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Sample records for c-o vibrational frequencies

  1. Theoretical study of the electrostatic and steric effects on the spectroscopic characteristics of the metal-ligand unit of heme proteins. 2. C-O vibrational frequencies, 17O isotropic chemical shifts, and nuclear quadrupole coupling constants.

    PubMed

    Kushkuley, B; Stavrov, S S

    1997-02-01

    The quantum chemical calculations, vibronic theory of activation, and London-Pople approach are used to study the dependence of the C-O vibrational frequency, 17O isotropic chemical shift, and nuclear quadrupole coupling constant on the distortion of the porphyrin ring and geometry of the CO coordination, changes in the iron-carbon and iron-imidazole distances, magnitude of the iron displacement out of the porphyrin plane, and presence of the charged groups in the heme environment. It is shown that only the electrostatic interactions can cause the variation of all these parameters experimentally observed in different heme proteins, and the heme distortions could modulate this variation. The correlations between the theoretically calculated parameters are shown to be close to the experimentally observed ones. The study of the effect of the electric field of the distal histidine shows that the presence of the four C-O vibrational bands in the infrared absorption spectra of the carbon monoxide complexes of different myoglobins and hemoglobins can be caused by the different orientations of the different tautomeric forms of the distal histidine. The dependence of the 17O isotropic chemical shift and nuclear quadrupole coupling constant on pH and the distal histidine substitution can be also explained from the same point of view.

  2. Theoretical Study of the Electrostatic and Steric Effects on the Spectroscopic Characteristics of the Metal-Ligand Unit of Heme Proteins. 2. C-O Vibrational Frequencies, 17O Isotropic Chemical Shifts, and Nuclear Quadrupole Coupling Constants

    PubMed Central

    Kushkuley, Boris; Stavrov, Solomon S.

    1997-01-01

    The quantum chemical calculations, vibronic theory of activation, and London-Pople approach are used to study the dependence of the C-O vibrational frequency, 17O isotropic chemical shift, and nuclear quadrupole coupling constant on the distortion of the porphyrin ring and geometry of the CO coordination, changes in the iron-carbon and iron-imidazole distances, magnitude of the iron displacement out of the porphyrin plane, and presence of the charged groups in the heme environment. It is shown that only the electrostatic interactions can cause the variation of all these parameters experimentally observed in different heme proteins, and the heme distortions could modulate this variation. The correlations between the theoretically calculated parameters are shown to be close to the experimentally observed ones. The study of the effect of the electric field of the distal histidine shows that the presence of the four C-O vibrational bands in the infrared absorption spectra of the carbon monoxide complexes of different myoglobins and hemoglobins can be caused by the different orientations of the different tautomeric forms of the distal histidine. The dependence of the 17O isotropic chemical shift and nuclear quadrupole coupling constant on pH and the distal histidine substitution can be also explained from the same point of view. PMID:9017215

  3. Distal and proximal ligand interactions in heme proteins: Correlations between C-O and Fe-C vibrational frequencies, oxygen-17 and carbon-13 nuclear magnetic resonance chemical shifts, and oxygen-17 nuclear quadrupole coupling constants in C sup 17 O- and sup 13 CO-labeled species

    SciTech Connect

    Ki Deok Park; Guo, K.; Adebodun, F.; Chiu, M.L.; Sligar, S.G.; Oldfield, E. )

    1991-03-05

    The authors have obtained the oxygen-17 nuclear magnetic resonance (NMR) spectra of a variety of C{sup 17}O-labeled heme proteins, including sperm whale (Physeter catodon) myoglobin, two synthetic sperm whale myoglobin mutants (His E7 {yields} Val E7; His E7 {yields} Phe E7), adult human hemoglobin, rabbit (Oryctolagus cuniculus) hemoglobin, horseradish (Cochlearia armoracia) peroxidase isoenzymes A and C, and Caldariomyces fumago chloroperoxidase, in some cases as a function of pH, and have determined their isotropic {sup 17}O NMR chemical shifts, {delta}{sub i}, and spin-lattice relaxation times, T{sub 1}. They have also obtained similar results on a picket fence prophyrin. The results show an excellent correlation between the infrared C-O vibrational frequencies, {nu}(C-O), and {delta}{sub i}, between {nu}(C-O) and the {sup 17}O nuclear quadrupole coupling constant, and as expected between e{sup 2}qQ/h and {delta}{sub i}. The results suggest the IR and NMR measurements reflect the same interaction, which is thought to be primarily the degree of {pi}-back-bonding from Fe d to CO {pi}* orbitals, as outlined previously.

  4. Charge Oscillation in C-O Stretching Vibrations: a Comparison of CO_2^- Anion and Carboxylate Functional Groups

    NASA Astrophysics Data System (ADS)

    Thompson, Michael C.; Weber, J. Mathias

    2017-06-01

    We compare the intensity ratio of symmetric to antisymmetric C-O stretching vibrational transitions in CO_2^- and MCOO^- (M = H, Ag and Bi) using photodissociation spectroscopy. This ratio depends strongly on the bonding partner M, caused by a dynamic change in the molecular charge distribution during vibrational motion. Density functional theory calculations indicate that such charge oscillations can occur for both the symmetric and antisymmetric C-O stretching vibrations in these systems. In the symmetric C-O stretching modes, however, they are at play only if a bonding partner is present, which acts as a reservoir for charge during CO bond compression in the symmetric stretching vibration.

  5. Modulational instabilities in acetanilide taking into account both the N H and the C=O vibrational self-trappings

    NASA Astrophysics Data System (ADS)

    Simo, Elie

    2007-02-01

    A model of crystalline acetanilide, ACN accounting for the C=O and N-H vibrational self-trappings is presented. We develop a fully discrete version of ACN. We show that ACN can be described by a set of two coupled discrete nonlinear Schrödinger (DNLS) equations. Modulational instabilities (MI) are studied both theoretically and numerically. Dispersion laws for the wavenumbers and frequencies of the linear modulation waves are determined. We also derived the criterion for the existence of MI. Numerical simulations are carried out for a variety of selected wave amplitudes in the unstable zone. It is shown that instabilities grow as the wavenumbers and amplitudes of the modulated waves increase. MI grow faster in the N-H mode than in the C=O mode. Temporal evolution of the density probabilities of the vibrational excitons are obtained by the numerical integration of the coupled DNLS equations governing the ACN molecule. These investigations confirm the generation of localized modes by the phenomenon of MI and the predominance of the N-H vibrational mode in the MI process of the ACN.

  6. The vibrational frequencies of difluoroethyne

    NASA Technical Reports Server (NTRS)

    Breidung, Juergen; Schneider, Winfried; Thiel, Walter; Lee, Timothy J.

    1992-01-01

    Ab initio coupled-cluster calculations with single and double excitations and with a perturbational treatment of connected triple excitations are reported for difluoroethyne using large basis sets. The results for the transbending mode nu-4 are extremely sensitive to electron correlation and basis set effects. The best theoretical and experimental estimates for the fundamental vibrational frequencies are in excellent agreement.

  7. Distal and proximal ligand interactions in heme proteins: correlations between C-O and Fe-C vibrational frequencies, oxygen-17 and carbon-13 nuclear magnetic resonance chemical shifts, and oxygen-17 nuclear quadrupole coupling constants in C17O- and 13CO-labeled species.

    PubMed

    Park, K D; Guo, K M; Adebodun, F; Chiu, M L; Sligar, S G; Oldfield, E

    1991-03-05

    We have obtained the oxygen-17 nuclear magnetic resonance (NMR) spectra of a variety of C17O-labeled heme proteins, including sperm whale (Physeter catodon) myoglobin, two synthetic sperm whale myoglobin mutants (His E7----Val E7; His E7----Phe E7), adult human hemoglobin, rabbit (Oryctolagus cuniculus) hemoglobin, horseradish (Cochlearia armoracia) peroxidase (E.C. 1.11.1.7) isoenzymes A and C, and Caldariomyces fumago chloroperoxidase (E.C. 1.11.1.10), in some cases as a function of pH, and have determined their isotropic 17O NMR chemical shifts, delta i, and spin-lattice relaxation times, T1. We have also obtained similar results on a picket fence prophyrin, [5,10,15,20-tetrakis(alpha, alpha, alpha, alpha, alpha-pivalamidophenyl)porphyrinato]iron(II) (1-MeIm)CO, both in solution and in the solid state. Our results show an excellent correlation between the infrared C-O vibrational frequencies, v(C-O), and delta i, between v(C-O) and the 17O nuclear quadrupole coupling constant (e2qQ/h, derived from T1), and as expected between e2qQ/h and delta i. Taken together with the work of others on the 13C NMR of 13CO-labeled proteins, where we find an excellent correlation between delta i(13C) and v(Fe-C), our results suggest that IR and NMR measurements reflect the same interaction, which is thought to be primarily the degree of pi-back-bonding from Fe d to CO pi* orbitals, as outlined previously [Li, X.-Y., & Spiro, T.G. (1988) J. Am. Chem. Soc. 110, 6024]. The modulation of this interaction by the local charge field of the distal heme residue (histidine, glutamine, arginine, and possibly lysine) in a variety of species and mutants, as reflected in the NMR and IR measurements, is discussed, as is the effect of cysteine as the proximal heme ligand.

  8. Frequency adjustable MEMS vibration energy harvester

    NASA Astrophysics Data System (ADS)

    Podder, P.; Constantinou, P.; Amann, A.; Roy, S.

    2016-10-01

    Ambient mechanical vibrations offer an attractive solution for powering the wireless sensor nodes of the emerging “Internet-of-Things”. However, the wide-ranging variability of the ambient vibration frequencies pose a significant challenge to the efficient transduction of vibration into usable electrical energy. This work reports the development of a MEMS electromagnetic vibration energy harvester where the resonance frequency of the oscillator can be adjusted or tuned to adapt to the ambient vibrational frequency. Micro-fabricated silicon spring and double layer planar micro-coils along with sintered NdFeB micro-magnets are used to construct the electromagnetic transduction mechanism. Furthermore, another NdFeB magnet is adjustably assembled to induce variable magnetic interaction with the transducing magnet, leading to significant change in the spring stiffness and resonance frequency. Finite element analysis and numerical simulations exhibit substantial frequency tuning range (25% of natural resonance frequency) by appropriate adjustment of the repulsive magnetic interaction between the tuning and transducing magnet pair. This demonstrated method of frequency adjustment or tuning have potential applications in other MEMS vibration energy harvesters and micromechanical oscillators.

  9. Low-frequency vibrational modes of glutamine

    NASA Astrophysics Data System (ADS)

    Wang, Wei-Ning; Wang, Guo; Zhang, Yan

    2011-12-01

    High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy. Based on the experimental and the computational results, the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations. Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.

  10. Wireless vibration sensor using frequency modulation technique

    NASA Astrophysics Data System (ADS)

    Kim, Minhyuck; Yoon, Hwan-Sik; Kim, Sehun; Kim, Joo-Hyung

    2012-04-01

    In recent years, wireless strain sensors have received attention as an efficient method to measure response of a structure in a remote location. Wireless sensors developed for remote measurement include RF wireless sensor modules and microstrip antenna-based sensors. In this paper, a simple wireless vibration sensor based on a piezoelectric sensor and the Frequency Modulation (FM) technique is developed for remote measurement of vibrating structures. The piezoelectric sensor can generate a voltage signal proportional to dynamic strain of the host structure. The voltage signal is then frequency modulated and transmitted wirelessly to a remote station by a simple FM transmitter circuit. Finally, the received signal is demodulated by a conventional FM radio circuit, and the vibration measurement data can be recovered. Since this type of wireless sensor employs a simple FM circuit, they do not require any wireless data transmission protocols allowing a low-cost wireless sensor in compact format. The proposed concept of the wireless vibration measurement is experimentally verified by measuring vibration of an aluminum cantilever beam. The proposed sensor could potentially be an efficient and cost effective method for measuring vibration of remote structures for dynamic testing or structural health monitoring.

  11. Normal vibration frequencies of the vocal ligament

    PubMed Central

    Titze, Ingo R.; Hunter, Eric J.

    2006-01-01

    The vocal ligament is the tension-bearing element in the vocal folds at high pitches. It has traditionally been treated as a vibrating string, with only length and longitudinal stress governing its normal mode frequencies. Results of this investigation show that, when bending stiffness and variable cross section are included, the lowest normal mode frequency can more than double, depending on the strain of the ligament. This suggests that much higher phonation frequencies may be achievable than heretofore thought for a given vocal fold length (e.g., nearly 1000 Hz at 50% elongation over cadaveric resting length). It also brings back into the discussion the concept of “damping,” an old misnomer for a reduction of the effective length of vibration of the vocal folds by relatively stiff boundary segments known as macula flavae. A formula is given for correcting the ideal string equation for the lowest mode frequency to include bending stiffness and macula flavae effects. PMID:15139637

  12. Normal vibration frequencies of the vocal ligament

    NASA Astrophysics Data System (ADS)

    Titze, Ingo R.; Hunter, Eric J.

    2004-05-01

    The vocal ligament is the tension-bearing element in the vocal folds at high pitches. It has traditionally been treated as a vibrating string, with only length and longitudinal stress governing its normal mode frequencies. Results of this investigation show that, when bending stiffness and variable cross section are included, the lowest normal mode frequency can more than double, depending on the strain of the ligament. This suggests that much higher phonation frequencies may be achievable than heretofore thought for a given vocal fold length (e.g., nearly 1000 Hz at 50% elongation over cadaveric resting length). It also brings back into the discussion the concept of ``damping,'' an old misnomer for a reduction of the effective length of vibration of the vocal folds by relatively stiff boundary segments known as macula flavae. A formula is given for correcting the ideal string equation for the lowest mode frequency to include bending stiffness and macula flavae effects.

  13. Dynamic vibration absorbers for vibration control within a frequency band

    NASA Astrophysics Data System (ADS)

    Yang, Cheng; Li, Deyu; Cheng, Li

    2011-04-01

    The use of dynamic vibration absorbers to control the vibration of a structure in both narrow and broadbands is discussed in this paper. As a benchmark problem, a plate incorporating multiple vibration absorbers is formulated, leading to an analytical solution when the number of absorbers yields one. Using this analytical solution, control mechanisms of the vibration absorber in different frequency bandwidths are studied; the coupling properties due to the introduction of the absorber into the host structure are analyzed; and the control performance of the absorber in different control bandwidths is examined with respect to its damping and location. It is found that the interaction between the plate and the absorber by means of the reaction force from the absorber plays a dominant role in a narrow band control, while in a relatively broadband control the dissipation by the absorber damping governs the control performance. When control bandwidth further enlarges, the optimal locations of the absorbers are not only affected by the targeted mode, but also by the other plate modes. These locations need to be determined after establishing a trade-off between the targeted mode and other modes involved in the coupling. Finally, numerical findings are assessed based on a simply-supported plate and a fair agreement between the predicted and measured results is obtained.

  14. Iminopropadienones RN=C=C=C=O and bisiminopropadienes RN=C=C=C=NR: Matrix infrared spectra and anharmonic frequency calculations

    NASA Astrophysics Data System (ADS)

    Bégué, Didier; Baraille, Isabelle; Andersen, Heidi Gade; Wentrup, Curt

    2013-10-01

    Methyliminopropadienone MeN=C=C=C=O 1a was generated by flash vacuum thermolysis from four different precursors and isolated in solid argon. The matrix-isolation infrared spectrum is dominated by unusually strong anharmonic effects resulting in complex fine structure of the absorptions due to the NCCCO moiety in the 2200 cm-1 region. Doubling and tripling of the corresponding absorption bands are observed for phenyliminopropadienone PhN=C=C=C=O 1b and bis(phenylimino)propadiene PhN=C=C=C=NPh 9, respectively. Anharmonic vibrational frequency calculations allow the identification of a number of overtones and combination bands as the cause of the splittings for each molecule. This method constitutes an important tool for the characterization of reactive intermediates and unusual molecules by matrix-isolation infrared spectroscopy.

  15. Iminopropadienones RN=C=C=C=O and bisiminopropadienes RN=C=C=C=NR: matrix infrared spectra and anharmonic frequency calculations.

    PubMed

    Bégué, Didier; Baraille, Isabelle; Andersen, Heidi Gade; Wentrup, Curt

    2013-10-28

    Methyliminopropadienone MeN=C=C=C=O 1a was generated by flash vacuum thermolysis from four different precursors and isolated in solid argon. The matrix-isolation infrared spectrum is dominated by unusually strong anharmonic effects resulting in complex fine structure of the absorptions due to the NCCCO moiety in the 2200 cm(-1) region. Doubling and tripling of the corresponding absorption bands are observed for phenyliminopropadienone PhN=C=C=C=O 1b and bis(phenylimino)propadiene PhN=C=C=C=NPh 9, respectively. Anharmonic vibrational frequency calculations allow the identification of a number of overtones and combination bands as the cause of the splittings for each molecule. This method constitutes an important tool for the characterization of reactive intermediates and unusual molecules by matrix-isolation infrared spectroscopy.

  16. Nonlinear frequency response analysis of structural vibrations

    NASA Astrophysics Data System (ADS)

    Weeger, Oliver; Wever, Utz; Simeon, Bernd

    2014-12-01

    In this paper we present a method for nonlinear frequency response analysis of mechanical vibrations of 3-dimensional solid structures. For computing nonlinear frequency response to periodic excitations, we employ the well-established harmonic balance method. A fundamental aspect for allowing a large-scale application of the method is model order reduction of the discretized equation of motion. Therefore we propose the utilization of a modal projection method enhanced with modal derivatives, providing second-order information. For an efficient spatial discretization of continuum mechanics nonlinear partial differential equations, including large deformations and hyperelastic material laws, we employ the concept of isogeometric analysis. Isogeometric finite element methods have already been shown to possess advantages over classical finite element discretizations in terms of higher accuracy of numerical approximations in the fields of linear vibration and static large deformation analysis. With several computational examples, we demonstrate the applicability and accuracy of the modal derivative reduction method for nonlinear static computations and vibration analysis. Thus, the presented method opens a promising perspective on application of nonlinear frequency analysis to large-scale industrial problems.

  17. High Frequency Shock During Random Vibration Testing

    DTIC Science & Technology

    2016-05-10

    Testing Level Natural Frequency (Hz) Ch. 17 Q Factor Test 1: White Noise 192.5 47.97 Test 2: -18 dB 192.5 51.11 Test 3: -15 dB 192.5 50.14 Test 4...12 dB 192.5 52.55 Test 5: -9 dB 192.5 44.99 Test 6: -6 dB 190 47.22 Test 7: White Noise 192.5 48.78 • -6dB Random Input • Shock origination...c o u s ti c P re s s u re ( P a ) Pre and Post White Noise Comparison Resonant frequencies and damping are unchanged after the shock event during

  18. The strongest CO binding and the highest C-O stretching frequency.

    PubMed

    Saha, Ranajit; Pan, Sudip; Frenking, Gernot; Chattaraj, Pratim K; Merino, Gabriel

    2017-01-18

    A coupled-cluster study is performed on CO bound BeY complexes (Y = O, CO3, SO4, NH, NCN, and NBO) to understand the effect of attached ligands (Y) on the CO binding ability and C-O stretching frequency (νCO). Herein, we report that BeNCN has the highest CO binding ability (via both C- and O-side binding) among the studied neutral Be-based clusters, whereas OCBeSO4 has the highest νCO among the neutral carbonyls. The nature and extent of shift in νCO compared to free CO are explained in terms of change in polarization in the bonding orbitals of CO and relative contribution from OC→BeY or CO→BeY σ-donation, and OC←BeY or CO←BeY π-back-donation. The largest blue-shift in OCBeSO4 and the largest red-shift in COBeNH are consequences of the smallest OC←BeSO4 π-back-donation and the largest CO←BeNH π-back-donation, respectively.

  19. Ultrasound vibrometry using orthogonal- frequency-based vibration pulses.

    PubMed

    Zheng, Yi; Yao, Aiping; Chen, Shigao; Urban, Matthew W; Lin, Haoming; Chen, Xin; Guo, Yanrong; Chen, Ke; Wang, Tianfu; Chen, Siping

    2013-11-01

    New vibration pulses are developed for shear wave generation in a tissue region with preferred spectral distributions for ultrasound vibrometry applications. The primary objective of this work is to increase the frequency range of detectable harmonics of the shear wave. The secondary objective is to reduce the required peak intensity of transmitted pulses that induce the vibrations and shear waves. Unlike the periodic binary vibration pulses, the new vibration pulses have multiple pulses in one fundamental period of the vibration. The pulses are generated from an orthogonal-frequency wave composed of several sinusoidal signals, the amplitudes of which increase with frequency to compensate for higher loss at higher frequency in tissues. The new method has been evaluated by studying the shear wave propagation in in vitro chicken and swine liver. The experimental results show that the new vibration pulses significantly increase tissue vibration with a reduced peak ultrasound intensity, compared with the binary vibration pulses.

  20. Ultrasound Vibrometry Using Orthogonal Frequency Based Vibration Pulses

    PubMed Central

    Zheng, Yi; Yao, Aiping; Chen, Shigao; Urban, Matthew W.; Lin, Haoming; Chen, Xin; Guo, Yanrong; Chen, Ke; Wang, Tianfu; Chen, Shiping

    2014-01-01

    New vibration pulses are developed for shear wave generation in a tissue region with preferred spectral distributions for ultrasound vibrometry applications. The primary objective of this work is to increase the frequency range of detectable harmonics of the shear wave. The secondary objective is to reduce the required peak intensity of transmitted pulses that induce the vibrations and shear waves. Unlike the periodic binary vibration pulses, the new vibration pulses have multiple pulses in one fundamental period of the vibration. The pulses are generated from an orthogonal-frequency wave composed of several sinusoidal signals of which the amplitudes increase with frequency to compensate for higher loss at higher frequency in tissues. The new method has been evaluated by studying the shear wave propagation in in vitro chicken and swine liver. The experimental results show that the new vibration pulses significantly increase tissue vibration with a reduced peak ultrasound intensity, compared with the binary vibration pulses. PMID:24158291

  1. Tuning vibrational mode localization with frequency windowing

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaolu; Talbot, Justin J.; Steele, Ryan P.

    2016-09-01

    Local-mode coordinates have previously been shown to be an effective starting point for anharmonic vibrational spectroscopy calculations. This general approach borrows techniques from localized-orbital machinery in electronic structure theory and generates a new set of spatially localized vibrational modes. These modes exhibit a well-behaved spatial decay of anharmonic mode couplings, which, in turn, allows for a systematic, a priori truncation of couplings and increased computational efficiency. Fully localized modes, however, have been found to lead to unintuitive mixtures of characteristic motions, such as stretches and bends, and accordingly large bilinear couplings. In this work, a very simple, tunable localization frequency window is introduced, in order to realize the transition from normal modes to fully localized modes. Partial localization can be achieved by localizing only pairs of modes within this traveling frequency window, which allows for intuitive interpretation of modes. The optimal window size is suggested to be a few hundreds of wave numbers, based on small- to medium-sized test systems, including water clusters and polypeptides. The new sets of partially localized coordinates retain their spatial coupling decay behavior while providing a reduced number of potential energy evaluations for convergence of anharmonic spectra.

  2. The effects of vibration on explosive and reactive strength when applying individualized vibration frequencies.

    PubMed

    Di Giminiani, Riccardo; Tihanyi, Jozsef; Safar, Sandor; Scrimaglio, Renato

    2009-01-15

    The aim of this study was to assess the effects of 8 weeks of whole-body vibrations on explosive and reactive leg strength. Thirty-three physically active students took part in the study and were randomly assigned to an individualized-vibration group, a fixed-vibration group or a control group. The frequency of vibration was set to 30 Hz for the fixed-vibration group, whereas the frequency for the individualized-vibration group was determined by monitoring the participants' EMGrms activity. The participants in the two vibration groups were exposed three times a week for 8 weeks to a series of 10 x 1-min whole-body vibrations with a 1-min pause between series of vibrations and a 4-min pause after the first five series of vibrations. Jump height in the squat jump increased significantly in all three groups (by 11% for the individualized-vibration group, p=0.001; by 3% for the fixed-vibration group, p=0.011; and by 2% for the control group, p=0.006), but countermovement jump height was not affected. In continuous rebound jumps by the individualized-vibration group, jumping height increased by 22% (p=0.006) and power increased by 18% (p=0.002). The results of this study suggest that the use of an individualized vibration frequency produces a greater response from the neuromuscular system and is more beneficial than vibrations at a fixed pre-selected frequency.

  3. Low-Frequency Vibration Drilling of Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Okamura, Kiyoshi; Sasahara, Hiroyuki; Segawa, Toshiaki; Tsutsumi, Masaomi

    Dry drilling of composite/metallic stacks for aircraft components is extremely difficult to keep sufficient hole quality and efficiency of drilling process. Problems of the dry drilling of those kinds of stacks are chip ejection, chip formation and high temperature especially for titanium alloy. To clear these problems, low-frequency vibration (10-50Hz) drilling is proposed in this study. Controlled sinusoidal vibration was given in drill axis direction with constant feed motion. The relationship between vibration conditions, such as vibration amplitude, frequency and drill feed rate, and chip formation and drilling temperature were investigated. As a result, low-frequency vibration drilling can control chip formation to reduce chip jamming and can reduce drilling temperature. Temperature measured at the cap burr decreased by 300 degrees C or more when low-frequency vibration was applied compared with the conventional drilling. Also the wear rate of the drill is decreased when the vibration is applied.

  4. Frequency-Dependent Attenuation of Blasting Vibration Waves

    NASA Astrophysics Data System (ADS)

    Zhou, Junru; Lu, Wenbo; Yan, Peng; Chen, Ming; Wang, Gaohui

    2016-10-01

    The dominant frequency, in addition to the peak particle velocity, is a critical factor for assessing adverse effects of the blasting vibration on surrounding structures; however, it has not been fully considered in blasting design. Therefore, the dominant frequency-dependent attenuation mechanism of blast-induced vibration is investigated in the present research. Starting with blasting vibration induced by a spherical charge propagating in an infinite viscoelastic medium, a modified expression of the vibration amplitude spectrum was derived to reveal the frequency dependency of attenuation. Then, ground vibration induced by more complex and more commonly used cylindrical charge that propagates in a semi-infinite viscoelastic medium was analyzed by numerical simulation. Results demonstrate that the absorptive property of the medium results in the frequency attenuation versus distance, whereas a rapid drop or fluctuation occurs during the attenuation of ground vibration. Fluctuation usually appears at moderate to far field, and the dominant frequency generally decreases to half the original value when rapid drop occurs. The decay rate discrepancy between different frequency components and the multimodal structure of vibration spectrum lead to the unsmooth frequency-dependent attenuation. The above research is verified by two field experiments. Furthermore, according to frequency-based vibration standards, frequency drop and fluctuation should be considered when evaluating blast safety. An optimized piecewise assessment is proposed for more accurate evaluation: With the frequency drop point as the breakpoint, the assessment is divided into two independent sections along the propagating path.

  5. Driving an Active Vibration Balancer to Minimize Vibrations at the Fundamental and Harmonic Frequencies

    NASA Technical Reports Server (NTRS)

    Holliday, Ezekiel S. (Inventor)

    2014-01-01

    Vibrations of a principal machine are reduced at the fundamental and harmonic frequencies by driving the drive motor of an active balancer with balancing signals at the fundamental and selected harmonics. Vibrations are sensed to provide a signal representing the mechanical vibrations. A balancing signal generator for the fundamental and for each selected harmonic processes the sensed vibration signal with adaptive filter algorithms of adaptive filters for each frequency to generate a balancing signal for each frequency. Reference inputs for each frequency are applied to the adaptive filter algorithms of each balancing signal generator at the frequency assigned to the generator. The harmonic balancing signals for all of the frequencies are summed and applied to drive the drive motor. The harmonic balancing signals drive the drive motor with a drive voltage component in opposition to the vibration at each frequency.

  6. Rapid hyperspectral, vibrationally resonant sum-frequency generation microscopy

    NASA Astrophysics Data System (ADS)

    Hanninen, Adam M.; Potma, Eric O.

    2017-02-01

    We discuss the development and application of a laser-scanning, nonlinear optical microscope capable of generating vibrationally resonant images based on sum-frequency generation (SFG), coherent anti-Stokes Raman scattering (CARS) or third-order sum-frequency generation (TSFG). The combination of these three modalities allows vibrationally sensitive imaging of both χ (2) and χ (3)-active structures in biological tissues, addressing both Raman-active as well as IR-allowed vibrational modes. We show the practical utility of these vibrationally sensitive modalities by imaging collagen I rich tissues.

  7. Lattice vibrational modes and their frequency shifts in semiconductor nanowires.

    PubMed

    Yang, Li; Chou, M Y

    2011-07-13

    We have performed first-principles calculations to study the lattice vibrational modes and their Raman activities in silicon nanowires (SiNWs). Two types of characteristic vibrational modes are examined: high-frequency optical modes and low-frequency confined modes. Their frequencies have opposite size dependence with a red shift for the optical modes and a blue shift for the confined modes as the diameter of SiNWs decreases. In addition, our calculations show that these vibrational modes can be detected by Raman scattering measurements, providing an efficient way to estimate the size of SiNWs.

  8. Sweeping tuneable vibration absorbers for low-mid frequencies vibration control

    NASA Astrophysics Data System (ADS)

    Gardonio, P.; Zilletti, M.

    2015-10-01

    This paper presents a simulation study concerning the low-mid frequencies control of flexural vibration in a lightly damped thin plate, which is equipped with three sweeping tuneable vibration absorbers and is excited by a rain on the roof broad frequency band stationary disturbance. The sweeping tuneable vibration absorbers are semi-active mass-spring-dashpot systems whose stiffness and damping properties can be varied uniformly within given ranges. They are operated in such a way as their characteristic natural frequencies are continuously varied to control the response of flexural modes that resonate within given frequency bands. More specifically, in this study the three sweeping tuneable vibration absorbers are operated asynchronously, each within one of three sequential frequency bands comprised between 20 and 120, 120 and 220, 220 and 320 Hz. The flexural vibration control effects produced by the three sweeping tuneable vibration absorbers are compared to those produced by three classical tuneable vibration absorbers, each set to control the response of a specific flexural mode of the plate resonating in one of these three frequency bands. The study shows that the proposed sweeping tuneable vibration absorbers outperform the classical tuneable vibration absorbers and produce about 6, 5, 4 dB reduction of the plate overall flexural response in the three frequency bands of operation. Also, the study indicates that the sweeping tuneable vibration absorbers are robust to variations in the plate flexural response. For instance they still produce about 5.1, 5.3, 4.6 dB reductions of the flexural response in the three frequency bands of operation when the plate is tensioned such that the flexural natural frequencies are shifted up from about 40 percent, for the first resonance, to 7 percent, for the tenth resonance.

  9. Vibrating Frequency Thresholds in Mice and Rats: Implications for the Effects of Vibrations on Animal Health.

    PubMed

    Rabey, Karyne N; Li, Yao; Norton, John N; Reynolds, Randall P; Schmitt, Daniel

    2015-08-01

    Vibrations in research facilities can cause complex animal behavioral and physiological responses that can affect animal health and research outcomes. The goal of this study was to determine the range of frequency values, where animals are unable to attenuate vibrations, and therefore may be most susceptible to their effects. Anesthetized and euthanized adult rats and mice were exposed to vibration frequencies over a wide range (0-600 Hz) and at a constant magnitude of 0.3 m/s(2). Euthanized animals were additionally exposed to vibrations at an acceleration of 1 m/s(2). The data showed that at most frequencies rodents were able to attenuate vibration magnitudes, with values for the back-mounted accelerometer being substantially less than that of the table. At frequencies of 41-60 Hz mice did not attenuate vibration magnitude, but instead the magnitude of the table and animal were equal or amplified. Rats experienced the same pattern of non-attenuation between 31 and 50 Hz. Once euthanized, the mice vibrated at a slightly more elevated frequency (up to 100 Hz). Based on these results, it may be prudent that in laboratory settings, vibrations in the ranges reported here should be accounted for as possible contributors to animal stress and/or biomechanical changes.

  10. Experimental and theoretical study of absorption spectrum of the (CH3)2CO···HF complex. Influence of anharmonic interactions on the frequency and intensity of the C=O and H-F stretching bands.

    PubMed

    Bulychev, V P; Svishcheva, E A; Tokhadze, K G

    2014-01-03

    IR absorption spectra of mixtures (CH3)2CO/HF and free (CH3)2CO molecules are recorded in the region of 4000-900 cm(-1) with a Bruker IFS-125 HR vacuum Fourier spectrometer at room temperature with a resolution up to 0.02 cm(-1). Spectral characteristics of the 2ν(C=O) overtone band of free acetone are reliably measured. The ν1(HF) and ν(C=O) absorption bands of the (CH3)2CO···HF complex are obtained by subtracting the absorption bands of free HF and acetone and absorption lines of atmospheric water from the experimental spectrum of mixtures. The experimental data are compared with theoretical results obtained from variational solutions of 1D-4D vibrational Schrödinger equations. The anharmonic potential energy and dipole moment surfaces used in the calculations were computed in the MP2/6-311++G(2d,2p) approximation with corrections for the basis set superposition error. Comparison of the data derived from solutions for different combinations of vibrational degrees of freedom shows that taking the inter-mode anharmonic interactions into account has different effects on the transition frequencies and intensities. Particular attention has been given to elucidation of the influence of anharmonic coupling of the H-F and C=O stretches with the low-frequency intermolecular modes on their frequencies and intensities and the strength of resonance between the fundamental H-F and the first overtone C=O transitions.

  11. The interaction between body position and vibration frequency on acute response to whole body vibration.

    PubMed

    Di Giminiani, Riccardo; Masedu, Francesco; Tihanyi, Jozsef; Scrimaglio, Renato; Valenti, Marco

    2013-02-01

    The present study was designed to investigate the electromyographic (EMG) response in leg muscles to whole-body vibration while using different body positions and vibration frequencies. Twenty male sport sciences students voluntarily participated in this single-group, repeated-measures study in which EMG data from the vastus lateralis (VL) and the lateral gastrocnemius (LG) were collected over a total of 36 trials for each subject (4 static positions × 9 frequencies). We found that vibration frequency, body position and the muscle stimulated had a significant effect (P-values ranged from 0.001 to 0.031) on the EMG response. Similarly, the muscle × frequency and position × muscle interactions were significant (P < 0.001). Interestingly, the frequency × positions interactions were not significant (P > 0.05). Our results indicate that lower frequencies of vibration (25-35 Hz) result in maximal activation of LG, whereas higher frequencies (45-55 Hz) elicit the highest responses in the VL. In addition, the position P2 (half squat position with the heels raised) is beneficial both for VL and LG, independently of the vibration frequency. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Wettability of a surface subjected to high frequency mechanical vibrations.

    PubMed

    Galleguillos-Silva, R; Vargas-Hernández, Y; Gaete-Garretón, L

    2017-03-01

    Ultrasonic radiation can modify some physical properties in liquid/solid interactions, such as wettability. The dependence of solid surface wettability on its vibrational state was studied. Experiments with an interface formed by distilled water deposited on a titanium alloy and surrounded by air were carried out. It is shown that it is possible to control the apparent wettability of a given liquid/solid/gas system by applying sonic-ultrasonic vibrations of controlled amplitude at the interface. The system studied is composed of a drop of distilled water deposited on a flat titanium surface in air. The contact angle was used as an indicator of apparent wettability. It is shown that the apparent wettability of a surface is linearly dependent on the peak vibration velocity and independent of the vibration frequency. Higher vibration speed lowers the contact angle and therefore causes greater surface wettability. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Capacitance-Based Frequency Adjustment of Micro Piezoelectric Vibration Generator

    PubMed Central

    Mao, Xinhua; He, Qing; Li, Hong; Chu, Dongliang

    2014-01-01

    Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method. PMID:25133237

  14. Capacitance-based frequency adjustment of micro piezoelectric vibration generator.

    PubMed

    Mao, Xinhua; He, Qing; Li, Hong; Chu, Dongliang

    2014-01-01

    Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method.

  15. Low-frequency vibration measurement by a dual-frequency DBR fiber laser

    NASA Astrophysics Data System (ADS)

    Zhang, Bing; Cheng, Linghao; Liang, Yizhi; Jin, Long; Guo, Tuan; Guan, Bai-Ou

    2017-09-01

    A dual-frequency distributed Bragg reflector (DBR) fiber laser based sensor is demonstrated for low-frequency vibration measurement through the Doppler effect. The response of the proposed sensor is quite linear and is much higher than that of a conventional accelerometer. The proposed sensor can work down to 1 Hz with high sensitivity. Therefore, the proposed sensor is very efficient in low-frequency vibration measurement.

  16. Low-frequency vibration control of floating slab tracks using dynamic vibration absorbers

    NASA Astrophysics Data System (ADS)

    Zhu, Shengyang; Yang, Jizhong; Yan, Hua; Zhang, Longqing; Cai, Chengbiao

    2015-09-01

    This study aims to effectively and robustly suppress the low-frequency vibrations of floating slab tracks (FSTs) using dynamic vibration absorbers (DVAs). First, the optimal locations where the DVAs are attached are determined by modal analysis with a finite element model of the FST. Further, by identifying the equivalent mass of the concerned modes, the optimal stiffness and damping coefficient of each DVA are obtained to minimise the resonant vibration amplitudes based on fixed-point theory. Finally, a three-dimensional coupled dynamic model of a metro vehicle and the FST with the DVAs is developed based on the nonlinear Hertzian contact theory and the modified Kalker linear creep theory. The track irregularities are included and generated by means of a time-frequency transformation technique. The effect of the DVAs on the vibration absorption of the FST subjected to the vehicle dynamic loads is evaluated with the help of the insertion loss in one-third octave frequency bands. The sensitivities of the mass ratio of DVAs and the damping ratio of steel-springs under the floating slab are discussed as well, which provided engineers with the DVA's adjustable room for vibration mitigation. The numerical results show that the proposed DVAs could effectively suppress low-frequency vibrations of the FST when tuned correctly and attached properly. The insertion loss due to the attachment of DVAs increases as the mass ratio increases, whereas it decreases with the increase in the damping ratio of steel-springs.

  17. Electrostatic frequency shifts in amide I vibrational spectra: Direct parameterization against experiment

    PubMed Central

    Reppert, Mike; Tokmakoff, Andrei

    2013-01-01

    The interpretation of protein amide I infrared spectra has been greatly assisted by the observation that the vibrational frequency of a peptide unit reports on its local electrostatic environment. However, the interpretation of spectra remains largely qualitative due to a lack of direct quantitative connections between computational models and experimental data. Here, we present an empirical parameterization of an electrostatic amide I frequency map derived from the infrared absorption spectra of 28 dipeptides. The observed frequency shifts are analyzed in terms of the local electrostatic potential, field, and field gradient, evaluated at sites near the amide bond in molecular dynamics simulations. We find that the frequency shifts observed in experiment correlate very well with the electric field in the direction of the C=O bond evaluated at the position of the amide oxygen atom. A linear best-fit mapping between observed frequencies and electric field yield sample standard deviations of 2.8 and 3.7 cm−1 for the CHARMM27 and OPLS-AA force fields, respectively, and maximum deviations (within our data set) of 9 cm−1. These results are discussed in the broader context of amide I vibrational models and the effort to produce quantitative agreement between simulated and experimental absorption spectra. PMID:23574217

  18. Electrostatic frequency shifts in amide I vibrational spectra: Direct parameterization against experiment

    NASA Astrophysics Data System (ADS)

    Reppert, Mike; Tokmakoff, Andrei

    2013-04-01

    The interpretation of protein amide I infrared spectra has been greatly assisted by the observation that the vibrational frequency of a peptide unit reports on its local electrostatic environment. However, the interpretation of spectra remains largely qualitative due to a lack of direct quantitative connections between computational models and experimental data. Here, we present an empirical parameterization of an electrostatic amide I frequency map derived from the infrared absorption spectra of 28 dipeptides. The observed frequency shifts are analyzed in terms of the local electrostatic potential, field, and field gradient, evaluated at sites near the amide bond in molecular dynamics simulations. We find that the frequency shifts observed in experiment correlate very well with the electric field in the direction of the C=O bond evaluated at the position of the amide oxygen atom. A linear best-fit mapping between observed frequencies and electric field yield sample standard deviations of 2.8 and 3.7 cm-1 for the CHARMM27 and OPLS-AA force fields, respectively, and maximum deviations (within our data set) of 9 cm-1. These results are discussed in the broader context of amide I vibrational models and the effort to produce quantitative agreement between simulated and experimental absorption spectra.

  19. Vibrational frequency fluctuations of ionic vibrational probe in water: Theoretical study with molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Okuda, Masaki; Higashi, Masahiro; Ohta, Kaoru; Saito, Shinji; Tominaga, Keisuke

    2017-09-01

    The vibrational dynamics of SCN- in H2O are theoretically investigated by molecular dynamics simulations. Based on the vibrational solvatochromism theory, we calculate the frequency-frequency time correlation function of the SCN anti-symmetric stretching mode, which is characterized by time constants of 0.13 and 1.41 ps. We find that the frequency fluctuation is almost determined by the electrostatic interaction from the water molecules in the first-hydration shell. The collective dynamics of the water molecules in the first-hydration shell is found to be similar to that of bulk water, though the hydrogen bond between the ion and water molecule is very strong.

  20. The low frequency vibrational modes of green fluorescent proteins

    NASA Astrophysics Data System (ADS)

    Tozzini, V.; Bizzarri, A. R.; Pellegrini, V.; Nifosı̀, R.; Giannozzi, P.; Iuliano, A.; Cannistraro, S.; Beltram, F.

    2003-02-01

    We report the observation and analysis of the low frequency vibrational modes of green fluorescent proteins (GFPs). Our study exploits the surface enhanced Raman scattering technique, which allowed the analysis of the vibrational modes of the proteins down to 300 cm -1. Here we present results on two GFP mutants, namely S65T/F64L GFP (EGFP) and S65T/F64L/T203Y GFP (E 2GFP). These particularly bright mutants display almost inverted population ratio of anionic (B) to neutral (A) forms of the chromophore. By comparing the vibrational spectrum of the proteins with that of a synthetic model chromophore in solution and with the aid of first principle calculations based on density functional theory, we identify the Raman active bands in this region of frequencies. A dominant collective mode at 720 cm -1 is found and assigned to a collective planar deformation of the chromophore. Low frequency vibrational modes belonging specifically to A and/or B structural configurations are also identified. This work demonstrates the possibility of monitoring the structural sub-states of GFPs through vibrational spectroscopy in a range of frequencies where collective modes peculiar of the double ring structure of the chromophore lie.

  1. Perceptual Space of Superimposed Dual-Frequency Vibrations in the Hands.

    PubMed

    Hwang, Inwook; Seo, Jeongil; Choi, Seungmoon

    2017-01-01

    The use of distinguishable complex vibrations that have multiple spectral components can improve the transfer of information by vibrotactile interfaces. We investigated the qualitative characteristics of dual-frequency vibrations as the simplest complex vibrations compared to single-frequency vibrations. Two psychophysical experiments were conducted to elucidate the perceptual characteristics of these vibrations by measuring the perceptual distances among single-frequency and dual-frequency vibrations. The perceptual distances of dual-frequency vibrations between their two frequency components along their relative intensity ratio were measured in Experiment I. The estimated perceptual spaces for three frequency conditions showed non-linear perceptual differences between the dual-frequency and single-frequency vibrations. A perceptual space was estimated from the measured perceptual distances among ten dual-frequency compositions and five single-frequency vibrations in Experiment II. The effect of the component frequency and the frequency ratio was revealed in the perceptual space. In a percept of dual-frequency vibration, the lower frequency component showed a dominant effect. Additionally, the perceptual difference among single-frequency and dual-frequency vibrations were increased with a low relative difference between two frequencies of a dual-frequency vibration. These results are expected to provide a fundamental understanding about the perception of complex vibrations to enrich the transfer of information using vibrotactile stimuli.

  2. Perceptual Space of Superimposed Dual-Frequency Vibrations in the Hands

    PubMed Central

    Seo, Jeongil; Choi, Seungmoon

    2017-01-01

    The use of distinguishable complex vibrations that have multiple spectral components can improve the transfer of information by vibrotactile interfaces. We investigated the qualitative characteristics of dual-frequency vibrations as the simplest complex vibrations compared to single-frequency vibrations. Two psychophysical experiments were conducted to elucidate the perceptual characteristics of these vibrations by measuring the perceptual distances among single-frequency and dual-frequency vibrations. The perceptual distances of dual-frequency vibrations between their two frequency components along their relative intensity ratio were measured in Experiment I. The estimated perceptual spaces for three frequency conditions showed non-linear perceptual differences between the dual-frequency and single-frequency vibrations. A perceptual space was estimated from the measured perceptual distances among ten dual-frequency compositions and five single-frequency vibrations in Experiment II. The effect of the component frequency and the frequency ratio was revealed in the perceptual space. In a percept of dual-frequency vibration, the lower frequency component showed a dominant effect. Additionally, the perceptual difference among single-frequency and dual-frequency vibrations were increased with a low relative difference between two frequencies of a dual-frequency vibration. These results are expected to provide a fundamental understanding about the perception of complex vibrations to enrich the transfer of information using vibrotactile stimuli. PMID:28081187

  3. An innovative MRE absorber with double natural frequencies for wide frequency bandwidth vibration absorption

    NASA Astrophysics Data System (ADS)

    Sun, Shuaishuai; Yang, Jian; Li, Weihua; Deng, Huaxia; Du, Haiping; Alici, Gursel; Yan, Tianhong

    2016-05-01

    A new design of adaptive tuned vibration absorber was proposed in this study for vibration reduction. The innovation of the new absorber is the adoption of the eccentric mass on the top of the multilayered magnetorheological elastomer (MRE) structure so that this proposed absorber has two vibration modes: one in the torsional direction and the other in translational direction. This property enables the absorber to expand its effective bandwidth and to be more capable of reducing the vibrations especially dealing with those vibrations with multi-frequencies. The innovative MRE absorber was designed and tested on a horizontal vibration table. The test results illustrate that the MRE absorber realized double natural frequencies, both of which are controllable. Inertia’s influence on the dynamic behavior of the absorber is also investigated in order to guide the design of the innovative MRE absorber. Additionally, the experimentally obtained natural frequencies coincide with the theoretical data, which sufficiently verifies the feasibility of this new design. The last part in terms of the vibration absorption ability also proves that both of these two natural frequencies play a great role in absorbing vibration energy.

  4. Acoustic metamaterial structures based on multi-frequency vibration absorbers

    NASA Astrophysics Data System (ADS)

    Pai, P. Frank; Peng, Hao

    2014-03-01

    This paper presents a new metamaterial beam based on multi-frequency vibration absorbers for broadband vibration absorption. The proposed metamaterial beam consists of a uniform isotropic beam and small two-mass spring-mass- damper subsystems at many locations along the beam to act as multi-frequency vibration absorbers. For an infinite metamaterial beam, governing equations of a unit cell are derived using the extended Hamilton principle. The existence of two stopbands is demonstrated using a model based on averaging material properties over a cell length and a model based on finite element modeling and the Bloch-Floquet theory for periodic structures. For a finite metamaterial beam, because these two idealized models cannot be used for finite beams and/or elastic waves having short wavelengths, a finite-element method is used for detailed modeling and analysis. The concepts of negative effective mass and effective stiffness and how the spring-mass-damper subsystem creates two stopbands are explained in detail. Numerical simulations reveal that the actual working mechanism of the proposed metamaterial beam is based on the concept of conventional mechanical vibration absorbers. For an incoming wave with a frequency in one of the two stopbands, the absorbers are excited to vibrate in their optical modes to create shear forces to straighten the beam and stop the wave propagation. For an incoming wave with a frequency outside of but between the two stopbands, it can be efficiently damped out by the damper with the second mass of each absorber. Hence, the two stopbands are connected into a wide stopband. Numerical examples validate the concept and show that the structure's boundary conditions do not have significant influence on the absorption of high-frequency waves. However, for absorption of low-frequency waves, the structure's boundary conditions and resonance frequencies and the location and spatial distribution of absorbers need to be considered in design, and it

  5. Effect of vibration frequency on biopsy needle insertion force.

    PubMed

    Tan, Lei; Qin, Xuemei; Zhang, Qinhe; Zhang, Hongcai; Dong, Hongjian; Guo, Tuodang; Liu, Guowei

    2017-05-01

    Needle insertion is critical in many clinical medicine procedures, such as biopsy, brachytherapy, and injection therapy. A platform with two degrees of freedom was set up to study the effect of vibration frequency on needle insertion force. The gel phantom deformation at the needle cutting edge and the Voigt model are utilized to develop a dynamic model to explain the relationship between the insertion force and needle-tip velocity. The accuracy of this model was verified by performing needle insertions into phantom gel. The effect of vibration on insertion force can be explained as the vibration increasing the needle-tip velocity and subsequently increasing the insertion force. In a series of needle insertion experiments with different vibration frequencies, the peak forces were selected for comparison to explore the effect of vibration frequency on needle insertion force. The experimental results indicate that the insertion force at 500Hz increases up to 17.9% compared with the force at 50Hz. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  6. Vibration amplitude sonoelastography lesion imaging using low-frequency audible vibration

    NASA Astrophysics Data System (ADS)

    Taylor, Lawrence; Parker, Kevin

    2003-04-01

    Sonoelastography or vibration amplitude imaging is an ultrasound imaging technique in which low-amplitude, low-frequency shear waves, less than 0.1-mm displacement and 1-kHz frequency, are propagated deep into tissue, while real time Doppler techniques are used to image the resulting vibration pattern. Finite-element studies and experiments on tissue-mimicking phantoms verify that a discrete hard inhomogeneity present within a larger region of soft tissue will cause a decrease in the vibration field at its location. This forms the basis for tumor detection using sonoelastography. Real time relative imaging of the vibration field is possible because a vibrating particle will phase modulate an ultrasound signal. The particle's amplitude is directly proportional to the spectral spread of the reflected Doppler echo. Real time estimation of the variance of the Doppler power spectrum at each pixel allows the vibration field to be imaged. Results are shown for phantom lesions, thermal lesions, and 3-D in vitro and 2-D in vivo prostate cancer. MRI and whole mount histology is used to validate the system accuracy.

  7. Vibration frequencies of a constrained cantilever wedge

    NASA Astrophysics Data System (ADS)

    Craver, W. Lionel, Jr.; Lu, Yangshan

    1989-05-01

    This paper presents the solution for the natural frequencies of a beam tapered in one direction, or a wedge, with both a rotational and a translational constraint at a position along the length of the beam. The eigenfrequencies were determined using an incremental search and bisection method, accurate to the fourth decimal place. The taper ratio was varied from 1.4 to 5.0 and the dimensionless spring constants were varied from 0 to 1000. Graphs are provided to illustrate some results.

  8. Collagen and component polypeptides: Low frequency and amide vibrations

    NASA Astrophysics Data System (ADS)

    Fontaine-Vive, F.; Merzel, F.; Johnson, M. R.; Kearley, G. J.

    2009-01-01

    Collagen is a fibrous protein, which exists widely in the human body. The biomechanical properties of collagen depend on its triple helix structure and the corresponding low frequency vibrations. We use first-principles, density functional theory methods and analytical force fields to investigate the molecular vibrations of a model collagen compound, the results being validated by comparison with published, inelastic neutron scattering data. The results from these atomistic simulations are used at higher frequency to study the Amide I and V vibrations and therefore the vibrational signature of secondary and tertiary structure formation. In addition to collagen, its component homopolymers, poly-glycine and poly-proline are also studied. The Amide V vibration of glycine is strongly modified in going from the single helix of poly-glycine II to the triple helix of collagen. The collagen models are hydrated and this work allows us to discuss the relative merits of density functional theory and force field methods when tackling complex, partially crystalline systems.

  9. Neuropathy in female dental personnel exposed to high frequency vibrations.

    PubMed Central

    Akesson, I; Lundborg, G; Horstmann, V; Skerfving, S

    1995-01-01

    OBJECTIVE--To evaluate early neuropathy in dental personnel exposed to high frequency vibrations. METHODS--30 dentists and 30 dental hygienists who used low and high speed hand pieces and ultrasonic scalers were studied, and 30 dental assistants and 30 medical nurses not exposed to vibration (all women). Vibrotactile sensibility, strength, motor performance, sensorineural symptoms and signs, and vascular symptoms in the hands, as well as mercury concentrations in biological samples and cervicobrachial symptoms, were studied. RESULTS--The two groups exposed to vibration had significant impairments of vibrotactile sensibility, strength, and motor performance, as well as more frequent sensorineural symptoms. In the dentists there were significant associations between the vibrotactile sensibility and strength, motor performance, superficial sensibility, and sensorineural symptoms. There were no associations between these findings and cervicobrachial symptoms, mercury concentrations, or smoking. There was no increase of vascular symptoms of the hands in the groups exposed to vibration. CONCLUSION--Dental hygienists and dentists had a slight neuropathy, which may be associated with their exposure to high frequency vibrations, and which may be detrimental to their work performance. Thus, development of safer equipment is urgent. PMID:7757164

  10. Enhanced shock and vibration isolator for the attenuation of low-frequency vibration and high-frequency pyroshock loads

    NASA Astrophysics Data System (ADS)

    Han, Jae-Hung; Youn, Se-Hyun; Jeong, Ho-Kyung; Jang, Young-Soon

    2012-04-01

    Launch vehicles, satellites and aircrafts often experience harsh vibration and pyroshock loads during the flight including maneuvering and separation events, which may cause the malfunction of equipped electronic devices. Furthermore, this minor malfunction can generate catastrophic failure of the whole mission. To prevent malfunction of the electronic devices from severe shock and vibration loads, elastomeric isolators are commonly applied between the electronic device and the equipment bay structure in the aerospace fields. However, this rubber type elastomeric material is vulnerable to the low-frequency vibration load which involves large amount of displacement due to its low stiffness. Recently, the present authors proposed new type of isolator, called as pseudoelastic hybrid mesh isolator. This talk introduces the key features of this new pseudoelastic hybrid mesh isolator which shows better isolation performance throughout all frequency range than conventional isolators.

