Temperature dependence of thermal vibrations in cubic ZnS, a comparison of anharmonic models
International Nuclear Information System (INIS)
Accurate integrated intensities for the Bragg reflection of neutrons from a ZnS single crystal have been measured at temperatures between 285 and 1173 K. After correction for thermal diffuse scattering and extinction effects the data were interpreted with different models that allow anharmonic contributions to the temperature factor. Both the cumulant expansion and the one-particle potential (OPP) model with quasi-harmonic temperature dependence describe the data satisfactorily, although the Gruneisen parameter obtained in the OPP analysis differs greatly from the value calculated from known thermodynamic quantities. Predictions based on Matsubara's anharmonic formalism are not in accord with the behavior observed at the highest temperatures
Anharmonic Vibrational Dynamics of DNA Oligomers
Kühn, O; Krishnan, G M; Fidder, H; Heyne, K
2008-01-01
Combining two-color infared pump-probe spectroscopy and anharmonic force field calculations we characterize the anharmonic coupling patterns between fingerprint modes and the hydrogen-bonded symmetric NH$_2$ stretching vibration in adenine-thymine dA$_{20}$-dT$_{20}$ DNA oligomers. Specifically, it is shown that the anharmonic coupling between the NH$_2$ bending and the CO stretching vibration, both absorbing around 1665 cm-1, can be used to assign the NH$_2$ fundamental transition at 3215 cm-1 despite the broad background absorption of water.
A local anharmonic treatment of vibrations of methane
Arias Carrasco, José Miguel; Pérez Bernal, Francisco; A. Frank; Lemus Casillas, Renato; Bijker, R.
1996-01-01
The stretching and bending vibrations of methane are studied in a local anharmonic model of molecular vibrations. The use of symmetry-adapted operators reduces the eigenvalue problem to block diagonal form. For the 44 observed energies we obtain a fit with a standard deviation of 0.81 cm$^{-1}$ (and a r.m.s. deviation of 1.16 cm$^{-1}$).
Anharmonic collective excitation in a solvable model
International Nuclear Information System (INIS)
We apply the time-dependent variational principle, the nuclear field theory, and the boson expansion method to the Lipkin model to discuss anharmonicities of collective vibrational excitations. It is shown that all of these approaches lead to the same anharmonicity to leading order in the number of particles. Comparison with the exact solution of the Lipkin model shows that these theories reproduce quite well
Anharmonic Decay of Vibrational States in Amorphous Silicon
Fabian, Jaroslav; Allen, Philip B.
1996-01-01
Anharmonic decay rates are calculated for a realistic atomic model of amorphous silicon. The results show that the vibrational states decay on picosecond timescales and follow the two-mode density of states, similar to crystalline silicon, but somewhat faster. Surprisingly little change occurs for localized states. These results disagree with a recent experiment.
Vibrational spectroscopy via the Caldeira-Leggett model with anharmonic system potentials
Gottwald, Fabian; Kühn, Oliver
2016-01-01
The Caldeira-Leggett (CL) model, which describes a system bi-linearly coupled to a harmonic bath, has enjoyed popularity in condensed phase spectroscopy owing to its utmost simplicity. However, the applicability of the model to cases with anharmonic system potentials, as it is required for the description of realistic systems in solution, is questionable due to the presence of the invertibility problem [J. Phys. Chem. Lett., \\textbf{6}, 2722 (2015)] unless the system itself resembles the CL model form. This might well be the case at surfaces or in the solid regime, which we here confirm for a particular example of an iodine molecule in the atomic argon environment under high pressure. For this purpose we extend the recently proposed Fourier method for parameterizing linear generalized Langevin dynamics[J. Chem. Phys., \\textbf{142}, 244110 (2015)] to the non-linear case based on the CL model and perform an extensive error analysis. In order to judge on the applicability of this model in advance, we give handy ...
Anharmonicities in vibrational spectra of deformed nuclei discussed in a simple model
International Nuclear Information System (INIS)
Some microscopic treatments of the nuclear vibrational spectra are analyzed in terms of a model allowing an exact solution for a many-body nucleon system interacting via pairing plus quadrupole force. The multi-phonon approach -exact diagonalization in the restricted space of 1, 2, 3, .. collective phonons- appears satisfactory for the few lowest lying vibrational Ksup(π)=0+ states in deformed nuclei. The non conservation of the number of particles and coupling between collective and non collective states seem to be main sources of the discrepancies, that occur for the higher states. On the other hand, the lowest order contributions suggested by nuclear field theory lead to serious disagreement as compared with the exact solutions
Effective harmonic oscillator description of anharmonic molecular vibrations
Indian Academy of Sciences (India)
Tapta Kanchan Roy; M Durga Prasad
2009-09-01
The validity of an effective harmonic oscillator approximation for anharmonic molecular vibrations is tested and compared with vibrational self consistent field and vibrational configurational interaction results. The effective harmonic oscillator is constructed variationally, by taking the trial wave function as a harmonic oscillator eigenfunction with the centroid and width parameter as variational paraeters. It is found that the effective harmonic oscillator approximation provides a description of the anharmonic eigenstates very similar to the vibrational self consistent field results. Coriolis coupling is also included in these studies.
Analytic calculations of anharmonic infrared and Raman vibrational spectra.
Cornaton, Yann; Ringholm, Magnus; Louant, Orian; Ruud, Kenneth
2016-02-01
Using a recently developed recursive scheme for the calculation of high-order geometric derivatives of frequency-dependent molecular properties [Ringholm et al., J. Comp. Chem., 2014, 35, 622], we present the first analytic calculations of anharmonic infrared (IR) and Raman spectra including anharmonicity both in the vibrational frequencies and in the IR and Raman intensities. In the case of anharmonic corrections to the Raman intensities, this involves the calculation of fifth-order energy derivatives-that is, the third-order geometric derivatives of the frequency-dependent polarizability. The approach is applicable to both Hartree-Fock and Kohn-Sham density functional theory. Using generalized vibrational perturbation theory to second order, we have calculated the anharmonic infrared and Raman spectra of the non- and partially deuterated isotopomers of nitromethane, where the inclusion of anharmonic effects introduces combination and overtone bands that are observed in the experimental spectra. For the major features of the spectra, the inclusion of anharmonicities in the calculation of the vibrational frequencies is more important than anharmonic effects in the calculated infrared and Raman intensities. Using methanimine as a trial system, we demonstrate that the analytic approach avoids errors in the calculated spectra that may arise if numerical differentiation schemes are used. PMID:26784673
Solvent effect on the anharmonic vibrational frequencies in guanine-cytosine base pair
Bende, A.; Muntean, C. M.
2012-02-01
We present an ab initio study of the vibrational properties of cytosine and guanine in the Watson-Crick and Hoogsteen base pair configurations. The results are obtained by considering the DFT method together with the Polarizable Continuum Model (PCM) using PBE and B3PW91 exchange-correlation functionals and triple-ζ valence basis set. We investigate the importance of anharmonic corrections for the vibrational modes taking into account the solvent effect of the water environment. In particular, the unusual anharmonic effect of the H+ vibration in the case of the Hoogsteen base pair configuration is discussed.
Vibrational Spectra of the Azabenzenes Revisited: Anharmonic Force Fields
Boese, A D; Martin, Jan M.L.
2003-01-01
Anharmonic force fields and vibrational spectra of the azabenzene series (pyridine, pyridazine, pyrimidine, pyrazine, s-triazine, 1,2,3-triazine, 1,2,4-triazine and s-tetrazine) and benzene are obtained using density functional theory (DFT) with the B97-1 exchange-correlation functional and a triple-zeta plus double polarization (TZ2P) basis set. Overall, the fundamental frequencies computed by second-order rovibrational perturbation theory are in excellent agreement with experiment. The resolution of the presently calculated anharmonic spectra is such that they represent an extremely useful tool for the assignment and interpretation of the experimental spectra, especially where resonances are involved.
Probing anharmonic properties of nuclear surface vibration by heavy-ion fusion reactions
Takigawa, N.; Hagino, K.; Kuyucak, S
1997-01-01
Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O and ^{144}Sm by the $sd-$ and $sdf-$ interacting boson model, we show that heavy-ion fusion reactions are strongly affected by anharmonic properties of nuclear surface vibrations and nuclear shape, and thus provide a powerful method to study details of nuclear structure and dynamics.
Mckenzie, R. L.
1976-01-01
A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom is used to predict the variation of thermally averaged vibrational-translational rate coefficients with temperature and initial-state quantum number. Multiple oscillator states are included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model is also used as a basis for evaluating several less complete, but analytic, models. Two computationally simple analytic approximations are found that successfully reproduce the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations are identified, and the relative rates of multiple-quantum transitions from excited states are evaluated for several molecular types.
Mckenzie, R. L.
1975-01-01
A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom was used to predict the variation of thermally averaged vibration-translation rate coefficients with temperature and initial-state quantum number. Multiple oscillator states were included in a numerical solution for collinear encounters. The results are compared with CO-He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model was also used as a basis for evaluating several less complete but analytic models. Two computationally simple analytic approximations were found that successfully reproduced the numerical rate coefficients for a wide range of molecular properties and collision partners. Their limitations were also identified. The relative rates of multiple-quantum transitions from excited states were evaluated for several molecular types.
Anharmonic thermal vibrations of be metal found in the MEM nuclear density map
International Nuclear Information System (INIS)
A direct observation of the thermal vibrations of Be metal was performed by the Maximum Entropy Method (MEM) using neutron single crystal data. In the previous study, the existence of the small but significant cubic anharmonicity of Be has been found by the conventional least squares refinement of the observed structure factors [Larsen, Lehmann and Merisalo (1980) Acta Cryst. A36, 159-163]. In the present study, the same data were used for the MEM analysis which are comprised of 48 reflections up to sinθ/λ = 1.41A-1 in order to obtain the high resolution nuclear density of Be without using any thermal vibrational model. It was directly visible in the MEM map that not only the cubic terms but also quartic anharmonicities exist in the thermal vibrations of Be nuclei. In order to evaluate thermal parameters of Be including anharmonic terms quantitatively, the least squares refinement of the effective one-particle potential (OPP) parameters up to quartic term was carried out by using the MEM nuclear densities around atomic sites as the data set to be fitted. It was found that the present treatment has a great advantage to decide the most appropriate model of OPP by visually comparing the model with MEM density map. As a result of the least squares refinement, the anharmonic thermal parameters are obtained as α33 = -0.340(5)[eV/A3], α40 = 0, β20 = 9.89(1)[eV/A4] and γ00 = 0. No other anharmonic term was significant. (author)
On the benefits of localized modes in anharmonic vibrational calculations for small molecules.
Panek, Paweł T; Jacob, Christoph R
2016-04-28
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 challenges, we use localized-mode coordinates to construct potential energy surfaces and perform vibrational self-consistent field and L-VCI calculations [P. T. Panek and C. 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 higher-order contributions in hybrid potential energy surfaces, which reduced the computational effort for the construction of the anharmonic potential energy surface significantly. Moreover, we find that when using localized-mode coordinates, the convergence with respect to the VCI excitation space proceeds more smoothly and that the error at low orders is reduced significantly. This makes it possible to devise low-cost models for obtaining a first approximation of anharmonic corrections. This demonstrates that the use of localized-mode coordinates can be beneficial already in anharmonic vibrational calculations of small molecules and provides a possible avenue for enabling such accurate calculations also for larger molecules. PMID:27131535
On the benefits of localized modes in anharmonic vibrational calculations for small molecules
Panek, Paweł T.; Jacob, Christoph R.
2016-04-01
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 challenges, we use localized-mode coordinates to construct potential energy surfaces and perform vibrational self-consistent field and L-VCI calculations [P. T. Panek and C. 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 higher-order contributions in hybrid potential energy surfaces, which reduced the computational effort for the construction of the anharmonic potential energy surface significantly. Moreover, we find that when using localized-mode coordinates, the convergence with respect to the VCI excitation space proceeds more smoothly and that the error at low orders is reduced significantly. This makes it possible to devise low-cost models for obtaining a first approximation of anharmonic corrections. This demonstrates that the use of localized-mode coordinates can be beneficial already in anharmonic vibrational calculations of small molecules and provides a possible avenue for enabling such accurate calculations also for larger molecules.
Bloino, Julien; Biczysko, Malgorzata; Barone, Vincenzo
2015-12-10
The aim of this paper is 2-fold. First, we want to report the extension of our virtual multifrequency spectrometer (VMS) to anharmonic intensities for Raman optical activity (ROA) with the full inclusion of first- and second-order resonances for both frequencies and intensities in the framework of the generalized second-order vibrational perturbation theory (GVPT2) for all kinds of vibrational spectroscopies. Then, from a more general point of view, we want to present and validate the performance of VMS for the parallel analysis of different vibrational spectra for medium-sized molecules (IR, Raman, VCD, ROA) including both mechanical and electric/magnetic anharmonicity. For the well-known methyloxirane benchmark, careful selection of density functional, basis set, and resonance thresholds permitted us to reach qualitative and quantitative agreement between experimental and computed band positions and shapes. Next, the whole series of halogenated azetidinones is analyzed, showing that it is now possible to interpret different spectra in terms of mass, electronegativity, polarizability, and hindrance variation between closely related substituents, chiral spectroscopies being particular effective in this connection. PMID:26580121
Anharmonic contributions to the inversion vibration in 2-aminopyrimidine
McCarthy, W. J.; Lapinski, L.; Nowak, M. J.; Adamowicz, L.
1995-07-01
The out-of-plane vibrations of the amino group in 2-aminopyrimidine have large amplitudes, and cannot be properly described within the harmonic approximation. The normal mode analysis carried out at this level of approximation at the restricted Hartree-Fock level and at the second-order Møller-Plesset perturbation theory level failed to match the experimental transition frequency of ν≊200 cm-1 of the inversion vibration in this compound. In an effort to better understand this vibration motion, we went beyond the harmonic approximation. The inversion vibration was treated as being uncoupled from all other nuclear degrees of freedom. An internal coordinate (ω) was chosen whose displacement mimicked the out-of-plane distortion of the amino group during the inversion vibration. Electronic energy was calculated at the second-order Møller-Plesset perturbation theory level at selected values of ω to form a double-well curve describing a model potential within which the nuclei move during the vibration. This potential was incorporated into a one-dimensional Hamiltonian, and vibrational energy expectation values were variationally determined by utilizing the harmonic wavefunctions as the basis set. Two sets of calculations were performed: one in which the mirror plane of symmetry was preserved throughout the vibrational deformation limiting the internal coordinates to 17, and another in which the symmetry was unconstrained permitting description by 3N-6=30 internal coordinates. These calculations resulted in prediction of the v=0→v=1 transition energy of ν=130.1 cm-1 and ν=206.7 cm-1, respectively, reasonably matching the experimental value of ≊200 cm-1.
Anharmonic contributions to the inversion vibration in 2-aminopyrimidine
Energy Technology Data Exchange (ETDEWEB)
McCarthy, W.J. [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States); Lapinski, L.; Nowak, M.J. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw (Poland); Adamowicz, L. [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States)
1995-07-08
The out-of-plane vibrations of the amino group in 2-aminopyrimidine have large amplitudes, and cannot be properly described within the harmonic approximation. The normal mode analysis carried out at this level of approximation at the restricted Hartree--Fock level and at the second-order Moller--Plesset perturbation theory level failed to match the experimental transition frequency of {nu}{approx}200 cm{sup {minus}1} of the inversion vibration in this compound. In an effort to better understand this vibration motion, we went beyond the harmonic approximation. The inversion vibration was treated as being uncoupled from all other nuclear degrees of freedom. An internal coordinate ({omega}) was chosen whose displacement mimicked the out-of-plane distortion of the amino group during the inversion vibration. Electronic energy was calculated at the second-order Moller--Plesset perturbation theory level at selected values of {omega} to form a double-well curve describing a model potential within which the nuclei move during the vibration. This potential was incorporated into a one-dimensional Hamiltonian, and vibrational energy expectation values were variationally determined by utilizing the harmonic wavefunctions as the basis set. Two sets of calculations were performed: one in which the mirror plane of symmetry was preserved throughout the vibrational deformation limiting the internal coordinates to 17, and another in which the symmetry was unconstrained permitting description by 3{ital N}{minus}6=30 internal coordinates. These calculations resulted in prediction of the {ital v}=0{r_arrow}{ital v}=1 transition energy of {nu}=130.1 cm{sup {minus}1} and {nu}=206.7 cm{sup {minus}1}, respectively, reasonably matching the experimental value of {approx}200 cm{sup {minus}1}. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
A study of anharmonic al and nonlinear behaviours of vibrations of atomic nuclei
International Nuclear Information System (INIS)
Double Giant Resonances, vibrational states in which a Giant Resonance is excited on top of another Giant Resonance, have been in the last years the object of many theories and studies. Whereas the measured energies and widths of these states agree with a theoretical predictions, the measured excitation cross sections on the other hand are almost always larger than the calculated ones. The standard theoretical approaches are based both on a harmonic approximation for the collective motion on the nucleus and on its linear response to an external field. In this work the influence of anharmonicities and non-linearities in the external field on the excitation of Double Giant Resonances are studied. First, an oscillator model and an extension of the Lipkin-Meshkow-Glick model are used to study the effects of anharmonicities and non-linearities on the excitation probabilities. The results show that these terms can influence the excitation probability of the second excited state in a significant way. Secondly, these exactly soluble schematic models are used to study some of the approximations made in microscopic calculations based on boson expansion methods and also some aspects on the time-dependent mean field approach. Finally, a microscopic calculation of the Coulomb excitation cross sections of Double Giant Resonances is presented for several nuclei. It is found that, for 208 Pb, the inclusion of anharmonicities and non-linearities and the consideration of many states that play a role in the excitation process give a satisfactory agreement between calculated and observed cross sections. (author)
International Nuclear Information System (INIS)
The vibrational transition probability expressions for the forced Morse oscillator have been derived using the commutation relations of the anharmonic Boson operators. The formulation is based on the collinear collision model with the exponential repulsive potential in the framework of semiclassical collision dynamics. The sample calculation results for H2 + He collision system, where the anharmonicity is large, are in excellent agreement with those from an exact, numerical quantum mechanical study by Clark and Dickinson, using the reactance matrix. Our results,however, are markedly different from those of Ree, Kim, and Shin's in which they approximate the commutation operator Io as unity, the harmonic oscillator limit. We have concluded that the quantum number dependence in Io must be retained to get accurate vibrational transition probabilities for the Morse oscillator
Anharmonic calculation of vibration characteristics of the [F(HF)2]''- complex
International Nuclear Information System (INIS)
Anharmonic vibrations of the [F(HF)2]- complex were calculated using second-order perturbation theory and the variational method. The interaction of the stretching vibrations of HF molecular fragments and stretching vibrations of the hydrogen bond, as well as the interaction between stretching and bending vibrations of HF was considered in the second method. A more accurate description of the high-frequency of stretching vibration of the HF molecules for the [F(HF)2]- system with a strong hydrogen bond is obtained by the variational method. (authors)
Franck-Condon factors based on anharmonic vibrational wave functions of polyatomic molecules
Rodriguez-Garcia, Valerie; Yagi, Kiyoshi; Hirao, Kimihiko; Iwata, Suehiro; Hirata, So
2006-07-01
Franck-Condon (FC) integrals of polyatomic molecules are computed on the basis of vibrational self-consistent-field (VSCF) or configuration-interaction (VCI) calculations capable of including vibrational anharmonicity to any desired extent (within certain molecular size limits). The anharmonic vibrational wave functions of the initial and final states are expanded unambiguously by harmonic oscillator basis functions of normal coordinates of the respective electronic states. The anharmonic FC integrals are then obtained as linear combinations of harmonic counterparts, which can, in turn, be evaluated by established techniques taking account of the Duschinsky rotations, geometry displacements, and frequency changes. Alternatively, anharmonic wave functions of both states are expanded by basis functions of just one electronic state, permitting the FC integral to be evaluated directly by the Gauss-Hermite quadrature used in the VSCF and VCI steps [Bowman et al., Mol. Phys. 104, 33 (2006)]. These methods in conjunction with the VCI and coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] method have predicted the peak positions and intensities of the vibrational manifold in the X˜B12 photoelectron band of H2O with quantitative accuracy. It has revealed that two weakly visible peaks are the result of intensity borrowing from nearby states through anharmonic couplings, an effect explained qualitatively by VSCF and quantitatively by VCI, but not by the harmonic approximation. The X˜B22 photoelectron band of H2CO is less accurately reproduced by this method, likely because of the inability of CCSD(T)/cc-pVTZ to describe the potential energy surface of open-shell H2CO+ with the same high accuracy as in H2O+.
Adiabatic coherent control in the anharmonic ion trap: Proposal for the vibrational two-qubit system
International Nuclear Information System (INIS)
A method for encoding a multiqubit system into the quantized motional states of ion string in an anharmonic linear trap is proposed. Control over this system is achieved by applying oscillatory electric fields (rf) shaped optimally for desired state-to-state transitions. Anharmonicity of the vibrational spectrum of the system plays a key role in this approach to the control and quantum computation, since it allows resolving different state-to-state transitions and addressing them selectively. The anharmonic trap architecture proposed earlier [Phys. Rev. A 83, 022305 (2011)] is explored here and the optimal control theory is used to derive pulses for a set of universal quantum gates. An accurate choice of pulse parameters allows deriving gates that are both accurate and simple. A practical realization of this approach seems to be within the reach of today's technology.
Czech Academy of Sciences Publication Activity Database
Brauer, B.; Gerber, R. B.; Kabeláč, Martin; Hobza, Pavel; Bakker, J. M.; Abo-Riziq, A.; Vries de, M. S.
2005-01-01
Roč. 109, - (2005), s. 6974-6984. ISSN 1089-5639 Grant ostatní: NSF(US) CHE-0244341 Institutional research plan: CEZ:AV0Z40550506 Keywords : nucleic acids base s * vibrational spectrum * frequencies anharmonicity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.898, year: 2005
Anharmonic apical oxygen vibration in high-Tc superconductors
International Nuclear Information System (INIS)
Using time-independent perturbation theory, a theoretical calculation has been performed for the transition temperatures for various high-Tc oxide compounds. It has been assumed that, three electrons are responsible for the superconducting current. Whereas two of these electrons form an exotic bound pair, the third electron causes perturbation H' = βx3 + γx4 with respect to apical oxygen vibrations. From the calculations, the transition temperatures are found to be realistic and comparable with experimental results. (author)
Structure, Anharmonic Vibrational Frequencies, and Intensities of NNHNN(+).
Yu, Qi; Bowman, Joel M; Fortenberry, Ryan C; Mancini, John S; Lee, Timothy J; Crawford, T Daniel; Klemperer, William; Francisco, Joseph S
2015-11-25
A semiglobal potential energy surface (PES) and quartic force field (QFF) based on fitting high-level electronic structure energies are presented to describe the structures and spectroscopic properties of NNHNN(+). The equilibrium structure of NNHNN(+) is linear with the proton equidistant between the two nitrogen groups and thus of D(∞h) symmetry. Vibrational second-order perturbation theory (VPT2) calculations based on the QFF fails to describe the proton "rattle" motion, i.e., the antisymmetric proton stretch, due to the very flat nature of PES around the global minimum but performs properly for other modes with sharper potential wells. Vibrational self-consistent field/virtual state configuration interaction (VSCF/VCI) calculations using a version of MULTIMODE without angular momentum terms successfully describe this motion and predict the fundamental to be at 759 cm(-1). This is in good agreement with the value of 746 cm(-1) from a fixed-node diffusion Monte Carlo calculation and the experimental Ar-tagged result of 743 cm(-1). Other VSCF/VCI energies are in good agreement with other experimentally reported ones. Both double-harmonic intensity and rigorous MULTIMODE intensity calculations show the proton-transfer fundamental has strong intensity. PMID:26529262
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 ...
Jacobian elliptic wave solutions in an anharmonic molecular crystal model
International Nuclear Information System (INIS)
Explicit Jacobian elliptic wave solutions are found in the anharmonic molecular crystal model for both the continuum limit and discrete modes. This class of wave solutions include the famous pulse-like and kink-like solitary modes. We would also like to report on the existence of some highly discrete staggered solitary wave modes not found in the continuum limit. (author). 9 refs, 1 fig
Anharmonicities and coherent vibrational dynamics of phosphate ions in bulk H2O.
Costard, Rene; Tyborski, Tobias; Fingerhut, Benjamin P
2015-11-28
Phosphates feature prominently in the energetics of metabolism and are important solvation sites of DNA and phospholipids. Here we investigate the ion H2PO4(-) in aqueous solution combining 2D IR spectroscopy of phosphate stretching vibrations in the range from 900-1300 cm(-1) with ab initio calculations and hybrid quantum-classical molecular dynamics based simulations of the non-linear signal. While the line shapes of diagonal peaks reveal ultrafast frequency fluctuations on a sub-100 fs timescale caused by the fluctuating hydration shell, an analysis of the diagonal and cross-peak frequency positions allows for extracting inter-mode couplings and anharmonicities of 5-10 cm(-1). The excitation with spectrally broad pulses generates a coherent superposition of symmetric and asymmetric PO2(-) stretching modes resulting in the observation of a quantum beat in aqueous solution. We follow its time evolution through the time-dependent amplitude and the shape of the cross peaks. The results provide a complete characterization of the H2PO4(-) vibrational Hamiltonian including fluctuations induced by the native water environment. PMID:26488541
Alparone, Andrea
2014-01-01
Infrared, Raman and electronic absorption spectra, electronic and vibrational (hyper)polarizabilities, of barbituric, 2-thiobarbituric and 2-selenobarbituric acids were studied in gas using ab initio and density functional theory levels. The vibrational spectra were computed using harmonic and anharmonic methods. Anharmonic contributions improve the agreement between calculated and available experimental wavenumbers, especially in the highest-energy spectral region (wavenumbers >1700 cm-1). Vibrational and electronic transitions potentially useful to identify the investigated compounds were explored. The electronic and vibrational hyperpolarizabilities for the IDRI nonlinear optical (NLO) process at the λ value of 790 nm were computed. Supported by spectroscopic results, electronic and vibrational polarizabilities and second-order hyperpolarizabilities increase progressively in the order barbituric acid acid acid. The seleno-derivative is predicted to be ca. three/four times more hyperpolarizable than the barbituric acid. The Se → O or Se → S substitutions can be practical strategies to enhances the NLO properties of barbituric and thiobarbituric acid-based materials.
Thermoelectric materials: The anharmonicity blacksmith
Heremans, Joseph P.
2015-12-01
Anharmonicity is a property of lattice vibrations governing how they interact and how well they conduct heat. Experiments on tin selenide, the most efficient thermoelectric material known, now provide a link between anharmonicity and electronic orbitals.
Krasnoshchekov, Sergey V; Craig, Norman C; Boopalachandran, Praveenkumar; Laane, Jaan; Stepanov, Nikolay F
2015-10-29
A quantum-mechanical (hybrid MP2/cc-pVTZ and CCSD(T)/cc-pVTZ) full quartic potential energy surface (PES) in rectilinear normal coordinates and the second-order operator canonical Van Vleck perturbation theory (CVPT2) are employed to predict the anharmonic vibrational spectra of s-trans- and s-gauche-butadiene (BDE). These predictions are used to interpret their infrared and Raman scattering spectra. New high-temperature Raman spectra in the gas phase are presented in support of assignments for the gauche conformer. The CVPT2 solution is based on a PES and electro-optical properties (EOP; dipole moment and polarizability) expanded in Taylor series. Higher terms than those routinely available from Gaussian09 software were calculated by numerical differentiation of quadratic force fields and EOP using the MP2/cc-pVTZ model. The integer coefficients of the polyad quantum numbers were derived for both conformers of BDE. Replacement of harmonic frequencies by their counterparts from the CCSD(T)/cc-pVTZ model significantly improved the agreement with experimental data for s-trans-BDE (root-mean-square deviation ≈ 5.5 cm(-1)). The accuracy in predicting the rather well-studied spectrum of fundamentals of s-trans-BDE assures good predictions of the spectrum of s-gauche-BDE. A nearly complete assignment of fundamentals was obtained for the gauche conformer. Many nonfundamental transitions of the BDE conformers were interpreted as well. The predictions of multiple Fermi resonances in the complex CH-stretching region correlate well with experiment. It is shown that solving a vibrational anharmonic problem through a numerical-analytic implementation of CVPT2 is a straightforward and computationally advantageous approach for medium-size molecules in comparison with the standard second-order vibrational perturbation theory (VPT2) based on analytic expressions. PMID:26437183
Tasinato, Nicola; Regini, Giorgia; Stoppa, Paolo; Pietropolli Charmet, Andrea; Gambi, Alberto
2012-06-01
Difluoromethane (CH(2)F(2), HFC-32) is a molecule used in refrigerant mixtures as a replacement of the more environmentally hazardous, ozone depleting, chlorofluorocarbons. On the other hand, presenting strong vibration-rotation bands in the 9 μm atmospheric window, it is a greenhouse gas which contributes to global warming. In the present work, the vibrational and ro-vibrational properties of CH(2)F(2), providing basic data for its atmospheric modeling, are studied in detail by coupling medium resolution Fourier transform infrared spectroscopy to high-level electronic structure ab initio calculations. Experimentally a full quantum assignment and accurate integrated absorption cross sections are obtained up to 5000 cm(-1). Ab initio calculations are carried out by using CCSD(T) theory and large basis sets of either the correlation consistent or atomic natural orbital hierarchies. By using vibrational perturbation theory to second order a complete set of vibrational and ro-vibrational parameters is derived from the ab initio quartic anharmonic force fields, which well compares with the spectroscopic constants retrieved experimentally. An excellent agreement between theory and experiment is achieved for vibrational energy levels and integrated absorption cross sections: transition frequencies up to four quanta of vibrational excitation are reproduced with a root mean square deviation (RMSD) of 7 cm(-1) while intensities are predicted within few km mol(-1) from the experiment. Basis set performances and core correlation effects are discussed throughout the paper. Particular attention is focused in the understanding of the anharmonic couplings which rule the vibrational dynamics of the |ν(1)>, |2ν(8)>, |2ν(2)> three levels interacting system. The reliability of the potential energy and dipole moment surfaces in reproducing the vibrational eigenvalues and intensities as well as in modeling the vibrational and ro-vibrational mixings over the whole 400-5000 cm(-1
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Highlights: ► Halon 1113, potential ozone depleting gas, vibrational eigenstates and intensity. ► FT-IR experimental and theoretical study of chlorotrifluoroethene. ► Ab initio calculations at MP2 and CCSD(T) levels with cc-pVTZ and ANO basis sets. ► Equilibrium geometry and harmonic force field. ► Full CCSD(T) and hybrid anharmonic force fields. - Abstract: Halon 1113 (chlorotrifluoroethene), used in the synthesis of fluorocarbon-based polymers, has been recently detected in the atmosphere and it is a potential source of chlorine atoms. In this work, the vibrational properties of chlorotrifluoroethene are studied in the 125–5000 cm−1 region by coupling Fourier-transform infrared spectroscopy and high-level ab initio calculations. The vibrational analysis is performed over the whole spectral range and band intensities are obtained in the range 400–3100 cm−1. Ab initio calculations of the anharmonic force field are performed at the coupled cluster level of theory employing either cc-pVTZ or ANO basis sets. Vibration perturbation theory is applied to obtain spectroscopic parameters from the computed anharmonic force fields. The present results provide a solid interpretation of chlorotrifluoroethene vibrational spectrum, and they represent a significant reference for future studies on this molecule, being also the first published data on absorption cross sections and ab initio calculations.
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Inclusion of the anharmonicity normal mode vibrations [i.e., the third and fourth (and higher) derivatives of a molecular Born-Oppenheimer potential energy surface] is necessary in order to theoretically reproduce experimental fundamental vibrational frequencies of a molecule. Although ab initio determinations of harmonic vibrational frequencies may give errors of only a few percent by the inclusion of electron correlation within a large basis set for small molecules, in general, molecular fundamental vibrational frequencies are more often available from high resolution vibration-rotation spectra. Recently developed analytic third derivatives methods for self-consistent-field (SCF) wavefunctions have made it possible to examine with previously unavailable accuracy and computational efficiency the anharmonic force fields of small molecules
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The interesting features of phase transition in Rochelle Salt (RS) or C4H4O6NaK.4(H2O) i.e. the appearance of two Curie points Tsub(c1) (255 K) and Tsub(c2) (297 K) and large isotope effect on Tsub(c) are studied. On deuteration the lower Curie point shifts towards lower temperature and the upper Curie point towards the higher temperature, showing evidently the important role played by the hydrogen atoms in the ferroelectric behaviour of RS. A conclusion has finally been drawn from the present and previous investigations that both proton-lattice and phonon-phonon interactions play a vital role in the phase transition in hydrogen bonded ferroelectrics including KDP family and the present Rochelle Salt group. An estimation of the anharmonic contribution in the dynamic and static properties has also been found out for these crystals. (K.B.)
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Highlights: ► UV, IR and hole-burning spectra of a tri-peptide Z-PLG-NH2 were measured in a jet. ► The laser desorption technique was used to evaporate the peptide. ► The conformers were detected but the population is mainly distributed to a single conformation. ► MD simulations and DFT calculations reproduced the IR spectrum except for NH stretch. ► Anharmonic vibrational analysis VQDPT reproduced the splitting of the NH stretch. - Abstract: The electronic excitation and infrared (IR) spectra of a capped tri-peptide, Z-PLG-NH2 (Z = benzyloxycarbonyl, P = Pro, L = Leu, G = Gly), were measured in the gas phase by using the laser desorption supersonic jet technique. By measuring an ultraviolet–ultraviolet hole burning spectrum, it was found that Z-PLG-NH2 has the maximum three conformers in the gas phase, but that the population is mainly distributed to a single conformation. Molecular dynamics simulations and density functional theory calculations well-reproduced the observed IR spectrum, except for splitting of the NH stretching bands by a β-turn structure that corresponds to a global minimum structure. Anharmonic vibrational analysis by vibrational quasi-degenerate perturbation theory (VQDPT) successfully reproduced the anharmonic splitting, and confirmed the assignments
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Graphical abstract: The spectrum of the water dimer trapped in neon has been recorded and analysed up to 14,000 cm-1. Highlights: → Observation of the vibrational spectrum of the water dimer from the far infrared to the visible. → Assignment based on 18O/16O shift and on approximate values of anharmonicity coefficients. → Calculations in the framework of the second-order perturbation - resonance theory. - Abstract: The infrared spectrum of the water dimer trapped in solid neon has been recorded up to the visible by improving significantly the experimental technique used in a previous paper [Y. Bouteiller, J.P. Perchard, Chem. Phys. 305 (2004) 1]. A total of 22 intramolecular transitions of the proton donor (PD) and 23 of the proton acceptor (PA) are now identified and assigned on the basis of 16O/18O isotopic shifts and of realistic anharmonicity corrections. From an ab initio determination of the potential energy a perturbation-resonance treatment has been carried out for each polyad Pn, n = 2-8. Finally combinations of intra + intermolecular transitions were identified and assigned on the basis of calculated anharmonicity coefficients.
Reynolds, Anthony
Proton-coupled electron transfer model systems (PCET) are examined using polarization selective femtosecond infrared pump-probe spectroscopy to determine how the structural modes are coupled to the OH/OD stretching vibrational mode by monitoring low frequency oscillations in the OH/OD vibrational mode using pump-probe techniques. For all of the systems discussed in this dissertation, low frequency modes are anharmonically coupled to the OH/OD stretching vibration. The OH/OD stretching vibration discussed in this dissertation have complex and broad lineshapes in the infrared region (IR) that are difficult to decipher. A broadband IR (BBIR) source, when used as part of a third order nonlinear infrared pump-probe spectroscopy, gains access into the electronic ground state potential energy surface. This information reveals the molecular dynamics that give rise to the complex structure in an IR spectra. The BBIR used for these experiments is generated by focusing 800 nm/400 nm pulses into compressed air and is tunable from 2 -- 5 microns with a FWHM greater than 1200 wavenumbers. The BBIR is a crucial mid-IR source in subsequent chapters for examining the broad lineshapes of the OH/OD stretching mode, which often exceeds 200 wavenumbers. The coupling of low frequency structural modulations to hydrogen bonding dynamics in PCET systems is explored by using the OH/OD stretching vibration in CCl4 or CHCl3. Third order nonlinear ultrafast infrared pump-probe spectroscopy is used to gather information on the high frequency OH/OD stretching vibrational modes in the ground state such as vibrational relaxation time and anharmonic vibrational coupling to low frequency structural modulations. At least one anharmonically coupled low frequency mode between 120 and 250 wavenumbers has been observed in all systems. To better understand and visualize how the low frequency mode may contribute to the PCET chemistry, we calculated the fundamental frequencies and third order coupling
Anharmonic vibrations around a triaxial nuclear deformation “frozen” to γ = 30°
Energy Technology Data Exchange (ETDEWEB)
Buganu, Petrica, E-mail: buganu@theory.nipne.ro; Budaca, Radu [Department of Theoretical Physics, National Institute of Physics and Nuclear Engineering, Str. Reactorului 30, RO-077125, POB-MG6, Bucharest-Magurele (Romania)
2015-12-07
The Davydov-Chaban Hamiltonian with a sextic oscillator potential for the variable β and γ fixed to 30° is exactly solved for the ground and β bands and approximately for the γ band. The model is called Z(4)-Sextic in connection with the already established Z(4) solution. The energy spectra, normalized to the energy of the first excited state, and several B(E2) transition probabilities, normalized to the B(E2) transition from the first excited state to the ground state, depend on a single parameter α. By varying α within a sufficiently large interval, a shape phase transition from an approximately spherical shape to a deformed one is evidenced.
Low-temperature vibrational anharmonicity of 151Eu in EuBa2Cu3O7-δ
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The angular averaged mean-square displacement of 151Eu in EuBa2Cu3O7-δ was measured as a function of temperature by Moessbauer spectroscopy using the absorption area method. Large low-temperature anharmonicity was found; i.e. the adiabatic potential experienced by Eu3+ ions presents a 'wine-bottle bottom' shape with a flat region about 0.1 AA wide. Comparisons with other experimental results are made. (author)
Alcohol dimers - how much diagonal OH anharmonicity?
Kollipost, Franz; Papendorf, Kim; Lee, Yu-Fang; Lee, Yuan-Pern; Suhm, Martin A
2014-01-01
The OH bond of methanol, ethanol and t-butyl alcohol becomes more anharmonic upon hydrogen bonding and the infrared intensity ratio between the overtone and the fundamental transition of the bridging OH stretching mode decreases drastically. FTIR spectroscopy of supersonic slit jet expansions allows to quantify these effects for isolated alcohol dimers, enabling a direct comparison to anharmonic vibrational predictions. The diagonal anharmonicity increase amounts to 15-18%, growing with incre...
Kesharwani, Manoj K; Brauer, Brina; Martin, Jan M L
2015-03-01
We have obtained uniform frequency scaling factors λ(harm) (for harmonic frequencies), λ(fund) (for fundamentals), and λ(ZPVE) (for zero-point vibrational energies (ZPVEs)) for the Weigend-Ahlrichs and other selected basis sets for MP2, SCS-MP2, and a variety of DFT functionals including double hybrids. For selected levels of theory, we have also obtained scaling factors for true anharmonic fundamentals and ZPVEs obtained from quartic force fields. For harmonic frequencies, the double hybrids B2PLYP, B2GP-PLYP, and DSD-PBEP86 clearly yield the best performance at RMSD = 10-12 cm(-1) for def2-TZVP and larger basis sets, compared to 5 cm(-1) at the CCSD(T) basis set limit. For ZPVEs, again, the double hybrids are the best performers, reaching root-mean-square deviations (RMSDs) as low as 0.05 kcal/mol, but even mainstream functionals like B3LYP can get down to 0.10 kcal/mol. Explicitly anharmonic ZPVEs only are marginally more accurate. For fundamentals, however, simple uniform scaling is clearly inadequate. PMID:25296165
Exact solutions for anharmonic oscillators
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Rigorous solutions for the one-dimensional quantum mechanical doubly anharmonic oscillator in the form of definite integrals, already presented (Flessas. Phys. Lett. 81 A: 17 (1981)), are here generalised to anharmonic interactions and their interest for models of the charmonium system considered. (U.K.)
Generation of discrete superpositions of coherent states in the anharmonic oscillator model
Miranowicz, A; Kielich, S; 10.1088/0954-8998/2/3/006
2011-01-01
The problem of generating discrete superpositions of coherent states in the process of light propagation through a nonlinear Kerr medium, which is modelled by the anharmonic oscillator, is discussed. It is shown that under an appropriate choice of the length (time) of the medium the superpositions with both even and odd numbers of coherent states can appear. Analytical formulae for such superpositions with a few components are given explicitly. General rules governing the process of generating discrete superpositions of coherent states are also given. The maximum number of well distinguished states that can be obtained for a given number of initial photons is estimated. The quasiprobability distribution $Q(\\alpha,\\alpha^*,t)$ representing the superposition states is illustrated graphically, showing regular structures when the component states are well separated.
The vibration states of the Skyrme model
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In the paper an algebraic method for the construction of the collective Hamiltonian of the Skyrme model is treated. The Skyrme model has some phenomenological success in describing the static properties of nucleon and their interactions. The vibration spectra in the framework of the subgroup SU(5) have been discussed. Exploiting the related symmetry group it is possible to obtain the simple analytic expressions for the eigenvalues of boson Hamiltonian and for intraband transition matrix elements as well as for side feeding from one band to the other. Back-bending occurs naturally as the crossing of two bands and it can be predicted from the relative spacing of the low excited states. The algebraic properties of collective variables lead to a new quantum number N which implies in the boson representation the maximum number of phonons contained in vibrational states. Because the boson-boson interaction in SU(5) invariant Hamiltonian splits the degeneracy of the multiplets, this limits describes an anharmonic vibrator. It should be noted, we describe finite dimensional system in contrast with the geometrical description in which N→∞. It is worth noting that the knowledge of the invariance properties of Hamiltonian provides directly a solution to the eigenvalue problem. The transformation into intrinsic frame of reference has been performed explicitly. Thus, the formulae for the potential energy, the quadrupole moments are obtained as well as the spectroscopic factors for 0+ state excitation in the two nucleon transfer reactions. The proposed collective Hamiltonian is applied to the transformational nuclei Sm, Gd and Dy. The agreement between the experimental data and the theoretical description is good
Model Indepedent Vibration Control
Yuan, Jing
2010-01-01
A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is
Energy localization in an anharmonic twist-opening model of DNA dynamics.
Tabi, Conrad Bertrand
2010-10-20
Energy localization is investigated in the framework of the anharmonic twist-opening model proposed by Cocco and Monasson. This model includes the coupling between opening and twist that result from the helicoidal geometry of B-DNA. I first reduce the corresponding two-component model to its amplitude equations, which have the form of coupled discrete nonlinear Schrödinger (DNLS) equations, and I perform the linear stability analysis of the plane waves, solutions of the coupled DNLS equations. It is shown that the stability criterion deeply depends on the stiffness of the molecule. Numerical simulations are carried out in order to verify analytical predictions. It results that increasing the value of the molecule stiffness makes the energy patterns long-lived and highly localized. This can be used to explain the way enzymes concentrate energy on specific sequences of DNA for the base-pairs to be broken. The role of those enzymes could therefore be to increase the stiffness of closed regions of DNA at the boundaries of an open state. PMID:21386590
Anharmonic modeling of the conformation-specific IR spectra of ethyl, n-propyl, and n-butylbenzene
Tabor, Daniel P.; Hewett, Daniel M.; Bocklitz, Sebastian; Korn, Joseph A.; Tomaine, Anthony J.; Ghosh, Arun K.; Zwier, Timothy S.; Sibert, Edwin L.
2016-06-01
Conformation-specific UV-IR double resonance spectra are presented for ethyl, n-propyl, and n-butylbenzene. With the aid of a local mode Hamiltonian that includes the effects of stretch-scissor Fermi resonance, the spectra can be accurately modeled for specific conformers. These molecules allow for further development of a first principles method for calculating alkyl stretch spectra. Across all chain lengths, certain dihedral patterns impart particular spectral motifs at the quadratic level. However, the anharmonic contributions are consistent from molecule to molecule and conformer to conformer. This transferability of anharmonicities allows for the Hamiltonian to be constructed from only a harmonic frequency calculation, reducing the cost of the model. The phenyl ring alters the frequencies of the CH2 stretches by about 15 cm-1 compared to their n-alkane counterparts in trans configurations. Conformational changes in the chain can lead to shifts in frequency of up to 30 cm-1.
Are giant resonances harmonic vibrations?
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Giant resonances are understood as the first quantum of collective vibrations. The non-linear response of a quantum anharmonic oscillator is investigated as a model for the excitation of giant resonances in heavy ion collisions. It is shown that the introduction of small anharmonicities and non-linearities can double the predicted cross section for the excitation of the two-phonon states. (R.P.)
Langevin model of the temperature and hydration dependence of protein vibrational dynamics.
Moritsugu, Kei; Smith, Jeremy C
2005-06-23
The modification of internal vibrational modes in a protein due to intraprotein anharmonicity and solvation effects is determined by performing molecular dynamics (MD) simulations of myoglobin, analyzing them using a Langevin model of the vibrational dynamics and comparing the Langevin results to a harmonic, normal mode model of the protein in vacuum. The diagonal and off-diagonal Langevin friction matrix elements, which model the roughness of the vibrational potential energy surfaces, are determined together with the vibrational potentials of mean force from the MD trajectories at 120 K and 300 K in vacuum and in solution. The frictional properties are found to be describable using simple phenomenological functions of the mode frequency, the accessible surface area, and the intraprotein interaction (the displacement vector overlap of any given mode with the other modes in the protein). The frictional damping of a vibrational mode in vacuum is found to be directly proportional to the intraprotein interaction of the mode, whereas in solution, the friction is proportional to the accessible surface area of the mode. In vacuum, the MD frequencies are lower than those of the normal modes, indicating intramolecular anharmonic broadening of the associated potential energy surfaces. Solvation has the opposite effect, increasing the large-amplitude vibrational frequencies relative to in vacuum and thus vibrationally confining the protein atoms. Frictional damping of the low-frequency modes is highly frequency dependent. In contrast to the damping effect of the solvent, the vibrational frequency increase due to solvation is relatively temperature independent, indicating that it is primarily a structural effect. The MD-derived vibrational dynamic structure factor and density of states are well reproduced by a model in which the Langevin friction and potential of mean force parameters are applied to the harmonic normal modes. PMID:16852503
Spontaneous and stimulated Raman studies of vibrational dephasing in condensed phases
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Vibrational dephasing in condensed phases is studied from both a theoretical and experimental standpoint. A theory is presented which describes the dynamics of motional or exchange processes in weakly perturbed systems. This general formalism, which has been previously used to describe motional narrowing in magnetic resonance, is applied to vibrational spectroscopy. The model treats the case of a high frequency vibration anharmonically coupled to a low-frequency vibration. Intermolecular exchange of low frequency vibrational quanta results in a temperature dependent broadening and frequency shift of the high frequency vibration. Analysis of experimental data by this model yields both the exchange rates and the anharmonic couplings
Vibration absorber modeling for handheld machine tool
Abdullah, Mohd Azman; Mustafa, Mohd Muhyiddin; Jamil, Jazli Firdaus; Salim, Mohd Azli; Ramli, Faiz Redza
2015-05-01
Handheld machine tools produce continuous vibration to the users during operation. This vibration causes harmful effects to the health of users for repeated operations in a long period of time. In this paper, a dynamic vibration absorber (DVA) is designed and modeled to reduce the vibration generated by the handheld machine tool. Several designs and models of vibration absorbers with various stiffness properties are simulated, tested and optimized in order to diminish the vibration. Ordinary differential equation is used to derive and formulate the vibration phenomena in the machine tool with and without the DVA. The final transfer function of the DVA is later analyzed using commercial available mathematical software. The DVA with optimum properties of mass and stiffness is developed and applied on the actual handheld machine tool. The performance of the DVA is experimentally tested and validated by the final result of vibration reduction.
Anharmonicity and hydrogen bonding in electrooptic sucrose crystal
Szostak, M. M.; Giermańska, J.
1990-03-01
The polarized absorption spectra of the sucrose crystal in the 5300 - 7300 cm -1 region have been measured. The assignments of all the eight OH stretching overtones are proposed and their mechanical anharmonicities are estimated. The discrepancies from the oriented gas model (OGM) in the observed relative band intensities, especially of the -CH vibrations, are assumed to be connected with vibronic couplings enhanced by the helical arrangement of molecules joined by hydrogen bondings. It seems that this kind of interactions might be important for the second harmonic generation (SHG) by the sucrose crystal.
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Quantum and anharmonic effects are investigated in H2-Li+-benzene, a model for hydrogen adsorption in metal-organic frameworks and carbon-based materials. Three- and 8-dimensional quantum diffusion Monte Carlo (QDMC) and rigid-body diffusion Monte Carlo (RBDMC) simulations are performed on potential energy surfaces interpolated from electronic structure calculations at the M05-2X/6-31+G(d,p) and M05-2X/6-311+G(2df,p) levels of theory using a three-dimensional spline or a modified Shepard interpolation. These calculations investigate the intermolecular interactions in this system, with three- and 8-dimensional 0 K H2 binding enthalpy estimates, ΔHbind (0 K), being 16.5 kJ mol−1 and 12.4 kJ mol−1, respectively: 0.1 and 0.6 kJ mol−1 higher than harmonic values. Zero-point energy effects are 35% of the value of ΔHbind (0 K) at M05-2X/6-311+G(2df,p) and cannot be neglected; uncorrected electronic binding energies overestimate ΔHbind (0 K) by at least 6 kJ mol−1. Harmonic intermolecular binding enthalpies can be corrected by treating the H2 “helicopter” and “ferris wheel” rotations as free and hindered rotations, respectively. These simple corrections yield results within 2% of the 8-dimensional anharmonic calculations. Nuclear ground state probability density histograms obtained from the QDMC and RBDMC simulations indicate the H2 molecule is delocalized above the Li+-benzene system at 0 K
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We investigate a chain of oscillators with anharmonic on-site potentials, with long range interparticle interactions, and coupled both to external and internal stochastic thermal reservoirs of Ornstein–Uhlenbeck type. We develop an integral representation, a' la Feynman–Kac, for the correlations and the heat current. We assume the approximation of discrete times in the integral formalism (together with a simplification in a subdominant part of the harmonic interaction) and develop a suitable polymer expansion for the model. In the regime of strong anharmonicity, strong harmonic pinning, and for the interparticle interaction with integrable polynomial decay, we prove the convergence of the polymer expansion uniformly in volume (number of sites and time). We also show that the two-point correlation decays in space such as the interparticle interaction. The existence of a convergent polymer expansion is of practical interest: it establishes a rigorous support for a perturbative analysis of the heat flow problem and for the computation of the thermal conductivity in related anharmonic crystals, including those with inhomogeneous potentials and long range interparticle interactions. To show the usefulness and trustworthiness of our approach, we compute the thermal conductivity of a specific anharmonic chain, and make a comparison with related numerical results presented in the literature. (paper)
Czech Academy of Sciences Publication Activity Database
Kabeláč, Martin; Hobza, Pavel; Špirko, Vladimír
2009-01-01
Roč. 11, č. 20 (2009), s. 3921-3926. ISSN 1463-9076 R&D Projects: GA AV ČR IAA400550511; GA AV ČR IAA400550808; GA ČR GA203/06/0420; GA MŠk LC512 Grant ostatní: GA ČR(CZ) GA203/06/0738 Institutional research plan: CEZ:AV0Z40550506 Keywords : tryptophan * anharmonicity * harmonic frequencies * ab initio Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.116, year: 2009
International Nuclear Information System (INIS)
In this work the mass spectra for some of the baryon resonances of the particle data group with three and four star status are obtained, and a unified description of the ground states and excitation spectra of baryons are provided in the framework of a non-relativistic potential model. For this goal we have analytically solved the radial Schroedinger equation for three identical interacting particles with the anharmonic potential by using the Ansatz method and then we have calculated the baryon resonances spectrum by using the Goursey Radicati mass formula (GR) and with generalized Goursey Radicati mass formula (GGR). The results of our model show that the calculated masses of baryon resonances by using the generalized Goursey Radicati mass formula are found to be in good agreement with the tabulations of the Particle Data Group. The overall good description of the spectrum which we obtain shows that our model can also be used to give a fair description of the energies of the excited multiples up to 3 GeV mass and negative-parity resonance. Moreover, we have shown that our model reproduces the position of the Roper resonance of the nucleon. (authors)
Zaleśny, Robert; Góra, Robert W; Luis, Josep M; Bartkowiak, Wojciech
2015-09-14
The influence of the spatial confinement on the electronic and vibrational contributions to longitudinal electric-dipole properties of model linear molecules including HCN, HCCH and CO2 is discussed. The effect of confinement is represented by two-dimensional harmonic oscillator potential of cylindrical symmetry, which mimics the key features of various types of trapping environments like, for instance, nanotubes or quantum well wires. Our results indicate that in general both (electronic and vibrational) contributions to (hyper)polarizabilities diminish upon spatial confinement. However, since the electronic term is particularly affected, the relative importance of vibrational contributions is larger for confined species. This effect increases also with the degree of anharmonicity of vibrational motion. PMID:26247540
International Nuclear Information System (INIS)
An overview is given on anharmonic lattice vibrations originating from structural instabilities. The transverse vibrations of the chain oxygens in YBa2Cu3O7 are found to be only moderately anharmonic. Measurements of the phonon linewidths in the Cu-O bond stretching vibrations strongly support recent calculations of the electron-phonon coupling. Results are presented on superconductivity-induced frequency shifts at short wavelengths. 20 refs., 15 figs
Anharmonic force fields and thermodynamic functions using density functional theory
Boese, A. Daniel; Klopper, Wim; Martin, Jan M. L.