  11. Enhanced shock and vibration isolator for the attenuation of low-frequency vibration and high-frequency pyroshock loads

    NASA Astrophysics Data System (ADS)

    Han, Jae-Hung; Youn, Se-Hyun; Jeong, Ho-Kyung; Jang, Young-Soon

    2011-11-01

    Launch vehicles, satellites and aircrafts often experience harsh vibration and pyroshock loads during the flight including maneuvering and separation events, which may cause the malfunction of equipped electronic devices. Furthermore, this minor malfunction can generate catastrophic failure of the whole mission. To prevent malfunction of the electronic devices from severe shock and vibration loads, elastomeric isolators are commonly applied between the electronic device and the equipment bay structure in the aerospace fields. However, this rubber type elastomeric material is vulnerable to the low-frequency vibration load which involves large amount of displacement due to its low stiffness. Recently, the present authors proposed new type of isolator, called as pseudoelastic hybrid mesh isolator. This talk introduces the key features of this new pseudoelastic hybrid mesh isolator which shows better isolation performance throughout all frequency range than conventional isolators.

  12. Acoustic metamaterial panels based on multi frequency vibration absorbers

    NASA Astrophysics Data System (ADS)

    Shi, Chao; Sun, Hongwei; Hu, Xiaolei; Gu, Jinliang

    2016-04-01

    Presented here is a new metamaterial panel based on multi-frequency vibration absorbers for broadband vibration absorption. The proposed metamaterial panel consists of a uniform isotropic panel and small two-mass spring-mass-damper subsystem many locations along the panel to act as multi-frequency vibration absorbers. The existence of two stopbands is demonstrated using a model based on averaging material properties over a cell length and a model based on finite element modeling and the Bloch-Floquet theory for periodic structures. For a finite metamaterial panel, because these two idealized models can not be used for finite panels and/or elastic waves having short wavelengths, a finite-element method is used for detailed modeling and analysis. The concepts of negative effective stiffness is explained in detail. For an incoming wave with a frequency in one of the two stopbands, the absorbers are excited to vibrate in their optical modes to create shear forces to straighten the panel and stop the wave propagation. For an incoming wave with a frequency outside of but between the two stopbands, it can be efficiently damped out by the damper with these mass of each absorber. Hence, the two stopbands are connected in to a wide stopband. Numerical examples validate the concept and show that the structures boundary conditions do not have significant influence on the absorption of high-frequency waves. However, for absorption of low-frequency waves, the structures boundary conditions and resonance frequencies and the location and spatial distribution of absorbers need to be considered in design, and it is better to use heavier masses for absorbers.

  13. Mutual Co-Assignment of the Calculated Vibrational Frequencies in the Ground and Lowest Excited Electronic States

    NASA Astrophysics Data System (ADS)

    Panchenko, Yurii N.

    2013-06-01

    The shifts of the molecular vibrational frequencies when going from the ground electronic state to the lowest excited electronic states pose some problems for the mutual co-assignment of the calculated vibrational frequencies in the different excited states. The trans-{C_2 O_2 F_2} shift of the frequency of the symmetrical ν(C=O) stretching vibration between the S_0 and T_1 is 373 wn. The feasibility of mutual co-assignments of the vibrational frequencies in these electronic states has been demonstrated for trans-{C_2 O_2 F_2}. Matrices analogous to the Duschinsky matrix were used to juxtapose the a_g vibrational frequencies of this molecule calculated at the CASPT2/cc-pVTZ level in the ground S_0 and excited triplet T_1 and singlet S_1 electronic states. The analog of the Duschinsky matrix D was obtained for this molecule using the equation D = (L_{I})^{-1} L_{II} where L_{I} and L_{II} are the matrices of the vibrational modes (normalized atomic displacements) obtained by solving the vibrational problems for the S_0 and T_1 electronic states, respectively. Choosing the dominant elements in columns of the D matrix and permuting these columns to arrange these elements along the diagonal of the transformed matrix D^* makes it possible to establish the correct mutual co-assignments of the calculated a_g vibrational frequencies of the trans-{C_2 O_2 F_2} molecule in the S_0 and T_1 electronic states. The analogous procedure was performed for the trans-{C_2 O_2 F_2} molecule in the T_1 and S_1 excited electronic states. The recent reassignments of the νb{2} and νb{3} calculated vibrational frequencies in the trans-{C_2 O_2 F_2} molecule in the ground state were also obtained for the triplet T_1 and singlet S_1 excited electronic states. The approach set forth in this text makes it possible to juxtapose the calculated vibrational frequencies of the same molecule in the different electronic states and to refine the assignments of these frequencies. This is essential

  14. Low-frequency vibration environment for five Shuttle missions

    NASA Technical Reports Server (NTRS)

    Baugher, George R.; Martin, Gary L.; Delombard, Richard

    1993-01-01

    The Microgravity Science and Applications Division's (MSAD) program to record and analyze the Shuttle's vibration environment is reviewed. This program provides microgravity science investigators with time and frequency analyses of the acceleration environment during their experiments' operation. Information is also provided for future investigators on the expected Shuttle vibration environment. As background, the two major elements of the program are discussed, the Space Acceleration Measurement System (SAMS) and the Acceleration Characterization and Analysis Project (ACAP). A comparison of the acceleration measurements from five Shuttle missions is discussed.

  15. Use of chaotic and random vibrations to generate high frequency test inputs: Part 2, Chaotic vibrations

    SciTech Connect

    Paez, T.L.; Gregory, D.L.

    1990-01-01

    This paper and a companion paper show that the traditional limits on amplitude and frequency that can be generated in a laboratory test on a vibration exciter can be substantially extended. This is accomplished by attaching a device to the shaker that permits controlled metal to metal impacts that generate a high acceleration, high frequency environment on a test surface. A companion paper derives some of the mechanical relations for the system. This paper shows that a sinusoidal shaker input can be used to excite deterministic chaotic dynamics of the system yielding a random vibration environment on the test surface, or a random motion of the shaker can be used to generate a random vibration environment on the test surface. Numerical examples are presented to show the kind of environments that can be generated in this system. 9 refs., 9 figs.

  16. A Solvatochromic Model Calibrates Nitriles’ Vibrational Frequencies to Electrostatic Fields

    PubMed Central

    Bagchi, Sayan; Fried, Stephen D.; Boxer, Steven G.

    2012-01-01

    Electrostatic interactions provide a primary connection between a protein’s three-dimensional structure and its function. Infrared (IR) probes are useful because vibrational frequencies of certain chemical groups, such as nitriles, are linearly sensitive to local electrostatic field, and can serve as a molecular electric field meter. IR spectroscopy has been used to study electrostatic changes or fluctuations in proteins, but measured peak frequencies have not been previously mapped to total electric fields, because of the absence of a field-frequency calibration and the complication of local chemical effects such as H-bonds. We report a solvatochromic model that provides a means to assess the H-bonding status of aromatic nitrile vibrational probes, and calibrates their vibrational frequencies to electrostatic field. The analysis involves correlations between the nitrile’s IR frequency and its 13C chemical shift, whose observation is facilitated by a robust method for introducing isotopes into aromatic nitriles. The method is tested on the model protein Ribonuclease S (RNase S) containing a labeled p-CN-Phe near the active site. Comparison of the measurements in RNase S against solvatochromic data gives an estimate of the average total electrostatic field at this location. The value determined agrees quantitatively with MD simulations, suggesting broader potential for the use of IR probes in the study of protein electrostatics. PMID:22694663

  17. A solvatochromic model calibrates nitriles' vibrational frequencies to electrostatic fields.

    PubMed

    Bagchi, Sayan; Fried, Stephen D; Boxer, Steven G

    2012-06-27

    Electrostatic interactions provide a primary connection between a protein's three-dimensional structure and its function. Infrared probes are useful because vibrational frequencies of certain chemical groups, such as nitriles, are linearly sensitive to local electrostatic field and can serve as a molecular electric field meter. IR spectroscopy has been used to study electrostatic changes or fluctuations in proteins, but measured peak frequencies have not been previously mapped to total electric fields, because of the absence of a field-frequency calibration and the complication of local chemical effects such as H-bonds. We report a solvatochromic model that provides a means to assess the H-bonding status of aromatic nitrile vibrational probes and calibrates their vibrational frequencies to electrostatic field. The analysis involves correlations between the nitrile's IR frequency and its (13)C chemical shift, whose observation is facilitated by a robust method for introducing isotopes into aromatic nitriles. The method is tested on the model protein ribonuclease S (RNase S) containing a labeled p-CN-Phe near the active site. Comparison of the measurements in RNase S against solvatochromic data gives an estimate of the average total electrostatic field at this location. The value determined agrees quantitatively with molecular dynamics simulations, suggesting broader potential for the use of IR probes in the study of protein electrostatics.

  18. Low Frequency Vibration Energy Harvesting using Diamagnetically Stabilized Magnet Levitation

    NASA Astrophysics Data System (ADS)

    Palagummi, Sri Vikram

    Over the last decade, vibration-based energy harvesting has provided a technology push on the feasibility of self-powered portable small electronic devices and wireless sensor nodes. Vibration energy harvesters in general transduce energy by damping out the environmentally induced relative emotion through either a cantilever beam or an equivalent suspension mechanism with one of the transduction mechanisms, like, piezoelectric, electrostatic, electromagnetic or magnetostrictive. Two major challenges face the present harvesters in literature, one, they suffer from the unavoidable mechanical damping due to internal friction present in the systems, second, they cannot operate efficiently in the low frequency range (< 10 Hz), when most of the ambient vibrational energy is in this low frequency broadband range. Passive and friction free diamagnetically stabilized magnet levitation mechanisms which can work efficiently as a vibration energy harvester in the low frequency range are discussed in this work. First, a mono-stable vertical diamagnetic levitation (VDL) based vibration energy harvester (VEH) is discussed. The harvester consists of a lifting magnet (LM), a floating magnet (FM) and two diamagnetic plates (DPs). The LM balances out the weight of the FM and stability is brought about by the repulsive effect of the DPs, made of pyrolytic graphite. Two thick cylindrical coils, placed in grooves which are engraved in the DPs, are used to convert the mechanical energy into electrical energy. Experimental frequency response of the system is validated by the theoretical analysis which showed that the VEH works in a low frequency range but sufficient levitation gap was not achieved and the frequency response characteristic of the system was effectively linear. To overcome these challenges, the influence of the geometry of the FM, the LM, and the DP were parametrically studied to assess their effects on the levitation gap, size of the system and the natural frequency. For

  19. Frequency identification of vibration signals using video camera image data.

    PubMed

    Jeng, Yih-Nen; Wu, Chia-Hung

    2012-10-16

    This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC) can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system.

  20. Frequency Identification of Vibration Signals Using Video Camera Image Data

    PubMed Central

    Jeng, Yih-Nen; Wu, Chia-Hung

    2012-01-01

    This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC) can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system. PMID:23202026

  1. Effects of broad frequency vibration on cultured osteoblasts

    NASA Technical Reports Server (NTRS)

    Tanaka, Shigeo M.; Li, Jiliang; Duncan, Randall L.; Yokota, Hiroki; Burr, David B.; Turner, Charles H.

    2003-01-01

    Bone is subjected in vivo to both high amplitude, low frequency strain, incurred by locomotion, and to low amplitude, broad frequency strain. The biological effects of low amplitude, broad frequency strain are poorly understood. To evaluate the effects of low amplitude strains ranging in frequency from 0 to 50 Hz on osteoblastic function, we seeded MC3T3-E1 cells into collagen gels and applied the following loading protocols for 3 min per day for either 3 or 7 days: (1) sinusoidal strain at 3 Hz, with 0-3000 microstrain peak-to-peak followed by 0.33 s resting time, (2) "broad frequency vibration" of low amplitude strain (standard deviation of 300 microstrain) including frequency components from 0 to 50 Hz, and (3) sinusoidal strain combined with broad frequency vibration (S + V). The cells were harvested on day 4 or 8. We found that the S + V stimulation significantly repressed cell proliferation by day 8. Osteocalcin mRNA was up-regulated 2.6-fold after 7 days of S + V stimulation, and MMP-9 mRNA was elevated 1.3-fold after 3 days of vibration alone. Sinusoidal stimulation alone did not affect the cell responses. No differences due to loading were observed in alkaline phosphatase activity and in mRNA levels of type I collagen, osteopontin, connexin 43, MMPs-1A, -3, -13. These results suggest that osteoblasts are more sensitive to low amplitude, broad frequency strain, and this kind of strain could sensitize osteoblasts to high amplitude, low frequency strain. This suggestion implies a potential contribution of stochastic resonance to the mechanical sensitivity of osteoblasts. Copyright 2002 Elsevier Science Ltd.

  2. Effects of broad frequency vibration on cultured osteoblasts

    NASA Technical Reports Server (NTRS)

    Tanaka, Shigeo M.; Li, Jiliang; Duncan, Randall L.; Yokota, Hiroki; Burr, David B.; Turner, Charles H.

    2003-01-01

    Bone is subjected in vivo to both high amplitude, low frequency strain, incurred by locomotion, and to low amplitude, broad frequency strain. The biological effects of low amplitude, broad frequency strain are poorly understood. To evaluate the effects of low amplitude strains ranging in frequency from 0 to 50 Hz on osteoblastic function, we seeded MC3T3-E1 cells into collagen gels and applied the following loading protocols for 3 min per day for either 3 or 7 days: (1) sinusoidal strain at 3 Hz, with 0-3000 microstrain peak-to-peak followed by 0.33 s resting time, (2) "broad frequency vibration" of low amplitude strain (standard deviation of 300 microstrain) including frequency components from 0 to 50 Hz, and (3) sinusoidal strain combined with broad frequency vibration (S + V). The cells were harvested on day 4 or 8. We found that the S + V stimulation significantly repressed cell proliferation by day 8. Osteocalcin mRNA was up-regulated 2.6-fold after 7 days of S + V stimulation, and MMP-9 mRNA was elevated 1.3-fold after 3 days of vibration alone. Sinusoidal stimulation alone did not affect the cell responses. No differences due to loading were observed in alkaline phosphatase activity and in mRNA levels of type I collagen, osteopontin, connexin 43, MMPs-1A, -3, -13. These results suggest that osteoblasts are more sensitive to low amplitude, broad frequency strain, and this kind of strain could sensitize osteoblasts to high amplitude, low frequency strain. This suggestion implies a potential contribution of stochastic resonance to the mechanical sensitivity of osteoblasts. Copyright 2002 Elsevier Science Ltd.

  3. Peroxyacetyl radical: Electronic excitation energies, fundamental vibrational frequencies, and symmetry breaking in the first excited state

    SciTech Connect

    Copan, Andreas V.; Wiens, Avery E.; Nowara, Ewa M.; Schaefer, Henry F.; Agarwal, Jay

    2015-02-07

    Peroxyacetyl radical [CH{sub 3}C(O)O{sub 2}] is among the most abundant peroxy radicals in the atmosphere and is involved in OH-radical recycling along with peroxyacetyl nitrate formation. Herein, the ground (X{sup ~}) and first (A{sup ~}) excited state surfaces of cis and trans peroxyacetyl radical are characterized using high-level ab initio methods. Geometries, anharmonic vibrational frequencies, and adiabatic excitation energies extrapolated to the complete basis-set limit are reported from computations with coupled-cluster theory. Excitation of the trans conformer is found to induce a symmetry-breaking conformational change due to second-order Jahn-Teller interactions with higher-lying excited states. Additional benchmark computations are provided to aid future theoretical work on peroxy radicals.

  4. Multiple vibration displacements at multiple vibration frequencies stress impact on human femur computational analysis.

    PubMed

    Ezenwa, Bertram; Yeoh, Han Teik

    2011-01-01

    Whole-body vibration training using single-frequency methods has been reported to improve bone mineral density. However, the intensities can exceed safe levels and have drawn unfavorable comments from subjects. In a previous article, whole-body vibration training using multiple vibration displacements at multiple vibration frequencies (MVDMVF) was reported. This article presents the computational simulation evaluation of stress dispersion on a femur with and without the MVDMVF input. A model of bone femur was developed from a computed tomography image of the lower limb with Mimics software from Materialise (Plymouth, Michigan). We analyzed the mesh model in COMSOL Multiphysics (COMSOL, Inc; Burlington, Massachusetts) with and without MVDMVF input, with constraints and load applied to the femur model. We compared the results with published joint stresses during walking, jogging, and stair-climbing and descending and with standard vibration exposure limits. Results showed stress levels on the femur are significantly higher with MVDMVF input than without. The stress levels were within the published levels during walking and stair-climbing and descending but below the stress levels during jogging. Our computational results demonstrate that MVDMVF generates stress level equivalent to the level during walking and stair-climbing. This evidence suggests that MVDMVF is safe for prolonged use in subjects with osteoporosis who ambulate independently.

  5. A Sub-Hertz, Low-Frequency Vibration Isolation Platform

    NASA Technical Reports Server (NTRS)

    Ortiz, Gerardo, G.; Farr, William H.; Sannibale, Virginio

    2011-01-01

    One of the major technical problems deep-space optical communication (DSOC) systems need to solve is the isolation of the optical terminal from vibrations produced by the spacecraft navigational control system and by the moving parts of onboard instruments. Even under these vibration perturbations, the DSOC transceivers (telescopes) need to be pointed l000 fs of times more accurately than an RF communication system (parabolic antennas). Mechanical resonators have been extensively used to provide vibration isolation for groundbased, airborne, and spaceborne payloads. The effectiveness of these isolation systems is determined mainly by the ability of designing a mechanical oscillator with the lowest possible resonant frequency. The Low-Frequency Vibration Isolation Platform (LFVIP), developed during this effort, aims to reduce the resonant frequency of the mechanical oscillators into the sub-Hertz region in order to maximize the passive isolation afforded by the 40 dB/decade roll-off response of the resonator. The LFVIP also provides tip/tilt functionality for acquisition and tracking of a beacon signal. An active control system is used for platform positioning and for dampening of the mechanical oscillator. The basic idea in the design of the isolation platform is to use a passive isolation strut with an approximately equal to 100-mHz resonance frequency. This will extend the isolation range to lower frequencies. The harmonic oscillator is a second-order lowpass filter for mechanical disturbances. The resonance quality depends on the dissipation mechanisms, which are mainly hysteretic because of the low resonant frequency and the absence of any viscous medium. The LFVIP system is configured using the well-established Stewart Platform, which consists of a top platform connected to a base with six extensible struts (see figure). The struts are attached to the base and to the platform via universal joints, which permit the extension and contraction of the struts. The

  6. Self-mixing vibration measurement using emission frequency sinusoidal modulation

    NASA Astrophysics Data System (ADS)

    Tao, Yufeng; Wang, Ming; Guo, Dongmei; Hao, Hui; Liu, Qiang

    2015-04-01

    In this paper, a simplified phase demodulation scheme is applied to recover vibration trail on a laser self-mixing interferometer for noncontact vibration measurement. The emission of semiconductor laser diode is modulated by injecting sinusoidal wave, and corresponding interference signal is a quasi-sinusoid wave. The vibration mathematical model for semiconductor laser diode is theoretically educed from basic self-mixing theory, the variation of target is converted into phase information. The simulation of demodulation algorithm and standard deviation are presented and the reconstructed waveform displays a desirable consistence with various moving trails. Following the principle, a minimum experimental system is established and position variation of the target mirror driven by voltage signal is translated into phase shifts, feedback is controlled at weak level during experiment, Fourier transform is implemented to analyze phase information. The comparisons of both amplitude and velocity with a Germany Doppler vibrometer are performed to testify vibration model, the error of proposed demodulation method is less than 30 nm and achieve a high accuracy in vibration frequency. The experimental results indicate the traditional phase technology can be applied on complex optical power signal after adaption providing a feasible application prospects in industrial and scientific situation with an inexpensive semiconductor laser.

  7. Configurations of high-frequency ultrasonics complex vibration systems for packaging in microelectronics.

    PubMed

    Tsujino, Jiromaru; Harada, Yoshiki; Ihara, Shigeru; Kasahara, Kohei; Shimizu, Masanori; Ueoka, Tetsugi

    2004-04-01

    Ultrasonic high-frequency complex vibrations are effective for various ultrasonic high-power applications. Three types of ultrasonic complex vibration system with a welding tip vibrating elliptical to circular locus for packaging in microelectronics were studied. The complex vibration sources are using (1) a longitudinal-torsional vibration converter with diagonal slits that is driven only by a longitudinal vibration source, (2) a complex transverse vibration rod with several stepped parts that is driven by two longitudinal vibration source crossed at a right angle and (3) a longitudinal vibration circular disk and three longitudinal transducers that are installed at the circumference of the disk.

  8. Time frequency analyses of vibrations of wind turbine towers

    NASA Astrophysics Data System (ADS)

    Chiang, Chih-Hung; Huang, Chi-Luen; Hsu, Keng-Tseng; Cheng, Chia-Chi; Yu, Chih-Peng; Lai, Jiunnren

    2015-04-01

    Transient vibrations of the tower supporting a horizontal-axis wind turbine were recorded using a microwave interferometer. Variations in dominant frequencies have been reported in the previous study. Signal analyses aiming to uncouple different frequency components were performed using reassigned spectrogram, a time-frequency representation based on time-corrected short time Fourier transform. Optimal resolutions in both time and frequency domains were first investigated using synthetic signals. The goal was to seek out the favorable combinations of window size and overlapping portions of adjacent windows for a data sequence at a given sampling rate. The dominant frequency found in reassigned spectrogram agrees with that obtained using Fourier spectrum of the same transient measurements of the wind turbine tower under investigation.

  9. Moving toward low frequencies active vibration control with inertial actuators

    NASA Astrophysics Data System (ADS)

    Cinquemani, S.; Costa, A.; Resta, F.

    2017-04-01

    In applications of vibration suppression, control forces ideally act on the structure increasing its damping. While the frequency response of the structure is guaranteed to have a positive real part under ideal conditions, in practice a stability limit exists when inertial actuators are used. In this case the system response is no longer guaranteed to be positive real and so the control system may become unstable at high gains. Moreover, traditional approaches suggest the use of inertial actuators only if its natural frequency is well below the natural frequency of the structure, thus preventing their use at low frequencies. This paper proposes an interesting technique to enlarge the operational range to lower frequencies and to allow the use of inertial actuators. The approach is numerically tested and experimentally validated on a test rig.

  10. Optimisation of Dynamic Vibration Absorbers Over a Frequency Band

    NASA Astrophysics Data System (ADS)

    Rade, Domingos Alves; Steffen, Valder

    2000-09-01

    This paper is focused on the reduction of vibration levels of mechanical systems using dynamic vibration absorbers (DVAs). A general methodology is proposed for the optimum selection of DVA parameters so as to guarantee the efficiency of those devices over a previously selected frequency band. The presented methodology utilises a substructure coupling technique exploring frequency response functions (FRFs), which enables one to calculate the FRFs of the composite structure (primary system+DVAs), from the FRFs of the primary structure and the theoretical expressions of the FRFs of the DVAs. The FRFs of the composite structure, which are expressed as functions of the DVA parameters, are then used to define scalar performance indexes related to the vibration levels of the composite structure over the selected frequency band. These performance indexes are optimised with respect to the DVA parameters by solving a general non-linear constrained optimisation problem. The first part of the paper is devoted to the formulation of the substructure coupling method and the optimisation procedures. Numerical applications using experimentally acquired FRFs are then presented to illustrate the main features of the proposed methodology.

  11. Internal resonance and low frequency vibration energy harvesting

    NASA Astrophysics Data System (ADS)

    Yang, Wei; Towfighian, Shahrzad

    2017-09-01

    A nonlinear vibration energy harvester with internal resonance is presented. The proposed harvester consists of two cantilevers, each with a permanent magnet on its tip. One cantilever has a piezoelectric layer at its base. When magnetic force is applied this two degrees-of-freedom nonlinear vibration system shows the internal resonance phenomenon that broadens the frequency bandwidth compared to a linear system. Three coupled partial differential equations are obtained to predict the dynamic behavior of the nonlinear energy harvester. The perturbation method of multiple scales is used to solve equations. Results from experiments done at different vibration levels with varying distances between the magnets validate the mathematical model. Experiments and simulations show the design outperforms the linear system by doubling the frequency bandwidth. Output voltage for frequency response is studied for different system parameters. The optimal load resistance is obtained for the maximum power in the internal resonance case. The results demonstrate that a design combining internal resonance and magnetic nonlinearity improves the efficiency of energy harvesting.

  12. Surface sum-frequency vibrational spectroscopy of nonpolar media

    SciTech Connect

    Sun, Shumei; Tian, Chuanshan; Shen, Y. Ron

    2015-04-27

    Sum-frequency generation spectroscopy is surface specific only if the bulk contribution to the signal is negligible. Negligible bulk contribution is, however, not necessarily true, even for media with inversion symmetry. The inevitable challenge is to find the surface spectrum in the presence of bulk contribution, part of which has been believed to be inseparable from the surface contribution. Here, we show that, for nonpolar media, it is possible to separately deduce surface and bulk spectra from combined phase-sensitive sum-frequency vibrational spectroscopic measurements in reflection and transmission. Finally, the study of benzene interfaces is presented as an example.

  13. Vibrational frequencies for Be3 and Be4

    NASA Technical Reports Server (NTRS)

    Rendell, Alistair P.; Lee, Timothy J.; Taylor, Peter R.

    1990-01-01

    The harmonic frequencies of Be3 and Be4, evaluated by multireference configuration-interaction (MRCI) and singles and doubles coupled-cluster (CCSD) methods, are reported, as are IR intensities evaluated by using the double harmonic approximation. A comparison of the results shows that the CCSD method augmented with a correction for connected triple excitations, CCSD(T), can be a viable alternative to MRCI for determining the ground-state properties of small Be clusters (other than the dimer). Results of normal mode analyses indicate that the anharmonic vibrational frequencies of Be3 and Be4 are reasonably consistent at the CCSD, CCSD(T), or MRCI levels of treatment.

  14. Cross-Propagation Sum-Frequency Generation Vibrational Spectroscopy

    SciTech Connect

    Fu, Li; Chen, Shun-li; Gan, Wei; Wang, Hong-fei

    2016-02-27

    Here we report the theory formulation and the experiment realization of sum-frequency generation vibrational spectroscopy (SFG-VS) in the cross-propagation (XP) geometry or configuration. In the XP geometry, the visible and the infrared (IR) beams in the SFG experiment are delivered to the same location on the surface from visible and IR incident planes perpendicular to each other, avoiding the requirement to have windows or optics to be transparent to both the visible and IR frequencies. Therefore, the XP geometry is applicable to study surfaces in the enclosed vacuum or high pressure chambers with far infrared (FIR) frequencies that can directly access the metal oxide and other lower frequency surface modes, with much broader selection of visible and IR transparent window materials.

  15. Microscale capillary wave turbulence excited by high frequency vibration.

    PubMed

    Blamey, Jeremy; Yeo, Leslie Y; Friend, James R

    2013-03-19

    Low frequency (O(10 Hz-10 kHz)) vibration excitation of capillary waves has been extensively studied for nearly two centuries. Such waves appear at the excitation frequency or at rational multiples of the excitation frequency through nonlinear coupling as a result of the finite displacement of the wave, most often at one-half the excitation frequency in so-called Faraday waves and twice this frequency in superharmonic waves. Less understood, however, are the dynamics of capillary waves driven by high-frequency vibration (>O(100 kHz)) and small interface length scales, an arrangement ideal for a broad variety of applications, from nebulizers for pulmonary drug delivery to complex nanoparticle synthesis. In the few studies conducted to date, a marked departure from the predictions of classical Faraday wave theory has been shown, with the appearance of broadband capillary wave generation from 100 Hz to the excitation frequency and beyond, without a clear explanation. We show that weak wave turbulence is the dominant mechanism in the behavior of the system, as evident from wave height frequency spectra that closely follow the Rayleigh-Jeans spectral response η ≈ ω(-17/12) as a consequence of a period-halving, weakly turbulent cascade that appears within a 1 mm water drop whether driven by thickness-mode or surface acoustic Rayleigh wave excitation. However, such a cascade is one-way, from low to high frequencies. The mechanism of exciting the cascade with high-frequency acoustic waves is an acoustic streaming-driven turbulent jet in the fluid bulk, driving the fundamental capillary wave resonance through the well-known coupling between bulk flow and surface waves. Unlike capillary waves, turbulent acoustic streaming can exhibit subharmonic cascades from high to low frequencies; here it appears from the excitation frequency all the way to the fundamental modes of the capillary wave at some four orders of magnitude in frequency less than the excitation frequency

  16. Long-range vibration sensor based on correlation analysis of optical frequency-domain reflectometry signals.

    PubMed

    Ding, Zhenyang; Yao, X Steve; Liu, Tiegen; Du, Yang; Liu, Kun; Han, Qun; Meng, Zhuo; Chen, Hongxin

    2012-12-17

    We present a novel method to achieve a space-resolved long- range vibration detection system based on the correlation analysis of the optical frequency-domain reflectometry (OFDR) signals. By performing two separate measurements of the vibrated and non-vibrated states on a test fiber, the vibration frequency and position of a vibration event can be obtained by analyzing the cross-correlation between beat signals of the vibrated and non-vibrated states in a spatial domain, where the beat signals are generated from interferences between local Rayleigh backscattering signals of the test fiber and local light oscillator. Using the proposed technique, we constructed a standard single-mode fiber based vibration sensor that can have a dynamic range of 12 km and a measurable vibration frequency up to 2 kHz with a spatial resolution of 5 m. Moreover, preliminarily investigation results of two vibration events located at different positions along the test fiber are also reported.

  17. Human vibration perception from single- and dual-frequency components

    NASA Astrophysics Data System (ADS)

    Ljunggren, Fredrik; Wang, Junye; Ågren, Anders

    2007-02-01

    This paper covers three different studies with respect to human perception of vertical vibrations. Although the amplitudes and frequencies throughout the experiments are set to match those that might occur in lightweight floor constructions, the results can be seen as general. A motion simulator generates signals from 5 to 31.5 Hz and the test subjects receive the vibrations sitting on a wooden chair. In the first study, the absolute threshold values from sinusoidal signals are determined. The results agree reasonably well with those found from other similar studies. In study number two, threshold values are determined in the presence of an 8 Hz base component. The threshold values were generally found to be higher than those obtained in the first study, except in the case of 10 Hz which due to beating effect gave an even lower threshold level than when the signal was played alone. The third study is about annoyance from dual sinusoidal vibrations, always including a base signal of 8 Hz at fixed amplitude. In similarity with study two, test persons reported to be more annoyed as the second signal component gets close to the base frequency and, naturally, they also got more annoyed as the amplitude increased.

  18. Modal analysis of dislocation vibration and reaction attempt frequency

    DOE PAGES

    Sobie, Cameron; Capolungo, Laurent; McDowell, David L.; ...

    2017-02-04

    Transition state theory is a fundamental approach for temporal coarse-graining. It estimates the reaction rate for a transition processes by quantifying the activation free energy and attempt frequency for the unit process. To calculate the transition rate of a gliding dislocation, the attempt frequency is often obtained from line tension estimates of dislocation vibrations, a highly simplified model of dislocation behavior. This work revisits the calculation of attempt frequency for a dislocation bypassing an obstacle, in this case a self-interstitial atom (SIA) loop. First, a direct calculation of the vibrational characteristics of a finite pinned dislocation segment is compared tomore » line tension estimates before moving to the more complex case of dislocation-obstacle bypass. The entropic factor associated with the attempt frequency is calculated for a finite dislocation segment and for an infinite glide dislocation interacting with an SIA loop. Lastly, it is found to be dislocation length independent for three cases of dislocation-self interstitial atom (SIA) loop interactions.« less

  19. Frequency-dependence of psychophysical and physiological responses to hand-transmitted vibration.

    PubMed

    Griffin, Michael J

    2012-01-01

    This invited paper reviews experimental studies of the frequency-dependence of absolute thresholds for the perception of vibration, equivalent comfort contours, temporary changes in sensation caused by vibration, and reductions in finger blood flow caused by hand-transmitted vibration. Absolute thresholds depend on the contact conditions but for a typical hand grip the thresholds show greatest sensitivity to acceleration around 125 Hz. The frequency-dependence of discomfort caused by hand-transmitted vibration depends on vibration magnitude: similar to absolute thresholds at low magnitudes, but the discomfort at higher magnitudes is similar when the vibration velocity is similar (at frequencies between about 16 and 400 Hz). Hand-transmitted vibration induces temporary elevations in vibrotactile thresholds that reflect the sensory mechanisms excited by the vibration and are therefore highly dependent on the frequency of vibration. Hand-transmitted vibration reduces finger blood flow during and after exposure; when the vibration velocity is similar at all frequencies there is more vasoconstriction at frequencies greater than 63 Hz than at lower frequencies. A single frequency weighting cannot provide a good indication of how all effects of hand-transmitted vibration depend on vibration frequency. Furthermore, a single frequency weighting provides only an approximate indication of any single response, because many factors influence the frequency-dependence of responses to hand-transmitted vibration, including the magnitude of vibration, contact conditions, and individual differences. Although the frequency weighting in current standards extends from 8 to 1,000 Hz, frequencies greater than 400 Hz rarely increase the weighted value on tools and there is currently little psychophysical or physiological evidence of their effects.

  20. Vibrational sum frequency generation spectroscopy using inverted visible pulses.

    PubMed

    Weeraman, Champika; Mitchell, Steven A; Lausten, Rune; Johnston, Linda J; Stolow, Albert

    2010-05-24

    We present a broadband vibrational sum frequency generation (BB-VSFG) scheme using a novel ps visible pulse shape. We generate the fs IR pulse via standard procedures and simultaneously generate an 'inverted' time-asymmetric narrowband ps visible pulse via second harmonic generation in the pump depletion regime using a very long nonlinear crystal which has high group velocity mismatch (LiNbO3). The 'inverted' ps pulse shape minimally samples the instantaneous nonresonant response but maximally samples the resonant response, maintaining high spectral resolution. We experimentally demonstrate this scheme, presenting SFG spectra of canonical organic monolayer systems in the C-H stretch region (2800-3000 cm(-1)).

  1. The Frequency of Torsional Vibration of a Tapered Beam

    NASA Technical Reports Server (NTRS)

    Coleman, Robert

    1939-01-01

    A solution for the equation of torsional vibration of tapered beams has been found in terms of Bessel functions for beams satisfying the following conditions: (a) the cross sections along the span are similar in shape; and (b) the torsional stiffness of a section can be expressed as a power of a linear function of distance along the span. The method of applying the analysis to actual cases has been described. Charts are given from which numerical values can be immediately obtained for most cases of practical importance. The theoretical values of the frequency ratio have been experimentally checked on five beams having different amounts of taper.

  2. High force vibration testing with wide frequency range

    SciTech Connect

    Romero, Edward F.; Jepsen, Richard A.; Gregory, Danny Lynn

    2013-04-02

    A shaker assembly for vibration testing includes first and second shakers, where the first shaker includes a piezo-electric material for generating vibration. A support structure permits a test object to be supported for vibration of the test object by both shakers. An input permits an external vibration controller to control vibration of the shakers.

  3. A Study on the Vibration Frequency of Blasting Excavation in Highly Stressed Rock Masses

    NASA Astrophysics Data System (ADS)

    Yang, Jianhua; Lu, Wenbo; Jiang, Qinghui; Yao, Chi; Jiang, Shuihua; Tian, Lin

    2016-07-01

    During blasting excavation in deep-buried tunnels and mines characterized by high in situ stress, the rock vibration is attributed not only to blast loading, but also to dynamic unloading caused by transient release of the in situ stress on excavation faces in the process of rock fragmentation by blasting. Understanding the vibration frequency characteristics under these two excitation sources is of important signification to determine appropriate vibration threshold limits for structure damage in deep-buried opening excavations. With a theoretical model developed for a deep-buried circular tunnel excavation by the millisecond delay blasting sequence, frequency characteristics and their influence factors are investigated and discussed for the vibrations induced by the blast loading, the dynamic unloading and the combined effects, respectively. The results show that the rising time of blast loading, the duration of dynamic unloading and the dimension of excavation boundaries are the main factors that affect the vibration frequency of blasting excavation in highly stressed rock masses. It is found that, the blast loading with a much shorter rising time accentuates higher vibration frequency than the dynamic unloading with a long duration, and it causes the blast loading vibration to be more readily attenuated as the propagation distance increases. Thus, the unloading vibration may become the main vibration component at far distances where its low-frequency vibration may exceed the vibration limits. The vibration induced by the combined effects has two distinctly dominant frequency bands corresponding to the two vibration excitation sources. The frequency analyses of the vibration records from two underground projects excavated by blasting are presented to demonstrate this finding. The findings of this study also clearly reveal that, reducing the dimension of excavation boundaries is one of the most effective means to prevent the vibrational damage to structures as it

  4. Vibrational resonances in biological systems at microwave frequencies.

    PubMed Central

    Adair, Robert K

    2002-01-01

    Many biological systems can be expected to exhibit resonance behavior involving the mechanical vibration of system elements. The natural frequencies of such resonances will, generally, be in the microwave frequency range. Some of these systems will be coupled to the electromagnetic field by the charge distributions they carry, thus admitting the possibility that microwave exposures may generate physiological effects in man and other species. However, such microwave excitable resonances are expected to be strongly damped by interaction with their aqueous biological environment. Although those dissipation mechanisms have been studied, the limitations on energy transfers that follow from the limited coupling of these resonances to the electromagnetic field have not generally been considered. We show that this coupling must generally be very small and thus the absorbed energy is so strongly limited that such resonances cannot affect biology significantly even if the systems are much less strongly damped than expected from basic dissipation models. PMID:11867434

  5. Wideband, low-frequency springless vibration energy harvesters: part II

    NASA Astrophysics Data System (ADS)

    Bendame, Mohamed; Abdel-Rahman, Eihab; Soliman, Mostafa

    2016-11-01

    This paper concludes a two-part investigation of a novel architecture for vibration energy harvesting (VEH), the springless VEH. In this part, we study vertical springless electromagnetic VEHs where the direction of motion is aligned with the gravitational field. Experimental results show the existence of three topologies in the response of vertical springless VEHs; linear, single-impact, and double-impact. A model, encompassing all three topologies, was developed and validated by comparison to experimental results. We found that vertical springless VEHs demonstrate low frequency harvesting (<20 Hz), widebeand harvesting (bandwidths up to \\text{BW}=11.2 Hz), and an optimal output power of P  =  7.52 mW at a base acceleration of 0.6 g. While horizontal springless VEHs typically offer more output power, the single-impact regime of the vertical springless VEHs offers the simultaneous advantages of wider harvesting bandwidths at lower operating frequencies.

  6. Vibrational frequencies and structural determinations of 1,4-thioxane

    NASA Astrophysics Data System (ADS)

    Ellzy, Michael W.; Jensen, James O.; Hameka, Hendrik F.; Kay, Jack G.; Zeroka, Daniel

    2001-10-01

    We present a detailed analysis of the structure and infrared spectra of 1,4-thioxane. The vibrational frequencies of the 1,4-thioxane molecule were analyzed using standard quantum chemical techniques. Frequencies were calculated at the MP2 and DFT levels of theory using the standard 6-31G* basis set. The structural transformation of the chemical agent bis (2-chloroethyl) sulfide (HD, mustard gas) and the related symmetry to a previously study compound (4) makes the symmetry of the 1,4-thioxane molecule an interesting candidate for study. The molecule exists normally in a C s configuration similar to the chair form of cyclohexane. High-energy forms of 1,4-thioxane with C 1 and C 2 symmetry also exist.

  7. Vibrational frequencies and structural determinations of di-vinyl sulfone

    NASA Astrophysics Data System (ADS)

    Ellzy, Michael W.; Jensen, James O.; Kay, Jack G.

    2003-03-01

    We present a detailed analysis of the structure and infrared spectra of di-vinyl sulfone. The vibrational frequencies of the di-vinyl sulfone molecule were analyzed using standard quantum chemical techniques. Frequencies were calculated at the MP2 and DFT levels of theory using the standard 6-311G* basis set. The structural transformation of the chemical agent bis(2-chloroehtyl) sulfide (HD, mustard gas) and the related symmetry to a previously study compounds [Spectrochim. Acta Part A 55 (1999) 121; Spectrochim. Acta Part A 57 (2001) 2417] makes the symmetry of the di-vinyl sulfone molecule an interesting candidate for study. The molecule exists normally in a C2 configuration. High-energy forms of di-vinyl sulfone with CS and C1 symmetries also exist.

  8. [Theory study on glycine linear oligopeptide vibrational spectrum frequency shift].

    PubMed

    Ye, Zhi-Peng; Li, Xin; Yang, Meng-Shi; Chen, Liang; Xu, Can; Chu, Xiu-Xiang

    2014-04-01

    By using the density functional theory, glycine linear oligopeptide of different lengths was geometrically optimized on the 6-31G (d) basis set level, their growth processes were simulated, and the average binding energy and vibration frequency were calculated with geometry. The results showed that the average binding energies tend to change in a regular pattern and stabilize with the number of residues increasing; With the oligopeptide chain bond length analysis it was found that the chain to the radial direction there is a opposite trend for chain and radial direction, which is anisotropic. It was found by the IR spectrum analysis that red shifts and blue shifts occur respectively when the same group of peptide bond vibrate, which is anisotropic; These phenomena originate from that quasi one-dimensional nanostructures lead to the anisotropy of the bond length; the induced effects, coupling effects and hydrogen bonding etc. between the same groups lead to the vibration frequency red shifts and blue shifts. The authors conclude that the growth of glycine linear oligopeptide is conducive to stability of the structure, and the authors infer that the oligopeptide has the tendency of self-assembled growth; Through the conformation and spectrum, the authors infer that there is a size effect in physical and chemical properties. The physical and chemical properties of peptide chain end group are extremely stable and unaffected by the impact of the oligopeptide chain length The results are significant to measuring the length and the number of residue of peptide, and to manufacturing the special features oligopeptide chain.

  9. Molecular orbital predictions of the vibrational frequencies of some molecular ions

    NASA Technical Reports Server (NTRS)

    Defrees, D. J.; Mclean, A. D.

    1985-01-01

    The initial detections of IR vibration-rotation bands in polyatomic molecular ions by recent spectroscopic advances were guided by ab initio prediction of vibrational frequencies. The present calculations predict the vibrational frequencies of additional ions which are candidates for laboratory analysis. Neutral molecule vibrational frequencies were computed at three levels of theory and then compared with experimental data; the effect of scaling was also investigated, in order to determine how accurately vibrational frequencies could be predicted. For 92 percent of the frequencies examined, the relatively simple HF/6-31G theory's vibrational frequencies were within 100/cm of experimental values, with a mean absolute error of 49/cm. On this basis, the frequencies of 30 molecular ions (many possessing astrophysical significance) were computed.

  10. Wideband, low-frequency springless vibration energy harvesters: part I

    NASA Astrophysics Data System (ADS)

    Bendame, Mohamed; Abdel-Rahman, Eihab; Soliman, Mostafa

    2016-11-01

    We present a novel architecture for wideband and low-frequency vibration energy harvesting (VEH). Springless vibration energy harvesters (SVEH) employ impact oscillators as energy harvesting elements. A seismic mass moves along a linear guide limited by stoppers at both ends of the track. An electromagnetic transducer converts the kinetic energy captured by the mass into electrical energy. Experiments using prototypes of the horizontal SVEH demonstrated low frequency harvesting (<20 Hz), wideband harvesting (up to 6.0 Hz), and an optimal rectified output power of P  =  12 mW for a base acceleration amplitude of 0.5 g. A model of the electromagnetic SVEH was developed and validated experimentally. A figure of merit was defined to quantify realizable output power in linear and nonlinear VEHs. Comparison using this figure of merit shows that electromagnetic SVEHs outperform their linear counterparts by 92%-232% for acceleration amplitudes in the range of 0.4-0.6 g.

  11. Low-frequency vibration measurement based on camera-projector system

    NASA Astrophysics Data System (ADS)

    Lyu, Chengang; Liu, Yuxiang; Gao, Shuang; Bao, Zhiqiang; Chang, Yuqing; Gao, Jiale; Yang, Jiachen; Jin, Jie

    2017-09-01

    A low-frequency vibration measurement based on a camera-projector system is proposed and verified by experiment at several hertz. A CCD camera gathered deformed fringes modulated by a vibrating trumpet at a constant sampling rate. Information on amplitude and frequency are contained in a series of observed images. The height value of each pixel point in the image can be restored by using Fourier transform profilometry. Connecting the height value of every sampling frame into a motion trajectory, the frequency and amplitude of the vibrating object can be obtained from the trajectory curve. The experiment restored the vibration process of a trumpet in half a cycle while the vibrating frequency was 3 Hz. Subsequently, the measurement of different frequencies and different amplitudes are comparatively studied. The results show that slight vibration at 35 µm and above can be detected by the system, which confirms the feasibility of the proposed system in the field of industrial vibration measurement.

  12. Distributed measurement of acoustic vibration location with frequency multiplexed phase-OTDR

    NASA Astrophysics Data System (ADS)

    Iida, Daisuke; Toge, Kunihiro; Manabe, Tetsuya

    2017-07-01

    All-fiber distributed vibration sensing is attracting attention in relation to structural health monitoring because it is cost effective, offers high coverage of the monitored area and can detect various structural problems. And in particular the demand for high-speed vibration sensing operating at more than 10 kHz has increased because high frequency vibration indicates high energy and severe trouble in the monitored object. Optical fiber vibration sensing with phase-sensitive optical time domain reflectometry (phase-OTDR) has long been studied because it can be used for distributed vibration sensing in optical fiber. However, pulse reflectometry such as OTDR cannot measure high-frequency vibration whose cycle is shorter than the repetition time of the OTDR. That is, the maximum detectable frequency depends on fiber length. In this paper, we describe a vibration sensing technique with frequency-multiplexed OTDR that can detect the entire distribution of a high-frequency vibration thus allowing us to locate a high-speed vibration point. We can measure the position, frequency and dynamic change of a high-frequency vibration whose cycle is shorter than the repetition time. Both frequency and position are visualized simultaneously for a 5-km fiber with an 80-kHz frequency response and a 20-m spatial resolution.

  13. Piezoelectric energy harvesting devices for low frequency vibration applications

    NASA Astrophysics Data System (ADS)

    Shen, Dongna

    Energy harvesting, a process of capturing ambient waste energy and converting it into usable electricity, has been attracting more and more researchers' interest because of the limitations of traditional power sources, the increasing demands upon mobile devices such as wireless sensor networks, and the recent advent of the extremely low power electrical and mechanical devices such as microelectromechanical systems (MEMS). In this research, bulk- and wafer-scale of piezoelectric power generator prototypes were developed. The Lead Zirconate Titanate (PZT) bimorph cantilever in bulk scale with a big proof mass at the free end tip was studied to convert ambient vibration energy of 100 Hz and above 1g (1g = 9.81 m/s2) acceleration amplitudes. The optimal design was based on matching the resonant frequency of the device with the environmental exciting frequency, and balancing the power output and the fracture safety factor. The fabricated PZT power generator with an effective volume of 0.0564 cm3 and a safety factor of 10g can produce 6.21 Vpk, 257 microW, or 4558 microW/cm 3 with an optimal resistive load of 75 kO from 1g acceleration at its resonant frequency of 97.6 Hz. To overcome the high fragility of PZT, substitute piezoelectric materials, Macro Fiber Composite (MFC) and polyvinylidene fluoride (PVDF), and alternative operational ambient for power generators were investigated for high vibration amplitude applications. Before fabricating piezoelectric power generators in wafer scale, interlayer effects on the properties of PZT thin film were surveyed. The fabricated device based on Si wafer, with a beam dimension about 4.800 mm x 0.400 mm x 0.036 mm and an integrated Si mass dimension about 1.360 mm x 0.940 mm x 0.456 mm produced 160 mVpk, 2.13 microW, or 3272 microW/cm3 with the optimal resistive load of 6 kO from 2g acceleration at its resonant frequency of 461.15 Hz. To precisely control the resonant frequency of the power generator, Si on insulator (SOI) wafer

  14. Deviations of frequency and the mode of vibration of commercially available whole-body vibration training devices.

    PubMed

    Kaeding, T S

    2015-06-01

    Research in the field of whole body vibration (WBV) training and the use of it in practice might be hindered by the fact that WBV training devices generate and transmit frequencies and/or modes of vibration which are different to preset adjustments. This research project shall clarify how exact WBV devices apply the by manufacturer information promised preset frequency and mode of vibration. Nine professional devices for WBV training were tested by means of a tri-axial accelerometer. The accelerations of each device were recorded under different settings with a tri-axial accelerometer. Beneath the measurement of different combinations of preset frequency and amplitude the repeatability across 3 successive measurements with the same preset conditions and one measurement under loaded condition were carried out. With 3 exceptions (both Board 3000 & srt medical PRO) we did not find noteworthy divergences between preset and actual applied frequencies. In these 3 devices we found divergences near -25%. Loading the devices did not affect the applied frequency or mode of vibration. There were no important divergences measurable for the applied frequency and mode of vibration regarding repeatability. The results of our measurements cannot be generalized as we only measured one respectively at most two devices of one model in terms of a random sample. Based on these results we strongly recommend that user in practice and research should analyse their WBV training devices regarding applied frequency and mode of vibration.

  15. Smart nanocoated structure for energy harvesting at low frequency vibration

    NASA Astrophysics Data System (ADS)

    Sharma, Sudhanshu

    Increasing demands of energy which is cleaner and has an unlimited supply has led development in the field of energy harvesting. Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can be stored and used to power other devices. With the recent surge of micro scale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources. In this research, a piezoelectric power generator composite prototype was developed to maximize the power output of the system. A lead zirconate titanate (PZT) composite structure was formed and mounted on a cantilever bar and was studied to convert vibration energy of the low range vibrations at 30 Hz--1000 Hz. To improve the performance of the PZT, different coatings were made using different percentage of Ferrofluid (FNP) and Zinc Oxide nanoparticles (ZnO) and binder resin. The optimal coating mixture constituent percentage was based on the performance of the composite structure formed by applying the coating on the PZT. The fabricated PZT power generator composite with an effective volume of 0.062 cm3 produced a maximum of 44.5 μW, or 0.717mW/cm3 at its resonant frequency of 90 Hz. The optimal coating mixture had the composition of 59.9%FNP + 40% ZnO + 1% Resin Binder. The coating utilizes the opto-magneto-electrical properties of ZnO and Magnetic properties of FNP. To further enhance the output, the magneto-electric (ME) effect was increased by subjecting the composite to magnetic field where coating acts as a magnetostrictive material. For the effective volume of 0.0062 cm 3, the composite produced a maximum of 68.5 μW, or 1.11mW/cm 3 at its resonant frequency of 90 Hz at 160 gauss. The optimal coating mixture had the composition of 59.9% FNP + 40% ZnO + 1% Resin Binder. This research also focused on improving the efficiency of solar cells by utilizing the magnetic effect along with gas plasma etching to improve the internal reflection

  16. Fundamental Study on the Effect of High Frequency Vibration on Ride Comfort

    NASA Astrophysics Data System (ADS)

    Nakagawa, Chizuru; Shimamune, Ryohei; Watanabe, Ken; Suzuki, Erimitsu

    To develop a more suitable method of evaluating ride comfort of high speed trains, a fundamental study was conducted on sensitivity of passengers to various frequencies of vibration with respect to ride comfort. Experiments were performed on 55 subjects using an electrodynamic vibration system that can generate vibrations in the frequency range of 1 to 80 Hz in the vertical direction. Results of experiments indicated that the subjects tend to experience greater discomfort when exposed to high frequency vibrations than that presumed by the conventional Japanese ride comfort assessment method, the "Ride Comfort Level."

  17. Characteristics in Molecular Vibrational Frequency Patterns between Agonists and Antagonists of Histamine Receptors.

    PubMed

    Oh, S June

    2012-06-01

    To learn the differences between the structure-activity relationship and molecular vibration-activity relationship in the ligand-receptor interaction of the histamine receptor, 47 ligands of the histamine receptor were analyzed by structural similarity and molecular vibrational frequency patterns. The radial tree that was produced by clustering analysis of molecular vibrational frequency patterns shows its potential for the functional classification of histamine receptor ligands.

  18. Characteristics in Molecular Vibrational Frequency Patterns between Agonists and Antagonists of Histamine Receptors

    PubMed Central

    2012-01-01

    To learn the differences between the structure-activity relationship and molecular vibration-activity relationship in the ligand-receptor interaction of the histamine receptor, 47 ligands of the histamine receptor were analyzed by structural similarity and molecular vibrational frequency patterns. The radial tree that was produced by clustering analysis of molecular vibrational frequency patterns shows its potential for the functional classification of histamine receptor ligands. PMID:23105941

  19. Micro-scale piezoelectric vibration energy harvesting: From fixed-frequency to adaptable-frequency devices

    NASA Astrophysics Data System (ADS)

    Miller, Lindsay Margaret

    hundred milliwatts and are falling steadily as improvements are made, it is feasible to use energy harvesting to power WSNs. This research begins by presenting the results of a thorough survey of ambient vibrations in the machine room of a large campus building, which found that ambient vibrations are low frequency, low amplitude, time varying, and multi-frequency. The modeling and design of fixed-frequency micro scale energy harvesters are then presented. The model is able to take into account rotational inertia of the harvester's proof mass and it accepts arbitrary measured acceleration input, calculating the energy harvester's voltage as an output. The fabrication of the micro electromechanical system (MEMS) energy harvesters is discussed and results of the devices harvesting energy from ambient vibrations are presented. The harvesters had resonance frequencies ranging from 31 - 232 Hz, which was the lowest reported in literature for a MEMS device, and produced 24 pW/g2 - 10 nW/g2 of harvested power from ambient vibrations. A novel method for frequency modification of the released harvester devices using a dispenser printed mass is then presented, demonstrating a frequency shift of 20 Hz. Optimization of the MEMS energy harvester connected to a resistive load is then presented, finding that the harvested power output can be increased to several microwatts with the optimized design as long as the driving frequency matches the harvester's resonance frequency. A framework is then presented to allow a similar optimization to be conducted with the harvester connected to a synchronously switched pre-bias circuit. With the realization that the optimized energy harvester only produces usable amounts of power if the resonance frequency and driving frequency match, which is an unrealistic situation in the case of ambient vibrations which change over time and are not always known a priori, an adaptable-frequency energy harvester was designed. The adaptable-frequency

  20. Evaluation of influences of frequency and amplitude on image degradation caused by satellite vibrations

    NASA Astrophysics Data System (ADS)

    Nan, Yi-Bing; Tang, Yi; Zhang, Li-Jun; Zheng, Cheng; Wang, Jing

    2015-05-01

    Satellite vibrations during exposure will lead to pixel aliasing of remote sensors, resulting in the deterioration of image quality. In this paper, we expose the problem and discuss the characteristics of satellite vibrations, and then present a pixel mixing model. The idea of mean mixing ratio (MMR) is proposed. MMR computations for different frequencies are implemented. In the mixing model, a coefficient matrix is introduced to estimate each mixed pixel. Thus, the simulation of degraded image can be performed when the vibration attitudes are known. The computation of MMR takes into consideration the influences of various frequencies and amplitudes. Therefore, the roles of these parameters played in the degradation progress are identified. Computations show that under the same vibration amplitude, the influence of vibrations fluctuates with the variation of frequency. The fluctuation becomes smaller as the frequency rises. Two kinds of vibration imaging experiments are performed: different amplitudes with the same frequency and different frequencies with the same amplitude. Results are found to be in very good agreement with the theoretical results. MMR has a better description of image quality than modulation transfer function (MTF). The influence of vibrations is determined mainly by the amplitude rather than the frequency. The influence of vibrations on image quality becomes gradually stable with the increase of frequency. Project supported by the National Basic Research Program of China (Grant No. 2013CB329202) and the Basic Industrial Technology Project of China (Grant No. J312012B002).

  1. Suppression of the Leidenfrost effect via low frequency vibrations.

    PubMed

    Ng, Boon T; Hung, Yew M; Tan, Ming K

    2015-01-28

    The ability to suppress the Leidenfrost effect is of significant importance in applications that require rapid and efficient cooling of surfaces with temperature higher than the Leidenfrost point TSL. The Leidenfrost effect will result in substantial reduction in cooling efficiency and hence there have been a few different approaches to suppress the Leidenfrost effect. The majority of these approaches relies on fabricating micro/nano-structures on heated surfaces, others rely on inducing an electric field between the droplets and the heated surfaces. In this paper, we present an approach that induces low frequency vibrations (f∼10(2) Hz) on a heated surface to suppress the effect. By mapping the different magnitudes of surface acceleration [greek xi with two dots above]sversus different initial surface temperatures Ts of the substrate, three regimes that represent three distinct impact dynamics are analyzed. Regime-I represents gentle film boiling ([greek xi with two dots above]s∼10(2) m s(-2) and Ts∼TSL), which is associated with the formation of thin spreading lamella around the periphery of the impinged droplet; Regime-II ([greek xi with two dots above]s∼10(2) m s(-2) and Ts>TSL) represents film boiling, which is associated with the rebound of the impinged droplet due to the presence of a thick vapor layer; Regime-III ([greek xi with two dots above]s∼10(3) m s(-2) and Ts∼TSL) represents contact boiling, which is associated with the ejection of tiny droplets due to the direct contact between the droplet and the heated surface. The estimated cooling enhancement for Regime-I is between 10% and 95%, Regime-II is between 5% and 15%, and Regime-III is between 95% and 105%. The improvement in cooling enhancement between Regime-I (strong Leidenfrost effect) and Regime-III (suppressed Leidenfrost effect) is more than 80%, demonstrating the effectiveness of using low frequency vibrations to suppress the Leidenfrost effect.

  2. Examining the impact of harmonic correlation on vibrational frequencies calculated in localized coordinates

    SciTech Connect

    Hanson-Heine, Magnus W. D.

    2015-10-28

    Carefully choosing a set of optimized coordinates for performing vibrational frequency calculations can significantly reduce the anharmonic correlation energy from the self-consistent field treatment of molecular vibrations. However, moving away from normal coordinates also introduces an additional source of correlation energy arising from mode-coupling at the harmonic level. The impact of this new component of the vibrational energy is examined for a range of molecules, and a method is proposed for correcting the resulting self-consistent field frequencies by adding the full coupling energy from connected pairs of harmonic and pseudoharmonic modes, termed vibrational self-consistent field (harmonic correlation). This approach is found to lift the vibrational degeneracies arising from coordinate optimization and provides better agreement with experimental and benchmark frequencies than uncorrected vibrational self-consistent field theory without relying on traditional correlated methods.

  3. Bioparticles assembled using low frequency vibration immune to evacuation drifts.

    PubMed

    Shao, Fenfen; Whitehill, James David; Ng, Tuck Wah

    2012-08-01

    The use of low frequency vibration on suspensions of glass beads in a droplet has been shown to develop a strong degree of patterning (to a ring) due to the manner with which the surface waves are modified. Functionalized glass beads that serve as bioparticles permit for sensitive readings when concentrated at specific locations. However, a time controlled exposure with analytes is desirable. The replacement of the liquid medium with analyte through extraction is needed to conserve time. Nevertheless, we show here that extraction with a porous media, which is simple and useable in the field, will strongly displace the patterned beads. The liquid removal was found to be dependent on two mechanisms that affect the shape of the droplet, one of contact hysteresis due to the outer edge pinning, and the other of liquid being drawn into the porous media. From this, we developed and demonstrated a modified well structure that prevented micro-bead displacement during evacuation. An added strong advantage with this approach lies with its ability to require only analytes to be dispensed at the location of aggregated particles, which minimizes analyte usage. This was analytically established here.

  4. Suppression of Leidenfrost effect via low frequency vibrations

    NASA Astrophysics Data System (ADS)

    Ng, Boon Thiam; Hung, Yew Mun; Tan, Ming Kwang

    2015-11-01

    Leidenfrost effect occurs when vapor layer forms in between the coolant and the hot surface above Leidenfrost point, which dramatically reduces the cooling efficiency due to low thermal conductivity of the vapor layer. To prevent surface overheating, there have been number of reported methods to suppress the Leidenfrost effect that were mainly based on functionalization of the substrate surface and application of electric field across the droplet and substrate. In this work, we induce low frequency vibrations (f ~ 100 Hz) to the heated substrate to suppress the Leidenfrost effect. Three distinct impact dynamics are observed based on different magnitudes of surface acceleration and surface temperature. In gentle film boiling regime, formation of thin spreading lamella around the periphery of the impinged droplet is observed; in film boiling regime, due to thicker vapor cushion, rebound of the impinged droplet is observed; in contact boiling regime, due to the direct contact between the impinged droplet and heated substrate, ejection of the tiny droplet is observed. Also, estimated cooling enhancement ratio for contact boiling regime shows an improvement from 95% to 105%.

  5. Investigating buried polymer interfaces using sum frequency generation vibrational spectroscopy

    PubMed Central

    Chen, Zhan

    2010-01-01

    This paper reviews recent progress in the studies of buried polymer interfaces using sum frequency generation (SFG) vibrational spectroscopy. Both buried solid/liquid and solid/solid interfaces involving polymeric materials are discussed. SFG studies of polymer/water interfaces show that different polymers exhibit varied surface restructuring behavior in water, indicating the importance of probing polymer/water interfaces in situ. SFG has also been applied to the investigation of interfaces between polymers and other liquids. It has been found that molecular interactions at such polymer/liquid interfaces dictate interfacial polymer structures. The molecular structures of silane molecules, which are widely used as adhesion promoters, have been investigated using SFG at buried polymer/silane and polymer/polymer interfaces, providing molecular-level understanding of polymer adhesion promotion. The molecular structures of polymer/solid interfaces have been examined using SFG with several different experimental geometries. These results have provided molecular-level information about polymer friction, adhesion, interfacial chemical reactions, interfacial electronic properties, and the structure of layer-by-layer deposited polymers. Such research has demonstrated that SFG is a powerful tool to probe buried interfaces involving polymeric materials, which are difficult to study by conventional surface sensitive analytical techniques. PMID:21113334

  6. Diborane, dialane, and digallane: Accurate geometries and vibrational frequencies

    SciTech Connect

    Magers, D.H.; Hood, R.B.; Leszczynski, J.

    1994-12-31

    Optimum equilibrium geometries, harmonic vibrational frequencies, and infrared intensities within the double harmonic approximation are computed for diborane, B{sub 2}H{sub 6}, dialane, Al{sub 2}H{sub 6}, and digallane, Ga{sub 2}H{sub 6}, at both the SCF level of theory and the second-order perturbation theory [E(2)] using three large basis sets: 6-311G(d,p), 6-311G(2d,2p), and 6-311G(2df,2p). In particular, the results obtained with the latter basis set make this present work the first study to include f-type polarization functions in a systematic investigation of the molecular structure and properties of all three molecules in the series. Because of the good agreement of the present theoretical results with experimental data and with previous theoretical studies which employed a higher treatment of electron correlation, this study serves to show that large basis sets can in part compensate for the lack of a more advanced treatment of electron correlation in these electron-deficient systems. In addition, this study establishes the level of basis set needed for future work on these systems including a thorough description of the total electronic density at a correlated level.

  7. Frequency-dependent Effects of Vibration on Physiological Systems: Experiments with Animals and other Human Surrogates

    PubMed Central

    KRAJNAK, Kristine; RILEY, Danny A.; WU, John; MCDOWELL, Thomas; WELCOME, Daniel E.; XU, Xueyan S.; DONG, Ren G.

    2015-01-01

    Occupational exposure to vibration through the use of power- and pneumatic hand-tools results in cold-induced vasospasms, finger blanching, and alterations in sensorineural function. Collectively, these symptoms are referred to as hand-arm vibration syndrome (HAVS). Currently the International Standards Organization (ISO) standard ISO 5349-1 contains a frequency-weighting curve to help workers and employers predict the risk of developing HAVS with exposure to vibration of different frequencies. However, recent epidemiological and experimental evidence suggests that this curve under-represents the risk of injuries to the hands and fingers induced by exposure to vibration at higher frequencies (>100 Hz). To improve the curve, better exposure-response data need to be collected. The goal of this review is to summarize the results of animal and computational modeling studies that have examined the frequency-dependent effects of vibration, and discuss where additional research would be beneficial to fill these research gaps. PMID:23060248

  8. A broadband frequency-tunable dynamic absorber for the vibration control of structures

    NASA Astrophysics Data System (ADS)

    Komatsuzaki, T.; Inoue, T.; Terashima, O.

    2016-09-01

    A passive-type dynamic vibration absorber (DVA) is basically a mass-spring system that suppresses the vibration of a structure at a particular frequency. Since the natural frequency of the DVA is usually tuned to a frequency of particular excitation, the DVA is especially effective when the excitation frequency is close to the natural frequency of the structure. Fixing the physical properties of the DVA limits the application to a narrowband, harmonically excited vibration problem. A frequency-tunable DVA that can modulate its stiffness provides adaptability to the vibration control device against non-stationary disturbances. In this paper, we suggest a broadband frequency-tunable DVA whose natural frequency can be extended by 300% to the nominal value using the magnetorheological elastomers (MREs). The frequency adjustability of the proposed absorber is first shown. The real-time vibration control performance of the frequency-tunable absorber for an acoustically excited plate having multiple resonant peaks is then evaluated. Investigations show that the vibration of the structure can be effectively reduced with an improved performance by the DVA in comparison to the conventional passive- type absorber.

  9. Active low-frequency vertical vibration isolation system for precision measurements

    NASA Astrophysics Data System (ADS)

    Wu, Kang; Li, Gang; Hu, Hua; Wang, Lijun

    2017-01-01

    Low-frequency vertical vibration isolation systems play important roles in precision measurements to reduce seismic and environmental vibration noise. Several types of active vibration isolation systems have been developed. However, few researches focus on how to optimize the test mass install position in order to improve the vibration transmissibility. An active low-frequency vertical vibration isolation system based on an earlier instrument, the Super Spring, is designed and implemented. The system, which is simple and compact, consists of two stages: a parallelogram-shaped linkage to ensure vertical motion, and a simple spring-mass system. The theoretical analysis of the vibration isolation system is presented, including terms erroneously ignored before. By carefully choosing the mechanical parameters according to the above analysis and using feedback control, the resonance frequency of the system is reduced from 2.3 to 0.03 Hz, a reduction by a factor of more than 75. The vibration isolation system is installed as an inertial reference in an absolute gravimeter, where it improved the scatter of the absolute gravity values by a factor of 5. The experimental results verifies the improved performance of the isolation system, making it particularly suitable for precision experiments. The improved vertical vibration isolation system can be used as a prototype for designing high-performance active vertical isolation systems. An improved theoretical model of this active vibration isolation system with beam-pivot configuration is proposed, providing fundamental guidelines for vibration isolator design and assembling.

  10. Trunk isometric force production parameters during erector spinae muscle vibration at different frequencies

    PubMed Central

    2013-01-01

    Background Vibration is known to alter proprioceptive afferents and create a tonic vibration reflex. The control of force and its variability are often considered determinants of motor performance and neuromuscular control. However, the effect of vibration on paraspinal muscle control and force production remains to be determined. Methods Twenty-one healthy adults were asked to perform isometric trunk flexion and extension torque at 60% of their maximal voluntary isometric contraction, under three different vibration conditions: no vibration, vibration frequencies of 30 Hz and 80 Hz. Eighteen isometric contractions were performed under each condition without any feedback. Mechanical vibrations were applied bilaterally over the lumbar erector spinae muscles while participants were in neutral standing position. Time to peak torque (TPT), variable error (VE) as well as constant error (CE) and absolute error (AE) in peak torque were calculated and compared between conditions. Results The main finding suggests that erector spinae muscle vibration significantly decreases the accuracy in a trunk extension isometric force reproduction task. There was no difference between both vibration frequencies with regard to force production parameters. Antagonist muscles do not seem to be directly affected by vibration stimulation when performing a trunk isometric task. Conclusions The results suggest that acute erector spinae muscle vibration interferes with torque generation sequence of the trunk by distorting proprioceptive information in healthy participants. PMID:23919578

  11. Numerical Analysis of the Influence of Low Frequency Vibration on Bubble Growth

    PubMed Central

    Han, D.; Kedzierski, Mark A.

    2017-01-01

    Numerical simulation of bubble growth during pool boiling under the influence of low frequency vibration was performed to understand the influence of common vibrations such as those induced by wind, highway transportation, and nearby mechanical devices on the performance of thermal systems that rely on boiling. The simulations were done for saturated R123 boiling at 277.6 K with a 15 K wall superheat. The numerical volume-of-fluid method (fixed grid) was used to define the liquid-vapor interface. The basic bubble growth characteristics including the bubble departure diameter and the bubble departure time were determined as a function of the bubble contact angle (20°–80°), the vibration displacement (10 µm–50 µm), the vibration frequency (5 Hz–25 Hz), and the initial vibration direction (positive or negative). The bubble parameters were shown to be strongly dependent on the bubble contact angle at the surface. For example, both the bubble departure diameter and the bubble departure time increased with the contact angle. At the same vibration frequency and the initial vibration direction, the bubble departure diameter and the bubble departure time both decreased with increasing vibration displacement. In addition, the vibration frequency had a greater effect on the bubble growth characteristics than did the vibration displacement. The vibration frequency effect was strongly influenced by the initial vibration direction. The pressure contour, the volume fraction of vapor phase, the temperature profile, and the velocity vector were investigated to understand these dynamic bubble behaviors. The limitation of the computational fluid dynamics approach was also described. PMID:28747812

  12. Numerical Analysis of the Influence of Low Frequency Vibration on Bubble Growth.

    PubMed

    Han, D; Kedzierski, Mark A

    2017-01-01

    Numerical simulation of bubble growth during pool boiling under the influence of low frequency vibration was performed to understand the influence of common vibrations such as those induced by wind, highway transportation, and nearby mechanical devices on the performance of thermal systems that rely on boiling. The simulations were done for saturated R123 boiling at 277.6 K with a 15 K wall superheat. The numerical volume-of-fluid method (fixed grid) was used to define the liquid-vapor interface. The basic bubble growth characteristics including the bubble departure diameter and the bubble departure time were determined as a function of the bubble contact angle (20°-80°), the vibration displacement (10 µm-50 µm), the vibration frequency (5 Hz-25 Hz), and the initial vibration direction (positive or negative). The bubble parameters were shown to be strongly dependent on the bubble contact angle at the surface. For example, both the bubble departure diameter and the bubble departure time increased with the contact angle. At the same vibration frequency and the initial vibration direction, the bubble departure diameter and the bubble departure time both decreased with increasing vibration displacement. In addition, the vibration frequency had a greater effect on the bubble growth characteristics than did the vibration displacement. The vibration frequency effect was strongly influenced by the initial vibration direction. The pressure contour, the volume fraction of vapor phase, the temperature profile, and the velocity vector were investigated to understand these dynamic bubble behaviors. The limitation of the computational fluid dynamics approach was also described.

  13. Determining the Posture and Vibration Frequency that Maximize Pelvic Floor Muscle Activity During Whole-Body Vibration

    PubMed Central

    Lee, Juhyun; Lee, Kyeongjin; Song, Changho

    2016-01-01

    Background The aim of this study was to investigate the electromyogram (EMG) response of pelvic floor muscle (PFM) to whole-body vibration (WBV) while using different body posture and vibration frequencies. Material/Methods Thirteen healthy adults (7 men, 6 women) voluntarily participated in this cross-sectional study in which EMG data from PFM were collected in a total of 12 trials for each subject (4 body postures, 3 vibration frequencies). Pelvic floor EMG activity was recorded using an anal probe. The rating of perceived exertion (RPE) was assessed with a modified Borg scale. Results We found that vibration frequency, body posture, and muscle stimulated had a significant effect on the EMG response. The PFM had high activation at 12 Hz and 26 Hz (p<0.05). PFM activation significantly increased with knee flexion (p<0.05). The RPE significantly increased with increased frequency (p<0.05). Conclusions The knee flexion angle of 40° at 12 Hz frequency can be readily promoted in improving muscle activation during WBV, and exercise would be performed effectively. Based on the results of the present investigation, sports trainers and physiotherapists may be able to optimize PFM training programs involving WBV. PMID:27787476

  14. Low-frequency wideband vibration energy harvesting by using frequency up-conversion and quin-stable nonlinearity

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Zhang, Qichang; Wang, Wei

    2017-07-01

    This work presents models and experiments of an impact-driven and frequency up-converted wideband piezoelectric-based vibration energy harvester with a quintuple-well potential induced by the combination effect of magnetic nonlinearity and mechanical piecewise-linearity. Analysis shows that the interwell motions during coupled vibration period enable to increase electrical power output in comparison to conventional frequency up-conversion technology. Besides, the quintuple-well potential with shallower potential wells could extend the harvester's operating bandwidth to lower frequencies. Experiments demonstrate our proposed approach can dramatically boost the measured power of the energy harvester as much as 35 times while its lower cut-off frequency is two times lower than that of a conventional counterpart. These results reveal our proposed approach shows promise for powering portable wireless smart devices from low-intensity, low-frequency vibration sources.

  15. Older Age Is Associated with Lower Optimal Vibration Frequency in Lower-Limb Muscles During Whole-Body Vibration.

    PubMed

    Carlucci, Flaminia; Orlando, Giorgio; Haxhi, Jonida; Laudani, Luca; Giombini, Arrigo; Macaluso, Andrea; Pigozzi, Fabio; Sacchetti, Massimo

    2015-07-01

    The aim of this study was to compare the optimal vibration frequency (OVF), which corresponds to maximal electromyographic muscle response during whole-body vibration, between young, middle-aged, and older women in four muscles of the lower-limbs. OVF was measured as the frequency corresponding to maximal root mean square of the surface electromyogram (RMSmax) during a continuous incremental protocol, with a succession of vibration frequencies from 20 to 55 Hz (A = 2 mm), on the vastus lateralis, vastus medialis, rectus femoris, and gastrocnemius lateralis muscles of the dominant lower-limb. Seventy-eight women were divided into three age groups, that is, young, 21.6 ± 2.4 yrs; middle aged, 43.0 ± 5.2 yrs; and older, 74.2 ± 6.0 yrs. OVF in the vastus medialis was lower in the older women than in the middle-aged and young women, whereas OVF in the vastus lateralis was lower in the older than in the young women. There were no differences in OVF between muscles within each group. RMSmax was higher in the older than in the young women in all muscles. Age range should be taken into consideration when determining OVF because it decreases with age. Properly individualizing the vibration protocol might greatly influence neuromuscular effects of vibration training.

  16. Separate recording of rationally related vibration frequencies using digital stroboscopic holographic interferometry

    SciTech Connect

    Alexeenko, Igor; Gusev, Michael; Gurevich, Vadim

    2009-06-20

    A method for separate recording of rationally related vibration frequencies is presented. To record and measure the mode shape of vibrations, a synchronized stroboscopic CCD camera is used. Synchronization and control of the camera acquisition for recording stroboscopic holographic sequence has been realized. The phase for different states of the object vibration is calculated using the Fourier-transform method. Experimental results are presented, and the advantages and disadvantages of the proposed method are discussed.

  17. A new adaptive resonance frequency of piezoelectric components used for vibration damping

    PubMed Central

    Faiz, A.; Petit, L.; Guyomar, D.; Ducourneau, J.

    2010-01-01

    This paper describes two methods for vibration damping in a broad band frequency range using a piezoelectric patch. The first method, applied to an adaptive device, uses a bias (static voltage control), which applies stresses or releases stresses in a piezoelectric component to modify its mechanical characteristics and thereby its resonance frequency. The second method is based on a semipassive approach [synchronized switch damping (SSD)], developed to control structural vibration damping using a piezoelectric component. Attenuations of 10 and 4.8 dB in vibration velocity have been obtained using the adaptive frequency and SSD methods. PMID:20369980

  18. Characterization of Frequency-Dependent Responses of the Vascular System to Repetitive Vibration

    PubMed Central

    Krajnak, Kristine; Miller, G. Roger; Waugh, Stacey; Johnson, Claud; Kashon, Michael L.

    2015-01-01

    Objective Occupational exposure to hand-transmitted vibration can result in damage to nerves and sensory loss. The goal of this study was to assess the frequency-dependent effects of repeated bouts of vibration on sensory nerve function and associated changes in nerves. Methods The tails of rats were exposed to vibration at 62.5, 125, or 250 Hz (constant acceleration of 49m/s2) for 10 days. The effects on sensory nerve function, nerve morphology, and transcript expression in ventral tail nerves were measured. Results Vibration at all frequencies had effects on nerve function and physiology. However, the effects tended to be more prominent with exposure at 250 Hz. Conclusion Exposure to vibration has detrimental effects on sensory nerve function and physiology. However, many of these changes are more prominent at 250-Hz exposure than at lower frequencies. PMID:22785326

  19. Low Frequency Vibrations Disrupt Left-Right Patterning in the Xenopus Embryo

    PubMed Central

    Vandenberg, Laura N.; Pennarola, Brian W.; Levin, Michael

    2011-01-01

    The development of consistent left-right (LR) asymmetry across phyla is a fascinating question in biology. While many pharmacological and molecular approaches have been used to explore molecular mechanisms, it has proven difficult to exert precise temporal control over functional perturbations. Here, we took advantage of acoustical vibration to disrupt LR patterning in Xenopus embryos during tightly-circumscribed periods of development. Exposure to several low frequencies induced specific randomization of three internal organs (heterotaxia). Investigating one frequency (7 Hz), we found two discrete periods of sensitivity to vibration; during the first period, vibration affected the same LR pathway as nocodazole, while during the second period, vibration affected the integrity of the epithelial barrier; both are required for normal LR patterning. Our results indicate that low frequency vibrations disrupt two steps in the early LR pathway: the orientation of the LR axis with the other two axes, and the amplification/restriction of downstream LR signals to asymmetric organs. PMID:21826245

  20. Electromyographic assessment of muscle fatigue during isometric vibration training at varying frequencies.

    PubMed

    Mischi, M; Rabotti, C; Cardinale, M

    2010-01-01

    Resistance exercise is essential to improve or maintain muscle performance. Vibration training has been suggested as an alternative option for muscle conditioning, aiming especially at improving muscle strength and power. Several studies link the effects of vibration training to enhanced neuromuscular stimulation, measured by electromyography (EMG) and typically ascribed to involuntary reflex mechanisms. However, the underlying mechanisms are still unclear, limiting the use of vibration training. This paper proposes additional methods to analyze the mechanisms involved in vibration training. A dedicated measurement setup was realized to relate vibration parameters to muscle fatigue in the biceps brachii. Fatigue is estimated by EMG mean frequency and conduction velocity assessments as well as by maximum voluntary contraction (MVC) force measurements. A modified maximum likelihood algorithm is proposed for the conduction velocity estimation based on high-density EMG recording. Five volunteers performed four isometric contractions of 50 s at 80% MVC with no vibration (control) and with superimposed vibration at 20, 30, and 40 Hz. Fatigue was estimated from the decay of force, EMG mean frequency, and EMG conduction velocity. 30-Hz vibrations represented the most fatiguing stimulus. Our preliminary results also show a better correlation between force and conduction velocity decay than between force and mean frequency decay, indicating the former as a better EMG indicator of fatigue. The proposed methods provide important advancements for the analysis of vibration exercise and guidance towards the definition of optimal training protocols.

  1. Effects of Frequency and Acceleration Amplitude on Osteoblast Mechanical Vibration Responses: A Finite Element Study

    PubMed Central

    Hsu, Hung-Yao

    2016-01-01

    Bone cells are deformed according to mechanical stimulation they receive and their mechanical characteristics. However, how osteoblasts are affected by mechanical vibration frequency and acceleration amplitude remains unclear. By developing 3D osteoblast finite element (FE) models, this study investigated the effect of cell shapes on vibration characteristics and effect of acceleration (vibration intensity) on vibrational responses of cultured osteoblasts. Firstly, the developed FE models predicted natural frequencies of osteoblasts within 6.85–48.69 Hz. Then, three different levels of acceleration of base excitation were selected (0.5, 1, and 2 g) to simulate vibrational responses, and acceleration of base excitation was found to have no influence on natural frequencies of osteoblasts. However, vibration response values of displacement, stress, and strain increased with the increase of acceleration. Finally, stress and stress distributions of osteoblast models under 0.5 g acceleration in Z-direction were investigated further. It was revealed that resonance frequencies can be a monotonic function of cell height or bottom area when cell volumes and material properties were assumed as constants. These findings will be useful in understanding how forces are transferred and influence osteoblast mechanical responses during vibrations and in providing guidance for cell culture and external vibration loading in experimental and clinical osteogenesis studies. PMID:28074178

  2. A Proposed Theory on Biodynamic Frequency Weighting for Hand-Transmitted Vibration Exposure

    PubMed Central

    DONG, Ren G.; WELCOME, Daniel E.; MCDOWELL, Thomas W.; XU, Xueyan S.; KRAJNAK, Kristine; WU, John Z.

    2015-01-01

    The objective of this study is to propose a theory on the biodynamic frequency weighting for studying hand-transmitted vibration exposures and vibration-induced effects. We hypothesize that the development of a vibration effect is the result of two consecutive but synergistic processes: biodynamic responses to input vibration and biological responses to the biomechanical stimuli resulting from the biodynamic responses. Hence, we further hypothesize that the frequency-dependency (W) of the effect generally includes two components: a biodynamic frequency weighting (W1) and a biological frequency weighting (W2), or W=W1•W2. These hypotheses are consistent with the stress and strain analysis theory and methods widely used in structural dynamics and biomechanics. The factorization may make it easier to study the complex frequency-dependency using different approaches: the biodynamic frequency weighting depends on the passive physical response of the system to vibration, and it can thus be determined by examining the biodynamic response of the system using various engineering methods; on the other hand, the biological frequency weighting depends on the biological mechanisms of the effects, and it can be investigated by studying the psychophysical, physiological, and pathological responses. To help test these hypotheses, this study reviewed and further developed methods to derive the finger biodynamic frequency weighting. As a result, preliminary finger biodynamic frequency weightings are proposed. The implications of the proposed theory and the preliminary biodynamic frequency weightings are also discussed. PMID:23060254

  3. A proposed theory on biodynamic frequency weighting for hand-transmitted vibration exposure.

    PubMed

    Dong, Ren G; Welcome, Daniel E; McDowell, Thomas W; Xu, Xueyan S; Krajnak, Kristine; Wu, John Z

    2012-01-01

    The objective of this study is to propose a theory on the biodynamic frequency weighting for studying hand-transmitted vibration exposures and vibration-induced effects. We hypothesize that the development of a vibration effect is the result of two consecutive but synergistic processes: biodynamic responses to input vibration and biological responses to the biomechanical stimuli resulting from the biodynamic responses. Hence, we further hypothesize that the frequency-dependency (W) of the effect generally includes two components: a biodynamic frequency weighting (W1) and a biological frequency weighting (W2), or W=W1• W2. These hypotheses are consistent with the stress and strain analysis theory and methods widely used in structural dynamics and biomechanics. The factorization may make it easier to study the complex frequency-dependency using different approaches: the biodynamic frequency weighting depends on the passive physical response of the system to vibration, and it can thus be determined by examining the biodynamic response of the system using various engineering methods; on the other hand, the biological frequency weighting depends on the biological mechanisms of the effects, and it can be investigated by studying the psychophysical, physiological, and pathological responses. To help test these hypotheses, this study reviewed and further developed methods to derive the finger biodynamic frequency weighting. As a result, preliminary finger biodynamic frequency weightings are proposed. The implications of the proposed theory and the preliminary biodynamic frequency weightings are also discussed.

  4. Immediate effects of 2 different whole-body vibration frequencies on muscle peak torque and stiffness.

    PubMed

    Siu, Parco M; Tam, Bjorn T; Chow, Daniel H; Guo, Jing-Yi; Huang, Yan-Ping; Zheng, Yong-Ping; Wong, Stephen H

    2010-10-01

    To examine the immediate effects of 2 vibration protocols with different vibration frequencies that yielded the same maximum acceleration (106.75ms(-2)) on muscle peak torque and stiffness of knee extensor and flexor. Randomized crossover study with repeated measures. Laboratory setting. Recreationally active male adults (N=10). Participants performed 10 bouts of 60-second static half squats intermitted with a 60-second rest period between bouts on a platform with no vibration (control) and a vibration frequency of 26Hz or 40Hz. Concentric and eccentric peak torques of knee extensor and flexor were examined within 5 minutes before and after vibration by isokinetic test. Young's modulus as an index of tissue stiffness was determined at quadriceps and hamstring pre- and postvibration by using an ultrasound indentation method. The 2-way repeated-measures analysis of variance indicated a significant interaction effect between vibration and vibration frequency for knee extensor concentric peak torque (P=.003). The vibration-induced changes of knee extensor concentric peak torque in vibration frequency of 26Hz (14.5Nm) and 40Hz (12.0Nm) were found to be significantly greater than that in controls (-29.4Nm) (P<.05). The change in eccentric peak torque of knee flexor after vibration tended to be greater in 26Hz of vibration frequency when compared with controls (26Hz of vibration frequency vs controls: 13.9±7.1 vs -11.4±5.3Nm, P=.08). No statistically significant differences were obtained in tissue stiffness in the quadriceps and hamstring with any of the conditions. Our data suggest that whole-body vibration at a frequency of 26Hz and 40Hz preclude the decline in concentric peak torque of knee extensor observed after 10 bouts of 60 seconds of static half squats. A change in muscle mechanical stiffness property as induced by whole-body vibration is not supported by our data. Copyright © 2010 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All

  5. Acute effects of various whole body vibration frequencies on 1RM in trained and untrained subjects.

    PubMed

    Rønnestad, Bent R

    2009-10-01

    The purpose of this study was to compare the acute effects of whole body vibration (WBV) at different vibration frequencies on 1 repetition maximum (1RM) in recreationally strength trained subjects and untrained subjects. While performing a 1RM test in half squat, trained (8 men) and untrained (5 men and 3 women) subjects were randomly exposed to WBV with a frequency of 20 Hz, 35 Hz, 50 Hz (amplitude, 3 mm), or control conditions with no vibration. 1RM in half squat was assessed in a Smith Machine while subjects were standing on a vibration platform. Both untrained and recreationally strength trained subjects increased their 1RM at a vibration frequency of 50 Hz compared with no vibration (p < 0.05), and untrained subjects increased their 1RM to a larger extent than recreationally trained subjects (8.7% vs. 4.9%; p < 0.05). However, there was no difference in 1RM while vibrating at a frequency of 20 Hz and 35 Hz compared with no vibrations in either of the groups. In conclusion, WBV with a frequency of 50 Hz increases 1RM in both recreationally strength trained and untrained subjects, whereas vibration frequencies of 20 Hz and 35 Hz do not have this effect. Untrained subjects increased their 1RM at WBV at 50 Hz to a larger extent than recreationally strength trained subjects. Therefore, if the purpose is to increase the stimulus to the neuromuscular system to a greater extent than traditional strength training, the WBV frequency should be 50 Hz and the exercises should be heavily loaded (as in traditional strength training).

  6. The low frequency 2D vibration sensor based on flat coil element

    SciTech Connect

    Djamal, Mitra; Sanjaya, Edi; Islahudin; Ramli

    2012-06-20

    Vibration like an earthquake is a phenomenon of physics. The characteristics of these vibrations can be used as an early warning system so as to reduce the loss or damage caused by earthquakes. In this paper, we introduced a new type of low frequency 2D vibration sensor based on flat coil element that we have developed. Its working principle is based on position change of a seismic mass that put in front of a flat coil element. The flat coil is a part of a LC oscillator; therefore, the change of seismic mass position will change its resonance frequency. The results of measurements of low frequency vibration sensor in the direction of the x axis and y axis gives the frequency range between 0.2 to 1.0 Hz.

  7. Storage capacity and vibration frequencies of guest molecules in CH4 and CO2 hydrates by first-principles calculations.

    PubMed

    Cao, Xiaoxiao; Su, Yan; Liu, Yuan; Zhao, Jijun; Liu, Changling

    2014-01-09

    Using first-principle calculations at B97-D/6-311++G(2d,2p) level, we systematically explore the gas capacity of five standard water cavities (5(12), 4(3)5(6)6(3), 5(12)6(2), 5(12)6(4), and 5(12)6(8)) in clathrate hydrate and study the inclusion complexes to infer general trends in vibrational frequencies of guest molecules as a function of cage size and number of guest molecules. In addition, the Raman spectra of hydrates from CO2/CH4 gases are simulated. From our calculations, the maximum cage occupancy of the five considered cages (5(12), 4(3)5(6)6(3), 5(12)6(2), 5(12)6(4), and 5(12)6(8)) is one, one, two, three, and seven for both CH4 and CO2 guest molecules, respectively. Meanwhile, the optimum cage occupancy are one, one, one, two, and four for CO2 molecules and one, one, two, three, and five for CH4 molecules, respectively. Both the C-H stretching frequency of CH4 and the C-O stretching frequency of CO2 gradually decrease as size of the water cages increases. Meanwhile, the C-H stretching frequency gradually increases as the amount of CH4 molecules in the water cavity (e.g., 5(12)6(8)) increases.

  8. Co-Assignment of the Molecular Vibrational Frequencies in Different Electronic States

    NASA Astrophysics Data System (ADS)

    Panchenko, Yurii; Abramenkov, Alexander

    2016-06-01

    Ultrafast electron diffraction experimental data for the structural parameters of molecules in excited electronic states are comparatively uncommon, hence these parameters are largely unknown. However, because differences between the molecular geometries of excited and ground electronic states cause differences in their experimental vibrational spectra it is important to establish a correspondence between the molecular vibrational frequencies in the ground state and those of the excited state of interest. The correct co-assignment of the experimental vibrational frequencies between two different electronic states of a molecule may be determined by the analog of the Duschinsky matrix D. This matrix D is defined as D = (LI)-1LII where LI and LII are the matrices of the vibrational modes of the two states of the molecule under investigation. They are obtained by solving the vibrational problems in the I and II electronic states, respectively. Choosing the dominant elements in columns of the D matrix and permuting these columns to arrange these elements along the diagonal of the transformed matrix Dast makes it possible to establish the correct co-assignment of the calculated frequencies in the two electronic states. The rows of Dast are for the vibrations in the I electronic state, whereas the columns are for vibrations in the II electronic state. The results obtained may be tested by analogous calculations of Dast for isotopologues. The feasibility of co-assignments of the vibrational frequencies in the ground and T_1 and S_1 excited electronic states are demonstrated for trans-C_2O_2F_2. The analogs of the Duschinsky matrix Dast were used to juxtapose the vibrational frequencies of this molecule calculated at the CASPT2/cc-pVTZ level in the S_0, T_1 and S_1 states. F. Duschinsky, Acta Physicochim. URSS, 7(4), 551-566 (1937). Yu. N. Panchenko, Vibrational spectroscopy, 68, 236-240 (2013).

  9. High frequency vibration characteristics of electric wheel system under in-wheel motor torque ripple

    NASA Astrophysics Data System (ADS)

    Mao, Yu; Zuo, Shuguang; Wu, Xudong; Duan, Xianglei

    2017-07-01

    With the introduction of in-wheel motor, the electric wheel system encounters new vibration problems brought by motor torque ripple excitation. In order to analyze new vibration characteristics of electric wheel system, torque ripple of in-wheel motor based on motor module and vector control system is primarily analyzed, and frequency/order features of the torque ripple are discussed. Then quarter vehicle-electric wheel system (QV-EWS) dynamics model based on the rigid ring tire assumption is established and the main parameters of the model are identified according to tire free modal test. Modal characteristics of the model are further analyzed. The analysis indicates that torque excitation of in-wheel motor is prone to arouse horizontal vibration, in which in-phase rotational, anti-phase rotational and horizontal translational modes of electric wheel system mainly participate. Based on the model, vibration responses of the QV-EWS under torque ripple are simulated. The results show that unlike vertical low frequency (lower than 20 Hz) vibration excited by road roughness, broadband torque ripple will arouse horizontal high frequency (50-100 Hz) vibration of electric wheel system due to participation of the three aforementioned modes. To verify the theoretical analysis, the bench experiment of electric wheel system is conducted and vibration responses are acquired. The experiment demonstrates the high frequency vibration phenomenon of electric wheel system and the measured order features as well as main resonant frequencies agree with simulation results. Through theoretical modeling, analysis and experiments this paper reveals and explains the high frequency vibration characteristics of electric wheel system, providing references for the dynamic analysis, optimal design of QV-EWS.

  10. A programmable broadband low frequency active vibration isolation system for atom interferometry

    NASA Astrophysics Data System (ADS)

    Tang, Biao; Zhou, Lin; Xiong, Zongyuan; Wang, Jin; Zhan, Mingsheng

    2014-09-01

    Vibration isolation at low frequency is important for some precision measurement experiments that use atom interferometry. To decrease the vibrational noise caused by the reflecting mirror of Raman beams in atom interferometry, we designed and demonstrated a compact stable active low frequency vibration isolation system. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. With the help of field programmable gate array-based control subsystem, the vibration isolation system performed flexibly and accurately. When the feedback is on, the intrinsic resonance frequency of the system will change from 0.8 Hz to about 0.015 Hz. The vertical vibration (0.01-10 Hz) measured by the in-loop seismometer is reduced by an additional factor of up to 500 on the basis of a passive vibration isolation platform, and we have proved the performance by adding an additional seismometer as well as applying it in the atom interferometry experiment.

  11. A programmable broadband low frequency active vibration isolation system for atom interferometry.

    PubMed

    Tang, Biao; Zhou, Lin; Xiong, Zongyuan; Wang, Jin; Zhan, Mingsheng

    2014-09-01

    Vibration isolation at low frequency is important for some precision measurement experiments that use atom interferometry. To decrease the vibrational noise caused by the reflecting mirror of Raman beams in atom interferometry, we designed and demonstrated a compact stable active low frequency vibration isolation system. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. With the help of field programmable gate array-based control subsystem, the vibration isolation system performed flexibly and accurately. When the feedback is on, the intrinsic resonance frequency of the system will change from 0.8 Hz to about 0.015 Hz. The vertical vibration (0.01-10 Hz) measured by the in-loop seismometer is reduced by an additional factor of up to 500 on the basis of a passive vibration isolation platform, and we have proved the performance by adding an additional seismometer as well as applying it in the atom interferometry experiment.

  12. Influence of whole body vibration platform frequency on neuromuscular performance of community-dwelling older adults.

    PubMed

    Furness, Trentham P; Maschette, Wayne E

    2009-08-01

    The purpose of this study was to progressively overload vibration platform frequency to describe sea-saw whole body vibration influence on neuromuscular performance of community-dwelling older adults. Seventy-three community-dwelling older adults (aged 72 +/- 8 years) were randomly assigned to 4 groups (zero, one, 2, and 3 whole body vibration sessions per week). Quantifiers of neuromuscular performance such as the 5-Chair Stands test, the Timed Up and Go (TUG) test, and the Tinetti test were recorded. Furthermore, Health-related quality of life was qualified with the SF-36 Health Survey. A 6-week whole body vibration intervention significantly improved the quantifiers of neuromuscular performance in a community-dwelling older adult sample. Whole body vibration was shown to significantly reduce time taken to complete the 5-Chair Stands test (p < 0.05) and the TUG test (p < 0.05). Tinetti test scores significantly improved (p < 0.05). as did all components of health-related quality of life (p < 0.05). Overall, progressively overloaded frequency elicited more beneficial improvement for the 3 whole body vibration sessions per week group. It was concluded that progressively overloaded frequency was effective in improving quantifiable measures of neuromuscular performance in the sample and that practitioners may confidently prescribe 3 whole body vibration sessions per week with more precise knowledge of the effects of whole body vibration on neuromuscular performance and health-related quality-of-life effects.

  13. Analysis of muscle fatigue induced by isometric vibration exercise at varying frequencies.

    PubMed

    Mischi, M; Rabotti, C; Cardinale, M

    2012-01-01

    An increase in neuromuscular activity, measured by electromyography (EMG), is usually observed during vibration exercise. The underlying mechanisms are however unclear, limiting the possibilities to introduce and exploit vibration training in rehabilitation programs. In this study, a new training device is used to perform vibration exercise at varying frequency and force, therefore enabling the analysis of the relationship between vibration frequency and muscle fatigue. Fatigue is estimated by maximum voluntary contraction measurement, as well as by EMG mean-frequency and conduction-velocity analysis. Seven volunteers performed five isometric contractions of the biceps brachii with a load consisting of a baseline of 80% of their maximum voluntary contraction (MVC), with no vibration and with a superimposed 20, 30, 40, and 50 Hz vibrational force of 40 N. Myoelectric and mechanical fatigue were estimated by EMG analysis and by assessment of the MVC decay, respectively. A dedicated motion artifact canceler, making use of accelerometry, is proposed to enable accurate EMG analysis. Use of this canceler leads to better interpolation of myoelectric fatigue trends and to better correlation between mechanical and myoelectric fatigue. In general, our results suggest vibration at 30 Hz to be the most fatiguing exercise. These results contribute to the analysis of vibration exercise and motivate further research aiming at improved training protocols.

  14. Qualitative Behavior of the Low-Frequency Vibrational Dynamics of Microtubules and the Surrounding Water.

    PubMed

    Moix, Jeremy M; Parker, James E; Echchgadda, Ibtissam

    2017-04-13

    The dynamics of the low-frequency vibrational modes of microtubules play a key role in many theoretical models regarding their biological function. We analyze these dynamics through large scale, classical molecular dynamics simulations of a microtubule composed of 42 tubulin heterodimers to provide insights into the qualitative nature of the vibrational energy absorption and dissipation mechanisms. The computed microtubule absorption spectra and vibrational density of states in the terahertz regime are presented, along with an analysis of the vibrational dephasing rates of the tubulin monomer center of mass dynamics, which are shown to be overdamped. Additionally, the presence of the microtubule modifies the dynamical properties of the solvation shell structure within roughly 10 Å of the protein. These vibrational properties are similar to those seen in other globular proteins and indicate microtubules are unlikely candidates for any large scale collective vibrational processes in the terahertz regime such as Fröhlich condensates.

  15. Detection of two identical frequency vibrations by phase discrimination in polarization-OTDR

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Pan, Yun; Zhang, MingJiang; Cao, Chunqi; Zhang, Xuping

    2017-04-01

    In this paper, a new detection method for two identical frequency vibrations along optic fiber is proposed, by discrimination of their phase relationship in polarization optical time-domain reflectometer (POTDR). A vibration on fiber would modulate its index and birefringence, then it can consequently change the state of polarization (SOP) of the scattering signal. However, multiple simultaneous vibrations at different positions would result in random fluctuating SOP of the scattering signal, which make them very difficult to be identified. In our proposed method, the phase of the vibration signal along the fiber is obtained by Fast Fourier Transform. Therefore, two vibration events with the same frequency could be distinguished effectively by using the pattern of the phase distribution. The principle of the method is analyzed in detail. Both simulation and experiment results are presented to demonstrate the validity and limitation of this method. It could be widely used for safety monitoring of long distance perimeters, electrical transmission line, and so on.

  16. Enhancement to Non-Contacting Stress Measurement of Blade Vibration Frequency

    NASA Technical Reports Server (NTRS)

    Platt, Michael; Jagodnik, John

    2011-01-01

    A system for turbo machinery blade vibration has been developed that combines time-of-arrival sensors for blade vibration amplitude measurement and radar sensors for vibration frequency and mode identification. The enabling technology for this continuous blade monitoring system is the radar sensor, which provides a continuous time series of blade displacement over a portion of a revolution. This allows the data reduction algorithms to directly calculate the blade vibration frequency and to correctly identify the active modes of vibration. The work in this project represents a significant enhancement in the mode identification and stress calculation accuracy in non-contacting stress measurement system (NSMS) technology when compared to time-of-arrival measurements alone.

  17. Electrostatic energy harvesting device with dual resonant structure for wideband random vibration sources at low frequency.

    PubMed

    Zhang, Yulong; Wang, Tianyang; Zhang, Ai; Peng, Zhuoteng; Luo, Dan; Chen, Rui; Wang, Fei

    2016-12-01

    In this paper, we present design and test of a broadband electrostatic energy harvester with a dual resonant structure, which consists of two cantilever-mass subsystems each with a mass attached at the free edge of a cantilever. Comparing to traditional devices with single resonant frequency, the proposed device with dual resonant structure can resonate at two frequencies. Furthermore, when one of the cantilever-masses is oscillating at resonance, the vibration amplitude is large enough to make it collide with the other mass, which provides strong mechanical coupling between the two subsystems. Therefore, this device can harvest a decent power output from vibration sources at a broad frequency range. During the measurement, continuous power output up to 6.2-9.8 μW can be achieved under external vibration amplitude of 9.3 m/s(2) at a frequency range from 36.3 Hz to 48.3 Hz, which means the bandwidth of the device is about 30% of the central frequency. The broad bandwidth of the device provides a promising application for energy harvesting from the scenarios with random vibration sources. The experimental results indicate that with the dual resonant structure, the vibration-to-electricity energy conversion efficiency can be improved by 97% when an external random vibration with a low frequency filter is applied.

  18. Comparative analysis of high-frequency dynamic measurement experiment for vibration sensor and GPS receiver

    NASA Astrophysics Data System (ADS)

    Ding, Keliang; Song, Zichao; Zhou, Mingduan; Liu, Miao

    2015-12-01

    Sensor technology applied in dynamic measurement in recent years become the mainly focus subject of attention. In this paper, the high-frequency data collected by two kinds of sensors from vibration sensor and GPS receiver are comparatively analyzed. The integrated scheme of dynamic measurement is proposed based on the high-frequency data for vibration sensor and GPS receiver. The result of experiment is shown that the above sensors with the some same characteristics based on the advantages of the sensors applied in the scheme. Finally, the feasibility and effectiveness of the integrated scheme for the vibration sensor and GPS receiver is verified in the dynamic measurement experiment.

  19. Active vibration control using optimized modified acceleration feedback with Adaptive Line Enhancer for frequency tracking

    NASA Astrophysics Data System (ADS)

    Nima Mahmoodi, S.; Craft, Michael J.; Southward, Steve C.; Ahmadian, Mehdi

    2011-03-01

    Modified acceleration feedback (MAF) control, an active vibration control method that uses collocated piezoelectric actuators and accelerometer is developed and its gains optimized using an optimal controller. The control system consists of two main parts: (1) frequency adaptation that uses Adaptive Line Enhancer (ALE) and (2) an optimized controller. Frequency adaptation method tracks the frequency of vibrations using ALE. The obtained frequency is then fed to MAF compensators. This provides a unique feature for MAF, by extending its domain of capabilities from controlling a certain mode of vibrations to any excited mode. The optimized MAF controller can provide optimal sets of gains for a wide range of frequencies, based on the characteristics of the system. The experimental results show that the frequency tracking method works quite well and fast enough to be used in a real-time controller. ALE parameters are numerically and experimentally investigated and tuned for optimized frequency tracking. The results also indicate that the MAF can provide significant vibration reduction using the optimized controller. The control power varies for vibration suppression at different resonance frequencies; however, it is always optimized.

  20. Low-frequency vibrational modes in blue opsin: A computational study

    NASA Astrophysics Data System (ADS)

    Thirumuruganandham, Saravana Prakash; Urbassek, Herbert M.

    Vibrational excitations of low-frequency collective modes are essential for functionally important conformational transitions in proteins. We have carried out an analysis of the low-frequency modes in blue opsin based on both normal-mode analysis and molecular dynamics simulations. Power spectra obtained by molecular dynamics agree well with the normal modes. A representative set of low-frequency modes is discussed with the help of vector-field representation. We thus demonstrate that terahertz spectroscopy of low-frequency modes might be relevant for identifying those vibrational degrees of freedom that correlate to known conformational changes in opsins.

  1. Estimation of vibration frequency of loudspeaker diaphragm by parallel phase-shifting digital holography

    NASA Astrophysics Data System (ADS)

    Kakue, T.; Endo, Y.; Shimobaba, T.; Ito, T.

    2014-11-01

    We report frequency estimation of loudspeaker diaphragm vibrating at high speed by parallel phase-shifting digital holography which is a technique of single-shot phase-shifting interferometry. This technique records multiple phaseshifted holograms required for phase-shifting interferometry by using space-division multiplexing. We constructed a parallel phase-shifting digital holography system consisting of a high-speed polarization-imaging camera. This camera has a micro-polarizer array which selects four linear polarization axes for 2 × 2 pixels. We set a loudspeaker as an object, and recorded vibration of diaphragm of the loudspeaker by the constructed system. By the constructed system, we demonstrated observation of vibration displacement of loudspeaker diaphragm. In this paper, we aim to estimate vibration frequency of the loudspeaker diaphragm by applying the experimental results to frequency analysis. Holograms consisting of 128 × 128 pixels were recorded at a frame rate of 262,500 frames per second by the camera. A sinusoidal wave was input to the loudspeaker via a phone connector. We observed displacement of the loudspeaker diaphragm vibrating by the system. We also succeeded in estimating vibration frequency of the loudspeaker diaphragm by applying frequency analysis to the experimental results.

  2. Statistical analysis of low frequency vibrations in variable speed wind turbines

    NASA Astrophysics Data System (ADS)

    Escaler, X.; Mebarki, T.

    2013-12-01

    The spectral content of the low frequency vibrations in the band from 0 to 10 Hz measured in full scale wind turbines has been statistically analyzed as a function of the whole range of steady operating conditions. Attention has been given to the amplitudes of the vibration peaks and their dependency on rotating speed and power output. Two different wind turbine models of 800 and 2000 kW have been compared. For each model, a sample of units located in the same wind farm and operating during a representative period of time have been considered. A condition monitoring system installed in each wind turbine has been used to register the axial acceleration on the gearbox casing between the intermediate and the high speed shafts. The average frequency spectrum has permitted to identify the vibration signature and the position of the first tower natural frequency in both models. The evolution of the vibration amplitudes at the rotor rotating frequency and its multiples has shown that the tower response is amplified by resonance conditions in one of the models. So, it is concluded that a continuous measurement and control of low frequency vibrations is required to protect the turbines against harmful vibrations of this nature.

  3. Coarse-fine adaptive tuned vibration absorber with high frequency resolution

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Yang, Bintang; You, Jiaxin; Gao, Zhe

    2016-11-01

    The speed fluctuation of satellite-rotary-mechanisms causes vibration of slightly different frequencies. The critical requirements of satellites need a vibration control device with high frequency resolution to suppress the vibration. This paper presents a coarse-fine adaptive tuned vibration absorber (ATVA) with high frequency resolution. The coarse-fine ATVA which simultaneously satisfies the requirements of high resolution and relatively wide effective bandwidth is capable of tracking the variable exciting frequency adaptively to suppress the vibration of the primary system. The coarse-fine ATVA is divided into a coarse tuning segment and a fine tuning segment. The coarse tuning segment is used to tune the required natural frequency in a relatively wide effective bandwidth and the fine tuning segment can achieve precise tune in a tiny-scale bandwidth. The mathematical model of the coarse tuning and the fine tuning is proposed to design the parameters of the coarse-fine ATVA. The experimental test results indicate the coarse tuning bandwidth of the coarse-fine ATVA is 8.7 Hz to 29 Hz and the minimum resolution of the fine tuning is 0.05 Hz. Moreover, a significant vibration attenuation of 15dB is verified in the effective bandwidth.

  4. High-precision absolute distance and vibration measurement with frequency scanned interferometry

    SciTech Connect

    Yang, H.-J.; Deibel, Jason; Nyberg, Sven; Riles, Keith

    2005-07-01

    We report high-precision absolute distance and vibration measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distance was determined by counting the interference fringes produced while scanning the laser frequency. A high-finesse Fabry-Perot interferometer was used to determine frequency changes during scanning. Two multiple-distance-measurement analysis techniques were developed to improve distance precision and to extract the amplitude and frequency of vibrations. Under laboratory conditions, measurement precision of {approx}50 nm was achieved for absolute distances ranging from 0.1 to 0.7 m by use of the first multiple-distance-measurement technique. The second analysis technique has the capability to measure vibration frequencies ranging from 0.1 to 100 Hz with an amplitude as small as a few nanometers without a priori knowledge.