2004-01-01
The very good performance of modern density functional theory for molecular geometries and harmonic vibrational frequencies has been well established. We investigate the performance of density functional theory (DFT) for quartic force fields, vibrational anharmonicity and rotation-vibration coupling constants, and thermodynamic functions beyond the RRHO (rigid rotor-harmonic oscillator) approximation of a number of small polyatomic molecules. Convergence in terms of basis set, integration gri...
Vibrational Spectroscopy of Methyl benzoate
Maiti, Kiran Sankar
2014-01-01
Methyl benzoate (MB) is studied as a model compound for the development of new IR pulse schemes with possible applicability to biomolecules. Anharmonic vibrational modes of MB are calculated on different level (MP2, SCS, CCSD(T) with varying basis sets) ab-initio PESs using the vibrational self-consistent field (VSCF) method and its correlation corrected extensions. Dual level schemes, combining different quantum chemical methods for diagonal and coupling potentials, are systematically studied and applied successfully to reduce the computational cost. Isotopic substitution of {\\beta}-hydrogen by deuterium is studied to obtain a better understanding of the molecular vibrational coupling topology.
Anomalous dynamical scaling in anharmonic chains and plasma models with multi-particle collisions
Di Cintio, Pierfrancesco; Bufferand, Hugo; Ciraolo, Guido; Lepri, Stefano; Straka, Mika J
2015-01-01
We study the anomalous dynamical scaling of equilibrium correlations in one dimensional systems. Two different models are compared: the Fermi-Pasta-Ulam chain with cubic and quartic nonlinearity and a gas of point particles interacting stochastically through the Multi-Particle Collision dynamics. For both models -that admit three conservation laws- by means of detailed numerical simulations we verify the predictions of Nonlinear Fluctuating Hydrodynamics for the structure factors of density and energy fluctuations at equilibrium. Despite of this, violations of the expected scaling in the currents correlation are found in some regimes, hindering the observation of the asymptotic scaling predicted by the theory. In the case of the gas model this crossover is clearly demonstrated upon changing the coupling constant.
Anomalous dynamical scaling in anharmonic chains and plasma models with multiparticle collisions
Di Cintio, Pierfrancesco; Livi, Roberto; Bufferand, Hugo; Ciraolo, Guido; Lepri, Stefano; Straka, Mika J.
2015-12-01
We study the anomalous dynamical scaling of equilibrium correlations in one-dimensional systems. Two different models are compared: the Fermi-Pasta-Ulam chain with cubic and quartic nonlinearity and a gas of point particles interacting stochastically through multiparticle collision dynamics. For both models—that admit three conservation laws—by means of detailed numerical simulations we verify the predictions of nonlinear fluctuating hydrodynamics for the structure factors of density and energy fluctuations at equilibrium. Despite this, violations of the expected scaling in the currents correlation are found in some regimes, hindering the observation of the asymptotic scaling predicted by the theory. In the case of the gas model this crossover is clearly demonstrated upon changing the coupling constant.
The origin of phonon anharmonicity in MgB{sub 2} and related compounds
Energy Technology Data Exchange (ETDEWEB)
Boeri, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Bachelet, G B [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Cappelluti, E [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy); Pietronero, L [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita di Roma ' La Sapienza' , Piazzale A. Moro 2, 00185 Rome (Italy)
2003-02-01
The recent discovery of a superconducting transition at 39 K in MgB{sub 2} - made of alternating Mg and graphene-like B planes - has raised great interest, for both its technological and theoretical implications. It was clear since the very beginning that the properties of this material are related to an anomalous coupling between the charge carriers in the {sigma} bands - due to in-plane bonds between Boron atoms - and the phonon mode (E{sub 2g}) which involves in-plane vibrations of the B ions. Theoretical studies have thus been focused on the search for possible anomalies in the e-ph coupling: one of the first results was the discovery that the E{sub 2g} phonon is highly anharmonic, but the connection between anharmonicity and T{sub c} in this material is still a controversial point. We first present a detailed first-principles study of the E{sub 2g} phonon anharmonicity in MgB{sub 2} and analogous compounds which are not superconducting, AlB{sub 2} and graphite, and in a hypothetical hole-doped graphite (C{sup 2+}{sub 2}); we then introduce an analytical model which allows us to relate the onset of anharmonicity with the small Fermi energy of the carriers in {sigma} bands. Our study suggests a possible relation between anharmonicity and non-adiabaticity; non-adiabatic effects, which can lead to a sensible increase of T{sub c} with respect to values predicted by conventional theory, become in fact relevant when phonon frequencies are comparable to electronic energy scales.
E x circle ε Jahn-Teller anharmonic coupling for an octahedral system
International Nuclear Information System (INIS)
The coupling between doubly degenerate electronic states and doubly degenerate vibrations is analyzed for an octahedral system on the basis of the introduction of an anharmonic Morse potential for the vibronic part. The vibrations are described by anharmonic coherent states and their linear coupling with the electronic states is considered. The matrix elements of the vibronic interaction are built and the energy levels corresponding to the interaction Hamiltonian are derived. (authors)
Modelling chaotic vibrations using NASTRAN
Sheerer, T. J.
1993-09-01
Due to the unavailability and, later, prohibitive cost of the computational power required, many phenomena in nonlinear dynamic systems have in the past been addressed in terms of linear systems. Linear systems respond to periodic inputs with periodic outputs, and may be characterized in the time domain or in the frequency domain as convenient. Reduction to the frequency domain is frequently desireable to reduce the amount of computation required for solution. Nonlinear systems are only soluble in the time domain, and may exhibit a time history which is extremely sensitive to initial conditions. Such systems are termed chaotic. Dynamic buckling, aeroelasticity, fatigue analysis, control systems and electromechanical actuators are among the areas where chaotic vibrations have been observed. Direct transient analysis over a long time period presents a ready means of simulating the behavior of self-excited or externally excited nonlinear systems for a range of experimental parameters, either to characterize chaotic behavior for development of load spectra, or to define its envelope and preclude its occurrence.
Stoppa, Paolo; Tasinato, Nicola; Baldacci, Agostino; Pietropolli Charmet, Andrea; Giorgianni, Santi; Tamassia, Filippo; Cané, Elisabetta; Villa, Mattia
2016-05-01
The FTIR spectra of CH2F2 have been investigated in a region of atmospheric interest (1000-1300 cm-1) where four fundamentals ν3, ν5, ν7 and ν9 occur. These vibrations perturb each other by different Coriolis interactions and the forbidden ν5 borrows intensity from the neighboring levels. Furthermore, the v4=2 state has been found to interact with the v3=1 and v9=1 states by anharmonic and c-type Coriolis resonances, respectively. The spectral analysis resulted in the assignment of about 7500 rovibrational transitions which have been simultaneously fitted, together with microwave data available in literature (Hirota E. J Mol Spectrosc 1978; 69: 409-420) [15] using the Watson's A-reduction Hamiltonian in the Ir representation and the relevant perturbation operators. The model employed includes eight types of resonances within the pentad ν3/ν5/ν7/ν9/2ν4. A set of spectroscopic constants for the four fundamentals as well as parameters for the v4=2 state and eighteen coupling terms have been determined. The simulations performed in different spectral regions well reproduce the experimental data.
Morgan, Sarah E; Chin, Alex W
2016-01-01
Collective protein modes are expected to be important for facilitating energy transfer in the Fenna-Matthews-Olson (FMO) complex, however to date little work has focussed on the microscopic details of these vibrations. The nonlinear network model (NNM) provides a computationally inexpensive approach to studying vibrational modes at the microscopic level, whilst incorporating anharmonicity in the inter-residue interactions which can influence protein dynamics. We apply the NNM to the FMO complex and find evidence for the existence of nonlinear discrete breather modes. These modes tend to transfer energy to the highly connected core pigments, potentially opening up alternative excitation energy transfer routes. Incorporating localised modes based on these discrete breathers in the optical spectra calculations for FMO using ab initio site energies and excitonic couplings can substantially improve their agreement with experimental results.
Information criteria and selection of vibration models.
Ruzek, Michal; Guyader, Jean-Louis; Pézerat, Charles
2014-12-01
This paper presents a method of determining an appropriate equation of motion of two-dimensional plane structures like membranes and plates from vibration response measurements. The local steady-state vibration field is used as input for the inverse problem that approximately determines the dispersion curve of the structure. This dispersion curve is then statistically treated with Akaike information criterion (AIC), which compares the experimentally measured curve to several candidate models (equations of motion). The model with the lowest AIC value is then chosen, and the utility of other models can also be assessed. This method is applied to three experimental case studies: A red cedar wood plate for musical instruments, a thick paper subjected to unknown membrane tension, and a thick composite sandwich panel. These three cases give three different situations of a model selection. PMID:25480053
International Nuclear Information System (INIS)
Graphical abstract: Schematic diagram of a bent triatomic molecule, depicting the atom numbering, and molecular axis system. An algebraic approach to perform global rovibrational analysis is presented. Highlights: ► Novel approach for a global rovibrational analysis of polyatomic molecules spectra. ► One-dimensional vibron model limit combined with rotational degrees of freedom. ► Phase space Hamiltonian written in terms of anharmonic ladder operators. ► Algebraic calculations performed with a symmetry-adapted rovibrational basis. ► Description of the rovibrational spectrum of H2Se in the ground electronic state. - Abstract: An algebraic approach to perform global rovibrational analysis of molecular spectra is presented. The approach combines the one-dimensional limit of the vibron model with rotational degrees of freedom. The model is based on the expression of the phase space Hamiltonian in terms of anharmonic ladder operators and the use of a symmetry-adapted basis set given by the linear combination of products of local vibrational and rotational wavefunctions. As an example we model the rovibrational spectra of a bent triatomic molecule, providing a global analysis for vibrational bands up to polyad 12 and Jmax = 5 of Hydrogen Selenide (H2Se). Satisfactory fits of vibrational and rovibrational energies are obtained. A prediction of 2579 rovibrational energies up to J ⩽ 5 and polyad 12 for the 140 lowest vibrational bands is also obtained. A possible extension of the model to reach spectroscopic quality results in larger molecular systems is also given.
Monitoring Vibration of A Model of Rotating Machine
Directory of Open Access Journals (Sweden)
Arko Djajadi
2012-03-01
Full Text Available Mechanical movement or motion of a rotating machine normally causes additional vibration. A vibration sensing device must be added to constantly monitor vibration level of the system having a rotating machine, since the vibration frequency and amplitude cannot be measured quantitatively by only sight or touch. If the vibration signals from the machine have a lot of noise, there are possibilities that the rotating machine has defects that can lead to failure. In this experimental research project, a vibration structure is constructed in a scaled model to simulate vibration and to monitor system performance in term of vibration level in case of rotation with balanced and unbalanced condition. In this scaled model, the output signal of the vibration sensor is processed in a microcontroller and then transferred to a computer via a serial communication medium, and plotted on the screen with data plotter software developed using C language. The signal waveform of the vibration is displayed to allow further analysis of the vibration. Vibration level monitor can be set in the microcontroller to allow shutdown of the rotating machine in case of excessive vibration to protect the rotating machine from further damage. Experiment results show the agreement with theory that unbalance condition on a rotating machine can lead to larger vibration amplitude compared to balance condition. Adding and reducing the mass for balancing can be performed to obtain lower vibration level.
Global modeling of vibration-rotation spectra of the acetylene molecule
Lyulin, O. M.; Perevalov, V. I.
2016-07-01
The global modeling of both line positions and intensities of the acetylene molecule in the 50-9900 cm-1 region has been performed using the effective operators approach. The parameters of the polyad model of effective Hamiltonian have been fitted to the line positions collected from the literature. The used polyad model of effective Hamiltonian takes into account the centrifugal distortion, rotational and vibrational ℓ-doubling terms and both anharmonic and Coriolis resonance interaction operators arising due to the approximate relations between the harmonic frequencies: ω1≈ω3≈5ω4≈5ω5 and ω2≈3ω4≈3ω5. The dimensionless weighted standard deviation of the fit is 2.8. The fitted set of 237 effective Hamiltonian parameters allowed reproducing 24,991 measured line positions of 494 bands with a root mean squares deviation 0.0037 cm-1. The eigenfunctions of the effective Hamiltonian corresponding to the fitted set of parameters were used to fit the observed line intensities collected from the literature for 15 series of transitions: ΔP = 0-13,15, where P=5V1+5V3 +3V2+V4+V5 is the polyad number (Vi are the principal vibrational quantum numbers). The fitted sets of the effective dipole moment parameters reproduce the observed line intensities within their experimental uncertainties 2-20%.
Jacobs, M. H.; Van Den Berg, A. P.
2013-12-01
Thermodynamic databases are indispensable tools in materials science and mineral physics to derive thermodynamic properties in regions of pressure-temperature-composition space for which experimental data are not available or scant. Because the amount of phases and substances in a database is arbitrarily large, thermodynamic formalisms coupled to these databases are often kept as simple as possible to sustain computational efficiency. Although formalisms based on parameterizations of 1 bar thermodynamic data, commonly used in Calphad methodology, meet this requirement, physically unrealistic behavior in properties hamper the application in the pressure regime prevailing in the Earth's lower mantle. The application becomes especially cumbersome when they are applied to planetary mantles of massive super earth exoplanets or in the development of pressure scales, where Hugoniot data at extreme conditions are involved. Methods based on the Mie-Grüneisen-Debye formalism have the advantage that physically unrealistic behavior in thermodynamic properties is absent, but due to the simple construction of the vibrational density of states (VDoS), they lack engineering precision in the low-pressure regime, especially at 1 bar pressure, hampering application of databases incorporating such formalism to industrial processes. To obtain a method that is generally applicable in the complete stability range of a material, we developed a method based on an alternative use of Kieffer's lattice vibrational formalism. The method requires experimental data to constrain the model parameters and is therefore semi-empirical. It has the advantage that microscopic properties for substances, such as the VDoS, Grüneisen parameters and electronic and static lattice properties resulting from present-day ab-initio methods can be incorporated to constrain a thermodynamic analysis of experimental data. It produces results free from physically unrealistic behavior at high pressure and temperature
Takács, Gergely
2012-01-01
Real-time model predictive controller (MPC) implementation in active vibration control (AVC) is often rendered difficult by fast sampling speeds and extensive actuator-deformation asymmetry. If the control of lightly damped mechanical structures is assumed, the region of attraction containing the set of allowable initial conditions requires a large prediction horizon, making the already computationally demanding on-line process even more complex. Model Predictive Vibration Control provides insight into the predictive control of lightly damped vibrating structures by exploring computationally efficient algorithms which are capable of low frequency vibration control with guaranteed stability and constraint feasibility. In addition to a theoretical primer on active vibration damping and model predictive control, Model Predictive Vibration Control provides a guide through the necessary steps in understanding the founding ideas of predictive control applied in AVC such as: · the implementation of ...
Nonlinear (Anharmonic Casimir Oscillator
Directory of Open Access Journals (Sweden)
Habibollah Razmi
2011-01-01
Full Text Available We want to study the dynamics of a simple linear harmonic micro spring which is under the influence of the quantum Casimir force/pressure and thus behaves as a (an nonlinear (anharmonic Casimir oscillator. Generally, the equation of motion of this nonlinear micromechanical Casimir oscillator has no exact solvable (analytical solution and the turning point(s of the system has (have no fixed position(s; however, for particular values of the stiffness of the micro spring and at appropriately well-chosen distance scales and conditions, there is (are approximately sinusoidal solution(s for the problem (the variable turning points are collected in a very small interval of positions. This, as a simple and elementary plan, may be useful in controlling the Casimir stiction problem in micromechanical devices.
Studying and Modeling Vibration Transducers and Accelerometers
Directory of Open Access Journals (Sweden)
Katalin Ágoston
2010-12-01
Full Text Available This paper presents types and operating mode of vibration sensors. Piezoelectric sensing elements are often used in accelerometers. It will be investigate the structure and transfer function of the seismic mass type sensing element. The article presents how the piezoelectric sensing element works and how can be modeled with an electronic circuit. The transfer functions of the electronic circuit models are studied in Matlab and the results are presented. It will be presented the influence of the seismic mass on the accelerometer’s working frequency domain.
Modelling the vibration of tyre sidewalls
Graham, W. R.
2013-10-01
The dynamical behaviour of the sidewall has an important influence on tyre vibration characteristics. Nonetheless, it remains crudely represented in many existing models. The current work considers a geometrically accurate, two-dimensional, sidewall description, with a view to identifying potential shortcomings in the approximate formulations and identifying the physical characteristics that must be accounted for. First, the mean stress state under pressurisation and centrifugal loading is investigated. Finite-Element calculations show that, while the loaded sidewall shape remains close to a toroid, its in-plane tensions differ appreciably from the associated analytical solution. This is largely due to the inability of the anisotropic sidewall material to sustain significant azimuthal stress. An approximate analysis, based on the meridional tension alone, is therefore developed, and shown to yield accurate predictions. In conjunction with a set of formulae for the ‘engineering constants’ of the sidewall material, the approximate solutions provide a straightforward and efficient means of determining the base state for the vibration analysis. The latter is implemented via a ‘waveguide’ discretisation of a variational formulation. Its results show that, while the full geometrical description is necessary for a complete and reliable characterisation of the sidewall's vibrational properties, a one-dimensional approximation will often be satisfactory in practice. Meridional thickness variations only become important at higher frequencies (above 500 Hz for the example considered here), and rotational inertia effects appear to be minor at practical vehicle speeds.
Czech Academy of Sciences Publication Activity Database
Ceausu-Velcescu, A.; Pracna, Petr
2012-01-01
Roč. 275, č. 276 (2012), s. 41-47. ISSN 0022-2852 Institutional support: RVO:61388955 Keywords : deuterated fluoroform * anharmonic * coriolis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.670, year: 2012
A shell model for tyre belt vibrations
Lecomte, C.; Graham, W. R.; Dale, M.
2010-05-01
We present a new formulation for the prediction of tyre belt vibrations in the frequency range 0-500 Hz. Our representation includes the effects of belt width, curvature and anisotropy, and also explicitly models the tyre sidewalls. Many of the associated numerical parameters are fixed by physical considerations; the remainder require empirical input. A systematic and general approach to this problem is developed, and illustrated for the specific example of a Goodyear Wrangler tyre. The resulting predictions for the radial response to radial forcing show good correspondence with experiment up to 300 Hz, and satisfactory agreement up to 1 kHz.
International Nuclear Information System (INIS)
A quantum model of a heterogeneous system consisting of a mixture of isotopes adsorbed on a solid surface and subjected to laser radiation is presented. The model system is described by a total Hamiltonian including direct and indirect (surface-phonon-mediated) couplings. The equations of motion are derived in the Heisenberg--Markovian picture in which the many-body effects of the surface phonon modes and the adspecies are reduced to an overall broadening (damping factor) given by the sum of the energy (T1) and phase (T 2) relaxations. The effects of the dephasing and anharmonicity on the average excitation are investigated. The ''bistability'' feature with a red-shifted optimal detuning is discussed in terms of the solution of a cubic equation. A diagonalization procedure is presented in a new basis which reveals the effects of the coupling strength, the frequency difference, and the level width of the isotopes on the total steady-state excitation, which in turn reflects the surface spectrum of the model system. Finally, the isotope selectivity given by the numerical results of the time-integrated excitation is discussed. It is shown that the optimal detuning for a weak coupling strength is further red-shifted for a strong isotopic coupling strength. Finally, energy feedback effects of the bath modes on the excitations of the active modes are investigated by combining a quantum excitation equation and a classical heat diffusion equation
Fermi resonance-algebraic model for molecular vibrational spectra
Institute of Scientific and Technical Information of China (English)
侯喜文; 董世海; 谢汨; 马中骐
1999-01-01
A Fermi resonance-algebraic model is proposed for molecular vibrations, where a U(2) algebra is used for describing the vibrations of each bond, and Fermi resonances between stretching and bending modes are taken into account. The model for a bent molecule XY2 and a molecule XY3 is successfully applied to fitting the recently observed vibrational spectrum of the water molecule and arsine (AsH3), respectively, and the results are compared with those of other models. Calculations show that algebraic approaches can be used as an effective method to describe molecular vibrations with small standard deviations.
Low Dimensional Models of Shell Vibrations. Parametrically Excited Vibrations of Cylinder Shells
Popov, A. A.; Thompson, J. M. T.; McRobie, F. A.
1998-01-01
Vibrations of cylindrical shells parametrically excited by axial forcing are considered. The governing system of two coupled non-linear partial differential equations is discretized by using Lagrange equations. The computation is simplified significantly by the application of computer algebra and as a result low dimensional models of shell vibrations are readily obtained. After applying numerical continuation techniques and ideas from dynamical systems theory, complete bifurcation diagrams are constructed. The principal aim is to investigate the interaction between different modes of shell vibration. Results for system models with two of the lowest modes are discussed.
A vibration model for centrifugal contactors
Energy Technology Data Exchange (ETDEWEB)
Leonard, R.A.; Wasserman, M.O.; Wygmans, D.G.
1992-11-01
Using the transfer matrix method, we created the Excel worksheet ``Beam`` for analyzing vibrations in centrifugal contactors. With this worksheet, a user can calculate the first natural frequency of the motor/rotor system for a centrifugal contactor. We determined a typical value for the bearing stiffness (k{sub B}) of a motor after measuring the k{sub B} value for three different motors. The k{sub B} value is an important parameter in this model, but it is not normally available for motors. The assumptions that we made in creating the Beam worksheet were verified by comparing the calculated results with those from a VAX computer program, BEAM IV. The Beam worksheet was applied to several contactor designs for which we have experimental data and found to work well.
A vibration model for centrifugal contactors
International Nuclear Information System (INIS)
Using the transfer matrix method, we created the Excel worksheet ''Beam'' for analyzing vibrations in centrifugal contactors. With this worksheet, a user can calculate the first natural frequency of the motor/rotor system for a centrifugal contactor. We determined a typical value for the bearing stiffness (kB) of a motor after measuring the kB value for three different motors. The kB value is an important parameter in this model, but it is not normally available for motors. The assumptions that we made in creating the Beam worksheet were verified by comparing the calculated results with those from a VAX computer program, BEAM IV. The Beam worksheet was applied to several contactor designs for which we have experimental data and found to work well
Detecting anharmonicity at a glance
International Nuclear Information System (INIS)
Harmonic motion is generally presented in such a way that most of the students believe that the small oscillations of a body are all harmonic. Since the situation is not actually so simple, and since the comprehension of harmonic motion is essential in many physical contexts, we present here some suggestions, addressed to undergraduate students and pre-service teachers, that allow one to find out at a glance the anharmonicity of a motion. Starting from a didactically motivated definition of harmonic motion, and stressing the importance of the interplay between mathematics and experiments, we give a four-point criterion for anharmonicity together with some emblematic examples. The role of linear damping is also analysed in relation to the gradual changing of harmonicity into anharmonicity when the ratio between the damping coefficient and the zero-friction angular frequency increases. (paper)
Detecting anharmonicity at a glance
Giliberti, M.; Stellato, M.; Barbieri, S.; Cavinato, M.; Rigon, E.; Tamborini, M.
2014-11-01
Harmonic motion is generally presented in such a way that most of the students believe that the small oscillations of a body are all harmonic. Since the situation is not actually so simple, and since the comprehension of harmonic motion is essential in many physical contexts, we present here some suggestions, addressed to undergraduate students and pre-service teachers, that allow one to find out at a glance the anharmonicity of a motion. Starting from a didactically motivated definition of harmonic motion, and stressing the importance of the interplay between mathematics and experiments, we give a four-point criterion for anharmonicity together with some emblematic examples. The role of linear damping is also analysed in relation to the gradual changing of harmonicity into anharmonicity when the ratio between the damping coefficient and the zero-friction angular frequency increases.
Anharmonic densities of states: A general dynamics-based solution
Jellinek, Julius; Aleinikava, Darya
2016-06-01
Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.
Partial dynamical symmetry and anharmonicity in γ-soft nuclei
International Nuclear Information System (INIS)
The concept of dynamical symmetry (DS) is now widely accepted to be of central importance in our understanding of many-body systems, such as nuclei. Its hallmarks are the solvability of the complete spectrum, and the existence of exact quantum numbers for all eigenstates. However, in most applications to realistic systems, the predictions of an exact DS are rarely fulfilled and one is compelled to break it. More often one finds that the assumed symmetry is not obeyed uniformly, i.e., is fulfilled by only some states but not by others. The need to address such situations has led to the introduction of partial dynamical symmetries (PDSs). The essential idea is to relax the stringent conditions of complete solvability, so that the DS is broken, but part of the eigen spectrum remains solvable with good symmetry. Various types of bosonic and fermionic PDS, have been shown to be relevant to nuclear spectroscopy [1-7] and to quantum phase transitions [8]. In the present contribution we extend the notion of PDS to encompass Hamiltonians with higher-order terms. We present a systematic procedure for constructing such PDS Hamiltonians and demonstrate their relevance to the anharmonicity of excited bands in the -soft nucleus 196Pt. The work, to be reported, was done in collaboration with J.E. Garcfa-Ramos (Huelva) and P. Van backer (GANIL) [9]. The SO(6)-DS limit of the interacting boson model (IBM) [10], provides a good description of the rotational spectrum and E2 rates for states in the ground band of 196Pt [11]. However, the resulting fit to energies of excited bands is quite poor. The empirical anharmonicity of excited vibrational bands is large and negative. On the other hand, in the SO(6)-DS limit, the calculated anharmonicity is fixed by the number of valence nucleons, and is found to be in marked disagreement with the empirical value. A detailed study of double-phonon excitations within the IBM, has concluded that large anharmonicities can be incorporated only by the
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.
Institute of Scientific and Technical Information of China (English)
陈恒杰; 方旺; 刘丰奎; 薛善增
2014-01-01
采用包含迭代三激发的耦合簇理论（ CC3和CCSDT-3），在aug-cc-pVTZ基组水平上对HOF分子几何构型进行优化。通过解析二阶导数结合有限差分技术获得HOF二阶、完全三阶和半对角四阶力场。通过非谐性分析，得到其基频、旋振相互作用常数、非谐性常数和离心畸变光谱常数。应用二阶振动微扰理论（VPT2）得到HOF多个泛频峰位置。目前计算值与实验及其它文献结果符合良好。%The molecular equilibrium structure of HOF has been optimized using iterative triplet coupled cluster approach (CC3 and CCSDT-3) together with aug-cc-pVTZ basis set.Quadratic, full cubic and semidiagonal part of the quartic force field have been obtained by the analytic second derivatives and finite difference techniques. Fundamental frequencies, vibration-rotation interaction constants, anharmonic constants and centrifugal distor-tion constants have been evaluated according to the anharmonic analytics.Several overtones have been expected by the vibrational second-order perturbation theory ( VPT2 ) .The present calculation values are in good agree-ment with others theoretical and experimental results.
Iyer, Srikanth S.; Candler, Robert N.
2016-03-01
In this work, we determine the intrinsic mechanical energy dissipation limit for single-crystal resonators due to anharmonic phonon-phonon scattering in the Akhiezer (Ω τ ≪1 ) regime. The energy loss is derived using perturbation theory and the linearized Boltzmann transport equation for phonons, and includes the direction- and polarization-dependent mode-Grüneisen parameters in order to capture the strain-induced anharmonicity among phonon branches. This expression reveals the fundamental differences among the internal friction limits for different types of bulk-mode elastic waves. For cubic crystals, 2D-extensional modes have increased dissipation compared to width-extensional modes because the biaxial deformation opposes the natural Poisson contraction of the solid. Additionally, we show that shear-mode vibrations, which preserve volume, have significantly reduced energy loss because dissipative phonon-phonon scattering is restricted to pure-shear phonon branches, indicating that Lamé- or wineglass-mode resonators will have the highest upper limit on mechanical efficiency. Finally, we employ key simplifications to evaluate the quality factor limits for common mode shapes in single-crystal silicon devices, explicitly including the correct effective elastic storage moduli for different vibration modes and crystal orientations. Our expression satisfies the pressing need for a reliable analytical model that can predict the phonon-phonon dissipation limits for modern resonant microelectromechanical systems, where precise manufacturing techniques and accurate finite-element methods can be used to select particular vibrational mode shapes and crystal orientations.
Vibration induced flow in hoppers: DEM 2D polygon model
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
A two-dimensional discrete element model (DEM) simulation of cohesive polygonal particles has been developed to assess the benefit of point source vibration to induce flow in wedge-shaped hoppers. The particle-particle interaction model used is based on a multi-contact principle.The first part of the study investigated particle discharge under gravity without vibration to determine the critical orifice size (Be) to just sustain flow as a function of particle shape. It is shown that polygonal-shaped particles need a larger orifice than circular particles. It is also shown that Be decreases as the number of particle vertices increases. Addition of circular particles promotes flow of polygons in a linear manner.The second part of the study showed that vibration could enhance flow, effectively reducing Be. The model demonstrated the importance of vibrator location (height), consistent with previous continuum model results, and vibration amplitude in enhancing flow.
Maltseva, Elena; Candian, Alessandra; Mackie, Cameron J; Huang, Xinchuan; Lee, Timothy J; Tielens, Alexander G G M; Oomens, Jos; Buma, Wybren Jan
2015-01-01
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micron CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold (~4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilises intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination ...
Positive Anharmonicities: The Oxonide Anion as an Example
Lee, Timothy J.; Arnold, James O. (Technical Monitor)
1997-01-01
An accurate ab initio quartic force field for the ozonide anion has been determined at the singles and doubles coupled-cluster level of theory that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T), using the augmented valence triple-zeta correlation consistent one-particle basis set. Convergence of the harmonic frequencies with respect to the one-particle basis set has been demonstrated by computing quadratic force fields at the CCSD(T) level using augmented valence double-zeta and quadruple-zeta basis sets. Fundamental vibrational frequencies have been determined via second-order ro-vibrational perturbation theory and also using exact variational methods. Agreement is very good, and they both show that the antisymmetric O-O stretch, v 3, possesses a positive anharmonic correction (that is, the fundamental frequency is predicted to be higher in energy than the harmonic frequency). Comparison of the O_3 and O3 quartic force fields shows that the positive anharmonic correction is the result of a particularly large F3333 symmetry internal coordinate force constant. The reasonableness of this force constant has been tested by computing both F33 and F3333 at the CCSD, CCSD(T), and CASPT2 levels of theory. A discussion of known positive anharmonicities for stretching modes is presented.
THEORETICAL MODEL OF VIBRATING OBJECT TRANSMITTING NOISE TOWARDS EXTERNAL SOUND
Institute of Scientific and Technical Information of China (English)
姚志远
2002-01-01
On the basic theory of modal method, the coupling relation between the vibration of objects and external sound was analyzed, the theoretical model solving the vibration and noise was provided, the corresponding calculation formula was given. The calculating results show out that this calculation formula is correct.
The spectroscopic constants and anharmonic force field of AgSH: An ab initio study.
Zhao, Yanliang; Wang, Meishan; Yang, Chuanlu; Ma, Xiaoguang; Zhu, Ziliang
2016-07-01
The equilibrium structure, spectroscopy constants, and anharmonic force field of silver hydrosulfide (AgSH) have been calculated at B3P86, B3PW91 and MP2 methods employing two basis sets, TZP and QZP, respectively. The calculated geometries, ground state rotational constants, harmonic vibrational wave numbers, and quartic and sextic centrifugal distortion constants are compared with the available experimental and theoretical data. The equilibrium rotational constants, fundamental frequencies, anharmonic constants, and vibration-rotation interaction constants, Coriolis coupling constants, cubic and quartic force constants are predicted. The calculated results show that the MP2/TZP results are in good agreement with experiment observation and are also an advisable choice to study the anharmonic force field of AgSH. PMID:27085293
Bishop, David M.; Luis Luis, Josep Maria; Kirtman, Bernard
1998-01-01
Compact expressions, complete through second order in electrical and/or mechanical anharmonicity, are given for the dynamic dipole vibrational polarizability and dynamic first and second vibrational hyperpolarizabilities. Certain contributions not previously formulated are now included
Vibration Reduction Evaluation of an Isolated EDG Model
International Nuclear Information System (INIS)
A vibration and noise are among one of the well known problems of a rotational machine. An Emergency Diesel Generator (EDG) is one of the safety related equipment of a Nuclear Power Plant. The EDG system also has a vibration problem. Kim, et al studied the operating vibration problem of the EDG system in Yonggwang 5, Ulchin 2 and 3 unit. Foundation systems of the Yongwang 5, Ulchin 2 and 3 unit EDG systems are an anchor bolt, coil spring with a seismic mass and a coil spring and viscous damper system, respectively. But in these cases it is impossible to evaluate the vibration reduction effect according to the spring system. So, in this study, a small scale EDG model and a spring-damper system were developed and a vibration was measured. For a producing a sine wave vibration, a vibration generator was produced. As a result, at least 80% of a vibration was decreased by using the coil spring and viscous damper system
Unexpected red shift of C-H vibrational band of Methyl benzoate
Maiti, Kiran Sankar; Scheurer, Christoph
2016-01-01
The C-H vibrational bands become more and more important in the structural determination of biological molecules with the development of CARS microscopy and 2DIR spectroscopy. Due to the congested pattern, near degeneracy, and strong anharmonicity of the C-H stretch vibrations, assignment of the C-H vibrational bands are often misleading. Anharmonic vibrational spectra calculation with multidimensional potential energy surface interprets the C-H vibrational spectra more accurately. In this article we have presented the importance of multidimensional potential energy surface in anharmonic vibrational spectra calculation and discuss the unexpected red shift of C-H vibrational band of Methyl benzoate.
Vibration Response of Multi Storey Building Using Finite Element Modelling
Chik, T. N. T.; Zakaria, M. F.; Remali, M. A.; Yusoff, N. A.
2016-07-01
Interaction between building, type of foundation and the geotechnical parameter of ground may trigger a significant effect on the building. In general, stiffer foundations resulted in higher natural frequencies of the building-soil system and higher input frequencies are often associated with other ground. Usually, vibrations transmitted to the buildings by ground borne are often noticeable and can be felt. It might affect the building and become worse if the vibration level is not controlled. UTHM building is prone to the ground borne vibration due to closed distance from the main road, and the construction activities adjacent to the buildings. This paper investigates the natural frequency and vibration mode of multi storey office building with the presence of foundation system and comparison between both systems. Finite element modelling (FEM) package software of LUSAS is used to perform the vibration analysis of the building. The building is modelled based on the original plan with the foundation system on the structure model. The FEM results indicated that the structure which modelled with rigid base have high natural frequency compare to the structure with foundation system. These maybe due to soil structure interaction and also the damping of the system which related to the amount of energy dissipated through the foundation soil. Thus, this paper suggested that modelling with soil is necessary to demonstrate the soil influence towards vibration response to the structure.
Origin of the large anharmonicity in the phonon modes of LiBH{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Gremaud, R.; Züttel, A. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory 505 (Hydrogen and Energy), Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Borgschulte, A., E-mail: andreas.borgschulte@empa.ch [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory 505 (Hydrogen and Energy), Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Ramirez-Cuesta, A.J.; Refson, K. [Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, PO Box 2008, MS 6473 Oak Ridge (United States); Colognesi, D. [Istituto dei Sistemi Complessi – sezione di Firenze, Consiglio Nazionale delle Ricerche, via Madonna del piano 10, 50019 Sesto Fiorentino (Italy)
2013-12-12
Highlights: • IR, Raman, and INS spectroscopy data and corresponding DFT-calculations on LiBH4. • Mismatch between experiment and theory are due to anharmonicity. • Strong anharmonic effects can be expected for vibrations with high H amplitude. - Abstract: The dynamics and bonding of the complex hydride LiBH{sub 4} have been investigated by vibrational spectroscopy and density functional theory (DFT). The combination of infrared, Raman, and inelastic neutron-scattering (INS) spectroscopies on hydrided and deuterated samples reveals a complete picture of the dynamics of the BH{sub 4}{sup −} ions as well as of the lattice. Particular emphasis is laid on a comparison between experiment and theory, revealing significant discrepancy between the two approaches for vibrations with high anharmonicity, which is related to large vibrational amplitudes. The latter is typical for librational modes in molecular crystals and pseudo-ionic crystals such as complex hydrides. The presented strategy for anharmonic frequency corrections might thus be generally applicable for this kind of materials.
Mathematical modeling of mechanical vibration assisted conductivity imaging
Ammari, Habib; Kwon, Hyeuknam; Seo, Jin Keun; Woo, Eung Je
2014-01-01
This paper aims at mathematically modeling a new multi-physics conductivity imaging system incorporating mechanical vibrations simultaneously applied to an imaging object together with current injections. We perturb the internal conductivity distribution by applying time-harmonic mechanical vibrations on the boundary. This enhances the effects of any conductivity discontinuity on the induced internal current density distribution. Unlike other conductivity contrast enhancing frameworks, it does not require a prior knowledge of a reference data. In this paper, we provide a mathematical framework for this novel imaging modality. As an application of the vibration-assisted impedance imaging framework, we propose a new breast image reconstruction method in electrical impedance tomography (EIT). As its another application, we investigate a conductivity anomaly detection problem and provide an efficient location search algorithm. We show both analytically and numerically that the applied mechanical vibration increas...
Modeling of Axial Spring Stiffness in Active Vibration Controlled Drilling
Directory of Open Access Journals (Sweden)
Pao William
2014-07-01
Full Text Available During drilling process, substantial amount of vibration and shock are induced to the drill string. Active vibration controlled drilling is introduced to reduce the vibration and increase the efficiency of drilling process. In this system, two main components that determine the damping coefficient are magnetorheological (MR damper and spring assembly. Performance of vibration damping system is depending on the viscosity of MR fluid in the damper and spring constant of spring assembly. One of the key issues that are unclear from the design is the correlation between the axial spring stiffness configuration and the damping force which needs to be tuned actively. There has been lack of studies on how the viscosity of MR fluid on the active vibration damper affects the damping stiffness of the whole system. The objective of the project is to extract the correlations for the viscous damping coefficient, equivalent spring stiffness and power input to the system. Simplified vibration model is thus created using Simulink, together with experimental data fed from APS Technology’s in-house team. Inputs of the simulation such as force exerted, mass of mandrel, spring constant and step time are based on the experimental data and can be adjusted to suit different experiments. By having the model, behavior of the system can be studied and analyzed. From the simulation, it is also observed that the relationship between damping coefficient and power input of the system is linear.
On the Applicability of the Caldeira-Leggett Model to Condensed Phase Vibrational Spectroscopy
Ivanov, Sergei D; Kühn, Oliver
2014-01-01
Formulating a rigorous system-bath partitioning approach remains an open issue. In this context the famous Caldeira-Leggett (CL) model that enables quantum and classical treatment of Brownian motion on equal footing has enjoyed popularity. Although this model is by any means a useful theoretical tool, its validity for describing anharmonic dynamics of real systems is often taken for granted. In this Letter we show that the model is not able to describe real systems unless the system part of the potential is taken effectively harmonic. We demonstrate that the deficiencies of the model are rooted in the anharmonicity. Further, we elaborate on the mathematical origin of the breakdown of the CL model.
Methyl group dynamics and the onset of anharmonicity in myoglobin
International Nuclear Information System (INIS)
The role of methyl groups in the onset of low-temperature anharmonic dynamics in a crystalline protein at low temperature is investigated using atomistic molecular dynamics (MD) simulation. Anharmonicity appears at 150 ∼ K, far below the much-studied solvent-activated dynamical transition at ∼ 220 K. A significant fraction of methyl groups exhibit nanosecond time scale rotational jump diffusion at 150 K. The splitting and shift in peak position of both the librational band (around 100 cm-1) and the torsional band (around 270?300 cm-1) also differ significantly among methyl groups, depending on the local environment. The simulation results provide no evidence for a correlation between methyl dynamics and solvent exposure, consistent with the hydration-independence of the low-temperature anharmonic dynamics observed in neutron scattering experiments. The calculated proton mean-square fluctuation and methyl NMR order parameters show a systematic nonlinear dependence on the rotational barrier which can be described using model functions. The methyl groups that exhibit many rotational excitations are located near xenon cavities, suggesting that cavities in proteins act as activation centers of anharmonic dynamics. The dynamic heterogeneity and the environmental sensitivity of motional parameters and low-frequency spectral bands of CH3 groups found here suggest that methyl dynamics may be used as a probe to investigate the relation between low-energy structural fluctuations and packing defects in proteins
The Modeling of Vibration Damping in SMA Wires
Energy Technology Data Exchange (ETDEWEB)
Reynolds, D R; Kloucek, P; Seidman, T I
2003-09-16
Through a mathematical and computational model of the physical behavior of shape memory alloy wires, this study shows that localized heating and cooling of such materials provides an effective means of damping vibrational energy. The thermally induced pseudo-elastic behavior of a shape memory wire is modeled using a continuum thermodynamic model and solved computationally as described by the authors in [23]. Computational experiments confirm that up to 80% of an initial shock of vibrational energy can be eliminated at the onset of a thermally-induced phase transformation through the use of spatially-distributed transformation regions along the length of a shape memory alloy wire.
International Nuclear Information System (INIS)
The multiphonon method, which is an exact diagonalization in the restricted space of collective phonons of different types, is tested in a simple two shell model allowing an exact solution for a many body system of fermions interacting via pairing plus quadrupole and octupole forces. It appears satisfactory for the description of the anharmonicities of the lowest-lying vibrational Ksup(π) = 0+ and 0- states in deformed nuclei. In particular, it allows electromagnetic transitions between the different one phonon states, which are completely forbidden in any harmonic treatment as TDA or RPA. It seems also that a restriction to the space spanned by the two lowest collective phonons of different type is sufficient for the description of the spectroscopic properties of the corresponding levels
Noise, vibration, harshness model of a rotating tyre
Bäcker, Manfred; Gallrein, Axel; Roller, Michael
2016-04-01
The tyre plays a fundamental role in the generation of acoustically perceptible driving noise and vibrations inside the vehicle. An essential part of these vibrations is induced by the road excitation and transferred via the tyre into the vehicle. There are two basic ways to study noise, vibration, harshness (NVH) behaviour: Simulations in time and frequency domains. Modelling the tyre transfer behaviour in frequency domain requires special attention to the rotation of the tyre. This paper shows the approach taken by the authors to include the transfer behaviour in the frequency range up to 250 Hz from geometric road excitations to resulting spindle forces in frequency domain. This paper validates the derived NVH tyre model by comparison with appropriate transient simulations of the base transient model.
Vibrational spectrum of CF4 isotopes in an algebraic model
Indian Academy of Sciences (India)
Joydeep Choudhury; Srinivasa Rao Karumuri; Nirmal Kumar Sarkar; Ramendu Bhattacharjee
2009-11-01
n this paper the stretching vibrational modes of CF4 isotopes are calculated up to first overtone using the one-dimensional vibron model for the first time. The model Hamiltonian so constructed seems to describe the C–F stretching modes accurately using a relatively small set of well-defined parameters.
Lattice thermal conductivity of filled skutterudites: An anharmonicity perspective
International Nuclear Information System (INIS)
We report a phenomenological model to calculate the high-temperature lattice thermal conductivity of filled skutterudite antimonides. The model needs no phonon resonant scattering terms. Instead, we assume that umklapp processes dominate the high-temperature phonon scattering. In order to represent the anharmonicity introduced by the filling atom, we introduce a Gaussian term into the relaxation time of the umklapp process. The developed model agrees remarkably well with the experimental results of REfCo4Sb12 and REfFe4Sb12 (RE = Yb, Ba, and Ca) alloys. To further test the validity of our model, we calculate the lattice thermal conductivity of nanostructured or multi-filled skutterudites. The calculation results are also in good agreement with experiment, increasing our confidence in the developed anharmonicity model.
Ground state properties of a Bose-Einstein condensate confined in an anharmonic external potential
Institute of Scientific and Technical Information of China (English)
Wang Deng-Long; Yan Xiao-Hong; Tang Yi
2004-01-01
In light of the interference experiment of Bose-Einstein condensates, we present an anharmonic external potential model to study ground state properties of Bose-Einstein condensates. The ground state energy and the chemical potential have been analytically obtained, which are lower than those in harmonic trap. Additionally, it is found that the anharmonic strength of the external potential has an important effect on density and velocity distributions of the ground state for the Thomas-Fermi model.
International Nuclear Information System (INIS)
We show a first-principles approach for analyzing anharmonic properties of lattice vibrations in solids. We firstly extract harmonic and anharmonic force constants from accurate first-principles calculations based on the density functional theory. Using the many-body perturbation theory of phonons, we then estimate the phonon scattering probability due to anharmonic phonon-phonon interactions. We show the validity of the approach by computing the lattice thermal conductivity of Si, a typical covalent semiconductor, and selected thermoelectric materials PbTe and Bi2Te3 based on the Boltzmann transport equation. We also show that the phonon lifetime and the lattice thermal conductivity of the high-temperature phase of SrTiO3 can be estimated by employing the perturbation theory on top of the solution of the self-consistent phonon equation
Energy Technology Data Exchange (ETDEWEB)
Tadano, Terumasa [Department of Applied Physics, The University of Tokyo, Tokyo 113-8656 (Japan); Tsuneyuki, Shinji [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan); Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581 (Japan)
2015-12-31
We show a first-principles approach for analyzing anharmonic properties of lattice vibrations in solids. We firstly extract harmonic and anharmonic force constants from accurate first-principles calculations based on the density functional theory. Using the many-body perturbation theory of phonons, we then estimate the phonon scattering probability due to anharmonic phonon-phonon interactions. We show the validity of the approach by computing the lattice thermal conductivity of Si, a typical covalent semiconductor, and selected thermoelectric materials PbTe and Bi{sub 2}Te{sub 3} based on the Boltzmann transport equation. We also show that the phonon lifetime and the lattice thermal conductivity of the high-temperature phase of SrTiO{sub 3} can be estimated by employing the perturbation theory on top of the solution of the self-consistent phonon equation.
Scale modeling flow-induced vibrations of reactor components
International Nuclear Information System (INIS)
Similitude relationships currently employed in the design of flow-induced vibration scale-model tests of nuclear reactor components are reviewed. Emphasis is given to understanding the origins of the similitude parameters as a basis for discussion of the inevitable distortions which occur in design verification testing of entire reactor systems and in feature testing of individual component designs for the existence of detrimental flow-induced vibration mechanisms. Distortions of similitude parameters made in current test practice are enumerated and selected example tests are described. Also, limitations in the use of specific distortions in model designs are evaluated based on the current understanding of flow-induced vibration mechanisms and structural response
The importance of anharmonicity in thermal transport across solid-solid interfaces
International Nuclear Information System (INIS)
Understanding interfacial thermal transport is of great importance for applications like energy devices and thermal management of electronics. Despite the significant efforts in the past few decades, thermal transport across solid-solid interfaces is still not fully understood and cannot be accurately predicted. Anharmonicity is often ignored in many prediction models, such as the mismatch models, the wave-packet method, and the Atomic Green's function. In this paper, we use molecular dynamics to systematically study the role of anharmonicity in thermal transport across solid-solid interfaces. The interatomic interactions are modeled using force constants up to the third order. This model allows controlling the anharmonicity independently by tuning the cubic force constants. The interfacial thermal conductance as a function of anharmonicity inside the materials and that at the interface is studied. We found that the anharmonicity inside the materials plays an important role in the interfacial thermal transport by facilitating the energy communication between different phonon modes. The anharmonicity at the interface has much less impact on the interfacial thermal transport. These results are important to the modification of traditional models to improve their prediction power
Maltseva, Elena; Petrignani, Annemieke; Candian, Alessandra; Mackie, Cameron J.; Huang, Xinchuan; Lee, Timothy J.; Tielens, Alexander G. G. M.; Oomens, Jos; Buma, Wybren Jan
2016-01-01
We report on an experimental and theoretical investigation of the importance of anharmonicity in the 3 micrometers CH stretching region of Polycyclic Aromatic Hydrocarbon (PAH) molecules. We present mass-resolved, high-resolution spectra of the gas-phase cold ((is) approximately 4K) linear PAH molecules naphthalene, anthracene, and tetracene. The measured IR spectra show a surprisingly high number of strong vibrational bands. For naphthalene, the observed bands are well separated and limited by the rotational contour, revealing the band symmetries. Comparisons are made to the harmonic and anharmonic approaches of the widely used Gaussian software. We also present calculated spectra of these acenes using the computational program SPECTRO, providing anharmonic predictions enhanced with a Fermi-resonance treatment that utilizes intensity redistribution. We demonstrate that the anharmonicity of the investigated acenes is strong, dominated by Fermi resonances between the fundamental and double combination modes, with triple combination bands as possible candidates to resolve remaining discrepancies. The anharmonic spectra as calculated with SPECTRO lead to predictions of the main modes that fall within 0.5% of the experimental frequencies. The implications for the Aromatic Infrared Bands, specifically the 3-m band are discussed.
Modeling vibration response and damping of cables and cabled structures
Spak, Kaitlin S.; Agnes, Gregory S.; Inman, Daniel J.
2015-02-01
In an effort to model the vibration response of cabled structures, the distributed transfer function method is developed to model cables and a simple cabled structure. The model includes shear effects, tension, and hysteretic damping for modeling of helical stranded cables, and includes a method for modeling cable attachment points using both linear and rotational damping and stiffness. The damped cable model shows agreement with experimental data for four types of stranded cables, and the damped cabled beam model shows agreement with experimental data for the cables attached to a beam structure, as well as improvement over the distributed mass method for cabled structure modeling.
International Nuclear Information System (INIS)
We clarify the role of the critical imidazolium C(2)H position (the central C between N atoms in the heterocycle) in the assembly motif of the [EMIM][BF4] ionic liquid by analyzing the vibrational spectra of the bare EMIM+ ion as well as that of the cationic [EMIM]2[BF4]+ (EMIM+ = 1-ethyl-3-methylimidazolium, C6H11N2+) cluster. Vibrational spectra of the cold, mass-selected ions are obtained using cryogenic ion vibrational predissociation of weakly bound D2 molecules formed in a 10 K ion trap. The C(2)H behavior is isolated by following the evolution of key vibrational features when the C(2) hydrogen, the proposed binding location of the anion to the imidazolium ring, is replaced by either deuterium or a methyl group (i.e., in the EMMIM+ analogue). Strong features in the ring CH stretching region of the bare ion are traced to Fermi resonances with overtones of lower frequency modes. Upon incorporation into the EMIM+ ⋅ ⋅ ⋅ BF4− ⋅ ⋅ ⋅ EMIM+ ternary complex, the C(2)H oscillator strength is dramatically increased, accounting for the much more complicated patterns derived from the EMIM+ ring CH stretches in the light isotopomer, which are strongly suppressed in the deuterated analogue. Further changes in the spectra that occur when the C(2)H is replaced by a methyl group are consistent with BF4− attachment directly to the imidazolium ring in an arrangement that maximizes the electrostatic interaction between the molecular ions
Dynamical response functions in models of vibrated granular media
Nicodemi, Mario
1998-01-01
In recently introduced schematic lattice gas models for vibrated dry granular media, we study the dynamical response of the system to small perturbations of shaking amplitudes and its relations with the characteristic fluctuations. Strong off equilibrium features appear and a generalized version of the fluctuation dissipation theorem is introduced. The relations with thermal glassy systems and the role of Edwards' compactivity are discussed.
Vibration testing of a 1/4-scale containment model
International Nuclear Information System (INIS)
This paper presents programs for the validation of soil-structure interaction (SSI) analysis methods with data that include ground and structural response motions during natural earthquakes and structural response from low-level vibration tests. The primary source of the data is the 1/4-scale containment building situated in Lotung in a seismically active region of Taiwan. The analysis validation program involves blind predictions of site and structural response to the vibration test excitations and to a selected strong-motion seismic event, and the subsequent comparison of predictions with corresponding measurements. This paper focuses on the vibration testing of the model containment structure and the determination of its dynamic characteristics from the experimental data. The 1/4-scale reinforced concrete containment structure, built by EPRI in cooperation with Taiwan Power Company, is located within an array of strong-motion seismographs, known as the SMART-1 array
Anharmonic effects in the optical and acoustic bending modes of graphene
Ramírez, R.; Chacón, E.; Herrero, C. P.
2016-06-01
The out-of-plane fluctuations of carbon atoms in a graphene sheet have been studied by means of classical molecular dynamic simulations with an empirical force field as a function of temperature. The Fourier analysis of the out-of-plane fluctuations often applied to characterize the acoustic bending mode of graphene is extended to the optical branch, whose polarization vector is perpendicular to the graphene layer. This observable is inaccessible in a continuous elastic model of graphene but it is readily obtained by the atomistic treatment. Our results suggest that the long-wavelength limit of the acoustic out-of-plane fluctuations of a free layer without stress is qualitatively similar to that predicted by a harmonic model under a tensile stress. This conclusion is a consequence of the anharmonicity of both in-plane and out-of-plane vibrational modes of the lattice. The most striking anharmonic effect is the presence of a linear term, ωA=vAk , in the dispersion relation of the acoustic bending band of graphene at long wavelengths (k →0 ). This term implies a strong reduction of the amplitude of out-of-plane oscillations in comparison to a flexural mode with a k2 dependence in the long-wavelength limit. Our simulations show an increase of the sound velocity associated to the bending mode, as well as an increase of its bending constant, κ , as the temperature increases. Moreover, the frequency of the optical bending mode, ωO(Γ ), also increases with the temperature. Our results are in agreement with recent analytical studies of the bending modes of graphene using either perturbation theory or an adiabatic approximation in the framework of continuous layer models.