  5. High-precision absolute distance and vibration measurement with frequency scanned interferometry.

    PubMed

    Yang, Hai-Jun; Deibel, Jason; Nyberg, Sven; Riles, Keith

    2005-07-01

    We report high-precision absolute distance and vibration measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distance was determined by counting the interference fringes produced while scanning the laser frequency. A high-finesse Fabry-Perot interferometer was used to determine frequency changes during scanning. Two multiple-distance-measurement analysis techniques were developed to improve distance precision and to extract the amplitude and frequency of vibrations. Under laboratory conditions, measurement precision of approximately 50 nm was achieved for absolute distances ranging from 0.1 to 0.7 m by use of the first multiple-distance-measurement technique. The second analysis technique has the capability to measure vibration frequencies ranging from 0.1 to 100 Hz with an amplitude as small as a few nanometers without a priori knowledge.

  6. Low-amplitude, broad-frequency vibration effects on cortical bone formation in mice.

    PubMed

    Castillo, Alesha B; Alam, Imranul; Tanaka, Shigeo M; Levenda, Jeffery; Li, Jiliang; Warden, Stuart J; Turner, Charles H

    2006-11-01

    Mechanical loading of the skeleton is necessary to maintain bone structure and strength. Large amplitude strains associated with vigorous activity typically result in the greatest osteogenic response; however, data suggest that low-amplitude, broad-frequency vibration results in new bone formation and may enhance adaptation through a stochastic resonance (SR) phenomenon. That is, random noise may maximally enhance bone formation to a known osteogenic stimulus. The aims of this study were to (1) assess the ability of different vibration signals to enhance cortical bone formation during short- and long-term loading and (2) determine whether vibration could effect SR in bone. Two studies were completed wherein several osteogenic loading waveforms, with or without an additive low-amplitude, broad-frequency (0-50 Hz) vibration signal, were applied to the mouse ulna in axial compression. In study 1, mice were loaded short-term (30 s/day, 2 days) with either a carrier signal alone (1 or 2 N sine waveform), vibration signal alone [0.1 N or 0.3 N root mean square (RMS)] or combined carrier and vibration signal. In study 2, mice were loaded long-term (30 s/day, 3 days/week, 4 weeks) with a carrier signal alone (static or sine waveform), vibration signal alone (0.02 N, 0.04 N, 0.08 N or 0.25 N RMS) or combined carrier and vibration signal. Sequential calcein bone labels were administered at 2 and 4 days and at 4 and 29 days after the first day of loading in study 1 and 2, respectively; bone formation parameters and changes in geometry were measured. Combined application of the carrier and vibration signals in study 1 resulted in significantly greater bone formation than with either signal alone (P < 0.001); however, this increase was independently explained by increased strain levels associated with additive vibration. When load and strain levels were similar across loading groups in study 2, cortical bone formation and changes in geometry were not significantly altered by

  7. Low-frequency vibration control of a pan/tilt platform with vision feedback

    NASA Astrophysics Data System (ADS)

    Chang, Yin-Chieh; Shaw, Jinsiang

    2007-05-01

    This paper aims to develop active control techniques with vision feedback for suppressing low-frequency vibration of a device mounted on a pan/tilt platform due to its base disturbances. Pan/tilt platforms are commonly seen in the head of a waking robot, in an antenna, in a vision surveillance equipment, in a cannon platform, etc., for yaw and pitch direction control. However, due to its inevitable low-frequency base vibration possibly from road or sea wave disturbance in a mobile situation, orientation control of the device mounted on the top tilt platform can be seriously affected. In this paper, an adaptive sliding control (ASC) scheme is first derived and employed for vibration attenuation. Function approximation technique is used to represent the unknown disturbance in some finite linear combination of the orthogonal basis. The dynamics of pan/tilt system can thus be proved to be a stable first-order filter driven by function approximation errors. Moreover, the adaptive update law can be obtained by using the Lyapunov stability theory. Secondly, the frequently used feedback active vibration control (AVC) with filtered- x LMS algorithm is to be used and compared with the adaptive sliding control for vibration suppression performance. Experimental tests of the control algorithms show that for independent single axis excitation, about 25.14 and 23 dB attenuations in average for single-frequency disturbance have been obtained by using the ASC and feedback AVC, respectively. For dual-frequency excitation, the vibration attenuations are about 20.77 and 12.73 dB by the two methods, respectively. As for simultaneous two axes excitations, ASC and feedback AVC have respective 17.57 and 15.18 dB vibration reductions under single-frequency disturbances. Thus, validity and effectiveness of the two active control methods with vision feedback for suppressing low-frequency vibration of the device on the pan/tilt platform is verified.

  8. The influence of vibration type, frequency, body position and additional load on the neuromuscular activity during whole body vibration.

    PubMed

    Ritzmann, Ramona; Gollhofer, Albert; Kramer, Andreas

    2013-01-01

    This study aimed to assess the influence of different whole body vibration (WBV) determinants on the electromyographic (EMG) activity during WBV in order to identify those training conditions that cause highest neuromuscular responses and therefore provide optimal training conditions. In a randomized cross-over study, the EMG activity of six leg muscles was analyzed in 18 subjects with respect to the following determinants: (1) vibration type (side-alternating vibration (SV) vs. synchronous vibration (SyV), (2) frequency (5-10-15-20-25-30 Hz), (3) knee flexion angle (10°-30°-60°), (4) stance condition (forefoot vs. normal stance) and (5) load variation (no extra load vs. additional load equal to one-third of the body weight). The results are: (1) neuromuscular activity during SV was enhanced compared to SyV (P < 0.05); (2) a progressive increase in frequency caused a progressive increase in EMG activity (P < 0.05); (3) the EMG activity was highest for the knee extensors when the knee joint was 60° flexed (P < 0.05); (4) for the plantar flexors in the forefoot stance condition (P < 0.05); and (5) additional load caused an increase in neuromuscular activation (P < 0.05). In conclusion, large variations of the EMG activation could be observed across conditions. However, with an appropriate adjustment of specific WBV determinants, high EMG activations and therefore high activation intensities could be achieved in the selected muscles. The combination of high vibration frequencies with additional load on an SV platform led to highest EMG activities. Regarding the body position, a knee flexion of 60° and forefoot stance appear to be beneficial for the knee extensors and the plantar flexors, respectively.

  9. Effect of vibration frequency on agonist and antagonist arm muscle activity.

    PubMed

    Rodríguez Jiménez, Sergio; Benítez, Adolfo; García González, Miguel A; Moras Feliu, Gerard; Maffiuletti, Nicola A

    2015-06-01

    This study aimed to assess the effect of vibration frequency (f out) on the electromyographic (EMG) activity of the biceps brachii (BB) and triceps brachii (TB) muscles when acting as agonist and antagonist during static exercises with different loads. Fourteen healthy men were asked to hold a vibratory bar as steadily as possible for 10 s during lying row (pulling) and bench press (pushing) exercise at f out of 0 (non-vibration condition), 18, 31 and 42 Hz with loads of 20, 50, and 80 % of the maximum sustainable load (MSL). The root mean square of the EMG activity (EMGRMS) of the BB and TB muscles was expressed as a function of the maximal EMGRMS for respective muscles to characterize agonist activation and antagonist coactivation. We found that (1) agonist activation was greater during vibration (42 Hz) compared to non-vibration exercise for the TB but not for the BB muscle (p < 0.05); (2) antagonist activation was greater during vibration compared to non-vibration exercise for both BB (p < 0.01) and TB (p < 0.05) muscles; (3) the vibration-induced increase in antagonist coactivation was proportional to vibration f out in the range 18-42 Hz and (4) the vibration-induced increase in TB agonist activation and antagonist coactivation occurred at all loading conditions in the range 20-80 % MSL. The use of high vibration frequencies within the range of 18-42 Hz can maximize TB agonist activation and antagonist activation of both BB and TB muscles during upper limb vibration exercise.

  10. C-5A Cargo Deck Low-Frequency Vibration Environment

    DTIC Science & Technology

    1975-02-01

    SAMPLE VIBRATION CALCULATIONS 13 1. Normal Distribution 13 2. Binomial Distribution 15 IV CONCLUSIONS 17 -! V REFERENCES 18 t: FEiCENDIJJ PAGS 2LANKNOT...Calculation for Binomial Distribution 108 (Vertical Acceleration, Right Rear Cargo Deck) xi I. INTRODUCTION The availability of large transport...the end of taxi. These peaks could then be used directly to compile the probability of occurrence of specific values of acceleration using the binomial

  11. Electrostatics determine vibrational frequency shifts in hydrogen bonded complexes.

    PubMed

    Dey, Arghya; Mondal, Sohidul Islam; Sen, Saumik; Ghosh, Debashree; Patwari, G Naresh

    2014-12-14

    The red-shifts in the acetylenic C-H stretching vibration of C-H∙∙∙X (X = O, N) hydrogen-bonded complexes increase with an increase in the basicity of the Lewis base. Analysis of various components of stabilization energy suggests that the observed red-shifts are correlated with the electrostatic component of the stabilization energy, while the dispersion modulates the stabilization energy.

  12. Frequency characteristics of human muscle and cortical responses evoked by noisy Achilles tendon vibration.

    PubMed

    Mildren, Robyn L; Peters, Ryan M; Hill, Aimee J; Blouin, Jean-Sébastien; Carpenter, Mark G; Inglis, J Timothy

    2017-05-01

    Noisy stimuli, along with linear systems analysis, have proven to be effective for mapping functional neural connections. We explored the use of noisy (10-115 Hz) Achilles tendon vibration to examine somatosensory reflexes in the triceps surae muscles in standing healthy young adults (n = 8). We also examined the association between noisy vibration and electrical activity recorded over the sensorimotor cortex using electroencephalography. We applied 2 min of vibration and recorded ongoing muscle activity of the soleus and gastrocnemii using surface electromyography (EMG). Vibration amplitude was varied to characterize reflex scaling and to examine how different stimulus levels affected postural sway. Muscle activity from the soleus and gastrocnemii was significantly correlated with the tendon vibration across a broad frequency range (~10-80 Hz), with a peak located at ~40 Hz. Vibration-EMG coherence positively scaled with stimulus amplitude in all three muscles, with soleus displaying the strongest coupling and steepest scaling. EMG responses lagged the vibration by ~38 ms, a delay that paralleled observed response latencies to tendon taps. Vibration-evoked cortical oscillations were observed at frequencies ~40-70 Hz (peak ~54 Hz) in most subjects, a finding in line with previous reports of sensory-evoked γ-band oscillations. Further examination of the method revealed 1) accurate reflex estimates could be obtained with <60 s of low-level (root mean square = 10 m/s(2)) vibration; 2) responses did not habituate over 2 min of exposure; and importantly, 3) noisy vibration had a minimal influence on standing balance. Our findings suggest noisy tendon vibration is an effective novel approach to characterize somatosensory reflexes during standing.NEW & NOTEWORTHY We applied noisy (10-115 Hz) vibration to the Achilles tendon to examine the frequency characteristics of lower limb somatosensory reflexes during standing. Ongoing muscle activity was coherent with the

  13. Individual Optimal Frequency in Whole-Body Vibration: Effect of Protocol, Joint Angle, and Fatiguing Exercise.

    PubMed

    Carlucci, Flaminia; Felici, Francesco; Piccinini, Alberto; Haxhi, Jonida; Sacchetti, Massimo

    2016-12-01

    Carlucci, F, Felici, F, Piccinini, A, Haxhi, J, and Sacchetti, M. Individual optimal frequency in whole-body vibration: effect of protocol, joint angle, and fatiguing exercise. J Strength Cond Res 30(12): 3503-3511, 2016-Recent studies have shown the importance of individualizing the vibration intervention to produce greater effects on the neuromuscular system in less time. The purpose of this study was to assess the individual optimal vibration frequency (OVF) corresponding to the highest muscle activation (RMSmax) during vibration at different frequencies, comparing different protocols. Twenty-nine university students underwent 3 continuous (C) and 2 random (R) different vibrating protocols, maintaining a squat position on a vibration platform. The C protocol lasted 50 seconds and involved the succession of ascending frequencies from 20 to 55 Hz, every 5 seconds. The same protocol was performed twice, having the knee angle at 120° (C) and 90° (C90), to assess the effect of joint angle and after a fatiguing squatting exercise (CF) to evaluate the influence of fatigue on OVF assessment. In the random protocols, vibration time was 20 seconds with a 2-minute (R2) and a 4-minute (R4) pauses between tested frequencies. Muscle activation and OVF values did not differ significantly in the C, R2, and R4 protocols. RMSmax was higher in C90 (p < 0.001) and in CF (p = 0.04) compared with the C protocol. Joint angle and fatiguing exercise had no effect on OVF. In conclusion, the shorter C protocol produced similar myoelectrical activity in the R2 and the R4 protocols, and therefore, it could be equally valid in identifying the OVF with considerable time efficiency. Knee joint angle and fatiguing exercise had an effect on surface electromyography response during vibration but did not affect OVF identification significantly.

  14. The effects of low-frequency vibrations on hepatic profile of blood

    NASA Astrophysics Data System (ADS)

    Damijan, Z.

    2008-02-01

    Body vibrations training has become popular in sports training, fitness activity, it is still a rare form of physical rehabilitation.. Vibrations are transmitted onto the whole body or some body parts of an exercising person via a vibration platform subjected to mechanical vertical vibrations. During the training session a participant has to maintain his body position or do exercises that engage specific muscles whilst vibrations of the platform are transmitted onto the person's body. This paper is the continuation of the earlier study covering the effects of low-frequency vibrations on selected physiological parameters of the human body. The experiments were conducted to find the answer to the question if vibration exposure (total duration of training sessions 6 hours 20 min) should produce any changes in hepatic profile of blood. Therefore a research program was undertaken at the University of Science and Technology AGH UST to investigate the effects of low-frequency vibration on selected parameters of hepatic profile of human blood. Cyclic fluctuations of bone loading were induced by the applied harmonic vibration 3.5 Hz and amplitude 0.004 m. The experiments utilizing two vibrating platforms were performed in the Laboratory of Structural Acoustics and Biomedical Engineering AGH-UST. The applied vibrations were harmless and not annoying, in accordance with the standard PN-EN ISO 130901-1, 1998. 23 women volunteers had 19 sessions on subsequent working days, at the same time of day. during the tests the participants remained in the standing position, passive. The main hypothesis has it that short-term low-frequency vibration exposure might bring about the changes of the hepatic profile of blood, including: bilirubin (BILIRUBIN), alkaline phosphatase (Alp), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and albumin (ALBUMIN) levels. Research data indicate the low-frequency vibrations exposure produces statistically significant decrease of

  15. Measurement of small mechanical vibrations of brain tissue exposed to extremely-low-frequency electric fields.

    PubMed

    Spiegel, R J; Ali, J S; Peoples, J F; Joines, W T

    1986-01-01

    Electromagnetic fields can interact with biological tissue both electrically and mechanically. This study investigated the mechanical interaction between brain tissue and an extremely-low-frequency (ELF) electric field by measuring the resultant vibrational amplitude. The exposure cell is a section of X-band waveguide that was modified by the addition of a center conductor to form a small TEM cell within the waveguide structure. The ELF signal is applied to the center conductor of the TEM cell. The applied ELF electric field generates an electrostrictive force on the surface of the brain tissue. This force causes the tissue to vibrate at a frequency equal to twice the frequency of the applied sinusoidal signal. An X-band signal is fed through the waveguide, scattered by the vibrating sample, and detected by a phase-sensitive receiver. Using a time-averaging spectrum analyzer, a vibration sensitivity of approximately 0.2 nmp-p can be achieved. The amplitude of the brain tissue vibrational response is constant for vibrational frequencies below 50 Hz; between 50 and 200 Hz resonant phenomena were observed; and above 200 Hz the amplitude fall-off is rapid.

  16. Etude infrarouge des effets de structure et de solvant sur la frequence itvC=O de cetones aliphatiques saturees. Relation frequence- topologie-milieu

    NASA Astrophysics Data System (ADS)

    Massat, A.; Dubois, J. E.

    1980-08-01

    The sensitivity of saturated aliphatic ketone stretching frequencies, vCO to structure and solvent effects is expressed by a four-term equation vco = 1740 + I(XXX) -0.24 G + 2.10 -3G · I(XXX) The four terms represent: the frequency of the base element (acetone) calculated in the absence of intermolecular interactions; the contribution of intramolecular environment E given by structure parameter I(itXXX) previously established in gas phase; that of the intermolecular environment related to the Allerhand and Schleyer G parameter; that of solvent-solute interactions. This equation covers an experimental range of 78 cm -1 for 192 measurements in four highly diverse solvents (C 6H 14, CC1 4, CH 3CN, CHBr 3) with a standard deviation of 1.6 cm -1; it expresses an overall statistical behavior, but masks individual behaviors. The latter are determined by comparing two characteristic parameters of ketones, a topological parameter I(XXX), and p expressing solvent sensitivity [slope of straight lines ν = f(G)]; they are Interpreted in terms of geometrical effect, variation of valency angles and of conformations.

  17. An extension of command shaping methods for controlling residual vibration using frequency sampling

    NASA Technical Reports Server (NTRS)

    Singer, Neil C.; Seering, Warren P.

    1992-01-01

    The authors present an extension to the impulse shaping technique for commanding machines to move with reduced residual vibration. The extension, called frequency sampling, is a method for generating constraints that are used to obtain shaping sequences which minimize residual vibration in systems such as robots whose resonant frequencies change during motion. The authors present a review of impulse shaping methods, a development of the proposed extension, and a comparison of results of tests conducted on a simple model of the space shuttle robot arm. Frequency shaping provides a method for minimizing the impulse sequence duration required to give the desired insensitivity.

  18. Low-frequency, broadband vibration energy harvester using coupled oscillators and frequency up-conversion by mechanical stoppers

    NASA Astrophysics Data System (ADS)

    Dechant, Eduard; Fedulov, Feodor; Chashin, Dmitrii V.; Fetisov, Leonid Y.; Fetisov, Yuri K.; Shamonin, Mikhail

    2017-06-01

    The frequencies of ambient vibrations are often low (below 30 Hz). A broadband (3 dB bandwidth is larger than 10 Hz at an acceleration amplitude of 9.81 m s-2) vibration based energy harvester is proposed for transducing mechanical energy at such low frequencies into electrical energy. The mechanical setup converts low frequency mechanical vibrations into high frequency resonance oscillations of the transducer. This conversion is done by mechanical impacts on two mechanical stoppers. The originality of the presented design is that both low-frequency and high-frequency oscillators are permanently mechanically coupled. In the equivalent mechanical circuit, this coupling is achieved by connecting the ends of the stiff spring to both seismic masses, whereas one seismic mass (collison member) is also attached to the soft spring used as the constitutive element of a low-frequency oscillator. Further, both mechanical oscillators are not realized as conventional cantilever beams. In particular, the high frequency oscillator with the natural frequency of 340 Hz is a disc-shaped diaphragm with attached piezoelectric elements and a seismic mass. It is shown that it is possible to convert mechanical vibrations with acceleration amplitude of 9.81 m s-2 in the region between approximately 7 and 25 Hz into electrical power larger than 0.1 mW with the maximum value of 0.8 mW. A simplified mathematical model based on piecewise linear coupled oscillators shows good agreement with experimental results. The ways to enhance the performance of the harvester and improve agreement with experiments are discussed.

  19. Fluid dynamic aspects of cardiovascular behavior during low-frequency whole-body vibration

    NASA Technical Reports Server (NTRS)

    Nerem, R. M.

    1973-01-01

    The behavior of the cardiovascular system during low frequency whole-body vibration, such as encountered by astronauts during launch and reentry, is examined from a fluid mechanical viewpoint. The vibration characteristics of typical manned spacecraft and other vibration environments are discussed, and existing results from in vivo studies of the hemodynamic aspects of this problem are reviewed. Recent theoretical solutions to related fluid mechanical problems are then used in the interpretation of these results and in discussing areas of future work. The results are included of studies of the effects of vibration on the work done by the heart and on pulsatile flow in blood vessels. It is shown that important changes in pulse velocity, the instantaneous velocity profile, mass flow rate, and wall shear stress may occur in a pulsatile flow due to the presence of vibration. The significance of this in terms of changes in peripheral vascular resistance and possible damage to the endothelium of blood vessels is discussed.

  20. Disturbing effects of low frequency sound immissions and vibrations in residential buildings.

    PubMed

    Findeis, H; Peters, E

    2004-01-01

    Noise immissions with predominant low frequency sound components may exert considerably disturbing effects in dwellings. This applies in particular to sounds which are excitated by transmission of structure-borne noise, and to low frequency sounds emitted by ventilators. Exposed persons usually declare such immissions as being "intolerable" even at very low A-weighted sound levels. If mechanical vibrations in the frequency range below 20 Hz (ground-borne vibrations) affect dwelling rooms, the annoying effects are perceived only by a small portion of exposed individuals as a physical effect. For the most part the immissions are observed as vibratory effects on the building and on objects inside the dwelling. The disturbing effects of vibration frequencies above 20 Hz (structure-borne sound) are determined by the airborne sound field generated inside a particular room and its given surface and extension.

  1. Development and application of a low-frequency FBG vibration sensor

    NASA Astrophysics Data System (ADS)

    Nan, Qiu-ming

    2010-10-01

    Dynamic monitoring is part of bridge structural health monitoring. Real-time and online monitoring for bridge's dynamic performance is an important technology means for model updating, damage detection of structure and security evaluation of bridge. Nowadays dynamic monitoring system is generally installed on new long-span bridges. Vibration sensor is key part of the technology means. Vibration of a large-scale bridge belongs to low frequency one, but traditional electromagnetic vibration sensors are restricted for use in the field due to such defects as signal unable to long distance transmission, hard to measure ultra-low frequency vibration, so it is inevitable and imminent to develop a novel-type vibration sensor instead of them. Aiming at the above-mentioned problems, the author in the paper develops a low-frequency vibration sensor with double-cantilever beam structure, based on fiber Bragg grating (FBG) and matching filtering demodulation. Some experiments are done to study its sensing properties and the results indicate that it has good temperature compensation, its natural frequency is about 35Hz, measurement bandwidth from 0.1Hz to 20Hz, sensitivity is 1000mv/g or so, linearity degree is over 0.9992, repeatability is superior to 2.4%, acceleration measurement range is 1g, and cross anti-interference is 5.6%. Such sensors have been successfully used on Wuhan Tianxingzhou Yangtze River Bridge(WTYRB). The most transmission distance of measurement signal is 10km or so and the lowest measurement frequency is 0.24 Hz. The application results show it can detect accurately dynamic properties of vital areas of the bridge and can meet the demands for dynamic measurement. To sum up, the sensor developed in the paper can overcome the shortcomings of electromagnetic sensors and has very good sensing properties, so it is very suitable to be used for low-frequency vibration measurement.

  2. Protonated Nitrous Oxide, NNOH(+): Fundamental Vibrational Frequencies and Spectroscopic Constants from Quartic Force Fields

    NASA Technical Reports Server (NTRS)

    Huang, Xinchuan; Fortenberry, Ryan C.; Lee, Timothy J.

    2013-01-01

    The interstellar presence of protonated nitrous oxide has been suspected for some time. Using established high-accuracy quantum chemical techniques, spectroscopic constants and fundamental vibrational frequencies are provided for the lower energy O-protonated isomer of this cation and its deuterated isotopologue. The vibrationally-averaged B0 and C0 rotational constants are within 6 MHz of their experimental values and the D(subJ) quartic distortion constants agree with experiment to within 3%. The known gas phase O-H stretch of NNOH(+) is 3330.91 cm(exp-1), and the vibrational configuration interaction computed result is 3330.9 cm(exp-1). Other spectroscopic constants are also provided, as are the rest of the fundamental vibrational frequencies for NNOH(+) and its deuterated isotopologue. This high-accuracy data should serve to better inform future observational or experimental studies of the rovibrational bands of protonated nitrous oxide in the ISM and the laboratory.

  3. An Analysis of the High Frequency Vibrations in Early Thematic Mapper Scenes

    NASA Technical Reports Server (NTRS)

    Kogut, J.; Larduinat, E.

    1985-01-01

    The motion of the mirrors in the thematic mapper (TM) and multispectral scanner (MSS) instruments, and the motion of other devices, such as the TDRSS antenna drive, and solar array drives onboard LANDSAT-4 cause vibrations to propagate through the spacecraft. These vibrations as well as nonlinearities in the scanning motion of the TM mirror can cause the TM detectors to point away from their nominal positions. Two computer programs, JITTER and SCDFT, were developed as part of the LANDSAT-D Assessment System (LAS), Products and Procedures Analysis (PAPA) program to evaluate the potential effect of high frequency vibrations on the final TM image. The maximum overlap and underlap which were observed for early TM scenes are well within specifications for the ground processing system. The cross scan and scan high frequency vibrations are also within the specifications cited for the flight system.

  4. Raman spectroscopy and x-ray diffraction of sp3CaC O3 at lower mantle pressures

    NASA Astrophysics Data System (ADS)

    Lobanov, Sergey S.; Dong, Xiao; Martirosyan, Naira S.; Samtsevich, Artem I.; Stevanovic, Vladan; Gavryushkin, Pavel N.; Litasov, Konstantin D.; Greenberg, Eran; Prakapenka, Vitali B.; Oganov, Artem R.; Goncharov, Alexander F.

    2017-09-01

    The exceptional ability of carbon to form sp2 and sp3 bonding states leads to a great structural and chemical diversity of carbon-bearing phases at nonambient conditions. Here we use laser-heated diamond-anvil cells combined with synchrotron x-ray diffraction, Raman spectroscopy, and first-principles calculations to explore phase transitions in CaC O3 at P >40 GPa . We find that postaragonite CaC O3 transforms to the previously predicted P 21/c CaC O3 with sp3-hybridized carbon at 105 GPa (˜30 GPa higher than the theoretically predicted crossover pressure). The lowest-enthalpy transition path to P 21/c CaC O3 includes reoccurring sp2 and sp3CaC O3 intermediate phases and transition states, as revealed by our variable-cell nudged-elastic-band simulation. Raman spectra of P 21/c CaC O3 show an intense band at 1025 c m-1 , which we assign to the symmetric C-O stretching vibration based on empirical and first-principles calculations. This Raman band has a frequency that is ˜20 % lower than the symmetric C-O stretching in sp2CaC O3 due to the C-O bond length increase across the sp2-sp3 transition and can be used as a fingerprint of tetrahedrally coordinated carbon in other carbonates.

  5. Tuning and sensitivity of the human vestibular system to low-frequency vibration.

    PubMed

    Todd, Neil P McAngus; Rosengren, Sally M; Colebatch, James G

    2008-10-17

    Mechanoreceptive hair-cells of the vertebrate inner ear have a remarkable sensitivity to displacement, whether excited by sound, whole-body acceleration or substrate-borne vibration. In response to seismic or substrate-borne vibration, thresholds for vestibular afferent fibre activation have been reported in anamniotes (fish and frogs) in the range -120 to -90 dB re 1g. In this article, we demonstrate for the first time that the human vestibular system is also extremely sensitive to low-frequency and infrasound vibrations by making use of a new technique for measuring vestibular activation, via the vestibulo-ocular reflex (VOR). We found a highly tuned response to whole-head vibration in the transmastoid plane with a best frequency of about 100 Hz. At the best frequency we obtained VOR responses at intensities of less than -70 dB re 1g, which was 15 dB lower than the threshold of hearing for bone-conducted sound in humans at this frequency. Given the likely synaptic attenuation of the VOR pathway, human receptor sensitivity is probably an order of magnitude lower, thus approaching the seismic sensitivity of the frog ear. These results extend our knowledge of vibration-sensitivity of vestibular afferents but also are remarkable as they indicate that the seismic sensitivity of the human vestibular system exceeds that of the cochlea for low-frequencies.

  6. Low Frequency Vibrations Induce Malformations in Two Aquatic Species in a Frequency-, Waveform-, and Direction-Specific Manner

    PubMed Central

    Vandenberg, Laura N.; Stevenson, Claire; Levin, Michael

    2012-01-01

    Environmental toxicants such as industrial wastes, air particulates from machinery and transportation vehicles, and pesticide run-offs, as well as many chemicals, have been widely studied for their effects on human and wildlife populations. Yet other potentially harmful environmental pollutants such as electromagnetic pulses, noise and vibrations have remained incompletely understood. Because developing embryos undergo complex morphological changes that can be affected detrimentally by alterations in physical forces, they may be particularly susceptible to exposure to these types of pollutants. We investigated the effects of low frequency vibrations on early embryonic development of two aquatic species, Xenopus laevis (frogs) and Danio rerio (zebrafish), specifically focusing on the effects of varying frequencies, waveforms, and applied direction. We observed treatment-specific effects on the incidence of neural tube defects, left-right patterning defects and abnormal tail morphogenesis in Xenopus tadpoles. Additionally, we found that low frequency vibrations altered left-right patterning and tail morphogenesis, but did not induce neural tube defects, in zebrafish. The results of this study support the conclusion that low frequency vibrations are toxic to aquatic vertebrates, with detrimental effects observed in two important model species with very different embryonic architectures. PMID:23251546

  7. Analysis of damped tissue vibrations in time-frequency space: a wavelet-based approach.

    PubMed

    Enders, Hendrik; von Tscharner, Vinzenz; Nigg, Benno M

    2012-11-15

    There is evidence that vibrations of soft tissue compartments are not appropriately described by a single sinusoidal oscillation for certain types of locomotion such as running or sprinting. This paper discusses a new method to quantify damping of superimposed oscillations using a wavelet-based time-frequency approach. This wavelet-based method was applied to experimental data in order to analyze the decay of the overall power of vibration signals over time. Eight healthy subjects performed sprinting trials on a 30 m runway on a hard surface and a soft surface. Soft tissue vibrations were quantified from the tissue overlaying the muscle belly of the medial gastrocnemius muscle. The new methodology determines damping coefficients with an average error of 2.2% based on a wavelet scaling factor of 0.7. This was sufficient to detect differences in soft tissue compartment damping between the hard and soft surface. On average, the hard surface elicited a 7.02 s(-1) lower damping coefficient than the soft surface (p<0.05). A power spectral analysis of the muscular vibrations occurring during sprinting confirmed that vibrations during dynamic movements cannot be represented by a single sinusoidal function. Compared to the traditional sinusoidal approach, this newly developed method can quantify vibration damping for systems with multiple vibration modes that interfere with one another. This new time-frequency analysis may be more appropriate when an acceleration trace does not follow a sinusoidal function, as is the case with multiple forms of human locomotion.

  8. Computational IR spectroscopy of water: OH stretch frequencies, transition dipoles, and intermolecular vibrational coupling constants

    NASA Astrophysics Data System (ADS)

    Choi, Jun-Ho; Cho, Minhaeng

    2013-05-01

    The Hessian matrix reconstruction method initially developed to extract the basis mode frequencies, vibrational coupling constants, and transition dipoles of the delocalized amide I, II, and III vibrations of polypeptides and proteins from quantum chemistry calculation results is used to obtain those properties of delocalized O-H stretch modes in liquid water. Considering the water symmetric and asymmetric O-H stretch modes as basis modes, we here develop theoretical models relating vibrational frequencies, transition dipoles, and coupling constants of basis modes to local water configuration and solvent electric potential. Molecular dynamics simulation was performed to generate an ensemble of water configurations that was in turn used to construct vibrational Hamiltonian matrices. Obtaining the eigenvalues and eigenvectors of the matrices and using the time-averaging approximation method, which was developed by the Skinner group, to calculating the vibrational spectra of coupled oscillator systems, we could numerically simulate the O-H stretch IR spectrum of liquid water. The asymmetric line shape and weak shoulder bands were quantitatively reproduced by the present computational procedure based on vibrational exciton model, where the polarization effects on basis mode transition dipoles and inter-mode coupling constants were found to be crucial in quantitatively simulating the vibrational spectra of hydrogen-bond networking liquid water.

  9. Modelling of Mechanical Coupling for Piezoelectric Energy Harvester Adapted to Low-Frequency Vibration

    NASA Astrophysics Data System (ADS)

    Untoro, T.; Viridi, S.; Suprijanto; Ekawati, E.

    2017-07-01

    In our previous work, we have developed a mechanical coupling for energy harvester from vibration source. This energy harvester uses piezoelectric with additional cantilever beam and permanent magnets. Our work proposed alternative scheme of mechanical coupling for tune the vibration input into resonant frequency of piezoelectric. Based on the experiment, correlation between the length of cantilever beam and the output power also evaluated. In this paper, we try to modelling our work into mathematical model and apply it to some case study. For example application, we apply our energy harvester system to generate electrical energy to enlighten the street. The human footsteps can be used as vibration source to generate electrical energy.

  10. Painting biological low-frequency vibrational modes from small peptides to proteins.

    PubMed

    Perticaroli, S; Russo, D; Paolantoni, M; Gonzalez, M A; Sassi, P; Nickels, J D; Ehlers, G; Comez, L; Pellegrini, E; Fioretto, D; Morresi, A

    2015-05-07

    Protein low-frequency vibrational modes are an important portion of a proteins' dynamical repertoire. Yet, it is notoriously difficult to isolate specific vibrational features in the spectra of proteins. Given an appropriately chosen model peptide, and using different experimental conditions, we can simplify the system and gain useful insights into the protein vibrational properties. Combining neutron scattering, depolarized light scattering, and molecular dynamics simulations, we analyse the low frequency vibrations of biological molecules, comparing the results from a small globular protein, lysozyme, and an amphiphilic peptide, NALMA, both in solution and in powder states. Lysozyme and NALMA present similar spectral features in the frequency range between 1 and 10 THz. With the aid of MD simulations, we assign the spectral features to methyl groups' librations (1-5 THz) and hindered torsions (5-10 THz) in NALMA. Our data also show that, while proteins display boson peak vibrations in both powder and solution forms, NALMA exhibits boson peak vibrations in powder form only. This provides insight into the nature of this feature, suggesting a connection of BP collective motions to a characteristic length scale of heterogeneities present in the system. These results provide context for the use of model peptide systems to study protein dynamics; demonstrating both their utility, and the great care that has to be used in extrapolating results observed in powder to solutions.

  11. Modeling, design and analysis of low frequency platform for attenuating micro-vibration in spacecraft

    NASA Astrophysics Data System (ADS)

    Kamesh, D.; Pandiyan, R.; Ghosal, Ashitava

    2010-08-01

    One of the most important factors that affect the pointing of precision payloads and devices in space platforms is the vibration generated due to static and dynamic unbalanced forces of rotary equipments placed in the neighborhood of payload. Generally, such disturbances are of low amplitude, less than 1 kHz, and are termed as 'micro-vibrations'. Due to low damping in the space structure, these vibrations have long decay time and they degrade the performance of payload. This paper addresses the design, modeling and analysis of a low frequency space frame platform for passive and active attenuation of micro-vibrations. This flexible platform has been designed to act as a mount for devices like reaction wheels, and consists of four folded continuous beams arranged in three dimensions. Frequency and response analysis have been carried out by varying the number of folds, and thickness of vertical beam. Results show that lower frequencies can be achieved by increasing the number of folds and by decreasing the thickness of the blade. In addition, active vibration control is studied by incorporating piezoelectric actuators and sensors in the dynamic model. It is shown using simulation that a control strategy using optimal control is effective for vibration suppression under a wide variety of loading conditions.

  12. Passive vibration isolation of reaction wheel disturbances using a low frequency flexible space platform

    NASA Astrophysics Data System (ADS)

    Kamesh, D.; Pandiyan, R.; Ghosal, Ashitava

    2012-03-01

    Reaction wheel assemblies (RWAs) are momentum exchange devices used in fine pointing control of spacecrafts. Even though the spinning rotor of the reaction wheel is precisely balanced to minimize emitted vibration due to static and dynamic imbalances, precision instrument payloads placed in the neighborhood can always be severely impacted by residual vibration forces emitted by reaction wheel assemblies. The reduction of the vibration level at sensitive payloads can be achieved by placing the RWA on appropriate mountings. A low frequency flexible space platform consisting of folded continuous beams has been designed to serve as a mount for isolating a disturbance source in precision payloads equipped spacecrafts. Analytical and experimental investigations have been carried out to test the usefulness of the low frequency flexible platform as a vibration isolator for RWAs. Measurements and tests have been conducted at varying wheel speeds, to quantify and characterize the amount of isolation obtained from the reaction wheel generated vibration. These tests are further extended to other variants of similar design in order to bring out the best isolation for given disturbance loads. Both time and frequency domain analysis of test data show that the flexible beam platform as a mount for reaction wheels is quite effective and can be used in spacecrafts for passive vibration control.

  13. A magnetic-spring-based, low-frequency-vibration energy harvester comprising a dual Halbach array

    NASA Astrophysics Data System (ADS)

    Salauddin, M.; Halim, M. A.; Park, J. Y.

    2016-09-01

    Energy harvesting that uses low-frequency vibrations is attractive due to the availability of such vibrations throughout the ambient environment. Significant power generation at low-frequency vibrations, however, is challenging because the power flow decreases as the frequency decreases; moreover, designing a spring-mass system that is suitable for low-frequency-vibration energy harvesting is difficult. In this work, our proposed device overcomes both of these challenges by using a dual Halbach array and magnetic springs. Each Halbach array concentrates the magnetic-flux lines on one side of the array while suppressing the flux lines on the other side; therefore, a dual Halbach array allows for an interaction between the concentrated magnetic-flux lines and the same coil so that the maximum flux linkage occurs. During the experiment, vibration was applied in a horizontal direction to reduce the gravity effect on the Halbach-array structure. To achieve an increased power generation at low-amplitude and low-frequency vibrations, the magnetic structure of the dual Halbach array and the magnetic springs were optimized in terms of the operating frequency and the power density; subsequently, a prototype was fabricated and tested. The prototype device offers a normalized power density of 133.45 μW cm-3 g-2 that is much higher than those of recently reported electromagnetic energy harvesters; furthermore, it is capable of delivering a maximum average power of 1093 μW to a 44 Ω optimum load, at an 11 Hz resonant frequency and under a 0.5 g acceleration.

  14. A low-frequency vibration energy harvester based on diamagnetic levitation

    NASA Astrophysics Data System (ADS)

    Kono, Yuta; Masuda, Arata; Yuan, Fuh-Gwo

    2017-04-01

    This article presents 3-degree-of-freedom theoretical modeling and analysis of a low-frequency vibration energy harvester based on diamagnetic levitation. In recent years, although much attention has been placed on vibration energy harvesting technologies, few harvesters still can operate efficiently at extremely low frequencies in spite of large potential demand in the field of structural health monitoring and wearable applications. As one of the earliest works, Liu, Yuan and Palagummi proposed vertical and horizontal diamagnetic levitation systems as vibration energy harvesters with low resonant frequencies. This study aims to pursue further improvement along this direction, in terms of expanding maximum amplitude and enhancing the flexibility of the operation direction for broader application fields by introducing a new topology of the levitation system.

  15. Peculiarities of the Third Natural Frequency Vibrations of a Cantilever for the Improvement of Energy Harvesting

    PubMed Central

    Ostasevicius, Vytautas; Janusas, Giedrius; Milasauskaite, Ieva; Zilys, Mindaugas; Kizauskiene, Laura

    2015-01-01

    This paper focuses on several aspects extending the dynamical efficiency of a cantilever beam vibrating in the third mode. A few ways of producing this mode stimulation, namely vibro-impact or forced excitation, as well as its application for energy harvesting devices are proposed. The paper presents numerical and experimental analyses of novel structural dynamics effects along with an optimal configuration of the cantilever beam. The peculiarities of a cantilever beam vibrating in the third mode are related to the significant increase of the level of deformations capable of extracting significant additional amounts of energy compared to the conventional harvester vibrating in the first mode. Two types of a piezoelectric vibrating energy harvester (PVEH) prototype are analysed in this paper: the first one without electrode segmentation, while the second is segmented using electrode segmentation at the strain nodes of the third vibration mode to achieve effective operation at the third resonant frequency. The results of this research revealed that the voltage generated by any segment of the segmented PVEH prototype excited at the third resonant frequency demonstrated a 3.4–4.8-fold increase in comparison with the non-segmented prototype. Simultaneously, the efficiency of the energy harvester prototype also increased at lower resonant frequencies from 16% to 90%. The insights presented in the paper may serve for the development and fabrication of advanced piezoelectric energy harvesters which would be able to generate a considerably increased amount of electrical energy independently of the frequency of kinematical excitation. PMID:26029948

  16. Estimation of turbine blade natural frequencies from casing pressure and vibration measurements

    NASA Astrophysics Data System (ADS)

    Forbes, Gareth L.; Randall, Robert B.

    2013-04-01

    Non-contact measurement of gas turbine rotor blade vibration is a non-trivial task, with no method available which achieves this aim without some significant draw-backs . This paper presents a truly non-contact method to estimate rotor blade natural frequencies from casing vibration measurements at a single engine operating speed. An analytical model is derived to simulate the internal casing pressure in a turbine engine including the effects of blade vibration on this pressure signal. It is shown that the internal pressure inside a turbine contains measureable information about the rotor blade natural frequencies and in-turn the casing vibration response also contains this information. The results presented herein show the residual, pressure and casing vibration, spectrum can be used to determine the rotor blade natural frequencies with validation provided for the analytical model by experimental measurements on a simplified test rig. A simulated blade fault in one of the rotor blades is introduced with successful estimation of the simulated faulty blade natural frequency.

  17. Measurement of small mechanical vibrations of brain tissue exposed to extremely-low-frequency electric fields

    SciTech Connect

    Spiegel, R.J.; Ali, J.S.; Peoples, J.F.; Joines, W.T.

    1986-01-01

    Electromagnetic fields can interact with biological tissue both electrically and mechanically. This study investigated the mechanical interaction between brain tissue and an extremely-low-frequency (ELF) electric field by measuring the resultant vibrational amplitude. The exposure cell is a section of X-band waveguide that was modified by the addition of a center conductor to form a small TEM cell within the waveguide structure. The ELF signal is applied to the center conductor of the TEM cell. The applied ELF electric field generates an electrostrictive force on the surface of the brain tissue. This force causes the tissue to vibrate at a frequency equal to twice the frequency of the applied sinusoidal signal. An X-band signal is fed through the waveguide, scattered by the vibrating sample, and detected by a phrase-sensitive receiver. Using a time-averaging spectrum analyzer, a vibration sensitivity of approximately 0.2 nmpp can be achieved. The amplitude of the brain tissue vibrational frequencies below 50 Hz; between 50 and 200 Hz resonant phenomena were observed; and above 200 Hz the amplitude fall-off is rapid.

  18. A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

    SciTech Connect

    Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun

    2014-10-15

    While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm{sup 3}, which was designed for a target frequency of as low as 100 Hz.

  19. A small-form-factor piezoelectric vibration energy harvester using a resonant frequency-down conversion

    NASA Astrophysics Data System (ADS)

    Sun, Kyung Ho; Kim, Young-Cheol; Kim, Jae Eun

    2014-10-01

    While environmental vibrations are usually in the range of a few hundred Hertz, small-form-factor piezoelectric vibration energy harvesters will have higher resonant frequencies due to the structural size effect. To address this issue, we propose a resonant frequency-down conversion based on the theory of dynamic vibration absorber for the design of a small-form-factor piezoelectric vibration energy harvester. The proposed energy harvester consists of two frequency-tuned elastic components for lowering the first resonant frequency of an integrated system but is so configured that an energy harvesting beam component is inverted with respect to the other supporting beam component for a small form factor. Furthermore, in order to change the unwanted modal characteristic of small separation of resonant frequencies, as is the case with an inverted configuration, a proof mass on the supporting beam component is slightly shifted toward a second proof mass on the tip of the energy harvesting beam component. The proposed small-form-factor design capability was experimentally verified using a fabricated prototype with an occupation volume of 20 × 39 × 6.9 mm3, which was designed for a target frequency of as low as 100 Hz.

  20. Stiffness Corrections for the Vibration Frequency of a Stretched Wire

    ERIC Educational Resources Information Center

    Hornung, H. G.; Durie, M. J.

    1977-01-01

    Discusses the need of introducing corrections due to wire stiffness arising from end constraints and wire axis distribution curvature in the measurement of ac electrical frequency by exciting transverse standing waves in a stretched steel wire. (SL)

  1. The Effect of the Weight Scheme on DFT Vibrational Frequencies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles; Ricca, Alessandra

    1999-01-01

    All-electron B3LYP harmonic frequencies of Ge2H5 and Ge2H6 are computed for several choices of grid and using both the Becke and the Stratmann, Scuseria, and Frisch atomic partition functions (weight scheme). For large grids, the results are independent of the weighting scheme. The lowest frequency mode is much more stable with respect to the number of grid points when the Stratmann, Scuseria, and Frisch weights are used.

  2. Broadband electromagnetic power harvester from vibrations via frequency conversion by impact oscillations

    SciTech Connect

    Yuksek, N. S.; Almasri, M.; Feng, Z. C.

    2014-09-15

    In this paper, we propose an electromagnetic power harvester that uses a transformative multi-impact approach to achieve a wide bandwidth response from low frequency vibration sources through frequency-up conversion. The device consists of a pick-up coil, fixed at the free edge of a cantilever beam with high resonant frequency, and two cantilever beams with low excitation frequencies, each with an impact mass attached at its free edge. One of the two cantilevers is designed to resonate at 25 Hz, while the other resonates at 50 Hz within the range of ambient vibration frequency. When the device is subjected to a low frequency vibration, the two low-frequency cantilevers responded by vibrating at low frequencies, and thus their thick metallic masses made impacts with the high resonance frequency cantilever repeatedly at two locations. This has caused it along with the pick-up coil to oscillate, relative to the permanent magnet, with decaying amplitude at its resonance frequency, and results in a wide bandwidth response from 10 to 63 Hz at 2 g. A wide bandwidth response between 10–51 Hz and 10–58 Hz at acceleration values of 0.5 g and 2 g, respectively, were achieved by adjusting the impact cantilever frequencies closer to each other (25 Hz and 45 Hz). A maximum output power of 85 μW was achieved at 5 g at 30 Hz across a load resistor, 2.68 Ω.

  3. A semi-continuum model on vibration frequency of silicon nanowires in <111> orientation

    SciTech Connect

    Yu, Hong Chen, Hong-Bo

    2016-06-15

    In this article, a new semi-continuum model is built to describe the fundamental vibration frequency of the silicon nanowires in <111> orientation. The Keating potential model and the discrete nature in the width and the thickness direction of the silicon nanowires in <111> orientation are applied in the new semi-continuum model. Based on the Keating model and the principle of conservation of energy, the vibration frequency of the silicon nanowires with the triangle, the rhombus, and the hexagon cross sections are derived. It is indicated that the calculation results based on this new model are accordant with the simulation results of the software based on molecular dynamics (MD).

  4. The geometry and frequency content of planetary gear single-mode vibration

    NASA Astrophysics Data System (ADS)

    Cooley, Christopher G.; Parker, Robert G.

    2013-10-01

    The geometry and frequency content of single-mode vibrations of spur planetary gears are investigated in the rotating carrier-fixed and the stationary reference frames. Planetary gears with equally spaced or diametrically opposed planets have exactly three mode types, called planet, rotational, and translational modes. The properties of these vibration modes lead to response with well-defined geometry. The frequency content of the motion differs between the rotating carrier-fixed and stationary bases. The results from this work assist the analysis of experimental planetary gear measurements.

  5. Geometric origin of excess low-frequency vibrational modes in weakly connected amorphous solids

    NASA Astrophysics Data System (ADS)

    Wyart, M.; Nagel, S. R.; Witten, T. A.

    2005-11-01

    Glasses have an excess number of low-frequency vibrational modes in comparison with most crystalline solids. We show that such a feature necessarily occurs in solids with low coordination. In particular, we analyze the density D(ω) of normal-mode frequencies ω and the nature of the low-frequency normal modes of a recently simulated system (O'Hern C., Silbert L. E., Liu A. J. and Nagel S. R., Phys. Rev. E, 68 (2003) 011306) comprised of weakly compressed spheres at zero temperature. We account for the observed a) convergence of D(ω) toward a non-zero constant as the frequency goes to zero, b) appearance of a low-frequency cutoff ω*, and c) power law increase of ω* with compression. We introduce a length scale l* which characterizes the vibrational modes that appear at ω*.

  6. Intramolecular vibrations in low-frequency normal modes of amino acids: L-alanine in the neat solid state.

    PubMed

    Zhang, Feng; Wang, Houng-Wei; Tominaga, Keisuke; Hayashi, Michitoshi

    2015-03-26

    This paper presents a theoretical analysis of the low-frequency phonons of L-alanine by using the solid-state density functional theory at the Γ point. We are particularly interested in the intramolecular vibrations accessing low-frequency phonons via harmonic coupling with intermolecular vibrations. A new mode-analysis method is introduced to quantify the vibrational characteristics of such intramolecular vibrations. We find that the torsional motions of COO(-) are involved in low-frequency phonons, although COO(-) is conventionally assumed to undergo localized torsion. We also find the broad distributions of intramolecular vibrations relevant to important functional groups of amino acids, e.g., the COO(-) and NH3(+) torsions, in the low-frequency phonons. The latter finding is illustrated by the concept of frequency distribution of vibrations. These findings may lead to immediate implications in other amino acid systems.

  7. Higher-order vibrational mode frequency tuning utilizing fishbone-shaped microelectromechanical systems resonator

    NASA Astrophysics Data System (ADS)

    Suzuki, Naoya; Tanigawa, Hiroshi; Suzuki, Kenichiro

    2013-04-01

    Resonators based on microelectromechanical systems (MEMS) have received considerable attention for their applications for wireless equipment. The requirements for this application include small size, high frequency, wide bandwidth and high portability. However, few MEMS resonators with wide-frequency tuning have been reported. A fishbone-shaped resonator has a resonant frequency with a maximum response that can be changed according to the location and number of several exciting electrodes. Therefore, it can be expected to provide wide-frequency tuning. The resonator has three types of electrostatic forces that can be generated to deform a main beam. We evaluate the vibrational modes caused by each exciting electrodes by comparing simulated results with measured ones. We then successfully demonstrate the frequency tuning of the first to fifth resonant modes by using the algorithm we propose here. The resulting frequency tuning covers 178 to 1746 kHz. In addition, we investigate the suppression of the anchor loss to enhance the Q-factor. An experiment shows that tapered-shaped anchors provide a higher Q-factor than rectangular-shaped anchors. The Q-factor of the resonators supported by suspension beams is also discussed. Because the suspension beams cause complicated vibrational modes for higher frequencies, the enhancement of the Q-factor for high vibrational modes cannot be obtained here. At present, the tapered-anchor resonators are thought to be most suitable for frequency tuning applications.

  8. Influence of low-frequency vibrations on blood flow improvement in human's limbs.

    PubMed

    Venslauskas, Mantas; Ostasevicius, Vytautas; Vilkinis, Paulius

    2017-01-01

    The fundamental cause of diabetic limbs' problem is insufficient blood supply. The aim of the current work was to experimentally and numerically investigate the blood flow velocity and pressure changes in the channel during vibrational excitation. The micro-scale Particle Image Velocimetry (μPIV) technique as well as corresponding numerical channel model in COMSOL Multiphysics software were used to investigate the influence of external vibrations. Momentum upstream flow were noted on the fluid that was influenced by vibrations. Furthermore, momentum flow velocity increased by more than 3 times in both experimentally and theoretically. These results show that suggested novel low-frequency vibrational excitation method should be investigated in clinical studies in case of improvement of blood circulation in human limbs.

  9. Effect of intermediate-frequency vibrations on the probability of the elementary charge-tansfer act

    SciTech Connect

    Belousov, A.A.; Kuznetsov, A.M.

    1986-01-01

    The probability of nonadiabatic transitions can be calculated in the harmonic approximation for any sort of vibrational spectrum of a system from the quantum-mechanical theory of charge-transfer processes in condensed media as it exists today. For adiabatic transitions, the largest difficulties for a rigorous theoretical examination arise in the case when the system has vibrations with intermediate frequencies. It is the aim of this work to estimate the effect of an intermediate local vibration on the preexponential factor and on the activation energy while assuming that transitions between terms corresponding to different vibrational states of this degree of freedom occur independently, and allowing for the possibility that the transitions between terms are adiabatic in character. The authors report results obtained in numerical computer calculations for different values of the parameters.

  10. Vibrational Coupling at the Topmost Surface of Water Revealed by Heterodyne-Detected Sum Frequency Generation Spectroscopy.

    PubMed

    Suzuki, Yudai; Nojima, Yuki; Yamaguchi, Shoichi

    2017-03-15

    Unraveling vibrational coupling is the key to consistently interpret vibrational spectra of complex molecular systems. The vibrational spectrum of the water surface heavily suffers from vibrational coupling, which hinders complete understanding of the molecular structure and dynamics of the water surface. Here we apply heterodyne-detected sum frequency generation spectroscopy to the water surface and accomplish the assignment of a weak vibrational band located at the lower energy side of the free OH stretch. We find that this band is due to a combination mode of the hydrogen-bonded OH stretch and a low-frequency intermolecular vibration, and this combination band appears in the surface vibrational spectrum through anharmonic vibrational coupling that takes place exclusively at the topmost surface.

  11. Robust vibration isolation via frequency-shaped sliding control and modal decomposition

    NASA Astrophysics Data System (ADS)

    Zuo, Lei; Slotine, Jean-Jacques E.

    2005-08-01

    A robust controller design is proposed for multi-degree-of-freedom active vibration isolation, which accounts for plant uncertainties and payload disturbances using frequency-shaped sliding control. First, modal decomposition is employed to rewrite the MIMO vibration control problem as a combination of individual SISO control problems in modal coordinates. The modal parameters for decomposition and modelling can be extracted from theoretical or experimental modal analysis. Next, the target frequency-domain performance of isolation, in this case a skyhook model, is recast as a frequency-shaped sliding surface. The practical effects of boundary layer approximation in the resulting controller design are examined. Simulations illustrate that the ideal skyhook effect can indeed be robustly achieved. The frequency-shaped manifold is also extended to adaptive vibration isolation without using model reference. This algorithm has been recently verified by experiments (IEEE Transactions on Control Systems Technology (2005), in press), and has been demonstrated very effective for vibration isolation. The paper also shows, more generally, that the design of a frequency-shaped sliding surface is formally equivalent to a feedback-feedforward compensation problem. Nonlinear target dynamics of the same order as the nominal plant can also be attained.

  12. Detailed Vibration Analysis of Pinion Gear with Time-Frequency Methods

    NASA Technical Reports Server (NTRS)

    Mosher, Marianne; Pryor, Anna H.; Lewicki, David G.

    2003-01-01

    In this paper, the authors show a detailed analysis of the vibration signal from the destructive testing of a spiral bevel gear and pinion pair containing seeded faults. The vibration signal is analyzed in the time domain, frequency domain and with four time-frequency transforms: the Short Time Frequency Transform (STFT), the Wigner-Ville Distribution with the Choi-Williams kernel (WV-CW), the Continuous Wavelet' Transform (CWT) and the Discrete Wavelet Transform (DWT). Vibration data of bevel gear tooth fatigue cracks, under a variety of operating load levels and damage conditions, are analyzed using these methods. A new metric for automatic anomaly detection is developed and can be produced from any systematic numerical representation of the vibration signals. This new metric reveals indications of gear damage with all of the time-frequency transforms, as well as time and frequency representations, on this data set. Analysis with the CWT detects changes in the signal at low torque levels not found with the other transforms. The WV-CW and CWT use considerably more resources than the STFT and the DWT. More testing of the new metric is needed to determine its value for automatic anomaly detection and to develop fault detection methods for the metric.

  13. First-principles calculations on anharmonic vibrational frequencies of polyethylene and polyacetylene in the Gamma approximation.

    PubMed

    Keçeli, Murat; Hirata, So; Yagi, Kiyoshi

    2010-07-21

    The frequencies of the infrared- and/or Raman-active (k=0) vibrations of polyethylene and polyacetylene are computed by taking account of the anharmonicity in the potential energy surfaces (PESs) and the resulting phonon-phonon couplings explicitly. The electronic part of the calculations is based on Gaussian-basis-set crystalline orbital theory at the Hartree-Fock and second-order Møller-Plesset (MP2) perturbation levels, providing one-, two-, and/or three-dimensional slices of the PES (namely, using the so-called n-mode coupling approximation with n=3), which are in turn expanded in the fourth-order Taylor series with respect to the normal coordinates. The vibrational part uses the vibrational self-consistent field, vibrational MP2, and vibrational truncated configuration-interaction (VCI) methods within the Gamma approximation, which amounts to including only k=0 phonons. It is shown that accounting for both electron correlation and anharmonicity is essential in achieving good agreement (the mean and maximum absolute deviations less than 50 and 90 cm(-1), respectively, for polyethylene and polyacetylene) between computed and observed frequencies. The corresponding values for the calculations including only one of such effects are in excess of 120 and 300 cm(-1), respectively. The VCI calculations also reproduce semiquantitatively the frequency separation and intensity ratio of the Fermi doublet involving the nu(2)(0) fundamental and nu(8)(pi) first overtone in polyethylene.

  14. Frequency weighting for vibration-induced white finger compatible with exposure-response models.

    PubMed

    Brammer, Anthony J; Pitts, Paul M

    2012-01-01

    An analysis has been performed to derive a frequency weighting for the development of vibration-induced white finger (VWF). It employs a model to compare health risks for pairs of population groups that are selected to have similar health outcomes from operating power tools or machines with markedly different acceleration spectra (rock drills, chain saws, pavement breakers and motorcycles). The model defines the Relative Risk, RR(f(trial)), which is constructed from the ratio of daily exposures and includes a trial frequency weighting that is applied to the acceleration spectra. The trial frequency weighting consists of a frequency-independent primary frequency range, and subordinate frequency ranges in which the response to vibration diminishes, with cut-off frequencies that are changed to influence the magnitude of RR(f(trial)). The frequency weighting so derived when RR(f(trial)) = 1 is similar to those obtained by other methods (W(hf), W(hT)). It consists of a frequency independent range from about 25 Hz to 500 Hz (-3 dB frequencies), with an amplitude cut-off rate of 12 dB/octave below 25 Hz and above 500 Hz. The range is compatible with studies of vasoconstriction in persons with VWF. The results provide further evidence that the ISO frequency weighting may be inappropriate for assessing the risk of developing VWF.

  15. Vibrational dephasing and frequency shifts of hydrogen-bonded pyridine-water complexes

    NASA Astrophysics Data System (ADS)

    Kalampounias, A. G.; Tsilomelekis, G.; Boghosian, S.

    2015-01-01

    In this paper we present the picosecond vibrational dynamics and Raman shifts of hydrogen-bonded pyridine-water complexes present in aqueous solutions in a wide concentration range from dense to extreme dilute solutions. We studied the vibrational dephasing and vibrational frequency modulation by calculating time correlation functions of vibrational relaxation by fits in the frequency domain. The concentration induced variations in bandwidths, band frequencies and characteristic dephasing times have been estimated and interpreted as effects due to solute-solvent interactions. The time-correlation functions of vibrational dephasing were obtained for the ring breathing mode of both "free" and hydrogen-bonded pyridine molecules and it was found that sufficiently deviate from the Kubo model. There is a general agreement in the whole concentration range with the modeling proposed by the Rothschild approach, which applies to complex liquids. The results have shown that the reorientation of pyridine aqueous solutions is very slow and hence in both scattering geometries only vibrational dephasing is probed. It is proposed that the spectral changes depend on the perturbations induced by the dynamics of the water molecules in the first hydration cell and water in bulk, while at extreme dilution conditions, the number of bulk water molecules increases and the interchange between molecules belonging to the first hydration cell may not be the predominant modulation mechanism. The evolution of several parameters, such as the characteristic times, the percentage of Gaussian character in the peak shape and the a parameter are indicative of drastic variations at extreme dilution revealing changes in the vibrational relaxation of the pyridine complexes in the aqueous environment. The higher dilution is correlated to diffusion of water molecules into the reference pyridine system in agreement with the jump diffusion model, while at extreme dilutions, almost all pyridine molecules are

  16. Investigation of a vibration-damping unit for reduction in low-frequency vibrations of electric motors

    NASA Technical Reports Server (NTRS)

    Grigoryey, N. V.; Fedorovich, M. A.

    1973-01-01

    The vibroacoustical characteristics of different types of electric motors are discussed. It is shown that the basic source of low frequency vibrations is rotor unbalance. A flexible damping support, with an antivibrator, is used to obtain the vibroacoustical effect of reduction in the basic harmonic of the electric motor. A model of the electric motor and the damping apparatus is presented. Mathematical models are developed to show the relationships of the parameters. The basic purpose in using a calculation model id the simultaneous replacement of the exciting force created by the rotor unbalance and its inertial rigidity characteristics by a limiting kinematic disturbance.

  17. Investigation of a vibration-damping unit for reduction in low-frequency vibrations of electric motors

    NASA Technical Reports Server (NTRS)

    Grigoryey, N. V.; Fedorovich, M. A.

    1973-01-01

    The vibroacoustical characteristics of different types of electric motors are discussed. It is shown that the basic source of low frequency vibrations is rotor unbalance. A flexible damping support, with an antivibrator, is used to obtain the vibroacoustical effect of reduction in the basic harmonic of the electric motor. A model of the electric motor and the damping apparatus is presented. Mathematical models are developed to show the relationships of the parameters. The basic purpose in using a calculation model id the simultaneous replacement of the exciting force created by the rotor unbalance and its inertial rigidity characteristics by a limiting kinematic disturbance.

  18. Application of analysis techniques for low frequency interior noise and vibration of commercial aircraft

    NASA Technical Reports Server (NTRS)

    Landmann, A. E.; Tillema, H. F.; Macgregor, G. R.

    1992-01-01

    Finite element analysis (FEA), statistical energy analysis (SEA), and a power flow method (computer program PAIN) were used to assess low frequency interior noise associated with advanced propeller installations. FEA and SEA models were used to predict cabin noise and vibration and evaluate suppression concepts for structure-borne noise associated with the shaft rotational frequency and harmonics (less than 100 Hz). SEA and PAIN models were used to predict cabin noise and vibration and evaluate suppression concepts for airborne noise associated with engine radiated propeller tones. Both aft-mounted and wing-mounted propeller configurations were evaluated. Ground vibration test data from a 727 airplane modified to accept a propeller engine were used to compare with predictions for the aft-mounted propeller. Similar data from the 767 airplane was used for the wing-mounted comparisons.

  19. The Possible Interstellar Anion CH2CN-: Spectroscopic Constants, Vibrational Frequencies, and Other Considerations

    NASA Technical Reports Server (NTRS)

    Fortenberry, Ryan C.; Crawford, T. Daniel; Lee, Timothy J.

    2012-01-01

    The A 1B1 <-1A0 excitation into the dipole-bound state of the cyanomethyl anion (CH2CN??) has been hypothesized as the carrier for one di use interstellar band. However, this particular molecular system has not been detected in the interstellar medium even though the related cyanomethyl radical and the isoelectronic ketenimine molecule have been found. In this study we are employing the use of proven quartic force elds and second-order vibrational perturbation theory to compute accurate spectroscopic constants and fundamental vibrational frequencies for X 1A0 CH2CN?? in order to assist in laboratory studies and astronomical observations. Keywords: Astrochemistry, ISM: molecular anions, Quartic force elds, Rotational constants, Vibrational frequencies

  20. Frequencies and Normal Modes of Vibration of Benz[a]anthracene Radical Ions

    NASA Astrophysics Data System (ADS)

    Kubba, Rehab M.; Al-ani, Raghida I.; Shanshal, Muthana

    2005-03-01

    MINDO/3-FORCES calculations were carried out for the radical ions of benz[a]anthracene. Both ions exhibit Cs symmetry with C-C bond alternation in all four rings. The obtained equilibrium geometry was applied for the calculation of all 3N - 6 vibration frequencies of each ion, and for the analysis of their normal coordinates. The so calculated frequencies of the radical cation were close to the experimental frequencies and those of the ab initio calculations. They fall in the ranges νCHstr. (3034 - 3087 cm-1), νCCstr. (1237 - 1609 cm-1), δCH (1142 - 1216 cm-1). Interesting correlations could be obtained for the frequencies of similar vibrations, e. g. νsymCHstr. >νasymCHstr. Exception is the frequency of vibration of CHα in ring A for the radical cation and the same bond in ring D for the radical anion. The vibration frequencies for the CH bonds depend on the σ -electron densities of the corresponding carbon atoms, i. e. νCH.+str. >νCHstr. >νCH.-str., where σ -ρĊ+ >σ -ρC >σ -ρĊ- . For the C-C stretching vibrations the relation ν(C-C)str. >ν(C-C).-str. >ν(C-C).+str. holds, with the exception of the Cβ -Cβ bond, for which the relation ν(C-C)str. >ν(C-C).+str. >ν(C-C).-str. is found. As for the in-plane and out of-plane deformations, the following general correlations δ (CH) >δ (CH).- >δ (CH).+ and γ (CC) >γ (CC).- >γ (CC).+.

  1. Frequency weightings for fore-and-aft vibration at the back: effect of contact location, contact area, and body posture.

    PubMed

    Morioka, Miyuki; Griffin, Michael J

    2010-01-01

    Fore-and-aft vibration of a backrest can influence discomfort and the risk of injury associated with whole-body vibration. Relevant standards (BS 6841:1987 and ISO2631-1:1997) recommend the W(c) frequency weighting for evaluating fore-and-aft vibration of backrests, but do not specify the precise location for measuring vibration. This study determined equivalent comfort contours for fore-and-aft vibration of the backs of seated persons from 2 to 80 Hz using the method of magnitude estimation, examining the effect of input location, contact area, and body posture. The equivalent comfort contours indicate decreased sensitivity to vibration acceleration at frequencies greater than 8 Hz. Equivalent comfort contours with a full backrest were similar to those with contact at only the highest location on the back. The derived frequency weightings are broadly consistent with frequency weighting W(c) but suggest somewhat greater sensitivity at frequencies greater than 30 Hz and vary in shape with changes in vibration magnitude. It is concluded that with low and moderate magnitudes of vibration the severity of fore-and-aft vibration of a backrest can be assessed from the frequency-weighted fore-and-aft acceleration measured at the highest point of contact between the backrest and the body if the frequency weighting W(c) is employed in the evaluation.

  2. Molecular-level mechanisms of vibrational frequency shifts in a polar liquid.

    PubMed

    Morales, Christine M; Thompson, Ward H

    2011-06-16

    A molecular-level analysis of the origins of the vibrational frequency shifts of the CN stretching mode in neat liquid acetonitrile is presented. The frequency shifts and infrared spectrum are calculated using a perturbation theory approach within a molecular dynamics simulation and are in good agreement with measured values reported in the literature. The resulting instantaneous frequency of each nitrile group is decomposed into the contributions from each molecule in the liquid and by interaction type. This provides a detailed picture of the mechanisms of frequency shifts, including the number of surrounding molecules that contribute to the shift, the relationship between their position and relative contribution, and the roles of electrostatic and van der Waals interactions. These results provide insight into what information is contained in infrared (IR) and Raman spectra about the environment of the probed vibrational mode. © 2011 American Chemical Society

  3. Synthesis of vibration systems, having group symmetry or quasi-symmetry, according to the frequency spectrum

    NASA Technical Reports Server (NTRS)

    Andryushkevichyus, A. I.; Ragulskis, K. M.

    1973-01-01

    Torsional vibration systems, with finite numbers of degrees of freedom are investigated. In designing such systems, it is important to select parameters, so that the frequency spectrum of the natural vibrations is beyond the limits of the resonance danger region. In the case when the system has a large number of degrees of freedom, calculation of its natural frequencies, as well as tuning out the resonance danger zones is laborious. When the system being investigated has one group symmetry or another, solution of the problem mentioned above is facilitated, as a consequence of breaking down the frequency equations into several, which are smaller in size. An algorithm is given for tuning out the natural frequency spectrum from the forbidden region, by means of varying the rigidity of systems having group symmetries or group quasi-symmetries.

  4. Note: A component-level frequency tunable isolator for vibration-sensitive chips using SMA beams.

    PubMed

    Zhang, Xiaoyong; Ding, Xin; Wu, Di; Qi, Junlei; Wang, Ruixin; Lu, Siwei; Yan, Xiaojun

    2016-06-01

    This note presents a component-level frequency tunable isolator for vibration-sensitive chips. The isolator employed 8 U-shaped shape memory alloy (SMA) beams to support an isolation island (used for mounting chips). Due to the temperature-induced Young's modulus variation of SMA, the system stiffness of the isolator can be controlled through heating the SMA beams. In such a way, the natural frequency of the isolator can be tuned. A prototype was fabricated to evaluate the concept. The test results show that the natural frequency of the isolator can be tuned in the range of 64 Hz-97 Hz by applying different heating strategies. Moreover, resonant vibration can be suppressed significantly (the transmissibility decreases about 65% near the resonant frequency) using a real-time tuning method.

  5. Note: A component-level frequency tunable isolator for vibration-sensitive chips using SMA beams

    SciTech Connect

    Zhang, Xiaoyong E-mail: yanxiaojun@buaa.edu.cn; Yan, Xiaojun E-mail: yanxiaojun@buaa.edu.cn; Ding, Xin; Wu, Di; Qi, Junlei; Wang, Ruixin; Lu, Siwei

    2016-06-15

    This note presents a component-level frequency tunable isolator for vibration-sensitive chips. The isolator employed 8 U-shaped shape memory alloy (SMA) beams to support an isolation island (used for mounting chips). Due to the temperature-induced Young’s modulus variation of SMA, the system stiffness of the isolator can be controlled through heating the SMA beams. In such a way, the natural frequency of the isolator can be tuned. A prototype was fabricated to evaluate the concept. The test results show that the natural frequency of the isolator can be tuned in the range of 64 Hz–97 Hz by applying different heating strategies. Moreover, resonant vibration can be suppressed significantly (the transmissibility decreases about 65% near the resonant frequency) using a real-time tuning method.

  6. Low frequency vibration approach for assessing performance of wood floor systems

    Treesearch

    Xiping Wang; Robert J. Ross; Michael O. Hunt; John R. Erickson; John W. Forsman

    2005-01-01

    The primary means of inspecting buildings and other structures is to evaluate each structure member individually. This is a time-consuming and expensive process, particularly if sheathing or other covering materials must be removed to access the structural members. The objective of this study was to determine if a low frequency vibration method could be used to...

  7. Low Frequency Vibration approach to asess the Performance of wood structural Systems

    Treesearch

    Xiping Wang; Robert J. Ross; Michael O. Hunt

    2004-01-01

    The primary means of inspecting buildings and other structures is to evaluate each structure member individually. This is a time consuming process that is expensive, particularly if sheathing or other covering materials must be removed to access the structural members. This paper presents an effort to use a low frequency vibration method for assessing the structural...

  8. A New Ultra-low Frequency Passive Vertical Vibration Isolation System

    NASA Astrophysics Data System (ADS)

    Zhao, Peng-Fei; Huang, Yu-Ying; Tang, Meng-Xi

    2002-02-01

    A new ultra-low frequency passive vertical vibration isolation system is constructed by connecting the torsion spring isolator with a reverse pendulum. The theoretical analysis shows that the new system can achieve a much longer resonant period and have a smaller size than the current torsion spring isolators with the same geometric parameters.

  9. Dependence of local sound vibration on time frequency in a monolithic array transducer

    SciTech Connect

    Saiga, N.; Suzuki, T.

    1982-02-01

    An approach of increasing spatial resolution in a monolithic array transducer was carried out which utilized the thickness vibration at frequencies slightly lower than the resonance band. At those frequencies, the optical probing manifested that an usual spatial impulse response shifted into a more sharp and monotonously damping one with a peak amplitude comparable to those in resonance. An actual imaging as a receiving array demonstrated the improvement of spatial resolution and the high uniformity of image contrast.

  10. Vibrational Frequencies of Halogen Atoms Adsorbed on Silver Metal Surfaces.

    DTIC Science & Technology

    1980-07-17

    TO Ct/Ag (100) Crystalline AgC£ has the face centered cubic structure , with four molecules per unit cell and a lattice constant of 5.547 A. 43 Jones...in the absence of dipolar coupling within the crystal. According to Fox and Hexter,42 (L"d is given by W 2-h + p2 (6) for the face centered cubic ... structure found for AgF, AgCR, AgBr, and AqI (phase III). ust is the transverse optic mode frequency in the single crystal, p is magnitude of the

  11. Low-frequency vibrational modes and infrared absorbance of red, blue and green opsin.

    PubMed

    Thirumuruganandham, Saravana Prakash; Urbassek, Herbert M

    2009-08-01

    Vibrational excitations of low-frequency collective modes are essential for functionally important conformational transitions in proteins. We carried out an analysis of the low-frequency modes in the G protein coupled receptors (GPCR) family of cone opsins based on both normal-mode analysis and molecular dynamics (MD) simulations. Power spectra obtained by MD can be compared directly with normal modes. In agreement with existing experimental evidence related to transmembrane proteins, cone opsins have functionally important transitions that correspond to approximately 950 modes and are found below 80 cm(-1). This is in contrast to bacteriorhodopsin and rhodopsin, where the important low-frequency transition modes are below 50 cm(-1). We find that the density of states (DOS) profile of blue opsin in a solvent (e.g. water) has increased populations in the very lowest frequency modes (<15 cm(-1)); this is indicative of the increased thermostability of blue opsin. From our work we found that, although light absorption behaves differently in blue, green and red opsins, their low-frequency vibrational motions are similar. The similarities and differences in the domain motions of blue, red and green opsins are discussed for several representative modes. In addition, the influence of the presence of a solvent is reported and compared with vacuum spectra. We thus demonstrate that terahertz spectroscopy of low-frequency modes might be relevant for identifying those vibrational degrees of freedom that correlate to known conformational changes in opsins.

  12. Eulerian frequency analysis of structural vibrations from high-speed video

    NASA Astrophysics Data System (ADS)

    Venanzoni, Andrea; De Ryck, Laurent; Cuenca, Jacques

    2016-06-01

    An approach for the analysis of the frequency content of structural vibrations from high-speed video recordings is proposed. The techniques and tools proposed rely on an Eulerian approach, that is, using the time history of pixels independently to analyse structural motion, as opposed to Lagrangian approaches, where the motion of the structure is tracked in time. The starting point is an existing Eulerian motion magnification method, which consists in decomposing the video frames into a set of spatial scales through a so-called Laplacian pyramid [1]. Each scale - or level - can be amplified independently to reconstruct a magnified motion of the observed structure. The approach proposed here provides two analysis tools or pre-amplification steps. The first tool provides a representation of the global frequency content of a video per pyramid level. This may be further enhanced by applying an angular filter in the spatial frequency domain to each frame of the video before the Laplacian pyramid decomposition, which allows for the identification of the frequency content of the structural vibrations in a particular direction of space. This proposed tool complements the existing Eulerian magnification method by amplifying selectively the levels containing relevant motion information with respect to their frequency content. This magnifies the displacement while limiting the noise contribution. The second tool is a holographic representation of the frequency content of a vibrating structure, yielding a map of the predominant frequency components across the structure. In contrast to the global frequency content representation of the video, this tool provides a local analysis of the periodic gray scale intensity changes of the frame in order to identify the vibrating parts of the structure and their main frequencies. Validation cases are provided and the advantages and limits of the approaches are discussed. The first validation case consists of the frequency content

  13. Eulerian frequency analysis of structural vibrations from high-speed video

    SciTech Connect

    Venanzoni, Andrea; De Ryck, Laurent; Cuenca, Jacques

    2016-06-28

    An approach for the analysis of the frequency content of structural vibrations from high-speed video recordings is proposed. The techniques and tools proposed rely on an Eulerian approach, that is, using the time history of pixels independently to analyse structural motion, as opposed to Lagrangian approaches, where the motion of the structure is tracked in time. The starting point is an existing Eulerian motion magnification method, which consists in decomposing the video frames into a set of spatial scales through a so-called Laplacian pyramid [1]. Each scale — or level — can be amplified independently to reconstruct a magnified motion of the observed structure. The approach proposed here provides two analysis tools or pre-amplification steps. The first tool provides a representation of the global frequency content of a video per pyramid level. This may be further enhanced by applying an angular filter in the spatial frequency domain to each frame of the video before the Laplacian pyramid decomposition, which allows for the identification of the frequency content of the structural vibrations in a particular direction of space. This proposed tool complements the existing Eulerian magnification method by amplifying selectively the levels containing relevant motion information with respect to their frequency content. This magnifies the displacement while limiting the noise contribution. The second tool is a holographic representation of the frequency content of a vibrating structure, yielding a map of the predominant frequency components across the structure. In contrast to the global frequency content representation of the video, this tool provides a local analysis of the periodic gray scale intensity changes of the frame in order to identify the vibrating parts of the structure and their main frequencies. Validation cases are provided and the advantages and limits of the approaches are discussed. The first validation case consists of the frequency content

  14. Low-frequency oscillation in a narrow vibrated granular system

    NASA Astrophysics Data System (ADS)

    Oyarte Gálvez, Loreto; van der Meer, Devaraj

    2015-11-01

    The analogy of the behaviour of granular materials with that of fluids has motivated much appealing research. An important example is a vertically shaken granular bed which exhibits fluid-like behavior, such as the Leidenfrost effect where a dense layer of grains floats on top of a gaseous layer, just like when a liquid droplet floats on its own vapour above a hot plate. When the shaking energy is increased the granular bed transits from the Leidenfrost to the convection state, for which a precursor is expected in the form of an oscillation of the bed as a whole. This precursor was observed numerically like an oscillation in the motion of the dense part, where the frequency of this oscillation is much lower than the frequency of the injected energy, and appears more relevant when the system is getting closer to the convective state. We built a setup that permits the observation of the granular Leidenfrost effect for a wide range of driving parameters. More specifically, a monodisperse granular material is contained in a transparent box and vertically shaken, and a fast camera is used to study its dynamics. The presence of a LFO is directly measured by images analysis and shows a good agreement with the previous numerical and experimental works.

  15. Harvesting Ambient Vibration Energy over a Wide Frequency Range for Self-Powered Electronics.

    PubMed

    Wang, Xiaofeng; Niu, Simiao; Yi, Fang; Yin, Yajiang; Hao, Chenglong; Dai, Keren; Zhang, Yue; You, Zheng; Wang, Zhong Lin

    2017-02-28

    Vibration is one of the most common energy sources in ambient environment. Harvesting vibration energy is a promising route to sustainably drive small electronics. This work introduces an approach to scavenge vibrational energy over a wide frequency range as an exclusive power source for continuous operation of electronics. An elastic multiunit triboelectric nanogenerator (TENG) is rationally designed to efficiently harvest low-frequency vibration energy, which can provide a maximum instantaneous output power density of 102 W·m(-3) at as low as 7 Hz and maintain its stable current outputs from 5 to 25 Hz. A self-charging power unit (SCPU) combining the TENG and a 10 mF supercapacitor gives a continuous direct current (DC) power delivery of 1.14 mW at a power management efficiency of 45.6% at 20 Hz. The performance of the SCPU can be further enhanced by a specially designed power management circuit, with a continuous DC power of 2 mW and power management efficiency of 60% at 7 Hz. Electronics such as a thermometer, hygrometer, and speedometer can be sustainably powered solely by the harvested vibration energy from a machine or riding bicycle. This approach has potential applications in self-powered systems for environment monitoring, machine safety, and transportation.

  16. Active control of high-frequency vibration: Optimisation using the hybrid modelling method

    NASA Astrophysics Data System (ADS)

    Muthalif, Asan G. A.; Langley, Robin S.

    2012-06-01

    This work presents active control of high-frequency vibration using skyhook dampers. The choice of the damper gain and its optimal location is crucial for the effective implementation of active vibration control. In vibration control, certain sensor/actuator locations are preferable for reducing structural vibration while using minimum control effort. In order to perform optimisation on a general built-up structure to control vibration, it is necessary to have a good modelling technique to predict the performance of the controller. The present work exploits the hybrid modelling approach, which combines the finite element method (FEM) and statistical energy analysis (SEA) to provide efficient response predictions at medium to high frequencies. The hybrid method is implemented here for a general network of plates, coupled via springs, to allow study of a variety of generic control design problems. By combining the hybrid method with numerical optimisation using a genetic algorithm, optimal skyhook damper gains and locations are obtained. The optimal controller gain and location found from the hybrid method are compared with results from a deterministic modelling method. Good agreement between the results is observed, whereas results from the hybrid method are found in a significantly reduced amount of time.

  17. Vibrational spectral signatures of crystalline cellulose using high resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS)

    DOE PAGES

    Zhang, Libing; Lu, Zhou; Velarde, Luis; ...

    2015-03-03

    Both the C–H and O–H region spectra of crystalline cellulose were studied using the sub-wavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) for the first time. The resolution of HR-BB-SFG-VS is about 10-times better than conventional scanning SFG-VS and has the capability of measuring the intrinsic spectral lineshape and revealing many more spectral details. With HR-BB-SFG-VS, we found that in cellulose samples from different sources, including Avicel and cellulose crystals isolated from algae Valonia (Iα) and tunicates (Iβ), the spectral signatures in the O–H region were unique for the two allomorphs, i.e. Iα and Iβ, while the spectral signaturesmore » in the C–H regions varied in all samples examined. Even though the origin of the different spectral signatures of the crystalline cellulose in the O–H and C–H vibrational frequency regions are yet to be correlated to the structure of cellulose, these results lead to new spectroscopic methods and opportunities to classify and to understand the basic crystalline structures, as well as variations in polymorphism of the crystalline cellulose.« less

  18. Vibrational spectral signatures of crystalline cellulose using high resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS)

    SciTech Connect

    Zhang, Libing; Lu, Zhou; Velarde, Luis; Fu, Li; Pu, Yunqiao; Ding, Shi-You; Ragauskas, Arthur; Wang, Hong-Fei; Yang, Bin

    2015-03-03

    Both the C–H and O–H region spectra of crystalline cellulose were studied using the sub-wavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) for the first time. The resolution of HR-BB-SFG-VS is about 10-times better than conventional scanning SFG-VS and has the capability of measuring the intrinsic spectral lineshape and revealing many more spectral details. With HR-BB-SFG-VS, we found that in cellulose samples from different sources, including Avicel and cellulose crystals isolated from algae Valonia (Iα) and tunicates (Iβ), the spectral signatures in the O–H region were unique for the two allomorphs, i.e. Iα and Iβ, while the spectral signatures in the C–H regions varied in all samples examined. Even though the origin of the different spectral signatures of the crystalline cellulose in the O–H and C–H vibrational frequency regions are yet to be correlated to the structure of cellulose, these results lead to new spectroscopic methods and opportunities to classify and to understand the basic crystalline structures, as well as variations in polymorphism of the crystalline cellulose.

  19. Vibrational Spectral Signatures of Crystalline Cellulose Using High Resolution Broadband Sum Frequency Generation Vibrational Spectroscopy (HR-BB-SFG-VS)

    SciTech Connect

    Zhang, Libing; Lu, Zhou; Velarde Ruiz Esparza, Luis A.; Fu, Li; Pu, Yunqiao; Ding, Shi-You; Ragauskas, Art J.; Wang, Hongfei; Yang, Bin

    2015-03-03

    Here we reported the first sub-wavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) study on both the C-H and O-H region spectra of crystalline cellulose. HR-BB-SFG-VS has about 10 times better resolution than the conventional scanning SFG-VS and is known to be able to measure the intrinsic spectral lineshape and to resolve much more spectral details. With HR-BB-SFG-VS, we found that in cellulose from different sources, including Avicel and cellulose crystals isolated from algae Valonia (Iα) and tunicates (Iβ), the spectral signatures in the OH regions were unique for different allomorphs, i.e. Iα and Iβ, while the spectral signatures in the C-H regions varied in all samples examined. Even though the origin of the different behaviors of the crystalline cellulose in the O-H and C-H vibrational frequency regions is yet to be correlated to the structure of cellulose, these results provided new spectroscopic methods and opportunities to classify and understand the basic crystalline structure, as well as variations, in polymorphism of the crystalline cellulose structure.

  20. Temperature dependence of vibrational frequency fluctuation of N3- in D2O

    NASA Astrophysics Data System (ADS)

    Tayama, Jumpei; Ishihara, Akane; Banno, Motohiro; Ohta, Kaoru; Saito, Shinji; Tominaga, Keisuke

    2010-07-01

    We have studied the temperature dependence of the vibrational frequency fluctuation of the antisymmetric stretching mode of N3- in D2O by three-pulse infrared (IR) photon echo experiments. IR pump-probe measurements were also carried out to investigate the population relaxation and the orientational relaxation of the same band. It was found that the time-correlation function (TCF) of the frequency fluctuation of this mode is well described by a biexponential function with a quasistatic term. The faster decay component has a time constant of about 0.1 ps, and the slower component varies from 1.4 to 1.1 ps in the temperature range from 283 to 353 K. This result indicates that liquid dynamics related to the frequency fluctuation are not highly sensitive to temperature. We discuss the relationship between the temperature dependence of the vibrational frequency fluctuation and that of the molecular motion of the system to investigate the molecular origin of the frequency fluctuation of the solute. We compare the temperature dependence of the frequency fluctuation with that of other dynamics such as dielectric relaxation of water. In contrast to the Debye dielectric relaxation time of D2O, the two time constants of the TCF of the frequency fluctuation do not exhibit strong temperature dependence. We propose a simple theoretical model for the frequency fluctuation in solutions based on perturbation theory and the dipole-dipole interaction between the vibrational mode of the solute and the solvent molecules. This model suggests that the neighboring solvent molecules in the vicinity of the solute play an important role in the frequency fluctuation. We suggest that the picosecond component of the frequency fluctuation results from structural fluctuation of the hydrogen-bonding network in water.

  1. Quantitative Sum-Frequency Generation Vibrational Spectroscopy of Molecular Surfaces and Interfaces: Lineshape, Polarization and Orientation

    SciTech Connect

    Wang, Hongfei; Velarde, Luis; Gan, Wei; Fu, Li

    2015-04-01

    Sum-frequency generation vibrational spectroscopy (SFG) can provide detailed information and understanding of molecular vibrational spectroscopy, orientational and conformational structure, and interactions of molecular surfaces and interfaces, through quantitative measurement and analysis. In this review, we present the current status and discuss the main developments on the measurement of intrinsic SFG spectral lineshape, formulations for polarization measurement and orientation analysis of the SFG-VS spectra. The main focus is to present a coherent formulation and discuss the main concepts or issues that can help to make SFG-VS a quantitative analytical and research tool in revealing the chemistry and physics of complex molecular surface and interface.

  2. Piezoelectric Instruments of High Natural Frequency Vibration Characteristics and Protection Against Interference by Mass Forces

    NASA Technical Reports Server (NTRS)

    Gohlka, Werner

    1943-01-01

    The exploration of the processes accompanying engine combustion demands quick-responding pressure-recording instruments, among which the piezoelectric type has found widespread use because of its especially propitious properties as vibration-recording instruments for high frequencies. Lacking appropriate test methods, the potential errors of piezoelectric recorders in dynamic measurements could only be estimated up to now. In the present report a test method is described by means of which the resonance curves of the piezoelectric pickup can be determined; hence an instrumental appraisal of the vibration characteristics of piezoelectric recorders is obtainable.

  3. Closed-Form Solutions for Free Vibration Frequencies of Functionally Graded Euler-Bernoulli Beams

    NASA Astrophysics Data System (ADS)

    Chen, W. R.; Chang, H.

    2017-03-01

    The bending vibration of a functionally graded Euler-Bernoulli beam is investigated by the transformed-section method. The material properties of the functionally graded beam (FGB) are assumed to vary across its thickness according to a simple power law. Closed-form solutions for free vibration frequencies of FGBs with classical boundary conditions are derived. Some analytical results are compared with numerical results found in the published literature to verify the accuracy of the model presented, and a good agreement between them is observed.

  4. Low-frequency vibrational modes of viruses used for nanoelectronic self-assemblies

    NASA Astrophysics Data System (ADS)

    Fonoberov, Vladimir A.; Balandin, Alexander A.

    2004-10-01

    Viruses of cylindrical shape have recently attracted attention as templates for assembly of nanostructured materials and as elements of nanoelectronic circuits. We have calculated the dispersion relations for the lowest vibrational frequencies of the tobacco mosaic virus (TMV) and M13 bacteriophage immersed in air or water. The radial breathing modes of TMV and M13 viruses in air (water) are 1.85 cm-1 and 6.42 cm-1 (2.10 cm-1 and 6.12 cm-1), respectively. Elastic vibrations of the two viruses in water are damped with the quality factor of 3.6 for the radial breathing modes.

  5. [Pulsed low-frequency electrotherapy of vibration disease associated with osteoarthrosis].

    PubMed

    Chudinova, O A; Fedorov, A A; Venediktov, D L; Samokhvalova, G N; Il'ina, M I; Budlianskaia, S V

    2010-01-01

    The study involving 185 patients with vibration disease and concomitant osteoarthrosis has demonstrated the positive influence of pulsed low-frequency currents in combination with hydrogen sulphide baths on the clinical course of the disease. This combined therapy produced good immediate and late post-treatment results. The data obtained suggest high efficiency of differential application of complex-modulated pulsed and fluctuating currents in patients with vibration disease. It is concluded that amplipulse therapy is the method of choice for the management of this pathology in the absence of apparatuses emitting pulsed currents in the running way regime.

  6. Orientations of nonlocal vibrational modes from combined experimental and theoretical sum frequency spectroscopy

    NASA Astrophysics Data System (ADS)

    Chase, Hilary M.; Chen, Shunli; Fu, Li; Upshur, Mary Alice; Rudshteyn, Benjamin; Thomson, Regan J.; Wang, Hong-Fei; Batista, Victor S.; Geiger, Franz M.

    2017-09-01

    Inferring molecular orientations from vibrational sum frequency generation (SFG) spectra is challenging in polarization combinations that result in low signal intensities, or when the local point group symmetry approximation fails. While combining experiments with density functional theory (DFT) could overcome this problem, the scope of the combined method has yet to be established. Here, we assess its feasibility of determining the distributions of molecular orientations for one monobasic ester, two epoxides and three alcohols at the vapor/fused silica interface. We find that molecular orientations of nonlocal vibrational modes cannot be determined using polarization-resolved SFG measurements alone.

  7. Two-dimensional resonance frequency tuning approach for vibration-based energy harvesting

    NASA Astrophysics Data System (ADS)

    Dong, Lin; Prasad, M. G.; Fisher, Frank T.

    2016-06-01

    Vibration-based energy harvesting seeks to convert ambient vibrations to electrical energy and is of interest for, among other applications, powering the individual nodes of wireless sensor networks. Generally it is desired to match the resonant frequencies of the device to the ambient vibration source to optimize the energy harvested. This paper presents a two-dimensionally (2D) tunable vibration-based energy harvesting device via the application of magnetic forces in two-dimensional space. These forces are accounted for in the model separately, with the transverse force contributing to the transverse stiffness of the system while the axial force contributes to a change in axial stiffness of the beam. Simulation results from a COMSOL magnetostatic 3D model agree well with the analytical model and are confirmed with a separate experimental study. Furthermore, analysis of the three possible magnetization orientations between the fixed and tuning magnets shows that the transverse parallel magnetization orientation is the most effective with regards to the proposed 2D tuning approach. In all cases the transverse stiffness term is in general significantly larger than the axial stiffness contribution, suggesting that from a tuning perspective it may be possible to use these stiffness contributions for coarse and fine frequency tuning, respectively. This 2D resonant frequency tuning approach extends earlier 1D approaches and may be particularly useful in applications where space constraints impact the available design space of the energy harvester.

  8. Classical harmonic vibrations with micro amplitudes and low frequencies monitored by quantum entanglement

    NASA Astrophysics Data System (ADS)

    Huang, Yong-Yi

    2016-02-01

    We study the entanglement dynamics of the two two-level atoms coupled with a single-mode polarized cavity field after incorporating the decoupled atomic centers of mass classical harmonic vibrations with micro amplitudes and low frequencies. We discover a new quantum mechanical measurement effect for the entanglement dynamics. We propose a quantitative vibrant factor to modify the concurrence of the two atomic states. When the vibrant frequencies are very low, we obtain that: (1) the factor depends on the relative vibrant displacements and the initial phases rather than the absolute amplitudes, and reduces the concurrence to three orders of magnitude; (2) the concurrence increases with the increase of the initial phases; (3) the frequency of the harmonic vibration can be obtained by measuring the maximal value of the concurrence during a small measurement time. These results indicate that the extremely weak classical harmonic vibrations can be monitored by the entanglement of quantum states. The effect reported in the paper always works well as long as the internal degrees of freedom of the system (regardless of unitary evolution or non-unitary evolution with time) are decoupled with the external classical harmonic vibrations of atomic centers of mass.

  9. Rotational structure of the five lowest frequency fundamental vibrational states of dimethylsulfoxide

    NASA Astrophysics Data System (ADS)

    Cuisset, Arnaud; Drumel, Marie-Aline Martin; Hindle, Francis; Mouret, Gaël; Sadovskií, Dmitrií A.

    2013-10-01

    We report on the successful extended analysis of the high-frequency (200-700 GHz) part of the gas phase (sub)mm-wave spectra of dimethylsulfoxide (DMSO). The spectrum was recorded at 100 kHz resolution using a solid state subTHz spectrometer. The five lowest energy fundamental vibrational states of DMSO with frequencies below 400 cm-1 were observed as sidebands along with the main 0←0 band. Neglecting the internal rotation of methyls, our rotational Hamiltonian reproduced the spectrum to the subMHz accuracy. We have found that the asymmetric bending state ν23 is the only low frequency fundamental vibrational state with the "anomalous" rotational structure uncovered in Cuisset et al. [1]. dmsomw 2013-09-04 15:03

  10. Low-frequency band gap mechanism of torsional vibration of lightweight elastic metamaterial shafts

    NASA Astrophysics Data System (ADS)

    Li, Lixia; Cai, Anjiang

    2016-07-01

    In this paper, the low-frequency band gap mechanism of torsional vibration is investigated for a kind of light elastic metamaterial (EM) shafts architecture comprised of a radial double-period element periodically as locally resonant oscillators with low frequency property. The dispersion relations are calculated by a method combining the transfer matrix and a lumped-mass method. The theoretical results agree well with finite method simulations, independent of the density of the hard material ring. The effects of the material parameters on the band gaps are further explored numerically. Our results show that in contrast to the traditional EM shaft, the weight of our proposed EM shaft can be reduced by 27% in the same band gap range while the vibration attenuation is kept unchanged, which is very convenient to instruct the potential engineering applications. Finally, the band edge frequencies of the lower band gaps for this light EM shaft are expressed analytically using physical heuristic models.

  11. Influence of low-frequency vibration on changes of biochemical parameters of living rats

    NASA Astrophysics Data System (ADS)

    Kasprzak, Cezary; Damijan, Zbigniew; Panuszka, Ryszard

    2004-05-01

    The aim of the research was to investigate how some selected biochemical parameters of living rats depend on exposure of low-frequency vibrations. Experiments were run on 30 Wistar rats randomly segregated into three groups: (I) 20 days old (before puberty), (II) 70th day after; (III) control group. The exposure was repeated seven times, for 3 h, at the same time of day. Vibrations applied during the first tests of the experiment had acceleration 1.22 m/s2 and frequency 20 Hz. At the 135th day the rats' bones were a subject of morphometric/biochemical examination. The results of biochemical tests proved decrease in LDL and HDL cholesterol levels for exposed rats as well as the Ca contents in blood plasma. There was evident increasing of Ca in blood plasma in exposed rats for frequency of exposition.

  12. Use of chaotic and random vibrations to generate high frequency test inputs

    SciTech Connect

    Gregory, D. L.; Paez, T. L.

    1990-01-01

    This paper and a companion paper show the traditional limits on amplitude and frequency that can be generated in a laboratory test on a vibration exciter can be substantially extended. This is accomplished by attaching a device to the shaker that permits controlled metal to metal impacts that generate high frequency, high acceleration environment on a test surface. A companion paper (Reference 1) shows that a sinusoidal or random shaker input can be used to generate a random vibration environment on the test surface. This paper derives the three response components that occur on the test surface due to an impact on the bottom surface and the base driven response from the shaker input. These response components are used to generate impulse response functions and frequency response functions which are used in the companion paper to derive power spectral density functions for the overall response. 9 refs., 8 figs.

  13. Dependence of palmar sweating response and central nervous system activity on the frequency of whole-body vibration.

    PubMed

    Ando, Hideo; Noguchi, Ryo

    2003-06-01

    This study was carried out to determine the effects of the frequency of whole-body vibration on palmar sweating response and the activity of the central sympathetic nervous system. Palmar sweating volume was measured on the right palm of six healthy men before and during 3 minutes of exposure to sinusoidal whole-body vibration at three different frequencies (16, 31.5, and 63 Hz). The whole-body vibration had a frequency-weighted, root mean square (rms) acceleration magnitude of 2.0 m/s2. As the index of the activated central sympathetic nervous system, saliva level of 3-methoxy-4-hydroxyphenylglycol (MHPG) was analyzed before and immediately after each vibration exposure. Each vibration frequency induced a palmar sweating response, that of 31.5 Hz being the largest. However, no significant difference was found between the three vibration conditions. Saliva MHPG increased in all the vibration exposures, and the largest change was observed at 31.5 Hz, the difference being significant. Acute exposure to whole-body vibration induced a palmar sweating response and activated the central sympathetic nervous system. The effects on the central nervous system were found to be dependent on the frequency of the vibration.

  14. Influence of pelvic position and vibration frequency on muscle activation during whole body vibration in quiet standing

    PubMed Central

    Kim, Joong-Hwi; Seo, Hye-Jung

    2015-01-01

    [Purpose] The purpose of this study was to investigate muscle activation related to postural stability depending on the pelvic position and frequency of whole body vibration (WBV) during quiet standing, and to identify the most effective training conditions that elicit the highest neuromuscular responses. [Subjects and Methods] Eighteen healthy subjects voluntarily participated in this single-group, repeated-measures study in which surface electromyography (EMG) data for the upper trapezius, rectus abdominis, external oblique abdominis, erector spinae, gluteus maximus, rectus femoris, semitendinosus, and medial gastrocnemius were collected at three frequencies (0 Hz, 10 Hz, and 20 Hz) of WBV and three pelvic positions (neutral, anterior tilt, posterior tilt) for each subject during quiet standing. [Results] The EMG activities of all the recorded muscles showed significant differences between the three frequencies of WBV and three pelvic positions during quiet standing. [Conclusion] The study findings suggest that a higher WBV frequency (20 Hz) should be used to strengthen most muscles, and that using the posterior pelvic tilt during WBV is much more effective at strengthening and training muscles related to core stability. PMID:25995555

  15. Frequency domain active vibration control of a flexible plate based on neural networks

    NASA Astrophysics Data System (ADS)

    Liu, Jinxin; Chen, Xuefeng; He, Zhengjia

    2013-06-01

    A neural-network (NN)-based active control system was proposed to reduce the low frequency noise radiation of the simply supported flexible plate. Feedback control system was built, in which neural network controller (NNC) and neural network identifier (NNI) were applied. Multi-frequency control in frequency domain was achieved by simulation through the NN-based control systems. A pre-testing experiment of the control system on a real simply supported plate was conducted. The NN-based control algorithm was shown to perform effectively. These works lay a solid foundation for the active vibration control of mechanical structures.

  16. Theory and experiment research for ultra-low frequency maglev vibration sensor

    SciTech Connect

    Zheng, Dezhi; Liu, Yixuan Guo, Zhanshe; Fan, Shangchun; Zhao, Xiaomeng

    2015-10-15

    A new maglev sensor is proposed to measure ultra-low frequency (ULF) vibration, which uses hybrid-magnet levitation structure with electromagnets and permanent magnets as the supporting component, rather than the conventional spring structure of magnetoelectric vibration sensor. Since the lower measurement limit needs to be reduced, the equivalent bearing stiffness coefficient and the equivalent damping coefficient are adjusted by the sensitivity unit structure of the sensor and the closed-loop control system, which realizes both the closed-loop control and the solving algorithms. A simple sensor experimental platform is then assembled based on a digital hardware system, and experimental results demonstrate that the lower measurement limit of the sensor is increased to 0.2 Hz under these experimental conditions, indicating promising results of the maglev sensor for ULF vibration measurements.

  17. Theory and experiment research for ultra-low frequency maglev vibration sensor.

    PubMed

    Zheng, Dezhi; Liu, Yixuan; Guo, Zhanshe; Zhao, Xiaomeng; Fan, Shangchun

    2015-10-01

    A new maglev sensor is proposed to measure ultra-low frequency (ULF) vibration, which uses hybrid-magnet levitation structure with electromagnets and permanent magnets as the supporting component, rather than the conventional spring structure of magnetoelectric vibration sensor. Since the lower measurement limit needs to be reduced, the equivalent bearing stiffness coefficient and the equivalent damping coefficient are adjusted by the sensitivity unit structure of the sensor and the closed-loop control system, which realizes both the closed-loop control and the solving algorithms. A simple sensor experimental platform is then assembled based on a digital hardware system, and experimental results demonstrate that the lower measurement limit of the sensor is increased to 0.2 Hz under these experimental conditions, indicating promising results of the maglev sensor for ULF vibration measurements.

  18. Theory and experiment research for ultra-low frequency maglev vibration sensor

    NASA Astrophysics Data System (ADS)

    Zheng, Dezhi; Liu, Yixuan; Guo, Zhanshe; Zhao, Xiaomeng; Fan, Shangchun

    2015-10-01

    A new maglev sensor is proposed to measure ultra-low frequency (ULF) vibration, which uses hybrid-magnet levitation structure with electromagnets and permanent magnets as the supporting component, rather than the conventional spring structure of magnetoelectric vibration sensor. Since the lower measurement limit needs to be reduced, the equivalent bearing stiffness coefficient and the equivalent damping coefficient are adjusted by the sensitivity unit structure of the sensor and the closed-loop control system, which realizes both the closed-loop control and the solving algorithms. A simple sensor experimental platform is then assembled based on a digital hardware system, and experimental results demonstrate that the lower measurement limit of the sensor is increased to 0.2 Hz under these experimental conditions, indicating promising results of the maglev sensor for ULF vibration measurements.

  19. Combined Amplitude and Frequency Measurements for Non-Contacting Turbomachinery Blade Vibration

    NASA Technical Reports Server (NTRS)

    Platt, Michael J. (Inventor); Jagodnik, John J. (Inventor)

    2013-01-01

    A method and apparatus for measuring the vibration of rotating blades, such as turbines, compressors, fans, or pumps, including sensing the return signal from projected energy and/or field changes from a plurality of sensors mounted on the machine housing. One or more of the sensors has a narrow field of measurement and the data is processed to provide the referenced time of arrival of each blade, and therefore the blade tip deflection due to vibration. One or more of the sensors has a wide field of measurement, providing a time history of the approaching and receding blades, and the data is processed to provide frequency content and relative magnitudes of the active mode(s) of blade vibration. By combining the overall tip deflection magnitude with the relative magnitudes of the active modes, the total vibratory stress state of the blade can be determined.

  20. Frontside-micromachined planar piezoresistive vibration sensor: Evaluating performance in the low frequency test range

    SciTech Connect

    Zhang, Lan; Lu, Jian Takagi, Hideki; Maeda, Ryutaro

    2014-01-15

    Using a surface piezoresistor diffusion method and front-side only micromachining process, a planar piezoresistive vibration sensor was successfully developed with a simple structure, lower processing cost and fewer packaging difficulties. The vibration sensor had a large sector proof mass attached to a narrow flexure. Optimization of the boron diffusion piezoresistor placed on the edge of the narrow flexure greatly improved the sensitivity. Planar vibration sensors were fabricated and measured in order to analyze the effects of the sensor dimensions on performance, including the values of flexure width and the included angle of the sector. Sensitivities of fabricated planar sensors of 0.09–0.46 mV/V/g were measured up to a test frequency of 60 Hz. The sensor functioned at low voltages (<3 V) and currents (<1 mA) with a high sensitivity and low drift. At low background noise levels, the sensor had performance comparable to a commercial device.

  1. Effect of low-magnitude, high-frequency vibration on osteocytes in the regulation of osteoclasts.

    PubMed

    Lau, Esther; Al-Dujaili, Saja; Guenther, Axel; Liu, Dawei; Wang, Liyun; You, Lidan

    2010-06-01

    Osteocytes are well evidenced to be the major mechanosensor in bone, responsible for sending signals to the effector cells (osteoblasts and osteoclasts) that carry out bone formation and resorption. Consistent with this hypothesis, it has been shown that osteocytes release various soluble factors (e.g. transforming growth factor-beta, nitric oxide, and prostaglandins) that influence osteoblastic and osteoclastic activities when subjected to a variety of mechanical stimuli, including fluid flow, hydrostatic pressure, and mechanical stretching. Recently, low-magnitude, high-frequency (LMHF) vibration (e.g., acceleration less than <1 x g, where g=9.81m/s(2), at 20-90 Hz) has gained much interest as studies have shown that such mechanical stimulation can positively influence skeletal homeostasis in animals and humans. Although the anabolic and anti-resorptive potential of LMHF vibration is becoming apparent, the signaling pathways that mediate bone adaptation to LMHF vibration are unknown. We hypothesize that osteocytes are the mechanosensor responsible for detecting the vibration stimulation and producing soluble factors that modulate the activity of effector cells. Hence, we applied low-magnitude (0.3 x g) vibrations to osteocyte-like MLO-Y4 cells at various frequencies (30, 60, 90 Hz) for 1h. We found that osteocytes were sensitive to this vibration stimulus at the transcriptional level: COX-2 maximally increased by 344% at 90Hz, while RANKL decreased most significantly (-55%, p<0.01) at 60Hz. Conditioned medium collected from the vibrated MLO-Y4 cells attenuated the formation of large osteoclasts (> or =10 nuclei) by 36% (p<0.05) and the amount of osteoclastic resorption by 20% (p=0.07). The amount of soluble RANKL (sRANKL) in the conditioned medium was found to be 53% lower in the vibrated group (p<0.01), while PGE(2) release was also significantly decreased (-61%, p<0.01). We conclude that osteocytes are able to sense LMHF vibration and respond by producing

  2. Effect of low-magnitude, high-frequency vibration on osteocytes in the regulation of osteoclasts

    PubMed Central

    Lau, Esther; Al-Dujaili, Saja; Guenther, Axel; Liu, Dawei; Wang, Liyun; You, Lidan

    2010-01-01

    Osteocytes are well evidenced to be the major mechanosensor in bone, responsible for sending signals to the effector cells (osteoblasts and osteoclasts) that carry out bone formation and resorption. Consistent with this hypothesis, it has been shown that osteocytes release various soluble factors (e.g. transforming growth factor-β, nitric oxide, and prostaglandins) that influence osteoblastic and osteoclastic activities when subjected to a variety of mechanical stimuli, including fluid flow, hydrostatic pressure, and mechanical stretching. Recently, low-magnitude, high-frequency (LMHF) vibration (e.g., acceleration less than <1g, where g=9.98 m/s2, at 20-90 Hz) has gained much interest as studies have shown that such mechanical stimulation can positively influence skeletal homeostasis in animals and humans. Although the anabolic and anti-resorptive potential of LMHF vibration is becoming apparent, the signaling pathways that mediate bone adaptation to LMHF vibration are unknown. We hypothesize that osteocytes are the mechanosensor responsible for detecting the vibration stimulation and producing soluble factors that modulate the activity of effector cells. Hence, we applied low-magnitude (0.3g) vibrations to osteocyte-like MLO-Y4 cells at various frequencies (30, 60, 90 Hz) for 1 hour. We found that osteocytes were sensitive to this vibration stimulus at the transcriptional level: COX-2 maximally increased by 344% at 90 Hz, while RANKL decreased most significantly (-55%, p<0.01) at 60 Hz. Conditioned medium collected from the vibrated MLO-Y4 cells attenuated the formation of large osteoclasts (≥10 nuclei) by 36% (p<0.05) and the amount of osteoclastic resorption by 20% (p=0.07). The amount of soluble RANKL (sRANKL) in the conditioned medium was found to be 53% lower in the vibrated group (p<0.01), while PGE2 release was also significantly decreased (-61%, p<0.01). We conclude that osteocytes are able to sense LMHF vibration and respond by producing soluble

  3. Electric-field effects on the OH vibrational frequency and infrared absorption intensity for water

    NASA Astrophysics Data System (ADS)

    Hermansson, Kersti

    1993-07-01

    The variations of the anharmonic OH frequency and the infrared absorption intensity with field strength have been calculated for the uncoupled OH stretching vibration of a water molecule in a static, homogeneous electric field using ab initio methods at the MP4 level with a nearly saturated basis set. The OH frequency is found to be virtually independent of the field components perpendicular to the vibrating OH bond. For the parallel component, the frequency vs field curve is close to quadratic, with a maximum for a slightly negative (directed from H to O) field strength. The external field perturbation, defined as Vext(E∥,rOH)=Vtot(E∥, rOH)-Vfree(rOH), is found to be closely linear in rOH, except when the field strength E∥ is both large and negative. The linear external force constant is almost perfectly accounted for by the sum of two terms, -E∥ṡdμ∥free/drOH and -1/2ṡE∥ṡ∂μ∥induced/∂rOH. These derivatives are quite insensitive to the choice of basis-set. The ∂μ∥induced/∂rOH derivative is approximately proportional to E∥, and gives rise to the arclike shape of the frequency vs field curve. The frequency maximum occurs where ∂μ∥tot/∂rOH≊0. It is the sign of dμ∥free/drOH which determines that the frequency maximum occurs at a negative field strength for water (but at a positive field strength for OH-, for example), i.e., that a frequency red-shift (blue-shift for OH-) occurs when the molecule is bound. The linear relationship between the infrared absorption intensity and frequency of the water OH vibration is derived.