Modeling and vibration control of an active membrane mirror
Ruggiero, Eric J.; Inman, Daniel J.
2009-09-01
The future of space satellite technology lies in ultra-large mirrors and radar apertures for significant improvements in imaging and communication bandwidths. The availability of optical-quality membranes drives a parallel effort for structural models that can capture the dominant dynamics of large, ultra-flexible satellite payloads. Unfortunately, the inherent flexibility of membrane mirrors wreaks havoc with the payload's on-orbit stability and maneuverability. One possible means of controlling these undesirable dynamics is by embedding active piezoelectric ceramics near the boundary of the membrane mirror. In doing so, active feedback control can be used to eliminate detrimental vibration, perform static shape control, and evaluate the health of the structure. The overall motivation of the present work is to design a control system using distributed bimorph actuators to eliminate any detrimental vibration of the membrane mirror. As a basis for this study, a piezoceramic wafer was attached in a bimorph configuration near the boundary of a tensioned rectangular membrane sample. A finite element model of the system was developed to capture the relevant system dynamics from 0 to 300 Hz. The finite element model was compared against experimental results, and fair agreement found. Using the validated finite element models, structural control using linear quadratic regulator control techniques was then used to numerically demonstrate effective vibration control. Typical results show that less than 12 V of actuation voltage is required to eliminate detrimental vibration of the membrane samples in less than 15 ms. The functional gains of the active system are also derived and presented. These spatially descriptive control terms dictate favorable regions within the membrane domain for placing sensors and can be used as a design guideline for structural control applications. The results of the present work demonstrate that thin plate theory is an appropriate modeling
Insight into structural phase transitions from the decoupled anharmonic mode approximation.
Adams, Donat J; Passerone, Daniele
2016-08-01
We develop a formalism (decoupled anharmonic mode approximation, DAMA) that allows calculation of the vibrational free energy using density functional theory even for materials which exhibit negative curvature of the potential energy surface with respect to atomic displacements. We investigate vibrational modes beyond the harmonic approximation and approximate the potential energy surface with the superposition of the accurate potential along each normal mode. We show that the free energy can stabilize crystal structures at finite temperatures which appear dynamically unstable at T = 0. The DAMA formalism is computationally fast because it avoids statistical sampling through molecular dynamics calculations, and is in principle completely ab initio. It is free of statistical uncertainties and independent of model parameters, but can give insight into the mechanism of a structural phase transition. We apply the formalism to the perovskite cryolite, and investigate the temperature-driven phase transition from the P21/n to the Immm space group. We calculate a phase transition temperature between 710 and 950 K, in fair agreement with the experimental value of 885 K. This can be related to the underestimation of the interaction of the vibrational states. We also calculate the main axes of the thermal ellipsoid and can explain the experimentally observed increase of its volume for the fluorine by 200-300% throughout the phase transition. Our calculations suggest the appearance of tunneling states in the high temperature phase. The convergence of the vibrational DOS and of the critical temperature with respect of reciprocal space sampling is investigated using the polarizable-ion model. PMID:27269514
Insight into structural phase transitions from the decoupled anharmonic mode approximation
Adams, Donat J.; Passerone, Daniele
2016-08-01
We develop a formalism (decoupled anharmonic mode approximation, DAMA) that allows calculation of the vibrational free energy using density functional theory even for materials which exhibit negative curvature of the potential energy surface with respect to atomic displacements. We investigate vibrational modes beyond the harmonic approximation and approximate the potential energy surface with the superposition of the accurate potential along each normal mode. We show that the free energy can stabilize crystal structures at finite temperatures which appear dynamically unstable at T = 0. The DAMA formalism is computationally fast because it avoids statistical sampling through molecular dynamics calculations, and is in principle completely ab initio. It is free of statistical uncertainties and independent of model parameters, but can give insight into the mechanism of a structural phase transition. We apply the formalism to the perovskite cryolite, and investigate the temperature-driven phase transition from the P21/n to the Immm space group. We calculate a phase transition temperature between 710 and 950 K, in fair agreement with the experimental value of 885 K. This can be related to the underestimation of the interaction of the vibrational states. We also calculate the main axes of the thermal ellipsoid and can explain the experimentally observed increase of its volume for the fluorine by 200–300% throughout the phase transition. Our calculations suggest the appearance of tunneling states in the high temperature phase. The convergence of the vibrational DOS and of the critical temperature with respect of reciprocal space sampling is investigated using the polarizable-ion model.
The role of damping for the driven anharmonic quantum oscillator
Guo, Lingzhen; André, Stephan; Schön, Gerd
2011-01-01
For the model of a linearly driven quantum anharmonic oscillator, the role of damping is investigated. We compare the position of the stable points in phase space obtained from a classical analysis to the result of a quantum mechanical analysis. The solution of the full master equation shows that the stable points behave qualitatively similar to the classical solution but with small modifications. Both the quantum effects and additional effects of temperature can be described by renormalizing the damping.
Vibration signal models for fault diagnosis of planet bearings
Feng, Zhipeng; Ma, Haoqun; Zuo, Ming J.
2016-05-01
Rolling element bearings are key components of planetary gearboxes. Among them, the motion of planet bearings is very complex, encompassing spinning and revolution. Therefore, planet bearing vibrations are highly intricate and their fault characteristics are completely different from those of fixed-axis case, making planet bearing fault diagnosis a difficult topic. In order to address this issue, we derive the explicit equations for calculating the characteristic frequency of outer race, rolling element and inner race fault, considering the complex motion of planet bearings. We also develop the planet bearing vibration signal model for each fault case, considering the modulation effects of load zone passing, time-varying angle between the gear pair mesh and fault induced impact force, as well as the time-varying vibration transfer path. Based on the developed signal models, we derive the explicit equations of Fourier spectrum in each fault case, and summarize the vibration spectral characteristics respectively. The theoretical derivations are illustrated by numerical simulation, and further validated experimentally and all the three fault cases (i.e. outer race, rolling element and inner race localized fault) are diagnosed.
Nonlinear dynamic modeling and resonance tuning of Galfenol vibration absorbers
International Nuclear Information System (INIS)
This paper investigates the semi-active control of a magnetically-tunable vibration absorber’s resonance frequency. The vibration absorber that is considered is a metal-matrix composite containing the magnetostrictive material Galfenol (FeGa). A single degree of freedom model for the nonlinear vibration of the absorber is presented. The model is valid under arbitrary stress and magnetic field, and incorporates the variation in Galfenol’s elastic modulus throughout the composite as well as Galfenol’s asymmetric tension–compression behavior. Two boundary conditions—cantilevered and clamped–clamped—are imposed on the composite. The frequency response of the absorber to harmonic base excitation is calculated as a function of the operating conditions to determine the composite’s capacity for resonance tuning. The results show that nearly uniform controllability of the vibration absorber’s resonance frequency is possible below a threshold of the input power amplitude using weak magnetic fields of 0–8 kA m−1. Parametric studies are presented to characterize the effect on resonance tunability of Galfenol volume fraction and Galfenol location within the composite. The applicability of the results to composites of varying geometry and containing different Galfenol materials is discussed. (paper)
Modeling nonlinear random vibration: Implication of the energy conservation law
Sun, Xu; Duan, Jinqiao; Li, Xiaofan
2012-01-01
Nonlinear random vibration under excitations of both Gaussian and Poisson white noises is considered. The model is based on stochastic differential equations, and the corresponding stochastic integrals are defined in such a way that the energy conservation law is satisfied. It is shown that Stratonovich integral and Di Paola-Falsone integral should be used for excitations of Gaussian and Poisson white noises, respectively, in order for the model to satisfy the underlining physical laws (e.g.,...
Anharmonic resonances with recursive delay feedback
Goldobin, Denis S.
2011-01-01
We consider application of the multiple time delayed feedback for control of anharmonic (nonlinear) oscillators subject to noise. In contrast to the case of a single delay feedback, the multiple one exhibits resonances between feedback and nonlinear harmonics, leading to a resonantly strong or weak oscillation coherence even for a small anharmonicity. Analytical results are confirmed numerically for van der Pol and van der Pol-Duffing oscillators. Highlights: > We construct general theory of ...
Anharmonicity effects in the frictionlike mode of graphite
Menéndez, C.; Lobato, A.; Abbasi-Pérez, D.; Fernández-Núñez, J.; Baonza, V. G.; Recio, J. M.
2016-04-01
Graphite is a prototypical solid lubricant demanding a thorough understanding of its low-friction behavior. The E2 g(1) Raman active vibrational mode of graphite is associated with the rigid-layer relative movement of its graphene sheets. Thus, this mode can provide a good means of exploring the low resistance of graphene layers to slip with respect to each other. To take advantage of this fact, the anharmonicity of the E2 g(1) mode has to be carefully characterized and evaluated since the atomic arrangement of carbon atoms in the ambient condition ABA stacking of graphite evidences potential asymmetry. The calculated one-dimensional energetic profile of the E2 g(1) mode reveals this local anisotropy around the energy minima and can be microscopically interpreted in terms of electron density interactions. Morse-type potentials accurately fit the energetic profiles at different interlayer separations, and provide simple analytical expressions for evaluating harmonic and anharmonic contributions to the Γ -point E2 g(1) frequency ωE2g(1 ) under a perturbative algebraic treatment. We quantify how the anharmonic contribution increases with the available energy (E ) at zero pressure, and how this contribution decreases as hydrostatic pressure (p ) or uniaxial stress is applied for a given available energy. The calculated ωE2g(1 )-p and ωE2g(1 )-E trends indicate an increasing (decreasing) of frictional forces in graphite with pressure (temperature). Our conclusions are supported by the good agreement of the calculated frequencies with existing Raman experiments under hydrostatic pressure conditions.
Vibration analysis with MADYMO human models
Verver, M.M.; Hoof, J.F.A.M. van
2002-01-01
The importance of comfort for the automotive industry is increasing. Car manufacturers use comfort to distinguish their products from their competitors. However, the development and design of a new car seat or interior is very time consuming and expensive. The introduction of computer models of huma
Forced vibration test of the Hualien large scale SSI model
International Nuclear Information System (INIS)
A Large-Scale Seismic Test (LSST) Program has been conducted at Hualien, Taiwan (Tang et al., 1991), to obtain earthquake-induced soil-structure interaction (SSI) data in a stiff soil site environment The Hualien program is a follow on of the Lotung program which is of soft soil site. Forced vibration tests of the Hualien 1/4-scale containment SSI test model were conducted in October, 1992 before backfill (without embedment) and in February, 1993 after backfill (with embedment) for the purpose of defining basic dynamic characteristics of the soil-structure system. Two horizontal directions excitation (NS, EW) are applied on the roof floor and on the basemat. Vertical excitation is applied on the basemat only. This paper describes the results of the forced vibration tests of the model without embedment. (author)
Perturbation Theory of Anharmonicity Effects in Slow Neutron Inelastic Scattering by Crystals
International Nuclear Information System (INIS)
An earlier perturbation treatment of the corresponding X-ray scattering problem is generalized into a calculation of the effect of vibrational anharmonicity on the scattering of slow neutrons by crystals. Of an expansion of the lattice potential in powers of the deviations from the thermally averaged sites, the cubic terms are taken into account up to second order; only first order terms are kept in the quartic anharmonicities. All higher terms are neglected. In particular, formulae for the shifts and broadenings of the one-phonon peaks in coherent scattering are derived in terms of the third and fourth order coupling coefficients. As in X-ray scattering, a simple quadratic relation exists between the shifted ''effective frequencies'' of the long wavelength lattice vibrations and the isothermal elastic constants of the crystal. The lattice frequencies of the harmonic approximation may be obtained by extrapolating to absolute zero the linear dependence on temperature shown by the shifted frequencies above the Debye temperature. (author)
Vibration testing of a 1/4-scale containment model
International Nuclear Information System (INIS)
Both the U.S. Nuclear Regulatory Commission (USNRC) and the Electric Power Research Institute (EPRI) have undertaken programs to validate soil-structure interactions analysis methods with data that include ground and structural response motions during natural earthquakes and structural response motions from low level vibration tests. The primary source of the data is the 1/4-scale containment building situated in Lotung in a seismically active region of Taiwan. The analysis validation program involves blind predictions of site and structural responses to the vibration test excitations and to a selected strong-motion seismic event, and the subsequent comparison of these predictions with corresponding measurements. The details of these programs are described more fully elsewhere. The present paper focuses on the vibration testing of the model containment structure and the determination of its dynamic characteristics from the experimental data. The 1/4-scale reinforced concrete containment structure, built by EPRI in cooperation with Taiwan Power Company, is located within an array of strong-motion seismographs, known as the SMART-1 array. Figure 1 shows a cross section of the structure. The structure is not a replica model of a typical nuclear power plant containment building. The roof slab had to be made massive to ensure that the fundamental frequencies of the model structure would fall within the frequency range of seismic excitation typical for the site
Vibration signal models for fault diagnosis of planetary gearboxes
Feng, Zhipeng; Zuo, Ming J.
2012-10-01
A thorough understanding of the spectral structure of planetary gear system vibration signals is helpful to fault diagnosis of planetary gearboxes. Considering both the amplitude modulation and the frequency modulation effects due to gear damage and periodically time variant working condition, as well as the effect of vibration transfer path, signal models of gear damage for fault diagnosis of planetary gearboxes are given and the spectral characteristics are summarized in closed form. Meanwhile, explicit equations for calculating the characteristic frequency of local and distributed gear fault are deduced. The theoretical derivations are validated using both experimental and industrial signals. According to the theoretical basis derived, manually created local gear damage of different levels and naturally developed gear damage in a planetary gearbox can be detected and located.
Model reduction and analysis of a vibrating beam microgyroscope
Ghommem, Mehdi
2012-05-08
The present work is concerned with the nonlinear dynamic analysis of a vibrating beam microgyroscope composed of a rotating cantilever beam with a tip mass at its end. The rigid mass is coupled to two orthogonal electrodes in the drive and sense directions, which are attached to the rotating base. The microbeam is driven by an AC voltage in the drive direction, which induces vibrations in the orthogonal sense direction due to rotation about the microbeam axis. The electrode placed in the sense direction is used to measure the induced motions and extract the underlying angular speed. A reduced-order model of the gyroscope is developed using the method of multiple scales and used to examine its dynamic behavior. © The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Comprehensive modeling approach of axial ultrasonic vibration grinding force
Institute of Scientific and Technical Information of China (English)
HE Yu-hui; ZHOU Qun; ZHOU Jian-jie; LANG Xian-jun
2016-01-01
The theoretical model of axial ultrasonic vibration grinding force is built on the basis of a mathematical model of cutting deforming force deduced from the assumptions of thickness of the undeformed debris under Rayleigh distribution and a mathematical model of friction based on the theoretical analysis of relative sliding velocity of abrasive and workpiece. Then, the coefficients of the ultrasonic vibration grinding force model are calculated through analysis of nonlinear regression of the theoretical model by using MATLAB, and the law of influence of grinding depth, workpiece speed, frequency and amplitude of the mill on the grinding force is summarized after applying the model to analyze the ultrasonic grinding force. The result of the above-mentioned law shows that the grinding force decreases as frequency and amplitude increase, while increases as grinding depth and workpiece speed increase; the maximum relative error of prediction and experimental values of the normal grinding force is 11.47% and its average relative error is 5.41%; the maximum relative error of the tangential grinding force is 10.14% and its average relative error is 4.29%. The result of employing regression equation to predict ultrasonic grinding force approximates to the experimental data, therefore the accuracy and reliability of the model is verified.
Living systems as coherent anharmonic oscillators
International Nuclear Information System (INIS)
A model of living systems considered as coherent, time-dependent anharmonic oscillators is presented. It is based on the concept of space-like coherent states minimizing the time-energy uncertainty relation, adapted to the case of biological systems whose growth is described by the Gompertz or West-Brown-Enquist functions. The coherent states of biological growth evolve coherently in space being localized along the classical time trajectory; hence, the growth is predicted to be coherent in space. It is proven that the Gompertz function is a special solution of the space-like Horodecki-Feinberg equation for the time-dependent Morse oscillator in the dissociation state. Its eigenvalue represents the momentum of biological growth, associated with a space-like component whose properties resemble those attributed by vitalists to the life momentum or vital impulse. The physical characteristics of the life energy and momentum and their connection with the concept of zero-point momentum of vacuum are presented.
Model-based design approach to reducing mechanical vibrations
Directory of Open Access Journals (Sweden)
P. Czop
2013-09-01
Full Text Available Purpose: The paper presents a sensitivity analysis method based on a first-principle model in order to reduce mechanical vibrations of a hydraulic damper. Design/methodology/approach: The first-principle model is formulated using a system of continuous ordinary differential equations capturing usually nonlinear relations among variables of the hydraulic damper model. The model applies three categories of parameters: geometrical, physical and phenomenological. Geometrical and physical parameters are deduced from construction and operational documentation. The phenomenological parameters are the adjustable ones, which are estimated or adjusted based on their roughly known values, e.g. friction/damping coefficients. Findings: The sensitivity analysis method provides major contributors and their magnitude that cause vibrations Research limitations/implications: The method accuracy is limited by the model accuracy and inherited nonlinear effects. Practical implications: The proposed model-based sensitivity method can be used to optimize prototypes of hydraulic dampers. Originality/value: The proposed sensitivity-analysis method minimizes a risk that a hydraulic damper does not meet the customer specification.
Modeling and control of vibration in mechanical structures
Nauclér, Peter
2005-01-01
All mechanical systems exhibit vibrational response when exposed to external disturbances. In many engineering applications vibrations are undesirable and may even have harmful effects. Therefore, control of mechanical vibration is an important topic and extensive research has been going on in the field over the years. In active control of vibration, the ability to actuate the system in a controlled manner is incorporated into the structure. Sensors are used to measure the vibrations and seco...
Monitoring Vibration of A Model of Rotating Machine
Arko Djajadi; Arsi Azavi; Rusman Rusyadi; Erikson Sinaga
2012-01-01
Mechanical movement or motion of a rotating machine normally causes additional vibration. A vibration sensing device must be added to constantly monitor vibration level of the system having a rotating machine, since the vibration frequency and amplitude cannot be measured quantitatively by only sight or touch. If the vibration signals from the machine have a lot of noise, there are possibilities that the rotating machine has defects that can lead to failure. In this experimental research proj...
Bandshapes in vibrational spectroscopy
International Nuclear Information System (INIS)
A detailed account is given of the development of modern bandshape theories since 1965. An investigation into the relative contributions of statistical irreversible relaxation processes is described, for a series of molecules in which gradually the length of one molecular axis is increased. An investigation into the theoretical and experimental investigation of the broadening brought about by the effect of fluctuating intermolecular potentials on the vibrational frequency is also described. The effect of an intermolecular perturbative potential on anharmonic and Morse oscillators is discussed and the results are presented of a computation on the broadening of the vibrational band of some diatomic molecules in a rigid lattice type solvent. The broadening of the OH-stretching vibration in a number of aliphatic alcohols, the vibrational bandshapes of the acetylenic C-H stretching vibration and of the symmetric methyl stretching vibration are investigated. (Auth./ C.F.)
Errea, Ion; Calandra, Matteo; Pickard, Chris J.; Nelson, Joseph; Needs, Richard J.; Li, Yinwei; Liu, Hanyu; Zhang, Yunwei; Ma, Yanming; Mauri, Francesco
2015-04-01
We use first-principles calculations to study structural, vibrational, and superconducting properties of H2S at pressures P ≥200 GPa . The inclusion of zero-point energy leads to two different possible dissociations of H2S , namely 3 H2S →2 H3S +S and 5 H2S →3 H3S +HS2 , where both H3S and HS2 are metallic. For H3S , we perform nonperturbative calculations of anharmonic effects within the self-consistent harmonic approximation and show that the harmonic approximation strongly overestimates the electron-phonon interaction (λ ≈2.64 at 200 GPa) and Tc. Anharmonicity hardens H-S bond-stretching modes and softens H-S bond-bending modes. As a result, the electron-phonon coupling is suppressed by 30% (λ ≈1.84 at 200 GPa). Moreover, while at the harmonic level Tc decreases with increasing pressure, the inclusion of anharmonicity leads to a Tc that is almost independent of pressure. High-pressure hydrogen sulfide is a strongly anharmonic superconductor.
Errea, Ion; Calandra, Matteo; Pickard, Chris J; Nelson, Joseph; Needs, Richard J; Li, Yinwei; Liu, Hanyu; Zhang, Yunwei; Ma, Yanming; Mauri, Francesco
2015-04-17
We use first-principles calculations to study structural, vibrational, and superconducting properties of H_{2}S at pressures P≥200 GPa. The inclusion of zero-point energy leads to two different possible dissociations of H2S, namely 3H2S→2H3S+S and 5H2S→3H3S+HS2, where both H3S and HS2 are metallic. For H3S, we perform nonperturbative calculations of anharmonic effects within the self-consistent harmonic approximation and show that the harmonic approximation strongly overestimates the electron-phonon interaction (λ≈2.64 at 200 GPa) and Tc. Anharmonicity hardens H─S bond-stretching modes and softens H─S bond-bending modes. As a result, the electron-phonon coupling is suppressed by 30% (λ≈1.84 at 200 GPa). Moreover, while at the harmonic level Tc decreases with increasing pressure, the inclusion of anharmonicity leads to a Tc that is almost independent of pressure. High-pressure hydrogen sulfide is a strongly anharmonic superconductor. PMID:25933334
Interval process model and non-random vibration analysis
Jiang, C.; Ni, B. Y.; Liu, N. Y.; Han, X.; Liu, J.
2016-07-01
This paper develops an interval process model for time-varying or dynamic uncertainty analysis when information of the uncertain parameter is inadequate. By using the interval process model to describe a time-varying uncertain parameter, only its upper and lower bounds are required at each time point rather than its precise probability distribution, which is quite different from the traditional stochastic process model. A correlation function is defined for quantification of correlation between the uncertain-but-bounded variables at different times, and a matrix-decomposition-based method is presented to transform the original dependent interval process into an independent one for convenience of subsequent uncertainty analysis. More importantly, based on the interval process model, a non-random vibration analysis method is proposed for response computation of structures subjected to time-varying uncertain external excitations or loads. The structural dynamic responses thus can be derived in the form of upper and lower bounds, providing an important guidance for practical safety analysis and reliability design of structures. Finally, two numerical examples and one engineering application are investigated to demonstrate the feasibility of the interval process model and corresponding non-random vibration analysis method.
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.
The anharmonic effect study of coupled Morse oscillators for the unimolecular reaction
Institute of Scientific and Technical Information of China (English)
2008-01-01
The importance of anharmonic effect in dissociation of molecular systems especially clusters has been noted. In this paper, we shall study the effect of coupled anharmonic oscillator of the standard bilinear form (SBF) Morse oscillator (MO) potential on unimolecular reaction. We shall use the systematic theoretical approach, YL method, proposed by Yao and Lin (YAO L, et. al. J Phys Chem A, 2007, 111(29): 6722-6729), which can evaluate anharmonic effects on the rate constants based on the transition state theory. In treating the anharmonic effect with the Morse oscillator potential on unimolecular reactions under collision-free conditions by using the RRKM (Rice-Ramsperger-Kassel-Marcus) theory, the in-verse Laplace transformation of the partition functions was used to obtain the total amount of state and density of state by using the first-order and the second-order approximations of the saddle-point method. To demonstrate the anharmonic effect of the SBF Morse model, we choose some model systems and a real reaction as examples.
Impeller leakage flow modeling for mechanical vibration control
Palazzolo, Alan B.
1996-01-01
HPOTP and HPFTP vibration test results have exhibited transient and steady characteristics which may be due to impeller leakage path (ILP) related forces. For example, an axial shift in the rotor could suddenly change the ILP clearances and lengths yielding dynamic coefficient and subsequent vibration changes. ILP models are more complicated than conventional-single component-annular seal models due to their radial flow component (coriolis and centrifugal acceleration), complex geometry (axial/radial clearance coupling), internal boundary (transition) flow conditions between mechanical components along the ILP and longer length, requiring moment as well as force coefficients. Flow coupling between mechanical components results from mass and energy conservation applied at their interfaces. Typical components along the ILP include an inlet seal, curved shroud, and an exit seal, which may be a stepped labyrinth type. Von Pragenau (MSFC) has modeled labyrinth seals as a series of plain annular seals for leakage and dynamic coefficient prediction. These multi-tooth components increase the total number of 'flow coupled' components in the ILP. Childs developed an analysis for an ILP consisting of a single, constant clearance shroud with an exit seal represented by a lumped flow-loss coefficient. This same geometry was later extended to include compressible flow. The objective of the current work is to: supply ILP leakage-force impedance-dynamic coefficient modeling software to MSFC engineers, base on incompressible/compressible bulk flow theory; design the software to model a generic geometry ILP described by a series of components lying along an arbitrarily directed path; validate the software by comparison to available test data, CFD and bulk models; and develop a hybrid CFD-bulk flow model of an ILP to improve modeling accuracy within practical run time constraints.
Scattering of Neutrons by an Anharmonic Crystal
International Nuclear Information System (INIS)
Numerical calculations have been performed for the anharmonic effects in neutron scattering. The phonon frequency widths and shifts have been calculated as a function of neutron frequency at different wave numbers and temperatures for a potential with central symmetry and for a face-centered cubic lattice
Modeling of Axial Spring Stiffness in Active Vibration Controlled Drilling
Pao William; Hashim Fakhruldin M; Parman Setyamartana
2014-01-01
During drilling process, substantial amount of vibration and shock are induced to the drill string. Active vibration controlled drilling is introduced to reduce the vibration and increase the efficiency of drilling process. In this system, two main components that determine the damping coefficient are magnetorheological (MR) damper and spring assembly. Performance of vibration damping system is depending on the viscosity of MR fluid in the damper and spring constant of spring assembly. One of...
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...
Tian, Jialin; Wu, Chunming; Yang, Lin; Yang, Zhi; Liu, Gang; Yuan, Changfu
2016-01-01
Comparative analysis whether considering the lateral inertia or not, aiming at the longitudinal vibration of the drill string in drilling progress, is proposed. In the light of the actual condition, the mechanical model of the drill string about vibration is established on the basis of the theoretical analysis. Longitudinal vibration equation of the drill string is derived from the Rayleigh-Love model and one-dimensional viscoelastic model. According to the Laplace transform method and the re...
On the Elastic Vibration Model for High Length-Diameter Ratio Rocket with Attitude Control System
Institute of Scientific and Technical Information of China (English)
朱伯立; 杨树兴
2003-01-01
An elastic vibration model for high length-diameter ratio spinning rocket with attitude control system which can be used for trajectory simulation is established. The basic theory of elastic dynamics and vibration dynamics were both used to set up the elastic vibration model of rocket body. In order to study the problem more conveniently, the rocket's body was simplified to be an even beam with two free ends. The model was validated by simulation results and the test data.
Modelling nuclear fuel vibrations in horizontal CANDU reactors
International Nuclear Information System (INIS)
Flow-induced fuel vibrations in the pressure tubes of CANDU reactors are of vital interest to designers because fretting damage may result. Computer simulation is being used to study how bundles vibrate and to identify bundle design features which will reduce vibration and hence fretting. (author)
The results of experimental investigations on tube vibration of model BN-1200 steam generator
International Nuclear Information System (INIS)
Self and forced vibrations of 61-tube model of BN-1200 steam generator are studied as well as the effect of the design and operational factors on vibrational response of heat-exchanging tubes (HET). It is stated that vibrations on the frequencies near to self ones give the main contribution into total vibration level of HET in the coolant flow. The maximal of vibration level of HET is determined in the area of coolant input into the model. In the area of longitudinal flow and in the area of coolant output the level of vibrational accelerations of HET is less by several times. It is pointed out that with flow rate increase vibration level of different HET in the input area grows according to the law from linear to quadratic
Design of CAP1400 reactor internals flow-induced vibration simulation test model
International Nuclear Information System (INIS)
While the first CAP1400 reactor internals is defined as a 'prototype', it is necessary to carry out the reactor internals flow-induced vibration simulation test for verifying the structure integrity of reactor internals and providing data for vibration assessment of CAP1400 reactor internals. The reactor internals flow-induced vibration simulation test is usually a reduced scale model test. This paper describes in detail the main factors of model scale, similarity criterion and the simplification of test model. The simplification of model will not only reduce the fabrication cost, but also obtain more accurate test data from the flow-induced vibration simulation test. (authors)
International Nuclear Information System (INIS)
The angular distribution of the elastic and inelastic scattering of a particles corresponding to the excitation of the low-lying collective states of 142Ce were measured at an incident energy of 18.0 MeV. The angular distribution of the following excited states were obtained: 641, 1.219, 1.450, 1.536, 1.653, 1.742, 2.004, 2.043, 2.114, 2.125, 2.279, 2.364, 2.542, 2.604 e 3.067 MeV. The angular distributions of the ground state and the first six excited states were analysed within the flamework of the Anharmonic Vibrational and Symmetric Rotational Models, with the Coupled Channel Theory. The Anharmonic Vibrational Model gave the best and most complete description of the experimental data. The wave functions and the deformation parameters of the analysed states were determined. (Author)
Vibration modeling of structural fuzzy with continuous boundary
DEFF Research Database (Denmark)
Friis, Lars; Ohlrich, Mogens
2008-01-01
From experiments it is well known that the vibration response of a main structure with many attached substructures often shows more damping than structural losses in the components can account for. In practice, these substructures, which are not attached in an entirely rigid manner, behave like a...... multitude of different sprung masses each strongly resisting any motion of the main structure (master) at their base antiresonance. The “theory of structural fuzzy” is intended for modeling such high damping. In the present article the theory of fuzzy structures is briefly outlined and a method of modeling...... effect of the fuzzy with spatial memory is demonstrated by numerical simulations of a main beam structure with fuzzy attachments. It is shown that the introduction of spatial memory reduces the damping effect of the fuzzy and in certain cases the damping effect may even be eliminated completely....
Electrons in anharmonic phonon fields of low-dimensional high-Tc superconductors
International Nuclear Information System (INIS)
A general mathematical formulation is developed for calculating the electron response function of layered superconductors. A model Hamiltonian for the low-dimensional superconducting system is developed which includes (i) bare electron interactions, (ii) harmonic phonon fields, (iii) electron-phonon interactions, (iv) anharmonic phonons and (v) effects of localized phonon fields. Quantum dynamics of electrons is studied adopting the Green's function theory via this advanced Hamiltonian in order to describe the many-body problem. This work remarkably describes that the electron-phonon coupling coefficient shows its inevitable presence in all sectors of phonon fields, namely, the fields of (i) anharmonic phonons (ii) localized phonons and (iii) the impurity-anharmonicity interaction. The expressions for electron density of states and electron heat capacity are also obtained in the new framework. (orig.)
International Nuclear Information System (INIS)
Interaction energies, molecular structure and vibrational frequencies of the binary complex formed between H(D)Cl and dimethyl ether have been obtained using quantum-chemical methods. Equilibrium and vibrationally averaged structures, harmonic and anharmonic wavenumbers of the complex and its deuterated isotopomer were calculated using harmonic and anharmonic second-order perturbation theory procedures with Density Functional Theory B3LYP and B2PLYP-D and ab initio Møller-Plesset second-order methods, and a 6-311++G(3d,3p) basis set. A phenomenological model describing anharmonic-type vibrational couplings within hydrogen bonds was developed to explain the unique broadening and fine structure, as well as the isotope effect of the Cl–H and Cl–D stretching IR absorption bands in the gaseous complexes with dimethyl ether, as an effect of hydrogen bond formation. Simulations of the rovibrational structure of the Cl–H and Cl–D stretching bands were performed and the results were compared with experimental spectra
Energy Technology Data Exchange (ETDEWEB)
Boda, Łukasz, E-mail: lboda@chemia.uj.edu.pl; Boczar, Marek; Gług, Maciej; Wójcik, Marek J. [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków (Poland)
2015-11-28
Interaction energies, molecular structure and vibrational frequencies of the binary complex formed between H(D)Cl and dimethyl ether have been obtained using quantum-chemical methods. Equilibrium and vibrationally averaged structures, harmonic and anharmonic wavenumbers of the complex and its deuterated isotopomer were calculated using harmonic and anharmonic second-order perturbation theory procedures with Density Functional Theory B3LYP and B2PLYP-D and ab initio Møller-Plesset second-order methods, and a 6-311++G(3d,3p) basis set. A phenomenological model describing anharmonic-type vibrational couplings within hydrogen bonds was developed to explain the unique broadening and fine structure, as well as the isotope effect of the Cl–H and Cl–D stretching IR absorption bands in the gaseous complexes with dimethyl ether, as an effect of hydrogen bond formation. Simulations of the rovibrational structure of the Cl–H and Cl–D stretching bands were performed and the results were compared with experimental spectra.
Allen, Philip B.
2015-08-01
The quasiharmonic (QH) approximation uses harmonic vibrational frequencies ωQ ,H(V ) computed at volumes V near V0 where the Born-Oppenheimer (BO) energy Eel(V ) is minimum. When this is used in the harmonic free energy, QH approximation gives a good zeroth order theory of thermal expansion and first-order theory of bulk modulus, where nth-order means smaller than the leading term by ɛn, where ɛ =ℏ ωvib/Eel or kBT /Eel , and Eel is an electronic energy scale, typically 2 to 10 eV. Experiment often shows evidence for next-order corrections. When such corrections are needed, anharmonic interactions must be included. The most accessible measure of anharmonicity is the quasiparticle (QP) energy ωQ(V ,T ) seen experimentally by vibrational spectroscopy. However, this cannot just be inserted into the harmonic free energy FH. In this paper, a free energy is found that corrects the double-counting of anharmonic interactions that is made when F is approximated by FH( ωQ(V ,T ) ) . The term "QP thermodynamics" is used for this way of treating anharmonicity. It enables (n +1 ) -order corrections if QH theory is accurate to order n . This procedure is used to give corrections to the specific heat and volume thermal expansion. The QH formulas for isothermal (BT) and adiabatic (BS) bulk moduli are clarified, and the route to higher-order corrections is indicated.
1/N-expansion and nonclassical state generation in higher-order anharmonic oscillators
Alekseev, K N; Perina, J; Alekseev, Kirill N.; Alekseeva, Natasha V.; Perina, Jan
1998-01-01
We consider the nonclassical states generation in weakly dissipative high-order anharmonic oscillators in the limit of large number of photons. We find the explicit time dependences of squeezing and Fano factor in the short-time approximation and for a finite temperature of reservoir. We show that the rate of squeezing is determined by an interplay between the polarization of the nonlinear medium modelled by the anharmonic oscillator and the thermal fluctuations of a reservoir. We demonstrate that photon statistics is super-Poissonian for any degree of the nonlinearity and determine the critical temperature of reservoir destroying light squeezing.
Crystal anharmonicity in Li(H,D) and Na(H,D) systems
International Nuclear Information System (INIS)
The reliability of our recently developed potential model is tested by extending the study to various anharmonic properties, e.g., third order elastic constants, fourth order elastic constants, Grueneisen parameters, and the pressure derivatives of second order elastic constants of hydrides and deuterides of lithium and sodium. A comparison of the calculated properties with the available experimental results and other theoretical estimates shows the validity and reliability of the derived potential in the study of crystal anharmonicities also. (author). 43 refs, 2 figs, 4 tabs
Anharmonicities and non-linearities in the excitation of double giant resonances
International Nuclear Information System (INIS)
The non-linear response of a quantum anharmonic oscillator is investigated as a model for the excitation of giant resonances in heavy ion collisions. It is shown that the introduction of small anharmonicities and non-linearities can double the predicted cross section for the excitation of the two-phonon states. These findings suggest that such ingredients must be included in future more complete calculations in order to reduce the huge discrepancy between the previous theoretical predictions and the experimental cross section of double giant resonance states. (author)
Vibrational exciton-mediated quantum state transfert: a simple model
Pouthier, Vincent J C
2012-01-01
A communication protocol is proposed in which quantum state transfer is mediated by a vibrational exciton. We consider two distant molecular groups grafted on the sides of a lattice. These groups behave as two quantum computers where the information in encoded and received. The lattice plays the role of a communication channel along which the exciton propagates and interacts with a phonon bath. Special attention is paid for describing the system involving an exciton dressed by a single phonon mode. The Hamiltonian is thus solved exactly so that the relevance of the perturbation theory is checked. Within the nonadiabatic weak-coupling limit, it is shown that the system supports three quasi-degenerate states that define the relevant paths followed by the exciton to tunnel between the computers. When the model parameters are judiciously chosen, constructive interferences take place between these paths. Phonon-induced decoherence is minimized and a high-fidelity quantum state transfer occurs over a broad temperat...
Forced vibration tests of a model foundation on rock ground
International Nuclear Information System (INIS)
The response of very stiff structures, such as nuclear reactor buildings, to earthquake ground motion is significantly affected by radiation damping due to the soil-structure interaction. The radiation damping can be computed by vibration admittance theory or dynamical ground compliance theory. In order to apply the values derived from these theories to the practical problems, comparative studies between theoretical results and experimental results concerning the soil-structure interaction, especially if the ground is rock, are urgently needed. However, experimental results for rock are less easily obtained than theoretical ones. The purpose of this paper is to describe the harmonic excitation tests of a model foundation on rock and to describe the results of comparative studies. (orig./HP)
A Spin Glass Model with Vibrations of Crystal Lattices
Institute of Scientific and Technical Information of China (English)
SHANG Yu-Min; CHENG Li-Min; YAO Kai-Lun
2005-01-01
@@ With the help of the replica method and imaginary-time functional-integrate technique, the spin glas s model with the vibrations of crystal lattices is investigated. In the limit of the replica symmetry and the imaginary-time staticapproximation, the magnetic and thermodynamic quantities have been obtained. By the numerical calculations,we found that the magnetization of the system has the typical spin-glass behaviour. A peak is found in the susceptibility-temperature curve and is shifted to lower temperature with increasing applied field. Due to the lattice contribution, the specific heat increas es strongly at high temperature. Due to the magnetic contribution,the anomaly in the specific heat-temperature curve forms a λ-type peak, which agrees with the observation ofRojo et al. [Phys. Rev. B 66 (2002) 094406].
Nonlinear Models for Transverse Forced Vibration of Axially Moving Viscoelastic Beams
Directory of Open Access Journals (Sweden)
Hu Ding
2011-01-01
Full Text Available Nonlinear models of transverse vibration of axially moving viscoelastic beams subjected external transverse loads via steady-state periodical response are numerically investigated. An integro-partial-differential equation and a partial-differential equation of transverse motion can be derived respectively from a model of the coupled planar vibration for an axially moving beam. The finite difference scheme is developed to calculate steady-state response for the model of coupled planar and the two models of transverse motion under the simple support boundary. Numerical results indicate that the amplitude of the steady-state response for the model of coupled vibration and two models of transverse vibration predict qualitatively the same tendencies with the changing parameters and the integro-partial-differential equation gives results more closely to the coupled planar vibration.
Torsional Vibrations at Guide-Vane Shaft of Pump–Turbine Model
Directory of Open Access Journals (Sweden)
Andrej Predin
1997-01-01
Full Text Available This article focuses on the problem of guide-vane vibrations of reversible pump–turbines, especially, in the pump mode. These vibrations are transmitted to the guide-vane shaft torque. The guide-vane vibrations are caused by the impeller exit flow, which has a turbulent and partly nondeterministic property. Experimentally determined flow velocities at the impeller exit are given. The mathematical models for theoretical torsional vibration prediction formulated using linear and nonlinear differential equations are presented. The results of theoretical calculations are compared with measurement results. The possibility of transferring the parameters from the model to the prototype is discussed.
ANALYSIS AND MODELLING OF BIODYNAMIC RESPONSE TO HAND ARM VIBRATION SYSTEM
Directory of Open Access Journals (Sweden)
Mohod Chandrashekhar D
2016-01-01
Full Text Available Hand operated tools are widely used in industrial and commercial sector. These tools generate vibrations which have impact on health of an operator. Hence study of Hand Vibration Syndrome is one of the key areas where major researchers are attracted. This study considers the literature review for hand operated vibration measurement and analysis that are extensively used. Objective of this review was to understand results and effects of hand vibration transmission on health. The review could be used to develop a prediction model with use of Adaptive Neuro Fuzzy Inference System hence another objective is to represent the applicability of ANFIS in development of the model
Modelling and Analysis of Vibrations in a UAV Helicopter with a Vision System
G. Nicolás Marichal Plasencia; María Tomás Rodríguez; Salvador Castillo Rivera; Ángela Hernández López
2012-01-01
The analysis of the nature and damping of unwanted vibrations on Unmanned Aerial Vehicle (UAV) helicopters are important tasks when images from on‐board vision systems are to be obtained. In this article, the authors model a UAV system, generate a range of vibrations originating in the main rotor and design a control methodology in order to damp these vibrations. The UAV is modelled using VehicleSim, the vibrations that appear on the fuselage are analysed to study their effects on the on‐boar...
Quantum anharmonic oscillator: The airy function approach
Energy Technology Data Exchange (ETDEWEB)
Maiz, F., E-mail: fethimaiz@gmail.com [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia); University of Cartage, Nabeul Engineering Preparatory Institute, Merazka, 8000 Nabeul (Tunisia); AlFaify, S. [King Khalid University, Faculty of Science, Physics Department, PO Box 9004, Abha 61413, Asseer (Saudi Arabia)
2014-05-15
New and simple numerical method is being reported to solve anharmonic oscillator problems. The method is setup to approach the real potential V(x) of the anharmonic oscillator system as a piecewise linear potential u(x) and to solve the Schrödinger equation of the system using the Airy function. Then, solutions continuity conditions lead to the energy quantification condition, and consequently, the energy eigenvalues. For testing purpose, the method was applied on the sextic and octic oscillators systems. The proposed method is found to be realistic, computationally simple, and having high degrees of accuracy. In addition, it can be applied to any form of potential. The results obtained by the proposed method were seen closely agreeing with results reached by other complicated methods.
Anharmonic oscillations of a conical buoy
Oliveira, J Brochado; da Silva, J M Machado
2011-01-01
A study of the foating of a circular cone shaped buoy in an ideal fluid has revealed some new interesting results. Using reduced variables it is shown, that at a crossover value (3/4) of the ratio of the specific masses of the fluid and of the buoy, the anharmonicity of the oscillation is the highest and that, unexpectedly, above this crossover value the normalized period is constant.
Two-phase CFD modeling of flow causing the heater vibration
International Nuclear Information System (INIS)
Vibrations of heater rods were observed in a heated annulus with water flow under boiling conditions. In order to find out the cause of such vibrations, CFD model of this annulus has been prepared in CFD code STAR-CCM+. Two-phase flow in the annulus was described using a two-fluid model with number of sub-models to describe the mass, momentum and energy transfer between phases. The model was validated using experimental data from reference. The validated model was used to perform a steady state calculation of flow parameters under different conditions. Results of CFD simulations were compared to experimentally detected vibration offset. It was found out that vibration increase caused by heating the channel is connected with the vibration offset. The results and their extension to nuclear safety were discussed. (author)
Aerodynamic and structural modeling for vortex-excited vibrations in bundled conductors
Verma, Himanshu
2009-01-01
Wind excited vibrations generated by the vortex shedding are very common in high-voltage overhead transmission lines. Although such vibrations are barely perceptible due to their low amplitudes (less than a conductor diameter), controlling them, however, is extremely important since they may lead to conductor fatigue. Mathematical models are therefore necessary for the computation of these vibrations, not only to evaluate the risk of potential damage to the transmission line but also for stud...
Modelling of vibrational optical activity of fibrillar systems
Czech Academy of Sciences Publication Activity Database
Kessler, Jiří; Kapitán, J.; Yamamoto, S.; Kiederling, T. A.; Bouř, Petr
Vienna : Vienna University of Technology, 2015 - (Lendl, B.; Koch, C.; Kraft, M.; Ofner, J.; Ramer, G.). s. 504-505 ISBN 978-3-200-04205-6. [ICAVS8. International Conference on Advanced Vibrational Spectroscopy /8./. 12.07.2015-17.07.2015, Vienna] Institutional support: RVO:61388963 Keywords : vibrational optical activity * proteins * fibrills Subject RIV: CF - Physical ; Theoretical Chemistry
International Nuclear Information System (INIS)
No suitable handy tool is available to predict train-induced vibration on environmental impact assessment. A simple prediction model is proposed which has been calibrated for high speed trains. The model input data are train characteristics, train speed and track properties; model output data are soil time-averaged velocity and velocity level. Model results have been compared with numerous vibration data retrieved from measurement campaigns led along the most important high-speed European rail tracks. Model performances have been tested by comparing measured and predicted vibration values
Hernández-Rojas, Javier; Calvo, Florent; Noya, Eva Gonzalez
2015-03-10
The semiclassical method of quantum thermal baths by colored noise thermostats has been used to simulate various atomic systems in the molecular and bulk limits, at finite temperature and in moderately to strongly anharmonic regimes. In all cases, the method performs relatively well against alternative approaches in predicting correct energetic properties, including in the presence of phase changes, provided that vibrational delocalization is not too strong-neon appearing already as an upper limiting case. In contrast, the dynamical behavior inferred from global indicators such as the root-mean-square bond length fluctuation index or the vibrational spectrum reveals more marked differences caused by zero-point energy leakage, except in the case of isolated molecules with well separated vibrational modes. To correct for such deficiencies and reduce the undesired transfer among modes, empirical modifications of the noise power spectral density were attempted to better describe thermal equilibrium but still failed when used as semiclassical preparation for microcanonical trajectories. PMID:26579740
Vibrations of liquid drops in film boiling phenomena: the mathematical model
Casal, Pierre
2008-01-01
Flattened liquid drops poured on a very hot surface evaporate quite slowly and float on a film of their own vapour. In the cavities of a surface, an unusual type of vibrational motions occurs. Large vibrations take place and different forms of dynamic drops are possible. They form elliptic patterns with two lobes or hypotrochoid patterns with three lobes or more. The lobes are turning relatively to the hot surface. We present a model of vibrating motions of the drops. Frequencies of the vibrations are calculated regarding the number of lobes. The computations agree with experiments.
Modeling of metallic surface topography modification by high-frequency vibration
Yao, Zhehe; Mei, Deqing; Chen, Zichen
2016-02-01
High-frequency vibration is capable of modifying metallic surface topography significantly, while the underlying mechanisms are still unclear. In this study, the acoustic softening effect is considered to explain and model the effects of high-frequency normal vibration on surface topography. The surface asperities can be softened by the high-frequency vibration due to acoustic softening, leading to the enhancement of surface topography modification. A theoretical model for metallic surface topography modification by high-frequency vibration is proposed based on the acoustic plasticity. Numerical predictions of surface roughness evolution were conducted under various working conditions based on the model developed. It was found that the reduction of surface roughness (RSR) after vibration-assisted forming was affected by static stress, vibration amplitude, material properties and initial specimen surface roughness. The predictions using the developed model were compared with experimental data. Results showed that the predicted RSR agreed well with the experimental results, indicating that the analytical model is able to accurately capture surface topography evolution during vibration-assisted metal forming. This study provides a basis for understanding the underlying mechanisms of surface topography modification in vibration-assisted manufacturing.
Quadrupole and monopole large amplitude vibrations
International Nuclear Information System (INIS)
A set of nonlinear dynamical equations for quadrupole and monopole moments of nuclei is derived from the TDHF equation with the help of the so-called Wigner function moments. It allows the description of coupled large amplitude monopole and quadrupole vibrations. These equations are solved numerically for 208Pb and 40Ca in a model with separable forces. The giant quadrupole and monopole resonances are reproduced very well. However the essential feature of the large amplitude motion is the existence of multiphonon states. They are analyzed in detail. The classical and quantum aspects of the analytically solvable one-dimensional pure monopole model are studied to clarify the problem of the anharmonicity of the collective spectrum. 26 refs., 2 figs., 2 tabs
Implementation of a vibrationally linked chemical reaction model for DSMC
Carlson, A. B.; Bird, Graeme A.
1994-01-01
A new procedure closely linking dissociation and exchange reactions in air to the vibrational levels of the diatomic molecules has been implemented in both one- and two-dimensional versions of Direct Simulation Monte Carlo (DSMC) programs. The previous modeling of chemical reactions with DSMC was based on the continuum reaction rates for the various possible reactions. The new method is more closely related to the actual physics of dissociation and is more appropriate to the particle nature of DSMC. Two cases are presented: the relaxation to equilibrium of undissociated air initially at 10,000 K, and the axisymmetric calculation of shuttle forebody heating during reentry at 92.35 km and 7500 m/s. Although reaction rates are not used in determining the dissociations or exchange reactions, the new method produces rates which agree astonishingly well with the published rates derived from experiment. The results for gas properties and surface properties also agree well with the results produced by earlier DSMC models, equilibrium air calculations, and experiment.
Vibration modeling of structural fuzzy with continuous boundary.
Friis, Lars; Ohlrich, Mogens
2008-02-01
From experiments it is well known that the vibration response of a main structure with many attached substructures often shows more damping than structural losses in the components can account for. In practice, these substructures, which are not attached in an entirely rigid manner, behave like a multitude of different sprung masses each strongly resisting any motion of the main structure (master) at their base antiresonance. The "theory of structural fuzzy" is intended for modeling such high damping. In the present article the theory of fuzzy structures is briefly outlined and a method of modeling fuzzy substructures examined. This is done by new derivations and physical interpretations are provided. Further, the method is extended and simplified by introducing a simple deterministic approach to determine the boundary impedance of the structural fuzzy. By using this new approach, the damping effect of the fuzzy with spatial memory is demonstrated by numerical simulations of a main beam structure with fuzzy attachments. It is shown that the introduction of spatial memory reduces the damping effect of the fuzzy and in certain cases the damping effect may even be eliminated completely. PMID:18247876
Accurate ab initio anharmonic force field and heat of formation for silane, $SiH_{4}$
Martin, J M L; Lee, T J; Martin, Jan M.L.; Baldridge, Kim K.; Lee, Timothy J.
1999-01-01
From large basis set coupled cluster calculations and a minor empirical adjustment, an anharmonic force field for silane has been derived that is consistently of spectroscopic quality ($\\pm 1 cm^{-1}$ on vibrational fundamentals) for all isotopomers of silane studied. Inner-shell polarization functions have an appreciable effect on computed properties and even on anharmonic corrections. From large basis set coupled cluster calculations and extrapolations to the infinite-basis set limit, we obtain TAE_0=303.80 \\pm 0.18 kcal/mol, which includes an anharmonic zero-point energy (19.59 kcal/mol), inner-shell correlation (-0.36 kcal/mol), scalar relativistic corrections (-0.70 kcal/mol), and atomic spin-orbit corrections (-0.43 kcal/mol). In combination with the recently revised \\HVSI{0}, we obtain $\\Delta H^{\\circ}_{f,0}[SiH_4(g)]=9.9 \\pm 0.4 kcal/mol$, in between the two established experimental values.
Active control of structural vibration with on-line secondary path modeling
Institute of Scientific and Technical Information of China (English)
YANG Tiejun; GU Zhongquan
2004-01-01
An active control strategy with on-line secondary path modeling is proposed and applied in active control of helicopter structural vibration. Computer simulations of the secondary path modeling performance demonstrate the superiorities of the active control strategy. A 2-input 4-output active control simulation for a helicopter model is performed and great reduction of structural vibration is achieved. 2-input 2-output and 2-input 4-output experimental studies of structural vibration control for a free-free beam are also carried out in laboratory to simulate a flying helicopter. The experimental results also show better reduction of the structural vibration, which verifies that the proposed method is effective and practical in structural vibration reduction.
Directory of Open Access Journals (Sweden)
Peng Guo
2012-12-01
Full Text Available With appropriate vibration modeling and analysis the incipient failure of key components such as the tower, drive train and rotor of a large wind turbine can be detected. In this paper, the Nonlinear State Estimation Technique (NSET has been applied to model turbine tower vibration to good effect, providing an understanding of the tower vibration dynamic characteristics and the main factors influencing these. The developed tower vibration model comprises two different parts: a sub-model used for below rated wind speed; and another for above rated wind speed. Supervisory control and data acquisition system (SCADA data from a single wind turbine collected from March to April 2006 is used in the modeling. Model validation has been subsequently undertaken and is presented. This research has demonstrated the effectiveness of the NSET approach to tower vibration; in particular its conceptual simplicity, clear physical interpretation and high accuracy. The developed and validated tower vibration model was then used to successfully detect blade angle asymmetry that is a common fault that should be remedied promptly to improve turbine performance and limit fatigue damage. The work also shows that condition monitoring is improved significantly if the information from the vibration signals is complemented by analysis of other relevant SCADA data such as power performance, wind speed, and rotor loads.
Vibration measurements of a wire scanner - Experimental setup and models
Herranz, Juan; Barjau, Ana; Dehning, Bernd
2016-03-01
In the next years the luminosity of the LHC will be significantly increased. This will require a much higher accuracy of beam profile measurement than actually achievable by the current wire scanner. The new performance demands a wire travelling speed up to 20 m s-1 and a position measurement accuracy of the order of 1 μm. The vibrations of the mechanical parts of the system and particularly the vibrations of the thin carbon wire have been identified as the major error sources of wire position uncertainty. Therefore the understanding of the wire vibrations has been given high priority for the design and operation of the new device. This article presents a new strategy to measure the wire vibrations based on the piezoresistive effect of the wire itself. An electronic readout system based on a Wheatstone bridge is used to measure the variation of the carbon wire resistance, which is directly proportional to the wire elongation caused by the oscillations.