  4. Statistics and Properties of Low-Frequency Vibrational Modes in Structural Glasses.

    PubMed

    Lerner, Edan; Düring, Gustavo; Bouchbinder, Eran

    2016-07-15

    Low-frequency vibrational modes play a central role in determining various basic properties of glasses, yet their statistical and mechanical properties are not fully understood. Using extensive numerical simulations of several model glasses in three dimensions, we show that in systems of linear size L sufficiently smaller than a crossover size L_{D}, the low-frequency tail of the density of states follows D(ω)∼ω^{4} up to the vicinity of the lowest Goldstone mode frequency. We find that the sample-to-sample statistics of the minimal vibrational frequency in systems of size Lfrequency modes are spatially quasilocalized and that their localization and associated quartic anharmonicity are largely frequency independent. The effect of preparation protocols on the low-frequency modes is elucidated, and a number of glassy length scales are briefly discussed.

  5. Temperature compensation method for the resonant frequency of a differential vibrating accelerometer using electrostatic stiffness control

    NASA Astrophysics Data System (ADS)

    Lee, Jungshin; Rhim, Jaewook

    2012-09-01

    Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment.

  6. Measurements of high frequency vibration using fiber Bragg grating sensors packaged on PZT plate

    NASA Astrophysics Data System (ADS)

    Fang, Qiaofeng; Chen, Wentao; Yin, Zhenyu; Liu, Yunqi

    2014-11-01

    We demonstrate the fiber Bragg grating (FBG) vibration sensors working at a frequency up to 900 kHz. The FBGs were surface-mounted on the piezoelectric (PZT) ceramic, which is used as the vibration sensor head. A nonlinear response was measured with a periodically strong response at the frequencies of 1 kHz, 5 kHz, 12 kHz, 40 kHz, 70 kHz and 400 kHz. Four kind of polymer were used to package the FBG on the PZT plate. The gratings have similar pattern of vibration response with different deviation on the output voltage. The FBGs packaged with the polymer 705B and EPO-TEK 353ND were found to have a better response at lower frequency, while the FBGs packaged with the polymer T120-023-C2 and TRA-BOND F112 have a better response at higher frequency. The sensors could be developed for the real-time monitoring of the large infrastructure.

  7. Wide operation frequency band magnetostrictive vibration power generator using nonlinear spring constant by permanent magnet

    NASA Astrophysics Data System (ADS)

    Furumachi, S.; Ueno, T.

    2016-04-01

    We study magnetostrictive vibration based power generator using iron-gallium alloy (Galfenol). The generator is advantages over conventional, such as piezoelectric material in the point of high efficiency highly robust and low electrical impedance. Generally, the generator exhibits maximum power when its resonant frequency matches the frequency of ambient vibration. In other words, the mismatch of these frequencies results in significant decrease of the output. One solution is making the spring characteristics nonlinear using magnetic force, which distorts the resonant peak toward higher or lower frequency side. In this paper, vibrational generator consisting of Galfenol plate of 6 by 0.5 by 13 mm wound with coil and U shape-frame accompanied with plates and pair of permanent magnets was investigated. The experimental results show that lean of resonant peak appears attributed on the non-linear spring characteristics, and half bandwidth with magnets is 1.2 times larger than that without. It was also demonstrated that the addition of proof mass is effective to increase the sensitivity but also the bandwidth. The generator with generating power of sub mW order is useful for power source of wireless heath monitoring for bridge and factory machine.

  8. Time frequency characterization of hand-transmitted, impulsive vibrations using analytic wavelet transform

    NASA Astrophysics Data System (ADS)

    Kim, Jay; Welcome, Daniel E.; Dong, Ren G.; Joon Song, Won; Hayden, Charles

    2007-11-01

    Current guidelines to assess health risk of hand-arm vibration are based on the frequency-weighted rms acceleration level, therefore do not fully consider the effect of temporal variations of the spectral energy. Time averaging effect involved with the frequency analysis may severely underestimate the risk of impact tools. A time-frequency ( T- F) analysis is necessary to characterize a highly transient signal whose spectral characteristics change rapidly in time. The analytic wavelet transform (AWT) is an ideal T- F analysis tool as it possesses the advantages of both the Fourier and wavelet transforms. The AWT is applied to acceleration signals measured from six tools, five impact type tools and one relatively steady-type tool, to explore possible improvements of the current risk assessment method of hand-arm vibration exposure. Based on the unique capability of the AWT, several new concepts including frequency-weighted time history, cumulative injury function, and cumulative injury index are defined in this study. Possible applications of these new concepts to hand-arm vibration research are described. Based on the results from this study, needs for future research are discussed.

  9. Nystagmus induced by high frequency vibrations of the skull in total unilateral peripheral vestibular lesions.

    PubMed

    Dumas, Georges; Perrin, Philippe; Schmerber, Sebastien

    2008-03-01

    The skull vibration-induced nystagmus test (SVINT) is a useful complementary test to the caloric test, which evaluates very low frequencies, and the head shaking test (HST), which explores medium range frequencies. These three tests are fully correlated in total unilateral vestibular lesions (tUVL) with a sensitivity of 98% and a specificity of 94% for the SVINT. The results of the interference of the SVINT with the cold caloric test on the intact ear suggest that different vestibular sensory cells are involved in these two tests. The stimulus location optimization suggests that vibrations directly stimulate the inner ear on the intact side. The aim of this study was to establish the effectiveness of a rapid, non-invasive test used to detect vestibular asymmetry at 30, 60 and 100 Hz stimulation in tUVL. The high frequency vibration test applied to the skull using the SVINT was compared to the results of HST and caloric test in 134 patients and 95 normal subjects: 131 patients had a total unilateral vestibular dysfunction and 3 had a bilateral total lesion (tBVL). The effects of stimulus frequency, topography and head position were studied using a video-nystagmograph. In tUVL, the SVINT always revealed a lesional nystagmus beating toward the healthy side at all frequencies. The mastoid site was more efficient than the cervical and vertex sites (p0.005). The mean skull vibratory nystagmus (SVN) slow phase velocity (SPV) is 10.7 degrees (SD =7.5; n=20). Mastoid stimulation efficiency was not correlated with the side of stimulation. SVN SPV was correlated with the total caloric efficiency on the healthy ear (p=0.03). The interference of the SVINT during the cold caloric test on the intact ear demonstrated a reversal of the caloric nystagmus at each application of the vibrator. In tBVL, SVINT revealed no nystagmus.

  10. Control of fluid flow during Bridgman crystal growth using low-frequency vibrational stirring

    NASA Astrophysics Data System (ADS)

    Zawilski, Kevin Thomas

    The goal of this research program was to develop an in depth understanding of a promising new method for stirring crystal growth melts called coupled vibrational stirring (CVS). CVS is a mixing technique that can be used in sealed systems and produces rapid mixing through vortex flows. Under normal operating conditions, CVS uses low-frequency vibrations to move the growth crucible along a circular path, producing a surface wave and convection in the melt. This research focused on the application of CVS to the vertical Bridgman technique. CVS generated flows were directly studied using a physical modeling system containing water/glycerin solutions. Sodium nitrate was chosen as a model growth system because the growth process could be directly observed using a transparent furnace. Lead magnesium niobate-lead titanate (PMNT) was chosen as the third system because of its potential application for high performance solid state transducers and actuators. In this study, the critical parameters for controlling CVS flows in cylindrical Bridgman systems were established. One of the most important results obtained was the dependence of an axial velocity gradient on the vibrational frequency. By changing the frequency, the intensity of fluid flow at a given depth can be easily manipulated. The intensity of CVS flows near the crystal-melt interface was found to be important. When flow intensity near the interface increased during growth, large growth rate fluctuations and significant changes in interface shape were observed. To eliminate such fluctuations, a constant flow rate near the crystal-melt interface was maintained by decreasing the vibrational frequency. A continuous frequency ramp was found to be essential to grow crystals of good quality under strong CVS flows. CVS generated flows were also useful in controlling the shape of the growth interface. In the sodium nitrate system without stirring, high growth rates produced a very concave interface. By adjusting the flow

  11. Vibrational Spectra and Adsorption of Trisiloxane Superspreading Surfactant at Air/Water Interface Studied with Sum Frequency Generation Vibrational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Feng, Jun; Wu, Dan; Wen, Jia; Liu, Shi-lin; Wang, Hong-fei

    2008-08-01

    The C-H stretch vibrational spectra of the trisiloxane superspreading surfactant Silwet L-77 ((CH3)3Si-O-Si(CH3)(C3H6)(OCH2CH2)7-8OCH3)-O-Si(CH3)3) at the air/water interface are measured with the surface Sum Frequency Generation Vibrational Spectroscopy (SFG-VS). The spectra are dominated with the features from the -Si-CH3 groups around 2905 cm-1 (symmetric stretch or SS mode) and 2957 cm-1 (mostly the asymmetric stretch or AS mode), and with the weak but apparent contribution from the -O-CH2- groups around 2880 cm-1 (symmetric stretch or SS mode). Comparison of the polarization dependent SFG spectra below and above the critical aggregate or micelle concentration (CAC) indicates that the molecular orientation of the C-H related molecular groups remained unchanged at different surface densities of the Silwet L-77 surfactant. The SFG-VS adsorption isotherm suggested that there was no sign of Silwet L-77 bilayer structure formation at the air/water interface. The Gibbs adsorption free energy of the Silwet surfactant to the air/water interface is -42.2±0.8kcal/mol, indicating the unusually strong adsorption ability of the Silwet L-77 superspreading surfactant.

  12. Time-frequency vibration analysis for the detection of motor damages caused by bearing currents

    NASA Astrophysics Data System (ADS)

    Prudhom, Aurelien; Antonino-Daviu, Jose; Razik, Hubert; Climente-Alarcon, Vicente

    2017-02-01

    Motor failure due to bearing currents is an issue that has drawn an increasing industrial interest over recent years. Bearing currents usually appear in motors operated by variable frequency drives (VFD); these drives may lead to common voltage modes which cause currents induced in the motor shaft that are discharged through the bearings. The presence of these currents may lead to the motor bearing failure only few months after system startup. Vibration monitoring is one of the most common ways for detecting bearing damages caused by circulating currents; the evaluation of the amplitudes of well-known characteristic components in the vibration Fourier spectrum that are associated with race, ball or cage defects enables to evaluate the bearing condition and, hence, to identify an eventual damage due to bearing currents. However, the inherent constraints of the Fourier transform may complicate the detection of the progressive bearing degradation; for instance, in some cases, other frequency components may mask or be confused with bearing defect-related while, in other cases, the analysis may not be suitable due to the eventual non-stationary nature of the captured vibration signals. Moreover, the fact that this analysis implies to lose the time-dimension limits the amount of information obtained from this technique. This work proposes the use of time-frequency (T-F) transforms to analyse vibration data in motors affected by bearing currents. The experimental results obtained in real machines show that the vibration analysis via T-F tools may provide significant advantages for the detection of bearing current damages; among other, these techniques enable to visualise the progressive degradation of the bearing while providing an effective discrimination versus other components that are not related with the fault. Moreover, their application is valid regardless of the operation regime of the machine. Both factors confirm the robustness and reliability of these tools

  13. A theoretical study of the sum frequency vibrational spectroscopy of the carbon tetrachloride/water interface

    NASA Astrophysics Data System (ADS)

    Green, Anthony J.; Perry, Angela; Moore, Preston B.; Space, Brian

    2012-03-01

    Theoretical approximations to the sum frequency vibrational spectroscopy (SFVS) of the carbon tetrachloride/water interface are constructed using the quantum-corrected time correlation functions (TCF) to aid in interpretation of experimental data and to predict novel vibrational modes. Instantaneous normal mode (INM) methods are used to characterize the observed modes leading to the TCF signal, thus providing molecular resolution of the vibrational lineshapes. Detailed comparisons of the theoretical signals are made with those obtained experimentally and show excellent agreement for the spectral peaks in the O-H stretching region of water. An intermolecular mode, unique to the interface, at 848 cm-1 is also identifiable, similar to the one seen for the water/vapor interface. INM analysis reveals the resonance is due to a wagging mode (hindered rotation) that was previously identified (Perry et al 2005 J. Chem. Phys. 123 144705) as localized on a single water molecule with both hydrogens displaced normal to the interface—generally it is found that the symmetry breaking at the interface leads to hindered translations and rotations at hydrophilic/hydrophobic interfaces that assume finite vibrational frequencies due to anchoring at the aqueous interface. Additionally, examination of the real and imaginary parts of the theoretical SFVS spectra reveal the spectroscopic species attributed the resonances and possible subspecies in the O-H region; these results are consistent with extant experimental data and associated analysis.

  14. Three-dimensional piezoelectric vibration energy harvester using spiral-shaped beam with triple operating frequencies

    SciTech Connect

    Zhao, Nian; Yang, Jin Yu, Qiangmo; Zhao, Jiangxin; Liu, Jun; Wen, Yumei; Li, Ping

    2016-01-15

    This work has demonstrated a novel piezoelectric energy harvester without a complex structure and appended component that is capable of scavenging vibration energy from arbitrary directions with multiple resonant frequencies. In this harvester, a spiral-shaped elastic thin beam instead of a traditional thin cantilever beam was adopted to absorb external vibration with arbitrary direction in three-dimensional (3D) spaces owing to its ability to bend flexibly and stretch along arbitrary direction. Furthermore, multiple modes in the elastic thin beam contribute to a possibility to widen the working bandwidth with multiple resonant frequencies. The experimental results show that the harvester was capable of scavenging the vibration energy in 3D arbitrary directions; they also exhibited triple power peaks at about 16 Hz, 21 Hz, and 28 Hz with the powers of 330 μW, 313 μW, and 6 μW, respectively. In addition, human walking and water wave energies were successfully converted into electricity, proving that our harvester was practical to scavenge the time-variant or multi-directional vibration energies in our daily life.

  15. Low frequency vibration induced streaming in a Hele-Shaw cell

    SciTech Connect

    Costalonga, M.; Brunet, P.; Peerhossaini, H.

    2015-01-15

    When an acoustic wave propagates in a fluid, it can generate a second order flow whose characteristic time is much longer than the period of the wave. Within a range of frequency between ten and several hundred Hz, a relatively simple and versatile way to generate streaming flow is to put a vibrating object in the fluid. The flow develops vortices in the viscous boundary layer located in the vicinity of the source of vibrations, leading in turn to an outer irrotational streaming called Rayleigh streaming. Because the flow originates from non-linear time-irreversible terms of the Navier-Stokes equation, this phenomenon can be used to generate efficient mixing at low Reynolds number, for instance in confined geometries. Here, we report on an experimental study of such streaming flow induced by a vibrating beam in a Hele-Shaw cell of 2 mm span using long exposure flow visualization and particle-image velocimetry measurements. Our study focuses especially on the effects of forcing frequency and amplitude on flow dynamics. It is shown that some features of this flow can be predicted by simple scaling arguments and that this vibration-induced streaming facilitates the generation of vortices.

  16. Gel performance in rheology and profile control under low-frequency vibration: coupling application of physical and chemical EOR techniques.

    PubMed

    Zheng, Li Ming; Pu, Chun Sheng; Liu, Jing; Ma, Bo; Khan, Nasir

    2017-01-01

    Flowing gel plugging and low-frequency vibration oil extraction technology have been widely applied in low-permeability formation. High probability of overlapping in action spheres of two technologies might lead to poor operating efficiency during gel injection. Study on flowing gel rheological properties under low-frequency vibration was essential, which was carried out indoor with viscosity measurement. Potential dynamic mechanisms were analyzed for the rheological variation. Under low-frequency vibration, gel rheological properties were found to be obviously influenced, with vibration delaying gel cross-linking in induction period, causing a two-stage gel viscosity change in acceleration period, and decreasing gel strength in stable period. Surface of gel system under vibration presented different fluctuating phenomenon from initial harmonic vibrating to heterogeneous fluctuating (droplet separation might appear) to final harmonic vibrating again. Dynamic displacement in unconsolidated sand pack revealed that low-frequency vibration during gel injection might be a measure to achieve deep profile control, with the gel injection depth increased by 65.8 % compared with the vibration-free sample. At last, suggestions for field test were given in the paper to achieve lower injection friction and better gel plugging efficiency.

  17. Low-frequency vibration isolation in sandwich plates by piezoelectric shunting arrays

    NASA Astrophysics Data System (ADS)

    Chen, Shengbing; Wang, Gang; Song, Yubao

    2016-12-01

    Piezoelectric shunting arrays are proposed to isolate low-frequency vibrations transmitted in sandwich plates. The performance is characterized through application of finite element method. The numerical result shows that a complete band gap, whose width is about 20 Hz, is produced in the desired low-frequency ranges. The band gap is induced by local resonances of the shunting circuits, whose location is strongly related to the inductance, while the resistance can broaden the band gap to some extent. Vibration experiments are conducted on a 1200 × 1000 × 15 mm aluminum honeycomb plate with two arrays of 5 × 5 shunted piezoelectric patches bonded on the surface panels. Significant attenuation is found in the experimental results, which agree well with the theoretical predictions. Consequently, the proposed idea is feasible and effective.

  18. Derivatives of buckling loads and vibration frequencies with respect to stiffness and initial strain parameters

    NASA Technical Reports Server (NTRS)

    Haftka, Raphael T.; Cohen, Gerald A.; Mroz, Zenon

    1990-01-01

    A uniform variational approach to sensitivity analysis of vibration frequencies and bifurcation loads of nonlinear structures is developed. Two methods of calculating the sensitivities of bifurcation buckling loads and vibration frequencies of nonlinear structures, with respect to stiffness and initial strain parameters, are presented. A direct method requires calculation of derivatives of the prebuckling state with respect to these parameters. An adjoint method bypasses the need for these derivatives by using instead the strain field associated with the second-order postbuckling state. An operator notation is used and the derivation is based on the principle of virtual work. The derivative computations are easily implemented in structural analysis programs. This is demonstrated by examples using a general purpose, finite element program and a shell-of-revolution program.

  19. Novel Euler-LaCoste linkage as a very low frequency vertical vibration isolator

    NASA Astrophysics Data System (ADS)

    Hosain, M. A.; Sirr, A.; Ju, L.; Blair, D. G.

    2012-08-01

    LaCoste linkage vibration isolators have shown excellent performance for ultra-low frequency vertical vibration isolation. However, such isolators depend on the use of conventional pre-stressed coil springs, which suffer from creep. Here, we show that compressional Euler springs can be configured to create a stable tension unit for use in a LaCoste structure. In a proof of concept experiment, we demonstrate a vertical resonance frequency of 0.15 Hz in an Euler-LaCoste configuration with 200 mm height. The system enables the use of very low creep maraging steel as spring elements to eliminate the creep while minimising spring mass and reducing the effect of parasitic resonances. Larger scale systems with optimized Euler spring boundary conditions should achieve performance suitable for applications on third generation gravitational wave detectors such as the proposed Einstein telescope.

  20. Anharmonic Vibrational Frequency Calculations Are Not Worthwhile for Small Basis Sets.

    PubMed

    Jacobsen, Ruth L; Johnson, Russell D; Irikura, Karl K; Kacker, Raghu N

    2013-02-12

    Anharmonic calculations using vibrational perturbation theory are known to provide near-spectroscopic accuracy when combined with high-level ab initio potential energy functions. However, performance with economical, popular electronic structure methods is less well characterized. We compare the accuracy of harmonic and anharmonic predictions from Hartree-Fock, second-order perturbation, and density functional theories combined with 6-31G(d) and 6-31+G(d,p) basis sets. As expected, anharmonic frequencies are closer than harmonic frequencies to experimental fundamentals. However, common practice is to correct harmonic predictions using multiplicative scaling. The surprising conclusion is that scaled anharmonic calculations are no more accurate than scaled harmonic calculations for the basis sets we used. The data used are from the Computational Chemistry Comparison and Benchmark Database (CCCBDB), maintained by the National Institute of Standards and Technology, which includes more than 3939 independent vibrations for 358 molecules.

  1. An Accurate Quartic Force Field and Vibrational Frequencies for HNO and DNO

    NASA Technical Reports Server (NTRS)

    Dateo, Christopher E.; Lee, Timothy J.; Schwenke, David W.

    1994-01-01

    An accurate ab initio quartic force field for HNO has been determined using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, CCSD(T), in conjunction with the correlation consistent polarized valence triple zeta (cc-pVTZ) basis set. Improved harmonic frequencies were determined with the cc-pVQZ basis set. Fundamental vibrational frequencies were determined using a second-order perturbation theory analysis and also using variational calculations. The N-0 stretch and bending fundamentals are determined well from both vibrational analyses. The H-N stretch, however, is shown to have an unusually large anharmonic correction, and is not well determined using second-order perturbation theory. The H-N fundamental is well determined from the variational calculations, demonstrating the quality of the ab initio quartic force field. The zero-point energy of HNO that should be used in isodesmic reactions is also discussed.

  2. On the linear elastic, isotropic modeling of poroelastic distributed vibration absorbers at low frequencies

    NASA Astrophysics Data System (ADS)

    Harne, R. L.

    2013-07-01

    Several past works have considered a passive vibration absorber device utilizing distributed mass and spring layers. The thickness of the poroelastic foam spring and the area density of the mass layer are modified to achieve a target natural frequency of the device while the foam itself provides adequate dissipation of energy as the mass dynamically compresses it at resonance. A model of the device earlier developed is briefly reviewed and validated by new experiments. The dependence of the absorber natural frequency and damping on the poroelastic spring thickness is observed in detail and is found to be consistent with past work on poroelastic material elastic characteristics outside of the linear dynamic regime. The results set a practical limit on the applicability of linearity assumptions in the present modeling of the distributed poroelastic vibration absorbers and thus determine a design parameter range for which the computationally efficient model is accurate.

  3. Novel Euler-LaCoste linkage as a very low frequency vertical vibration isolator.

    PubMed

    Hosain, M A; Sirr, A; Ju, L; Blair, D G

    2012-08-01

    LaCoste linkage vibration isolators have shown excellent performance for ultra-low frequency vertical vibration isolation. However, such isolators depend on the use of conventional pre-stressed coil springs, which suffer from creep. Here, we show that compressional Euler springs can be configured to create a stable tension unit for use in a LaCoste structure. In a proof of concept experiment, we demonstrate a vertical resonance frequency of 0.15 Hz in an Euler-LaCoste configuration with 200 mm height. The system enables the use of very low creep maraging steel as spring elements to eliminate the creep while minimising spring mass and reducing the effect of parasitic resonances. Larger scale systems with optimized Euler spring boundary conditions should achieve performance suitable for applications on third generation gravitational wave detectors such as the proposed Einstein telescope.

  4. Frequency Response of the Sample Vibration Mode in Scanning Probe Acoustic Microscope

    NASA Astrophysics Data System (ADS)

    Zhao, Ya-Jun; Cheng, Qian; Qian, Meng-Lu

    2010-05-01

    Based on the interaction mechanism between tip and sample in the contact mode of a scanning probe acoustic microscope (SPAM), an active mass of the sample is introduced in the mass-spring model. The tip motion and frequency response of the sample vibration mode in the SPAM are calculated by the Lagrange equation with dissipation function. For the silicon tip and glass assemblage in the SPAM the frequency response is simulated and it is in agreement with the experimental result. The living myoblast cells on the glass slide are imaged at resonance frequencies of the SPAM system, which are 20kHz, 30kHz and 120kHz. It is shown that good contrast of SPAM images could be obtained when the system is operated at the resonance frequencies of the system in high and low-frequency regions.

  5. Development and Validation of Transferable Amide I Vibrational Frequency Maps for Peptides

    PubMed Central

    Wang, L.; Middleton, C. T.; Zanni, M. T.; Skinner, J. L.

    2012-01-01

    Infrared (IR) spectroscopy of the amide I band has been widely utilized for the analysis of peptides and proteins. Theoretical modeling of IR spectra of proteins requires an accurate and efficient description of the amide I frequencies. In this paper, amide I frequency maps for protein backbone and side chain groups are developed from experimental spectra and vibrational lifetimes of N-methylacetamide and acetamide in different solvents. The frequency maps, along with established nearest-neighbor frequency shift and coupling schemes, are then applied to a variety of peptides in aqueous solution and reproduce experimental spectra well. The frequency maps are designed to be transferable to different environments; therefore, they can be used for heterogeneous systems, such as membrane proteins. PMID:21405034

  6. Low-frequency vibration study of amino acids using terahertz spectroscopy and solid-state density functional theory

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Tominaga, Keisuke; Hayashi, Michitoshi; Wang, Houng-Wei

    2014-11-01

    Understanding the low-frequency normal modes of amino acids, the building blocks of proteins, is crucial to reveal the vibration-function relationship in the macromolecular system. Recent advances in terahertz spectroscopy (THz) and solid-state density functional theory (DFT) have ensured an accurate description of low-frequency modes of amino acids. New knowledge people have learnt so far is that the inter- and intra-molecular vibrations are strongly mixed with each other in the THz region through the vibrational coordinate mixing. Rich information is believed embedded in this phenomenon. We introduce a generalized mode-analysis method that allows for the accurate decomposition of a normal mode of interest into the three intermolecular translations, three principal librations and various intrinsic intramolecular vibrations. This mode-analysis method will be demonstrated in the crystalline C60 systems and then applied to shed light on the nature of low-frequency phonons of glycine, diglycine and triglycine. This method helps reveal new intramolecular vibrational modes on the first hand, and more importantly, illuminate a new phenomenon of the frequency distribution of intramolecular vibrations (FDIV). FDIV describes the possible broad distributions of important intramolecular vibrations in the low-frequency normal modes. The FDIV concept may indicate an additional mechanism for the intramolecular vibrations to become thermally active and participate in various biological functions.

  7. Sparse Representation Based Frequency Detection and Uncertainty Reduction in Blade Tip Timing Measurement for Multi-Mode Blade Vibration Monitoring

    PubMed Central

    Pan, Minghao; Yang, Yongmin; Guan, Fengjiao; Hu, Haifeng; Xu, Hailong

    2017-01-01

    The accurate monitoring of blade vibration under operating conditions is essential in turbo-machinery testing. Blade tip timing (BTT) is a promising non-contact technique for the measurement of blade vibrations. However, the BTT sampling data are inherently under-sampled and contaminated with several measurement uncertainties. How to recover frequency spectra of blade vibrations though processing these under-sampled biased signals is a bottleneck problem. A novel method of BTT signal processing for alleviating measurement uncertainties in recovery of multi-mode blade vibration frequency spectrum is proposed in this paper. The method can be divided into four phases. First, a single measurement vector model is built by exploiting that the blade vibration signals are sparse in frequency spectra. Secondly, the uniqueness of the nonnegative sparse solution is studied to achieve the vibration frequency spectrum. Thirdly, typical sources of BTT measurement uncertainties are quantitatively analyzed. Finally, an improved vibration frequency spectra recovery method is proposed to get a guaranteed level of sparse solution when measurement results are biased. Simulations and experiments are performed to prove the feasibility of the proposed method. The most outstanding advantage is that this method can prevent the recovered multi-mode vibration spectra from being affected by BTT measurement uncertainties without increasing the probe number. PMID:28758952

  8. Changes in postural sway frequency and complexity in altered sensory environments following whole body vibrations.

    PubMed

    Dickin, D Clark; McClain, Matthew A; Hubble, Ryan P; Doan, Jon B; Sessford, David

    2012-10-01

    Studies assessing whole body vibration (WBV) have produced largely positive effects, with some neutral, on postural control with frequencies between 25 and 40 Hz. However no conclusive evidence indicates that 25-40 Hz elicits the optimal beneficial effects. To address this issue, a larger range of vibration intensity (10-50 Hz at peak-to-peak amplitudes of 2 and 5mm) was employed while increasing the postural complexity (altered somatosensory and/or visual information) to assess acute effects of 4-min of WBV on postural control. Twelve healthy young adults underwent postural assessment at four time intervals (prior to, immediately following and 10 and 20 min post WBV). Findings revealed both postural sway frequency and sway complexity/regularity were affected by WBV. Baseline posture demonstrated increased sway frequency (p=.04) following WBV with no changes in sway complexity. When the support surface was altered, changes in both the frequency and complexity of sway were elicited (p=.027, .002, respectively). When both somatosensory and visual information were altered delayed improvements in postural control were elicited (p=.05 and .01, for frequency and complexity, respectively). Given the differential acute effects as a function of postural task complexity, future longitudinal studies could determine the overall training effect on sway frequency and complexity.

  9. Computational Thermochemistry: Scale Factor Databases and Scale Factors for Vibrational Frequencies Obtained from Electronic Model Chemistries.

    PubMed

    Alecu, I M; Zheng, Jingjing; Zhao, Yan; Truhlar, Donald G

    2010-09-14

    Optimized scale factors for calculating vibrational harmonic and fundamental frequencies and zero-point energies have been determined for 145 electronic model chemistries, including 119 based on approximate functionals depending on occupied orbitals, 19 based on single-level wave function theory, three based on the neglect-of-diatomic-differential-overlap, two based on doubly hybrid density functional theory, and two based on multicoefficient correlation methods. Forty of the scale factors are obtained from large databases, which are also used to derive two universal scale factor ratios that can be used to interconvert between scale factors optimized for various properties, enabling the derivation of three key scale factors at the effort of optimizing only one of them. A reduced scale factor optimization model is formulated in order to further reduce the cost of optimizing scale factors, and the reduced model is illustrated by using it to obtain 105 additional scale factors. Using root-mean-square errors from the values in the large databases, we find that scaling reduces errors in zero-point energies by a factor of 2.3 and errors in fundamental vibrational frequencies by a factor of 3.0, but it reduces errors in harmonic vibrational frequencies by only a factor of 1.3. It is shown that, upon scaling, the balanced multicoefficient correlation method based on coupled cluster theory with single and double excitations (BMC-CCSD) can lead to very accurate predictions of vibrational frequencies. With a polarized, minimally augmented basis set, the density functionals with zero-point energy scale factors closest to unity are MPWLYP1M (1.009), τHCTHhyb (0.989), BB95 (1.012), BLYP (1.013), BP86 (1.014), B3LYP (0.986), MPW3LYP (0.986), and VSXC (0.986).

  10. Effect of transient heating on vibration frequencies of some simple wing structures

    NASA Technical Reports Server (NTRS)

    Vosteen, Louis F; Mcwithey, Robert R; Thomson, Robert G

    1957-01-01

    Thermal stresses, which may result from transient heating, can cause changes in the effective stiffness of wing structures. Some effects of this change in stiffness were investigated experimentally by radiantly heating three types of simple wing structures: a uniform plate, a solid double-wedge section, and a circular-arc multiweb-wing section. Changes in stiffness were determined by measuring the changes in natural frequency of vibration during transient heating. Some comparisons are made between theoretical calculations and the measured data.

  11. Remote-Controlled Rotorcraft Blade Vibration and Modal Analysis at Low Frequencies

    DTIC Science & Technology

    2016-02-01

    3 Fig. 4 Blade response to shaker outputting 1-V sine wave at 5 Hz..................4 Fig. 5...Rotor blade response to shaker outputting 1-V sine wave at 100 Hz ....5 Fig. 6 Rotor blade response to shaker outputting 1-V sine sweep from 20- to 100...that the unflawed rotor blade was tested. Frequency, amplitude, and mode data of vibration were collected while the shaker was outputting a sine

  12. Vibrational characteristics of FRP-bonded concrete interfacial defects in a low frequency regime

    NASA Astrophysics Data System (ADS)

    Cheng, Tin Kei; Lau, Denvid

    2014-04-01

    As externally bonded fiber-reinforced polymer (FRP) is a critical load-bearing component of strengthened or retrofitted civil infrastructures, the betterment of structural health monitoring (SHM) methodology for such composites is imperative. Henceforth the vibrational characteristics of near surface interfacial defects involving delamination and trapped air pockets at the FRP-concrete interface are investigated in this study using a finite element approach. Intuitively, due to its lower interfacial stiffness compared with an intact interface, a damaged region is expected to have a set of resonance frequencies different from an intact region when excited by acoustic waves. It has been observed that, when excited acoustically, both the vibrational amplitudes and frequency peaks in the response spectrum of the defects demonstrate a significant deviation from an intact FRP-bonded region. For a thin sheet of FRP bonded to concrete with sizable interfacial defects, the fundamental mode under free vibration is shown to be relatively low, in the order of kHz. Due to the low resonance frequencies of the defects, the use of low-cost equipment for interfacial defect detection via response spectrum analysis is highly feasible.

  13. Low-frequency vibration treatment of bone marrow stromal cells induces bone repair in vivo

    PubMed Central

    He, Shengwei; Zhao, Wenzhi; Zhang, Lu; Mi, Lidong; Du, Guangyu; Sun, Chuanxiu; Sun, Xuegang

    2017-01-01

    Objective(s): To study the effect of low-frequency vibration on bone marrow stromal cell differentiation and potential bone repair in vivo. Materials and Methods: Forty New Zealand rabbits were randomly divided into five groups with eight rabbits in each group. For each group, bone defects were generated in the left humerus of four rabbits, and in the right humerus of the other four rabbits. To test differentiation, bones were isolated and demineralized, supplemented with bone marrow stromal cells, and implanted into humerus bone defects. Varying frequencies of vibration (0, 12.5, 25, 50, and 100 Hz) were applied to each group for 30 min each day for four weeks. When the bone defects integrated, they were then removed for histological examination. mRNA transcript levels of runt-related transcription factor 2, osteoprotegerin, receptor activator of nuclear factor κ-B ligan, and pre-collagen type 1 α were measured. Results: Humeri implanted with bone marrow stromal cells displayed elevated callus levels and wider, more prevalent, and denser trabeculae following treatment at 25 and 50 Hz. The mRNA levels of runt-related transcription factor 2, osteoprotegerin, receptor activator of nuclear factor κ-B ligand, and pre-collagen type 1 α were also markedly higher following 25 and 50 Hz treatment. Conclusion: Low frequency (25–50 Hz) vibration in vivo can promote bone marrow stromal cell differentiation and repair bone injury. PMID:28133520

  14. Low-frequency vibration treatment of bone marrow stromal cells induces bone repair in vivo.

    PubMed

    He, Shengwei; Zhao, Wenzhi; Zhang, Lu; Mi, Lidong; Du, Guangyu; Sun, Chuanxiu; Sun, Xuegang

    2017-01-01

    To study the effect of low-frequency vibration on bone marrow stromal cell differentiation and potential bone repair in vivo. Forty New Zealand rabbits were randomly divided into five groups with eight rabbits in each group. For each group, bone defects were generated in the left humerus of four rabbits, and in the right humerus of the other four rabbits. To test differentiation, bones were isolated and demineralized, supplemented with bone marrow stromal cells, and implanted into humerus bone defects. Varying frequencies of vibration (0, 12.5, 25, 50, and 100 Hz) were applied to each group for 30 min each day for four weeks. When the bone defects integrated, they were then removed for histological examination. mRNA transcript levels of runt-related transcription factor 2, osteoprotegerin, receptor activator of nuclear factor κ-B ligan, and pre-collagen type 1 α were measured. Humeri implanted with bone marrow stromal cells displayed elevated callus levels and wider, more prevalent, and denser trabeculae following treatment at 25 and 50 Hz. The mRNA levels of runt-related transcription factor 2, osteoprotegerin, receptor activator of nuclear factor κ-B ligand, and pre-collagen type 1 α were also markedly higher following 25 and 50 Hz treatment. Low frequency (25-50 Hz) vibration in vivo can promote bone marrow stromal cell differentiation and repair bone injury.

  15. Modal analysis of 2-D sedimentary basin from frequency domain decomposition of ambient vibration array recordings

    NASA Astrophysics Data System (ADS)

    Poggi, Valerio; Ermert, Laura; Burjanek, Jan; Michel, Clotaire; Fäh, Donat

    2015-01-01

    Frequency domain decomposition (FDD) is a well-established spectral technique used in civil engineering to analyse and monitor the modal response of buildings and structures. The method is based on singular value decomposition of the cross-power spectral density matrix from simultaneous array recordings of ambient vibrations. This method is advantageous to retrieve not only the resonance frequencies of the investigated structure, but also the corresponding modal shapes without the need for an absolute reference. This is an important piece of information, which can be used to validate the consistency of numerical models and analytical solutions. We apply this approach using advanced signal processing to evaluate the resonance characteristics of 2-D Alpine sedimentary valleys. In this study, we present the results obtained at Martigny, in the Rhône valley (Switzerland). For the analysis, we use 2 hr of ambient vibration recordings from a linear seismic array deployed perpendicularly to the valley axis. Only the horizontal-axial direction (SH) of the ground motion is considered. Using the FDD method, six separate resonant frequencies are retrieved together with their corresponding modal shapes. We compare the mode shapes with results from classical standard spectral ratios and numerical simulations of ambient vibration recordings.

  16. Analysis of vibration and frequency transmission of high speed EMU with flexible model

    NASA Astrophysics Data System (ADS)

    Ren, Zun-Song; Yang, Guang; Wang, Shan-Shan; Sun, Shou-Guang

    2014-12-01

    When the operation speed of the high-speed train increases and the weight of the carbody becomes lighter, not only does the sensitivity of the wheel/rail contact get higher, but also the vibration frequency range of the vehicle system gets enlarged and more frequencies are transmitted from the wheelset to the carbody. It is important to investigate the vibration characteristics and the dynamic frequency transmission from the wheel/rail interface to the carbody of the high-speed electric multi-uint (EMU). An elastic highspeed vehicle dynamics model is established in which the carbody, bogieframes, and wheelsets are all dealt with as flexible body. A rigid high-speed vehicle dynamics model is set up to compare with the simulation results of the elastic model. In the rigid vehicle model, the carbody, bogieframes and wheelsets are treated as rigid component while the suspension and structure parameters are the same as used in the elastic model. The dynamic characteristic of the elastic high speed vehicle is investigated in time and frequency domains and the difference of the acceleration, frequency distribution and transmission of the two types of models are presented. The results show that the spectrumpower density of the vehicle decreases from the wheelset to the carbody and the acceleration transmission ratio is approximately from 1% to 10% for each suspension system. The frequency of the wheelset rotation is evident in the vibration of the flexible model and is transmitted from the wheelset to the bogieframe and to the carbody. The results of the flexible model are more reasonable than that of the rigid model. A field test data of the high speed train are presented to verify the simulation results. It shows that the simulation results are coincidentwith the field test data.

  17. Quartic force field predictions of the fundamental vibrational frequencies and spectroscopic constants of the cations HOCO+ and DOCO+

    NASA Astrophysics Data System (ADS)

    Fortenberry, Ryan C.; Huang, Xinchuan; Francisco, Joseph S.; Crawford, T. Daniel; Lee, Timothy J.

    2012-06-01

    Only one fundamental vibrational frequency of protonated carbon dioxide (HOCO+) has been experimentally observed in the gas phase: the ν1 O-H stretch. Utilizing quartic force fields defined from CCSD(T)/aug-cc-pVXZ (X = T,Q,5) complete basis set limit extrapolated energies modified to include corrections for core correlation and scalar relativistic effects coupled to vibrational perturbation theory and vibrational configuration interaction computations, we are predicting the full set of gas phase fundamental vibrational frequencies of HOCO+. Our prediction of ν1 is within less than 1 cm-1 of the experimental value. Our computations also include predictions of the gas phase fundamental vibrational frequencies of the deuterated form of the cation, DOCO+. Additionally, other spectroscopic constants for both systems are reported as part of this study, and a search for a cis-HOCO+ minimum found no such stationary point on the potential surface indicating that only the trans isomer is stable.

  18. Nonlinear Microstructured Material to Reduce Noise and Vibrations at Low Frequencies

    NASA Astrophysics Data System (ADS)

    Lavazec, Deborah; Cumunel, Gwendal; Duhamel, Denis; Soize, Christian; Batou, Anas

    2016-09-01

    At low frequencies, for which the wavelengths are wide, the acoustic waves and the mechanical vibrations cannot easily be reduced in the structures at macroscale by using dissipative materials, contrarily to the middle- and high-frequency ranges. The final objective of this work is to reduce the vibrations and the induced noise on a broad low-frequency band by using a microstructured material by inclusions that are randomly arranged in the material matrix. The dynamical regimes of the inclusions will be imposed in the nonlinear domain in order that the energy be effectively pumped over a broad frequency band around the resonance frequency, due to the nonlinearity. The first step of this work is to design and to analyze the efficiency of an inclusion, which is made up of a hollow frame including a point mass centered on a beam. This inclusion is designed in order to exhibit nonlinear geometric effects in the low-frequency band that is observed. For this first step, the objective is to develop the simplest mechanical model that has the capability to roughly predict the experimental results that are measured. The second step, which is not presented in the paper, will consist in developing a more sophisticated nonlinear dynamical model of the inclusion. In this paper, devoted to the first step, it is proved that the nonlinearity induces an attenuation on a broad frequency band around the resonance, contrarily to its linear behavior for which the attenuation is only active in a narrow frequency band around the resonance. We will present the design in terms of geometry, dimension and materials for the inclusion, the experimental manufacturing of this system realized with a 3D printing system, and the experimental measures that have been performed. We compare the prevision given by the stochastic computational model with the measurements. The results obtained exhibit the physical attenuation over a broad low-frequency band, which were expected.

  19. Effects of vibration frequency on vibration-assisted nano-scratch process of mono-crystalline copper via molecular dynamics simulation

    SciTech Connect

    Zhu, Bo; Zhao, Hongwei E-mail: khl69@163.com; Zhao, Dan; Zhang, Peng; Yang, Yihan; Han, Lei; Kui, Hailin E-mail: khl69@163.com

    2016-03-15

    It has always been a critical issue to understand the material removal behavior of Vibration-Assisted Machining (VAM), especially on atomic level. To find out the effects of vibration frequency on material removal response, a three-dimensional molecular dynamics (MD) model has been established in this research to investigate the effects of scratched groove, crystal defects on the surface quality, comparing with the Von Mises shear strain and tangential force in simulations during nano-scratching process. Comparisons are made among the results of simulations from different vibration frequency with the same scratching feed, depth, amplitude and crystal orientation. Copper potential in this simulation is Embedded-Atom Method (EAM) potential. Interaction between copper and carbon atoms is Morse potential. Simulational results show that higher frequency can make groove smoother. Simulation with high frequency creates more dislocations to improve the machinability of copper specimen. The changing frequency does not have evident effects on Von Mises shear strain. Higher frequency can decrease the tangential force to reduce the consumption of cutting energy and tool wear. In conclusion, higher vibration frequency in VAM on mono-crystalline copper has positive effects on surface finish, machinablility and tool wear reduction.

  20. Effects of vibration frequency on vibration-assisted nano-scratch process of mono-crystalline copper via molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Zhu, Bo; Zhao, Hongwei; Zhao, Dan; Zhang, Peng; Yang, Yihan; Han, Lei; Kui, Hailin

    2016-03-01

    It has always been a critical issue to understand the material removal behavior of Vibration-Assisted Machining (VAM), especially on atomic level. To find out the effects of vibration frequency on material removal response, a three-dimensional molecular dynamics (MD) model has been established in this research to investigate the effects of scratched groove, crystal defects on the surface quality, comparing with the Von Mises shear strain and tangential force in simulations during nano-scratching process. Comparisons are made among the results of simulations from different vibration frequency with the same scratching feed, depth, amplitude and crystal orientation. Copper potential in this simulation is Embedded-Atom Method (EAM) potential. Interaction between copper and carbon atoms is Morse potential. Simulational results show that higher frequency can make groove smoother. Simulation with high frequency creates more dislocations to improve the machinability of copper specimen. The changing frequency does not have evident effects on Von Mises shear strain. Higher frequency can decrease the tangential force to reduce the consumption of cutting energy and tool wear. In conclusion, higher vibration frequency in VAM on mono-crystalline copper has positive effects on surface finish, machinablility and tool wear reduction.

  1. Whole Body Vibration at Different Exposure Frequencies: Infrared Thermography and Physiological Effects

    PubMed Central

    Sonza, Anelise; Robinson, Caroline C.; Achaval, Matilde; Zaro, Milton A.

    2015-01-01

    The aim of this study was to investigate the effects of whole body vibration (WBV) on physiological parameters, cutaneous temperature, tactile sensitivity, and balance. Twenty-four healthy adults (25.3 ± 2.6 years) participated in four WBV sessions. They spent 15 minutes on a vibration platform in the vertical mode at four different frequencies (31, 35, 40, and 44 Hz) with 1 mm of amplitude. All variables were measured before and after WBV exposure. Pressure sensation in five anatomical regions and both feet was determined using Von Frey monofilaments. Postural sway was measured using a force plate. Cutaneous temperature was obtained with an infrared camera. WBV influences the discharge of the skin touch-pressure receptors, decreasing sensitivity at all measured frequencies and foot regions (P ≤ 0.05). Regarding balance, no differences were found after 20 minutes of WBV at frequencies of 31 and 35 Hz. At 40 and 44 Hz, participants showed higher anterior-posterior center of pressure (COP) velocity and length. The cutaneous temperature of the lower limbs decreased during and 10 minutes after WBV. WBV decreases touch-pressure sensitivity at all measured frequencies 10 min after exposure. This may be related to the impaired balance at higher frequencies since these variables have a role in maintaining postural stability. Vasoconstriction might explain the decreased lower limb temperature. PMID:25664338

  2. Vibration sensor data denoising using a time-frequency manifold for machinery fault diagnosis.

    PubMed

    He, Qingbo; Wang, Xiangxiang; Zhou, Qiang

    2013-12-27

    Vibration sensor data from a mechanical system are often associated with important measurement information useful for machinery fault diagnosis. However, in practice the existence of background noise makes it difficult to identify the fault signature from the sensing data. This paper introduces the time-frequency manifold (TFM) concept into sensor data denoising and proposes a novel denoising method for reliable machinery fault diagnosis. The TFM signature reflects the intrinsic time-frequency structure of a non-stationary signal. The proposed method intends to realize data denoising by synthesizing the TFM using time-frequency synthesis and phase space reconstruction (PSR) synthesis. Due to the merits of the TFM in noise suppression and resolution enhancement, the denoised signal would have satisfactory denoising effects, as well as inherent time-frequency structure keeping. Moreover, this paper presents a clustering-based statistical parameter to evaluate the proposed method, and also presents a new diagnostic approach, called frequency probability time series (FPTS) spectral analysis, to show its effectiveness in fault diagnosis. The proposed TFM-based data denoising method has been employed to deal with a set of vibration sensor data from defective bearings, and the results verify that for machinery fault diagnosis the method is superior to two traditional denoising methods.

  3. Vibration Sensor Data Denoising Using a Time-Frequency Manifold for Machinery Fault Diagnosis

    PubMed Central

    He, Qingbo; Wang, Xiangxiang; Zhou, Qiang

    2014-01-01

    Vibration sensor data from a mechanical system are often associated with important measurement information useful for machinery fault diagnosis. However, in practice the existence of background noise makes it difficult to identify the fault signature from the sensing data. This paper introduces the time-frequency manifold (TFM) concept into sensor data denoising and proposes a novel denoising method for reliable machinery fault diagnosis. The TFM signature reflects the intrinsic time-frequency structure of a non-stationary signal. The proposed method intends to realize data denoising by synthesizing the TFM using time-frequency synthesis and phase space reconstruction (PSR) synthesis. Due to the merits of the TFM in noise suppression and resolution enhancement, the denoised signal would have satisfactory denoising effects, as well as inherent time-frequency structure keeping. Moreover, this paper presents a clustering-based statistical parameter to evaluate the proposed method, and also presents a new diagnostic approach, called frequency probability time series (FPTS) spectral analysis, to show its effectiveness in fault diagnosis. The proposed TFM-based data denoising method has been employed to deal with a set of vibration sensor data from defective bearings, and the results verify that for machinery fault diagnosis the method is superior to two traditional denoising methods. PMID:24379045

  4. Design and performance of a multimodal vibration-based energy harvester model for machine rotational frequencies

    NASA Astrophysics Data System (ADS)

    Sun, Shilong; Tse, Peter W.

    2017-06-01

    This paper presents the design of vibration-based energy harvester model whose resonance frequency can be tunable with the help of the various cantilever type beam structures: T-folded, E-folded without a tip mass, E-folded with one tip mass, and E-folded with two tip masses. The main contribution is to make an optimal structure that can scavenge the destructive vibration into the highest possible electric energy even the attached machine is running at a low rotational frequency. The finite element method and experimental verification were used to search for the optimal design that can make the operational bandwidth broader and yield the maximum power output. The results show that the design of E-folded with two tip masses can offer a first three resonance frequencies varied from 18.18 Hz to 26.8 Hz. Such a range of low frequency can well adopt the common range of rotational frequency of most of the rotary machines. From the observations of experiments, the maximum output of electricity could be guaranteed and harvested by an external circuit tailor-made for the beam structures.

  5. A Frequency-Independent Vibrational Energy Harvester using Symmetrically Charged Comb-Drive Electrodes with Heavily Doped Ion Electrets

    NASA Astrophysics Data System (ADS)

    Mitsuya, H.; Ashizawa, H.; Ishibashi, K.; Homma, H.; Ataka, M.; Hashiguchi, G.; Fujita, H.; Toshiyoshi, H.

    2016-11-01

    An energy harvester has been developed to efficiently earn energy from both cyclic and impulse vibrations by using a symmetric pair of comb-electrodes that are heavily doped with potassium-ions to form electrets. By equalizing the electromechanical forces on the opposing comb-drives, energy conversion efficiency is enhanced for both impulses and broad-frequency harmonic vibrations.

  6. Electrostatic MEMS vibration energy harvester for HVAC applications with impact-based frequency up-conversion

    NASA Astrophysics Data System (ADS)

    Oxaal, J.; Hella, M.; Borca-Tasciuc, D.-A.

    2016-12-01

    This paper reports on electrostatic MEMS vibration energy harvesters with gap-closing interdigitated electrodes, designed for and tested on HVAC air ducts. The harvesters were fabricated on SOI wafers with 200 µm device layer using a custom microfabrication process. Designs with aspects ratio (electrodes’ gap versus depth) of 10 and 20 were implemented, while the overall footprint was approximately 1 cm  ×  1 cm in both cases. In order to enhance the power output, a dual-level physical stopper system was designed to control the minimum gap between the electrodes, which is a key parameter in the conversion process. The dual-level stopper utilizes cantilever beams to absorb a portion of the impact energy as the electrodes approach the impact point, and a film of parylene with nanometer thickness deposited on the electrode sidewalls. The parylene layer defines the absolute minimum gap and provides electrical insulation. The fabricated devices were first tested on a vibration shaker to characterize the resonant behavior. Devices with aspect ratio 10 were found to exhibit frequency up-conversion, which enhances the amount of converted power. Devices with both aspect ratios were found to exhibits spring hardening due to impact with the stoppers and spring softening behavior at increasing voltage bias. The highest power measured on shaker table for sinusoidal vibrations was 3.13 µW (includes enhancement due to frequency up-conversion driven by impact) for aspect ratio 10, and 0.166 µW for aspect ratio 20. The corresponding dimensional figure-of-merit, defined as the power output normalized to vibration acceleration and frequency, squared voltage and device mass, was in the range of 10 · 10-8 m V-2 for both devices, about an order of magnitude higher than state-of-the-art. Testing was carried out on HVAC air duct vibrating with an RMS acceleration of 155 mg RMS, a primary frequency of 60 Hz and a PSD of 7.15 · 10-2 g2 Hz-1. The peak power measured was

  7. Chiral Vibrational Structures of Proteins at Interfaces Probed by Sum Frequency Generation Spectroscopy

    PubMed Central

    Fu, Li; Wang, Zhuguang; Yan, Elsa C.Y.

    2011-01-01

    We review the recent development of chiral sum frequency generation (SFG) spectroscopy and its applications to study chiral vibrational structures at interfaces. This review summarizes observations of chiral SFG signals from various molecular systems and describes the molecular origins of chiral SFG response. It focuses on the chiral vibrational structures of proteins and presents the chiral SFG spectra of proteins at interfaces in the C-H stretch, amide I, and N-H stretch regions. In particular, a combination of chiral amide I and N-H stretches of the peptide backbone provides highly characteristic vibrational signatures, unique to various secondary structures, which demonstrate the capacity of chiral SFG spectroscopy to distinguish protein secondary structures at interfaces. On the basis of these recent developments, we further discuss the advantages of chiral SFG spectroscopy and its potential application in various fields of science and technology. We conclude that chiral SFG spectroscopy can be a new approach to probe chiral vibrational structures of protein at interfaces, providing structural and dynamic information to study in situ and in real time protein structures and dynamics at interfaces. PMID:22272140

  8. Chiral vibrational structures of proteins at interfaces probed by sum frequency generation spectroscopy.

    PubMed

    Fu, Li; Wang, Zhuguang; Yan, Elsa C Y

    2011-01-01

    We review the recent development of chiral sum frequency generation (SFG) spectroscopy and its applications to study chiral vibrational structures at interfaces. This review summarizes observations of chiral SFG signals from various molecular systems and describes the molecular origins of chiral SFG response. It focuses on the chiral vibrational structures of proteins and presents the chiral SFG spectra of proteins at interfaces in the C-H stretch, amide I, and N-H stretch regions. In particular, a combination of chiral amide I and N-H stretches of the peptide backbone provides highly characteristic vibrational signatures, unique to various secondary structures, which demonstrate the capacity of chiral SFG spectroscopy to distinguish protein secondary structures at interfaces. On the basis of these recent developments, we further discuss the advantages of chiral SFG spectroscopy and its potential application in various fields of science and technology. We conclude that chiral SFG spectroscopy can be a new approach to probe chiral vibrational structures of protein at interfaces, providing structural and dynamic information to study in situ and in real time protein structures and dynamics at interfaces.

  9. Analysis of Vibration Exercise at Varying Frequencies by Different Fatigue Estimators.

    PubMed

    Xu, Lin; Rabotti, Chiara; Mischi, Massimo

    2016-12-01

    Vibration exercise (VE) has been suggested to improve muscle strength and power performance, due to enhanced neuromuscular demand. However, understanding of the most appropriate VE protocols is lacking, limiting the optimal use of VE in rehabilitation programs. In this study, the fatiguing effect of vibration at different frequencies was investigated by employing a force-modulation VE system. Twenty volunteers performed 12-s isometric contractions of the biceps brachii with a load consisting of a baseline force of 80% of their maximum voluntary contraction (MVC) and a superimposed sinusoidal force at 0 (control condition with no vibration), 20, 30, and 40 Hz. Mechanical fatigue was estimated by assessment of MVC decay after each task while myoelectric fatigue was estimated by analysis of multichannel electromyography (EMG) signals recorded during VE. EMG conduction velocity, spectral compression, power, and fractal dimension were estimated as indicators of myoelectric fatigue. Our results suggest vibration, in particular at 30 Hz, to produce a larger degree of fatigue as compared to control condition. These results motivate further research aiming at introducing VE in rehabilitation programs with improved training protocols.

  10. Vibration Powered RF-Transponder for Sensing Low Frequency Motion Events

    NASA Astrophysics Data System (ADS)

    Gupta, S. K.; Pinrod, V.; Nadig, S.; Davaji, B.; Lal, A.

    2016-11-01

    Vibration energy harvesting offers a pathway to developing battery-less sensing solutions to be deployed in wireless sensor network nodes. The integration of the energy harvesters require regulation by power conditioning and control circuitry that consume some of the energy generated, reducing the effective energy available for node function. By designing a unique 3D-printed plastic structure for low frequency sensitivity and mechanical switching, and a lateral PZT bimorph for capturing energy from environmental vibrations, we report a zero-power consumption RF-transponder capable of detecting and reporting motion events without a battery. We have successfully picked up wireless transmissions on an external receiver placed ∼25cm away from the transponder, shaken at 0.75 g and 20 Hz. We have additionally demonstrated the ability to harvest energy from 5 Hz vibrations up to just under 150 Hz. When placed on an oil-based electric generator, which vibrates when operating, the RF-transponder has successfully picked up the differing harmonics to identify the mode of operation as the economy or regular power setting.

  11. Muscle activity and acceleration during whole body vibration: effect of frequency and amplitude.

    PubMed

    Pollock, Ross D; Woledge, Roger C; Mills, Kerry R; Martin, Finbarr C; Newham, Di J

    2010-10-01

    Whole body vibration may improve muscle and bone strength, power and balance although contradictory findings have been reported. Prolonged exposure may result in adverse effects. We investigated the effects of high (5.5 mm) and low (2.5mm) amplitude whole body vibration at various frequencies (5-30 Hz) on muscle activity and acceleration throughout the body. Surface electromyographic activity was recorded from 6 leg muscles in 12 healthy adults (aged 31.3 (SD 12.4) years). The average rectified acceleration of the toe, ankle, knee, hip and head was recorded from 15 healthy adults (36 (SD 12.1) years) using 3D motion analysis. Whole body vibration increased muscle activity 5-50% of maximal voluntary contraction with the greatest increase in the lower leg. Activity was greater with high amplitude at all frequencies, however this was not always significant (P<0.05-0.001). Activation tended to increase linearly with frequency in all muscles except gluteus maximus and biceps femoris. Accelerations throughout the body ranged from approximately 0.2 to 9 g and decreased with distance from the platform. Acceleration at the head was always < 0.33 g. The greatest acceleration of the knee and hip occurred at approximately 15 Hz and thereafter decreased with increasing frequency. Above the knee at frequencies > 15 Hz acceleration decreased with distance from the platform. This was associated with increased muscle activity, presumably due to postural control and muscle tuning mechanisms. The minimal acceleration at the head reduces the likelihood of adverse reactions. The levels of activation are unlikely to cause hypertrophy in young healthy individuals but may be sufficient in weak and frail people. 2010 Elsevier Ltd. All rights reserved.

  12. The vibrating reed frequency meter: digital investigation of an early cochlear model

    PubMed Central

    Wit, Hero P.

    2015-01-01

    The vibrating reed frequency meter, originally employed by Békésy and later by Wilson as a cochlear model, uses a set of tuned reeds to represent the cochlea’s graded bank of resonant elements and an elastic band threaded between them to provide nearest-neighbour coupling. Here the system, constructed of 21 reeds progressively tuned from 45 to 55 Hz, is simulated numerically as an elastically coupled bank of passive harmonic oscillators driven simultaneously by an external sinusoidal force. To uncover more detail, simulations were extended to 201 oscillators covering the range 1–2 kHz. Calculations mirror the results reported by Wilson and show expected characteristics such as traveling waves, phase plateaus, and a response with a broad peak at a forcing frequency just above the natural frequency. The system also displays additional fine-grain features that resemble those which have only recently been recognised in the cochlea. Thus, detailed analysis brings to light a secondary peak beyond the main peak, a set of closely spaced low-amplitude ripples, rapid rotation of phase as the driving frequency is swept, frequency plateaus, clustering, and waxing and waning of impulse responses. Further investigation shows that each reed’s vibrations are strongly localised, with small energy flow along the chain. The distinctive set of equally spaced ripples is an inherent feature which is found to be largely independent of boundary conditions. Although the vibrating reed model is functionally different to the standard transmission line, its cochlea-like properties make it an intriguing local oscillator model whose relevance to cochlear mechanics needs further investigation. PMID:26623180

  13. a Hamiltonian to Obtain a Global Frequency Analysis of all the Vibrational Bands of Ethane

    NASA Astrophysics Data System (ADS)

    Moazzen-Ahmadi, Nasser; Norooz Oliaee, Jalal

    2016-06-01

    The interest in laboratory spectroscopy of ethane stems from the desire to understand the methane cycle in the atmospheres of planets and their moons and from the importance of ethane as a trace species in the terrestrial atmosphere. Solar decomposition of methane in the upper part of these atmospheres followed by a series of reactions leads to a variety of hydrocarbon compounds among which ethane is often the second most abundant species. Because of its high abundance, ethane spectra have been measured by Voyager and Cassini in the regions around 30, 12, 7, and 3 μm. Therefore, a complete knowledge of line parameters of ethane is crucial for spectroscopic remote sensing of planetary atmospheres. Experimental characterization of torsion-vibration states of ethane lying below 1400 cm-1 have been made previously, but extension of the Hamiltonian model for treatment of the strongly perturbed νb{8} fundamental and the complex band system of ethane in the 3 micron region requires careful examination of the operators for many new torsionally mediated vibration-rotation interactions. Following the procedures outlined by Hougen, we have re-examined the transformation properties of the total angular momentum, the translational and vibrational coordinates and momenta of ethane, and for vibration-torsion-rotation interaction terms constructed by taking products of these basic operators. It is found that for certain choices of phase, the doubly degenerate vibrational coordinates with and symmetry can be made to transform under the group elements in such a way as to yield real matrix elements for the torsion-vibration-rotation couplings whereas other choices of phase may require complex algebra. In this talk, I will discuss the construction of a very general torsion-vibration-rotation Hamiltonian for ethane, as well as the prospect for using such a Hamiltonian to obtain a global frequency analysis (based in large part on an extension of earlier programs and ethane fits^a from

  14. Application of ground vibration frequency spectrum analysis as a tool for optimizing the blast design in large open pit mines

    SciTech Connect

    Rao, K.R.

    1994-12-31

    This paper explains the methodology for assessing the efficiency of rockmass fragmentation by explosive blasting, from ground vibration frequency spectrum analysis of the blast event. Explosives are used in the mining, quarrying and construction industries for fragmenting rockmass to a suitable size. When an explosive charge is detonated, in addition to fragmenting the rockmass, it will also generate ground vibration and air vibrations. Efficiency of a blast depend upon percentage of blast energy wasted in generating ground vibrations and air vibrations. This in turn will depend upon rockmass characteristics, amount of explosive energy used per delay and spatial distribution of explosive in the rockmass. Ground vibrations and air vibrations, arising out of explosive detonation in a rockmass, could be captured by micro-computer based engineering seismograph and sound level meter. Typical frequency range indicative of efficient rockmass fragmentation for a particular rockmass can be identified from ground vibration frequency spectra analysis of the blast event on a personal computer applying Fast Fourier transforms (FFT). The typical frequency range indicative of efficient rockmass fragmentation depends upon rockmass impedance and can be estimated from rockmass characteristics and monitoring few trial blasts. Blast event efficiency is estimated by comparing the typical frequency range with the dominant frequency range of the blast event record. A large number of blast events monitored and analyzed by the author in different rockmass formations and correlation of the results with observations made while fragmented material is lifted and loaded into trucks indicated that ground vibration frequency spectrum analysis could be used as a reliable and cost effective tool for assessing the blasting efficiency and optimizing blast design in large open-pit mines.

  15. Strain-induced vibration and temperature sensing BOTDA system combined frequency sweeping and slope-assisted techniques.

    PubMed

    Hu, Junhui; Xia, Lan; Yang, Li; Quan, Wenwen; Zhang, Xuping

    2016-06-13

    A BOTDA sensing scheme combined frequency sweeping and slope-assisted techniques is proposed and experimentally demonstrated for simultaneously temperature and strain-induced vibration sensing. In this scheme, during sweeping Brillouin gain spectrum (BGS) for temperature measurement, we simultaneously perform FFT to the time-domain traces whose probe-pump frequency difference (PPFD) is within the FWHM of the BGS at each position of fiber, and the location and the frequency of the strain-induced vibration event can be acquired based on SA-BOTDA technique. In this way, the vibration can be continuously measured at each selected working frequency point during the BGS scanning process and multiple measurements of vibration event can be completed in one whole BGS scanning process. Meanwhile, double sidebands probe method is employed to reduce the nonlocal effects. In our experiment, a temperature event and two vibration events with the frequency of 7.00Hz or 10.00Hz are simultaneously measured near the end of 10.6km long sensing fiber in a traditional BOTDA system. The system shows 1.2°C temperature accuracy and 0.67Hz frequency resolution, as well as a 3m spatial resolution. The proposed method may find some potential applications where both the strain-induced vibration frequency and temperature are the diagnostic objects.

  16. Vibration Modes at Terahertz and Infrared Frequencies of Ionic Liquids Consisting of an Imidazolium Cation and a Halogen Anion

    PubMed Central

    Yamada, Toshiki; Tominari, Yukihiro; Tanaka, Shukichi; Mizuno, Maya; Fukunaga, Kaori

    2014-01-01

    The terahertz and infrared frequency vibration modes of room-temperature ionic liquids with imidazolium cations and halogen anions were extensively investigated. There is an intermolecular vibrational mode between the imidazolium ring of an imidazolium cation, a halogen atomic anion with a large absorption coefficient and a broad bandwidth in the low THz frequency region (13–130 cm−1), the intramolecular vibrational modes of the alkyl-chain part of an imidazolium cation with a relatively small absorption coefficient in the mid THz frequency region (130–500 cm−1), the intramolecular skeletal vibrational modes of an imidazolium ring affected by the interaction between the imidazolium ring, and a halogen anion with a relatively large absorption coefficient in a high THz frequency region (500–670 cm−1). Interesting spectroscopic features on the interaction between imidazolium cations and halogen anions was also obtained from spectroscopic studies at IR frequencies (550–3300 cm−1). As far as the frequency of the intermolecular vibrational mode is concerned, we found the significance of the reduced mass in determining the intermolecular vibration frequency. PMID:28788255

  17. Temperature dependence of the low frequency dynamics of myoglobin. Measurement of the vibrational frequency distribution by inelastic neutron scattering.

    PubMed Central

    Cusack, S; Doster, W

    1990-01-01

    Inelastic neutron scattering spectra of myoglobin hydrated to 0.33 g water (D2O)/g protein have been measured in the low frequency range (1-150 cm-1) at various temperatures between 100 and 350 K. The spectra at low temperatures show a well-resolved maximum in the incoherent dynamic structure factor Sinc(q, omega) at approximately 25 cm-1 and no elastic broadening. This maximum becomes gradually less distinct above 180 K due to the increasing amplitude of quasielastic scattering which extends out to 30 cm-1. The vibrational frequency distribution derived independently at 100 and 180 K are very similar, suggesting harmonic behavior at these temperatures. This result has been used to separate the vibrational motion from the quasielastic motion at temperatures above 180 K. The form of the density of states of myoglobin is discussed in relation to that of other amorphous systems, to theoretical calculations of low frequency modes in proteins, and to previous observations by electron-spin relaxation of fractal-like spectral properties of proteins. The onset of quasielastic scattering above 180 K is indicative of a dynamic transition of the system and correlates with an anomalous increase in the atomic mean-squared displacements observed by Mössbauer spectroscopy (Parak, F., E. W. Knapp, and D. Kucheida. 1982. J. Mol. Biol. 161: 177-194.) and inelastic neutron scattering (Doster, W., S. Cusack, and W. Petry, 1989. Nature [Lond.]. 337: 754-756.) Similar behavior is observed for a hydrated powder of lysozyme suggesting that the low frequency dynamics of globular proteins have common features. PMID:2166599

  18. On the efficacy of the wavelet decomposition for high frequency vibration analyses

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Cheng, L.

    2016-10-01

    This paper reports the extraordinary ability of the wavelet decomposition for vibration analyses under the framework of Rayleigh-Ritz method. Using a beam as an example, Daubechies wavelet scale functions are used as admissible functions for decomposing the flexural displacement of the structure, along with the artificial springs at the boundary, to predict vibration of an Euler-Bernoulli beam in an extremely large frequency range. It is shown that the use of wavelet basis allows reaching very high frequencies, typically covering more than 1000 modes using conventional computational facility within the available numerical dynamics of the computers with no particular care needed for round-off errors. As a side benefit, the use of spring boundary also allows handling any elastic boundary conditions through a dynamic contribution in the Hamiltonian of the beam. The wavelet decomposed approach combines the flexibility of the global methods and the accuracy of local methods by inheriting the versatility of the Rayleigh-Ritz approach and the superior fitting ability of the wavelets. Numerical results on both free and forced vibrations are given, in excellent agreement with predictions of classical methods.

  19. The effect of lubricant supply and frequency upon the behaviour of EHD films subjected to vibrations

    NASA Astrophysics Data System (ADS)

    Glovnea, R.; Zhang, X.; Sugimura, J.

    2017-02-01

    Machine elements such as rolling element bearings or gears often experience vibrations due to for example geometrical inaccuracies, shock loading, rotating unbalanced masses, and others. These machine elements rely on a very thin lubricant film to protect the metallic surfaces from direct contact and eventual damage. During rapid variation of load the elastohydrodynamic contact is influenced by the so-called squeeze film effect, however, when both entrainment and squeeze are present, the conditions of film formation are more complex. It is expected that the lubricant film thickness is influenced by the amplitude and frequency of the vibrations. At the same time, as it is known that the film thickness is established in the inlet of the contact, it is equally important to evaluate what is the role played by the supply of lubricant to the contact under oscillatory conditions. To date there are not many studies on the effect of the oscillatory motion parameters upon the behaviour of the lubricant film. In this study the focus is on the effect of the frequency of vibrations and the supply of lubricant upon the film thickness.

  20. Design of piezoelectric MEMS cantilever for low-frequency vibration energy harvester

    NASA Astrophysics Data System (ADS)

    Takei, Ryohei; Makimoto, Natsumi; Okada, Hironao; Itoh, Toshihiro; Kobayashi, Takeshi

    2016-06-01

    We report the design of piezoelectric MEMS cantilevers formed on a silicon-on-insulator wafer to efficiently harvest electrical power from harmonic vibration with a frequency of approximately 30 Hz. Numerical simulation indicates that a >4-µm-thick top silicon layer and >3-µm-thick piezoelectric film are preferable to maximize the output electrical power. An in-plane structure of the cantilever is also designed retaining the footprint of the cantilever. The simulation results indicate that the output power is maximized when the length ratio of the proof mass to the cantilever beam is 1.5. To ensure the accuracy of the simulation, we fabricated and characterized cantilevers with a 10-µm-thick top silicon layer and a 1.8-µm-thick piezoelectric film, resulting in 0.21 µW at a vibration of 0.5 m/s2 and 25.1 Hz. The measured output power is in agreement with the simulated value, meaning that the design is significantly reliable for low-frequency vibration energy harvesters.

  1. Instantaneous pair theory for high-frequency vibrational energy relaxation in fluids

    NASA Astrophysics Data System (ADS)

    Larsen, Ross E.; Stratt, Richard M.

    1999-01-01

    Notwithstanding the long and distinguished history of studies of vibrational energy relaxation, exactly how it is that high frequency vibrations manage to relax in a liquid remains somewhat of a mystery. Both experimental and theoretical approaches seem to say that there is a natural frequency range associated with intermolecular motion in liquids, typically spanning no more than a few hundred cm-1. Landau-Teller-type theories explain rather easily how a solvent can absorb any vibrational energy within this "band," but how is it that molecules can rid themselves of superfluous vibrational energies significantly in excess of these values? In this paper we develop a theory for such processes based on the idea that the crucial liquid motions are those that most rapidly modulate the force on the vibrating coordinate — and that by far the most important of these motions are those involving what we have called the mutual nearest neighbors of the vibrating solute. Specifically, we suggest that whenever there is a single solvent molecule sufficiently close to the solute that the solvent and solute are each other's nearest neighbors, then the instantaneous scattering dynamics of the solute-solvent pair alone suffices to explain the high-frequency relaxation. This highly reduced version of the dynamics has implications for some of the previous theoretical formulations of this problem. Previous instantaneous-normal-mode theories allowed us to understand the origin of a band of liquid frequencies, and even had some success in predicting relaxation within this band, but lacking a sensible picture of the effects of liquid anharmonicity on dynamics, were completely unable to treat higher frequency relaxation. When instantaneous-normal-mode dynamics is used to evaluate the instantaneous pair theory, though, we end up with a multiphonon picture of the relaxation which is in excellent agreement with the exact high-frequency dynamics — suggesting that the critical anharmonicity

  2. Stick-slip failure in granular experiments: the role of low-frequency vibrational modes

    NASA Astrophysics Data System (ADS)

    Brzinski, T., III; Daniels, K.

    2014-12-01

    The intermittent nature of strain at geological faults is a consequence of the loss of rigidity of the gouge. Due to the granular nature of the gouge, we take insight from granular physics in order to characterize the role of gouge in the generation of seismic events. In static granular packings, the loss of rigidity has been observed to be associated with an excess in low-frequency vibrational modes. The same holds true in both molecular and colloidal glasses, suggesting that excess low-frequency vibrational modes are a general feature in the failure of disordered solids. Therefore, we seek a relationship between these low-frequency modes and spatiotemporal patterns of failure by studying an experimental analog to a geological fault. Specifically, we measure the acoustic emissions from jammed, quasi-2D granular packings under shear. We use a split-bottom annular shear geometry, driven with a linear-ramp torque in order to generate stick-slip behavior, and observe intervals of both periodic and aperiodic slip. We investigate how low-frequency emissions are associated with both local and global slip events of various magnitudes and directions. Twelve piezoelectric acoustic receivers, an imaging system, and high-resolution stress/strain sensors enable direct comparison of acoustic properties as the system approaches failure. The use of photoelastic grains enables local measurement of changes to the internal stresses.

  3. Composite 3D-printed metastructures for low-frequency and broadband vibration absorption.

    PubMed

    Matlack, Kathryn H; Bauhofer, Anton; Krödel, Sebastian; Palermo, Antonio; Daraio, Chiara

    2016-07-26

    Architected materials that control elastic wave propagation are essential in vibration mitigation and sound attenuation. Phononic crystals and acoustic metamaterials use band-gap engineering to forbid certain frequencies from propagating through a material. However, existing solutions are limited in the low-frequency regimes and in their bandwidth of operation because they require impractical sizes and masses. Here, we present a class of materials (labeled elastic metastructures) that supports the formation of wide and low-frequency band gaps, while simultaneously reducing their global mass. To achieve these properties, the metastructures combine local resonances with structural modes of a periodic architected lattice. Whereas the band gaps in these metastructures are induced by Bragg scattering mechanisms, their key feature is that the band-gap size and frequency range can be controlled and broadened through local resonances, which are linked to changes in the lattice geometry. We demonstrate these principles experimentally, using advanced additive manufacturing methods, and inform our designs using finite-element simulations. This design strategy has a broad range of applications, including control of structural vibrations, noise, and shock mitigation.

  4. An efficient low frequency horizontal diamagnetic levitation mechanism based vibration energy harvester

    NASA Astrophysics Data System (ADS)

    Palagummi, S.; Yuan, F. G.

    2016-04-01

    This article identifies and studies key parameters that characterize a horizontal diamagnetic levitation (HDL) mechanism based low frequency vibration energy harvester with the aim of enhancing performance metrics such as efficiency and volume figure of merit (FoMv). The HDL mechanism comprises of three permanent magnets and two diamagnetic plates. Two of the magnets, aka lifting magnets, are placed co-axially at a distance such that each attract a centrally located magnet, aka floating magnet, to balance its weight. This floating magnet is flanked closely by two diamagnetic plates which stabilize the levitation in the axial direction. The influence of the geometry of the floating magnet, the lifting magnet and the diamagnetic plate are parametrically studied to quantify their effects on the size, stability of the levitation mechanism and the resonant frequency of the floating magnet. For vibration energy harvesting using the HDL mechanism, a coil geometry and eddy current damping are critically discussed. Based on the analysis, an efficient experimental system is setup which showed a softening frequency response with an average system efficiency of 25.8% and a FoMv of 0.23% when excited at a root mean square acceleration of 0.0546 m/s2 and at frequency of 1.9 Hz.

  5. Ultralow frequency acoustic bandgap and vibration energy recovery in tetragonal folding beam phononic crystal

    NASA Astrophysics Data System (ADS)

    Gao, Nansha; Wu, Jiu Hui; Yu, Lie; Hou, Hong

    2016-06-01

    This paper investigates ultralow frequency acoustic properties and energy recovery of tetragonal folding beam phononic crystal (TFBPC) and its complementary structure. The dispersion curve relationships, transmission spectra and displacement fields of the eigenmodes are studied with FEA in detail. Compared with the traditional three layer phononic crystal (PC) structure, this structure proposed in this paper not only unfold bandgaps (BGs) in lower frequency range (below 300 Hz), but also has lighter weight because of beam structural cracks. We analyze the relevant physical mechanism behind this phenomenon, and discuss the effects of the tetragonal folding beam geometric parameters on band structure maps. FEM proves that the multi-cell structures with different arrangements have different acoustic BGs when compared with single cell structure. Harmonic frequency response and piezoelectric properties of TFBPC are specifically analyzed. The results confirm that this structure does have the recovery ability for low frequency vibration energy in environment. These conclusions in this paper could be indispensable to PC practical applications such as BG tuning and could be applied in portable devices, wireless sensor, micro-electro mechanical systems which can recycle energy from vibration environment as its own energy supply.

  6. Composite 3D-printed metastructures for low-frequency and broadband vibration absorption

    NASA Astrophysics Data System (ADS)

    Matlack, Kathryn H.; Bauhofer, Anton; Krödel, Sebastian; Palermo, Antonio; Daraio, Chiara

    2016-07-01

    Architected materials that control elastic wave propagation are essential in vibration mitigation and sound attenuation. Phononic crystals and acoustic metamaterials use band-gap engineering to forbid certain frequencies from propagating through a material. However, existing solutions are limited in the low-frequency regimes and in their bandwidth of operation because they require impractical sizes and masses. Here, we present a class of materials (labeled elastic metastructures) that supports the formation of wide and low-frequency band gaps, while simultaneously reducing their global mass. To achieve these properties, the metastructures combine local resonances with structural modes of a periodic architected lattice. Whereas the band gaps in these metastructures are induced by Bragg scattering mechanisms, their key feature is that the band-gap size and frequency range can be controlled and broadened through local resonances, which are linked to changes in the lattice geometry. We demonstrate these principles experimentally, using advanced additive manufacturing methods, and inform our designs using finite-element simulations. This design strategy has a broad range of applications, including control of structural vibrations, noise, and shock mitigation.

  7. Composite 3D-printed metastructures for low-frequency and broadband vibration absorption

    PubMed Central

    Bauhofer, Anton; Krödel, Sebastian; Palermo, Antonio; Daraio, Chiara

    2016-01-01

    Architected materials that control elastic wave propagation are essential in vibration mitigation and sound attenuation. Phononic crystals and acoustic metamaterials use band-gap engineering to forbid certain frequencies from propagating through a material. However, existing solutions are limited in the low-frequency regimes and in their bandwidth of operation because they require impractical sizes and masses. Here, we present a class of materials (labeled elastic metastructures) that supports the formation of wide and low-frequency band gaps, while simultaneously reducing their global mass. To achieve these properties, the metastructures combine local resonances with structural modes of a periodic architected lattice. Whereas the band gaps in these metastructures are induced by Bragg scattering mechanisms, their key feature is that the band-gap size and frequency range can be controlled and broadened through local resonances, which are linked to changes in the lattice geometry. We demonstrate these principles experimentally, using advanced additive manufacturing methods, and inform our designs using finite-element simulations. This design strategy has a broad range of applications, including control of structural vibrations, noise, and shock mitigation. PMID:27410042

  8. Modal analysis of 2-D sedimentary basin from frequency domain decomposition of ambient vibration array recordings

    NASA Astrophysics Data System (ADS)

    Poggi, Valerio; Ermert, Laura; Michel, Clotaire; Fäh, Donat

    2014-05-01

    The frequency domain decomposition is a well-established spectral technique used in civil engineering to analyze and monitor the modal response of buildings and structures. The method is based on singular value decomposition of the cross-power spectral density matrix from simultaneous array recordings of ambient vibration. This method is advantageous to retrieve not only the resonance frequencies of the investigated structure, but also the corresponding modal shapes without using an absolute reference. This is an important piece of information, which can be used to identify areas of minimum and maximum ground motion on the structure. We apply this approach to evaluate the SH and P-SV resonance characteristics of 2D Alpine sedimentary valleys through decomposition of ambient vibration recordings from linear seismic arrays deployed perpendicularly to the valley axis. Results are presented for a set of synthetic models, initially used to validate the method, and for a real acquisition survey performed in the Rhone valley (Switzerland). For the real case, up to six separate resonant frequencies, together with their corresponding modal shapes, were retrieved for the SH case using the frequency domain decomposition method. We then compare these mode shapes with results from classical site-to-reference spectral ratios and solutions from analytical and numerical modal analysis.

  9. Diffusion regime for high-frequency vibrations of randomly heterogeneous structures.

    PubMed

    Savin, Eric

    2008-12-01

    The evolution of the high-frequency vibrational energy density of slender heterogeneous structures such as Timoshenko beams or thick shells is depicted by transport equations or radiative transfer equations (RTEs) in the presence of random heterogeneities. A diffusive regime arises when their correlation lengths are comparable to the wavelength, among other possible situations, and waves are multiply scattered. The purpose of this paper is to expound how diffusion approximations of the RTEs for elastic structures can be derived and to discuss the relevance of the vibrational conductivity analogy invoked in the structural acoustics literature. Its main contribution is the consideration of a heterogeneous background medium with varying parameters and the effects of polarization of elastic waves. The paper also outlines some of the remarkable features of the diffusive regime: depolarization of waves, energy equipartition, and asymptotic Fick's law.

  10. Frequency-resolved optical gating technique for retrieving the amplitude of a vibrational wavepacket

    NASA Astrophysics Data System (ADS)

    Nabekawa, Yasuo; Furukawa, Yusuke; Okino, Tomoya; Amani Eilanlou, A.; Takahashi, Eiji J.; Yamanouchi, Kaoru; Midorikawa, Katsumi

    2015-06-01

    We propose a novel method to determine the complex amplitude of each eigenfunction composing a vibrational wavepacket of / molecular ions evolving with a ~10 fs time scale. We find that the two-dimensional spectrogram of the kinetic energy release (KER) of H+/D+ fragments plotted against the time delay of the probe pulse is equivalent to the spectrogram used in the frequency-resolved optical gating (FROG) technique to retrieve the complex amplitude of an ultrashort optical pulse. By adapting the FROG algorithm to the delay-KER spectrogram of the vibrational wavepacket, we have successfully reconstructed the complex amplitude. The deterioration in retrieval accuracy caused by the bandpass filter required to process actual experimental data is also discussed.

  11. Low Frequency Vibrating Optical System for Detecting Objects Buried in Turbid Media: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Cywiak, D.; Cywiak, M.; Pérez-Solano, R.; Gutiérrez-Juárez, G.

    2012-11-01

    Preliminary results of an in-plane vibrating system to image objects buried in turbid media are presented. The incident optical beam is vibrated in a periodic back-and-forth motion at low frequency and small constant amplitude in a plane perpendicular to the direction of the beam. The detection is performed in the AC mode, blocking the DC component. The system shows a dramatic increase in the AC signal whenever the target boundary intersects with the reference line between the incident laser beam and a photodiode after a small aperture. The system was capable to render visible 2 mm width objects buried at depths up to 3 cm from the front surface of a 1% intralipid sample.

  12. Vibrational Frequencies of Fractionally Charged Molecular Species: Benchmarking DFT Results against ab Initio Calculations.

    PubMed

    Bâldea, Ioan

    2017-03-23

    Recent advances in nano/molecular electronics and electrochemistry made it possible to continuously tune the fractional charge q of single molecules and to use vibrational spectroscopic methods to monitor such changes. Approaches to compute vibrational frequencies ω(q) of fractionally charged species based on the density functional theory (DFT) are faced with an important issue: the basic quantity used in these calculations, the total energy, should exhibit piecewise linearity with respect to the fractional charge, but approximate, commonly utilized exchange correlation functionals do not obey this condition. In this paper, with the aid of a simple and representative example, we benchmark results for ω(q) obtained within the DFT against ab initio methods, namely, coupled cluster singles and doubles and also second- and third-order Møller-Plesset perturbation) expansions. These results indicate that, in spite of missing the aforementioned piecewise linearity, DFT-based values ω(q) can reasonably be trusted.

  13. Frequency-varying synchronous micro-vibration suppression for a MSFW with application of small-gain theorem

    NASA Astrophysics Data System (ADS)

    Peng, Cong; Fan, Yahong; Huang, Ziyuan; Han, Bangcheng; Fang, Jiancheng

    2017-01-01

    This paper presents a novel synchronous micro-vibration suppression method on the basis of the small gain theorem to reduce the frequency-varying synchronous micro-vibration forces for a magnetically suspended flywheel (MSFW). The proposed synchronous micro-vibration suppression method not only eliminates the synchronous current fluctuations to force the rotor spinning around the inertia axis, but also considers the compensation caused by the displacement stiffness in the permanent-magnet (PM)-biased magnetic bearings. Moreover, the stability of the proposed control system is exactly analyzed by using small gain theorem. The effectiveness of the proposed micro-vibration suppression method is demonstrated via the direct measurement of the disturbance forces for a MSFW. The main merit of the proposed method is that it provides a simple and practical method in suppressing the frequency varying micro-vibration forces and preserving the nominal performance of the baseline control system.

  14. Low-Magnitude, High-Frequency Vibration Fails to Accelerate Ligament Healing but Stimulates Collagen Synthesis in the Achilles Tendon

    PubMed Central

    Thompson, William R.; Keller, Benjamin V.; Davis, Matthew L.; Dahners, Laurence E.; Weinhold, Paul S.

    2015-01-01

    Background: Low-magnitude, high-frequency vibration accelerates fracture and wound healing and prevents disuse atrophy in musculoskeletal tissues. Purpose: To investigate the role of low-magnitude, high-frequency vibration as a treatment to accelerate healing of an acute ligament injury and to examine gene expression in the intact Achilles tendon of the injured limb after low-magnitude, high-frequency vibration. Study Design: Controlled laboratory study. Methods: Complete surgical transection of the medial collateral ligament (MCL) was performed in 32 Sprague-Dawley rats, divided into control and low-magnitude, high-frequency vibration groups. Low-magnitude, high-frequency vibration started on postoperative day 2, and rats received vibration for 30 minutes a day for 12 days. All rats were sacrificed 2 weeks after the operation, and their intact and injured MCLs were biomechanically tested or used for histological analysis. Intact Achilles tendons from the injured limb were evaluated for differences in gene expression. Results: Mechanical testing revealed no differences in the ultimate tensile load or the structural stiffness between the control and vibration groups for either the injured or intact MCL. Vibration exposure increased gene expression of collagen 1 alpha (3-fold), interleukin 6 (7-fold), cyclooxygenase 2 (5-fold), and bone morphogenetic protein 12 (4-fold) in the intact Achilles tendon when compared with control tendons (P < .05). Conclusion: While no differences were observed in the mechanical or histological properties of the fully transected MCL after low-magnitude, high-frequency vibration treatment, significant enhancements in gene expression were observed in the intact Achilles tendon. These included collagen, several inflammatory cytokines, and growth factors critical for tendons. Clinical Relevance: As low-magnitude, high-frequency vibration had no negative effects on ligament healing, vibration therapy may be a useful tool to accelerate healing

  15. Time-domain filtered-x-Newton narrowband algorithms for active isolation of frequency-fluctuating vibration

    NASA Astrophysics Data System (ADS)

    Li, Yan; He, Lin; Shuai, Chang-geng; Wang, Fei

    2016-04-01

    A time-domain filtered-x Newton narrowband algorithm (the Fx-Newton algorithm) is proposed to address three major problems in active isolation of machinery vibration: multiple narrowband components, MIMO coupling, and amplitude and frequency fluctuations. In this algorithm, narrowband components are extracted by narrowband-pass filters (NBPF) and independently controlled by multi-controllers, and fast convergence of the control algorithm is achieved by inverse secondary-path filtering of the extracted sinusoidal reference signal and its orthogonal component using L×L numbers of 2nd-order filters in the time domain. Controller adapting and control signal generation are also implemented in the time domain, to ensure good real-time performance. The phase shift caused by narrowband filter is compensated online to improve the robustness of control system to frequency fluctuations. A double-reference Fx-Newton algorithm is also proposed to control double sinusoids in the same frequency band, under the precondition of acquiring two independent reference signals. Experiments are conducted with an MIMO single-deck vibration isolation system on which a 200 kW ship diesel generator is mounted, and the algorithms are tested under the vibration alternately excited by the diesel generator and inertial shakers. The results of control over sinusoidal vibration excited by inertial shakers suggest that the Fx-Newton algorithm with NBPF have much faster convergence rate and better attenuation effect than the Fx-LMS algorithm. For swept, frequency-jumping, double, double frequency-swept and double frequency-jumping sinusoidal vibration, and multiple high-level harmonics in broadband vibration excited by the diesel generator, the proposed algorithms also demonstrate large vibration suppression at fast convergence rate, and good robustness to vibration with frequency fluctuations.

  16. Modal identification using the frequency-scale domain decomposition technique of ambient vibration responses

    NASA Astrophysics Data System (ADS)

    Le, Thien-Phu; Argoul, Pierre

    2016-12-01

    This paper proposes a new modal identification method of ambient vibration responses. The application of the singular value decomposition to continuous wavelet transform of power spectral density matrix gives singular values and singular vectors in frequency-scale domain. Analytical development shows a direct relation between local maxima in frequency-scale representation of singular values and modal parameters. This relation is then carried on for the identification of modal parameters via a complete practical procedure. The main novelties of this work involve the new formulation in frequency-scale domain and the capacity for the identification of modal parameters without the step of ridges extraction in comparison with previous wavelet-based modal identification methods.

  17. A vibration isolation system in low frequency excitation region using negative stiffness structure for vehicle seat

    NASA Astrophysics Data System (ADS)

    Le, Thanh Danh; Ahn, Kyoung Kwan

    2011-12-01

    This paper designs and fabricates a vibration isolation model for improving vibration isolation effectiveness of the vehicle seat under low excitation frequencies. The feature of the proposed system is to use two symmetric negative stiffness structures (NSS) in parallel to a positive stiffness structure. Here, theoretical analysis of the proposed system is clearly presented. Then, the design procedure is derived so that the resonance peak of frequency-response curve drifts to the left, the load support capacity of the system is maintained, the total size of the system is reduced for easy practical application and especially, the bending of the frequency-response curve is minimized. Next the dynamic equation of the proposed system is set up. Then, the harmonic balance (HB) method is employed to seek the characteristic of the motion transmissibility of the proposed system at the steady state for each of the excitation frequency. From this characteristic, the curves of the motion transmission are predicted according to the various values of the configurative parameters of the system. Then, the time responses to the sinusoidal, multi frequency and random excitations are also investigated by simulation and experiment. In addition, the isolation performance comparison between the system with NSS and system without NSS is realized. The simulation results reveal that the proposed system has larger frequency region of isolation than that of the system without NSS. The experimental results confirm also that with a random excitation mainly spreading from 0.1 to 10 Hz, the isolation performance of the system with NSS is greatly improved, where the RMS values of the mass displacement may be reduced to 67.2%, whereas the isolation performance of the system without NSS is bad. Besides, the stability of the steady-state response is also studied. Finally, some conclusions are given.

  18. Broadband Sum-Frequency Generation Spectroscopy of High-Frequency Vibrations of Water Molecules at Silica Surfaces

    NASA Astrophysics Data System (ADS)

    Isaienko, Oleksandr; Nihonyanagi, Satoshi; Sil, Devika; Borguet, Eric

    2012-06-01

    Building on our discovery of a method to extend noncollinear optical parametric amplification to a broad class of materials, we developed one of the first sources generating ultrabroadband infrared pulses with bandwidths Δν > 2500 cm-1 in the near-IR (λ = 1.1-1.6 μm) and Δν > 1000 cm-1 in the mid-IR (λ = 1.7-3.5 μm; ν = 2800-6000 cm-1). The ultra-broadband IR source enabled surface-sensitive sum-frequency generation (SFG) vibrational spectroscopy of mineral-water interfaces crucial in many natural and man-made processes such as ion exchange in geochemical environments and oil extraction from tar sands. This novel ultrabroadband IR source allowed the acquisition of SFG spectra of water OH stretch (spanning 3000-3800 cm-1) from mineral surfaces without tuning the IR frequency, in 60 sec or less. The high signal-to-noise ratio of the broadband-IR SFG setup allowed the extension of SFG spectroscopy of interfacial hydroxyls at mineral/water surfaces to the low cross-section vibrational modes found in the high frequency range (4000-7000 cm-1). We performed, what we believe to be, the first surface-specific vibrational SFG spectroscopic measurements of the stretch+bend combination band, νcomb = νOH+δHOH of liquid water at silica surfaces near 5200 cm-1. SFG of the νcomb mode allows in-situ probing of surface-bound, e.g., SiOH, and H-OH hydroxyls separately. This provides access to the interfacial water bending mode δ (near 1600 cm-1), which has not been observed directly in SFG. O. Isaienko and E. Borguet Opt. Express 16(6), 3949-3954 March 2008. O. Isaienko and E. Borguet Opt. Express 20(1), 547-561 January 2012. O. Isaienko, S. Nihonyanagi, D. Sil and E. Borguet (in preparation).}.

  19. Energy Expenditure and Substrate Oxidation in Response to Side-Alternating Whole Body Vibration across Three Commonly-Used Vibration Frequencies.

    PubMed

    Fares, Elie-Jacques; Charrière, Nathalie; Montani, Jean-Pierre; Schutz, Yves; Dulloo, Abdul G; Miles-Chan, Jennifer L

    2016-01-01

    There is increasing recognition about the importance of enhancing energy expenditure (EE) for weight control through increases in low-intensity physical activities comparable with daily life (1.5-4 METS). Whole-body vibration (WBV) increases EE modestly and could present both a useful adjuvant for obesity management and tool for metabolic phenotyping. However, it is unclear whether a "dose-response" exists between commonly-used vibration frequencies (VF) and EE, nor if WBV influences respiratory quotient (RQ), and hence substrate oxidation. We aimed to investigate the EE-VF and RQ-VF relationships across three different frequencies (30, 40, and 50Hz). EE and RQ were measured in 8 healthy young adults by indirect calorimetry at rest, and subsequently during side-alternating WBV at one of 3 VFs (30, 40, and 50 Hz). Each frequency was assessed over 5 cycles of intermittent WBV (30s vibration/30s rest), separated by 5 min seated rest. During the WBV participants stood on the platform with knees flexed sufficiently to maintain comfort, prevent transmission of vibration to the upper body, and minimise voluntary physical exertion. Repeatability was assessed across 3 separate days in a subset of 4 individuals. In order to assess any sequence/habituation effect, an additional group of 6 men underwent 5 cycles of intermittent WBV (30s vibration/30s rest) at 40 Hz, separated by 5 min seated rest. Side-alternating WBV increased EE relative to standing, non-vibration levels (+36%, p<0.001). However, no differences in EE were observed across VFs. Similarly, no effect of VF on RQ was found, nor did WBV alter RQ relative to standing without vibration. No relationship could be demonstrated between EE and VF in the range of 30-50Hz, and substrate oxidation did not change in response to WBV. Furthermore, the thermogenic effect of intermittent WBV, whilst robust, was quantitatively small (<2 METS).

  20. Multiscale wireless sensor node for impedance-based SHM and low-frequency vibration data acquisition

    SciTech Connect

    Taylor, Stuart G; Farinholt, Kevin M; Park, Gyuhae; Farrar, Charles R; Todd, Michael D

    2009-01-01

    This paper presents recent developments in an extremely compact, wireless impedance sensor node (WID3, Wireless Impedance Device) at Los Alamos National Laboratory for use in impedance-based structural health monitoring (SHM), Sensor diagnostics and low-frequency vibrational data acquisition. The current generation WID3 is equipped with an Analog Devices AD5933 impedance chip that can resolve measurements up to 100 kHz, a frequency range ideal for many SHM applications. An integrated set of multiplexers allows the end user to monitor seven piezoelectric sensors from a single sensor node. The WID3 combines on-board processing using an Atmega1281 microcontroller, data storage using flash memory, wireless communications capabilities, and a series of internal and external triggering options into a single package to realize a truly comprehensive, self-contained wireless active-sensor node for SHM applications. Furthermore, we recently extended the capability of this device by implementing low-frequency analog to digital and digital and analog converters so that the same device can measure structural vibration data. The WID3 requires less than 70 mW of power to operate, and it can operate in various wireless network paradigms. The performance of this miniaturized and portable device is compared to our previous results and its broader capabilities are demonstrated.

  1. Relationship between low-frequency aircraft noise and annoyance due to rattle and vibration.

    PubMed

    Fidell, Sanford; Pearsons, Karl; Silvati, Laura; Sneddon, Matthew

    2002-04-01

    A near-replication of a study of the annoyance of rattle and vibration attributable to aircraft noise [Fidell et al., J. Acoust. Soc. Am. 106, 1408-1415 (1999)] was conducted in the vicinity of Minneapolis-St. Paul International Airport (MSP). The findings of the current study were similar to those reported earlier with respect to the types of objects cited as sources of rattle in homes, frequencies of notice of rattle, and the prevalence of annoyance due to aircraft noise-induced rattle. A reliably lower prevalence rate of annoyance (but not of complaints) with rattle and vibration was noted among respondents living in homes that had been treated to achieve a 5-dB improvement in A-weighted noise reduction than among respondents living in untreated homes. This difference is not due to any substantive increase in low-frequency noise reduction of acoustically treated homes, but may be associated with installation of nonrattling windows. Common interpretations of the prevalence of a consequential degree of annoyance attributable to low-frequency aircraft noise may be developed from the combined results of the present and prior studies.

  2. An Accurate ab initio Quartic Force Field and Vibrational Frequencies for CH4 and Isotopomers

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Martin, Jan M. L.; Taylor, Peter R.

    1995-01-01

    A very accurate ab initio quartic force field for CH4 and its isotopomers is presented. The quartic force field was determined with the singles and doubles coupled-cluster procedure that includes a quasiperturbative estimate of the effects of connected triple excitations, CCSD(T), using the correlation consistent polarized valence triple zeta, cc-pVTZ, basis set. Improved quadratic force constants were evaluated with the correlation consistent polarized valence quadruple zeta, cc-pVQZ, basis set. Fundamental vibrational frequencies are determined using second-order perturbation theory anharmonic analyses. All fundamentals of CH4 and isotopomers for which accurate experimental values exist and for which there is not a large Fermi resonance, are predicted to within +/- 6 cm(exp -1). It is thus concluded that our predictions for the harmonic frequencies and the anharmonic constants are the most accurate estimates available. It is also shown that using cubic and quartic force constants determined with the correlation consistent polarized double zeta, cc-pVDZ, basis set in conjunction with the cc-pVQZ quadratic force constants and equilibrium geometry leads to accurate predictions for the fundamental vibrational frequencies of methane, suggesting that this approach may be a viable alternative for larger molecules. Using CCSD(T), core correlation is found to reduce the CH4 r(e), by 0.0015 A. Our best estimate for r, is 1.0862 +/- 0.0005 A.

  3. An Accurate ab initio Quartic Force Field and Vibrational Frequencies for CH4 and Isotopomers

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Martin, Jan M. L.; Taylor, Peter R.

    1995-01-01

    A very accurate ab initio quartic force field for CH4 and its isotopomers is presented. The quartic force field was determined with the singles and doubles coupled-cluster procedure that includes a quasiperturbative estimate of the effects of connected triple excitations, CCSD(T), using the correlation consistent polarized valence triple zeta, cc-pVTZ, basis set. Improved quadratic force constants were evaluated with the correlation consistent polarized valence quadruple zeta, cc-pVQZ, basis set. Fundamental vibrational frequencies are determined using second-order perturbation theory anharmonic analyses. All fundamentals of CH4 and isotopomers for which accurate experimental values exist and for which there is not a large Fermi resonance, are predicted to within +/- 6 cm(exp -1). It is thus concluded that our predictions for the harmonic frequencies and the anharmonic constants are the most accurate estimates available. It is also shown that using cubic and quartic force constants determined with the correlation consistent polarized double zeta, cc-pVDZ, basis set in conjunction with the cc-pVQZ quadratic force constants and equilibrium geometry leads to accurate predictions for the fundamental vibrational frequencies of methane, suggesting that this approach may be a viable alternative for larger molecules. Using CCSD(T), core correlation is found to reduce the CH4 r(e), by 0.0015 A. Our best estimate for r, is 1.0862 +/- 0.0005 A.

  4. Pressure effect on vibrational frequency and dephasing of 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids.

    PubMed

    Pison, L; Costa Gomes, M F; Pádua, A A H; Andrault, D; Norman, S; Hardacre, C; Ribeiro, M C C

    2013-08-07

    Raman spectra in the range of the totally symmetric stretching mode of the [PF6](-) anion, νs(PF6), have been measured for 1-alkyl-3-methylimidazolium ionic liquids [CnC1im][PF6], for n = 4, 6, and 8, as a function of pressure at room temperature. The ionic liquids [C6C1im][PF6] and [C8C1im][PF6] remain in an amorphous phase up to 3.5 GPa, in contrast to [C4C1im][PF6], which crystallizes above ~0.5 GPa. Equations of state based either on a group contribution model or Carnahan-Starling-van der Waals model have been used to estimate the densities of the ionic liquids at high pressures. The shifts of the vibrational frequency of νs(PF6) with density observed in [C6C1im][PF6] and in [C8C1im][PF6] have been calculated by a hard-sphere model of a pseudo-diatomic solute under short-range repulsive interactions with the neighboring particles. The stochastic model of Kubo for vibrational dephasing has been used to obtain the amplitude of vibrational frequency fluctuation, <Δω(2)>, and the relaxation time of frequency fluctuation, τc, as a function of density by Raman band shape analysis of the νs(PF6) mode of [C6C1im][PF6] and [C8C1im][PF6].

  5. The effect of classical and quantum dynamics on vibrational frequency shifts of H2 in clathrate hydrates.

    PubMed

    Plattner, Nuria; Meuwly, Markus

    2014-01-14

    Vibrational frequency shifts of H2 in clathrate hydrates are important to understand the properties and elucidate details of the clathrate structure. Experimental spectra of H2 in clathrate hydrates have been measured for different clathrate compositions, temperatures, and pressures. In order to establish reliable relationships between the clathrate structure, dynamics, and observed frequencies, calculations of vibrational frequency shifts in different clathrate environments are required. In this study, a combination of classical molecular dynamics simulations, electronic structure calculations, and quantum dynamical simulation is used to calculate relative vibrational frequencies of H2 in clathrate hydrates. This approach allows us to assess dynamical effects and simulate the change of vibrational frequencies with temperature and pressure. The frequency distributions of the H2 vibrations in the different clathrate cage types agree favorably with experiment. Also, the simulations demonstrate that H2 in the 5(12) cage is more sensitive to the details of the environment and to quantum dynamical effects, in particular when the cage is doubly occupied. We show that for the 5(12) cage quantum effects lead to frequency increases and double occupation is unlikely. This is different for the 5(12)6(4) cages for which higher occupation numbers than one H2 per cage are likely.

  6. The effect of classical and quantum dynamics on vibrational frequency shifts of H{sub 2} in clathrate hydrates

    SciTech Connect

    Plattner, Nuria; Meuwly, Markus

    2014-01-14

    Vibrational frequency shifts of H{sub 2} in clathrate hydrates are important to understand the properties and elucidate details of the clathrate structure. Experimental spectra of H{sub 2} in clathrate hydrates have been measured for different clathrate compositions, temperatures, and pressures. In order to establish reliable relationships between the clathrate structure, dynamics, and observed frequencies, calculations of vibrational frequency shifts in different clathrate environments are required. In this study, a combination of classical molecular dynamics simulations, electronic structure calculations, and quantum dynamical simulation is used to calculate relative vibrational frequencies of H{sub 2} in clathrate hydrates. This approach allows us to assess dynamical effects and simulate the change of vibrational frequencies with temperature and pressure. The frequency distributions of the H{sub 2} vibrations in the different clathrate cage types agree favorably with experiment. Also, the simulations demonstrate that H{sub 2} in the 5{sup 12} cage is more sensitive to the details of the environment and to quantum dynamical effects, in particular when the cage is doubly occupied. We show that for the 5{sup 12} cage quantum effects lead to frequency increases and double occupation is unlikely. This is different for the 5{sup 12}6{sup 4} cages for which higher occupation numbers than one H{sub 2} per cage are likely.

  7. Computational procedures for evaluating the sensitivity derivatives of vibration frequencies and Eigenmodes of framed structures

    NASA Technical Reports Server (NTRS)

    Fetterman, Timothy L.; Noor, Ahmed K.

    1987-01-01

    Computational procedures are presented for evaluating the sensitivity derivatives of the vibration frequencies and eigenmodes of framed structures. Both a displacement and a mixed formulation are used. The two key elements of the computational procedure are: (a) Use of dynamic reduction techniques to substantially reduce the number of degrees of freedom; and (b) Application of iterative techniques to improve the accuracy of the derivatives of the eigenmodes. The two reduction techniques considered are the static condensation and a generalized dynamic reduction technique. Error norms are introduced to assess the accuracy of the eigenvalue and eigenvector derivatives obtained by the reduction techniques. The effectiveness of the methods presented is demonstrated by three numerical examples.

  8. Comparison of DFT with Traditional Methods for the Calculation of Vibrational Frequencies and Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

    1997-01-01

    The vibrational frequencies of MO2 are computed at many levels of theory, including HF, B3LYP, BP86, CASSCF, MP2, and CCSD(T). The computed results are compared with the available experimental results. Most of the methods fail for at least one state of the systems considered. The accuracy of the results and the origin of the observed failures are discussed. The B3LYP bond energies are compared with traditional methods for a variety of systems, ranging from FeCOn+ to SiCln and its positive ions. The cases where B3LYP differs from the traditional methods are discussed.

  9. Vibrational frequencies of anti-diabetic drug studied by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, S. Q.; Li, H.; Xie, L.; Chen, L.; Peng, Y.; Zhu, Y. M.; Li, H.; Dong, P.; Wang, J. T.

    2012-04-01

    By using terahertz time-domain spectroscopy, the absorption spectra of seven anti-diabetic pills have been investigated. For gliquidone, glipizide, gliclazide, and glimepiride, an obvious resonance peak is found at 1.37 THz. Furthermore, to overcome the limit of density functional theory that can analyze the normal mode frequencies of the ground state of organic material, we also present a method that relies on pharmacophore recognition, from which we can obtain the resonance peak at 1.37 THz can be attributed to the vibration of sulfonylurea group. The results indicate that the veracity of density functional theory can be increased by combining pharmacophore recognition.

  10. First-Principles Framework to Compute Sum-Frequency Generation Vibrational Spectra of Semiconductors and Insulators

    NASA Astrophysics Data System (ADS)

    Wan, Quan; Galli, Giulia

    2015-12-01

    We present a first-principles framework to compute sum-frequency generation (SFG) vibrational spectra of semiconductors and insulators. The method is based on density functional theory and the use of maximally localized Wannier functions to compute the response to electric fields, and it includes the effect of electric field gradients at surfaces. In addition, it includes quadrupole contributions to SFG spectra, thus enabling the verification of the dipole approximation, whose validity determines the surface specificity of SFG spectroscopy. We compute the SFG spectra of ice Ih basal surfaces and identify which spectra components are affected by bulk contributions. Our results are in good agreement with experiments at low temperature.