The theoretical modeling and monitoring of WWER fuel assembly vibrations under operating conditions
International Nuclear Information System (INIS)
A configuration of a fuel assembly (FA) vibration monitoring system is proposed in the paper. The vibration monitoring of the fuel assembly (FA) is the main experimental support during the processes of FA design, FA commissioning and FA commercial operation. Such monitoring is addressed to define the limits for hydrodynamic loadings of the FA and to estimate the characteristics of FA dynamic response. The last should include the estimation of vibration both FA and internal as a whole, because the oscillations of the FA and internals have interdependent nature and in many respects are determined by an actual conditions of support structures. The paper also presents a flow chart of the FA vibration analysis including internal relations and feedbacks as well as a configuration of FA vibration monitoring system. The necessity of the theoretical modeling of fuel vibration characteristics is discussed and used for interpretation of the monitoring results related to the probable abnormal vibrational conditions. Some results of vibration-noise measurements of WWER-440 fuel assemblies as an example of vibration monitoring system application are also given in this work
Modelling flow-induced vibrations of gates in hydraulic structures
Erdbrink, C.D.
2014-01-01
The dynamic behaviour of gates in hydraulic structures caused by passing flow poses a potential threat to flood protection. Complex interactions between the turbulent flow and the suspended gate body may induce undesired vibrations. This thesis contributes to a better understanding and prevention of gate vibrations by employing a variety of computational approaches. Simulations with the finite-element method are used to analyse the fluid-structure interaction of a new underflow gate type whic...
Non-linear model of a ball vibration absorber
Czech Academy of Sciences Publication Activity Database
Náprstek, Jiří; Fischer, Cyril; Pirner, Miroš; Fischer, Ondřej
Vol. 2. Dordrecht : Springer, 2013 - (Papadrakakis, M.; Fragiadakis, M.; Plevris, V.), s. 381-396 ISBN 978-94-007-6572-6. - (Computational Methods in Applied Sciences. 30) R&D Projects: GA ČR(CZ) GA103/09/0094; GA AV ČR(CZ) IAA200710902; GA AV ČR(CZ) IAA200710805 Institutional support: RVO:68378297 Keywords : vibration ball absorber * dynamic stability * nonlinear vibration Subject RIV: JM - Building Engineering
Lei, Yaguo; Liu, Zongyao; Lin, Jing; Lu, Fanbo
2016-05-01
Condition monitoring and fault diagnosis of epicyclic gearboxes using vibration signals are not as straightforward as that of fixed-axis gearboxes since epicyclic gearboxes behave quite differently from fixed-axis gearboxes in many aspects, like spectral structures. Aiming to present the spectral structures of vibration signals of epicyclic gearboxes, phenomenological models of vibration signals of epicyclic gearboxes are developed by algebraic equations and spectral structures of these models are deduced using Fourier series analysis. In the phenomenological models, all the possible vibration transfer paths from gear meshing points to a fixed transducer and the effects of angular shifts of planet gears on the spectral structures are considered. Accordingly, time-varying vibration transfer paths from sun-planet/ring-planet gear meshing points to the fixed transducer due to carrier rotation are given by window functions with different amplitudes. And an angular shift in one planet gear position is introduced in the process of modeling. After the theoretical derivations, three experiments are conducted on an epicyclic gearbox test rig and the spectral structures of collected vibration signals are analyzed. As a result, the effects of angular shifts of planet gears are verified, and the phenomenological models of vibration signals when a local fault occurs on the sun gear and the planet gear are validated, respectively. The experiment results demonstrate that the established phenomenological models in this paper are helpful to the condition monitoring and fault diagnosis of epicyclic gearboxes.
Equivalent linearization technique for quantum anharmonic oscillators
International Nuclear Information System (INIS)
Quantum dynamics means studying the evolution of an initially prescribed wave function. This is analytically tractable for special wavefunctions for the simplest of the situations—free particle and simple harmonic oscillator. The purely anharmonic oscillators are virtually impossible to handle. We show here that the study of Ehrenfest's equation provides an alternative route to studying quantum dynamics. It does not give exact answers but clarifies some basic aspects of quantum dynamics by providing a prescription for constructing equivalent simple harmonic oscillators. (paper)
A microscopic nuclear collective rotation-vibration model: 2D submodel
Gulshani, Parviz
2016-01-01
The previous microscopic collective rotation-vibration model is improved to include interaction between collective oscillations in a pair of spatial directions, and to remove many of the previous-model approximations. As in the previous model, the nuclear Schrodinger equation (instead of the Hamiltonian) is canonically transformed to obtain a Schrodinger equation for collective rotation and vibration of a nucleus coupled to an intrinsic motion, with the related constraints imposed on the wave...
Quantum dissipative effect of one dimension coupled anharmonic oscillator
International Nuclear Information System (INIS)
Quantum dissipative effect of one dimension coupled anharmonic oscillator is investigated. The systems are two coupled harmonic oscillator with the different masses. The dissipative effect is studied based on the quantum state diffusion formalism. The result show that the anharmonic effect increase the amplitude but the lifetime of the oscillation depend on the damping coefficient and do not depend on the temperature
Quantum dissipative effect of one dimension coupled anharmonic oscillator
Energy Technology Data Exchange (ETDEWEB)
Sulaiman, A. [Badan Pengkajian dan Penerapan Teknologi, BPPT Bld. II (19thfloor), Jl. M.H. Thamrin 8, Jakarta 10340 (Indonesia); Indonesia Center for Theoretical and Mathematical Physics (ICTMP), Jl. Ganesha 10, Bandung 40132 (Indonesia); Zen, Freddy P. [Theoretical Physics Laboratory (THEPI), Department of Physics, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia); Indonesia Center for Theoretical and Mathematical Physics (ICTMP), Jl. Ganesha 10, Bandung 40132 (Indonesia)
2015-04-16
Quantum dissipative effect of one dimension coupled anharmonic oscillator is investigated. The systems are two coupled harmonic oscillator with the different masses. The dissipative effect is studied based on the quantum state diffusion formalism. The result show that the anharmonic effect increase the amplitude but the lifetime of the oscillation depend on the damping coefficient and do not depend on the temperature.
Ahmed, M.; Gu, F.; Ball, A. D.
2012-05-01
Traditional vibration monitoring techniques have found it difficult to determine a set of effective diagnostic features due to the high complexity of the vibration signals originating from the many different impact sources and wide ranges of practical operating conditions. In this paper Principal Component Analysis (PCA) is used for selecting vibration feature and detecting different faults in a reciprocating compressor. Vibration datasets were collected from the compressor under baseline condition and five common faults: valve leakage, inter-cooler leakage, suction valve leakage, loose drive belt combined with intercooler leakage and belt loose drive belt combined with suction valve leakage. A model using five PCs has been developed using the baseline data sets and the presence of faults can be detected by comparing the T2 and Q values from the features of fault vibration signals with corresponding thresholds developed from baseline data. However, the Q -statistic procedure produces a better detection as it can separate the five faults completely.
Analysis and Modelling of Muscles Motion during Whole Body Vibration
Directory of Open Access Journals (Sweden)
La Gatta A
2010-01-01
Full Text Available The aim of the study is to characterize the local muscles motion in individuals undergoing whole body mechanical stimulation. In this study we aim also to evaluate how subject positioning modifies vibration dumping, altering local mechanical stimulus. Vibrations were delivered to subjects by the use of a vibrating platform, while stimulation frequency was increased linearly from 15 to 60 Hz. Two different subject postures were here analysed. Platform and muscles motion were monitored using tiny MEMS accelerometers; a contra lateral analysis was also presented. Muscle motion analysis revealed typical displacement trajectories: motion components were found not to be purely sinusoidal neither in phase to each other. Results also revealed a mechanical resonant-like behaviour at some muscles, similar to a second-order system response. Resonance frequencies and dumping factors depended on subject and his positioning. Proper mechanical stimulation can maximize muscle spindle solicitation, which may produce a more effective muscle activation.
Electromagnetic Vibration Energy Harvesting Devices Architectures, Design, Modeling and Optimization
Spreemann, Dirk
2012-01-01
Electromagnetic vibration transducers are seen as an effective way of harvesting ambient energy for the supply of sensor monitoring systems. Different electromagnetic coupling architectures have been employed but no comprehensive comparison with respect to their output performance has been carried out up to now. Electromagnetic Vibration Energy Harvesting Devices introduces an optimization approach which is applied to determine optimal dimensions of the components (magnet, coil and back iron). Eight different commonly applied coupling architectures are investigated. The results show that correct dimensions are of great significance for maximizing the efficiency of the energy conversion. A comparison yields the architectures with the best output performance capability which should be preferably employed in applications. A prototype development is used to demonstrate how the optimization calculations can be integrated into the design–flow. Electromagnetic Vibration Energy Harvesting Devices targets the design...
Structure and vibrational spectra of a model of a-Si:H with periodic boundary conditions
Energy Technology Data Exchange (ETDEWEB)
Winer, K.; Wooten, F.
1983-08-01
A ball-and -stick model of a-Si:H with periodic boundary conditions has been constructed. A computer replica of the structure has been relaxed and the density, radial distribution function and vibrational spectra calculated.
Simplified vibration analysis method of shells of revolution using beam model
International Nuclear Information System (INIS)
A simplified vibration analysis method for the shells of revolution using the beam model is now under consideration. In the beam model, the relations between the shear forces and horizontal deformations are used for the calculations of the shear area and the relations between the overturning moments and rotation angles are for those of the inertia moment. The calculations of the vibration characteristics of the cylindrical shell, spherical shell and the cylindrical shell with the spherical cap were conducted to verify the accuracy of the beam model. The natural frequencies and the vibration modes of the proposed method are in good agreement with that of the FEM analysis using the axisymmetrical shell model. The proposed method is easily applicable to the vibration analysis of actual shell structures. (author)
Cohesive and anharmonic elastic properties of mixed fluorite crystals
International Nuclear Information System (INIS)
The cohesive and anharmonic elastic properties of four mixed fluorite crystals (CaxSr1-xF2, SrxBa1-xF2, BaxCa1-xF2 and CdxPb1-xF2) have been investigated by means of a three-body potential (TBP) model which consists of the long-range Coulomb and three-body interactions and the short-range van der Waals attraction and overlap repulsion effective upto the second neighbour ions. Due to the lack of measured data on cohesive energy, third-order elastic constants and pressure derivatives of the second-order elastic constants of mixed fluorites, the accuracy of the present results has been tested by comparing them with the so-called experimental results generated by the application of Vegard's law to their corresponding experimental values for the host fluorites. (author). 32 refs, 3 figs, 1 tab
Approximation methods for the partition functions of anharmonic systems
International Nuclear Information System (INIS)
The analytical approximations for the classical, quantum mechanical and reduced partition functions of the diatomic molecule oscillating internally under the influence of the Morse potential have been derived and their convergences have been tested numerically. This successful analytical method is used in the treatment of anharmonic systems. Using Schwinger perturbation method in the framework of second quantization formulism, the reduced partition function of polyatomic systems can be put into an expression which consists separately of contributions from the harmonic terms, Morse potential correction terms and interaction terms due to the off-diagonal potential coefficients. The calculated results of the reduced partition function from the approximation method on the 2-D and 3-D model systems agree well with the numerical exact calculations
Estimation of Reversed Flow in Long Pipeline Based on Axial Vibration Model of Dense Paste
Directory of Open Access Journals (Sweden)
Fuyan Lyu
2016-01-01
Full Text Available Intense axial vibration of the paste and the reversed flow make damage to the transportation system and lag the transport progress. This paper analyzed the axial vibration of the paste by building the vibration model according to the working situations of the system. The amount of the reversed flow share is then estimated based on the formed axial vibration model. The estimation of the reversed flow is carried out by counting the amount of the decompressed paste in certain time, which is being relative to the displacement in a single process of the vibration in numerical. The estimation of the reversed flow share of coal slime paste under certain transportation conditions was given and compared with the result based on the wave velocity method. It is evident that the introduction of axial vibration model into the study of the pipeline transportation system is feasible and reasonable, which also supplements the theoretical foundation for the analysis of dense paste vibrations in pipeline transportation system and its impacts on the system.
Nonlinear Model and Qualitative Analysis for Coupled Axial/Torsional Vibrations of Drill String
Fushen Ren; Baojin Wang; Suli Chen; Zhigang Yao; Baojun Bai
2016-01-01
A nonlinear dynamics model and qualitative analysis are presented to study the key effective factors for coupled axial/torsional vibrations of a drill string, which is described as a simplified, equivalent, flexible shell under axial rotation. Here, after dimensionless processing, the mathematical models are obtained accounting for the coupling of axial and torsional vibrations using the nonlinear dynamics qualitative method, in which excitation loads and boundary conditions of the drill stri...
Yao, J M
2016-01-01
We discuss anharmonicity of the multi-octupole-phonon states in $^{208}$Pb based on a covariant density functional theory, by fully taking into account the interplay between the quadrupole and the octupole degrees of freedom. Our results indicate the existence of a large anharmonicity in the transition strengths, even though the excitation energies are similar to those in the harmonic limit. We also show that the quadrupole-shape fluctuation significantly enhances the fragmentation of the two-octupole-phonon states in $^{208}$Pb. Using those transition strengths as inputs to coupled channels calculations, we then discuss the fusion reaction of $^{16}$O+$^{208}$Pb at energies around the Coulomb barrier. We show that the anharmonicity of the octupole vibrational excitation considerably improves previous coupled-channels calculations in the harmonic oscillator limit, significantly reducing the height of the main peak in the fusion barrier distribution.
A new online secondary path modeling method for adaptive active structure vibration control
International Nuclear Information System (INIS)
This paper proposes a new variable step size FXLMS algorithm with an auxiliary noise power scheduling strategy for online secondary path modeling. The step size for the secondary path modeling filter and the gain of auxiliary noise are varied in accordance with the parameters available directly. The proposed method has a low computational complexity. Computer simulations show that an active vibration control system with the proposed method gives much better vibration attenuation and modeling accuracy at a faster convergence rate than existing methods. National Instruments’ CompactRIO is used as an embedded processor to control simply supported beam vibration. Experimental results indicate that the vibration of the beam has been effectively attenuated. (papers)
RESEARCH ON ACTIVE VIBRATION CONTROL BASED ON COMBINED MODEL FOR COUPLED SYSTEMS
Institute of Scientific and Technical Information of China (English)
Niu Junchuan; Zhao Guoqun; Song Kongjie
2004-01-01
A novel combined model of the vibration control for the coupled flexible system and its general mathematic description are developed. In presented model, active and passive controls as well as force and moment controls are combined into a single unit to achieve the efficient vibration control of the flexible structures by multi-approaches. Considering the complexity of the energy transmission in the vibrating system, the transmission channels of the power flow transmitted into the foundation are discussed, and the general forces and the corresponding velocities are combined into a single function, respectively. Under the control strategy of the minimum power flow, the transmission characteristics of the power flow are investigated. From the presented numerical examples, it is obvious that the analytical model is effective, and both force and moment controls are able to depress vibration energy substantially.
Vibrational relaxation in liquids: Comparisons between gas phase and liquid phase theories
International Nuclear Information System (INIS)
The vibrational relaxation of iodine in liquid xenon was studied to understand what processes are important in determining the density dependence of the vibrational relaxation. This examination will be accomplished by taking simple models and comparing the results to both experimental outcomes and the predictions of molecular dynamics simulations. The vibration relaxation of iodine is extremely sensitive to the iodine potential. The anharmonicity of iodine causes vibrational relaxation to be much faster at the top of the iodine well compared to the vibrational relaxation at the bottom. A number of models are used in order to test the ability of the Isolated Binary Collision theory's ability to predict the density dependence of the vibrational relaxation of iodine in liquid xenon. The models tested vary from the simplest incorporating only the fact that the solvent occupies volume to models that incorporate the short range structure of the liquid in the radial distribution function. None of the models tested do a good job of predicting the actual relaxation rate for a given density. This may be due to a possible error in the choice of potentials to model the system
Influence of tyre-road contact model on vehicle vibration response
Múčka, Peter; Gagnon, Louis
2015-09-01
The influence of the tyre-road contact model on the simulated vertical vibration response was analysed. Three contact models were compared: tyre-road point contact model, moving averaged profile and tyre-enveloping model. In total, 1600 real asphalt concrete and Portland cement concrete longitudinal road profiles were processed. The linear planar model of automobile with 12 degrees of freedom (DOF) was used. Five vibration responses as the measures of ride comfort, ride safety and dynamic load of cargo were investigated. The results were calculated as a function of vibration response, vehicle velocity, road quality and road surface type. The marked differences in the dynamic tyre forces and the negligible differences in the ride comfort quantities were observed among the tyre-road contact models. The seat acceleration response for three contact models and 331 DOF multibody model of the truck semi-trailer was compared with the measured response for a known profile of test section.
Zhao, S.; Erturk, A.
2013-01-01
We present electroelastic modeling, analytical and numerical solutions, and experimental validations of piezoelectric energy harvesting from broadband random vibrations. The modeling approach employed herein is based on a distributed-parameter electroelastic formulation to ensure that the effects of higher vibration modes are included, since broadband random vibrations, such as Gaussian white noise, might excite higher vibration modes. The goal is to predict the expected value of the power output and the mean-square shunted vibration response in terms of the given power spectral density (PSD) or time history of the random vibrational input. The analytical method is based on the PSD of random base excitation and distributed-parameter frequency response functions of the coupled voltage output and shunted vibration response. The first of the two numerical solution methods employs the Fourier series representation of the base acceleration history in an ordinary differential equation solver while the second method uses an Euler-Maruyama scheme to directly solve the resulting electroelastic stochastic differential equations. The analytical and numerical simulations are compared with several experiments for a brass-reinforced PZT-5H bimorph under different random excitation levels. The simulations exhibit very good agreement with the experimental measurements for a range of resistive electrical boundary conditions and input PSD levels. It is also shown that lightly damped higher vibration modes can alter the expected power curve under broadband random excitation. Therefore, the distributed-parameter modeling and solutions presented herein can be used as a more accurate alternative to the existing single-degree-of-freedom solutions for broadband random vibration energy harvesting.
International Nuclear Information System (INIS)
Fundamental studies in vibrational energy harvesting consider the electromechanically coupled devices to be excited by uniform base vibration. Since many harvester devices are mass–spring systems, there is a clear opportunity to exploit the mechanical resonance in a fashion identical to tuned mass dampers to simultaneously suppress the vibration of the host structure via reactive forces while converting the ‘absorbed’ vibration into electrical power. This paper presents a general analytical model for the coupled electro-elastic dynamics of a vibrating panel to which distributed energy harvesting devices are attached. One such device is described which employs a corrugated piezoelectric spring layer. The model is validated by comparison to measured elastic and electric frequency response functions. Tests on an excited panel show that the device, contributing 1% additional mass to the structure, concurrently attenuates the lowest panel mode accelerance by >20 dB while generating 0.441 µW for a panel drive acceleration of 3.29 m s−2. Adjustment of the load resistance connected to the piezoelectric spring layer verifies the analogy between the present harvester device and an electromechanically stiffened and damped vibration absorber. The results show that maximum vibration suppression and energy harvesting objectives occur for nearly the same load resistance in the harvester circuit. (paper)
Research on the Identification Modeling of Air-Magnet Active Vibration Isolation System
Directory of Open Access Journals (Sweden)
Wen Xianglong
2015-01-01
Full Text Available The methods of the identification modeling of air-magnet active vibration isolation system (AMAVIS are studied. Difference equation model and transfer function model are established respectively in the time domain and frequency domain. The models are analyzed and proved by the experiment. Identification results show that the order of frequency identification is higher than the time identification model. But when it comes to accuracy and convergence, frequency identification model has obvious advantage. This paper provides evidence for subsequent active vibration control. The conclusion is the basic of subsequent experiment and research.
Modelling and Analysis of Vibrations in a UAV Helicopter with a Vision System
Directory of Open Access Journals (Sweden)
G. Nicolás Marichal Plasencia
2012-11-01
Full Text Available The analysis of the nature and damping of unwanted vibrations on Unmanned Aerial Vehicle (UAV helicopters are important tasks when images from on‐board vision systems are to be obtained. In this article, the authors model a UAV system, generate a range of vibrations originating in the main rotor and design a control methodology in order to damp these vibrations. The UAV is modelled using VehicleSim, the vibrations that appear on the fuselage are analysed to study their effects on the on‐board vision system by using Simmechanics software. Following this, the authors present a control method based on an Adaptive Neuro‐Fuzzy Inference System (ANFIS to achieve satisfactory damping results over the vision system on board.
Scale-model characterization of flow-induced vibrational response of FFTF reactor internals
International Nuclear Information System (INIS)
Fast Test Reactor core internal and peripheral components were assessed for flow-induced vibrational characteristics under scaled and simulated prototype flow conditions in the Hydraulic Core Mockup as an integral part of the Fast Test Reactor Vibration Program. The Hydraulic Core Mockup was an 0.285 geometric scale model of the Fast Test Reactor internals designed to simulate prototype vibrational and hydraulic characteristics. Using water to simulate sodium coolant, vibrational characteristics were measured and determined for selected model components over the scaled flow range of 36 to 110%. Additionally, in-situ shaker tests were conducted on selected Hydraulic Core Mockup outlet plenum components to establish modal characteristics. Most components exhibited resonant response at all test flow rates; however, the measured dynamic response was neither abnormal nor anomalously flow-rate dependent, and the predicted prototype components' response were deemed acceptable
Experimental and Numerical Investigations on Vibration Characteristics of a Loaded Ship Model
Institute of Scientific and Technical Information of China (English)
Pu Liang; Ming Hong; Zheng Wang
2015-01-01
In this paper, the vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method (FEM) by 8-node acoustic fluid elements. The vibration characteristics of the structure in the finite fluid domain are calculated combining structure FEM mass matrix. By writing relevant programs, the numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain.
Stabilization for the Vibrations Modeled by the `Standard Linear Model' of Viscoelasticity
Indian Academy of Sciences (India)
Ganesh C Gorain
2010-09-01
We study the stabilization of vibrations of a flexible structure modeled by the `standard linear model’ of viscoelasticity in a bounded domain in $\\mathbb{R}^n$ with a smooth boundary. We prove that amplitude of the vibrations remains bounded in the sense of a suitable norm in a space $\\mathbb{X}$, defined explicitly in (22) subject to a restriction on the uncertain disturbing forces on $\\mathbb{X}$. We also estimate the total energy of the system over time interval [0,] for any >0, with a tolerance level of the disturbances. Finally, when the input disturbances are insignificant, uniform exponential stabilization is obtained and an explicit form for the energy decay rate is derived. These results are achieved by a direct method under undamped mixed boundary conditions.
Non-linear journal bearing model for analysis of superharmonic vibrations of rotor systems
Energy Technology Data Exchange (ETDEWEB)
Hannukainen, P.
2008-07-01
A rotating machine usually consists of a rotor and bearings that supports it. The nonidealities in these components may excite vibration of the rotating system. The uncontrolled vibrations may lead to excessive wearing of the components of the rotating machine or reduce the process quality. Vibrations may be harmful even when amplitudes are seemingly low, as is usually the case in superharmonic vibration that takes place below the first critical speed of the rotating machine. Superharmonic vibration is excited when the rotational velocity of the machine is a fraction of the natural frequency of the system. In such a situation, a part of the machineAEs rotational energy is transformed into vibration energy. The amount of vibration energy should be minimised in the design of rotating machines. The superharmonic vibration phenomena can be studied by analysing the coupled rotor-bearing system employing a multibody simulation approach. This research is focused on the modelling of hydrodynamic journal bearings and rotorbearing systems supported by journal bearings. In particular, the non-idealities affecting the rotor-bearing system and their effect on the superharmonic vibration of the rotating system are analysed. A comparison of computationally efficient journal bearing models is carried out in order to validate one model for further development. The selected bearing model is improved in order to take the waviness of the shaft journal into account. The improved model is implemented and analyzed in a multibody simulation code. A rotor-bearing system that consists of a flexible tube roll, two journal bearings and a supporting structure is analysed employing the multibody simulation technique. The modelled non-idealities are the shell thickness variation in the tube roll and the waviness of the shaft journal in the bearing assembly. Both modelled non-idealities may cause subharmonic resonance in the system. In multibody simulation, the coupled effect of the non
Anharmonic potential in the oscillator representation
International Nuclear Information System (INIS)
In the non relativistic and relativized Schroedinger equation the Wick ordering method called the oscillator representation is proposed to calculate the energy spectrum for a wide class of potentials allowing the existence of a bound state. The oscillator representation method gives a unique regular way to describe and calculate the energy levels of ground as well as orbital and radial excitation states for a wide class of potentials. The results of the zeroth approximation oscillator representation are in good agreement with the exact values for the anharmonic potentials. The oscillator representation method was applied to the relativized Schroedinger equation too. The perturbation series converges fairly fast, i.e., the highest perturbation corrections over the interaction Hamiltonian are small enough. 29 refs.; 4 tabs. (author)
Comparison of vibration test results for Atucha II NPP and large scale concrete block models
International Nuclear Information System (INIS)
In order to study the soil structure interaction of reactor building that could be constructed on a Quaternary soil, a comparison study of the soil structure interaction springs was performed between full scale vibration test results of Atucha II NPP and vibration test results of large scale concrete block models constructed on Quaternary soil. This comparison study provides a case data of soil structure interaction springs on Quaternary soil with different foundation size and stiffness. (author)
Free Vibration Analysis for Cracked FGM Beams by Means of a Continuous Beam Model
E Chuan Yang; Xiang Zhao; Ying Hui Li
2015-01-01
Based on Euler-Bernoulli beam theory and a continuous stiffness beam model, the free vibration of rectangular-section beams made of functionally graded materials (FGMs) containing open edge cracks is studied. Assuming the material gradients follow exponential distribution along beam thickness direction, the conversion relation between the vibration governing equations of a FGM beam and that of an isotropic homogenous beam is deduced. A continuous function is used to characterize the bending s...
International Nuclear Information System (INIS)
It is general practice to use a simple beam model in the analysis of the vibration characteristics of a slender rod for the simplicity and easiness to get the results. Besides the circular cross-section, fuel rods may have twisted square cross section in order to enhance the mechanical and thermo-hydraulic performance. In this case the modeling for the analysis of the vibration takes much efforts to simulate it properly. Instead of the more complex solid modeling, a simple beam model can be used if the simulation is properly done. In this study, the validity of the use of a simple beam model for the twisted square rod are discussed and the results of the two calculations are evaluated. The results show that the simple equivalent beam model also can be applied for this type of the rod on the vibration analysis and the effect of the twisted form on the rigidity of the rod is negligibly small
Modelling vibrational coherence in the primary rhodopsin photoproduct
Weingart, O.; Garavelli, M.
2012-12-01
Molecular dynamics simulations of the rhodopsin photoreaction reveal coherent low frequency oscillations in the primary photoproduct (photorhodopsin), with frequencies slightly higher than observed in the experiment. The coherent molecular motions in the batho-precursor can be attributed to the activation of ground state vibrational modes in the hot photo-product, involving out-of-plane deformations of the carbon skeleton. Results are discussed and compared with respect to spectroscopic data and suggested reaction mechanisms.
Agarwalla, Bijay Kumar; Jiang, Jian-Hua; Segal, Dvira
2015-12-01
We study the statistical properties of charge and energy transport in electron conducting junctions with electron-phonon interactions, specifically, the thermoelectric efficiency and its fluctuations. The system comprises donor and acceptor electronic states, representing a two-site molecule or a double-quantum-dot system. Electron transfer between metals through the two molecular sites is coupled to a particular vibrational mode which is taken to be either harmonic or anharmonic, a truncated (two-state) spectrum. Considering these models we derive the cumulant generating function in steady state for charge and energy transfer, correct to second order in the electron-phonon interaction, but exact to all orders in the metal-molecule coupling strength. This is achieved by using the nonequilibrium Green's function approach (harmonic mode) and a kinetic quantum master-equation method (anharmonic mode). From the cumulant generating function we calculate the charge current and its noise and the large-deviation function for the thermoelectric efficiency. We demonstrate that at large bias the charge current, differential conductance, and the current noise can identify energetic and structural properties of the junction. We further examine the operation of the junction as a thermoelectric engine and show that while the macroscopic thermoelectric efficiency is indifferent to the nature of the mode (harmonic or anharmonic), efficiency fluctuations do reflect this property.
Large-amplitude motion in the Suzuki model
International Nuclear Information System (INIS)
The classical and quantum aspects for the analytically solvable one-dimensional pure monopole Suzuki model are studied to clarify the problem of quantization of classical collective motion. A set of nonlinear dynamic equations for a monopole moment of a nucleus are derived from the TDHF equation using the Wigner function moments model. It provides to describe large-amplitude monopole vibrations. The corresponding collective Hamiltonian is constructed and quantized. The anharmonicity of the collective spectra is analyzed in detal
Ice-shelf forced vibrations modelled with a full 3-D elastic model
Directory of Open Access Journals (Sweden)
Y. V. Konovalov
2014-12-01
Full Text Available Ice-shelf forced vibrations modelling was performed using a full 3-D finite-difference elastic model, which takes into account sub-ice seawater flow. The sub-ice seawater flow was described by the wave equation, so the ice-shelf flexures result from the hydrostatic pressure perturbations in sub-ice seawater layer. The numerical experiments were performed for idealized ice-shelf geometry, which was considered in the numerical experiments in Holdsworth and Glynn (1978. The ice-plate vibrations were modelled for harmonic ingoing pressure perturbations and for a wide spectrum of the ocean swell periodicities, ranging from infragravity wave periods down to periods of a few seconds (0.004–0.2 Hz. The spectrums for the vibration amplitudes were obtained in this range and are published in this manuscript. The spectrums contain distinct resonant peaks, which corroborate the ability of resonant-like motion in suitable conditions of the forcing. The impact of local irregularities in the ice-shelf geometry to the amplitude spectrums was investigated for idealized sinusoidal perturbations of the ice surface and the sea bottom. The results of the numerical experiments presented in this manuscript, are approximately in agreement with the results obtained by the thin-plate model in the research carried out by Holdsworth and Glynn (1978. In addition, the full model allows to observe 3-D effects, for instance, vertical distribution of the stress components in the plate. In particular, the model reveals the increasing in shear stress, which is neglected in the thin-plate approximation, from the terminus towards the grounding zone with the maximum at the grounding line in the case of considered high-frequency forcing. Thus, the high-frequency forcing can reinforce the tidal impact to the ice-shelf grounding zone additionally exciting the ice fracture there.
A theory of the strain-dependent critical field in Nb3Sn, based on anharmonic phonon generation
Valentinis, D F; Bordini, B; Rossi, L
2014-01-01
We propose a theory to explain the strain dependence of the critical properties in A15 superconductors. Starting from the strong-coupling formula for the critical temperature, and assuming that the strain sensitivity stems mostly from the electron-phonon alpha F-2 function, we link the strain dependence of the critical properties to a widening of alpha F-2. This widening is attributed to the nonlinear generation of phonons, which takes place in the anharmonic deformation potential induced by the strain. Based on the theory of sum- and difference-frequency wave generation in nonlinear media, we obtain an explicit connection between the widening of alpha F-2 and the anharmonic energy. The resulting model is fit to experimental datasets for Nb3Sn, and the anharmonic energy extracted from the fits is compared with first-principles calculations.
Model-based failure detection for cylindrical shells from noisy vibration measurements.
Candy, J V; Fisher, K A; Guidry, B L; Chambers, D H
2014-12-01
Model-based processing is a theoretically sound methodology to address difficult objectives in complex physical problems involving multi-channel sensor measurement systems. It involves the incorporation of analytical models of both physical phenomenology (complex vibrating structures, noisy operating environment, etc.) and the measurement processes (sensor networks and including noise) into the processor to extract the desired information. In this paper, a model-based methodology is developed to accomplish the task of online failure monitoring of a vibrating cylindrical shell externally excited by controlled excitations. A model-based processor is formulated to monitor system performance and detect potential failure conditions. The objective of this paper is to develop a real-time, model-based monitoring scheme for online diagnostics in a representative structural vibrational system based on controlled experimental data. PMID:25480059
International Nuclear Information System (INIS)
This study explores the possibilities for inverse analysis and modelling from data of a nonlinearly vibrating structure. We are suggesting a statistical approach based on singular spectrum analysis (SSA). The method is based on a free decay response, when the structure is given an initial disturbance and is left to vibrate on its own. The measured vibration response is decomposed into new variables, the principal components, which are used to uncover oscillatory patterns in the structural response. In this study an application of the methodology for the purposes of delamination detection in a composite beam is explored.
Nonlinear Model and Qualitative Analysis for Coupled Axial/Torsional Vibrations of Drill String
Directory of Open Access Journals (Sweden)
Fushen Ren
2016-01-01
Full Text Available A nonlinear dynamics model and qualitative analysis are presented to study the key effective factors for coupled axial/torsional vibrations of a drill string, which is described as a simplified, equivalent, flexible shell under axial rotation. Here, after dimensionless processing, the mathematical models are obtained accounting for the coupling of axial and torsional vibrations using the nonlinear dynamics qualitative method, in which excitation loads and boundary conditions of the drill string are simplified to a rotating, flexible shell. The analysis of dynamics responses is performed by means of the Runge-Kutta-Fehlberg method, in which the rules that govern the changing of the torsional and axial excitation are revealed, and suggestions for engineering applications are also given. The simulation analysis shows that when the drill string is in a lower-speed rotation zone, the torsional excitation is the key factor in the coupling vibration, and increasing the torsional stress of the drill string more easily leads to the coupling vibration; however, when the drill string is in a higher-speed rotating zone, the axial excitation is a key factor in the coupling vibration, and the axial stress in a particular interval more easily leads to the coupling vibration of the drill string.
Probing anharmonicity of a quantum oscillator in an optomechanical cavity
Latmiral, Ludovico; Armata, Federico; Genoni, Marco G.; Pikovski, Igor; Kim, M. S.
2016-05-01
We present a way of measuring with high precision the anharmonicity of a quantum oscillator coupled to an optical field via radiation pressure. Our protocol uses a sequence of pulsed interactions to perform a loop in the phase space of the mechanical oscillator, which is prepared in a thermal state. We show how the optical field acquires a phase depending on the anharmonicity. Remarkably, one only needs small initial cooling of the mechanical motion to probe even small anharmonicities. Finally, by applying tools from quantum estimation theory, we calculate the ultimate bound on the estimation precision posed by quantum mechanics and compare it with the precision obtainable with feasible measurements such as homodyne and heterodyne detection on the cavity field. In particular we demonstrate that homodyne detection is nearly optimal in the limit of a large number of photons of the field and we discuss the estimation precision of small anharmonicities in terms of its signal-to-noise ratio.
Linear delta expansion technique for the solution of anharmonic oscillations
Indian Academy of Sciences (India)
P K Bera; J Datta
2007-01-01
The linear delta expansion technique has been developed for solving the differential equation of motion for symmetric and asymmetric anharmonic oscillators. We have also demonstrated the sophistication and simplicity of this new perturbation technique.
Dynamic Properties of Proton Transfer in the Anharmonic-Interaction Hydrogen Bond Systems
Institute of Scientific and Technical Information of China (English)
YAN Xun-Ling; DONG Rui-Xin; PANG Xiao-Feng
2001-01-01
We analyze the properties of the excited solitary-wave model in the case of anharmonic-interaction of heavy ionic lattice in hydrogen bond systems.In this case,some new phenomena appear.We find different types of solutions for the proton displacement and influences on the kinks and pulse solitary waves by numerical calculation.For each of them we have presented a direct relation with the effective potential of the system.
Electromechanical coupling model and analysis of transient behavior for inertial vibrating machines
Institute of Scientific and Technical Information of China (English)
HU Ji-yun; YU Cui-ping; YIN Xue-gang
2004-01-01
A mathematical model of electromechanical coupling system for a planar inertial vibrating machine is built by setting up dynamical equations of discrete systems with a matrix methodology proposed. The substance of the transient behavior of the machine is unveiled by analyzing the results of the computer simulation to the model, and new methods are presented for diminishing the transient amplitude of the vibrating machine and improving the transient behavior. The reliable mathematical model is provided for intelligent control of the transient behavior of the equipment.
Directory of Open Access Journals (Sweden)
XU, F.
2013-05-01
Full Text Available Orbital Friction Vibration Actuator (OFVA is a core component of Orbital Friction Welding (OFW, which is a novel apertureless welding technology utilizing friction heat to implement solid-state joining. In this paper, topology and operational principle of OFVA are introduced, the analytical formulas of the electromagnetic force for the x and y directions, which can drive the mover to generate a circular motion trajectory, are derived, and the characteristic of static electromagnetic force is predicted by analytical method and 2-D (two-dimensional FEM (finite element method, 3-D and measurement. The coupled magnetic field-circuit-motion simulation models which are driven by current and voltage source are established, respectively, and some of its operational characteristics are analyzed. Simulation and experiment validate theoretical analysis and the feasibility of the fabricated prototype, demonstrate the good performance of the OFVA, and provide valuable reference for engineering applications.
Nonlocal plate model for free vibrations of single-layered graphene sheets
Ansari, R.; Sahmani, S.; Arash, B.
2010-11-01
Vibration analysis of single-layered graphene sheets (SLGSs) is investigated using nonlocal continuum plate model. To this end, Eringens's nonlocal elasticity equations are incorporated into the classical Mindlin plate theory for vibrations of rectangular nanoplates. In contrast to the classical model, the nonlocal model developed in this study has the capability to evaluate the natural frequencies of the graphene sheets with considering the size-effects on the vibrational characteristics of them. Solutions for frequencies of the free vibration of simply-supported and clamped SLGSs are computed using generalized differential quadrature (GDQ) method. Then, molecular dynamics (MD) simulations for the free vibration of various SLGSs with different values of side length and chirality are employed, the results of which are matched with the nonlocal model ones to derive the appropriate values of the nonlocal parameter relevant to each boundary condition. It is found that the value of the nonlocal parameter is independent of the magnitude of the geometrical variables of the system.
Nonlocal plate model for free vibrations of single-layered graphene sheets
Energy Technology Data Exchange (ETDEWEB)
Ansari, R., E-mail: r_ansari@guilan.ac.i [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of); Sahmani, S.; Arash, B. [Department of Mechanical Engineering, University of Guilan, P.O. Box 3756, Rasht (Iran, Islamic Republic of)
2010-11-15
Vibration analysis of single-layered graphene sheets (SLGSs) is investigated using nonlocal continuum plate model. To this end, Eringens's nonlocal elasticity equations are incorporated into the classical Mindlin plate theory for vibrations of rectangular nanoplates. In contrast to the classical model, the nonlocal model developed in this study has the capability to evaluate the natural frequencies of the graphene sheets with considering the size-effects on the vibrational characteristics of them. Solutions for frequencies of the free vibration of simply-supported and clamped SLGSs are computed using generalized differential quadrature (GDQ) method. Then, molecular dynamics (MD) simulations for the free vibration of various SLGSs with different values of side length and chirality are employed, the results of which are matched with the nonlocal model ones to derive the appropriate values of the nonlocal parameter relevant to each boundary condition. It is found that the value of the nonlocal parameter is independent of the magnitude of the geometrical variables of the system.
Nonlocal plate model for free vibrations of single-layered graphene sheets
International Nuclear Information System (INIS)
Vibration analysis of single-layered graphene sheets (SLGSs) is investigated using nonlocal continuum plate model. To this end, Eringens's nonlocal elasticity equations are incorporated into the classical Mindlin plate theory for vibrations of rectangular nanoplates. In contrast to the classical model, the nonlocal model developed in this study has the capability to evaluate the natural frequencies of the graphene sheets with considering the size-effects on the vibrational characteristics of them. Solutions for frequencies of the free vibration of simply-supported and clamped SLGSs are computed using generalized differential quadrature (GDQ) method. Then, molecular dynamics (MD) simulations for the free vibration of various SLGSs with different values of side length and chirality are employed, the results of which are matched with the nonlocal model ones to derive the appropriate values of the nonlocal parameter relevant to each boundary condition. It is found that the value of the nonlocal parameter is independent of the magnitude of the geometrical variables of the system.
Boz, Utku; Basdogan, Ipek
2015-12-01
Structural vibrations is a major cause for noise problems, discomfort and mechanical failures in aerospace, automotive and marine systems, which are mainly composed of plate-like structures. In order to reduce structural vibrations on these structures, active vibration control (AVC) is an effective approach. Adaptive filtering methodologies are preferred in AVC due to their ability to adjust themselves for varying dynamics of the structure during the operation. The filtered-X LMS (FXLMS) algorithm is a simple adaptive filtering algorithm widely implemented in active control applications. Proper implementation of FXLMS requires availability of a reference signal to mimic the disturbance and model of the dynamics between the control actuator and the error sensor, namely the secondary path. However, the controller output could interfere with the reference signal and the secondary path dynamics may change during the operation. This interference problem can be resolved by using an infinite impulse response (IIR) filter which considers feedback of the one or more previous control signals to the controller output and the changing secondary path dynamics can be updated using an online modeling technique. In this paper, IIR filtering based filtered-U LMS (FULMS) controller is combined with online secondary path modeling algorithm to suppress the vibrations of a plate-like structure. The results are validated through numerical and experimental studies. The results show that the FULMS with online secondary path modeling approach has more vibration rejection capabilities with higher convergence rate than the FXLMS counterpart.
Directory of Open Access Journals (Sweden)
Xu Liu
2015-01-01
Full Text Available Unsteady aerodynamic system modeling is widely used to solve the dynamic stability problems encountering aircraft design. In this paper, single degree-of-freedom (SDF vibration model and forced simple harmonic motion (SHM model for dynamic derivative prediction are developed on the basis of modified Etkin model. In the light of the characteristics of SDF time domain solution, the free vibration identification methods for dynamic stability parameters are extended and applied to the time domain numerical simulation of blunted cone calibration model examples. The dynamic stability parameters by numerical identification are no more than 0.15% deviated from those by experimental simulation, confirming the correctness of SDF vibration model. The acceleration derivatives, rotary derivatives, and combination derivatives of Army-Navy Spinner Rocket are numerically identified by using unsteady N-S equation and solving different SHV patterns. Comparison with the experimental result of Army Ballistic Research Laboratories confirmed the correctness of the SHV model and dynamic derivative identification. The calculation result of forced SHM is better than that by the slender body theory of engineering approximation. SDF vibration model and SHM model for dynamic stability parameters provide a solution to the dynamic stability problem encountering aircraft design.
Kinetic model of vibrational relaxation in a humid-air pulsed corona discharge
Energy Technology Data Exchange (ETDEWEB)
Komuro, Atsushi; Ono, Ryo [Department of Advanced Energy, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 227-8568 (Japan); Oda, Tetsuji, E-mail: komuro@streamer.t.u-tokyo.ac.j, E-mail: ryo-ono@k.u-tokyo.ac.j [Department of Electrical Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 (Japan)
2010-10-15
The effect of humidity on the vibrational relaxation of O{sub 2}(v) and N{sub 2}(v) in a humid-air pulsed corona discharge is studied using a kinetic model. We previously showed that humidity markedly increases the vibration-to-translation (V-T) rate of molecules in a humid-air pulsed corona discharge by measuring O{sub 2}(v) density (Ono et al 2010 Plasma Sources Sci. Technol. 19 015009). In this paper, we numerically calculate the vibrational kinetics of O{sub 2}, N{sub 2} and H{sub 2}O to study the reason behind the acceleration of V-T in the presence of humidity. The calculation closely reproduces the measured acceleration of V-T due to humidity, and shows that the increase in the V-T rate is caused by the fast vibration-to-vibration (V-V) processes of O{sub 2}-H{sub 2}O and N{sub 2}-H{sub 2}O and the subsequent rapid V-T process of H{sub 2}O-H{sub 2}O. In addition, it is shown that O atom density is also important in the vibrational kinetics owing to the rapid V-T process of O{sub 2}-O.
A Simplified Model for Vibration Analysis of Diesel Engine Crankshaft System
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A spatial finite element model for vibration analysis of crankshaft system was proposed. The crankshaft body was simplified as spatial rigid frame by using beam elements based on Timoshenko beam theory. The main bearings in system were simplified as linear springs and dashpots. The natural frequencies of the crankshaft system of a four in-line cylinder engine were calculated and compared with the analytical and experimental values available in other publications. In order to simulate the motion of operating crankshaft system, the gas forces, rotating masses and reciprocating masses were considered, the crankshaft and main bearings were coupled in a rotating coordinate system, and a dynamic model for vibration analysis of crankshaft system was established. By applying the dynamic model, the influence of the mass and moment of inertia of front pulley on the behavior of crankshaft vibration was investigated.
U(2) algebraic model applied to stretching vibrational spectra of tetrahedral molecules
Hou, X W; Hou, Xi-Wen; Ma, Zhong-Qi
1998-01-01
The highly excited stretching vibrational energy levels and the intensities of infrared transitions in tetrahedral molecules are studied in a U(2) algebraic model. Its applications to silane and silicon tetrafluoride are presented with smaller standard deviations than those of other models.
Deriving Vibration Modes of Semi-infinite Chain Model by "Invariant Eigen-operator"Method
Institute of Scientific and Technical Information of China (English)
ZHANG Lin-Na; FAN Hong-Yi; FU Zun-Tao; and WU Hao; LIU Shi-Kuo
2008-01-01
For the first time, we introduce a fully quantum mechanical Hamiltonian for a semi-infinite chain model of atoms. We then derive the vibration modes of this model by virtue of the "invariant eigen-operator" method in two different cases, which is concise and revealing.
Modeling of wave propagation in drill strings using vibration transfer matrix methods.
Han, Je-Heon; Kim, Yong-Joe; Karkoub, Mansour
2013-09-01
In order to understand critical vibration of a drill bit such as stick-slip and bit-bounce and their wave propagation characteristics through a drill string system, it is critical to model the torsional, longitudinal, and flexural waves generated by the drill bit vibration. Here, a modeling method based on a vibration transfer matrix between two sets of structural wave variables at the ends of a constant cross-sectional, hollow, circular pipe is proposed. For a drill string system with multiple pipe sections, the total vibration transfer matrix is calculated by multiplying all individual matrices, each is obtained for an individual pipe section. Since drill string systems are typically extremely long, conventional numerical analysis methods such as a finite element method (FEM) require a large number of meshes, which makes it computationally inefficient to analyze these drill string systems numerically. The proposed "analytical" vibration transfer matrix method requires significantly low computational resources. For the validation of the proposed method, experimental and numerical data are obtained from laboratory experiments and FEM analyses conducted by using a commercial FEM package, ANSYS. It is shown that the modeling results obtained by using the proposed method are well matched with the experimental and numerical results. PMID:23967925
Dynamics Modelling of a Plate Vibrating in a Perfect Fluid
Directory of Open Access Journals (Sweden)
Bouarroudj Nadra
2007-01-01
Full Text Available We deal with the interaction problem of a plate vibrating within a perfect fluid. We establish the equations describing the dynamics behaviour of the plate using the general equations of the elasto-dynamic. The fluid flow described by the equation of Eulers low amplitude. We presented results of the existence, the unicity and the regularity of the problem verified by the plate as well as by the fluid We used the integral equations for the numerical resolution of the problem that allowed us to determine the coupling term between the fluid and the plate. The numerical results were obtained using finite element method coupled with an implicit diagram in time.
Mathematical model for cross-flow-induced vibrations of tube rows
International Nuclear Information System (INIS)
A mathematical model is presented for cross-flow-induced vibrations of tube banks including the effects of vortex shedding, fluidelastic coupling, drag force, fluid inertia coupling, and others. The model can predict the details of complex tube-fluid interactions: (1) natural frequencies and mode shapes of coupled vibrations; (2) critical flow velocities; (3) responses to vortex shedding, drag force, and other types of excitations; and (4) the dominant excitation mechanism at a given flow velocity. The analytical results are in good agreement with the published experimental results
On the modeling of vibration transmission over a spatially curved cable with casing
Otrin, Miha; Boltežar, Miha
2009-09-01
We propose an approach to the vibration modeling of spatially curved steel wires with a casing and a contact between the outer casing and the inner steel wire. For the mathematical model of the steel wire and the outer casing, the Euler-Bernoulli beam theory with no axial pre-load is used, and for the discretisation, finite elements are used. The excitation of the steel wire and the outer casing is in the form of random kinematic excitation. For the energy dissipation the proportional viscous damping model and the structural damping model are used. The damping parameters are identified from the Nyquist diagram and from the continuous wavelet transform. For the identification of the frequency dependence of the dynamic modulus of elasticity a method is proposed that uses the measured natural frequencies and the experimentally determined natural modes. The contact between the steel wire and the outer casing is modelled using the penalty method with the friction in a tangential direction. We show that higher values of the friction coefficient have a significant influence on lowering the level of vibration transmission. The model also predicts that the dynamic modulus of the elasticity of a steel wire does not have a major influence on the level of vibration transmission, which was also validated by experiment. On the basis of an experimental validation the model of a steel wire with an outer casing proved to be suitable for the prediction of the vibration transmission.
Vibration response of a railway track obtained using numerical models based on FEM
Directory of Open Access Journals (Sweden)
Cardona Foix S.
2012-07-01
Full Text Available In the last forty years, researchers have developed models of wheel-rail contact force in order to study vibrations and rolling noise caused by railway traffic. These models range from analytical models, who consider a single rail of a railway track in contact with a rigid wheel attached to the bogie by means of the primary suspension, to numerical models based on finite element methods, boundary element, and mixed methods. Unlike analytical models, numerical models allow us to characterize more precisely the different components of railway track structure and consider the interaction between the entire track and a complete vehicle wheel-set. The study of the elements constituting the set of the railway track, the wheel-set and the primary suspension, as well as the knowledge of their influence in vibration generation and transmission due to train passage is of great interest when evaluating the possible vibration effects in the railway surrounding areas. This paper presents a numerical model of the track structure based on the finite element method. It is devoted to the study of the vibration response caused by vertical forces applied at any location on the rails. The numerical results are compared with analytical results previously presented in the bibliography.
Quartic oscillator potential in the γ-rigid regime of the collective geometrical model
International Nuclear Information System (INIS)
A prolate γ-rigid version of the Bohr-Mottelson Hamiltonian with a quartic anharmonic oscillator potential in β collective shape variable is used to describe the spectra for a variety of vibrational-like nuclei. Speculating the exact separation between the two Euler angles and the β variable, one arrives at a differential Schroedinger equation with a quartic anharmonic oscillator potential and a centrifugal-like barrier. The corresponding eigenvalue is approximated by an analytical formula depending only on a single parameter up to an overall scaling factor. The applicability of the model is discussed in connection to the existence interval of the free parameter, which is limited by the accuracy of the approximation, and by comparison with the predictions of the related X(3) and X(3)-β 2 models. The model is applied to qualitatively describe the spectra for nine nuclei which exhibit near-vibrational features. (orig.)
DEFF Research Database (Denmark)
Friis, Lars; Ohlrich, Mogens
2008-01-01
-dimensional continuous boundary. Additionally, a simple method for determining the so-called equivalent coupling factor is presented. The validity of this method is demonstrated by numerical simulations of the vibration response of a master plate structure with fuzzy attachments. It is revealed that the method performs......Many complicated systems of practical interest consist basically of a well-defined outer shell-like master structure and a complicated internal structure with uncertain dynamic properties. Using the "fuzzy structure theory" for predicting audible frequency vibration, the internal structure is......-dimensional continuous boundary was examined in a companion paper (L. Friis and M. Ohlrich, "Vibration modeling of structural fuzzy with continuous boundary," J. Acoust. Soc. Am. 123, 718-728 (2008)). In the present paper, this method is extended, such that it allows modeling of fuzzy substructures with a two...
Institute of Scientific and Technical Information of China (English)
WANG Yuanzhan; HUA Leina; DONG Shaowei
2004-01-01
Vibrating, sliding and uplift rocking are three elementary motion types of caisson breakwaters. The dynamic model and the numerical simulation method of vibrating-sliding-uplift rocking coupled motion of caisson breakwaters are developed. The histories of displacement, rotation, sliding force and overturning moment of a caisson breakwater under the excitation of breaking wave impact are calculated for the motion models of vibrating, vibrating-sliding, vibrating-uplift rocking and vibrating-sliding-uplift rocking. The effects of various motion models on the stability of caisson breakwaters are investigated. The feasibility of the dynamic design idea that the sliding motion and the uplift rocking motion of caisson breakwaters are allowed under the excitation of breaking wave impact is discussed.
Lopes, Patrícia; Ruiz, Jésus Fernández; Alves Costa, Pedro; Medina Rodríguez, L; Cardoso, António Silva
2016-10-15
The present paper focuses on the experimental validation of a numerical approach previously proposed by the authors for the prediction of vibrations inside buildings due to railway traffic in tunnels. The numerical model is based on the concept of dynamic substructuring and is composed by three autonomous models to simulate the following main parts of the problem: i) generation of vibrations (train-track interaction); ii) propagation of vibrations (track-tunnel-ground system); iii) reception of vibrations (building coupled to the ground). The experimental validation consists in the comparison between the results predicted by the proposed numerical model and the measurements performed inside a building due to the railway traffic in a shallow tunnel located in Madrid. Apart from the brief description of the numerical model and of the case study, the main options and simplifications adopted on the numerical modeling strategy are discussed. The balance adopted between accuracy and simplicity of the numerical approach proved to be a path to follow in order to transfer knowledge to engineering practice. Finally, the comparison between numerical and experimental results allowed finding a good agreement between both, fact that ensures the ability of the proposed modeling strategy to deal with real engineering practical problems. PMID:26589136
Modeling the benefits of an artificial gravity countermeasure coupled with exercise and vibration
Goel, Rahul; Kaderka, Justin; Newman, Dava
2012-01-01
The current, system-specific countermeasures to space deconditioning have limited success with the musculoskeletal system in long duration missions. Artificial gravity (AG) that is produced by short radius centrifugation has been hypothesized as an effective countermeasure because it reintroduces an acceleration field in space; however, AG alone might not be enough stimuli to preserve the musculoskeletal system. A novel combination of AG coupled with one-legged squats on a vibrating platform may preserve muscle and bone in the lower limbs to a greater extent than the current exercise paradigm. The benefits of the proposed countermeasure have been analyzed through the development of a simulation platform. Ground reaction force data and motion data were collected using a motion capture system while performing one-legged and two-legged squats in 1-G. The motion was modeled in OpenSim, an open-source software, and inverse dynamics were applied in order to determine the muscle and reaction forces of lower limb joints. Vibration stimulus was modeled by adding a 20 Hz sinusoidal force of 0.5 body weight to the force plate data. From the numerical model in a 1-G acceleration field, muscle forces for quadriceps femoris, plantar flexors and glutei increased substantially for one-legged squats with vibration compared to one- or two-legged squats without vibration. Additionally, joint reaction forces for one-legged squats with vibration also increased significantly compared to two-legged squats with or without vibration. Higher muscle forces and joint reaction forces might help to stimulate muscle activation and bone modeling and thus might reduce musculoskeletal deconditioning. These results indicate that the proposed countermeasure might surpass the performance of the current space countermeasures and should be further studied as a method of mitigating musculoskeletal deconditioning.
Harmonic and Anharmonic Free Energies in Superlattices of Soft Particle Systems
Travesset, Alex; Calero, Carles; Knorowski, Chris
Many problems in self and directed assembly rely on the rigorous calculation of free energies. In systems of nanoparticles with capping ligands, for example, superlattices are found in closely competing structures, such as hcp/fcc, cubic/hexagonal diamond or those isomorphic between MgCu2 and MgZn2. With this motivation, we investigate a general method to calculate free energy of crystalline solids by considering the harmonic approximation and quasistatically switching the anharmonic contribution. The advantage of the method is that the harmonic approximation provides an already very accurate estimate of the free energy, and therefore the anharmonic term is numerically very small and can be determined to very high accuracy. We further show that the anharmonic contribution to the free energy satisfies a number of exact inequalities that place con- strains on its magnitude and allows approximate but fast and accurate estimates. We apply it to Lennard Jones sytems where we demonstrate that hcp is the equilibrium phase at low temperature and pressure and obtain the coexistence curve with the fcc phase, which exhibits reentrant behavior and binary systems that model nanoparticle superlattices with hydrocarbon capping ligand. The research was performed at the Ames Laboratory, which is operated for the US DOE by Iowa State University under Contract Number DE-AC02-07CH11358.
Meer, David W.; Lewandowski, Edward J.
2010-01-01
The U.S. Department of Energy (DOE), Lockheed Martin Corporation (LM), and NASA Glenn Research Center (GRC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. As part of the extended operation testing of this power system, the Advanced Stirling Convertors (ASC) at NASA GRC undergo a vibration test sequence intended to simulate the vibration history that an ASC would experience when used in an ASRG for a space mission. During these tests, a data system collects several performance-related parameters from the convertor under test for health monitoring and analysis. Recently, an additional sensor recorded the slip table position during vibration testing to qualification level. The System Dynamic Model (SDM) integrates Stirling cycle thermodynamics, heat flow, mechanical mass, spring, damper systems, and electrical characteristics of the linear alternator and controller. This Paper presents a comparison of the performance of the ASC when exposed to vibration to that predicted by the SDM when exposed to the same vibration.
Secondary flows enhance mixing in a model of vibration-assisted dialysis
Pitre, John; Mueller, Bruce; Lewis, Susan; Bull, Joseph
2014-11-01
Hemodialysis is an integral part of treatment for patients with end stage renal disease. While hemodialysis has traditionally been described as a diffusion-dominated process, recent in vitro work has shown that vibration of the dialyzer can enhance the clearance of certain solutes during treatment. We hypothesize that the addition of vibration generates secondary flows in the dialysate compartment. These flows, perpendicular to the longitudinal axis of the dialysis fibers, advect solute away from the fiber walls, thus maintaining a larger concentration gradient and enhancing diffusion. Using the finite element method, we simulated the flow of dialysate through a hexagonally-packed array of cylinders and the transport of solute away from the cylinder walls. The addition of vibration was modeled using sinusoidal body forces of various frequencies and amplitudes. Using the variance of the concentration field as a metric, we found that vibration improves mixing according to a power law dependency on frequency. We will discuss the implications of these computational results on our understanding of the in vitro experiments and propose optimal vibration patterns for improving clearance in dialysis treatments. This work was supported by the Michigan Institute for Clinical and Health Research and NIH Grant UL1TR000433.
International Nuclear Information System (INIS)
This paper presents the results of vibration tests of PWR core barrel model, which were performed in liquid flow of hydrodynamic testing circuit in symmetrical/asymmetrical flow conditions simulating 4 and 3 loop operations. The measurements of dynamic stresses and displacements were carried out, processed stochastically and analyzed by correlation techniques
Directory of Open Access Journals (Sweden)
Jialin Tian
2016-01-01
Full Text Available Comparative analysis whether considering the lateral inertia or not, aiming at the longitudinal vibration of the drill string in drilling progress, is proposed. In the light of the actual condition, the mechanical model of the drill string about vibration is established on the basis of the theoretical analysis. Longitudinal vibration equation of the drill string is derived from the Rayleigh-Love model and one-dimensional viscoelastic model. According to the Laplace transform method and the relationships among parameters of the model, the solutions to complex impedance at the bottom of the drill string are obtained, and then the comparison results are analyzed, which is the lateral inertia effect on longitudinal vibration characteristics. The researches show that the smaller the length of the drill string, the greater the cross-sectional area of the drill string, the greater the damping coefficient of bottom hole on the bottom of the drill string, and the more evident the effect on the dynamic stiffness of the drill string with lateral inertia effect. The Poisson ratio of the drill string only has some effects on it taking account of the lateral inertia effect, and the influence is relatively small compared with the former three conditions.
Static and Vibration Analyses of General Wing Structures Using Equivalent Plate Models
Kapania, Rakesh K.; Liu, Youhua
1999-01-01
An efficient method, using equivalent plate model, is developed for studying the static and vibration analyses of general built-up wing structures composed of skins, spars, and ribs. The model includes the transverse shear effects by treating the built-up wing as a plate following the Reissner-Mindlin theory, the so-called First-order Shear Deformation Theory (FSDT). The Ritz method is used with the Legendre polynomials being employed as the trial functions. This is in contrast to previous equivalent plate model methods which have used simple polynomials, known to be prone to numerical ill-conditioning, as the trial functions. The present developments are evaluated by comparing the results with those obtained using MSC/NASTRAN, for a set of examples. These examples are: (i) free-vibration analysis of a clamped trapezoidal plate with (a) uniform thickness, and (b) non-uniform thickness varying as an airfoil, (ii) free-vibration and static analyses (including skin stress distribution) of a general built-up wing, and (iii) free-vibration and static analyses of a swept-back box wing. The results obtained by the present equivalent plate model are in good agreement with those obtained by the finite element method.
International Nuclear Information System (INIS)
This paper states a methodology for using a Modular Artificial Neural Network (ANN) in modeling the vibration monitoring of the Steam Turbine (ST) in Nuclear Power Plant (NPP). The input and the output signals of the vibration transducer are used as a source of the training data for the neural network model. The type of the network used in this methodology is the supervised Multilayer Feed-Forward Neural Networks with the Back-Propagation (BP) algorithm. The module architecture is according to the Human Factors (HF) Considerations in designing the Human-System Interface (HSI). The Vibration Severity limits are determined by the International Organization for Standardization (ISO) 10816. The model also contained 2 out of 3 voting and dynamic trip limit value ANNs. The results show that the proposed Modular ANN has good generalization capability to monitor and protect the machine from the Vibration Severity, increasing the reliability of (ST), and good HSI. This modeling methodology can be used for the other non-redundant components in NPP such as Reactor Coolant Pump (RCP)
Stochastic Response of Energy Balanced Model for Vortex-Induced Vibration
DEFF Research Database (Denmark)
Nielsen, Søren R.K.; Krenk, S.
A double oscillator model for vortex-induced oscillations of structural elements based on exact power exchange between fluid and structure, recently proposed by authors, is extended to include the effect of the turbulent component of the wind. In non-turbulent flow vortex-induced vibrations of li...
Fractal Theory and Contact Dynamics Modeling Vibration Characteristics of Damping Blade
Directory of Open Access Journals (Sweden)
Ruishan Yuan
2014-01-01
Full Text Available The contact surface structure of dry friction damper is complicate, irregular, and self-similar. In this paper, contact surface structure is described with the fractal theory and damping blade is simplified as 2-DOF cantilever beam model with lumped masses. By changing the position of the damper, lacing and shroud structure are separately simulated to study vibration absorption effect of damping blade. The results show that both shroud structure and lacing could not only dissipate energy but also change stiffness of blade. Under the same condition of normal pressure and contact surface, the damping effect of lacing is stronger than that of shroud structure. Meanwhile, the effect on changing blade stiffness of shroud structure is stronger than that of lacing. This paper proposed that there is at least one position of the blade, at which the damper dissipates the most vibration energy during a vibration cycle.
The experimental validation of a numerical model for the prediction of railway induced vibrations
Lombaert, Geert; Degrande, Geert; Kogut, J.; François, Stijn
2006-01-01
This paper presents the experimental validation of a numerical model for the prediction of train induced vibrations. The model fully accounts for the dynamic interaction between the train, the track and the soil. The track geometry is assumed to be invariant with respect to the longitudinal direction, which allows for an efficient solution of the dynamic track-soil interaction problem in the frequency-wavenumber domain. The model is validated by means of several experiments that have been per...
A study of neutron noise physical model for in core vibration
International Nuclear Information System (INIS)
It is important to monitor in core vibration with the neutron noise method. The perturbed theory (system equation and perturbed noise source), control theory (transfer function) and the reactor dynamics (point kinetic equations) have been used to build the physical model. The model has been used to interpret the power spectral density of the zero power reactor simulated experiment. In the model, a low frequency noise term has been introduced to describe the abnormal increase of low frequency part of PSD curve
Kuo, K. A.; Verbraken, H.; Degrande, G.; Lombaert, G.
2016-07-01
Along with the rapid expansion of urban rail networks comes the need for accurate predictions of railway induced vibration levels at grade and in buildings. Current computational methods for making predictions of railway induced ground vibration rely on simplifying modelling assumptions and require detailed parameter inputs, which lead to high levels of uncertainty. It is possible to mitigate against these issues using a combination of field measurements and state-of-the-art numerical methods, known as a hybrid model. In this paper, two hybrid models are developed, based on the use of separate source and propagation terms that are quantified using in situ measurements or modelling results. These models are implemented using term definitions proposed by the Federal Railroad Administration and assessed using the specific illustration of a surface railway. It is shown that the limitations of numerical and empirical methods can be addressed in a hybrid procedure without compromising prediction accuracy.
Rakheja, S; Gurram, R; Gouw, G J
1993-10-01
Hand-arm vibration (HAV) models serve as an effective tool to assess the vibration characteristics of the hand-tool system and to evaluate the attenuation performance of vibration isolation mechanisms. This paper describes a methodology to identify the parameters of HAV models, whether linear or nonlinear, using mechanical impedance data and a nonlinear programming based optimization technique. Three- and four-degrees-of-freedom (DOF) linear, piecewise linear and nonlinear HAV models are formulated and analyzed to yield impedance characteristics in the 5-1000 Hz frequency range. A local equivalent linearization algorithm, based upon the principle of energy similarity, is implemented to simulate the nonlinear HAV models. Optimization methods are employed to identify the model parameters, such that the magnitude and phase errors between the computed and measured impedance characteristics are minimum in the entire frequency range. The effectiveness of the proposed method is demonstrated through derivations of models that correlate with the measured X-axis impedance characteristics of the hand-arm system, proposed by ISO. The results of the study show that a linear model cannot predict the impedance characteristics in the entire frequency range, while a piecewise linear model yields an accurate estimation. PMID:8253830
Quantum versus semiclassical description of selftrapping: anharmonic effects
International Nuclear Information System (INIS)
Selftrapping has been traditionally studied on the assumption that quasiparticles interact with harmonic phonons and that this interaction is linear in the displacement of the phonon. To complement recent semiclassical studies of anharmonicity and nonlinearity in this context, we present below a fully quantum mechanical analysis of a two-site system, where the oscillator is described by a tunably anharmonic potential, with a square well with infinite walls and the harmonic potential as its extreme limits, and wherein the interaction is nonlinear in the oscillator displacement. We find that even highly anharmonic polarons behave similar to their harmonic counterparts in that selftrapping is preserved for long times in the limit of strong coupling, and that the polaronic tunneling time scale depends exponentially on the polaron binding energy. Further, in agreement with earlier results related to harmonic polarons, the semiclassical approximation agrees with the full quantum result in the massive oscillator limit of small oscillator frequency and strong quasiparticle-oscillator coupling. (author)
Rahmouni, A.; Beidouri, Z.; Benamar, R.
2013-09-01
The purpose of the present paper was the development of a physically discrete model for geometrically nonlinear free transverse constrained vibrations of beams, which may replace, if sufficient degrees of freedom are used, the previously developed continuous nonlinear beam constrained vibration models. The discrete model proposed is an N-Degrees of Freedom (N-dof) system made of N masses placed at the ends of solid bars connected by torsional springs, presenting the beam flexural rigidity. The large transverse displacements of the bar ends induce a variation in their lengths giving rise to axial forces modelled by longitudinal springs. The calculations made allowed application of the semi-analytical model developed previously for nonlinear structural vibration involving three tensors, namely the mass tensor mij, the linear rigidity tensor kij and the nonlinearity tensor bijkl. By application of Hamilton's principle and spectral analysis, the nonlinear vibration problem is reduced to a nonlinear algebraic system, examined for increasing numbers of dof. The results obtained by the physically discrete model showed a good agreement and a quick convergence to the equivalent continuous beam model, for various fixed boundary conditions, for both the linear frequencies and the nonlinear backbone curves, and also for the corresponding mode shapes. The model, validated here for the simply supported and clamped ends, may be used in further works to present the flexural linear and nonlinear constrained vibrations of beams with various types of discontinuities in the mass or in the elasticity distributions. The development of an adequate discrete model including the effect of the axial strains induced by large displacement amplitudes, which is predominant in geometrically nonlinear transverse constrained vibrations of beams [1]. The investigation of the results such a discrete model may lead to in the case of nonlinear free vibrations. The development of the analogy between the
Directory of Open Access Journals (Sweden)
Z.A. Stotsko
2007-09-01
Full Text Available Purpose: The objective of this work is to develop the principles of the theoretical investigation of vibration volumetric treatment for the surfaces of articles manufactured by friable dry medium and to create the method for choice and optimization of machine parameters.Design/methodology/approach: Theoretical investigations are based on using the analytic methods of theory of non-linear oscillations and asymptotic methods of solving non-linear differential equations for describing dynamic processes of volumetric vibration treatment. Experimental investigations of dynamic processes that take place in the vibromachines were carried out with using the computer and vibration measuring system.Findings: Complex non-linear mathematic model of the system “vibromachine – treating medium” is created. Due to their non-linearity, models of such kind are adequate to real situation of vibrotreatment, they can also be applied in investigation of dynamics of the vibromachine and its medium.Research limitations/implications: Processes of vibration volumetric treatment need additional investigations.Practical implications: The obtained complex mathematical model of the system “vibromachine – trading medium” enables us to analytically determine the influence of its parameters upon the intensity of articles treatment in it according to the chosen criterion; thus it saves us from carrying out time taking cumbersome experiments both for designing a vibromachine and for selecting modes of treating articles in it.Originality/value: The new approach to the investigations of volumetric vibration treatment by means non-linear mathematic model of the system “vibromachine – treating medium” have been shown.
Vibrational Heat Transport in Molecular Junctions
Segal, Dvira; Agarwalla, Bijay Kumar
2016-05-01
We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules.
Vibrational Heat Transport in Molecular Junctions.
Segal, Dvira; Agarwalla, Bijay Kumar
2016-05-27
We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules. PMID:27215814
A modeling and vibration analysis of a piezoelectric micro-pump diaphragm
Kaviani, Samira; Bahrami, Mohsen; Esfahani, Amir Monemian; Parsi, Behzad
2014-12-01
The vibration analysis of a micro-pump diaphragm is presented. A piezoelectric micro-pump is studied. For this purpose, a dynamic model of the micro-pump is derived. The micro-pump diaphragm is modeled as circular double membranes, a piezoelectric one as actuator and a silicon one for representing the membrane for pumping action. The damping effect of the fluid is introduced into the equations. Vibration analysis is established by explicitly solving the dynamic model. The natural frequencies and mode shapes are calculated. The orthogonality conditions of the system are discussed. To verify the results, the finite-element micro-pump model is developed in ANSYS software package. The results show that the two methods are well comparable.
Adaptive Neuro-Fuzzy Modeling of UH-60A Pilot Vibration
Kottapalli, Sesi; Malki, Heidar A.; Langari, Reza
2003-01-01
Adaptive neuro-fuzzy relationships have been developed to model the UH-60A Black Hawk pilot floor vertical vibration. A 200 point database that approximates the entire UH-60A helicopter flight envelope is used for training and testing purposes. The NASA/Army Airloads Program flight test database was the source of the 200 point database. The present study is conducted in two parts. The first part involves level flight conditions and the second part involves the entire (200 point) database including maneuver conditions. The results show that a neuro-fuzzy model can successfully predict the pilot vibration. Also, it is found that the training phase of this neuro-fuzzy model takes only two or three iterations to converge for most cases. Thus, the proposed approach produces a potentially viable model for real-time implementation.
A microscopic nuclear collective rotation-vibration model: 2D submodel
Gulshani, Parviz
2016-01-01
The previous microscopic collective rotation-vibration model is improved to include interaction between collective oscillations in a pair of spatial directions, and to remove many of the previous-model approximations. As in the previous model, the nuclear Schrodinger equation (instead of the Hamiltonian) is canonically transformed to obtain a Schrodinger equation for collective rotation and vibration of a nucleus coupled to an intrinsic motion, with the related constraints imposed on the wavefunction (rather than on the particle co-ordinates). The resulting equation is then effectively linearized into three self-consistent, time-reversal invariant, cranking-type equations using a variational method. The relation of the equations to the phenomenological hydrodynamic collective Bohr-Davydov-Faessler-Greiner model is discussed. To facilitate the solution of the equations and enhance physical insight, we consider in this article the collective oscillations in only two space directions. For harmonic oscillator mea...
Vibration modelling and analysis of piezoelectric energy harvesters
Mak, Kuok Hang
2011-01-01
The performance of piezoelectric cantilever beam energy harvesters subjected to base excitation is considered in this work. Based on the linear assumption, a theoretical model is developed to predict the mechanical and electrical responses of the harvester and in comparison to other theoretical models, more accurate mode shape functions are used for the structural part of the harvester. The model is validated against experimental measurements and parameter studies are carried out to investiga...
Adaptive Model Predictive Vibration Control of a Cantilever Beam with Real-Time Parameter Estimation
Directory of Open Access Journals (Sweden)
Gergely Takács
2014-01-01
Full Text Available This paper presents an adaptive-predictive vibration control system using extended Kalman filtering for the joint estimation of system states and model parameters. A fixed-free cantilever beam equipped with piezoceramic actuators serves as a test platform to validate the proposed control strategy. Deflection readings taken at the end of the beam have been used to reconstruct the position and velocity information for a second-order state-space model. In addition to the states, the dynamic system has been augmented by the unknown model parameters: stiffness, damping constant, and a voltage/force conversion constant, characterizing the actuating effect of the piezoceramic transducers. The states and parameters of this augmented system have been estimated in real time, using the hybrid extended Kalman filter. The estimated model parameters have been applied to define the continuous state-space model of the vibrating system, which in turn is discretized for the predictive controller. The model predictive control algorithm generates state predictions and dual-mode quadratic cost prediction matrices based on the updated discrete state-space models. The resulting cost function is then minimized using quadratic programming to find the sequence of optimal but constrained control inputs. The proposed active vibration control system is implemented and evaluated experimentally to investigate the viability of the control method.
Krajnak, Kristine; Raju, Sandya G; Miller, G Roger; Johnson, Claud; Waugh, Stacey; Kashon, Michael L; Riley, Danny A
2016-01-01
Repeated exposure to hand-transmitted vibration through the use of powered hand tools may result in pain and progressive reductions in tactile sensitivity. The goal of the present study was to use an established animal model of vibration-induced injury to characterize changes in sensory nerve function and cellular mechanisms associated with these alterations. Sensory nerve function was assessed weekly using the current perception threshold test and tail-flick analgesia test in male Sprague-Dawley rats exposed to 28 d of tail vibration. After 28 d of exposure, Aβ fiber sensitivity was reduced. This reduction in sensitivity was partly attributed to structural disruption of myelin. In addition, the decrease in sensitivity was also associated with a reduction in myelin basic protein and 2',3'- cyclic nucleotide phosphodiasterase (CNPase) staining in tail nerves, and an increase in circulating calcitonin gene-related peptide (CGRP) concentrations. Changes in Aβ fiber sensitivity and CGRP concentrations may serve as early markers of vibration-induced injury in peripheral nerves. It is conceivable that these markers may be utilized to monitor sensorineural alterations in workers exposed to vibration to potentially prevent additional injury. PMID:26852665
Three-dimensional finite element modelling of vocal folds vibration in thehuman larynx
Czech Academy of Sciences Publication Activity Database
Vampola, T.; Horáček, Jaromír; Klepáček, I.
Firenze : Firenze University Press, 2007 - (Manfredi, C.), s. 44-46 ISBN 978-88-8453-674-7. [Models and analysis of vocal emissions for biomedical applications /5th International workshop/. Firenze (IT), 13.12.2007-15.12.2007] R&D Projects: GA AV ČR IAA2076401 Institutional research plan: CEZ:AV0Z20760514 Keywords : biomechanics of human voice * parametric FE model of the human larynx * numerical simulation of the vocal folds vibration Subject RIV: BI - Acoustics
Response prediction for large scale model structure under forced vibration test
International Nuclear Information System (INIS)
This paper presents the analytical prediction for the responses of the forced vibration test on a quarter-scale containment model structure built at Hualien, Taiwan. The prediction is performed blindly by using the computer program HASSI-8 which is developed for solving the soil-structure interaction problem using the method of hybrid modeling. The results obtained show very good correlation with the field test results
Vibration modeling of sandwich structures using solid-shell finite elements
KPEKY, Fessal; Boudaoud, Hakim; Chalal, Hocine; ABED-MERAIM, Farid; Daya, El Mostafa
2014-01-01
The aim of this work is to propose a new finite element modeling for vibration of sandwich structures with soft core. Indeed, several approaches have been adopted in the literature to accurately model these types of structures, but show some limitations in certain configurations of high contrast of material properties or geometric aspect ratios between the different layers. In these situations, it is generally well-known that the use of higher-order or three-dimensional finite elements is mor...
Modeling study of vibrational photochemical isotope enrichment. [HBr + Cl/sub 2/; HCl + Br/sub 2/
Energy Technology Data Exchange (ETDEWEB)
Badcock, C.C.; Hwang, W.C.; Kalsch, J.F.
1978-09-29
Chemical kinetic modeling studies of vibrational-photochemical isotope enrichment have been performed on two systems: Model (I), H/sup 79/Br(H/sup 81/Br) + Cl/sub 2/ and, Model (II), H/sup 37/Cl(H/sup 35/Cl) + Br. Pulsed laser excitation was modeled to the first excited vibrational level of H/sup 79/Br in Model I and the first and second excited vibrational levels of both HCl isotopes in Model II. These are prototype systems of exoergic (Model I) and endoergic (Model II) reactions. The effects on enrichment of varying the external parameters (pressure, laser intensity) and the internal parameters (rate constants for V-V exchange and excited-state reactions) were examined. Studies of these prototype systems indicate that a favorable reaction for enrichment, with isotopically-specific excitation and a significantly accelerated vibrationally-excited-state reaction should have the following properties: the reaction from v = 0 should be only moderately exoergic, and the most favorable coreactant should be a polyatomic species, such as alkyl radical. Direct excitation of the reacting vibrational level is at least an order of magnitude more favorable for enrichment than is population by energy transfer. Enrichment of the minor isotope by these processes is more effective than is major isotope enrichment. Within limits, increased laser intensity is beneficial. However, for sequential excitation of a second vibrational level, major isotope enrichment can be diminished by high populations of the first vibrational level.
Diagrammatic Vibrational Coupled-Cluster
Faucheaux, Jacob A.; Hirata, So
2015-06-01
A diagrammatic vibrational coupled-cluster method for calculation of zero-point energies and an equation-of-motion coupled-cluster method for calculation of anharmonic vibrational frequencies are developed. The methods, which we refer to as XVCC and EOM-XVCC respectively, rely on the size-extensive vibrational self-consistient field (XVSCF) method for reference wave functions. The methods retain the efficiency advantages of XVSCF making them suitable for applications to large molecules and solids, while they are numerically shown to accurately predict zero-point energies and frequencies of small molecules as well. In particular, EOM-XVCC is shown to perform well for modes which undergo Fermi resonance where traditional perturbative methods fail. Rules for the systematic generation and interpretation of the XVCC and EOM-XVCC diagrams to any order are presented.
Directory of Open Access Journals (Sweden)
Lezin Seba MINSILI
2013-11-01
Full Text Available The purpose of this research paper was to assess and predict the effect of vibrations induced by an underground railway on nearby-existing buildings prior to the construction of projected new railway lines of the National Railway Master Plan of Cameroon and after upgrading of the railway conceded to CAMRAIL linking the two most densely populated cities of Cameroon: Douala and Yaoundé. With the source-transmitter-receiver mathematical model as the train-soil-structure interaction model, taking into account sub-model parameters such as type of the train-railway system, typical geotechnical conditions of the ground and the sensitivity of the nearby buildings, the analysis is carried out over the entire system using the dynamic finite element method in the time domain. This subdivision of the model is a powerful tool that allows to consider different alternatives of sub-models with different characteristics, and thus to determine any critical excessive vibration impact. Based on semi-empirical analytical results obtained from presented models, the present work assesses and predicts characteristics of traffic-induced vibrations as a function of time duration, intensity and vehicle speed, as well as their influence on buildings at different levels.
De Marco, Luigi; Fournier, Joseph A; Thämer, Martin; Carpenter, William; Tokmakoff, Andrei
2016-09-01
Water's extended hydrogen-bond network results in rich and complex dynamics on the sub-picosecond time scale. In this paper, we present a comprehensive analysis of the two-dimensional infrared (2D IR) spectrum of O-H stretching vibrations in liquid H2O and their interactions with bending and intermolecular vibrations. By exploring the dependence of the spectrum on waiting time, temperature, and laser polarization, we refine our molecular picture of water's complex ultrafast dynamics. The spectral evolution following excitation of the O-H stretching resonance reveals vibrational dynamics on the 50-300 fs time scale that are dominated by intermolecular delocalization. These O-H stretch excitons are a result of the anharmonicity of the nuclear potential energy surface that arises from the hydrogen-bonding interaction. The extent of O-H stretching excitons is characterized through 2D depolarization measurements that show spectrally dependent delocalization in agreement with theoretical predictions. Furthermore, we show that these dynamics are insensitive to temperature, indicating that the exciton dynamics alone set the important time scales in the system. Finally, we study the evolution of the O-H stretching mode, which shows highly non-adiabatic dynamics suggestive of vibrational conical intersections. We argue that the so-called heating, commonly observed within ∼1 ps in nonlinear IR spectroscopy of water, is a nonequilibrium state better described by a kinetic temperature rather than a Boltzmann distribution. Our conclusions imply that the collective nature of water vibrations should be considered in describing aqueous solvation. PMID:27608998
Advances in simulated modeling of vibration systems based on computational intelligence
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Computational intelligence is the computational simulation of the bio-intelligence, which includes artificial neural networks, fuzzy systems and evolutionary computations. This article summarizes the state of the art in the field of simulated modeling of vibration systems using methods of computational intelligence, based on some relevant subjects and the authors' own research work. First, contributions to the applications of computational intelligence to the identification of nonlinear characteristics of packaging are reviewed. Subsequently, applications of the newly developed training algorithms for feedforward neural networks to the identification of restoring forces in multi-degree-of-freedom nonlinear systems are discussed. Finally, the neural-network-based method of model reduction for the dynamic simulation of microelectromechanical systems (MEMS) using generalized Hebbian algorithm (GHA) and robust GHA is outlined. The prospects of the simulated modeling of vibration systems using techniques of computational intelligence are also indicated.
Optomechanical self-oscillations in an anharmonic potential: engineering a nonclassical steady state
Grimm, Manuel; Bruder, Christoph; Lörch, Niels
2016-09-01
We study self-oscillations of an optomechanical system, where coherent mechanical oscillations are induced by a driven optical or microwave cavity, for the case of an anharmonic mechanical oscillator potential. A semiclassical analytical model is developed to characterize the limit cycle for large mechanical amplitudes corresponding to a weak nonlinearity. As a result, we predict conditions to achieve subpoissonian phonon statistics in the steady state, indicating classically forbidden behavior. We compare with numerical simulations and find very good agreement. Our model is quite general and can be applied to other physical systems such as trapped ions or superconducting circuits.
Modeling and experimental vibration analysis of nanomechanical cantilever active probes
International Nuclear Information System (INIS)
Nanomechanical cantilever (NMC) active probes have recently received increased attention in a variety of nanoscale sensing and measurement applications. Current modeling practices call for a uniform cantilever beam without considering the intentional jump discontinuities associated with the piezoelectric layer attachment and the NMC cross-sectional step. This paper presents a comprehensive modeling framework for modal characterization and dynamic response analysis of NMC active probes with geometrical discontinuities. The entire length of the NMC is divided into three segments of uniform beams followed by applying appropriate continuity conditions. The characteristics matrix equation is then used to solve for system natural frequencies and mode shapes. Using an equivalent electromechanical moment of a piezoelectric layer, forced motion analysis of the system is carried out. An experimental setup consisting of a commercial NMC active probe from Veeco and a state-of-the-art microsystem analyzer, the MSA-400 from Polytec, is developed to verify the theoretical developments proposed here. Using a parameter estimation technique based on minimizing the modeling error, optimal values of system parameters are identified. Mode shapes and the modal frequency response of the system for the first three modes determined from the proposed model are compared with those obtained from the experiment and commonly used theory for uniform beams. Results indicate that the uniform beam model fails to accurately predict the actual system response, especially in multiple-mode operation, while the proposed discontinuous beam model demonstrates good agreement with the experimental data. Such detailed and accurate modeling framework can lead to significant enhancement in the sensitivity of piezoelectric-based NMC sensors for use in variety of sensing and imaging applications
Modeling of plasma-based CO2 conversion: lumping of the vibrational levels
Berthelot, Antonin; Bogaerts, Annemie
2016-08-01
Although CO2 conversion by plasma technology is gaining increasing interest, the underlying mechanisms for an energy-efficient process are still far from understood. In this work, a reduced non-equilibrium CO2 plasma chemistry set, based on level lumping of the vibrational levels, is proposed and the reliability of this level-lumping method is tested by a self-consistent zero-dimensional code. A severe reduction of the number of equations to be solved is achieved, which is crucial to be able to model non-equilibrium CO2 plasmas by 2-dimensional models. Typical conditions of pressure and power used in a microwave plasma for CO2 conversion are investigated. Several different sets, using different numbers of lumped groups, are considered. The lumped models with 1, 2 or 3 groups are able to reproduce the gas temperature, electron density and electron temperature profiles, as calculated by the full model treating all individual excited levels, in the entire pressure range investigated. Furthermore, a 3-groups model is also able to reproduce the shape of the vibrational distribution function (VDF) and gives the most reliable prediction of the CO2 conversion. A strong influence of the vibrational excitation on the plasma characteristics is observed. Finally, the limitations of the lumped-levels method are discussed.
Kinetic model for the vibrational energy exchange in flowing molecular gas mixtures. Ph.D. Thesis
Offenhaeuser, F.
1987-01-01
The present study is concerned with the development of a computational model for the description of the vibrational energy exchange in flowing gas mixtures, taking into account a given number of energy levels for each vibrational degree of freedom. It is possible to select an arbitrary number of energy levels. The presented model uses values in the range from 10 to approximately 40. The distribution of energy with respect to these levels can differ from the equilibrium distribution. The kinetic model developed can be employed for arbitrary gaseous mixtures with an arbitrary number of vibrational degrees of freedom for each type of gas. The application of the model to CO2-H2ON2-O2-He mixtures is discussed. The obtained relations can be utilized in a study of the suitability of radiation-related transitional processes, involving the CO2 molecule, for laser applications. It is found that the computational results provided by the model agree very well with experimental data obtained for a CO2 laser. Possibilities for the activation of a 16-micron and 14-micron laser are considered.
Vibrational and electronic collisional-radiative model in air for Earth entry problems
International Nuclear Information System (INIS)
The two-temperature collisional-radiative model CoRaM-AIR, working over a wide range for pressure and temperatures, has been developed for the flow conditions around a space vehicle entering the Earth's atmosphere. The species N2, O2, NO, N, O, Ar, N2+, O2+, NO+, N+, O+, Ar+, and free electrons are taken into account. The model is vibrationally specific on the ground electronic state of N2, O2, and NO, and electronically specific for all species, with a total of 169 vibrational states and 829 electronic states, respectively. A wide set of elementary processes is considered under electron and heavy particle impact given the temperatures involved (up to 30 000 K). This set corresponds to almost 700 000 forward and backward elementary processes. The relaxation from initial thermal or chemical nonequilibrium is studied for dissociation-ionization situations in conditions related to the FIRE II flight experiment. Boltzmann plots clearly prove that the vibrational and electronic excitation distributions are far from being Boltzmanian. In particular, high-lying vibrational levels remain underpopulated for most of the duration of the relaxation. This relaxation can be separated in a first phase characterized by the dissociation and the excitation of the molecular species, and a second phase leading to the excitation and the ionization of the dissociation products. Owing to the vibrational relaxation, the time scales are slightly higher than the ones predicted by former kinetic mechanisms usually used in flow simulations. In the present FIRE II conditions, radiation does not play a significant role
Transient Two-Dimensional Infrared Spectroscopy in a Vibrational Ladder.
Kemlin, Vincent; Bonvalet, Adeline; Daniault, Louis; Joffre, Manuel
2016-09-01
We report on transient 2D Fourier transform infrared spectroscopy (2DIR) after vibrational ladder climbing induced in the CO-moiety longitudinal stretch of carboxyhemoglobin. The population distribution, spreading up to seven vibrational levels, results in a nonequilibrium 2DIR spectrum evidencing a large number of peaks that can be easily attributed to individual transitions thanks to the anharmonicity of the vibrational potential. We discuss the physical origin of the observed peaks as well as the qualitative behavior of the subsequent dynamics governed by population relaxation in the vibrational ladder. PMID:27508408
Modeling and Tuning for Vibration Energy Harvesting using a Piezoelectric Bimorph
Cao, Yongqing
With the development of wireless sensors and other devices, the need for continuous power supply with high reliability is growing ever more. The traditional battery power supply has the disadvantage of limited duration of continuous power supply capability so that replacement for new batteries has to be done regularly. This can be quite inconvenient and sometimes quite difficult especially when the sensors are located in places not easily accessible such as the inside of a machine or wild field. This situation stimulates the development of renewable power supply which can harvest energy from the environment. The use of piezoelectric materials to converting environment vibration to electrical energy is one of the alternatives of which a broad range of research has been done by many researchers, focusing on different issues. The improvement of efficiency is one of the most important issues in vibration based energy harvesting. For this purpose different methods are devised and more accurate modeling of coupled piezoelectric mechanical systems is investigated. In the current paper, the research is focused on improving voltage generation of a piezoelectric bimorph on a vibration beam, as well as the analytical modeling of the same system. Also an initial study is conducted on the characteristics of the vibration of Zinc oxide (ZnO) nanowire, which is a promising material for its coupled semiconducting and piezoelectric properties. The effect on the voltage generation by different placement of the piezoelectric bimorph on the vibrating beam is investigated. The relation between the voltage output and the curvature is derived which is used to explain the effect of placement on voltage generation. The effect of adding a lumped mass on the modal frequencies of the beam and on the curvature distribution is investigated. The increased voltage output from the piezoelectric bimorph by using appropriately selected mass is proved analytically and also verified by experiment. For
Vibrations of turbine blades bundles model with rubber damping elements
Czech Academy of Sciences Publication Activity Database
Půst, Ladislav; Pešek, Luděk
2014-01-01
Roč. 21, č. 1 (2014), s. 45-52. ISSN 1802-1484 R&D Projects: GA ČR GA101/09/1166 Institutional support: RVO:61388998 Keywords : mathematical model * bundle of five blades * rubber damping elements * eigenmodes Subject RIV: BI - Acoustics http://www.engineeringmechanics.cz/obsahy.html?R=21&C=1
Yan, Su
2007-12-01
To improve the fuel consumption of a satellite, maintain the position and orientation and eliminate the unwanted thruster vibration, intelligent composite structure technology was proposed in the ADPICAS (Adaptive Damping and Positioning using Intelligent Composite Active Structures) project funded by the ONR (Office of Naval Research) in collaboration with the NRL (Naval Research Laboratory) in 2000. This dissertation introduces the author's research achievements in developing smart composite panels for the ADPICAS project, including modeling, actuator optimization, and vibration control. The method of separation of variables is presented to derive the analytical shape functions for complex composite structures with asymmetric constraints, i.e., the 2-D Adaptive Composite Circular Plate (ACCP) in cylindrical coordinates and the 3-D Adaptive Composite Satellite Dish (ACSD) in spherical coordinates. Following these solutions, two modeling approaches are developed to obtain the models of adaptive composite panels including an adaptive composite beam, the ACCP, and the ACSD. One model approach is to employ the Lagrange-Rayleigh-Ritz method based on the developed analytical shape functions. Meanwhile, the transfer function estimation technique, combining the finite element analyses, is applied to obtain the numerical model of the composite panels. Aiming at improving the actuation efficiency, a Genetic Algorithm is presented to optimize the piezoelectric actuator placement on the composite panels. Taking the inertia and stiffness characteristics of the piezoelectric actuators into account, this algorithm defines the performance index as a weighted summation of control error and control energy consumption, and obtained the optimal solution that minimizes the performance index. Furthermore, an adaptive disturbance observer/feed-forward (ADOB/FF) controller is proposed to achieve simultaneous precision positioning and vibration suppression of the adaptive composite panels
Contribution to mathematical modeling of drive parasitic vibration
Czech Academy of Sciences Publication Activity Database
Kratochvíl, Ctirad; Kalous, J.; Kotek, Vladimír
Praha: Ústav termomechaniky AV ČR, 2000 - (Dobiáš, I.), s. 117-120 ISBN 80-85918-54-4. [National colloquium with international participation Dynamics of machines 2000.. Praha (CZ), 08.02.2000-09.02.2000] R&D Projects: GA ČR GA101/98/0972; GA MŠk VS96122 Keywords : dynamic system * mathematical modeling Subject RIV: BI - Acoustics
Modelling of the vibration properties of the human vocal folds
Czech Academy of Sciences Publication Activity Database
Vampola, T.; Horáček, Jaromír; Klepáček, I.
Praha: Institute of Thermomechanics AS CR, v. v. i., 2007 - (Zolotarev, I.), s. 305-406 ISBN 978-80-87012-06-2. [Engineering Mechanics 2007: national conference with international participation. Svratka (CZ), 14.05.2007-17.05.2007] R&D Projects: GA AV ČR IAA2076401 Institutional research plan: CEZ:AV0Z20760514 Keywords : biomechanics of voice * FE model Subject RIV: BI - Acoustics
Fuzzy Model-based Pitch Stabilization and Wing Vibration Suppression of Flexible Wing Aircraft.
Ayoubi, Mohammad A.; Swei, Sean Shan-Min; Nguyen, Nhan T.
2014-01-01
This paper presents a fuzzy nonlinear controller to regulate the longitudinal dynamics of an aircraft and suppress the bending and torsional vibrations of its flexible wings. The fuzzy controller utilizes full-state feedback with input constraint. First, the Takagi-Sugeno fuzzy linear model is developed which approximates the coupled aeroelastic aircraft model. Then, based on the fuzzy linear model, a fuzzy controller is developed to utilize a full-state feedback and stabilize the system while it satisfies the control input constraint. Linear matrix inequality (LMI) techniques are employed to solve the fuzzy control problem. Finally, the performance of the proposed controller is demonstrated on the NASA Generic Transport Model (GTM).
A Grey Prediction Model on Vibration Severity Development of a Pump
Institute of Scientific and Technical Information of China (English)
ZHAO Rong-zhen; ZHANG You-yun
2004-01-01
The method to enhance the precision of a grey model GM ( 1, 1 ) for predicting the development of vibration severity of a pump is investigated. The rectifying procedures involve the strtcture and the parameters regarding GM( 1,1 ). A new model based on GM ( 1, 1 ), which is GM ( E, 1,1 ), is proposed. In GM(E, 1, 1), the distribution of relative errors ratios between the original series and predicting series obtained by the mean of GM( 1,1 ) are considered in special points to set up the threshold and adjusting coefficients to control the modified action and the rectified amount based on distribution of the original series.The case shows that GM(E, 1, 1 ) is good at predicting the vibration severity development of the pump.
Modeling and control of flow-induced vibrations of a flexible hydrofoil in viscous flow
Caverly, Ryan James; Li, Chenyang; Chae, Eun Jung; Forbes, James Richard; Young, Yin Lu
2016-06-01
In this paper, a reduced-order model (ROM) of the flow-induced vibrations of a flexible cantilevered hydrofoil is developed and used to design an active feedback controller. The ROM is developed using data from high-fidelity viscous fluid-structure interaction (FSI) simulations and includes nonlinear terms to accurately capture the effect of lock-in. An active linear quadratic Gaussian (LQG) controller is designed based on a linearization of the ROM and is implemented in simulation with the ROM and the high-fidelity viscous FSI model. A controller saturation method is also presented that ensures that the control force applied to the system remains within a prescribed range. Simulation results demonstrate that the LQG controller successfully suppresses vibrations in both the ROM and viscous FSI simulations using a reasonable amount of control force.
Torsional vibrations of helically buckled drill-strings: experiments and FE modelling
Kapitaniak, M.; Hamaneh, V. V.; Wiercigroch, M.
2016-05-01
This paper presents investigations of a complex drill-string vibrations on a novel experimental rig, developed by the Centre for Applied Dynamics Research at the University of Aberdeen. The rig is capable of exhibiting of all major types of drill-string vibrations, including torsional, axial and lateral modes. The importance of this work lies in the fact, that the experimental rig utilizes real industrial drill-bits and rock samples, which after careful identification of Torque On Bit (TOB) speed curves, allows to use an equivalent friction model to accommodate for both frictional and cutting components of the bit-rock interactions. Moreover, the proposed Finite Element model, after a careful calibration, is capable of replicating experimental results, for the prebuckled configuration of the drill-string. This allows us to observe the effect of winding and unwinding of the helical deformation during stick-slip motion.
Vibration tests on some models of PEC reactor core elements
International Nuclear Information System (INIS)
This paper describes the aims of the experimental tests carried out at ISMES, within an agreement with the Department of Fast Reactors of ENEA, on some models of the elements of PEC Fast Nuclear Reactor Core in the frame of the activities for the seismic verification of the PEC core. The seismic verification is briefly described with particular attention to the problems arising from the shocks among the various elements during an earthquake, as well as the computer code used, the purpose and the techniques used to perform tests, some results and the first comparison between the theory and the experimental data
Active vibration control using state space LQG and internal model control methods
DEFF Research Database (Denmark)
Mørkholt, Jakob; Elliott, S.J.
Two ways of designing discrete time robust H2-controllers for feedback broadband active vibration control are compared through computer simulations. The methods are based on different models of disturbance and plant transfer functions, but yield controllers with identical properties. Two simple...... ways of introducing robustness into the H2-design are compared, and finally an efficient way of designing a practical IIR-controller is proposed....
A microscopic derivation of nuclear collective rotation-vibration model, axially symmetric case
Gulshani, Parviz
2015-01-01
We derive a microscopic version of the successful phenomenological hydrodynamic model of Bohr-Davydov-Faessler-Greiner for collective rotation-vibration motion of an axially symmetric deformed nucleus. The derivation is not limited to small oscillation amplitude. The nuclear Schrodinger equation is canonically transformed the to collective co-ordinates, which is then linearized using a constrained variational method. The associated constraints are imposed on the wavefunction rather than on th...
Linear stability analysis of self-excited vibrations in drilling using an infinite dimensional model
Aarsnes, Ulf Jakob F.; Aamo, Ole Morten
2016-01-01
This paper deals with predicting the occurrence of self-excited vibrations during drilling. Previous work postulates that these are due to the coupling between the distributed drill string system and the regenerative effect in the bit-rock interaction law. We use a previously developed distributed model and the linearized bit-rock interaction law to derive a graphical condition for stability based on the Nyquist stability criterion.
Skewing of the glottal area during vocal fold vibration. A computer modelling study
Czech Academy of Sciences Publication Activity Database
Laukkanen, A. M.; Horáček, Jaromír; Švec, J. G.
University of Tokyo : Tokyo, 2006 - (Niimi, S.), s. 30-33 [International Conference on Voice Physiology and Biomechanics /5./. Tokyo (JP), 12.07.2006-14.07.2006] R&D Projects: GA AV ČR(CZ) IAA2076401 Institutional research plan: CEZ:AV0Z20760514 Keywords : biomechanics of voice * numerical simulation of vocal fold vibration * aeoroelastics model of the vocal folds Subject RIV: BI - Acoustics
Czech Academy of Sciences Publication Activity Database
Klika, Václav; Maršík, František
Lublin : Agatka, 2009, s. 148-151. ISBN 978-83-60783-18-4. [Sympozjum Naukowe.Sympozjum w ramach 40-lecia Katedry Ortopedii Dzieciecej UM i 60-lecia Uniwersytetu Medycznego w Lublinie. Lublin (PL), 17.09.2009-19.09.2009] R&D Projects: GA ČR(CZ) GA106/08/0557 Institutional research plan: CEZ:AV0Z20760514 Keywords : bone remodeling * vibrating plates * thermodynamic model Subject RIV: FI - Traumatology, Orthopedics
Soil-Pile Interaction in the Pile Vertical Vibration Based on Fictitious Soil-Pile Model
Guodong Deng; Jiasheng Zhang; Wenbing Wu; Xiong Shi; Fei Meng
2014-01-01
By introducing the fictitious soil-pile model, the soil-pile interaction in the pile vertical vibration is investigated. Firstly, assuming the surrounding soil of pile to be viscoelastic material and considering its vertical wave effect, the governing equations of soil-pile system subjected to arbitrary harmonic dynamic force are founded based on the Euler-Bernoulli rod theory. Secondly, the analytical solution of velocity response in frequency domain and its corresponding semianalytical solu...
Modelling and Quasilinear Control of Compressor Surge and Rotating Stall Vibrations
Ranjan Vepa
2010-01-01
An unsteady nonlinear and extended version of the Moore-Greitzer model is developed to facilitate the synthesis of a quasilinear stall vibration controller. The controller is synthesised in two steps. The first step defines the equilibrium point and ensures that the desired equilibrium point is stable. In the second step, the margin of stability at the equilibrium point is tuned or increased by an appropriate feedback of change in the mass flow rate about the steady mass flow rate at the comp...
Wind-Tunnel Tests of a Bridge Model with Active Vibration Control
DEFF Research Database (Denmark)
Hansen, H. I.; Thoft-Christensen, Palle; Mendes, P. A.;
The application of active control systems to reduce wind vibrations in bridges is a new area of research. This paper presents the results that were obtained on a set of wind tunnel tests of a bridge model equipped with active movable flaps. Based on the monitored position and motion of the deck......, the flaps are regulated by a control algorithm so that the wind forces exerted on them counteract the deck oscillations....
Rotational-vibrational coupling in the BPS Skyrme model of baryons
Adam, C; Sanchez-Guillen, J; Wereszczynski, A
2013-01-01
We calculate the rotational-vibrational spectrum in the BPS Skyrme model for the hedgehog skyrmion with baryon number one. The resulting excitation energies for the nucleon and delta Roper resonances are slightly above their experimental values. Together with the fact that in the standard Skyrme model these excitation energies are significantly lower than the experimental ones, this provides strong evidence for the conjecture that the inclusion of the BPS Skyrme model is necessary for a successful quantitative description of physical properties of baryons and nuclei.
Rotational-vibrational coupling in the BPS Skyrme model of baryons
Energy Technology Data Exchange (ETDEWEB)
Adam, C.; Naya, C.; Sanchez-Guillen, J. [Departamento de Física de Partículas, Universidad de Santiago de Compostela and Instituto Galego de Física de Altas Enerxias (IGFAE), E-15782 Santiago de Compostela (Spain); Wereszczynski, A. [Institute of Physics, Jagiellonian University, Reymonta 4, Kraków (Poland)
2013-11-04
We calculate the rotational-vibrational spectrum in the BPS Skyrme model for the hedgehog skyrmion with baryon number one. The resulting excitation energies for the nucleon and delta Roper resonances are slightly above their experimental values. Together with the fact that in the standard Skyrme model these excitation energies are significantly lower than the experimental ones, this provides strong evidence for the conjecture that the inclusion of the BPS Skyrme model is required for a successful quantitative description of physical properties of baryons and nuclei.
Free vibrations analysis of carbon nanotubes resting on Winkler foundations based on nonlocal models
Rahmanian, M.; Torkaman-Asadi, M. A.; Firouz-Abadi, R. D.; Kouchakzadeh, M. A.
2016-03-01
In the present study, free vibrations of single walled carbon nanotubes (SWCNT) on an elastic foundation is investigated by nonlocal theory of elasticity with both beam and shell models. The nonlocal boundary conditions are derived explicitly and effectiveness of nonlocal parameter appearing in nonlocal boundary conditions is studied. Also it is demonstrated that the beam model is comparatively incapable of capturing size effects while shell model captures size effects more precisely. Moreover, the effects of some parameters such as mechanical properties, foundation stiffness, length and radius ratios on the natural frequencies are studied and some conclusions are drawn.
Uncertainty modeling in vibration, control and fuzzy analysis of structural systems
Halder, Achintya; Ayyub, Bilal M
1997-01-01
This book gives an overview of the current state of uncertainty modeling in vibration, control, and fuzzy analysis of structural and mechanical systems. It is a coherent compendium written by leading experts and offers the reader a sampling of exciting research areas in several fast-growing branches in this field. Uncertainty modeling and analysis are becoming an integral part of system definition and modeling in many fields. The book consists of ten chapters that report the work of researchers, scientists and engineers on theoretical developments and diversified applications in engineering sy
Anharmonicity of the excited octupole band in actinides using supersymmetric quantum mechanics
Jolos, R. V.; von Brentano, P.; Casten, R. F.
2013-09-01
Background: Low-lying octupole collective excitations play an important role in the description of the structure of nuclei in the actinide region. Ground state alternating parity rotational bands combining both positive and negative parity states are known in several nuclei. However, only recently it has been discovered in 240Pu an excited positive parity rotational band having an octupole nature and demonstrating strong anharmonicity of the octupole motion in the band head energies.Purpose: To suggest a model describing both ground state and excited alternating parity bands, which includes a description of the anharmonic effects in the bandhead excitation energies and can be used to predict the energies of the excited rotational bands of octupole nature and the E1 transition probabilities.Methods: The mathematical technique of the supersymmetric quantum mechanics with a collective Hamiltonian depending only on the octupole collective variable which keeps axial symmetry is used to describe the ground state and excited alternating parity rotational bands.Results: The excitation energies of the states belonging to the lowest negative parity and the excited positive parity bands are calculated for 232Th, 238U, and 240Pu. The E1 transition matrix elements are also calculated for 240Pu.Conclusions: It is shown that the suggested model describes the excitation energies of the states of the lowest negative parity band with the accuracy around 10 keV. The anharmonicity in the bandhead energy of the excited positive parity band is described also. The bandhead energy of the excited positive parity band is described with the accuracy around 100 keV.
Directory of Open Access Journals (Sweden)
H. F. Wang
2014-01-01
Full Text Available Support looseness fault is a type of common fault in aeroengine. Serious looseness fault would emerge under larger unbalanced force, which would cause excessive vibration and even lead to rubbing fault, so it is important to analyze and recognize looseness fault effectively. In this paper, based on certain type turbofan engine structural features, a rotor-support-casing whole model for certain type turbofan aeroengine is established. The rotor and casing systems are modeled by means of the finite element beam method; the support systems are modeled by lumped-mass model; the support looseness fault model is also introduced. The coupled system response is obtained by numerical integral method. In this paper, based on the casing acceleration signals, the impact characteristics of symmetrical stiffness and asymmetric stiffness models are analyzed, finding that the looseness fault would lead to the longitudinal asymmetrical characteristics of acceleration time domain wave and the multiple frequency characteristics, which is consistent with the real trial running vibration signals. Asymmetric stiffness looseness model is verified to be fit for aeroengine looseness fault model.
Analysis of bit-rock interaction during stick-slip vibrations using PDC cutting force model
Energy Technology Data Exchange (ETDEWEB)
Patil, P.A.; Teodoriu, C. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE
2013-08-01
Drillstring vibration is one of the limiting factors maximizing the drilling performance and also causes premature failure of drillstring components. Polycrystalline diamond compact (PDC) bit enhances the overall drilling performance giving the best rate of penetrations with less cost per foot but the PDC bits are more susceptible to the stick slip phenomena which results in high fluctuations of bit rotational speed. Based on the torsional drillstring model developed using Matlab/Simulink for analyzing the parametric influence on stick-slip vibrations due to drilling parameters and drillstring properties, the study of relations between weight on bit, torque on bit, bit speed, rate of penetration and friction coefficient have been analyzed. While drilling with the PDC bits, the bit-rock interaction has been characterized by cutting forces and the frictional forces. The torque on bit and the weight on bit have both the cutting component and the frictional component when resolved in horizontal and vertical direction. The paper considers that the bit is undergoing stick-slip vibrations while analyzing the bit-rock interaction of the PDC bit. The Matlab/Simulink bit-rock interaction model has been developed which gives the average cutting torque, T{sub c}, and friction torque, T{sub f}, values on cutters as well as corresponding average weight transferred by the cutting face, W{sub c}, and the wear flat face, W{sub f}, of the cutters value due to friction.
Modeling and dynamic properties of dual-chamber solid and liquid mixture vibration isolator
Li, F. S.; Chen, Q.; Zhou, J. H.
2016-07-01
The dual-chamber solid and liquid mixture (SALiM) vibration isolator, mainly proposed for vibration isolation of heavy machines with low frequency, consists of four principle parts: SALiM working media including elastic elements and incompressible oil, multi-layers bellows container, rigid reservoir and the oil tube connecting the two vessels. The isolation system under study is governed by a two-degrees-of-freedom (2-DOF) nonlinear equation including quadratic damping. Simplifying the nonlinear damping into viscous damping, the equivalent stiffness and damping model is derived from the equation for the response amplitude. Theoretical analysis and numerical simulation reveal that the isolator's stiffness and damping have multiple properties with different parameters, among which the effects of exciting frequency, vibrating amplitude, quadratic damping coefficient and equivalent stiffness of the two chambers on the isolator's dynamics are discussed in depth. Based on the boundary characteristics of stiffness and damping and the main causes for stiffness hardening effect, improvement strategies are proposed to obtain better dynamic properties. At last, experiments were implemented and the test results were generally consistent with the theoretical ones, which verified the reliability of the nonlinear dynamic model.
Suppression of chaotic vibrations in a nonlinear half-car model
International Nuclear Information System (INIS)
The present work investigates the nonlinear response of a half-car model. The disturbances of the road are assumed to be sinusoidal. After constructing the bifurcation diagram, we using the 0-1 test for identify the chaotic motion. The principal objective of this study is to eliminate the chaotic behaviour of the chassis and reduce its vibration, and for this reason a control system for semi-active vehicle suspension with magnetorheological damper is proposed. The control mechanism is designed based on SDRE technique, where the control parameter is the voltage applied to the coil of the damper. Numerical results show that the proposed control method is effective in significantly reducing of the chassis vibration, increasing therefore, passenger comfort
Suppression of chaotic vibrations in a nonlinear half-car model
Energy Technology Data Exchange (ETDEWEB)
Tusset, Ângelo Marcelo, E-mail: tusset@utfpr.edu.br, E-mail: piccirillo@utfpr.edu.br, E-mail: fcjanzen@utfpr.edu.br, E-mail: wagner-barth@hotmail.com; Piccirillo, Vinícius, E-mail: tusset@utfpr.edu.br, E-mail: piccirillo@utfpr.edu.br, E-mail: fcjanzen@utfpr.edu.br, E-mail: wagner-barth@hotmail.com; Janzen, Frederic Conrad, E-mail: tusset@utfpr.edu.br, E-mail: piccirillo@utfpr.edu.br, E-mail: fcjanzen@utfpr.edu.br, E-mail: wagner-barth@hotmail.com; Lenz, Wagner Barth, E-mail: tusset@utfpr.edu.br, E-mail: piccirillo@utfpr.edu.br, E-mail: fcjanzen@utfpr.edu.br, E-mail: wagner-barth@hotmail.com [UTFPR- PONTA GROSSA, PR (Brazil); Balthazar, José Manoel, E-mail: jmbaltha@rc.unesp.br [UNESP-BAURU, SP (Brazil); Fonseca Brasil, Reyolando M. L. R. da, E-mail: reyolando.brasil@ufabc.edu.br [UFABC-SANTO ANDRE, SP (Brazil)
2014-12-10
The present work investigates the nonlinear response of a half-car model. The disturbances of the road are assumed to be sinusoidal. After constructing the bifurcation diagram, we using the 0-1 test for identify the chaotic motion. The principal objective of this study is to eliminate the chaotic behaviour of the chassis and reduce its vibration, and for this reason a control system for semi-active vehicle suspension with magnetorheological damper is proposed. The control mechanism is designed based on SDRE technique, where the control parameter is the voltage applied to the coil of the damper. Numerical results show that the proposed control method is effective in significantly reducing of the chassis vibration, increasing therefore, passenger comfort.
Gulshani, P.
2016-07-01
We derive a microscopic version of the successful phenomenological hydrodynamic model of Bohr-Davydov-Faessler-Greiner for collective rotation-vibration motion of an axially symmetric deformed nucleus. The derivation is not limited to small oscillation amplitude. The nuclear Schrodinger equation is canonically transformed to collective co-ordinates, which is then linearized using a constrained variational method. The associated constraints are imposed on the wavefunction rather than on the particle co-ordinates. The approach yields three self-consistent, time-reversal invariant, cranking-type Schrodinger equations for the rotation-vibration and intrinsic motions, and a self-consistency equation. For harmonic oscillator mean-field potentials, these equations are solved in closed forms for excitation energy, cut-off angular momentum, and other nuclear properties for the ground-state rotational band in some deformed nuclei. The results are compared with measured data.
Erdbrink, C.D.; Krzhizhanovskaya, V.V.; Sloot, P. M. A.
2012-01-01
Operation of flood barrier gates is sometimes hampered by flow-induced vibrations. Although the physics is understood for specific gate types, it remains challenging to judge dynamic gate behaviour for unanticipated conditions. This paper presents a hybrid modelling system for predicting vibrations by combining machine learning with physics-based modelling so that critical situations can be avoided. In the outlined data-driven approach gate response data is acquired by sensors and stored in a...
Xu, F; J. Hu; Li, Y.; Zou, J.; Xu, Y; Shang, J.
2013-01-01
Orbital Friction Vibration Actuator (OFVA) is a core component of Orbital Friction Welding (OFW), which is a novel apertureless welding technology utilizing friction heat to implement solid-state joining. In this paper, topology and operational principle of OFVA are introduced, the analytical formulas of the electromagnetic force for the x and y directions, which can drive the mover to generate a circular motion trajectory, are derived, and the characteristic of static electromagnetic fo...
Low dimensional models for stick-slip vibration of drill-strings
Energy Technology Data Exchange (ETDEWEB)
Silveira, M; Wiercigroch, M, E-mail: m.silveira@abdn.ac.u, E-mail: m.wiercigroch@abdn.ac.u [Centre for Applied Dynamics Research, School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE (United Kingdom)
2009-08-01
Effective reduction of drill-string vibration is still a major problem in drilling industry and therefore robust predictive tools need to be developed. In this paper we study two low dimensional nonlinear models. The first is a 1-DOF torsional model of the botom-hole assembly (BHA). The second model is a 3-DOF torsional system having in addition to the BHA a rotary table, which allows simulation of interactions for which there is experimental evidence. Three different friction models with increasing levels of complexity are applied to determine their influence in the dynamical responses. Comparison between the dynamic responses for three friction models shows that the dangerous stick-slip limit-cycles do not change qualitatively. Simulations show that, if appropriately controlled, large amplitude stick-slip limit-cycles can change to small amplitude limit-cycles in Model 2. In Model 1, with constant velocity of the rotary table, it goes from a large amplitude stick-slip limit-cycle to a fixed point. Bifurcation diagrams confirm the existence of a set of parameters in which the system operates without stick-slip vibration.
Low dimensional models for stick-slip vibration of drill-strings
International Nuclear Information System (INIS)
Effective reduction of drill-string vibration is still a major problem in drilling industry and therefore robust predictive tools need to be developed. In this paper we study two low dimensional nonlinear models. The first is a 1-DOF torsional model of the botom-hole assembly (BHA). The second model is a 3-DOF torsional system having in addition to the BHA a rotary table, which allows simulation of interactions for which there is experimental evidence. Three different friction models with increasing levels of complexity are applied to determine their influence in the dynamical responses. Comparison between the dynamic responses for three friction models shows that the dangerous stick-slip limit-cycles do not change qualitatively. Simulations show that, if appropriately controlled, large amplitude stick-slip limit-cycles can change to small amplitude limit-cycles in Model 2. In Model 1, with constant velocity of the rotary table, it goes from a large amplitude stick-slip limit-cycle to a fixed point. Bifurcation diagrams confirm the existence of a set of parameters in which the system operates without stick-slip vibration.
Institute of Scientific and Technical Information of China (English)
R ANSARI; S ROUHI; M ARYAYI
2013-01-01
By the atomistic and continuum finite element models, the free vibration behavior of single-walled carbon nanotubes (SWCNTs) is studied. In the atomistic finite element model, the bonds and atoms are modeled by the beam and point mass elements, respectively. The molecular mechanics is linked to structural mechanics to determine the elastic properties of the mentioned beam elements. In the continuum finite element approach, by neglecting the discrete nature of the atomic structure of the nanotubes, they are modeled with shell elements. By both models, the natural frequencies of SWCNTs are computed, and the effects of the geometrical parameters, the atomic structure, and the boundary conditions are investigated. The accuracy of the utilized methods is verified in comparison with molecular dynamic simulations. The molecular structural model leads to more reliable results, especially for lower aspect ratios. The present analysis provides valuable information about application of continuum models in the investigation of the mechanical behaviors of nanotubes.
Theoretical studies of fluid-structure interactions in two-phase flow through vibration models
International Nuclear Information System (INIS)
On the basis of reduced characteristic equations for calculation of continuity, momentum and energy of a two-phase flow, relations are derived for a substitute of the gas-fluid mixture, covering position and time-dependent density and velocity data, and are verified by a boiling fluid model. The results are applied to a 1D and a 2D vibration model (pendulum in two-phase flow), taking into account the flui-structure interaction and the calculation of eigenfrequencies and damping. (orig.)
Kouroussis, G.; Bergeret, E.; Conti, C.; Verlinden, O.
With the development of continuous technological innovation, the railway transport is presented as an interesting alternative to the road traffic. Some drawbacks exist, one of the most problematic being certainly the vibrations induced by the railway traffic. The presented research wants to establish a reliable methodology in order to evaluate, from the design stage of a vehicle or of a track, the efforts transmitted by the vehicle to the track/soil system and consequently the level of vibrations in the surroundings. An analysis of the interaction between the track and the soil has been performed in order to show when the track/soil uncoupling can be assumed, with the aim of working in two stages. The first step is based on the vertical dynamic behaviour of the vehicle/track subsystem, taking into account any irregularity in the rail surface. For the soil subsystem (second step), recent publications showed that the finite/infinite element method can be an interesting alternative to boundary element method. The objective of this paper is to demonstrate the real benefit of the vehicle modelling in this kind of problem. Typical railway applications (Brussels tram, Thalys HST) are proposed, showing among others that significant reduction of ground vibration level can be obtained by modifying the dynamic characteristics of the vehicle.
Two-dimensional model of vocal fold vibration for sound synthesis of voice and soprano singing
Adachi, Seiji; Yu, Jason
2005-05-01
Voiced sounds were simulated with a computer model of the vocal fold composed of a single mass vibrating both parallel and perpendicular to the airflow. Similarities with the two-mass model are found in the amplitudes of the glottal area and the glottal volume flow velocity, the variation in the volume flow waveform with the vocal tract shape, and the dependence of the oscillation amplitude upon the average opening area of the glottis, among other similar features. A few dissimilarities are also found in the more symmetric glottal and volume flow waveforms in the rising and falling phases. The major improvement of the present model over the two-mass model is that it yields a smooth transition between oscillations with an inductive load and a capacitive load of the vocal tract with no sudden jumps in the vibration frequency. Self-excitation is possible both below and above the first formant frequency of the vocal tract. By taking advantage of the wider continuous frequency range, the two-dimensional model can successfully be applied to the sound synthesis of a high-pitched soprano singing, where the fundamental frequency sometimes exceeds the first formant frequency. .
A mathematical model for estimating the vibration due to basting in Sarcheshmeh Copper Mine
International Nuclear Information System (INIS)
Ground vibration due to blasting is the research subject of many investigations. A lot of works have been done in order to estimate the quality and quantity of this blasting outcome. Mathematical models proposed by various investigators are a noticeable result of these investigations. In this paper, the origin of these mathematical models are studied and the short comes are pointed out. With aid of real data a new empirical model has been proposed. This model is some modification of the previous ones with some different parameters. This investigation is based on analyzing the data obtained by operating 14 blasts in Sarcheshmeh Copper Mine whose data have been collected by seismographs installed in the area. In the proposed model, instead of the amount of charge exploded in each delay the amount of charge the vibration due to which is designed to facilitate application of a radial confining pressure to a grouted bolt while pulling it axially. During the test, both axial displacement of the bolt as well as the radial dilation of the grout was monitored. Few deformed bolts were designed and manufactured to study the effect of the shape of the ribs. While pull out, the cement that is captured between lugs will shear which in turn emphasizes the importance of shear strength of the grout annulus. In this report, details of the laboratory test results are presented and conclusions are given based on the obtained results
Thermal weights for semiclassical vibrational response functions
Energy Technology Data Exchange (ETDEWEB)
Moberg, Daniel R.; Alemi, Mallory; Loring, Roger F., E-mail: roger.loring@cornell.edu [Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853 (United States)
2015-08-28
Semiclassical approximations to response functions can allow the calculation of linear and nonlinear spectroscopic observables from classical dynamics. Evaluating a canonical response function requires the related tasks of determining thermal weights for initial states and computing the dynamics of these states. A class of approximations for vibrational response functions employs classical trajectories at quantized values of action variables and represents the effects of the radiation-matter interaction by discontinuous transitions. Here, we evaluate choices for a thermal weight function which are consistent with this dynamical approximation. Weight functions associated with different semiclassical approximations are compared, and two forms are constructed which yield the correct linear response function for a harmonic potential at any temperature and are also correct for anharmonic potentials in the classical mechanical limit of high temperature. Approximations to the vibrational linear response function with quantized classical trajectories and proposed thermal weight functions are assessed for ensembles of one-dimensional anharmonic oscillators. This approach is shown to perform well for an anharmonic potential that is not locally harmonic over a temperature range encompassing the quantum limit of a two-level system and the limit of classical dynamics.
Anharmonic phonons and magnons in BiFeO3
International Nuclear Information System (INIS)
The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 < T < 750K, using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. We do not find any evidence for a spin gap. A strong T-dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large amplitude motions of Bi and O ions observed with neutron diffraction. These results highlight the importance of spin-phonon coupling in this material.
Anharmonic phonons and magnons in BiFeO3
Energy Technology Data Exchange (ETDEWEB)
Delaire, Olivier A [ORNL; Ma, Jie [ORNL; Stone, Matthew B [ORNL; Huq, Ashfia [ORNL; Gout, Delphine J [ORNL; Brown, Craig [National Institute of Standards and Technology (NIST); Wang, Kefeng [Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing; Ren, Zhifeng [Boston College, Chestnut Hill
2012-01-01
The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO3 were measured for temperatures 200 < T < 750K , using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO3 closely resembles that of similar Fe perovskites, such as LaFeO3, despite the cycloid modulation in BiFeO3. We do not find any evidence for a spin gap. A strong T-dependence of the phonon DOS was found, with a marked broadening of the whole spectrum, providing evidence of strong anharmonicity. This anharmonicity is corroborated by large amplitude motions of Bi and O ions observed with neutron diffraction. These results highlight the importance of spin-phonon coupling in this material.
Dirac bound states of anharmonic oscillator in external fields
Energy Technology Data Exchange (ETDEWEB)
Hamzavi, Majid, E-mail: majid.hamzavi@gmail.com [Department of Physics, University of Zanjan, Zanjan (Iran, Islamic Republic of); Ikhdair, Sameer M., E-mail: sikhdair@gmail.com [Department of Physics, Faculty of Science, an-Najah National University, Nablus, West Bank, Palestine (Country Unknown); Department of Electrical and Electronic Engineering, Near East University, 922022 Nicosia, Northern Cyprus, Mersin 10 (Turkey); Falaye, Babatunde J., E-mail: fbjames11@physicist.net [Theoretical Physics Section, Department of Physics, University of Ilorin, P. M. B. 1515, Ilorin (Nigeria)
2014-02-15
We explore the effect of the external magnetic and Aharonov–Bohm (AB) flux fields on the energy levels of Dirac particle subjects to mixed scalar and vector anharmonic oscillator field in the two-dimensional (2D) space. We calculate the exact energy eigenvalues and the corresponding un-normalized two-spinor-components wave functions in terms of the chemical potential parameter, magnetic field strength, AB flux field and magnetic quantum number by using the Nikiforov–Uvarov (NU) method. -- Highlights: • Effect of the external fields on the energy levels of Dirac particle with the anharmonic oscillator is investigated. • The solutions are discussed in view of spin and pseudospin symmetries limits. • The energy levels and wave function are presented by the Nikiforov–Uvarov method.
Superfluid Fermi Gases in a Rotating Anharmonic Trap
Institute of Scientific and Technical Information of China (English)
MA Juan; XUE Ju-Kui
2011-01-01
The quadrupole mode frequency, the monopole mode frequency, and the critical rotational frequency for stirring a single vortex nucleation along the BEC-BCS crossover are obtained. The results show that, in a rotating anisotropic anharmonic trap, the quadrupole mode frequency and the critical rotational frequency for stirring a single vortex nucleation are modified significantly when the system crosses from the BEC side to the BCS side: the anisotropy of the trap induces a downshift of the quadrupole mode frequency and the critical rotational frequency and helps the vortex formation in the system, while an anharmonic trap induces an upshift of the quadrupole mode frequency and the critical rotational frequency and suppresses the vortex formation in the system.
Finite-element time evolution operator for the anharmonic oscillator
Milton, Kimball A.
1995-01-01
The finite-element approach to lattice field theory is both highly accurate (relative errors approximately 1/N(exp 2), where N is the number of lattice points) and exactly unitary (in the sense that canonical commutation relations are exactly preserved at the lattice sites). In this talk I construct matrix elements for dynamical variables and for the time evolution operator for the anharmonic oscillator, for which the continuum Hamiltonian is H = p(exp 2)/2 + lambda q(exp 4)/4. Construction of such matrix elements does not require solving the implicit equations of motion. Low order approximations turn out to be extremely accurate. For example, the matrix element of the time evolution operator in the harmonic oscillator ground state gives a results for the anharmonic oscillator ground state energy accurate to better than 1 percent, while a two-state approximation reduces the error to less than 0.1 percent.
Masoumi, H. R.; Degrande, G.
2008-06-01
This paper presents a numerical model for the prediction of free field vibrations due to vibratory and impact pile driving. As the focus is on the response in the far field, where deformations are relatively small, a linear elastic constitutive behavior is assumed for the soil. The free field vibrations are calculated by means of a coupled FE-BE model using a subdomain formulation. The results show that, in the near field, the response of the soil is dominated by a vertically polarized shear wave, whereas in the far field, Rayleigh waves dominate the ground vibration and body waves are importantly attenuated. Finally, the computed ground vibrations are compared with the results of field measurements reported in the literature.
International Nuclear Information System (INIS)
Molecular-surface studies are often done by assuming a corrugated, static (i.e., rigid) surface. To be able to investigate the effects that vibrations of surface atoms may have on spectra and cross sections, an expansion Hamiltonian model is proposed on the basis of the recently reported [R. Marquardt et al., J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES), which was built for the CO/Cu(100) system with a rigid surface. In contrast to other molecule-surface coupling models, such as the modified surface oscillator model, the coupling between the adsorbed molecule and the surface atoms is already included in the present expansion SAP-PES model, in which a Taylor expansion around the equilibrium positions of the surface atoms is performed. To test the quality of the Taylor expansion, a direct model, that is avoiding the expansion, is also studied. The latter, however, requests that there is only one movable surface atom included. On the basis of the present expansion and direct models, the effects of a moving top copper atom (the one to which CO is bound) on the energy levels of a bound CO/Cu(100) system are studied. For this purpose, the multiconfiguration time-dependent Hartree calculations are carried out to obtain the vibrational fundamentals and overtones of the CO/Cu(100) system including a movable top copper atom. In order to interpret the results, a simple model consisting of two coupled harmonic oscillators is introduced. From these calculations, the vibrational levels of the CO/Cu(100) system as function of the frequency of the top copper atom are discussed
Computer Simulation Study of Thermal Conduction in 1D Chains of Anharmonic Oscillators
Institute of Scientific and Technical Information of China (English)
Tejal N.Shah; P.N.Gajjar
2013-01-01
In this work thermal conduction in one-dimensional (1D) chains of anharmonic oscillators are studied using computer simulation.The temperature profile,heat flux and thermal conductivity are investigated for chain length N =100,200,400,800 and 1600.In the computer simulation anharmonicity is introduced due to Fermi-Pasta-Ulam-β (FPU-β) model For substrate interaction,an onsite potential due to Frenkel-Kontorova (FK) model has been used.Numerical simulations demonstrate that temperature gradient scales behave as N-1 linearly with the relation J =0.1765/N.For the thermal conductivity K,KN to N obey the linear relation of the type KN =0.8805N.It is shown that thermal transport is dependent on phonon-phonon interaction as well as phonon-lattice interaction.The thermal conductivity increaseslinearly with increase inanharmonicity and predicts relation κ =0.133 + 0.804β.It is also concluded that for higher value of the strength of the onsite potential system tends to a thermal insulator.
Path Integral Solution for an Angle-Dependent Anharmonic Oscillator
Institute of Scientific and Technical Information of China (English)
S.Haouat
2012-01-01
We have given a straightforward method to solve the problem of noncentral anharmonic oscillator in three dimensions. The relative propagator is presented by means of path integrals in spherical coordinates. By making an adequate change of time we are able to separate the angular motion from the radial one. The relative propagator is then exactly calculated. The energy spectrum and the corresponding wave functions are obtained.
A resurgence analysis for cubic and quartic anharmonic potentials
Gahramanov, Ilmar
2016-01-01
In this work we explicitly show resurgence relations between perturbative and one instanton sectors of the resonance energy levels for cubic and quartic anharmonic potentials in one-dimensional quantum mechanics. Both systems satisfy the Dunne-Unsal relation and hence we are able to derive one-instanton non-perturbative contributions with the fluctuation terms to the energy merely from the perturbative data. We confirm our results with previous results obtained by Zinn-Justin et al.
Vibrational properties of the π-bonded chain model of the Si(111) 2 x 1 surface
International Nuclear Information System (INIS)
A tight-binding theory is used to study vibrational excitations of the π-bonded chain model of the Si(111)2x1 surface. Some aspects of the surface phonon spectrum are discussed. The authors study the charge fluctuations driven by the vibrational excitations and the surface conductivity associated with the phonons. They find that a longitudinal optical phonon on the surface chains dominates the surface conductivity
Phonon anharmonicity and negative thermal expansion in SnSe
Bansal, Dipanshu; Hong, Jiawang; Li, Chen W.; May, Andrew F.; Porter, Wallace; Hu, Michael Y.; Abernathy, Douglas L.; Delaire, Olivier
2016-08-01
The anharmonic phonon properties of SnSe in the P n m a phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measured the phonon dispersions and density of states (DOS) and their temperature dependence, which revealed a strong, inhomogeneous shift and broadening of the spectrum on warming. First-principles simulations were performed to rationalize these measurements, and to explain the previously reported anisotropic thermal expansion, in particular the negative thermal expansion within the Sn-Se bilayers. Including the anisotropic strain dependence of the phonon free energy, in addition to the electronic ground state energy, is essential to reproduce the negative thermal expansion. From the phonon DOS obtained with INS and additional calorimetry measurements, we quantify the harmonic, dilational, and anharmonic components of the phonon entropy, heat capacity, and free energy. The origin of the anharmonic phonon thermodynamics is linked to the electronic structure.
Modelling the effects of solar particle events on vibrationally excited hydroxyl
Winkler, Holger; Maik Wissing, Jan; Teiser, Georg; von Savigny, Christian; Notholt, Justus
2016-04-01
The main source of vibrationally excited hydroxyl molecules in the Earth's mesosphere is the reaction H + O3 → OH(v) + O2. The exothermicity of this process leads to excitations of hydroxyl up to the 9th vibrational state. During solar particle events (SPEs), energetic protons and electrons can enter the polar atmosphere and cause ion-chemical perturbations. It is well established that both ozone and hydrogen are affected by SPEs. As a result, the production rate of OH(v) changes. Additionally, the quenching rates of OH(v) change due to increasing concentrations of atomic oxygen. Furthermore, SPE induced temperature changes influence the chemistry of OH(v). We use a one-dimensional atmospheric chemistry model in combination with the University of Bremen Ion Chemistry (UBIC) model to simulate the impact of major SPEs on mesospheric OH(v = 0…9). For this purpose, SPE ionisation rates from AIMOS (Atmospheric Ionization Module Osnabrück) are used. Temperature changes are considered by predictions of the MSIS-E-90 atmosphere model as well as by data from the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite instrument. The modelled radiative emissions of OH(v) are compared to satellite observations (SABER and SCIAMACHY = Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY).
Venuti, Fiammetta; Racic, Vitomir; Corbetta, Alessandro
2016-09-01
After 15 years of active research on the interaction between moving people and civil engineering structures, there is still a lack of reliable models and adequate design guidelines pertinent to vibration serviceability of footbridges due to multiple pedestrians. There are three key issues that a new generation of models should urgently address: pedestrian "intelligent" interaction with the surrounding people and environment, effect of human bodies on dynamic properties of unoccupied structure and inter-subject and intra-subject variability of pedestrian walking loads. This paper presents a modelling framework of human-structure interaction in the vertical direction which addresses all three issues. The framework comprises two main models: (1) a microscopic model of multiple pedestrian traffic that simulates time varying position and velocity of each individual pedestrian on the footbridge deck, and (2) a coupled dynamic model of a footbridge and multiple walking pedestrians. The footbridge is modelled as a SDOF system having the dynamic properties of the unoccupied structure. Each walking pedestrian in a group or crowd is modelled as a SDOF system with an adjacent stochastic vertical force that moves along the footbridge following the trajectory and the gait pattern simulated by the microscopic model of pedestrian traffic. Performance of the suggested modelling framework is illustrated by a series of simulated vibration responses of a virtual footbridge due to light, medium and dense pedestrian traffic. Moreover, the Weibull distribution is shown to fit well the probability density function of the local peaks in the acceleration response. Considering the inherent randomness of the crowd, this makes it possible to determine the probability of exceeding any given acceleration value of the occupied bridge.
Decision tree based knowledge acquisition and failure diagnosis using a PWR loop vibration model
International Nuclear Information System (INIS)
An analytical vibration model of the primary system of a 1300 MW PWR was used for simulating mechanical faults. Deviations in the calculated power density spectra and coherence functions are determined and classified. The decision tree technique is then used for a personal computer supported knowledge presentation and for optimizing the logical relationships between the simulated faults and the observed symptoms. The optimized decision tree forms the knowledge base and can be used to diagnose known cases as well as to include new data into the knowledge base if new faults occur. (author)
Vibrational behavior of adaptive aircraft wing structures modelled as composite thin-walled beams
Song, O.; Librescu, L.; Rogers, C. A.
1992-01-01
The vibrational behavior of cantilevered aircraft wings modeled as thin-walled beams and incorporating piezoelectric effects is studied. Based on the converse piezoelectric effect, the system of piezoelectric actuators conveniently located on the wing yield the control of its associated vertical and lateral bending eigenfrequencies. The possibility revealed by this study enabling one to increase adaptively the eigenfrequencies of thin-walled cantilevered beams could play a significant role in the control of the dynamic response and flutter of wing and rotor blade structures.
Role of energy exchange in vibrational dephasing processes in liquids and solids
International Nuclear Information System (INIS)
Three theories which claim relevance to the dephasing of molecular vibrations in condensed phase matter are presented. All of these theories predict (in certain limiting cases) that the widths and shifts of molecular vibrations will obey an Arrhenius temperature dependence. The basic tenets of the theories are detailed so that the differences between them may be used in an experiment to distinguish between them. One model, based on intermolecular energy exchange of low-frequency modes, results in dephasing the high-frequency modes when anharmonic coupling is present. A computer analysis of temperature dependent experimental lineshapes can result in the extraction of various parameters such as the anharmonic shifts and the exchange rates. It is shown that, in order to properly assess the relative validity of the three models, other evidence must be obtained such as the spectral parameters of the low-frequency modes, the combination bands, and the isotopic dilution behavior. This evidence is presented for d14-durene (perdeutero-1,2,4,5-tetramethylbenzene) and compared to previous data obtained on pure h14-durene. An extension of the (HSC) intermolecular energy exchange model which allows for the possibility of partial delocalization of the low-frequency modes gives an adequate description of the experimental evidence. Isotopic dilution experiments, in particular, have resulted in a detailed picture of the energy transfer dynamics of the low-frequency modes. A section in which some spontaneous Raman spectra support a model of inhomogeneous broadening in liquids based on results of picosecond stimulated Raman spectroscopy is presented. The model is that a distribution of environmental sites is created by a distribution in the local density and thus creates inhomogeneous broadening
Pisanova, Ekaterina S.; Krushkov, Angel Y.
2016-03-01
An exactly solvable lattice model describing structural phase transitions in an anharmonic crystal with long-range interaction (decreasing at large distances r as r-d-σ, where d is the space dimensionality and 0 power and (b) quantum disordered region - exponentially.
On the Free Vibration Modeling of Spindle Systems: A Calibrated Dynamic Stiffness Matrix
Directory of Open Access Journals (Sweden)
Omar Gaber
2014-01-01
Full Text Available The effect of bearings on the vibrational behavior of machine tool spindles is investigated. This is done through the development of a calibrated dynamic stiffness matrix (CDSM method, where the bearings flexibility is represented by massless linear spring elements with tuneable stiffness. A dedicated MATLAB code is written to develop and to assemble the element stiffness matrices for the system’s multiple components and to apply the boundary conditions. The developed method is applied to an illustrative example of spindle system. When the spindle bearings are modeled as simply supported boundary conditions, the DSM model results in a fundamental frequency much higher than the system’s nominal value. The simply supported boundary conditions are then replaced by linear spring elements, and the spring constants are adjusted such that the resulting calibrated CDSM model leads to the nominal fundamental frequency of the spindle system. The spindle frequency results are also validated against the experimental data. The proposed method can be effectively applied to predict the vibration characteristics of spindle systems supported by bearings.
The influence of external weak magnetic field on anharmonic nanocontacts of Josephson type
International Nuclear Information System (INIS)
The work considers the influence of weak external magnetic field on anharmonic Josephson's nanocontacts. The coordinate dependences of phase differences φ(x), superconducting current Is(x) and magnetic field H(x) anharmonic nanocontacts were found. It was defined the anharmonism parameter increase leads to phase difference φ(x) decaying faster, and penetration of magnetic field decreases. It was shown the considered contacts react on external weak magnetic field in more passive way
Non-Gaussian wave packet dynamics in anharmonic potential: Cumulant expansion treatment
Toutounji, Mohamad
2015-03-01
This manuscript utilizes cumulant expansion as an alternative algebraic approach to evaluating integrals and solving a system of nonlinear differential equations for probing anharmonic dynamics in condensed phase systems using Morse oscillator. These integrals and differential equations become harder to solve as the anharmonicity of the system goes beyond that of Morse oscillator description. This algebraic approach becomes critically important in case of Morse oscillator as it tends to exhibit divergent dynamics and numerical uncertainties at low temperatures. The autocorrelation function is calculated algebraically and compared to the exact one for they match perfectly. It is also compared to the approximate autocorrelation function using the differential equations technique reported in Toutounji (2014) for weak and strong electron-phonon coupling cases. It is found that the present cumulant method is more efficient, and easier to use, than the exact expression. Deviation between the approximate autocorrelation function and the exact autocorrelation function starts to arise as the electron-phonon coupling strength increases. The autocorrelation function obtained using cumulants identically matches the exact autocorrelation function, thereby surpassing the approach presented in Toutounji (2014). The advantage of the present methodology is its applicability to various types of electron-phonon coupling cases. Additionally, the herein approach only uses algebraic techniques, thereby avoiding both the divergence integral and solving a set of linear first- and second-order partial differential equations as was done in previous work. Model calculations are presented to demonstrate the accuracy of the herein work.
DEFF Research Database (Denmark)
Thomsen, Jon Juel
About this textbook An ideal text for students that ties together classical and modern topics of advanced vibration analysis in an interesting and lucid manner. It provides students with a background in elementary vibrations with the tools necessary for understanding and analyzing more complex...... dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... and physics. This edition includes a new chapter on the useful effects of fast vibrations and many new exercise problems. Written for: Students in mechanical or structural engineering. Keywords: Nonlinear Vibrations, Bifurcations, Chaotic Vibrations, Vibrations and Stability....
Directory of Open Access Journals (Sweden)
N. Al Sdran
2016-06-01
Full Text Available The numerical solutions of the time independent Schrödinger equation of different one-dimensional potentials forms are sometime achieved by the asymptotic iteration method. Its importance appears, for example, on its efficiency to describe vibrational system in quantum mechanics. In this paper, the Airy function approach and the Numerov method have been used and presented to study the oscillator anharmonic potential V(x = Ax2α + Bx2, (A>0, B<0, with (α = 2 for quadratic, (α =3 for sextic and (α =4 for octic anharmonic oscillators. The Airy function approach is based on the replacement of the real potential V(x by a piecewise-linear potential v(x, while, the Numerov method is based on the discretization of the wave function on the x-axis. The first energies levels have been calculated and the wave functions for the sextic system have been evaluated. These specific values are unlimited by the magnitude of A, B and α. It’s found that the obtained results are in good agreement with the previous results obtained by the asymptotic iteration method for α =3.
Thi, Wing-Fai; Woitke, Peter; Plas, Gerrit van des; Bertelsen, Rosina; Wiesenfeld, Laurent
2012-01-01
The carbon monoxide rovibrational emission from discs around Herbig Ae stars and T Tauri stars with strong ultraviolet emissions suggests that fluorescence pumping from the ground X1 Sigma+ to the electronic A1 Pi state of CO should be taken into account in disc models. We implemented a CO model molecule that includes up to 50 rotational levels within nine vibrational levels for the ground and A excited states in the radiative photochemical code ProDiMo. We took CO collisions with hydrogen molecules, hydrogen atoms, helium, and electrons into account. We estimated the missing collision rates using standard scaling laws and discussed their limitations. UV fluorescence and IR pumping impact on the population of ro-vibrational v > 1 levels. The v = 1 rotational levels are populated at rotational temperatures between the radiation temperature around 4.6 micron and the gas kinetic temperature. The UV pumping efficiency increases with decreasing disc mass. The consequence is that the vibrational temperatures, which...
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard; Kirkegaard, Poul Henning; Persson, K.;
2012-01-01
Transmission of sound and vibrations in the built environment is a nuisance to people working and living in buildings.......Transmission of sound and vibrations in the built environment is a nuisance to people working and living in buildings....
Parker, Robert G.; Guo, Yi; Eritenel, Tugan; Ericson, Tristan M.
2012-01-01
Vibration and noise caused by gear dynamics at the meshing teeth propagate through power transmission components to the surrounding environment. This study is devoted to developing computational tools to investigate the vibro-acoustic propagation of gear dynamics through a gearbox using different bearings. Detailed finite element/contact mechanics and boundary element models of the gear/bearing/housing system are established to compute the system vibration and noise propagation. Both vibration and acoustic models are validated by experiments including the vibration modal testing and sound field measurements. The effectiveness of each bearing type to disrupt vibration propagation is speed-dependent. Housing plays an important role in noise radiation .It, however, has limited effects on gear dynamics. Bearings are critical components in drivetrains. Accurate modeling of rolling element bearings is essential to assess vibration and noise of drivetrain systems. This study also seeks to fully describe the vibro-acoustic propagation of gear dynamics through a power-transmission system using rolling element and fluid film wave bearings. Fluid film wave bearings, which have higher damping than rolling element bearings, could offer an energy dissipation mechanism that reduces the gearbox noise. The effectiveness of each bearing type to disrupt vibration propagation in explored using multi-body computational models. These models include gears, shafts, rolling element and fluid film wave bearings, and the housing. Radiated noise is mapped from the gearbox surface to surrounding environment. The effectiveness of rolling element and fluid film wave bearings in breaking the vibro-acoustic propagation path from the gear to the housing is investigated.
Directory of Open Access Journals (Sweden)
Stefan E. Huber
2012-09-01
Full Text Available We calculate harmonic frequencies of the three most abundant carbonic acid conformers. For this, different model chemistries are investigated with respect to their benefits and shortcomings. Based on these results we use perturbation theory to calculate anharmonic corrections at the ωB97XD/aug-cc-pVXZ, X = D, T, Q, level of theory and compare them with recent experimental data and theoretical predictions. A discrete variable representation method is used to predict the large anharmonic contributions to the frequencies of the stretching vibrations in the hydrogen bonds in the carbonic acid dimer. Moreover, we re-investigate the energetics of the formation of the carbonic acid dimer from its constituents water and carbon dioxide using a high-level extrapolation method. We find that the ωB97XD functional performs well in estimating the fundamental frequencies of the carbonic acid conformers. Concerning the reaction energetics, the accuracy of ωB97XD is even comparable to the high-level extrapolation method. We discuss possibilities to detect carbonic acid in various natural environments such as Earth's and Martian atmospheres.
Institute of Scientific and Technical Information of China (English)
Zhang Da; Sun Jiu-Xun
2012-01-01
A simple equation of state (EOS) in wide ranges of pressure and temperature is constructed within the MieGrüneisen-Debye framework.Instead of the popular Birch-Murnaghan and Vinet EOS,we employ a five-parameter cold energy expression to represent the static EOS term,which can correctly produce cohesive energy without any spurious oscillations in the extreme compression and expansion regions.We developed a Padé approximation-based analytic Debye quasiharmonic model with high accuracy which improves the performance of EOS in the low temperature region.The anharmonic effect is taken into account by using a semi-empirical approach.Its reasonability is verified by the fact that the total thermal pressure tends to the lowest-order anharmonic expansion in the literature at low temperature,and tends to ideal-gas limitation at high temperature,which is physically correct.Besides,based on this approach,the anharmonic thermal pressure can be expressed in the Grüineisen form,which is convenient for applications.The proposed EOS is used to study the thermodynamic properties of MgO including static and shock compression conditions,and the results are very satisfactory as compared with the experimental data.
Cluster Model for Wave-Like Motions of a 2D Vertically Vibrated Granular System
International Nuclear Information System (INIS)
The fact that trapezoid clusters exist in 2D vertically vibrated granular systems leads us to construct a cluster model, in which wave-like motions are explained as the result of cluster-plate and cluster-cluster collisions. By analyzing the collision of one cluster with the plate in detail, we deduce a basic equation from velocity relationship, which could be separated into two correlative equations: one relates wave-like motion with exciting acceleration, and we call it the excitation condition; the other relates wavelength with exciting frequency, viz., the dispersion relation. The theoretical results are in agreement with the experimental ones, which supports the idea of the cluster model. Moreover, from the cluster model, we also predict a possibility of abnormal dispersion relation of a 2D granular system. (fundamental areas of phenomenology(including applications))
Size-dependent vibrational behavior of a Jeffcott model for micro-rotor systems
Energy Technology Data Exchange (ETDEWEB)
Hashemi, Mehdi; Asghari, Mohsen [Sharif University of Technology, Tehran (Iran, Islamic Republic of)
2016-01-15
In this study, several analytical expressions are obtained for the vibrational characteristics of a Jeffcott model for micro-rotor systems based on the strain gradient theory to investigate the small-scale effects on the model. The Jeffcott model consists of a massless microrotating shaft and a disk as a rotor with eccentricity. The disk is mounted on the middle of the shaft. Two second-order differential equations associated with the oscillating motion of the rotor in the plane perpendicular to the longitudinal axis are presented and transformed into a complex form. The stiffness of the system is determined by obtaining the deflection of a strain-gradient-based nonrotating microbeam subjected to a concentrated force at the rotor position. Numerical results illustrate the effect of higher-order material constants on the natural frequency and the response of the Jeffcott micro-rotor system with eccentricity.
Xu, Tengfei; Castel, Arnaud
2016-04-01
In this paper, a model, initially developed to calculate the stiffness of cracked reinforced concrete beams under static loading, is used to assess the dynamic stiffness. The model allows calculating the average inertia of cracked beams by taking into account the effect of bending cracks (primary cracks) and steel-concrete bond damage (i.e. interfacial microcracks). Free and forced vibration experiments are used to assess the performance of the model. The respective influence of bending cracks and steel-concrete bond damage on both static and dynamic responses is analyzed. The comparison between experimental and simulated deflections confirms that the effects of both bending cracks and steel-concrete bond loss should be taken into account to assess reinforced concrete stiffness under service static loading. On the contrary, comparison of experimental and calculated dynamic responses reveals that localized steel-concrete bond damages do not influence significantly the dynamic stiffness and the fundamental frequency.
Dynamic test and finite element model updating of bridge structures based on ambient vibration
Institute of Scientific and Technical Information of China (English)
2008-01-01
The dynamic characteristics of bridge structures are the basis of structural dynamic response and seismic analysis,and are also an important target of health condition monitoring.In this paper,a three-dimensional finite-element model is first established for a highway bridge over a railroad on No.312 National Highway.Based on design drawings,the dynamic characteristics of the bridge are studied using finite element analysis and ambient vibration measurements.Thus,a set of data is selected based on sensitivity analysis and optimization theory;the finite element model of the bridge is updated.The numerical and experimental results show that the updated method is more simple and effective,the updated finite element model can reflect the dynamic characteristics of the bridge better,and it can be used to predict the dynamic response under complex external forces.It is also helpful for further damage identification and health condition monitoring.
Modeling of hydrogen ground state rotational and vibrational temperatures in kinetic plasmas
International Nuclear Information System (INIS)
A dipole-quadrupole electron-impact excitation model, consistent with molecular symmetry rules, is presented to fit ro-vibronic spectra of the hydrogen Fulcher-α Q-branch line emissions for passively measuring the rotational temperature of hydrogen neutral molecules in kinetic plasmas with the coronal equilibrium approximation. A quasi-rotational temperature and quadrupole contribution factor are adjustable parameters in the model. Quadrupole excitation is possible due to a violation of the 1st Born approximation for low to medium energy electrons (up to several hundred eV). The Born-Oppenheimer and Franck-Condon approximations are implicitly shown to hold. A quadrupole contribution of 10% is shown to fit experimental data at several temperatures from different experiments with electron energies from several to 100 eV. A convenient chart is produced to graphically determine the vibrational temperature of the hydrogen molecules from diagonal band intensities, if the ground state distribution is Boltzmann. Hydrogen vibrational modes are long-lived, surviving up to thousands of wall collisions, consistent with multiple other molecular dynamics computational results. The importance of inter-molecular collisions during a plasma pulse is also discussed.
Reliability estimation for cutting tools based on logistic regression model using vibration signals
Chen, Baojia; Chen, Xuefeng; Li, Bing; He, Zhengjia; Cao, Hongrui; Cai, Gaigai
2011-10-01
As an important part of CNC machine, the reliability of cutting tools influences the whole manufacturing effectiveness and stability of equipment. The present study proposes a novel reliability estimation approach to the cutting tools based on logistic regression model by using vibration signals. The operation condition information of the CNC machine is incorporated into reliability analysis to reflect the product time-varying characteristics. The proposed approach is superior to other degradation estimation methods in that it does not necessitate any assumption about degradation paths and probability density functions of condition parameters. The three steps of new reliability estimation approach for cutting tools are as follows. First, on-line vibration signals of cutting tools are measured during the manufacturing process. Second, wavelet packet (WP) transform is employed to decompose the original signals and correlation analysis is employed to find out the feature frequency bands which indicate tool wear. Third, correlation analysis is also used to select the salient feature parameters which are composed of feature band energy, energy entropy and time-domain features. Finally, reliability estimation is carried out based on logistic regression model. The approach has been validated on a NC lathe. Under different failure threshold, the reliability and failure time of the cutting tools are all estimated accurately. The positive results show the plausibility and effectiveness of the proposed approach, which can facilitate machine performance and reliability estimation.
Cardona-Morales, O.; Avendaño, L. D.; Castellanos-Domínguez, G.
2014-02-01
Condition monitoring of mechanical systems is an important topic for industry since it improves machine maintenance and reduce the total associated operational cost. In this sense, vibration analysis is a useful tool for failure prevention in rotating machines, and its main challenge is to perform on-line estimation of dynamic behavior, due to non-stationary operating conditions. To this, estimation of both, amplitude and instantaneous frequency, holding most of process information should be carried out. Nevertheless, approaches for estimating those parameters require to have the shaft speed reference signal, which is not always provided in several industrial applications. In this paper, a novel Order Tracking (OT) scheme of estimation is proposed that is based on the state space model that avoids the shaft speed reference signal. The nonlinear oscillatory model designed as frequency tracker is adapted for estimating the phase and the amplitude of each particular harmonic component. Specifically, nonlinear filtering (namely, the Square-Root Cubature Kalman Filter) is used to estimate the spectral components from the vibration signal. The proposed approach is tested and compared with baseline Vold-Kalman Filtering over four different datasets. The obtained results show that proposed approach is robust and it performs with high accuracy estimation of the order component and the instantaneous frequency under different operating conditions; both allow capturing machine dynamic behavior.
Fu, Jie; Li, Peidong; Wang, Yuan; Liao, Guanyao; Yu, Miao
2016-03-01
This paper addresses the problem of micro-vibration control of a precision vibration isolation system with a magnetorheological elastomer (MRE) isolator and fuzzy control strategy. Firstly, a polyurethane matrix MRE isolator working in the shear-compression mixed mode is introduced. The dynamic characteristic is experimentally tested, and the range of the frequency shift and the model parameters of the MRE isolator are obtained from experimental results. Secondly, a new semi-active control law is proposed, which uses isolation structure displacement and relative displacement between the isolation structure and base as the inputs. Considering the nonlinearity of the MRE isolator and the excitation uncertainty of an isolation system, the designed semi-active fuzzy logic controller (FLC) is independent of a system model and is robust. Finally, the numerical simulations and experiments are conducted to evaluate the performance of the FLC with single-frequency and multiple-frequency excitation, respectively, and the experimental results show that the acceleration transmissibility is reduced by 54.04% at most, which verifies the effectiveness of the designed semi-active FLC. Moreover, the advantages of the approach are demonstrated in comparison to the passive control and ON-OFF control.
International Nuclear Information System (INIS)
Extensive research has been done on the topics of both turbulence-induced vibration and vibration based energy harvesting; however, little effort has been put into bringing these two topics together. Preliminary experimental studies have shown that piezoelectric structures excited by turbulent flow can produce significant amounts of useful power. This research could serve to benefit applications such as powering remote, self-sustained sensors in small rivers or air ventilation systems where turbulent fluid flow is a primary source of ambient energy. A novel solution for harvesting energy in these unpredictable fluid flow environments was explored by the authors in previous work, and a harvester prototype was developed. This prototype, called piezoelectric grass, has been the focus of many experimental studies. In this paper the authors present a theoretical analysis of the piezoelectric grass harvester modeled as a single unimorph cantilever beam exposed to turbulent cross-flow. This distributed parameter model was developed using a combination of both analytical and statistical techniques. The analytical portion uses a Rayleigh–Ritz approximation method to describe the beam dynamics, and utilizes piezoelectric constitutive relationships to define the electromechanical coupling effects. The statistical portion of the model defines the turbulence-induced forcing function distributed across the beam surface. The model presented in this paper was validated using results from several experimental case studies. Preliminary results show that the model agrees quite well with experimental data. A parameter optimization study was performed with the proposed model. This study demonstrated how a new harvester could be designed to achieve maximum power output in a given turbulent fluid flow environment. (paper)
Thermodynamics of Anharmonic Systems: Uncoupled Mode Approximations for Molecules.
Li, Yi-Pei; Bell, Alexis T; Head-Gordon, Martin
2016-06-14
The partition functions, heat capacities, entropies, and enthalpies of selected molecules were calculated using uncoupled mode (UM) approximations, where the full-dimensional potential energy surface for internal motions was modeled as a sum of independent one-dimensional potentials for each mode. The computational cost of such approaches scales the same with molecular size as standard harmonic oscillator vibrational analysis using harmonic frequencies (HO(hf)). To compute thermodynamic properties, a computational protocol for obtaining the energy levels of each mode was established. The accuracy of the UM approximation depends strongly on how the one-dimensional potentials of each modes are defined. If the potentials are determined by the energy as a function of displacement along each normal mode (UM-N), the accuracies of the calculated thermodynamic properties are not significantly improved versus the HO(hf) model. Significant improvements can be achieved by constructing potentials for internal rotations and vibrations using the energy surfaces along the torsional coordinates and the remaining vibrational normal modes, respectively (UM-VT). For hydrogen peroxide and its isotopologs at 300 K, UM-VT captures more than 70% of the partition functions on average. By contrast, the HO(hf) model and UM-N can capture no more than 50%. For a selected test set of C2 to C8 linear and branched alkanes and species with different moieties, the enthalpies calculated using the HO(hf) model, UM-N, and UM-VT are all quite accurate comparing with reference values though the RMS errors of the HO model and UM-N are slightly higher than UM-VT. However, the accuracies in entropy calculations differ significantly between these three models. For the same test set, the RMS error of the standard entropies calculated by UM-VT is 2.18 cal mol(-1) K(-1) at 1000 K. By contrast, the RMS error obtained using the HO model and UM-N are 6.42 and 5.73 cal mol(-1) K(-1), respectively. For a test set
Anharmonic parametric excitation in optical lattices
Jauregui, R; Roati, G; Modugno, G
2001-01-01
We study both experimentally and theoretically the losses induced by parametric excitation in far-off-resonance optical lattices. The atoms confined in a 1D sinusoidal lattice present an excitation spectrum and dynamics substantially different from those expected for a harmonic potential. We develop a model based on the actual atomic Hamiltonian in the lattice and we introduce semiempirically a broadening of the width of lattice energy bands which can physically arise from inhomogeneities and fluctuations of the lattice, and also from atomic collisions. The position and strength of the parametric resonances and the evolution of the number of trapped atoms are satisfactorily described by our model.
Modeling and optimal vibration control of conical shell with piezoelectric actuators
Institute of Scientific and Technical Information of China (English)
Wang Weiyuan; Wei Yingjie; Wang Cong; Zou Zhenzhu
2008-01-01
In this paper numerical simulations of active vibration control for conical shell structure with distributed piezoelectric actuators is presented. The dynamic equations of conical shell structure are derived using the finite element model (FEM) based on Mindlin's plate theory. The results of modal calculations with FEM model are accurate enough for engineering applications in comparison with experiment results. The Electromechanical influence of distributed piezoelectric actuators is treated as a boundary condition for estimating the control force. The independent modal space control (IMSC) method is adopted and the optimal linear quadratic state feedback control is implemented so that the best control performance with the least control cost can be achieved. Optimal control effects are compared with controlled responses with other non-optimal control parameters. Numerical simulation results are given to demonstrate the effectiveness of the control scheme.
Bailly, Lucie; Henrich, Nathalie; Pelorson, Xavier
2010-05-01
Occurrences of period-doubling are found in human phonation, in particular for pathological and some singing phonations such as Sardinian A Tenore Bassu vocal performance. The combined vibration of the vocal folds and the ventricular folds has been observed during the production of such low pitch bass-type sound. The present study aims to characterize the physiological correlates of this acoustical production and to provide a better understanding of the physical interaction between ventricular fold vibration and vocal fold self-sustained oscillation. The vibratory properties of the vocal folds and the ventricular folds during phonation produced by a professional singer are analyzed by means of acoustical and electroglottographic signals and by synchronized glottal images obtained by high-speed cinematography. The periodic variation in glottal cycle duration and the effect of ventricular fold closing on glottal closing time are demonstrated. Using the detected glottal and ventricular areas, the aerodynamic behavior of the laryngeal system is simulated using a simplified physical modeling previously validated in vitro using a larynx replica. An estimate of the ventricular aperture extracted from the in vivo data allows a theoretical prediction of the glottal aperture. The in vivo measurements of the glottal aperture are then compared to the simulated estimations. PMID:21117769
International Nuclear Information System (INIS)
The absorption spectrum of the 18O3 isotopologue of ozone is recorded by CW-Cavity Ring Down Spectroscopy between 7400 and 7920 cm−1. The typical noise equivalent absorption of the recordings is αmin≈1×10−10 cm−1 allowing for the detection of extremely weak vibrational bands located only a few % below the dissociation limit. The absorption spectrum also includes the weak 3A2(000)–X(110) hot vibronic band at 7877.53 cm−1 affected by predissociation broadening. Overall, about 1000 lines were rovibrationnally assigned to six vibrational bands. Their line positions were modelled using effective Hamiltonian models covering three vibrational interacting systems and involving several “dark” states perturbing observed transitions. Line positions could be reproduced with rms deviations on the order of 0.01 cm−1. The dipole transition moment parameters of the six bands were determined from the retrieved line intensities. The obtained set of effective parameters and the experimentally determined energy levels were used to generate a list of 1461 transitions provided as Supplementary materials. - Highlights: • Cavity Ring Down Spectroscopy of 18O3 between 7400 and 7920 cm−1. • 1017 Transitions assigned to six A-type vibrational bands. • Upper vibrational states located a few % below the dissociation limit at 8560 cm−1. • Effective operator modelling of the spectra. • Good agreement with ab initio values for the band centres and rotational constants
DEFF Research Database (Denmark)
Bucinskas, Paulius; Andersen, Lars Vabbersgaard; Persson, Kent
2016-01-01
Construction of high speed railway lines has been an increasing trend in recent years. Countries like Denmark and Sweden plan to expand and upgrade their railways to accommodate high-speed traffic. To benefit from the full potential of the reduced commuting times, these lines must pass through...... densely populated urban areas with the collateral effect of increased noise and vibrations levels. This paper aims to quantify the vibrations levels in the area surrounding an elevated railway line built as a multi-span bridge structure. The proposed model employs finite-element analysis to model the...
International Nuclear Information System (INIS)
This paper describes the latest status of the fabrication and testing of a sub-scaled tokamak model for the vibration test to validate numerical analysis on seismic response of fusion reactor. The sub-scale model referred to the 1998 ITER design and the scale was decided as to be 1/8 considering the capacity of test facility and the scaling ratio was chosen so that the stress becomes equivalent to that of the real machine. The partial test had been performed with the gravity supports and TF coil case, and their vibration characteristics were verified. (author)
Calculation of anharmonic couplings and THz linewidths in crystalline PETN
International Nuclear Information System (INIS)
We have developed a method for calculating the cubic anharmonic couplings in molecular crystals for normal modes with the zero wave vector in the framework of classical mechanics, and have applied it, combined with perturbation theory, to obtain the linewidths of all infrared absorption lines of crystalline pentaerythritol tetranitrate in the terahertz region (−1). Contributions of the up- and down-conversion processes to the total linewidth were calculated. The computed linewidths are in qualitative agreement with experimental data and the results of molecular dynamics simulations. Quantum corrections to the linewidths in the terahertz region are shown to be negligible
Analytic WKB energy expressions for three-dimensional anharmonic oscillators
International Nuclear Information System (INIS)
A direct evaluation of the lowest-order WKB integral for three-dimensional quartic (V(r)=r4) and quartic anharmonic (V(r)=1/2ω2r2 + lambdar4) oscillators is carried out. The highly implicit relation for the energy defined by the WKB quantisation condition is expressed in terms of complete elliptic integrals. An approximate non-perturbative inversion of the implicit relation provides explicit analytic expressions for the energy which reproduce known energy values quite accurately. (author)
Perfect Lattice Perturbation Theory A Study of the Anharmonic Oscillator
Bietenholz, W
1999-01-01
As an application of perfect lattice perturbation theory, we construct an O(\\lambda) perfect lattice action for the anharmonic oscillator analytically in momentum space. In coordinate space we obtain a set of 2-spin and 4-spin couplings \\propto \\lambda, which we evaluate for various masses. These couplings never involve variables separated by more than two lattice spacings. The O(\\lambda) perfect action is simulated and compared to the standard action. We discuss the improvement for the first two energy gaps \\Delta E_1, \\Delta E_2 and for the scaling quantity \\Delta E_2 / \\Delta E1 in different regimes of the interaction parameter, and of the correlation length.
Effect of Anharmonicity on the Phonon Spectrum near its Discontinuity
International Nuclear Information System (INIS)
The method based on Green's function is used in investigating the effect of anharmonicity on the phonon spectrum near its discontinuity. In contrast to the usual case, the effect that phonon branches, which are independent in the harmonic approximation, have on one another requires the solution of the Dyson system of equations. The authors consider cases of significant and irregular discontinuity and show that for irregular discontinuity the excitations which arise can have a widely varying lifetime and frequency renormalization with respect to both value and temperature dependence. In particular, the one-phonon coherent neutron scattering cross section near the spectrum discontinuity is analysed. (author)
Energy Technology Data Exchange (ETDEWEB)
Zhou, Fei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nielson, Weston [Univ. of California, Los Angeles, CA (United States); Xia, Yi [Univ. of California, Los Angeles, CA (United States); Ozoliņš, Vidvuds [Univ. of California, Los Angeles, CA (United States)
2014-10-01
First-principles prediction of lattice thermal conductivity κ_{L} of strongly anharmonic crystals is a long-standing challenge in solid-state physics. Making use of recent advances in information science, we propose a systematic and rigorous approach to this problem, compressive sensing lattice dynamics. Compressive sensing is used to select the physically important terms in the lattice dynamics model and determine their values in one shot. Nonintuitively, high accuracy is achieved when the model is trained on first-principles forces in quasirandom atomic configurations. The method is demonstrated for Si, NaCl, and Cu_{12}Sb_{4}S_{13}, an earth-abundant thermoelectric with strong phonon-phonon interactions that limit the room-temperature κ_{L} to values near the amorphous limit.
Lokhov, Alexey V
2016-01-01
Data analysis of the next generation effective antineutrino mass measurement experiment KATRIN requires reliable knowledge of systematic corrections. In particular, the width of the daughter molecular ion excitation spectrum rovibrational band should be known with a better then 1% precision. Very precise ab initio quantum calculations exist, and we compare them with the well known tritium molecule parameters within the framework of a phenomenological model. The rovibrational band width with accuracy of a few percent is interpreted as a result of the zero-point atomic oscillation in the harmonic potential. The Morse interatomic potential is used to investigate the impact of anharmonic atomic oscillations. The calculated corrections cannot account for the difference between the ab initio quantum calculations and the phenomenological model.
Nonlinear spectroscopy of superconducting anharmonic resonators
DiVincenzo, David P
2011-01-01
We formulate a model for the steady state response of a nonlinear quantum oscillator structure, such as those used in a variety of superconducting qubit experiments, when excited by a steady, but not necessarily small, ac tone. We show that this model can be derived directly from a circuit description of some recent qubit experiments in which the state of the qubit is read out directly, without a SQUID magnetometer. The excitation profile has a rich structure depending on the detuning of the tone from the small-signal resonant frequency, on the degree of damping, and on the excitation amplitude. We explore two regions in detail: First, at high damping there is a trough in the excitation response as a function of detuning, near where the classical Duffing bifurcation occurs. This trough has been understood as a classical interference between two metastable responses with opposite phase. We use Wigner function studies to show that while this picture is roughly correct, there are also more quantum mechanical asp...
Nonlinear spectroscopy of superconducting anharmonic resonators
International Nuclear Information System (INIS)
We formulate a model for the steady state response of a nonlinear quantum oscillator structure, such as those used in a variety of superconducting qubit experiments, when excited by a steady, but not necessarily small, ac tone. We show that this model can be derived directly from a circuit description of some recent qubit experiments in which the state of the qubit is read out directly, without a superconducting quantum interference device (SQUID) magnetometer. The excitation profile has a rich structure depending on the detuning of the tone from the small-signal resonant frequency, on the degree of damping and on the excitation amplitude. We explore two regions in detail. Firstly, at high damping there is a trough in the excitation response as a function of detuning, near where the classical Duffing bifurcation occurs. This trough has been understood as a classical interference between two metastable responses with opposite phase. We use Wigner function studies to show that while this picture is roughly correct, there are also more quantum mechanical aspects to this feature. Secondly, at low damping we study the emergence of sharp, discrete spectral features from a continuum response. We show that these the structures, associated with discrete transitions between different excited-state eigenstates of the oscillator, provide an interesting example of a quantum Fano resonance. The trough in the Fano response evolves continuously from the ‘classical’ trough at high damping. (paper)
Perry, David S.; Miller, Anthony; Amyay, Badr; Fayt, André; Herman, Michel
2010-04-01
The link between energy-resolved spectra and time-resolved dynamics is explored quantitatively for acetylene (12C2H2), ? with up to 8600 cm-1 of vibrational energy. This comparison is based on the extensive and reliable knowledge of the vibration-rotation energy levels and on the model Hamiltonian used to fit them to high precision [B. Amyay, S. Robert, M. Herman, A. Fayt, B. Raghavendra, A. Moudens, J. Thiévin, B. Rowe, and R. Georges, J. Chem. Phys. 131, 114301 (2009)]. Simulated intensity borrowing features in high resolution absorption spectra and predicted survival probabilities in intramolecular vibrational redistribution (IVR) are first investigated for the v 4 + v 5 and v 3 bright states, for J = 2, 30 and 100. The dependence of the results on the rotational quantum number and on the choice of vibrational bright state reflects the interplay of three kinds of off-diagonal resonances: anharmonic, rotational l-type, and Coriolis. The dynamical quantities used to characterize the calculated time-dependent dynamics are the dilution factor φ d, the IVR lifetime τ IVR , and the recurrence time τ rec. For the two bright states v 3 + 2v 4 and 7v 4, the collisionless dynamics for thermally averaged rotational distributions at T = 27, 270 and 500 K were calculated from the available spectroscopic data. For the 7v 4 bright state, an apparent irreversible decay of is found. In all cases, the model Hamiltonian allows a detailed calculation of the energy flow among all of the coupled zeroth-order vibration-rotation states.
Resummation of divergent perturbation series: Application to the vibrational states of H2CO molecule
International Nuclear Information System (INIS)
Large-order Rayleigh–Schrödinger perturbation theory (RSPT) is applied to the calculation of anharmonic vibrational energy levels of H2CO molecule. We use the model of harmonic oscillators perturbed by anharmonic terms of potential energy. Since the perturbation series typically diverge due to strong couplings, we apply the algebraic approximation technique because of its effectiveness shown earlier by Goodson and Sergeev [J. Chem. Phys. 110, 8205 (1999); ibid. 124, 094111 (2006)] and in our previous articles [A. D. Bykov et al. Opt. Spectrosc. 114, 396 (2013); ibid. 116, 598 (2014)]. To facilitate the resummation of terms contributing to perturbed states, when resonance mixing between states is especially strong and perturbation series diverge very quick, we used repartition of the Hamiltonian by shifting the normal mode frequencies. Energy levels obtained by algebraic approximants were compared with the results of variational calculation. It was found that for low energy states (up to ∼5000 cm−1), algebraic approximants gave accurate values of energy levels, which were in excellent agreement with the variational method. For highly excited states, strong and multiple resonances complicate series resummation, but a suitable change of normal mode frequencies allows one to reduce the resonance mixing and to get accurate energy levels. The theoretical background of the problem of RSPT series divergence is discussed along with its numerical analysis. For these purposes, the vibrational energy is considered as a function of a complex perturbation parameter. Layout and classification of its singularities allow us to model the asymptotic behavior of the perturbation series and prove the robustness of the algorithm
Godtliebsen, Ian H; Christiansen, Ove
2015-10-01
It is demonstrated how vibrational IR and Raman spectra can be calculated from damped response functions using anharmonic vibrational wave function calculations, without determining the potentially very many eigenstates of the system. We present an implementation for vibrational configuration interaction and vibrational coupled cluster, and describe how the complex equations can be solved using iterative techniques employing only real trial vectors and real matrix-vector transformations. Using this algorithm, arbitrary frequency intervals can be scanned independent of the number of excited states. Sample calculations are presented for the IR-spectrum of water, Raman spectra of pyridine and a pyridine-silver complex, as well as for the infra-red spectrum of oxazole, and vibrational corrections to the polarizability of formaldehyde. PMID:26450293
Vibration of hydraulic machinery
Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong
2013-01-01
Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...
Zhao, Zhi-li; Qiu, Zhi-cheng; Zhang, Xian-min; Han, Jian-da
2016-03-01
A kind of hybrid pneumatic-piezoelectric flexible manipulator system has been presented in the paper. A hybrid driving scheme is achieved by combining of a pneumatic proportional valve based pneumatic drive and a piezoelectric actuator bonded to the flexible beam. The system dynamics models are obtained based on system identification approaches, using the established experimental system. For system identification of the flexible piezoelectric manipulator subsystem, parametric estimation methods are utilized. For the pneumatic driven system, a single global linear model is not accurate enough to describe its dynamics, due to the high nonlinearity of the pneumatic driven system. Therefore, a self-organizing map (SOM) based multi-model system identification approach is used to get multiple local linear models. Then, a SOM based multi-model inverse controller and a variable damping pole-placement controller are applied to the pneumatic drive and piezoelectric actuator, respectively. Experiments on pneumatic driven vibration control, piezoelectric vibration control and hybrid vibration control are conducted, utilized proportional and derivative (PD) control, SOM based multi-model inverse controller, and the variable damping pole-placement controller. Experimental results demonstrate that the investigated control algorithms can improve the vibration control performance of the pneumatic driven flexible piezoelectric manipulator system.
Structural and vibrational properties of Co nanoparticles formed by ion implantation
Energy Technology Data Exchange (ETDEWEB)
Sprouster, D.J.; Giulian, R.; Araujo, L.L.; Kluth, P.; Johannessen, B.; Cookson, D.J.; Foran, G.J.; Ridgway, M.C. (Aust. Synch.); (ANU)
2010-02-19
We report on the structural and vibrational properties of Co nanoparticles formed by ion implantation and thermal annealing in amorphous silica. The evolution of the nanoparticle size, phase, and structural parameters were determined as a function of the formation conditions using transmission electron microscopy, small-angle x-ray scattering, and x-ray absorption spectroscopy. The implantation fluence and annealing temperature governed the spherical nanoparticle size and phase. To determine the latter, x-ray absorption near-edge structure analysis was used to quantify the hexagonal close packed, face-centered cubic and oxide fractions. The structural properties were characterized by extended x-ray absorption fine structure spectroscopy (EXAFS) and finite-size effects were readily apparent. With a decrease in nanoparticle size, an increase in structural disorder and a decrease in both coordination number and bondlength were observed as consistent with the non-negligible surface-area-to-volume ratio characteristic of nanoparticles. The surface tension of Co nanoparticles calculated using a liquid drop model was more than twice that of bulk material. The size-dependent vibrational properties were probed with temperature-dependent EXAFS measurements. Using a correlated anharmonic Einstein model and thermodynamic perturbation theory, Einstein temperatures for both nanoparticles and bulk material were determined. Compared to bulk Co, the mean vibrational frequency of the smallest nanoparticles was reduced as attributed to a greater influence of loosely bonded, undercoordinated surface atoms relative to the effect of capillary pressure generated by surface curvature.
International Nuclear Information System (INIS)
In this study, sandwich beam model (SM) is proposed for free vibration analysis of bilayer graphene nanoribbons (BLGNRs) with interlayer shear effect. This model also takes into account the intralayer (in-plane) stretch of graphene nanoribbons. The molecular dynamics (MD) simulations using the software LAMMPS and Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential are done to validate the accuracy of the sandwich model results. The MD simulation results include the two first frequencies of cantilever BLGNRs with different lengths and two interlayer shear moduli, i.e., 0.25 and 4.6 GPa. These two interlayer shear moduli, 0.25 and 4.6 GPa, can be obtained by sliding a small flake of graphene on a large graphene substrate when the parameter of E-LJ term in AIREBO potential, epsilon-CC, is set to be 2.84 and 45.44 meV, respectively. The SM results for a wide range of bending rigidity values show that the proposed model, i.e., the SM, predicts much better than the previous beam model in which the intralayer stretch is ignored. In addition, it is observed that the model can properly predict the natural frequencies of BLGNRs for various values of the bending rigidity and the interlayer shear modulus
Energy Technology Data Exchange (ETDEWEB)
Nazemnezhad, Reza, E-mail: rnazemnezhad@iust.ac.ir, E-mail: rnazemnezhad@du.ac.ir [School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Shokrollahi, Hassan [School of Mechanical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Hosseini-Hashemi, Shahrokh [School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Center of Excellence in Railway Transportation, Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of)
2014-05-07
In this study, sandwich beam model (SM) is proposed for free vibration analysis of bilayer graphene nanoribbons (BLGNRs) with interlayer shear effect. This model also takes into account the intralayer (in-plane) stretch of graphene nanoribbons. The molecular dynamics (MD) simulations using the software LAMMPS and Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential are done to validate the accuracy of the sandwich model results. The MD simulation results include the two first frequencies of cantilever BLGNRs with different lengths and two interlayer shear moduli, i.e., 0.25 and 4.6 GPa. These two interlayer shear moduli, 0.25 and 4.6 GPa, can be obtained by sliding a small flake of graphene on a large graphene substrate when the parameter of E-LJ term in AIREBO potential, epsilon-CC, is set to be 2.84 and 45.44 meV, respectively. The SM results for a wide range of bending rigidity values show that the proposed model, i.e., the SM, predicts much better than the previous beam model in which the intralayer stretch is ignored. In addition, it is observed that the model can properly predict the natural frequencies of BLGNRs for various values of the bending rigidity and the interlayer shear modulus.
Soil-Pile Interaction in the Pile Vertical Vibration Based on Fictitious Soil-Pile Model
Directory of Open Access Journals (Sweden)
Guodong Deng
2014-01-01
Full Text Available By introducing the fictitious soil-pile model, the soil-pile interaction in the pile vertical vibration is investigated. Firstly, assuming the surrounding soil of pile to be viscoelastic material and considering its vertical wave effect, the governing equations of soil-pile system subjected to arbitrary harmonic dynamic force are founded based on the Euler-Bernoulli rod theory. Secondly, the analytical solution of velocity response in frequency domain and its corresponding semianalytical solution of velocity response in time domain are derived by means of Laplace transform technique and separation of variables technique. Based on the obtained solutions, the influence of parameters of pile end soil on the dynamic response is studied in detail for different designing parameters of pile. Lastly, the fictitious soil-pile model and other pile end soil supporting models are compared. It is shown that the dynamic response obtained by the fictitious soil-pile model is among the dynamic responses obtained by other existing models if there are appropriate material parameters and thickness of pile end soil for the fictitious soil-pile model.
Anharmonicity in light scattering by optical phonons in GaAs1-xBix
Joshya, R. S.; Rajaji, V.; Narayana, Chandrabhas; Mascarenhas, A.; Kini, R. N.
2016-05-01
We present a Raman spectroscopic study of GaAs1-xBix epilayers grown by molecular beam epitaxy. We have investigated the anharmonic effect on the GaAs-like longitudinal optical phonon mode ( LOGaAs' ) of GaAs1-xBix for different Bi concentrations at various temperatures. The results are analyzed in terms of the anharmonic damping effect induced by thermal and compositional disorder. We have observed that the anharmonicity increases with Bi concentration in GaAs1-xBix as evident from the increase in the anharmonicity constants. In addition, the anharmonic lifetime of the optical phonon decreases with increasing Bi concentration in GaAs1-xBix.
Anharmonicity in Light Scattering by Optical Phonons in GaAs1-xBix
Energy Technology Data Exchange (ETDEWEB)
Joshya, R. S.; Rajaji, V.; Narayana, Chandrabhas; Mascarenhas, Angelo; Kini, R. N.
2016-05-28
We present a Raman spectroscopic study of GaAs 1-xBix epilayers grown by molecular beam epitaxy. We have investigated the anharmonic effect on the GaAs-like longitudinal optical phonon mode (LO'GaAs) of GaAs 1-xBix for different Bi concentrations at various temperatures. The results are analyzed in terms of the anharmonic damping effect induced by thermal and compositional disorder. We have observed that the anharmonicity increases with Bi concentration in GaAs 1-xBix as evident from the increase in the anharmonicity constants. In addition, the anharmonic lifetime of the optical phonon decreases with increasing Bi concentration in GaAs 1-xBix.
Directory of Open Access Journals (Sweden)
Suhir E.
2012-08-01
Full Text Available Some basic problems of the dynamic response of electronic and photonic (E&P systems to shocks and vibrations are addressed and discussed. The emphasis is on analytical (mathematical modeling, the reliability physics behind the addressed phenomena, and design-for-reliability (DfR issues and challenges. The addressed problems include 1 linear response: effect of viscous damping, shock tests vs. drop tests, role of compliant interfaces, and maximum acceleration and maximum dynamic stress as a suitable reliability criterion; 2 nonlinear response: printed circuit board (PCB experiencing an impact load applied to its support contour and ball-grid-array (BGA testing on the board level; 3 shock protection of portable electronics, including the possible use of nano-wires as a suitable protective “cushion”. The fruitfulness of the probabilistic DfR (PDfR concept to quantify and assure the field (operational reliability of E&P devices and systems is also indicated.
Corrections to vibrational transition probabilities calculated from a three-dimensional model.
Stallcop, J. R.
1972-01-01
Corrections to the collision-induced vibration transition probability calculated by Hansen and Pearson from a three-dimensional semiclassical model are examined. These corrections come from the retention of higher order terms in the expansion of the interaction potential and the use of the actual value of the deflection angle in the calculation of the transition probability. It is found that the contribution to the transition cross section from previously neglected potential terms can be significant for short range potentials and for the large relative collision velocities encountered at high temperatures. The correction to the transition cross section obtained from the use of actual deflection angles will not be appreciable unless the change in the rotational quantum number is large.
Application of Tube-Packaged FBG Strain Sensor in Vibration Experiment of Submarine Pipeline Model
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Optical fiber sensors have received increasing attention in the fields of aeronautic and civil engineering for their superior ability to stand explosion, immunity to electromagnetic interference and high accuracy, especially fit for measurement applications in harsh environment. In this study, a novel FBG (fiber Bragg grating) strain sensor, which is packaged in a 1.2 mm stainless steel tube with epoxy resin, is developed. Experiments are conducted on the universal material testing machine to calibrate its strain transferring characteristics. The sensor has the advantages of small size, high precision and flexible use, and exhibits promising potentials. Five tube-packaged strain FBG sensors have been applied to the vibration experiment of a submarine pipeline model. The strain measured with the FBG sensor agrees well with that measured with the electric resistance strain sensor.
Malago`, M.; Mucchi, E.; Dalpiaz, G.
2016-03-01
Heavy duty wheels are used in applications such as automatic vehicles and are mainly composed of a polyurethane tread glued to a cast iron hub. In the manufacturing process, the adhesive application between tread and hub is a critical assembly phase, since it is completely made by an operator and a contamination of the bond area may happen. Furthermore, the presence of rust on the hub surface can contribute to worsen the adherence interface, reducing the operating life. In this scenario, a quality control procedure for fault detection to be used at the end of the manufacturing process has been developed. This procedure is based on vibration processing techniques and takes advantages of the results of a lumped parameter model. Indicators based on cyclostationarity can be considered as key parameters to be adopted in a monitoring test station at the end of the production line due to their not deterministic characteristics.
System reliability of randomly vibrating structures: Computational modeling and laboratory testing
Sundar, V. S.; Ammanagi, S.; Manohar, C. S.
2015-09-01
The problem of determination of system reliability of randomly vibrating structures arises in many application areas of engineering. We discuss in this paper approaches based on Monte Carlo simulations and laboratory testing to tackle problems of time variant system reliability estimation. The strategy we adopt is based on the application of Girsanov's transformation to the governing stochastic differential equations which enables estimation of probability of failure with significantly reduced number of samples than what is needed in a direct simulation study. Notably, we show that the ideas from Girsanov's transformation based Monte Carlo simulations can be extended to conduct laboratory testing to assess system reliability of engineering structures with reduced number of samples and hence with reduced testing times. Illustrative examples include computational studies on a 10-degree of freedom nonlinear system model and laboratory/computational investigations on road load response of an automotive system tested on a four-post test rig.
Vibrational relaxation of the H2O bending mode in liquid water.
Larsen, Olaf F A; Woutersen, Sander
2004-12-22
We have studied the vibrational relaxation of the H(2)O bending mode in an H(2)O:HDO:D(2)O isotopic mixture using infrared pump-probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55+/-10 cm(-1) for the H(2)O bending mode, and a value of 400+/-30 fs for its vibrational lifetime. PMID:15606231
Vibrational relaxation of the H2O bending mode in liquid water
Larsen, Olaf F. A.; Woutersen, Sander
2004-12-01
We have studied the vibrational relaxation of the H2O bending mode in an H2O:HDO:D2O isotopic mixture using infrared pump-probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55±10 cm-1 for the H2O bending mode, and a value of 400±30 fs for its vibrational lifetime.
Directory of Open Access Journals (Sweden)
Jiménez-Alonso, J. F.
2014-12-01
Full Text Available Although the scientific community had knowledge of the human induced vibration problems in structures since the end of the 19th century, it was not until the occurrence of the vibration phenomenon happened in the Millennium Bridge (London, 2000 that the importance of the problem revealed and a higher level of attention devoted. Despite the large advances achieved in the determination of the human-structure interaction force, one of the main deficiencies of the existing models is the exclusion of the effect of changes in the footbridge dynamic properties due to the presence of pedestrians. In this paper, the formulation of a human-structure interaction model, addresses these limitations, is carried out and its reliability is verified from previously published experimental results.Aunque la comunidad científica tenía conocimiento de los problemas vibratorios inducidos por peatones en estructuras desde finales del siglo xix, no fue hasta la ocurrencia de los eventos vibratorios acontecidos en la pasarela del Milenio (Londres, 2000, cuando la importancia del problema se puso de manifiesto y se le comenzó a dedicar un mayor nivel de atención. A pesar de los grandes avances alcanzados en la caracterización de la fuerza de interacción peatón-estructura una de las principales deficiencias de los modelos existentes es la exclusión del cambio en las propiedades dinámicas de la pasarela por la presencia de peatones. En este artículo, se presenta la formulación de un modelo de interacción peatón-estructura que intenta dar respuesta a dichas limitaciones, y su validación a partir de resultados experimentales previamente publicados por otros autores.
Modeling of Tool Wear in Vibration Assisted Nano Impact-Machining by Loose Abrasives
Sagil James; Sundaram, Murali M.
2014-01-01
Vibration assisted nano impact-machining by loose abrasives (VANILA) is a novel nanomachining process that combines the principles of vibration assisted abrasive machining and tip-based nanomachining, to perform target specific nanoabrasive machining of hard and brittle materials. An atomic force microscope (AFM) is used as a platform in this process wherein nanoabrasives, injected in slurry between the workpiece and the vibrating AFM probe which is the tool, impact the workpiece and cause na...
Widiyarto, Muhammad Helmi Nur
2006-01-01
Machine tool vibration is a complex subject requiring a multi-disciplinary approach involving the identification and analysis of the vibration sources and characteristics, as well as its direct and indirect effects. Machine tool vibration is influenced and can be characterised by the machine's structural dynamics, the drive system performance and the cutting force generation. Its effect materialises in the form of poor surface finish of the workpiece, accelerated cuttingtool we...
Formulation of human-structure interaction system models for vertical vibration
Caprani, Colin C.; Ahmadi, Ehsan
2016-09-01
In this paper, human-structure interaction system models for vibration in the vertical direction are considered. This work assembles various moving load models from the literature and proposes extension of the single pedestrian to a crowd of pedestrians for the FE formulation for crowd-structure interaction systems. The walking pedestrian vertical force is represented as a general time-dependent force, and the pedestrian is in turn modelled as moving force, moving mass, and moving spring-mass-damper. The arbitrary beam structure is modelled using either a formulation in modal coordinates or finite elements. In each case, the human-structure interaction (HSI) system is first formulated for a single walking pedestrian and then extended to consider a crowd of pedestrians. Finally, example applications for single pedestrian and crowd loading scenarios are examined. It is shown how the models can be used to quantify the interaction between the crowd and bridge structure. This work should find use for the evaluation of existing and new footbridges.
Vibration modeling and testing of bilayer beams for determination of film elastic modulus
International Nuclear Information System (INIS)
Analysis of the main parameters affecting the fundamental vibrating frequency of film/substrate bilayer beams of rectangular cross-section is discussed based on modeling and testing. Initially, the limits of validity of two analytical models to obtain the fundamental frequency of perfectly-bonded bilayer beams in cantilever configuration are determined by comparing the predicted frequencies to a finite element model developed herein. Using a selected analytical formulation, a modeling-assisted methodology is employed to investigate the parameters that are most influential on the determination of the elastic modulus of the film using a vibratory technique. Modeling suggests the use of thin compliant substrates for extracting the modulus of stiff (metallic) films. If the substrate is stiffer than the film, a thicker film is required to yield measurable shifts in the resonant frequency. The elastic modulus of a millimeter-thick thermosetting polymer extracted by this method agrees with the results obtained from conventional tensile testing of the polymer. Measurements carried out on a gold (100 nm)/polysulfone (130 µm) system yield an average elastic modulus of the gold film similar to the values reported in the literature. (paper)
Resonant squeezing and the anharmonic decay of coherent phonons
Fahy, Stephen; Murray, Éamonn D.; Reis, David A.
2016-04-01
We show that the anharmonic decay of large-amplitude coherent phonons in a solid generates strongly enhanced squeezing of the phonon modes near points of the Brillouin zone where energy conservation in the three-phonon decay process is satisfied. The squeezing process leads to temporal oscillations of the mean-square displacement of target modes in resonance with the coherent phonon, which are characteristic of coherent phonon decay and do not occur in the decay of a phonon in a well-defined number state. For realistic material parameters of optically excited group-V semimetals, we predict that this squeezing results in strongly enhanced oscillations of the x-ray diffuse scattering intensity at sharply defined values of the x-ray momentum transfer. Numerical simulations of the phonon dynamics and the x-ray diffuse scattering in optically excited bismuth, using harmonic and anharmonic force parameters calculated with constrained density functional theory, demonstrate oscillations of the diffuse scattering intensity of magnitude 10%-20% of the thermal background at points of the Brillouin zone, where resonance occurs. Such oscillations should be observable using time-resolved optical-pump and x-ray-probe facilities available at current x-ray free-electron laser sources.
Anharmonic lattice interactions in improper ferroelectrics for multiferroic design
International Nuclear Information System (INIS)
The design and discovery of new multiferroics, or materials that display both ferroelectricity and long-range magnetic order, is of fundamental importance for new electronic technologies based on low-power consumption. Far too often, however, the mechanisms causing these properties to arise are incompatible or occur at ordering temperatures below room temperature. One design strategy which has gained considerable interest is to begin with a magnetic material, and find novel ways to induce a spontaneous electric polarization within the structure. To this end, anharmonic interactions coupling multiple lattice modes have been used to lift inversion symmetry in magnetic dielectrics. Here we provide an overview of the microscopic mechanisms by which various types of cooperative atomic displacements result in ferroelectricity through anharmonic multi-mode coupling, as well as the types of materials most conducive to these lattice instabilities. The review includes a description of the origins of the displacive modes, a classification of possible non-polar lattice modes, as well as how their coupling can produce spontaneous polarizations. We then survey the recent improper ferroelectric literature, and describe how the materials discussed fall within a proposed classification scheme, offering new directions for the theoretical design of magnetic ferroelectrics. Finally, we offer prospects for the future discovery of new magnetic improper ferroelectrics, as well as detail remaining challenges and open questions facing this exciting new field. (topical review)
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.
Directory of Open Access Journals (Sweden)
E. Elsherbiny1
2015-08-01
Full Text Available : In This paper reports on the integration of several technologies to realize, by modeling and design the first twodimensional (2D micro power generator which harvesting multi-directional vibration energy from surrounding environmental, which consists of composite cylindrical system with fixed coil and two rounded axial Neodymium permanent magnets.
Verotti, M.; Servadio, P.; Belfiore, N. P.; Bergonzoli, S.
2012-04-01
Both soil compaction and ground vibration are forms of environmental degradation that may be understood in the context of the vehicle-soil interaction process considered (Hildebrand et al., 2008). The transit of tractors on agricultural soil is often the main cause of soil compaction increasing. As known, this can be a serious problems for tillage and sowing and therefore the influence of all the affecting factors have been extensively studied in the last decades in order to understand their impact on the biosystem. There are factors related to the climate, namely to the rainfalls and temperature, and many others. Hence, it is not simple to figure out a complete model for predicting an index of compaction, for a given situation. Soil compaction models are important tools for controlling soil compaction due to agricultural field traffic and they are potentially useful technique to provide information concerning correct soil management. By means of such models, strategies and recommendations for prevention of soil compaction may be developed and specific advice may be given to farmers and advisers. In order to predict field wheeled and tracked vehicle performance, some empirical methods, used for off-road vehicle, were applied by Servadio (2010) on agricultural soil. The empirical indexes included, besides the soil strength, the load carried by the tire or track, some technical characteristics of the tire or track of the vehicle (tire or track width, tire or track wheel diameter, unloaded tire section height, number of wheel station in one track, tire deflection, total length of the belt track, the track pitch) as well as the vehicle passes. They have been validated with the tests results of agricultural vehicles over a range of soil in central Italy. Among the parameters which affect soil compaction, the water content of the soil, the axle load and number of vehicle passes proved to be the most important ones. The present paper concerns mainly vehicle
Massuyeau, Florian; Faulques, Eric; Latouche, Camille; Barone, Vincenzo
2016-07-28
The structure, spectroscopic parameters and optical properties of stilbene have been investigated by a computational protocol including suitable treatment of anharmonic contributions together with new experimental results. A full reproduction of the 500-3500 cm(-1) IR spectrum has been possible using the VPT2 approach and new insights are provided in the 6000 cm(-1) region where typical signatures have been characterized as a set of overtones and combination bands. Vibrational contributions to electronic transitions have been taken into account to simulate the optical (absorption and emission) properties of stilbene. Spectra simulated by employing the state-of-the-art Adiabatic Hessian model coupled to global hybrid functionals are in remarkable agreement with their experimental counterparts and the inclusion of Herzberg-Teller contributions further improves the results with respect to those delivered by the basic Franck-Condon model. PMID:27373560
Blažević, D.; Zelenika, S.
2015-05-01
Scavenging of low-level ambient vibrations i.e. the conversion of kinetic into electric energy, is proven as effective means of powering low consumption electronic devices such as wireless sensor nodes. Cantilever based scavengers are characterised by several advantages and thus thoroughly investigated; analytical models based on a distributed parameter approach, Euler-Bernoulli beam theory and eigenvalue analysis have thus been developed and experimentally verified. Finite element models (FEM) have also been proposed employing different modelling approaches and commercial software packages with coupled analysis capabilities. An approach of using a FEM analysis of a piezoelectric cantilever bimorph under harmonic excitation is used in this work. Modal, harmonic and linear and nonlinear transient analyses are performed. Different complex dynamic effects are observed and compared to the results obtained by using a distributed parameter model. The influence of two types of finite elements and three mesh densities is also investigated. A complex bimorph cantilever, based on commercially available Midé Technology® Volture energy scavengers, is then considered. These scavengers are characterised by an intricate multilayer structure not investigated so far in literature. An experimental set-up is developed to evaluate the behaviour of the considered class of devices. The results of the modal and the harmonic FEM analyses of the behaviour of the multilayer scavengers are verified experimentally for three different tip masses and 12 different electrical load values. A satisfying agreement between numerical and experimental results is achieved.
Plenio, M B; Huelga, S F
2013-01-01
We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in non linear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the non linear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of...
International Nuclear Information System (INIS)
A theoretical vibration model of a pressurized water reactor is established and studied which takes into account the fluid-structure interaction of the coupled three-dimensional system reactor pressure vessel-core barrel (reactor cavity). Vibration differential equations are derived only for the two-dimensional movement; the eigenfrequencies and amplitude ratios of the undamped system as well as a dimensionless damping factor of cavity vibrations are calculated with the data of the WWER-440, and discussed. (orig.)
DEFF Research Database (Denmark)
Zhang, Zili; Nielsen, Søren R. K.; Basu, Biswajit;
2015-01-01
Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g. This facilit...
International Nuclear Information System (INIS)
An electromechanically coupled model for a cantilevered piezoelectric energy harvester with a proof mass is presented. Proof masses are essential in microscale devices to move device resonances towards optimal frequency points for harvesting. Such devices with proof masses have not been rigorously modeled previously; instead, lumped mass or concentrated point masses at arbitrary points on the beam have been used. Thus, this work focuses on the exact vibration analysis of cantilevered energy harvester devices including a tip proof mass. The model is based not only on a detailed modal analysis, but also on a thorough investigation of damping ratios that can significantly affect device performance. A model with multiple degrees of freedom is developed and then reduced to a single-mode model, yielding convenient closed-form normalized predictions of device performance. In order to verify the analytical model, experimental tests are undertaken on a macroscale, symmetric, bimorph, piezoelectric energy harvester with proof masses of different geometries. The model accurately captures all aspects of the measured response, including the location of peak-power operating points at resonance and anti-resonance, and trends such as the dependence of the maximal power harvested on the frequency. It is observed that even a small change in proof mass geometry results in a substantial change of device performance due not only to the frequency shift, but also to the effect on the strain distribution along the device length. Future work will include the optimal design of devices for various applications, and quantification of the importance of nonlinearities (structural and piezoelectric coupling) for device performance
Directory of Open Access Journals (Sweden)
Jinhui Li
2015-01-01
Full Text Available This paper addresses the self-excited vibration problems of maglev vehicle-bridge interaction system which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the whole system. Firstly, two levitation models with different complexity are developed, and the comparison of the energy curves associated with the two models is carried out. We conclude that the interaction model with a single levitation control unit is sufficient for the study of the self-excited vibration. Then, the principle underlying the self-excited vibration is explored from the standpoint of work acting on the bridge done by the levitation system. Furthermore, the influences of the parameters, including the modal frequency and modal damping of bridge, the gain of the controller, the sprung mass, and the unsprung mass, on the stability of the interaction system are carried out. The study provides a theoretical guidance for solving the self-excited vibration problems of the vehicle-bridge interaction systems.
Simplified Prediction Model for Vortex-Induced Vibrations of Top Tensioned Risers
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
According to the characteristics of deepwater top tensioned risers, a simplified model is presented to predict the multi-modal response of vortex-induced vibration (VIV) in non-uniform flow based on energy equilibrium theory and the experimental data from VIV self-excited and forced oscillations of rigid cylinders. The response amplitude of each mode is determined by a balance between the energy fed into the riser over the lock-in regions and the energy dissipated by the fluid damping over the remainders. Compared with the previous prediction models, this method can take fully account of the intrinsic nature of VIV for low mass ratio structures on lock-in regions, added mass and nonlinear fluid damping effect, etc. Moreover, it is the first time to propose the accurate calculating procedure for VIV amplitude correction factor by solving energy equilibrium equation and a closed form solution is presented for the case of a riser of uniform mass and cross-section oscillating in a uniform flow. The predicted values show a reasonable agreement with VIV experiments of riser models in stepped and sheared currents.
Nonlocal-integro-differential modeling of vibration of elastically supported nanorods
Kiani, Keivan
2016-09-01
In the previously established nonlocal continuum-based models, small characteristic length was commonly incorporated into the mass matrix and the driving force vector which is a bit in contradiction with our sense regarding these factors. Herein, a nonlocal-integro-differential version of the constitutive relations is employed for the bulk and the surface layer of the nanorod. By adopting Hamilton's principle, integro-partial differential equations of motion of elastically supported nanorods are established accounting for both nonlocality and surface energy effects. Then, these are solved by an efficient meshless methodology. For fixed-fixed and fixed-free nanorods, modal analysis of the problem is also performed and the explicit expressions of the mass and stiffness matrices are derived. For these special cases, the obtained results by the meshless technique are successfully verified with those of the modal solution. In the newly developed numerical model, the small-scale parameter is only incorporated into the stiffness matrix which gives us a more realistic sense about the nonlocality effect. Subsequently, the roles of the surface energy, small-scale parameter, elastic supports, and kernel function on natural frequencies of the nanostructure are discussed and explained. This work can be considered as a pivotal step towards a more reasonable nonlocal modeling of vibration of nanoscale structures.
Almeida de Mendonça, João Paulo; Henrique de Lima, Alessandro; Amaral Junqueira, Georgia Maria; Gianini Quirino, Welber; Legnani, Cristiano; Oliveira Maciel, Indhira; Sato, Fernando
2016-05-01
We use the Coronene (C24H12), a simple and finite molecule, to make a model to study the spectroscopic and structural alterations generated by oxygenated groups in graphene oxide (GO). Based on the Lerf–Klinowski model, we chose the hydroxyl [OH‑], the carboxyl [COOH‑] and the epoxy [the ring C2O inside the molecule] as our radicals of interest and study their collective and isolated effects. We perform geometry optimization, vibrational IR (via AM1 and DFT-B3LYP) and Raman spectra (via DFT-B3LYP) of a series of functionalized coronene molecules. As results, we obtain some useful data for the analysis of IR and Raman spectra of GO, which facilitate the understanding and identification of the peaks found in the experiment. Finally, we suggest a new model to study GO, producing an accurate signature when compared to our experimental data. Such molecule shows in more details of the structural effects caused by functionalization when compared to experimental data.
Directory of Open Access Journals (Sweden)
Chang-Hua Zou
2009-01-01
Full Text Available Problem statement: Cardiovascular Diseases (CVD continued to be the leading cause of death. Failure or abnormal cardiac cellular or sub-cellular vibrations (oscillations could lead failure or abnormal heart beats that could cause CVD. Understanding the mechanisms of the vibrations (oscillations could help to prevent or to treat the diseases. Scientists have studied the mechanisms for more than 100 years. To our knowledge, the mechanisms are still unclear today. In this investigation, based on published data or results, conservation laws of the momentum as well as the energy, in views of biology, biochemistry, informatics and physics (BioChemInfoPhysics, we proposed our models of cardiac cellular and sub-cellular vibrations (oscillations of biological components, such as free ions in Biological Fluids (BF, Biological Membranes (BM, Ca++H+ (Ca++ and Na+K+ ATPases, Na+Ca++ exchangers (NCX, Ca++ carriers and myosin heads. Approach: Our models were described with 4-D (x, y, z, t or r, ?, z, t momentum transfer equations in mathematical physics. Results: The momentum transfer equations were solved with free and forced, damped, un-damped and over-damped, vibrations (oscillations. The biological components could be modeled as resonators or vibrators (oscillators, such as liquid plasmas, membranes, active springs, passive springs and active swings. Conclusion: We systematically provided new insights of automation (ignition and maintain, transportation, propagation and orientation of the cardiac cellular and sub-cellular vibrations (oscillations and resonances, with our BioChemInfoPhysics models of 4-D momentum transfer equations. Our modeling results implied: Auto-rhythmic cells (Sinoatrial Node Cells (SANC, Atrioventricular Node Cells (AVNC, Purkinje fibers, non-Auto-rhythmic ventricular myocytes and their Sarcoplasmic Reticulums (SR work as Biological Liquid Plasma Resonators (BLPR. The resonators were
Variational and coupled-cluster calculations of the spectra of anharmonic oscillators
International Nuclear Information System (INIS)
Using the general anharmonic oscillator as a case study, we examine the coupled-cluster method (CCM) in some detail. Emphasis is specially placed on the accuracy of the standard ground-state energy calculation and the excitation spectrum as derived via the Emrich ansatz. We are particularly interested in problems that can arise from large differences between the exact wave function and its model counterpart that forms the starting point of the CCM. To this end we begin with a variational Hartree approximation applied to three particular anharmonic-oscillator Hamiltonians that contain, respectively, pure quartic, equally weighted cubic and quartic, and double-well perturbations. These are chosen to provide increasingly stringent tests for the CCM in the above sense. Considerable attention is paid to the variational description of the double-well case, where the various possible solutions to the Hartree equations are considered and a further calculation on the energy-level splitting is performed. The CCM is then used to improve systematically upon our chosen starting point and is shown, particularly for the ground state, both to produce extremely accurate results and to be rather resilient to even gross deficiencies in the starting wave function. The main problem is the double-well system, where the CCM shows its lack of intrinsic inbuilt tunneling mechanisms via the absence of level splitting. Even here the CCM still produces very accurate average energies for very deep wells. While clearly needing some modification in such extreme cases, the CCM is shown to be quite adaptable and robust with regard to inaccurate starting wave functions
Energy Technology Data Exchange (ETDEWEB)
Tachikawa, Masanori [Quantum Chemistry Division, Graduate School of NanoBioScience, Yokohama City University, 22-2 Seto, Kanazawa, Yokohama 236-0027 (Japan)
2015-12-31
To theoretically demonstrate the binding of a positron to small polarized molecules, we have calculated the vibrational averaged positron affinity (PA) values along the local vibrational contribution with the configuration interaction level of multi-component molecular orbital method. This method can take the electron-positron correlation contribution into account through single electronic - single positronic excitation configurations. The PA values are enhanced by including the local vibrational contribution from vertical PA values due to the anharmonicity of the potential.
Effective field theory for nuclear vibrations with quantified uncertainties
Pérez, E A Coello
2015-01-01
We develop an effective field theory (EFT) for nuclear vibrations. The key ingredients - quadrupole degrees of freedom, rotational invariance, and a breakdown scale around the three-phonon level - are taken from data. The EFT is developed for spectra and electromagnetic moments and transitions. We employ tools from Bayesian statistics for the quantification of theoretical uncertainties. The EFT consistently describes spectra and electromagnetic transitions for $^{62}$Ni, $^{98,100}$Ru, $^{106,108}$Pd, $^{110,112,114}$Cd, and $^{118,120,122}$Te within the theoretical uncertainties. This suggests that these nuclei can be viewed as anharmonic vibrators.
Effective field theory for nuclear vibrations with quantified uncertainties
Coello Pérez, E. A.; Papenbrock, T.
2015-12-01
We develop an effective field theory (EFT) for nuclear vibrations. The key ingredients—quadrupole degrees of freedom, rotational invariance, and a breakdown scale around the three-phonon level—are taken from data. The EFT is developed for spectra and electromagnetic moments and transitions. We employ tools from Bayesian statistics for the quantification of theoretical uncertainties. The EFT consistently describes spectra and electromagnetic transitions for 62Ni,100,98Ru,108,106Pd, 110,112,114Cd, and 118,120,122Te within the theoretical uncertainties. This suggests that these nuclei can be viewed as anharmonic vibrators.
International Nuclear Information System (INIS)
The transition temperature, the depletion of the condensate atoms and the collective excitations of a Bose–Einstein condensation (BEC) with two- and three-body interactions in an anharmonic trap at finite temperature are studied in detail. By using the Popov version of the Hartree–Fock–Bogoliubov (HFB) approximation, an extended self-consistent model describing BEC with both two- and three-body interactions in a distorted harmonic potential at finite temperature is obtained and solved numerically. The results show that the transition temperature, the condensed atom number and the collective excitations are modified dramatically by the atomic three-body interactions and the distortion of the harmonic trap. (general)
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
This paper presents a numerical prediction of the unsteady flow field around oscillating airfoils at high angles of attack by solving unsteady Reynolds-averaged Navier-Stokes equations with SST turbulence model in order to simulate the effects of wind tunnel model vibrations on the aerodynamic properties of airfoils,especially high-aspect-ratio wings in a wind tunnel.The effects of the phase lagging between different modes of oscillations,i.e.,the airfoil plunging oscillation mode,the pitching oscillation mode,and the forward-backward oscillation mode,are also studied.It is shown that the vibrations (oscillations) of airfoils can cause the unsteady shedding of large-size separated vortex to precede the stationary stall incidence,hence lead to a stall onset at some earlier (lower) incidence than that in the steady sense.The different phase lagging has different effect on the flow field.When the pitching oscillation mode has small phase lagging behind the plunging oscillation mode,the effect of vibrations is large.Besides,if the amplitude of the oscillations is large enough,and the different modes of vibrations match or combine appropriately,the unsteady stall may occur 2° earlier in angle of attack than the case where airfoils keep stationary.
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. PMID:26087405
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.
Vibration energy harvesting by a Timoshenko beam model and piezoelectric transducer
Stoykov, S.; Litak, G.; Manoach, E.
2015-11-01
An electro-mechanical system of vibrational energy harvesting is studied. The beam is excited by external and kinematic periodic forces and damped by an electrical resistor through the coupled piezoelectric transducer. Nonlinearities are introduced by stoppers limiting the transverse displacements of the beam. The interaction between the beam and the stoppers is modeled as Winkler elastic foundation. The mechanical properties of the piezoelectric layer are taken into account and the beam is modeled as a composite structure. For the examined composite beam, the geometrically nonlinear version of the Timoshenko's beam theory is assumed. The equations of motion are derived by the principle of virtual work considering large deflections. An isogeometric approach is applied for space discretization and B-Splines are used as shape functions. Finally, the power output and the efficiency of the system due to harmonic excitations are discussed. The influence of the position of the stoppers and their length on the dynamics of the beam and consequently on the power output are analyzed and presented.
International Nuclear Information System (INIS)
This research thesis fits into the frame of researches achieved in the nuclear field in order to optimize the predictive abilities of sizing models of nuclear plant components. It more precisely addresses the modelling of the action exerted by the flowing fluid and the induced feedback by the structure dynamics. The objective is herein to investigate the interaction between the turbulence at the wall vicinity and the effects of non-conservative and potentially destabilizing unsteady coupling. The peculiar case of a single cylinder in infinite environment, and submitted to a transverse flow, is studied statically and then dynamically. The influence of flow regimes on dynamic response is characterized, and the quantification of fluid-structure interaction energy is assessed. The author then addresses the case of an array of cylinders, and highlights the contribution of three-dimensional macro-simulations for the analysis of flow-induced structure vibrations in subcritical regime within a High Performance Calculation (HPC) framework, and the interest of a CFD/CSM (computational fluid dynamics/computational structure mechanics) coupling in the case of turbulent flows in an industrial environment
Directory of Open Access Journals (Sweden)
Qingwen Li
2015-01-01
Full Text Available In the tunnel and underground space engineering, the blasting wave will attenuate from shock wave to stress wave to elastic seismic wave in the host rock. Also, the host rock will form crushed zone, fractured zone, and elastic seismic zone under the blasting loading and waves. In this paper, an accurate mathematical dynamic loading model was built. And the crushed zone as well as fractured zone was considered as the blasting vibration source thus deducting the partial energy for cutting host rock. So this complicated dynamic problem of segmented differential blasting was regarded as an equivalent elastic boundary problem by taking advantage of Saint-Venant’s Theorem. At last, a 3D model in finite element software FLAC3D accepted the constitutive parameters, uniformly distributed mutative loading, and the cylindrical attenuation law to predict the velocity curves and effective tensile curves for calculating safety criterion formulas of surrounding rock and tunnel liner after verifying well with the in situ monitoring data.
Directory of Open Access Journals (Sweden)
Pieter-Jan Vlok
2012-01-01
Full Text Available
ENGLISH ABSTRACT: Increased competitiveness in the production world necessitates improved maintenance strategies to increase availabilities and drive down cost . The maintenance engineer is thus faced with the need to make more intelligent pre ventive renewal decisions . Two of the main techniques to achieve this is through Condition Monitoring (such as vibrat ion monitoring and oil anal ysis and Statistical Failure Analysis (typically using probabilistic techniques . The present paper discusses these techniques, their uses and weaknesses and then presents th e Proportional Hazard Model as an solution to most of these weaknesses. It then goes on to compare the results of the different techniques in monetary terms, using a South African case study. This comparison shows clearly that the Proportional Hazards Model is sup erior to the present t echniques and should be the preferred model for many actual maintenance situations.
AFRIKAANSE OPSOMMING: Verhoogde vlakke van mededinging in die produksie omgewing noodsaak verbeterde instandhouding strategies om beskikbaarheid van toerusting te verhoog en koste te minimeer. Instandhoudingsingenieurs moet gevolglik meer intellegente voorkomende hernuwings besluite neem. Twee prominente tegnieke om hierdie doelwit te bereik is Toestandsmonitering (soos vibrasie monitering of olie analise en Statistiese Falingsanalise (gewoonlik m.b.v. probabilistiese metodes. In hierdie artikel beskou ons beide hierdie tegnieke, hulle gebruike en tekortkominge en stel dan die Proporsionele Gevaarkoers Model voor as 'n oplossing vir meeste van die tekortkominge. Die artikel vergelyk ook die verskillende tegnieke in geldelike terme deur gebruik te maak van 'n Suid-Afrikaanse gevalle studie. Hierdie vergelyking wys duidelik-uit dat die Proporsionele Gevaarkoers Model groter beloft e inhou as die huidige tegni eke en dat dit die voorkeur oplossing behoort te wees in baie werklike instandhoudings situasies.
1/N-expansion for the anharmonic oscillator
International Nuclear Information System (INIS)
The properties of the 1/N-expansion for the anharmonic oscillator in quantum mechanics have been investigated. The first seven terms of the expansion for the energy of ground and first excited levels are obtained analytically. The high-order behaviour of the 1/N-expansion coefficients in closed form was found, the asymptotic series obtained being Borel summable. The formulae derived was used to find the first seven coefficients of the perturbative expansion in powers of the coupling constant in the case of the double-well potential for arbitrary number of components N. These exact expressions enable us to guess the large-order behaviour of the perturbative coefficients for N=0, 1, ... 4. An example of summing the asymptotic series in powers of 1/N applying the Pade-Borel method is given
Critical rotation of an anharmonically trapped Bose-Einstein condensate
Institute of Scientific and Technical Information of China (English)
Ma Juan; Li Zhi; Xue Ju-Kui
2009-01-01
We consider rotational motion of an interacting atomic Bose-Einstein condensate (BEC) with both two- and threebody interactions in a quadratic-plus-quartic and harmonic-plus-Gaussian trap. By using the variational method, the influence of the three-body interaction and the anharmonicity of the trap on the lowest energy surface mode excitation and the spontaneous shape deformation (responsible for the vortex formation) in a rotating BEC is discussed in detail. It is found that the repulsive three-body interaction helps the formation of the vortex and reduces the lowest energy surface mode frequency and the critical rotational frequency of the system. Moreover, the critical rotational frequency for the vortex formation in the harmonic-plus-Gaussian potential is lower than that in the quadratic-plus-quartic potential.
Ran, Yibin; Pang, Min; Shen, Wei; Li, Ming; He, Rongxing
2016-10-01
We systematically studied the vibrational-resolved electronic spectra of group IV dichlorides using the Franck-Condon approximation combined with the Duschinsky and Herzberg-Teller effects in harmonic and anharmonic frameworks (only the simulation of absorption spectra includes the anharmonicity). Calculated results showed that the band shapes of simulated spectra are in accordance with those of the corresponding experimental or theoretical ones. We found that the symmetric bend mode in progression of absorption is the most active one, whereas the main contributor in photoelectron spectra is the symmetric stretching mode. Moreover, the Duschinsky and anharmonic effects exert weak influence on the absorption spectra, except for PbCl2 molecule. The theoretical insights presented in this work are significant in understanding the photophysical properties of MCl2 (M=C, Si, Ge, Sn, Pb) and studying the Herzberg-Teller and the anharmonic effects on the absorption spectra of new dichlorides of this main group. PMID:27280730
Liu, Shibing; Yang, Bingen
2015-08-01
Flexible multistage rotating systems that are supported or guided by long water-lubricated rubber bearings (WLRBs) have a variety of engineering applications. Vibration analysis of this type of machinery for performance and duality requires accurate modeling of WLRBs and related rotor-bearing assemblies. This work presents a new model of WLRBs, with attention given to the determination of bearing dynamic coefficients. Due to its large length-to-diameter ratio, a WLRB cannot be described by conventional pointwise bearing models with good fidelity. The bearing model proposed in this paper considers spatially distributed bearing forces. For the first time in the literature, the current study addresses the issue of mixed lubrication in the operation of WLRBs, which involves interactions of shaft vibration, elastic deformation of rubber material and fluid film pressure, and validates the WLRB model in experiments. Additionally, with the new bearing model, vibration analysis of WLRB-supported flexible multistage rotating systems is performed through use of a distributed transfer function method, which delivers accurate and closed-form analytical solutions of steady-state responses without discretization.
Directory of Open Access Journals (Sweden)
Jialong Jiao
2016-01-01
Full Text Available Ship hydroelastic vibration is an issue involving mutual interactions among inertial, hydrodynamic, and elastic forces. The conventional laboratory tests for wave-induced hydroelastic vibrations of ships are performed in tank conditions. An alternative approach to the conventional laboratory basin measurement, proposed in this paper, is to perform tests by large-scale model measurement in real sea waves. In order to perform this kind of novel experimental measurement, a large-scale free running model and the experiment scheme are proposed and introduced. The proposed testing methodology is quite general and applicable to a wide range of ship hydrodynamic experimental research. The testing procedure is presented by illustrating a 5-hour voyage trial of the large-scale model carried out at Huludao harbor of China in August 2015. Hammer tests were performed to identify the natural frequencies of the ship model at the beginning of the tests. Then a series of tests under different sailing conditions were carried out to investigate the vibrational characteristics of the model. As a postvoyage analysis, load, pressure, acceleration, and motion responses of the model are studied with respect to different time durations based on the measured data.
SIMULATION OF VIBRATION STRESS RELIEF AFTER WELDING BASED ON FEM
Institute of Scientific and Technical Information of China (English)
X.C.Zhao; Y.D.Zhang; H.W.Zhang; Q.Wu
2008-01-01
A finite element model is developed for the simulation of vibration stress relief (VSR) after welding.For the nonresonant vibration,the reduction in stress strongly depends on the amplitude of vibration.For the resonant vibration,the vibration frequency is the key for stress relief.The vibration frequency should be close to the structure natural frequency for the desired vibration mode.Only small vibration amplitude is required,which will be amplified during vibration.Vibration time does not have a major impact on vibration stress relief.When the amplitude of vibration stress relief is large,the treatment will be more effective.
Coriolis and anharmonicity couplings in the intramolecular vibrational energy flow: H+3 potential
International Nuclear Information System (INIS)
A classical study was conducted on the effects of Coriolis coupling on the internal energy flow between the two degenerate normal mode oscillations of H+3 . Strong correlations between the energy flow and the types of trajectories with the direction of the molecular rotation are revealed. The angle at which a trajectory, near its onset, approaches the isoenergetic contour on the potential surface is shown to determine the type of the trajectory and general characteristics of the system
Research on modeling of nonlinear vibration isolation system based on Bouc–Wen model
Directory of Open Access Journals (Sweden)
Zhi-ling Peng
2014-12-01
Full Text Available A feedforword neural network of multi-layer topologies for systems with hysteretic nonlinearity is constructed based on Bouc–Wen differential model. It not only reflects the hysteresis force characteristics of the Bouc–Wen model, but also determines its corresponding parameters. The simulation results show that restoring force–displacement curve hysteresis loop is very close to the real curve. The model trained can accurately predict the time response of system. The model is checked under the noise level. The result shows that the model has higher modeling precision, good generalization capability and a certain anti-interference ability.
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...
DEFF Research Database (Denmark)
Darula, Radoslav; Stein, George Juraj; Kallesøe, Carsten Skovmose;
2012-01-01
of the electromagnetic circuit in its various operational regimes. The parametric identification supplements mathematical derivations. The analyzed mechanical system is essentially a Single Degree-Of-Freedom (SDOF) oscillatory system augmented by magnetic force influence. The additional magnetic...... across the coil terminals. The electric circuit is closed with a shunt resistance connected to the electromagnet. The current induced in the circuit generates additional alternating magnetic force. This force counteracts the original vibration and damps it. In this way the coupled electro......-magneto-mechanical system suppresses the forced vibration. The mechanical energy is converted into electric one and dissipated in the shunt resistance external to the oscillatory system. Hence, the described system can be used as vibration controller to reduce excessive vibration of large machines and/or structures in semi...
Modeling peptide vibrations with dynamic change in structure. Local and extended contributions
Czech Academy of Sciences Publication Activity Database
Kiederling, T.; Kubelka, J.; Bouř, Petr; Wei, Y.; Vazquez, F.
Bochum : Ruhr-University Bochum, 2015. s. 46. [European Conference on the Spectroscopy of Biological Molecules /16./. 06.09.2015-10.09.2015, Bochum] Institutional support: RVO:61388963 Keywords : molecular dynamics * peptide vibrations Subject RIV: CF - Physical ; Theoretical Chemistry
Directory of Open Access Journals (Sweden)
Young-Ho Park
2006-01-01
Full Text Available In this paper, an energy flow model is developed to analyze transverse vibration including the effects of rotatory inertia as well as shear distortion, which are very important in the Timoshenko beam transversely vibrating in the medium-to-high frequency ranges. The energy governing equations for this energy flow model are newly derived by using classical displacement solutions of the flexural motion for the Timoshenko beam, in detail. The derived energy governing equations are in the general form incorporating not only the Euler-Bernoulli beam theory used for the conventional energy flow model but also the Rayleigh, shear, and Timoshenko beam theories. Finally, to verify the validity and accuracy of the derived model, numerical analyses for simple finite Timoshenko beams were performed. The results obtained by the derived energy flow model for simple finite Timoshenko beams are compared with those of the classical solutions for the Timoshenko beam, the energy flow solution, and the classical solution for the Euler-Bernoulli beam with various excitation frequencies and damping loss factors of the beam. In addition, the vibrational energy flow analyses of coupled Timoshenko beams are described in the other companion paper.
Modeling and Vibration Suppression for Telescopic Systems of Structural Members with Clearance
Arnold, Dieter; Mittwollen, Martin; Schönung, Frank; Wauer, Jörg; Barthels, Pierre
2006-01-01
Telescopic systems of structural members with clearance are found in many applications, e.g., mobile cranes, rack feeders, fork lifters, stacker cranes (see Figure 1). Operating these machines, undesirable vibrations may reduce the performance and increase safety problems. Therefore, this contribution has the aim to reduce these harmful vibrations. For a better understanding, the dynamic behaviour of these constructions is analysed. The main interest is the overlapping area of each two sectio...
Damping of collective vibrations in a memory-dependent transport model
International Nuclear Information System (INIS)
Damping of nuclear collective vibrations is studied on the basis of a Boltzmann-type transport equation with memory effects. It is shown that the memory effects play an essential role for a proper treatment of the damping properties of collective vibrations. A simple analytical formula is derived for the spreading widths at finite temperatures which provides a reasonable description for the gross properties of the damping of giant dipole and giant quadrupole resonances over a broad range of nuclei. (orig.)
Modeling the vibrational spectrum of 4,4'-diphenylmethane- bis(methyl)carbamate
Shundalau, M. B.; Pitsevich, G. A.; Ksenofontov, M. A.; Umreiko, D. S.
2010-07-01
We present results of ab initio calculations of the structure and vibrational IR spectrum for 4,4'-diphenylmethane-bis(methyl)carbamate (DPMC). Calculations were carried out in the HF/6-311G approximation with subsequent force-field scaling. The calculated characteristics of the vibrational spectrum of DPMC show satisfactory agreement with experimental values, which permits them to be used in spectral and structural analysis
Parameswaran, Arun P.; Ananthakrishnan, B.; Gangadharan, K. V.
2015-10-01
Real physical vibrating smart systems exhibit a lot of nonlinearities in their dynamics. Undesirable vibrations, particularly in the regions of first as well as second resonance, play a very important role in deteriorating the stability of the system as well as its operational efficiency. The work presented in the paper focuses on an analytical technique of mathematical modeling of a vibrating piezoelectric laminate cantilever beam which is considered to be the smart system. The natural frequencies of the vibrating smart system are determined from the ANSYS simulation studies and experimentally, it is found that the vibrations induced voltage is maximum at the first followed by the second natural frequencies. Hence, the smart system is modeled analytically through finite element technique using the Euler-Bernoulli beam theory for the first two flexural modes of vibrations. To account for the possible nonlinearities, a suitable robust controller is designed based on sliding mode technique. Simulation studies on the developed analytical model indicated a high performance of the designed controller in controlling the vibrations at first and second resonance regions. Also, the designed controller was found to be effective in its operations when the excitation varied over a large range covering the first two natural frequencies. In the final stage, the designed robust controller was successfully prototyped on a Field Programmable Gate Array (FPGA) platform using LabVIEW coupled with Compact Reconfigurable Input Output (cRIO-9022) controller configured in its FPGA interface mode and the resulting robust FPGA controller successfully controlled the occurring system vibrations.
Energy Technology Data Exchange (ETDEWEB)
Plenio, M. B.; Almeida, J.; Huelga, S. F. [Institute for Theoretical Physics, Albert-Einstein-Allee 11, University Ulm, D-89069 Ulm (Germany)
2013-12-21
We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in nonlinear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the nonlinear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of oscillatory behaviour using 2D photon echo techniques to corroborate the fundamental importance of the interplay of electronic and vibrational degrees of freedom in the dynamics of light harvesting aggregates.
Directory of Open Access Journals (Sweden)
Sergio Vincenzo Calcina
2014-01-01
Full Text Available This paper deals with the ambient vibration tests performed in an arch dam in two different working conditions in order to assess the effect produced by two different reservoir water levels on the structural vibration properties. The study consists of an experimental part and a numerical part. The experimental tests were carried out in two different periods of the year, at the beginning of autumn (October 2012 and at the end of winter (March 2013, respectively. The measurements were performed using a fast technique based on asynchronous records of microtremor time-series. In-contact single-station measurements were done by means of one single high resolution triaxial tromometer and two low-frequency seismometers, placed in different points of the structure. The Standard Spectral Ratio method has been used to evaluate the natural frequencies of vibration of the structure. A 3D finite element model of the arch dam-reservoir-foundation system has been developed to verify analytically determined vibration properties, such as natural frequencies and mode shapes, and their changes linked to water level with the experimental results.
Zhang, Xingwu; Gao, Robert X.; Yan, Ruqiang; Chen, Xuefeng; Sun, Chuang; Yang, Zhibo
2016-08-01
Crack is one of the crucial causes of structural failure. A methodology for quantitative crack identification is proposed in this paper based on multivariable wavelet finite element method and particle swarm optimization. First, the structure with crack is modeled by multivariable wavelet finite element method (MWFEM) so that the vibration parameters of the first three natural frequencies in arbitrary crack conditions can be obtained, which is named as the forward problem. Second, the structure with crack is tested to obtain the vibration parameters of first three natural frequencies by modal testing and advanced vibration signal processing method. Then, the analyzed and measured first three natural frequencies are combined together to obtain the location and size of the crack by using particle swarm optimization. Compared with traditional wavelet finite element method, MWFEM method can achieve more accurate vibration analysis results because it interpolates all the solving variables at one time, which makes the MWFEM-based method to improve the accuracy in quantitative crack identification. In the end, the validity and superiority of the proposed method are verified by experiments of both cantilever beam and simply supported beam.
Yairi, Motoki; Sakagami, Kimihiro; Nishibara, Kosuke; Okuzono, Takeshi
2016-07-01
Although sound radiation from sound-induced vibration and from force-excited vibration of solid structures are similar phenomena in terms of radiating from vibrating structures, the general relationship between them has not been explicitly studied to date. In particular, airborne sound transmission through walls and sound radiation from structurally vibrating surfaces in buildings are treated as different issues in architectural acoustics. In this paper, a fundamental relationship is elucidated through the use of a simple model. The transmission coefficient for random-incidence sound and the radiated sound power under point force excitation of an infinite elastic plate are both analyzed. Exact and approximate solutions are derived for the two problems, and the relationship between them is theoretically discussed. A conversion function that relates the transmission coefficient and radiated sound power is obtained in a simple closed form through the approximate solutions. The exact solutions are also related by the same conversion function. It is composed of the specific impedance and the wavenumber, and is independent of any elastic plate parameters. The sound radiation due to random-incidence sound and point force excitation are similar phenomena, and the only difference is the gradient of those characteristics with respect to the frequency. PMID:27475169
Suzuki, Y.
2016-05-01
This article demonstrates the practical applicability of a method of modelling shape memory alloys (SMAs) as actuators. For this study, a pair of SMA wires was installed in an antagonistic manner to form an actuator, and a linear differential equation that describes the behaviour of the actuator’s generated force relative to its input voltage was derived for the limited range below the austenite onset temperature. In this range, hysteresis need not be considered, and the proposed SMA actuator can therefore be practically applied in linear control systems, which is significant because large deformations accompanied by hysteresis do not necessarily occur in most vibration control cases. When specific values of the parameters used in the differential equation were identified experimentally, it became clear that one of the parameters was dependent on ambient airflow velocity. The values of this dependent parameter were obtained using an additional SMA wire as a sensor. In these experiments, while the airflow distribution around the SMA wires was varied by changing the rotational speed of the fans in the wind tunnels, an input voltage was conveyed to the SMA actuator circuit, and the generated force was measured. In this way, the parameter dependent on airflow velocity was estimated in real time, and it was validated that the calculated force was consistent with the measured one.
Modeling and new equipment definition for the vibration isolation box equipment system
Sani, Robert L.
1993-01-01
Our MSAD-funded research project is to provide numerical modeling support for the VIBES (Vibration Isolation Box Experiment System) which is an IML2 flight experiment being built by the Japanese research team of Dr. H. Azuma of the Japanese National Aerospace Laboratory. During this reporting period, the following have been accomplished: A semi-consistent mass finite element projection algorithm for 2D and 3D Boussinesq flows has been implemented on Sun, HP And Cray Platforms. The algorithm has better phase speed accuracy than similar finite difference or lumped mass finite element algorithms, an attribute which is essential for addressing realistic g-jitter effects as well as convectively-dominated transient systems. The projection algorithm has been benchmarked against solutions generated via the commercial code FIDAP. The algorithm appears to be accurate as well as computationally efficient. Optimization and potential parallelization studies are underway. Our implementation to date has focused on execution of the basic algorithm with at most a concern for vectorization. The initial time-varying gravity Boussinesq flow simulation is being set up. The mesh is being designed and the input file is being generated. Some preliminary 'small mesh' cases will be attempted on our HP9000/735 while our request to MSAD for supercomputing resources is being addressed. The Japanese research team for VIBES was visited, the current set up and status of the physical experiment was obtained and ongoing E-Mail communication link was established.
Forced vibration test of the Hualien large scale soil structure interaction model (pt. 2)
International Nuclear Information System (INIS)
A large-scale seismic test (LSST) programme conducted at Hualien (stiff soil site), Taiwan, has started (Tang et al., 1991) to provide earthquake-induced soil-structure interaction (SSI) data as an extension of the same kind of program conducted at Lotung (soft soil site) (EPRI, 1989). Two tests have been performed: a forced vibration test (FVT) without embedment (Morishita et al., 1993) and the same test with embedment. Horizontal excitations were applied in two different directions both on the roof slab and on the basemat of a 1/4-scale containment model. Vertical excitations were applied on the basemat only. The concept of 'principal axes (D1, D2)' was introduced for the SSI system, and the basic dynamic characteristics of the soil-structure system were obtained for D1 and D2. As an example, resonance frequencies for horizontal excitations were 4.1 and 4.6 Hz without embedment, and 6.1 and 6.3 Hz with embedment for D1 and D2 based on results transformed to principal axes. Finally, a soil impedance function was obtained by a newly defined error minimizing method. This function also simulates the classic embedment effect. (orig.)
Forced vibration test of the Hualien large scale soil structure interaction model (pt. 2)
Energy Technology Data Exchange (ETDEWEB)
Sugawara, Y.; Uetake, T. [Tokyo Electr. Power Co., Yokohama (Japan); Kobayashi, T.; Yamaya, H. [Kajima Technical Res. Inst., Tokyo (Japan)
1997-10-01
A large-scale seismic test (LSST) programme conducted at Hualien (stiff soil site), Taiwan, has started (Tang et al., 1991) to provide earthquake-induced soil-structure interaction (SSI) data as an extension of the same kind of program conducted at Lotung (soft soil site) (EPRI, 1989). Two tests have been performed: a forced vibration test (FVT) without embedment (Morishita et al., 1993) and the same test with embedment. Horizontal excitations were applied in two different directions both on the roof slab and on the basemat of a 1/4-scale containment model. Vertical excitations were applied on the basemat only. The concept of `principal axes (D{sub 1}, D{sub 2})` was introduced for the SSI system, and the basic dynamic characteristics of the soil-structure system were obtained for D{sub 1} and D{sub 2}. As an example, resonance frequencies for horizontal excitations were 4.1 and 4.6 Hz without embedment, and 6.1 and 6.3 Hz with embedment for D{sub 1} and D{sub 2} based on results transformed to principal axes. Finally, a soil impedance function was obtained by a newly defined error minimizing method. This function also simulates the classic embedment effect. (orig.) 4 refs.
Forced vibration test of the Hualien large scale soil-structure interaction (SSI) model: part 2
Energy Technology Data Exchange (ETDEWEB)
Sugawara, Y.; Uetake, T. [Tokyo Electric Power Co., Inc. (Japan); Kobayashi, T.; Yamaya, H. [Kajima Technical Research Inst., Tokyo (Japan)
1995-12-31
A Large-Scale Seismic Test (LSST) Program conducted at Hualien (stiff soil site). Taiwan, has started to obtain earthquake-induced soil-structure interaction (SSI) data as an extension of the same kind of program conducted at Lotung (soft soil site). Two tests have been performed: a Forced Vibration Test without embedment and the same test with embedment. Horizontal excitations were applied in two different directions both on the roof slab and on the basemat of a 1/4-scale containment model. Vertical excitations were applied on the basemat only. The concept of Principal Axes (D{sub 1}, D{sub 2}) was introduced for the SSI system, and the basic dynamic characteristics of the soil-structure system were obtained for D{sub 1} and D{sub 2}. As an example, peak frequencies for horizontal excitation were 4.1 and 4.6 Hz without embedment, and 6.1 and 6.3 Hz with embedment for D{sub 1} and D{sub 2} based on results transformed to principal axes. Finally, a soil impedance function was obtained by a newly defined error minimizing method. This function also simulates the classic embedment effect. (author). 5 refs., 9 figs., 1 tab.
Free vibrations of a taut cable with a general viscoelastic damper modeled by fractional derivatives
Sun, Limin; Chen, Lin
2015-01-01
This study extends dynamic understanding of a taut cable with a viscous damper at arbitrary location to that with a general linear viscoelastic (VE) damper portrayed by a five-parameter fractional derivative model (FDM). The FDM is able to describe a generalized relationship between force and deformation of viscoelastic dampers (material) in a wide frequency range, which can simulate a practical damper including its support condition or a secondary tie between neighboring cables. Free vibrations of the passively controlled cable system have then been formulated analytically through complex modal analysis. For the restricted case that the FDM is installed close to one cable anchorage, asymptotic solutions for the system complex frequency and modal damping are presented; explicit formulas have also been derived to determine the maximal attainable damping and corresponding optimum FDM parameters, based on which effects of frequency-dependent damper properties are appreciated. Considering the FDM located at arbitrary location, the three distinct regimes of frequency evolutions observed for a cable with a viscous damper have been generalized to that with a VE damper; also, new characteristics of the regime diagram and the frequency evolution in each regime are observed.
Modeling and simulation of vortex induced vibration on the subsea riser/pipeline (GRP pipe)
Raja Adli, Raja Nor Fauziah bt; Ibrahim, Idris
2012-06-01
This paper presents the research work conducted to investigate the dynamics characteristics of the offshore riser pipeline due to vortex flow and to develop a model that could predict its vortex induced responses. Glass-fiber reinforced plastic (GRP) pipe is used for this study which has smaller density from the steel. A two-dimensional finite element computational method is implemented to describe the dynamic behavior of the riser. The governing equation of motion was based on Hamilton's principle, consists of the strain energy due to bending and axial deformation, kinetic energy due to both riser and internal fluid movement and also external force from currents and waves. A direct integration method namely Newmark integration scheme is proposed to solve the equation of motion. A MATLAB program code was developed to obtain the simulation results. The natural frequency and damping ratio are presented for each mode. Dynamic response of riser is shown in time-domain and the numerical results are discussed. Several parameter effects are used to investigate dynamic responses and the results show an agreement with the theory. Vortex shedding phenomenon also has been discussed in this paper. As a conclusion, the simulation results have successfully shown the vortex induced vibration responses for GRP pipeline.
Study on Impeller Fracture Model Based on Vibration Characteristics and Fractal Theory
Directory of Open Access Journals (Sweden)
Xiaolong Zhang
2015-01-01
Full Text Available During the operation of centrifugal compressor, failure easily occurs in the presence of complicated external forces. The failure process characterizes with strong nonlinearity, and hence it is difficult to be described by conventional methods. In this paper, firstly, the cracks in different positions are described using crack fractal theory. The basic failure modes of the impeller are summarized. Secondly, a three-dimensional finite element model of the impeller is constructed. Then the von Mises stress under the centrifugal force is calculated, and the corresponding impeller failure process is simulated by “element life and death technology” in ANSYS. Finally, the impeller failure mechanism is analyzed. It can be found that the static stress is not the main cause of the impeller failure, and the dynamic characteristics of the impeller are not perfect because of the pitch vibration modes which appeared in the investigated frequency range. Meanwhile, the natural frequency of the impeller also cannot avoid the frequency of the excitation force.
Forced vibration test of the Hualien large scale soil-structure interaction (SSI) model: part 2
International Nuclear Information System (INIS)
A Large-Scale Seismic Test (LSST) Program conducted at Hualien (stiff soil site). Taiwan, has started to obtain earthquake-induced soil-structure interaction (SSI) data as an extension of the same kind of program conducted at Lotung (soft soil site). Two tests have been performed: a Forced Vibration Test without embedment and the same test with embedment. Horizontal excitations were applied in two different directions both on the roof slab and on the basemat of a 1/4-scale containment model. Vertical excitations were applied on the basemat only. The concept of Principal Axes (D1, D2) was introduced for the SSI system, and the basic dynamic characteristics of the soil-structure system were obtained for D1 and D2. As an example, peak frequencies for horizontal excitation were 4.1 and 4.6 Hz without embedment, and 6.1 and 6.3 Hz with embedment for D1 and D2 based on results transformed to principal axes. Finally, a soil impedance function was obtained by a newly defined error minimizing method. This function also simulates the classic embedment effect. (author). 5 refs., 9 figs., 1 tab
Study on forced vibration tests for large scale SSI model. Test results and their analysis
International Nuclear Information System (INIS)
A Large-Scale Seismic Test (LSST) Program has been conducted at Hualien, Taiwan, to obtain earthquake-induced soil-structure interaction (SSI) data in a stiff soil site environment. Forced vibration tests of the Hualien 1/4-scale containment SSI test model were conducted in October, 1992 before backfill (without embedment) and in February, 1993 after backfill (with embedment) for the purpose of defining basic dynamic characteristics of the soil-structure system. As results, peak frequencies were obtained as 4.1 and 4.3 Hz with twin peaks for both NS and EW horizontal excitation before backfill and as 6.1 and 6.3 Hz for NS and EW excitation respectively after backfill and orthogonal components were rather large. This results suggested existence of principal axes which were different from excitation directions. They were estimated 34 degree before backfill and 30 degree after backfill counterclockwise from NS direction, respectively. After transformed to the principal axes, each resonance curve had single peak and the orthogonal component became negligible. Based on this transformed results, the basic dynamic characteristics of the soil-structure system were obtained, namely, natural frequencies and damping factors. Soil impedances were also obtained by the method minimizing error function defined newly. (author)
Measurement Model and Precision Analysis of Accelerometers for Maglev Vibration Isolation Platforms
Directory of Open Access Journals (Sweden)
Qianqian Wu
2015-08-01
Full Text Available High precision measurement of acceleration levels is required to allow active control for vibration isolation platforms. It is necessary to propose an accelerometer configuration measurement model that yields such a high measuring precision. In this paper, an accelerometer configuration to improve measurement accuracy is proposed. The corresponding calculation formulas of the angular acceleration were derived through theoretical analysis. A method is presented to minimize angular acceleration noise based on analysis of the root mean square noise of the angular acceleration. Moreover, the influence of installation position errors and accelerometer orientation errors on the calculation precision of the angular acceleration is studied. Comparisons of the output differences between the proposed configuration and the previous planar triangle configuration under the same installation errors are conducted by simulation. The simulation results show that installation errors have a relatively small impact on the calculation accuracy of the proposed configuration. To further verify the high calculation precision of the proposed configuration, experiments are carried out for both the proposed configuration and the planar triangle configuration. On the basis of the results of simulations and experiments, it can be concluded that the proposed configuration has higher angular acceleration calculation precision and can be applied to different platforms.
A 3D finite element model for the vibration analysis of asymmetric rotating machines
International Nuclear Information System (INIS)
This paper suggests a 3D finite element method based on the modal theory in order to analyse linear periodically time-varying systems. Presentation of the method is given through the particular case of asymmetric rotating machines. First, Hill governing equations of asymmetric rotating oscillators with two degrees of freedom are investigated. These differential equations with periodic coefficients are solved with classic Floquet theory leading to parametric quasi-modes. These mathematical entities are found to have the same fundamental properties as classic Eigenmodes, but contain several harmonics possibly responsible for parametric instabilities. Extension to the vibration analysis (stability, frequency spectrum) of asymmetric rotating machines with multiple degrees of freedom is achieved with a fully 3D finite element model including stator and rotor coupling. Due to Hill expansion, the usual degrees of freedom are duplicated and associated with the relevant harmonic of the Floquet solutions in the frequency domain. Parametric quasi-modes as well as steady-state response of the whole system are ingeniously computed with a component-mode synthesis method. Finally, experimental investigations are performed on a test rig composed of an asymmetric rotor running on non-isotropic supports. Numerical and experimental results are compared to highlight the potential of the numerical method. (authors)
Fermi-Decay Law of Bose—Einstein Condensate Trapped in an Anharmonic Potential
International Nuclear Information System (INIS)
The Fermi-decay law of Bose—Einstein condensate, which is trapped by a cigar-shaped anharmonic trap and subjected to a weak random perturbation, is investigated by numerically calculating quantum fidelity (Loschmidt echo), to reveal the coherence loss of the condensate. We find that there are three indispensable factors, anharmonic trap, weak random perturbation and nonlinear interaction, in charging of the Fermi-decay law. The anharmonic trap creates anharmonic oscillations, and the weak random perturbation causes coherence loss by disturbing their coherent oscillations, while the nonlinear interaction enhances the loss to the Fermi-decay law. Based on the Fermi-decay law, some suggestions are presented to prolong the coherent time during coherently manipulating condensates. (general)
Myrtle, Timothy Fitzgerald
1998-12-01
This dissertation describes the development of an aeroelastic model of a helicopter rotor incorporating partial span trailing edge flaps on the blade and its application to the investigation of vibration reduction using active control. A new two-dimensional unsteady aerodynamic model for an airfoil/flap combination is described that includes compressibility and unsteady freestream effects. This new aerodynamic model is based on a rational function approximation (RFA) approach. In this approach, oscillatory response data obtained for a selected set of generalized airfoil and flap motions is used to generate an approximate aerodynamic transfer function which can be transformed to the time domain to form a state space aerodynamic model. In this dissertation, a method is described for adapting the conventional RFA approach to include unsteady freestream effects. Excellent agreement is demonstrated between the response of the new aerodynamic model and an exact incompressible solution to the unsteady freestream case. This model provides a complete description of the unsteady flap hinge moments due to airfoil and flap motion, allowing a complete and accurate characterization of control actuation requirements. The structural model utilizes an elastic blade model which includes fully coupled flap-lag-torsional dynamics and includes the effects of moderate deflections. The aeroelastic model is formulated in the time domain, with the coupled trim/response solution obtained using direct numerical integration in combination with autopilot type controller. A conventional higher harmonic control approach is used to investigate vibration reduction. Vibration control studies are performed which compare results using the new aerodynamic model and incompressible quasisteady Theodorsen aerodynamics. Significant differences were observed in the required deflections and control moments, indicating that compressibility and unsteady effects are necessary to properly characterize the
Vibrational analysis of phenol/(methanol)1
Gerhards, M.; Beckmann, K.; Kleinermanns, K.
1994-09-01
Ab initio calculations at the Hartree-Fock 4-31G* level were performed in order to calculate binding energies and vibrational frequencies of the phenol/CH3OH-cluster and two deuterated isotopomers ( d-phenol/CH3OD, d-phenol-CD3OD). The minimum energy structure is trans-linear, as for the phenol/H2O-cluster. The calculated frequencies of phenol and methanol as well as the intramolecular frequencies of the phenol/CH3OH-cluster are assigned to experimental values. The calculated intermolecular frequencies of the phenol/CH3OH-cluster are compared with the available experimental frequencies of the S 0 (and S 1)-state of the phenol/methanol-cluster and the similar p-cresol/methanol-cluster. Assignments are suggested for the σ and p 1-mode. In order to clarify the assignment of the low frequency vibration at 22 cm-1 anharmonic corrections for the β2-mode of the phenol/CH3OH-cluster are calculated. These calculations show only slight anharmonicity compared with the β2-mode calculations carried out for the phenol/H2O-cluster.
Avendaño-Valencia, L. D.; Fassois, S. D.
2015-07-01
The problem of damage detection in an operating wind turbine under normal operating conditions is addressed. This is characterized by difficulties associated with the lack of measurable excitation(s), the vibration response non-stationary nature, and its dependence on various types of uncertainties. To overcome these difficulties a stochastic approach based on Random Coefficient (RC) Linear Parameter Varying (LPV) AutoRegressive (AR) models is postulated. These models may effectively represent the non-stationary random vibration response under healthy conditions and subsequently used for damage detection through hypothesis testing. The performance of the method for damage and fault detection in an operating wind turbine is subsequently assessed via Monte Carlo simulations using the FAST simulation package.
International Nuclear Information System (INIS)
The optimized mean-trajectory (OMT) approximation is a semiclassical method for computing vibrational response functions from action-quantized classical trajectories connected by discrete transitions that represent radiation-matter interactions. Here, we extend the OMT to include additional vibrational coherence and energy transfer processes. This generalized approximation is applied to a pair of anharmonic chromophores coupled to a bath. The resulting 2D spectra are shown to reflect coherence transfer between normal modes
Svenne, J P; Amos, K; Fraser, P R; Karataglidis, S; Pisent, G; van der Knijff, D
2016-01-01
We employ a collective vibration coupled-channel model to describe the nucleon-16O cluster systems, obtaining low-excitation spectra for 17O and 17F. Bound and resonance states of the compound systems have been deduced, showing good agreement with experimental spectra. Low energy scattering cross sections of neutrons and protons from 16O also have been calculated and the results compare well with available experimental data.
Sahu, Nityananda; Khire, Subodh S.; Gadre, Shridhar R.
2015-10-01
Empirical model potentials are found to be very useful for generating most competitive minima of large water clusters, whereas correlated (e.g. second order-Møller-Plesset perturbation (MP2) theory or higher) calculations are necessary for predicting their accurate energetics and vibrational features. The present study reports the structures and energetics of (H2O)32 clusters at MP2 level using aug-cc-pvDZ basis set, starting with low-lying structures generated from model potentials. Such high-end and accurate calculations are made feasible by the cost-effective fragment-based molecular tailoring approach (MTA) in conjunction with the grafting procedure. The latter is found to yield electronic energies with a sub-millihartree accuracy with reference to their full calculation counterparts. The vibrational spectra of nine low-lying (H2O)32 isomers are obtained from the corresponding MTA-based Hessian matrix. All these low-lying isomers show almost similar spectral features, which are in fair agreement with the experiment. The experimental spectrum of (H2O)32 is thus better understood from the vibrational features of this set of very closely spaced isomers. The present case study of (H2O)32 clearly demonstrates the efficacy in obtaining accurate structures, energetics and spectra at correlated level of theory by combining model potential-based structures with fragmentation methods.
Energy Technology Data Exchange (ETDEWEB)
El Bouzidi, Salim [School of Engineering, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Hassan, Marwan, E-mail: mahassan@uoguelph.ca [School of Engineering, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Riznic, Jovica [Operational Engineering Assessment Division, Canadian Nuclear Safety Commission, Ottawa, Ontario K1P 5S9 (Canada)
2015-10-15
Highlights: • Comprehensive flow induced vibrations time domain model was developed. • Simulations of fluidelastic instability and turbulence were conducted. • Nonlinear effect due to the clearances at the supports was studied. • Prediction of stresses due to fluid excitation was obtained. • Deterministic and stochastic analyses for crack and leakage rate were conducted. - Abstract: Flow-induced vibrations (FIVs) are a major threat to the operation of nuclear steam generators. Turbulence and fluidelastic instability are the two main excitation mechanisms leading to tube vibrations. The consequences to the operation of steam generators are premature wear of the tubes, as well as development of cracks that may leak hazardous fluids. This paper investigates the effect of tube support clearance on the integrity of tube bundles within steam generators. Special emphasis will be placed on crack propagation and leakage rates. A crack growth model is used to simulate the growth of surface flaws and through-wall cracks of various initial sizes due to a wide range of support clearances. Leakage rates are predicted using a two-phase flow leakage model. Nonlinear finite element analysis is used to simulate a full U-bend subjected to fluidelastic and turbulence forces. Monte Carlo simulations are then used to conduct a probabilistic assessment of steam generator life due to crack development.
Indian Academy of Sciences (India)
Long Zhang; Guoliang Xiong; Hesheng Liu; Huijun Zou; Weizhong Guo
2010-04-01
A parametric time-frequency representation is presented based on timevarying autoregressive model (TVAR), followed by applications to non-stationary vibration signal processing. The identiﬁcation of time-varying model coefﬁcients and the determination of model order, are addressed by means of neural networks and genetic algorithms, respectively. Firstly, a simulated signal which mimic the rotor vibration during run-up stages was processed for a comparative study on TVAR and other non-parametric time-frequency representations such as Short Time Fourier Transform, Continuous Wavelet Transform, Empirical Mode Decomposition, Wigner–Ville Distribution and Choi–Williams Distribution, in terms of their resolutions, accuracy, cross term suppression as well as noise resistance. Secondly, TVAR was applied to analyse non-stationary vibration signals collected from a rotor test rig during run-up stages, with an aim to extract fault symptoms under non-stationary operating conditions. Simulation and experimental results demonstrate that TVAR is an effective solution to non-stationary signal analysis and has strong capability in signal time-frequency feature extraction.
International Nuclear Information System (INIS)
Highlights: • Comprehensive flow induced vibrations time domain model was developed. • Simulations of fluidelastic instability and turbulence were conducted. • Nonlinear effect due to the clearances at the supports was studied. • Prediction of stresses due to fluid excitation was obtained. • Deterministic and stochastic analyses for crack and leakage rate were conducted. - Abstract: Flow-induced vibrations (FIVs) are a major threat to the operation of nuclear steam generators. Turbulence and fluidelastic instability are the two main excitation mechanisms leading to tube vibrations. The consequences to the operation of steam generators are premature wear of the tubes, as well as development of cracks that may leak hazardous fluids. This paper investigates the effect of tube support clearance on the integrity of tube bundles within steam generators. Special emphasis will be placed on crack propagation and leakage rates. A crack growth model is used to simulate the growth of surface flaws and through-wall cracks of various initial sizes due to a wide range of support clearances. Leakage rates are predicted using a two-phase flow leakage model. Nonlinear finite element analysis is used to simulate a full U-bend subjected to fluidelastic and turbulence forces. Monte Carlo simulations are then used to conduct a probabilistic assessment of steam generator life due to crack development
Banerjee, Amit; Panigrahi, Brajesh; Pohit, G.
2016-04-01
In the present work, dynamic response of cracked Timoshenko beam with functionally graded material properties are obtained by a numerical technique using Ritz approximation. In order to verify the applicability and performance of the formulation, comparisons of the present numerical method with three-dimensional FEM models are made. Crack is assumed to be transverse and open throughout the vibration cycle. Two different crack detection techniques have been proposed. Results obtained by the numerical technique are used in both of the crack detection techniques. In the first technique, the frequency contours with respect to crack location and size are plotted and the intersection of contours of different modes helps in the prediction of crack location and size. In the second technique, crack is modelled using response surface methodology (RSM). The sum of the squared errors between the numerical and RSM regression model natural frequencies is used as the objective function. This objective function is minimised using genetic algorithm optimisation technique. Both the crack detection techniques and the numerical analysis have shown good agreement with each other.
The symmetry breaking phenomenon in anharmonic oscillator model
Mastine, Antonio Carlos; Natti, Erica Regina Takano
2010-01-01
In this article a non-perturbative time-dependent technique is used to treat the initial value problem, in Quantum Mechanics context, for a non-equilibrium self-interacting fermionic system in the presence of an external magnetic field. Particularly, in mean-field regime, we study the dynamical symmetry breaking phenomenon, identifying the physical processes associated.
International Nuclear Information System (INIS)
The research of nuclear reactions is necessary to identify the specific characteristics of nucleus and it is the most effective experimental method up to now. However, in order to explain the properties of nuclear structures, in addition to the study of the nuclear reactions, nuclear structure models to explain experimental dat and its theory must be used. There are many nuclear structure models to solve those properties of nucleus. This paper presents a collective model application to identify some of rotational bands and vibrational bands of 152 Sm and 152Gd nucleus which result from beta decay of 152Eu source the. (author)
Nuclear structure of 150Sm in the DPPQ model and IBM
International Nuclear Information System (INIS)
The decay pattern of the low lying levels in the shape transitional nucleus 150Sm is analyzed in terms of the quasi-vibrational and quasi-rotational collective model. The Dynamic Pairing plus quadrupole Model in the microscopic theory of the collective model is employed to predict extensive structure characteristics. The potential energy surface (PES), the spectroscopic factors and the E2, E0 transition rates from the DPPQ model are illustrated. Comparison is made with the predictions in the Interacting Boson Model (IBM-1). A correspondence is demonstrated of the effect of the control parameter in the two models on the calculated nuclear structure. The study of the wave functions of the two spin I = 2 excited states in IBM is carried out. The alternative view of an anharmonic vibrator and a soft rotor is discussed in terms of the E2 transition rates and other structural characteristics. (author)
Vibrational states as a representations of a SU(6) group
International Nuclear Information System (INIS)
Full text : In any event it is proved that a description of collective states in terms of a SU(6) model might be appropriate, especially in the two limiting situations in which the approximate symmetries O+(5) and SU(3) occur. For nuclei whose spectrum is not too far from these exact symmetries it might be useful to use the respective unperturbed wave functions and energies. The symmetry structure of the nuclear many body system is in general very complex. However, since only few degrees of freedom play a dominant role in the description of the collective states, it is hoped that the Hamiltonian of the system when written in terms of these degrees of freedom has simple symmetry properties. It is important to notice that our collective Hamiltonian yields a finite energy matrix for a given value of N and a definite spin. This is a consequence of the symmetry properties of our collective operators. Because the boson-boson interaction in Hamiltonian splits the degeneracy of the multiplets, this limit describes an anharmonic vibrator. It is worth nothing that the knowledge of the invariance properties of the Hamiltonian provides directly a solution to the eigenvalue problem.
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.
International Nuclear Information System (INIS)
A 1/9-scale model flow-induced vibration test of a proposed advanced water reactor (AWR) was performed. The main objectives of the test program were: (1) to derive an empirical equation for the turbulence-induced forcing function that can be applied to the full-sized prototype; (2) to study the effect of viscosity on the turbulence forcing function generation and dissipation and to verify the superposition assumption widely used in dynamic analysis of weakly coupled fluid-shell systems; (3) to measure the shell response due to turbulence-induced excitation so that the data can be used to verify methods and computer programs used in the flow-induced vibration design analysis of the prototype. This paper describes Objective (3) of the test program
Accurate calculation of vibrational frequencies using explicitly correlated coupled-cluster theory.
Rauhut, Guntram; Knizia, Gerald; Werner, Hans-Joachim
2009-02-01
The recently proposed explicitly correlated CCSD(T)-F12x (x = a,b) approximations [T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106 (2007)] are applied to compute equilibrium structures and harmonic as well as anharmonic vibrational frequencies for H(2)O, HCN, CO(2), CH(2)O, H(2)O(2), C(2)H(2), CH(2)NH, C(2)H(2)O, and the trans-isomer of 1,2-C(2)H(2)F(2). Using aug-cc-pVTZ basis sets, the CCSD(T)-F12a equilibrium geometries and harmonic vibrational frequencies are in very close agreement with CCSD(T)/aug-cc-pV5Z values. The anharmonic frequencies are evaluated using vibrational self-consistent field and vibrational configuration interaction methods based on automatically generated potential energy surfaces. The mean absolute deviation of the CCSD(T)-F12a/aug-cc-pVTZ anharmonic frequencies from experimental values amounts to only 4.0 cm(-1). PMID:19206956
Vibration analysis of a trimorph plate as a precursor model for smart automotive bodywork
International Nuclear Information System (INIS)
This study investigates the vibration characteristics of a proposed candidate structure for smarter car bodies. The material is conceived as a three-layer laminated structure in the form of a trimorph plate. The vibration response of the plate is investigated for large deflections by considering the effects of geometric nonlinearity. First, the governing equation for the mid-point deflection of the plate is developed based on classical laminate plate theory (CLPT). The governing equation is solved, and a simulation is run for different possible layer-stacking sequences. Comparisons are made between the nonlinear vibration response of this trimorph plate both with and without the effects of the von Kármán geometric nonlinearity. The results show that for the same material properties the different layer-stacking sequences produce different vibration responses, and from there it is concluded that layer-stacking sequencing is a basis for the definition of a suitable material configuration for high performance automotive applications.
Economic benefits of CAD-models for compressor manifold vibration analyses according to API 618
Eijk, A.; Samland, G.; Retz, N.; Sauter, D.
2003-01-01
Reciprocating compressors, including pulsation dampers and the connected pipe system, are often the heart of an installation and should therefore operate reliable. Compressor manifold vibrations can contribute to fatigue failure of the system which can lead to unsafe situations, loss of capacity and
Accounting for environment and dynamics in modeling of vibrational spectra in condensed phase
Czech Academy of Sciences Publication Activity Database
Andrushchenko, Valery; Bouř, Petr
Antalya: -, 2015. s. 46. [TURCMOS 2015. International Turkish Congress on Molecular Spectroscopy /2./. 13.09.2015-18.09.2015, Antalya] R&D Projects: GA ČR(CZ) GA14-03564S Institutional support: RVO:61388963 Keywords : vibrational spectra simulations * molecular dynamics * DFT * MD/DFT Subject RIV: CF - Physical ; Theoretical Chemistry
Vibration analysis of a trimorph plate as a precursor model for smart automotive bodywork
Big-Alabo, A.; Cartmell, M. P.
2012-08-01
This study investigates the vibration characteristics of a proposed candidate structure for smarter car bodies. The material is conceived as a three-layer laminated structure in the form of a trimorph plate. The vibration response of the plate is investigated for large deflections by considering the effects of geometric nonlinearity. First, the governing equation for the mid-point deflection of the plate is developed based on classical laminate plate theory (CLPT). The governing equation is solved, and a simulation is run for different possible layer-stacking sequences. Comparisons are made between the nonlinear vibration response of this trimorph plate both with and without the effects of the von Kármán geometric nonlinearity. The results show that for the same material properties the different layer-stacking sequences produce different vibration responses, and from there it is concluded that layer-stacking sequencing is a basis for the definition of a suitable material configuration for high performance automotive applications.
Zhu, Yu; Li, Qiang; Xu, Dengfeng; Hu, Chuxiong; Zhang, Ming
2012-09-01
This paper presents a negative stiffness magnetic suspension vibration isolator (NSMSVI) using magnetic spring and rubber ligaments. The positive stiffness is obtained by repulsive magnetic spring while the negative stiffness is gained by rubber ligaments. In order to study the vibration isolation performance of the NSMSVI, an analytical expression of the vertical stretch force of the rubber ligament is constructed. Experiments are carried out, which demonstrates that the analytical expression is effective. Then an analytical expression of the vertical stiffness of the rubber ligament is deduced by the derivative of the stretch force of the rubber ligament with respect to the displacement of the inner magnetic ring. Furthermore, the parametric study of the magnetic spring and rubber ligament are carried out. As a case study, the size dimensions of the magnetic spring and rubber ligament are determined. Finally, an NSMSVI table was built to verify the vibration isolation performance of the NSMSVI. The transmissibility curves of the NSMSVI are subsequently calculated and tested by instruments. The experimental results reveal that there is a good consistency between the measured transmissibility and the calculated ones, which proves that the proposed NSMSVI is effective and can realize low-frequency vibration isolation.
Goychuk, Igor
2014-01-01
Here we generalize our previous model of molecular motors trafficking subdiffusing cargos in viscoelastic cytosol by (i) including mechanochemical coupling between cyclic conformational fluctuations of the motor protein driven by the reaction of ATP hydrolysis and its translational motion within the simplest two-state model of hand-over-hand motion of kinesin, and also (ii) by taking into account the anharmonicity of the tether between the motor and cargo (its maximally possible extension length). It is shown that the major earlier results such as occurrence of normal versus anomalous transport depending on the amplitude of binding potential, cargo size and the motor turnover frequency not only survive in this more realistic model, but the results also look very similar for the correspondingly adjusted parameters. However, this more realistic model displays a substantially larger thermodynamic efficiency due to a bidirectional mechanochemical coupling. For realistic parameters, the maximal thermodynamic effic...
Directory of Open Access Journals (Sweden)
G.M. Golenkov
2015-12-01
Full Text Available Purpose. The research of the influence of value and direction of current on the equivalent spring magnetic force based on coaxial-linear motor (CLM – MS. Methodology. We carried out investigation of the equivalent harshness of magnetic spring with determination of electromechanical propulsion performance characteristics by the methods of computer modeling and experimental research of physical model of CLM – MS. The modeling of magnetic spring of CLM – MS is carried out by the finite-element method. The challenge is met as an axisymmetric challenge in cylindrical co-ordinates in magnetostatic approach. The experimental investigattion of the propulsion performance characteristics of magnetic spring is carried out on the test bench. Results. After the computer modeling and the experimental investigation of the electromechanical propulsion performance characteristics of magnetic spring the expressions of equivalent stiffness coefficient depending on the current in winding are obtained. The results of computer modeling are confirmed experimentally. Originality. The determination of equivalent stiffness coefficient of magnetic spring of vibration exciter based on coaxial-linear motor. Practical value. The obtained determination of equivalent stiffness coefficient of magnetic spring may be used in process of designing of vibration machines with devices for change of natural oscillation frequency.
Plattenburg, Joseph; Dreyer, Jason T.; Singh, Rajendra
2016-06-01
This paper proposes a new analytical model for a thin cylindrical shell that utilizes a homogeneous cardboard liner to increase modal damping. Such cardboard liners are frequently used as noise and vibration control devices for cylindrical shell-like structures in automotive drive shafts. However, most prior studies on such lined structures have only investigated the associated damping mechanisms in an empirical manner. Only finite element models and experimental methods have been previously used for characterization, whereas no analytical studies have addressed sliding friction interaction at the shell-liner interface. The proposed theory, as an extension of a prior experimental study, uses the Rayleigh-Ritz method and incorporates material structural damping along with frequency-dependent viscous and Coulomb interfacial damping formulations for the shell-liner interaction. Experimental validation of the proposed model, using a thin cylindrical shell with three different cardboard liner thicknesses, is provided to validate the new model, and to characterize the damping parameters. Finally, the model is used to investigate the effect of the liner and the damping parameters on the modal attenuation of the shell vibration, in particular for the higher-order coupled shell modes.
Selective excitation of branched vibrational ladder in uranium hexafluoride laser isotope separation
International Nuclear Information System (INIS)
Theoretical investigation was made on the dynamics of initial excitation process in molecular laser isotope separation for uranium hexafluoride (UF6) based on the generalized N-level density-matrix equation derived by Goodman et al. Branched vibrational model due to anharmonic-splitting components for the ν3 mode of UF6 molecule were formalized and phase interferences of density-matrix elements were considered to analyze the selective excitation. Because of a power-broadening effect, no more than 0.05J/cm2 fluence of a laser pulse completely masks high enrichment peaks in broadband (Δν = 2GHz) pumping case. Even when matching the laser frequency with ν3 band (n = 0 → 1) of 238UF6, the enrichment factor (α ≡ Rproduct/Rfeed, R ≡ [235UF6]/[238UF6]; R is the abundance ratio and [ ] means the mole fraction.) does not decrease. A narrow spectral linewidth (Δν = 400MHz) is shown to be essential to achieve a high concentration ratio in the system with a branched N-level ladder as expected from a general two-level system. The exciting frequency, which does not necessarily accord with the ν3 band of 235UF6, gives the maximum enrichment peak. Both the detuning of the optimum frequency and the sharp enrichment peak suggest a direct excitation due to multiphoton resonance. Spectral stability of the laser pulse is also required to excite only the desired isotope for the system with complicated anharmonic-splittings. (author)
DEFF Research Database (Denmark)
Santos, Ilmar; Saracho, C.M.; Smith, J.T.;
2004-01-01
illustrate linear, non-linear and time-depending terms in a very transparent way. Although neither gyroscopic effect due to rotor angular vibrations nor higher blade mode shapes are considered in the analysis, the equations of motion of the rotor-blades system are still general enough for the purpose of the......This work gives a theoretical and experimental contribution to the problem of rotor-blades dynamic interaction. A validation procedure of mathematical models is carried out with help of a simple test rig, built by a mass-spring system attached to four flexible rotating blades. With this test rig...... the test rig by attaching the rigid rotor to a flexible foundation. The blades are modeled as Euler-Bernoulli beams. Using three different approaches to describe the beam deformation one achieves: (a) a linear model; (b) a linear beam model with second order terms; (c) a fully non-linear model. Tip...
DEFF Research Database (Denmark)
Araujo, A.; Soares, C.; Herskovits, J.;
2002-01-01
structural behaviour and implement efficient control algorithms for active noise and vibration control. To address this issue we propose a discrete finite element model, associated to gradient optimisation and to an inverse method using experimental vibration data to carry out the identification of...... electromechanical properties in composite plate specimens with surface bonded piezoelectric patches or layers. The properties to be determined are the elastic and piezoelectric constants of the structure's constituent materials. (C) 2002 Elsevier Science Ltd. All rights reserved....
International Nuclear Information System (INIS)
The nearly dispersionless, so-called 'optical' vibrational modes observed by inelastic neutron scattering from icosahedral Al-Pd-Mn and Zn-Mg-Y quasicrystals are found to correspond well to modes of a continuum elastic sphere that has the same diameter as the corresponding icosahedral basic units of the quasicrystal. When the sphere is considered as free, most of the experimentally found modes can be accounted for, in both systems. Taking into account the mechanical connection between the clusters and the remainder of the quasicrystal allows a complete assignment of all optical modes in the case of Al-Pd-Mn. This approach provides support to the relevance of clusters in the vibrational properties of quasicrystals
DEFF Research Database (Denmark)
Sørensen, Herman
1997-01-01
Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board......Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board...