  11. Comparison of DFT with Traditional Methods for the Calculation of Vibrational Frequencies and Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

    1997-01-01

    The vibrational frequencies of MO2 are computed at many levels of theory, including HF, B3LYP, BP86, CASSCF, MP2, and CCSD(T). The computed results are compared with the available experimental results. Most of the methods fail for at least one state of the systems considered. The accuracy of the results and the origin of the observed failures are discussed. The B3LYP bond energies are compared with traditional methods for a variety of systems, ranging from FeCOn+ to SiCln and its positive ions. The cases where B3LYP differs from the traditional methods are discussed.

  12. Temporal response of biological cells to high-frequency optical jumping and vibrating tweezers

    NASA Astrophysics Data System (ADS)

    Yu, Lingyao; Sheng, Yunlong

    2014-09-01

    We analyzed the temporal responses of biological cells in the jumping and vibrating optical tweezers for tugging, wiggling and stretching the cells with the finite element method. Some new concepts were established, which might be investigated in the future experiments, such as the jumping of local stress and local strain, independently on the recovery time of the viscoelastic material and on the jumping frequency, the energy dissipation in the hysteresis cycles, the cytoplasm fluid field and its interaction with the cell membrane. The cell was modeled with full 3D structure and viscoelastic continuum materials.

  13. A piezoelectric pulse generator for low frequency non-harmonic vibration

    NASA Astrophysics Data System (ADS)

    Jiang, Hao; Yeatman, Eric M.

    2013-12-01

    This paper reports a new piezoelectric prototype for pulse generation by energy harvesting from low frequency non-harmonic vibration. The pulse generator presented here consists of two parts: the electromechanical part and the load circuit. A metal rolling rod is used as the proof mass, moving along the substrate to achieve both actuating of the piezoelectric cantilever by magnetic coupling and self-synchronous switching of the circuit. By using this new approach, the energy from the piezoelectric transduction mechanism is regulated simultaneously when it is extracted. This allows a series of tuneable pulses to be generated, which can be applied to self-powered RF wireless sensor network (WSN) nodes.

  14. First-principles framework to compute sum-frequency generation vibrational spectra of semiconductors and insulators.

    SciTech Connect

    Wan, Quan; Galli, Giulia

    2015-12-11

    We present a first-principles framework to compute sum-frequency generation (SFG) vibrational spectra of semiconductors and insulators. The method is based on density functional theory and the use of maximally localized Wannier functions to compute the response to electric fields, and it includes the effect of electric field gradients at surfaces. In addition, it includes quadrupole contributions to SFG spectra, thus enabling the verification of the dipole approximation, whose validity determines the surface specificity of SFG spectroscopy. We compute the SFG spectra of ice Ih basal surfaces and identify which spectra components are affected by bulk contributions. Our results are in good agreement with experiments at low temperature.

  15. Li2MoO4 crystal growth from solution activated by low-frequency vibrations

    NASA Astrophysics Data System (ADS)

    Barinova, Olga; Sadovskiy, Andrey; Ermochenkov, Ivan; Kirsanova, Svetlana; Sukhanova, Ekaterina; Kostikov, Vladimir; Belov, Stanislav; Mozhevitina, Elena; Khomyakov, Andrew; Kuchuk, Zhanna; Zharikov, Eugeny; Avetissov, Igor

    2017-01-01

    The possibility of Li2MoO4 crystal growth from aqueous solutions activated by axial vibrational control (AVC) technique was investigated. It was found out that a low-frequency mechanical activation of the solution led to an increase of Li2MoO4 equilibrium solubility in aqueous solution for 11 rel% in the 25-29 °C temperature range. The changes in solution structure were analyzed in situ by Raman study of the solution. The AVC activation of solution resulted in a re-faceting of growing crystals, a smoothing of a face surface morphology and reduction of water content in the crystal.

  16. Proteins at interfaces probed by chiral vibrational sum frequency generation spectroscopy.

    PubMed

    Yan, Elsa C Y; Wang, Zhuguang; Fu, Li

    2015-02-19

    Characterizations of protein structures at interfaces are important in solving an array of fundamental and engineering problems, including understanding transmembrane signal transduction and molecular transport processes and development of biomaterials to meet the needs of biomedical and energy research. However, in situ and real-time characterization of protein secondary structures is challenging because it requires physical methods that are selective to both interface and secondary structures. Here, we summarize recent experimental developments in our laboratory of chiral vibrational sum frequency generation spectroscopy (SFG) for analyzing protein structures at interfaces. We showed that chiral SFG provides vibrational optical signatures of the peptide N-H stretch and amide I modes that can distinguish various protein secondary structures. Using these signatures, we further applied chiral SFG to probe orientations and folding kinetics of proteins at interfaces. Our results show that chiral SFG is a background-free, label-free, in situ, and real-time vibrational method for studying proteins at interfaces. This recent progress demonstrates the potential of chiral SFG in solving problems related to proteins and other chiral biopolymers at interfaces.

  17. Ultra-low frequency vertical vibration isolator based on LaCoste spring linkage

    NASA Astrophysics Data System (ADS)

    Li, G.; Hu, H.; Wu, K.; Wang, G.; Wang, L. J.

    2014-10-01

    For the applications in precision measurement such as absolute gravimeter, we have designed and built an ultra-low frequency vertical vibration isolator based on LaCoste spring linkage. In the system, an arm with test mass is suspended by a mechanical extension spring, and one end of the arm is connected to the frame with flexible pivots. The displacement of the arm is detected by an optical reflection method. With the displacement signal, a feedback control force is exerted on the arm to keep it at the balance position. This method can also correct the systematic drift caused by temperature change. In order to study the vibration isolation performance of the system, we analyze the dynamic characteristics of the spring linkage in the general case, and present key methods to adjust the natural oscillating period of the system. With careful adjustment, the system can achieve a steady oscillation with a natural period up to 32 s. This isolator has been tested based on the T-1 absolute gravimeter. A statistical uncertainty of 2 μGal has been achieved within a typical 12 h measurement. The experimental results verify that the isolator has significant vibration isolation performance, and it is very suitable for applications in high precision absolute gravity measurement.

  18. Ultra-low frequency vertical vibration isolator based on LaCoste spring linkage.

    PubMed

    Li, G; Hu, H; Wu, K; Wang, G; Wang, L J

    2014-10-01

    For the applications in precision measurement such as absolute gravimeter, we have designed and built an ultra-low frequency vertical vibration isolator based on LaCoste spring linkage. In the system, an arm with test mass is suspended by a mechanical extension spring, and one end of the arm is connected to the frame with flexible pivots. The displacement of the arm is detected by an optical reflection method. With the displacement signal, a feedback control force is exerted on the arm to keep it at the balance position. This method can also correct the systematic drift caused by temperature change. In order to study the vibration isolation performance of the system, we analyze the dynamic characteristics of the spring linkage in the general case, and present key methods to adjust the natural oscillating period of the system. With careful adjustment, the system can achieve a steady oscillation with a natural period up to 32 s. This isolator has been tested based on the T-1 absolute gravimeter. A statistical uncertainty of 2 μGal has been achieved within a typical 12 h measurement. The experimental results verify that the isolator has significant vibration isolation performance, and it is very suitable for applications in high precision absolute gravity measurement.

  19. Non-Seismology Seismology: Using QuakeCatchers to Analyze the Frequency of Bridge Vibrations

    NASA Astrophysics Data System (ADS)

    Courtier, A. M.; Constantin, C.; Wilson, C. F.

    2013-12-01

    We conducted an experiment to test the feasibility of measuring seismic waves generated by traffic near James Madison University. We used QuakeCatcher seismometers (originally designed for passive seismic measurement) to measure vibrations associated with traffic on a wooden bridge as well as a nearby concrete bridge. This experiment was a signal processing exercise for a student research project and did not draw any conclusions regarding bridge safety or security. The experiment consisted of two temporary measurement stations comprised of a laptop computer and a QuakeCatcher - a small seismometer that plugs directly into the laptop via a USB cable. The QuakeCatcher was taped to the ground at the edge of the bridge to achieve good coupling, and vibrational events were triggered repeatedly with a control vehicle to accumulate a consistent dataset of the bridge response. For the wooden bridge, the resulting 'seismograms' were converted to Seismic Analysis Code (SAC) format and analyzed in MATLAB. The concrete bridge did not generate vibrations significant enough to trigger the recording mechanism on the QuakeCatchers. We will present an overview of the experimental design and frequency content of the traffic patterns, as well as a discussion of the instructional benefits of using the QuakeCatcher sensors in this non-traditional setting.

  20. Postural responses to various frequencies of vibration of the triceps surae and forefoot sole during quiet standing.

    PubMed

    Naka, Masami; Fujiwara, Katsuo; Kiyota, Naoe

    2015-01-01

    The purpose of this study was to determine the role of somatosensory input to the sensory reference system in quiet standing. We applied vibration (0.5 mm amplitude, 1-60 Hz) to the triceps surae and the forefoot sole to stimulate the muscle spindles and the mechanoreceptors, respectively, and evaluated postural responses. Thirteen young healthy adults who showed backward-lean and forward-lean responses to vibration at high and low frequencies, respectively, participated in the full experiment. The lowest vibration frequencies inducing backward-lean responses (B-LF) were 15-55 Hz for the triceps surae and 16-60 Hz for the forefoot sole. The highest frequencies inducing forward-lean responses (F-HF) were 3-18 Hz for the triceps surae and 1-20 Hz for the forefoot sole. When vibration was simultaneously applied to the triceps surae and forefoot sole at F-HF, no response was induced in 70% of trials. A forward-lean response was induced in the remaining 30% of trials. Simultaneous vibration of the triceps surae and forefoot sole at B-LF induced backward-lean responses in all trials. All postural responses occurred 0.5-4.3 s after vibration onset. Postural responses to high-frequency vibration conceivably occur as a compensatory movement to the illusionary perception that standing position is deviating forward from quiet standing, which must be a reference position. Postural responses to low-frequency vibration possibly occur to equalize the positional information that is received from the triceps surae and the forefoot sole. Both postural responses are likely to involve the sensory reference system, which is located in the supraspinal nervous system.

  1. Low resonance frequency vibration affects strength of paretic and non-paretic leg differently in patients with stroke.

    PubMed

    Tihanyi, J; Di Giminiani, R; Tihanyi, T; Gyulai, G; Trzaskoma, L; Horváth, M

    2010-06-01

    The objective of the study was to investigate the chronic effect of low frequency whole body vibration (WBV) on isometric and eccentric strength of knee extensors with different force exertion capacity. It was hypothesized that (1) four-week WBV intervention with the low frequency domain would enhance muscle strength and (2) the improvement would be more pronounced in the weaker muscle. To test our hypothesis twenty patients with acute stroke were recruited. Ten patients were randomly assigned to vibration and the remaining ten patients served for control.The patients in the vibration group received WBV with 20 Hz frequency three times per week standing on a vibration platform in half squat position meanwhile flexing and extending the joints and placing the weight from one leg to the other. Knee extensor strength was determined under isometric and eccentric contraction before and after WBV intervention. Myoelectrical activity (EMG) of the vastus lateralis muscle was also measured.Significant improvement was revealed in the vibration group only. The maximum isometric torque and EMG activity increased significantly for both paretic and non-paretic leg, but the improvement was threefold greater in the vibration group. No significant alteration was found in rate of torque development. Maximum eccentric torque and EMG increased significantly for the paretic leg only. Mechanical work enhanced significantly in the paretic side only.The results of our study indicate that the selection of the effective vibration frequency depends upon the physical condition of neuromuscular system. Low vibration frequency intervention can increase the strength in weak muscles due to neuromuscular impairment and restricted physical activity.

  2. On Enhancement of Fluid Flow in Porous Media by Application of Low-Frequency Sonic Vibrations

    NASA Astrophysics Data System (ADS)

    Iassonov, P. P.; Beresnev, I. A.

    2001-05-01

    Numerous observations and laboratory experiments show that application of vibrations at different frequencies may significantly enhance transport of non-aqueous phase liquids (NAPLs) in porous media. However, the physical mechanisms governing the coupling between stress (seismic) waves and multiphase fluid flow are poorly understood. There are many mechanisms thought to be responsible for the observed fluid-sound interaction. Among these are the reduction in the effect of capillary forces, destruction of films adsorbed on pore boundaries, fluid resonance, coalescence of NAPL ganglia, and peristaltic transport. The high-frequency sonic waves as an aid in the stimulation of NAPL flow are extremely limited in distance range due to high attenuation. Only low-frequency waves can reach regions of the reservoirs or aquifers that are far from boreholes. Our analyses suggest that, in the low-frequency range, non-linear rheology of the fluid and capillary forces may be the predominant mechanisms of stimulation. Our theoretical model thus incorporates these mechanisms for a case of a flow through a circular tube. It was shown in earlier studies that crude oil demonstrates yield-stress behavior; the yield-stress rheology was thus assumed in our model. The exact rheological parameters of higher-grade oils in the near-zero stress range are unknown; however, these parameters can be indirectly estimated from field data. The model shows that low-frequency waves of relatively low intensity can significantly enhance the flow rate of a yield-stress fluid under small external-pressure gradients. We estimated the parameters of the sonic field for a possible field implementation and the range of its applicability. As opposed to rheological properties, the capillary effects on the flow are well known, but only the resonance effects have been previously studied in connection with the effect of vibrations. We have demonstrated that, due to the effect of "pinning" of NAPL menisci on the

  3. Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure

    SciTech Connect

    Li, Pengwei Wang, Yanfen; Luo, Cuixian; Li, Gang; Hu, Jie; Zhang, Wendong; Liu, Ying; Liu, Wei

    2015-04-15

    As an alternative to traditional cantilever beam structures and their evolutions, a flexible beam based, interdigital structure, vibration energy harvester has been presented and investigated. The proposed interdigital-shaped oscillator consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. In order to achieve low frequency and wide-bandwidth harvesting, Young’s modulus of materials, frame size and the amount of the cantilevers have been studied systematically. The measured frequency responses of the designed device (PDMS frame, quintuple piezoelectric cantilever beams) show a 460% increase in bandwidth below 80Hz. When excited at an acceleration of 1.0 g, the energy harvester achieves to a maximum open-circuit voltage of 65V, and the maximum output power 4.5 mW.

  4. Normal vibrational modes of phospholipid bilayers observed by low-frequency Raman scattering

    NASA Astrophysics Data System (ADS)

    Surovtsev, N. V.; Dmitriev, A. A.; Dzuba, S. A.

    2017-03-01

    Low-frequency Raman spectra of multilamellar vesicles made either of 1-palmitoyl-2-oleoyl-s n -glycero-3-phosphocholine (POPC) or 1,2-dipalmitoyl-s n -glycero-3-phosphocholine (DPPC) have been studied in a wide temperature range. Below 0 ∘C two peaks are found at frequencies around 8-9 and 14 -17 c m -1 and attributed to the normal vibrational modes of the phospholipid bilayer, which are determined by the bilayer thickness and stiffness (elastic modulus). The spectral positions of the peaks depend on the temperature and the bilayer composition. It is suggested that the ratio of the intensities of the first and second peaks can serve as a measure of the interleaflet elastic coupling. The addition of cholesterol to the phospholipid bilayer leads to peak shift and broadening, which may be assigned to the composition heterogeneities commonly attributed to the lipid raft formation.

  5. Vibration energy harvester with low resonant frequency based on flexible coil and liquid spring

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Zhang, Q.; Zhao, L.; Tang, Y.; Shkel, A.; Kim, E. S.

    2016-11-01

    This paper reports an electromagnetic vibration-energy harvester with low resonant frequency based on liquid spring composed of ferrofluid. Cylinder magnet array formed by four disc NdFeB magnets is suspended by ferrofluid in a laser-machined acrylic tube which is wrapped by flexible planar coil fabricated with microfabrication process. The magnet array and coil are aligned automatically by the ferrofluid. Restoring force when the magnet array is deviated from the balance position is proportional to the deviated distance, which makes the ferrofluid work as a liquid spring obeying Hook's law. Experimental results show that the electromagnetic energy harvester occupying 1.8 cc and weighing 5 g has a resonant frequency of 16 Hz and generates an induced electromotive force of Vrms = 2.58 mV (delivering 79 nW power into matched load of 21 Ω) from 3 g acceleration at 16 Hz.

  6. Tracking Intramolecular Vibrational Redistribution in Polyatomic Small-Molecule Liquids by Ultrafast Time-Frequency-Resolved CARS.

    PubMed

    Liu, Xiaosong; Zhang, Wei; Song, Yunfei; Yu, Guoyang; Zheng, Zhaoyang; Zeng, Yangyang; Lv, Zhe; Song, Huajie; Yang, Yanqiang

    2017-07-06

    Selective excitation of C-H stretching vibrational modes, detection of intramolecular vibrational energy redistribution (IVR), and vibrational modes coupling in the electronic ground state of benzene are performed by using femtosecond time- and frequency-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy. Both of the parent modes in the Raman-active bands are coherently excited by an ultrafast stimulated Raman pump, giving initial excitations of 3056 cm(-1) (A1g) and 3074 cm(-1) (E2g) and subsequent IVR from the parent modes to daughter modes of 1181 and 992 cm(-1), and the coherent vibrational coupling of the relevant modes is tracked. The directionality and selectivity of IVR and coherent coupling among all of the relevant vibrational modes are discussed in the view of molecular symmetry.

  7. The dispersion correction and weak-hydrogen-bond network in low-frequency vibration of solid-state salicylic acid

    NASA Astrophysics Data System (ADS)

    Takahashi, Masae; Ishikawa, Yoichi; Ito, Hiromasa

    2012-04-01

    We perform the dispersion-corrected first-principles calculations of vibrational absorption and the far-infrared (terahertz) spectroscopic experiments at different temperature to examine the effect of weak-hydrogen-bond network on the low-frequency vibrations of solid-state salicylic acid. By dispersion correction, calculated frequencies improve especially in the intermonomer torsion and interdimer translational modes which are closely related to the weak hydrogen bonds. The calculated frequencies and their relative intensities reproduce the observed spectrum in the accuracy of 10 cm-1 or less. Weak-hydrogen-bond network causes a large frequency shift of out-of-plane intermonomer modes and enhances interdimer translational modes accompanied by the O⋯H stretching vibrations.

  8. Comparison of frequency-domain and time-domain rotorcraft vibration control methods

    NASA Technical Reports Server (NTRS)

    Gupta, N. K.

    1984-01-01

    Active control of rotor-induced vibration in rotorcraft has received significant attention recently. Two classes of techniques have been proposed. The more developed approach works with harmonic analysis of measured time histories and is called the frequency-domain approach. The more recent approach computes the control input directly using the measured time history data and is called the time-domain approach. The report summarizes the results of a theoretical investigation to compare the two approaches. Five specific areas were addressed: (1) techniques to derive models needed for control design (system identification methods), (2) robustness with respect to errors, (3) transient response, (4) susceptibility to noise, and (5) implementation difficulties. The system identification methods are more difficult for the time-domain models. The time-domain approach is more robust (e.g., has higher gain and phase margins) than the frequency-domain approach. It might thus be possible to avoid doing real-time system identification in the time-domain approach by storing models at a number of flight conditions. The most significant error source is the variation in open-loop vibrations caused by pilot inputs, maneuvers or gusts. The implementation requirements are similar except that the time-domain approach can be much simpler to implement if real-time system identification were not necessary.

  9. Reorganization of intramolecular high frequency vibrational modes and dynamic solvent effect in electron transfer reactions.

    PubMed

    Yudanov, Vladislav V; Mikhailova, Valentina A; Ivanov, Anatoly I

    2012-04-26

    The possibility of the multichannel stochastic model to adequately describe all principal regularities observed in thermal electron transfer kinetics has been demonstrated. The most important are as follows: (i) the model predicts the solvent controlled regime in the Marcus normal region and its almost full suppression in the Marcus inverted region as well as a continuous transition between them in the vicinity of the activationless region; (ii) the suppression of dynamic solvent effect (DSE) is principally caused by the reorganization of high frequency vibrational modes; (iii) an additional factor of the DSE suppression stems from fast solvent relaxation component; (iv) in the inverted region, the multichannel stochastic model predicts the apparent activation energy to be much less than that calculated with Marcus equation. The exploration of the multichannel stochastic model has allowed one to conclude that the reorganization of high frequency vibrational modes can (i) raise the maximum rate constant above the solvent controlled limit by 2 and more orders of magnitude, (ii) shift the rate constant maximum to larger values of the free energy gap, and (iii) approach the electron transfer kinetics to the nonadiabatic regime.

  10. Low-frequency vibration modulation of guided waves to image nonlinear scatterers for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Jiao, J. P.; Drinkwater, B. W.; Neild, S. A.; Wilcox, P. D.

    2009-06-01

    Guided wave structural health monitoring offers the prospect of continuous interrogation of large plate-like structures with a sparse network of permanently attached sensors. Currently, the most common approach is to monitor changes in the received signals by subtraction from a reference signal obtained when the structure was known to be defect-free. In this paper a comparison is made between this defect-free subtraction approach and a technique in which low-frequency vibration modulation of guided wave signals is used to detect nonlinear scatterers. The modulation technique potentially overcomes the need for the defect-free reference measurement as the subtraction is now made between different parts of an externally applied low-frequency vibration. Linear defects were simulated by masses bonded onto a plate and nonlinear scatterers were simulated by loading a similar mass against the plate. The experimental results show that the defect-free subtraction technique performs well in detecting the bonded mass whereas the modulation technique is able to discriminate between the bonded and loaded masses. Furthermore, because the modulation technique does not require a defect-free reference, it is shown to be relatively independent of temperature effects, a significant problem for reference based subtraction techniques.

  11. A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency

    NASA Astrophysics Data System (ADS)

    Guo, Yan-bo; Liu, Zi-zhong; Liu, Hong-xia; Zhang, Feng-ying; Yin, Jun-qing

    2016-07-01

    A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L = C, Si, Ge, n = 3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.0). There are high positive correlations between the theoretical calculated the NICS values and the value of the RSVRSF (A1g/A1‧) of the LnHn (L = C, Si, Ge, n = 3, 5-8). The bigger the aromatic degree, the bigger the RSVRSF is. The value of the RSVRSF is a new probe of aromaticity. Expectedly, it is predicted that the experimental determination of the aromatic degree can be achieved by the determination of the ring stretching vibration (A1g/A1‧) Raman spectrum frequencies for the aromatic target molecules.

  12. On the spectroscopic constants, first electronic state, vibrational frequencies, and isomerization of hydroxymethylene (HCOH+)

    NASA Astrophysics Data System (ADS)

    Theis, Riley A.; Fortenberry, Ryan C.

    2017-09-01

    The hydroxymethylene cation (HCOH+) is believed to be chemically independent of the more stable formaldehyde cation isomer in interstellar chemistry and may likely be a precursor to methanol in chemical reaction networks. Previous work is corroborated here showing that the trans conformer of HCOH+ is 3.48 kcal/mol lower than the cis on the potential energy surface. The small energy difference between the conformers and the much larger dipole moment of cis-HCOH+ (2.73 D) make this conformer more likely to be observed than trans-HCOH+ via telescopic rotational spectroscopy. A strong adiabatic shift is also predicted in the first electronic excitation into the 1 2A‧‧/2 2A state out of either conformer into a C1 structure reducing the excitation wavelength from the near-ultraviolet all the way into the near-infrared. The full set of fundamental vibrational frequencies are also computed here at high-level. The 3306.0 cm-1 and 3225.3 cm-1 hydroxide stretches, respective of bare trans- and cis-HCOH+ , are in agreement with previous theory but are significantly higher than the frequencies determined from previous experiment utilizing argon tagging techniques. This shift is likely because the proton-bound complex created with the argon tag reduces the experimental frequencies. Lower-level computations including the argon tag bring the hydroxide stretches much closer to the experimental frequencies indicating that the predicted frequencies for bare HCOH+ are likely well-described.

  13. A vibrating reed apparatus to measure the natural frequency of multilayered thin films

    NASA Astrophysics Data System (ADS)

    Gamboa, F.; López, A.; Avilés, F.; Corona, J. E.; Oliva, A. I.

    2016-04-01

    An apparatus for measuring the natural frequency of sub-micrometric layered films in cantilever beam configuration is presented. The instrument comprises a specially designed test rig with a sample holder, an electronic excitation source, a vibration sensor and an automated software for the excitation and data recollection. The beam is excited by means of an air pulse and the oscillation amplitude of its free end is measured through a laser diode-photosensor arrangement. The instrument provides a very low uncertainty (˜1 mHz, for frequencies of the order of tens Hz) for repeated sequential tests and the major source of uncertainty (˜0.2 Hz, corresponding to a coefficient of variation of 0.18%) arises from the difficulty of placing the sample in an exactly identical location upon clamping. This high sensitivity renders the capability of measuring very small frequency shifts upon deposition of sub-micrometric films over thicker substrates. In order to assess the reliability of the apparatus, cantilever beams of 125 μm thick neat Kapton (substrate) and thin layered films of Au/Kapton and Al/Au/Kapton of 200-250 nm film thickness were fabricated and their natural frequency and damping factor were measured. Calculations of the natural frequency of such beams by finite element analysis further support the accuracy of the experimental measurements.

  14. Energy harvesting of radio frequency and vibration energy to enable wireless sensor monitoring of civil infrastructure

    NASA Astrophysics Data System (ADS)

    Galchev, Tzeno; McCullagh, James; Peterson, Rebecca L.; Najafi, Khalil; Mortazawi, Amir

    2011-04-01

    To power distributed wireless sensor networks on bridges, traditional power cables or battery replacement are excessively expensive or infeasible. This project develops two power harvesting technologies. First, a novel parametric frequency-increased generator (PFIG) is developed. The fabricated PFIG harvests the non-periodic and unprecedentedly low frequency (DC to 30 Hz) and low acceleration (0.55-9.8 m/s2) mechanical energy available on bridges with an average power > 2 μW. Prototype power conversion and storage electronics were designed and the harvester system was used to charge a capacitor from arbitrary bridge-like vibrations. Second, an RF scavenger operating at medium and shortwave frequencies has been designed and tested. Power scavenging at MHz frequencies allows for lower antenna directivities, reducing sensitivity to antenna positioning. Furthermore, ambient RF signals at these frequencies have higher power levels away from cities and residential areas compared to the UHF and SHF bands utilized for cellular communication systems. An RF power scavenger operating at 1 MHz along with power management and storage circuitry has been demonstrated. It powers a LED at a distance of 10 km from AM radio stations.

  15. Spatial and Time Variability of Ambient Vibration H/V Frequency Peak

    NASA Astrophysics Data System (ADS)

    Benkaci, Nassima; Oubaiche, El-hadi; Chatelain, Jean-luc; Bensalem, Rabah; Abbes, Khadidja

    2016-04-01

    The ambient vibration H/V technique is widely used nowadays in microzonation studies, because of its easy field handling and its low cost, compared to other geophysical methods. However, in presence of complex geology or lateral heterogeneity evidenced by more than one peak frequency in the H/V curve, it is difficult to interpret the results, especially when soil information is lacking. In this work, we focus on the construction site of the Baraki 40000=place stadium, located in the north-east side of the Mitidja basin (Algeria), to identify the seismic wave amplification zones. H/V curve analysis leads to the observation of spatial and time variability of the H/V frequency peaks. The spatial variability allows dividing the studied area into three main zones: (1) one with a predominant frequency around 1,5 Hz showing an important amplification level, (2) the second exhibits two peaks at 1,5 Hz and in the 4 Hz - 10 Hz range, and (3) the third zone is characterized by a plateau between 2 Hz and 3 Hz. These H/V curve categories reveal a consequent lateral heterogeneity dividing the stadium site roughly in the middle. Furthermore, a continuous ambient vibration recording during several weeks allows showing that the first peak at 1,5Hz in the second zone, completely disappears between 2 am and 4 am, and reaching its maximum amplitude around 12 am. Consequently, the anthropogenic noise source generating these important variations could be the Algiers Rocade Sud highway, located in the maximum amplification azimuth direction of the H/V curves. This work points out that the H/V method is an important tool to perform nano-zonation studies prior to geotechnical and geophysical investigations, and that, in some cases, the H/V technique fails to reveal the resonance frequency in the absence of strong anthropogenic source.

  16. Effect of higher frequency components and duration of vibration on bone tissue alterations in the rat-tail model

    PubMed Central

    PEELUKHANA, Srikara V.; GOENKA, Shilpi; KIM, Brian; KIM, Jay; BHATTACHARYA, Amit; STRINGER, Keith F.; BANERJEE, Rupak K.

    2015-01-01

    To formulate more accurate guidelines for musculoskeletal disorders (MSD) linked to Hand-Arm Vibration Syndrome (HAVS), delineation of the response of bone tissue under different frequencies and duration of vibration needs elucidation. Rat-tails were vibrated at 125 Hz (9 rats) and 250 Hz (9 rats), at 49 m/s2, for 1D (6 rats), 5D (6 rats) and 20D (6 rats); D=days (4 h/d). Rats in the control group (6 rats for the vibration groups; 2 each for 1D, 5D, and 20D) were left in their cages, without being subjected to any vibration. Structural and biochemical damages were quantified using empty lacunae count and nitrotyrosine signal-intensity, respectively. One-way repeated-measure mixed-model ANOVA at p<0.05 level of significance was used for analysis. In the cortical bone, structural damage quantified through empty lacunae count was significant (p<0.05) at 250 Hz (10.82 ± 0.66) in comparison to the control group (7.41 ± 0.76). The biochemical damage was significant (p<0.05) at both the 125 Hz and 250 Hz vibration frequencies. The structural damage was significant (p<0.05) at 5D for cortical bone while the trabecular bone showed significant (p<0.05) damage at 20D time point. Further, the biochemical damage increased with increase in the duration of vibration with a significant (p<0.05) damage observed at 20D time point and a near significant change (p=0.08) observed at 5D time point. Structural and biochemical changes in bone tissue are dependent upon higher vibration frequencies of 125 Hz, 250 Hz and the duration of vibration (5D, 20D). PMID:25843564

  17. Effect of higher frequency components and duration of vibration on bone tissue alterations in the rat-tail model.

    PubMed

    Peelukhana, Srikara V; Goenka, Shilpi; Kim, Brian; Kim, Jay; Bhattacharya, Amit; Stringer, Keith F; Banerjee, Rupak K

    2015-01-01

    To formulate more accurate guidelines for musculoskeletal disorders (MSD) linked to Hand-Arm Vibration Syndrome (HAVS), delineation of the response of bone tissue under different frequencies and duration of vibration needs elucidation. Rat-tails were vibrated at 125 Hz (9 rats) and 250 Hz (9 rats), at 49 m/s(2), for 1D (6 rats), 5D (6 rats) and 20D (6 rats); D=days (4 h/d). Rats in the control group (6 rats for the vibration groups; 2 each for 1D, 5D, and 20D) were left in their cages, without being subjected to any vibration. Structural and biochemical damages were quantified using empty lacunae count and nitrotyrosine signal-intensity, respectively. One-way repeated-measure mixed-model ANOVA at p<0.05 level of significance was used for analysis. In the cortical bone, structural damage quantified through empty lacunae count was significant (p<0.05) at 250 Hz (10.82 ± 0.66) in comparison to the control group (7.41 ± 0.76). The biochemical damage was significant (p<0.05) at both the 125 Hz and 250 Hz vibration frequencies. The structural damage was significant (p<0.05) at 5D for cortical bone while the trabecular bone showed significant (p<0.05) damage at 20D time point. Further, the biochemical damage increased with increase in the duration of vibration with a significant (p<0.05) damage observed at 20D time point and a near significant change (p=0.08) observed at 5D time point. Structural and biochemical changes in bone tissue are dependent upon higher vibration frequencies of 125 Hz, 250 Hz and the duration of vibration (5D, 20D).

  18. Vibrations in MagAO: frequency-based analysis of on-sky data, resonance sources identification, and future challenges in vibrations mitigation

    NASA Astrophysics Data System (ADS)

    Zúñiga, Sebastián.; Garcés, Javier; Close, Laird M.; Males, Jared R.; Morzinski, Katie M.; Escárate, Pedro; Castro, Mario; Marchioni, José; Zagals, Diego

    2016-07-01

    Frequency-based analysis and comparisons of tip-tilt on-sky data registered with 6.5 Magellan Telescope Adaptive Optics (MagAO) system on April and Oct 2014 was performed. Twelve tests are conducted under different operation conditions in order to observe the influence of system instrumentation (such as fans, pumps and louvers). Vibration peaks can be detected, power spectral densities (PSDs) are presented to reveal their presence. Instrumentation-induced resonances, close-loop gain and future challenges in vibrations mitigation techniques are discussed.

  19. [Dynamics of vegetative indicators induced by low-frequency magnetotherapy and EHF-puncture in hypertensive workers exposed to vibration].

    PubMed

    Drobyshev, V A; Efremov, A V; Loseva, M I; Sukharevskaia, T M; Michurin, A I

    2002-01-01

    Low-frequency magnetic fields and EHF-therapy have been used in correction of autonomic homeostasis in workers exposed to vibration for different periods of time. The workers suffered from early arterial hypertension. Vegetative status and central hemodynamics improved best in workers exposed to vibration for less than 5 years. If the exposure was 6-15 years, a positive trend occurred in the tension of regulatory mechanisms. Workers with long exposure to vibration suffering from vagotonia showed an inadequate response of the autonomic parameters to treatment. This necessitates enhancement of therapeutic measures with medicines.

  20. Optical multi-frequency swept sensing for wide-field vibration measurement of interior surfaces in biological tissue

    NASA Astrophysics Data System (ADS)

    Choi, S.; Nin, F.; Hibino, H.; Suzuki, T.

    2015-12-01

    Multifrequency sensing technique adopting the wide field heterodyne detection technique is demonstrated for interior surface vibration measurements in thick biological tissue. These arrangements allow obtaining not only 3D tomographic images but also various vibration parameters such as spatial amplitude, phase, and frequency, with high temporal and transverse resolutions over a wide field. The axial resolution and the accuracy of vibration amplitude measurement were estimated to be 2.5 μm and 3 nm, respectively. This wide-field tomographic sensing method can be applied for measuring microdynamics of a variety of biological samples, thus contributing to the progress in life sciences research.

  1. Focusing vibrating targets in frequency-modulation continuous-wave-synthetic aperture radar with Doppler keystone transform

    NASA Astrophysics Data System (ADS)

    Hu, Yuxin; Zhang, Yuan; Sun, Jinping; Lei, Peng

    2016-04-01

    Vibrating targets generally induce sinusoidal micro-Doppler modulation in high resolution synthetic aperture radar (SAR). They could cause defocused and ghost results by conventional imaging algorithms. This paper proposes a method on vibrating target imaging in frequency-modulation continuous-wave (FMCW) SAR systems. The continuous motion of sensor platform during pulse time is considered in the signal model. Based on Bessel series expansion of the signal in the azimuth direction, the influence of platform motion on the azimuth frequency is eliminated after dechirp and deskew. In addition, the range walk is compensated in the two-dimensional frequency domain by Doppler keystone transform. Next, using range cell migration correction, the azimuth quadratic phase compensation and the range curvature correction are made in range-Doppler domain for the focus of paired echoes. The residual video phase of paired echoes is eliminated, and vibration parameters are estimated to compensate in the sinusoidal modulation phase. Then the deghosted image of vibrating targets can be obtained. The proposed method is applicable to multiple targets with various vibrating states due to no need of a priori knowledge of targets. Finally, simulations are carried out to validate the effectiveness of the method in FMCW-SAR imaging of vibrating targets.

  2. Distinct frequency dependent effects of whole-body vibration on non-fractured bone and fracture healing in mice.

    PubMed

    Wehrle, Esther; Wehner, Tim; Heilmann, Aline; Bindl, Ronny; Claes, Lutz; Jakob, Franz; Amling, Michael; Ignatius, Anita

    2014-08-01

    Low-magnitude high-frequency vibration (LMHFV) provokes anabolic effects in non-fractured bone; however, in fracture healing, inconsistent results were reported and optimum vibration conditions remain unidentified. Here, we investigated frequency dependent effects of LMHFV on fracture healing. Twelve-week-old, female C57BL/6 mice received a femur osteotomy stabilized using an external fixator. The mice received whole-body vibrations (20 min/day) with 0.3g peak-to-peak acceleration and a frequency of either 35 or 45 Hz. After 10 and 21 days, the osteotomized femurs and intact bones (contra-lateral femurs, lumbar spine) were evaluated using bending-testing, µ-computed tomography, and histomorphometry. In non-fractured trabecular bone, vibration with 35 Hz significantly increased the relative amount of bone (+28%) and the trabecular number (+29%), whereas cortical bone was not influenced. LMHFV with 45 Hz failed to provoke anabolic effects in trabecular or cortical bone. Fracture healing was not significantly influenced by whole-body vibration with 35 Hz, whereas 45 Hz significantly reduced bone formation (-64%) and flexural rigidity (-34%) of the callus. Although the exact mechanisms remain open, our results suggest that small vibration setting changes could considerably influence LMHFV effects on bone formation in remodeling and repair, and even disrupt fracture healing, implicating caution when treating patients with impaired fracture healing.

  3. Definitions of non-stationary vibration power for time-frequency analysis and computational algorithms based upon harmonic wavelet transform

    NASA Astrophysics Data System (ADS)

    Heo, YongHwa; Kim, Kwang-joon

    2015-02-01

    While the vibration power for a set of harmonic force and velocity signals is well defined and known, it is not as popular yet for a set of stationary random force and velocity processes, although it can be found in some literatures. In this paper, the definition of the vibration power for a set of non-stationary random force and velocity signals will be derived for the purpose of a time-frequency analysis based on the definitions of the vibration power for the harmonic and stationary random signals. The non-stationary vibration power, defined as the short-time average of the product of the force and velocity over a given frequency range of interest, can be calculated by three methods: the Wigner-Ville distribution, the short-time Fourier transform, and the harmonic wavelet transform. The latter method is selected in this paper because band-pass filtering can be done without phase distortions, and the frequency ranges can be chosen very flexibly for the time-frequency analysis. Three algorithms for the time-frequency analysis of the non-stationary vibration power using the harmonic wavelet transform are discussed. The first is an algorithm for computation according to the full definition, while the others are approximate. Noting that the force and velocity decomposed into frequency ranges of interest by the harmonic wavelet transform are constructed with coefficients and basis functions, for the second algorithm, it is suggested to prepare a table of time integrals of the product of the basis functions in advance, which are independent of the signals under analysis. How to prepare and utilize the integral table are presented. The third algorithm is based on an evolutionary spectrum. Applications of the algorithms to the time-frequency analysis of the vibration power transmitted from an excitation source to a receiver structure in a simple mechanical system consisting of a cantilever beam and a reaction wheel are presented for illustration.

  4. Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Reppert, Mike; Tokmakoff, Andrei

    2015-08-01

    An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2-3 cm-1. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance.

  5. Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy

    SciTech Connect

    Reppert, Mike; Tokmakoff, Andrei

    2015-08-14

    An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2–3 cm{sup −1}. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance.

  6. Structures and vibrational frequency shifts of argon(n)hydrogen chloride clusters and vibrations of carbon monoxide adsorbed on copper(100) surface

    NASA Astrophysics Data System (ADS)

    Bahel, Atul

    1999-07-01

    The ability to vary the number of atoms or molecules in a cluster enables us to observe how its various structural and dynamical properties evolve with size, from those typical of isolated gas phase molecules towards the bulk limit. In an effort to understand the vibrational frequency shifts of hydrogen chloride solvated by argon atoms, a three-step methodology was implemented. First, Monte Carlo simulated annealing followed by a direct minimization using Newton-Raphson (NR) steps was employed to search the optimum geometries of ArnHCl (n = 1-12) clusters. In the second step, 5D quantum bound state calculations were performed to compute zero point energies of a cluster for HCl in the vibrational state of 0 and 1. Finally, the vibrational frequency shift of HCl in the cluster was calculated by taking the difference between two zero point energies. Our calculations show that the convergence of HCl vibrational shift to its matrix value is slow. It requires at least 5 solvation shells before it reaches within 1 cm- 1 and 8 solvation shells are needed for HCl to reach the vibrational shift of 15 cm-1 equal to its experimentally observed matrix value. During the course of this dissertation, we also studied adsorption of the CO molecule on Cu surface. The vibrational motions of adsorbed atoms and molecules play important roles in their chemistry and photochemistry. For adsorbates on metal surfaces, the most extensive experimental studies have been done on the vibrations of CO chemisorbed on Cu(100). However, theoretically it still remains a challenging task. To accurately compute the vibrations of CO adsorbed on Cu(100) surface, we improved 5D and implemented 6D quantum bound state discrete variable representation with successive diagonalization and truncation technique. A realistic many-body potential of Tully et al. [J. Vac. Sci. Technol. A 11, 1914 (1993)] was used for these calculations. Our 6D calculated value for the doubly degenerate CO translation is 27.3 cm- 1

  7. Time-dependent wave packet averaged vibrational frequencies from femtosecond stimulated Raman spectra

    NASA Astrophysics Data System (ADS)

    Wu, Yue-Chao; Zhao, Bin; Lee, Soo-Y.

    2016-02-01

    Femtosecond stimulated Raman spectroscopy (FSRS) on the Stokes side arises from a third order polarization, P(3)(t), which is given by an overlap of a first order wave packet, |" separators=" Ψ2 ( 1 ) ( p u , t ) > , prepared by a narrow band (ps) Raman pump pulse, Epu(t), on the upper electronic e2 potential energy surface (PES), with a second order wave packet, <" separators=" Ψ1 ( 2 ) ( p r ∗ , p u , t ) | , that is prepared on the lower electronic e1 PES by a broadband (fs) probe pulse, Epr(t), acting on the first-order wave packet. In off-resonant FSRS, |" separators=" Ψ2 ( 1 ) ( p u , t ) > resembles the zeroth order wave packet |" separators=" Ψ1 ( 0 ) ( t ) > on the lower PES spatially, but with a force on |" separators=" Ψ2 ( 1 ) ( p u , t ) > along the coordinates of the reporter modes due to displacements in the equilibrium position, so that <" separators=" Ψ1 ( 2 ) ( p r ∗ , p u , t ) | will oscillate along those coordinates thus giving rise to similar oscillations in P(3)(t) with the frequencies of the reporter modes. So, by recovering P(3)(t) from the FSRS spectrum, we are able to deduce information on the time-dependent quantum-mechanical wave packet averaged frequencies, ω ¯ j ( t ) , of the reporter modes j along the trajectory of |" separators=" Ψ1 ( 0 ) ( t ) > . The observable FSRS Raman gain is related to the imaginary part of P(3)(ω). The imaginary and real parts of P(3)(ω) are related by the Kramers-Kronig relation. Hence, from the FSRS Raman gain, we can obtain the complex P(3)(ω), whose Fourier transform then gives us the complex P(3)(t) to analyze for ω ¯ j ( t ) . We apply the theory, first, to a two-dimensional model system with one conformational mode of low frequency and one reporter vibrational mode of higher frequency with good results, and then we apply it to the time-resolved FSRS spectra of the cis-trans isomerization of retinal in rhodopsin [P. Kukura et al., Science 310, 1006 (2005)]. We obtain the vibrational

  8. Time-dependent wave packet averaged vibrational frequencies from femtosecond stimulated Raman spectra.

    PubMed

    Wu, Yue-Chao; Zhao, Bin; Lee, Soo-Y

    2016-02-07

    Femtosecond stimulated Raman spectroscopy (FSRS) on the Stokes side arises from a third order polarization, P(3)(t), which is given by an overlap of a first order wave packet, |Ψ2(1)(pu,t)>, prepared by a narrow band (ps) Raman pump pulse, Epu(t), on the upper electronic e2 potential energy surface (PES), with a second order wave packet, <Ψ1(2)(pr(∗),pu,t)|, that is prepared on the lower electronic e1 PES by a broadband (fs) probe pulse, Epr(t), acting on the first-order wave packet. In off-resonant |FSRS, Ψ2(1)(pu,t)> resembles the zeroth order wave packet |Ψ1(0)(t)> on the lower PES spatially, but with a force on |Ψ2(1)(pu,t)> along the coordinates of the reporter modes due to displacements in the equilibrium position, so that <Ψ1(2)(pr(∗),pu,t)| will oscillate along those coordinates thus giving rise to similar oscillations in P(3)(t) with the frequencies of the reporter modes. So, by recovering P(3)(t) from the FSRS spectrum, we are able to deduce information on the time-dependent quantum-mechanical wave packet averaged frequencies, ω̄j(t), of the reporter modes j along the trajectory of |Ψ1 (0)(t)>. The observable FSRS Raman gain is related to the imaginary part of P(3)(ω). The imaginary and real parts of P(3)(ω) are related by the Kramers-Kronig relation. Hence, from the FSRS Raman gain, we can obtain the complex P(3)(ω), whose Fourier transform then gives us the complex P(3)(t) to analyze for ω̄j(t). We apply the theory, first, to a two-dimensional model system with one conformational mode of low frequency and one reporter vibrational mode of higher frequency with good results, and then we apply it to the time-resolved FSRS spectra of the cis-trans isomerization of retinal in rhodopsin [P. Kukura et al., Science 310, 1006 (2005)]. We obtain the vibrational frequency up-shift time constants for the C12-H wagging mode at 216 fs and for the C10-H wagging mode at 161 fs which are larger than for the C11-H wagging mode at 127 fs, i.e., the C11-H

  9. Vibration signal analysis using parameterized time-frequency method for features extraction of varying-speed rotary machinery

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Dong, X. J.; Peng, Z. K.; Zhang, W. M.; Meng, G.

    2015-01-01

    In real application, when rotary machinery frequently involves variable-speed, unsteady load and defect, it will produce non-stationary vibration signal. Such signal can be characterized by mono- or multi-component frequency modulation (FM) and its internal instantaneous patterns are closely related to operation condition of the rotary machinery. For example, instantaneous frequency (IF) and instantaneous amplitude (IA) of a non-stationary signal are two important time-frequency features to be inspected. For vibration signal analysis of the rotary machinery, time-frequency analysis (TFA), known for analyzing the signal in the time and frequency domain simultaneously, has been accepted as a key signal processing tool. Particularly, parameterized TFA, among various TFAs, has shown great potential to investigate time-frequency features of non-stationary signals. It attracts more attention for improving time-frequency representation (TFR) with signal-dependent transform parameters. However, the parameter estimation and component separation are two problems to tackle with while using the parameterized TFA to extract time-frequency features from non-stationary vibration signal of varying-speed rotary machinery. In this paper, we propose a procedure for the parameterized TFA to analyze the non-stationary vibration signal of varying-speed rotary machinery. It basically includes four steps: initialization, estimation of transform parameter, component separation and parameterized TFA, as well as feature extraction. To demonstrate the effectiveness of the proposed method in analyzing mono- and multi-component signals, it is first used to analyze the vibration response of a laboratory rotor during a speed-up and run-down process, and then extract the instantaneous time-frequency signatures of a hydro-turbine rotor in a hydroelectric power station during a shut-down stage. In addition, the results are compared with several traditional TFAs and the proposed method outperforms

  10. A systematic theoretical study of harmonic vibrational frequencies: The ammonium ion NH4+ and other simple molecules

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yukio; Schaefer, Henry F.

    1980-09-01

    Analytic gradient techniques have been used to predict the harmonic vibrational frequencies of HCN, H2CO, H2O, CH4 and NH4+ at several levels of molecular electronic structure theory. Basis sets of double zeta, double zeta plus polarization, and extended plus polarization quality have been used in conjunction with self-consistent-field and configuration interaction methods. For the four spectroscopically characterized molecules, comparison with theory is particularly appropriate because experimental harmonic frequencies are available. For the 16 vibrational frequencies thus considered, the DZ SCF level of theory yields average errors of 166 cm-1 or 8.0%. The DZ+P SCF results are of comparable accuracy, differing on the average from experiment by 176 cm-1 or 8.3%. With the extended basis set, the comparable SCF frequency errors are only slightly less. The explicit incorporation of correlation effects qualitatively improves the agreement between theoretical and experimental harmonic vibrational frequencies. The DZ CI frequencies differ on the average by only 44 cm-1 or 2.0%. Perhaps surprisingly, the use of larger basis sets in conjunction with CI including all singly and doubly excited configurations leads to larger average errors in the vibrational frequencies. For example, the DZ+P CI frequencies have average errors of 80 cm-1 or 3.5%. Thus it seems clear that higher excitations (probably unlinked clusters especially) have a significant effect (order of 50 cm-1) on the theoretical prediction of polyatomic vibrational frequencies. The apparent discrepancy between the theoretical and experimental equilibrium geometry of CH4 is resolved here, and shown to have been a simple consequence of basis set incompleteness. Finally, the gas phase NH4+ equilibrium bond distance is predicted to be 1.022 Å, or 0.01-0.02 Å shorter than found by Ibers and Stevenson for NH4+ in crystalline NH4Cl and NH4F.

  11. Mixed quantum-classical molecular dynamics analysis of the molecular-level mechanisms of vibrational frequency shifts.

    PubMed

    Morales, Christine M; Thompson, Ward H

    2007-06-28

    A detailed analysis of the origins of vibrational frequency shifts of diatomic molecules (I2 and ICl) in a rare gas (Xe) liquid is presented. Specifically, vibrationally adiabatic mixed quantum-classical molecular dynamics simulations are used to obtain the instantaneous frequency shifts and correlate the shifts to solvent configurations. With this approach, important mechanistic questions are addressed, including the following: How many solvent atoms determine the frequency shift? What solvent atom configurations lead to blue shifts, and which lead to red shifts? What is the effect of solute asymmetry? The mechanistic analysis can be generally applied and should be useful in understanding what information is provided by infrared and Raman spectra about the environment of the probed vibrational mode.

  12. Detecting the classical harmonic vibrations of micro amplitudes and low frequencies with an atomic Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Huang, Yong-Yi

    2014-01-01

    We study the effects of atomic beams classical harmonic vibrations of micro amplitudes and low frequencies perpendicular to the wave vectors of atomic branches on the mean numbers of atoms arriving at the detectors in an atomic Mach-Zehnder interferometer, where the two atomic beams are in the same wave surface and have the same phase. We propose a vibrant factor to quantitatively describe the effects of atomic beams vibrations. It shows that: (i) the vibrant factor depends on the relative vibrant displacement and the initial phase rather than the absolute amplitude, (ii) the factor increases with the increase of the initial phase, and (iii) the frequencies can be derived from equal time interval measurements of the mean numbers of atoms arriving at the detectors. These results indicate that it is possible to detect the classical harmonic vibrations of micro amplitudes and low frequencies by measuring the variations in the mean numbers of atoms arriving at the detectors.

  13. Vibrational spectroscopy at interfaces by IR-VIS sum-frequency generation using CLIO FEL

    SciTech Connect

    Peremans, A.; Tadjeddine, A.; Wan Quan, Z.

    1995-12-31

    IR-vis sum-frequency generation (SFG) has developed into a versatile technique for probing the vibrational structure of interfaces. To overcome the limited spectral range accessible by benchtop IR lasers, we have developed an SFG spectrometer that makes use of the broad band tuneable infrared beam provided by the CLIO-FEL. We will evaluate the gain in sensitivity of the FEL-SFG spectrometer in comparison to that of benchtop lasers, taking account of the surface damage by laser heating. Thereafter, we review the different research projects undertaken using this facility: (1) The interface selectivity of SFG makes it particularly suitable for probing buried liquid/solid interface. We took advantage of the spectrometer sensitivity to monitor the electrochemical deposition of hydrogen on platinum single crystals at under- and overpotential (2) Because of its sensitivity to the molecular symmetry, SFG allows probing the conformation of self assembled monolayers deposited on metals. We discuss SFG spectra of {omega}(4-nitroanilino)-dodecane adsorbed on polycrystalline gold and silver films; in the 1550 - 900 cm{sup -1} spectral range. (3) We have undertaken a spectroscopic approach for the investigation of polymer films adhesion on glass. Polyurethane/glass interface is investigated in the 2200 - 1600 cin{sup -1} spectral region. (4) The use of the CLIO FEL allows probing of the vibrational dynamics of the prominent IR active vibrations between 1500 and 500 cm{sup -1} of fullerene epitaxial films. These modes are modified upon charge transfer from the substrate to the C{sub 60} molecules. Preliminary SFG spectra of C{sub 60}/Ag interface are presented. (5) Site specific detection of CO adsorption and CO + O coadsorption on Pd(111) are studied.

  14. Dispersion corrected DFT approaches for Anharmonic Vibrational Frequency Calculations: Nucleobases and their Dimers

    PubMed Central

    Fornaro, Teresa; Biczysko, Malgorzata; Monti, Susanna; Barone, Vincenzo

    2015-01-01

    Computational spectroscopy techniques have become in the last years effective means to analyze and assign infrared (IR) spectra for molecular systems of increasing dimensions and in different environments. However, transition from compilations of harmonic data to full anharmonic simulations of spectra is still under way. The most promising results for large systems have been obtained, in our opinion, by perturbative vibrational approaches based on potential energy surfaces computed by hybrid (especially B3LYP) density functionals and medium size (e.g. SNSD) basis sets. In this framework, we are actively developing a comprehensive and robust computational protocol aimed to a quantitative reproduction of the spectra of nucleic acid bases complexes and their adsorption on solid supports (organic/inorganic). In this contribution we report the essential results of the first step devoted to isolated monomers and dimers. It is well known that in order to model the vibrational spectra of weakly bound molecular complexes dispersion interactions should be taken into proper account. In this work, we have chosen two popular and inexpensive approaches to model dispersion interaction, namely the semi-empirical dispersion correction (D3) and pseudopotential based (DCP) methodologies both in conjunction with the B3LYP functional. These have been used for simulating fully anharmonic IR spectra of nucleobases and their dimers through generalized second order vibrational perturbation theory (GVPT2). We have studied, in particular, isolated adenine, hypoxanthine, uracil, thymine and cytosine, the hydrogen-bonded and stacked adenine and uracil dimers, and the stacked adenine-naphthalene heterodimer. Anharmonic frequencies are compared with standard B3LYP results and experimental findings, while the computed interaction energies and structures of complexes are compared to the best available theoretical estimates. PMID:24531740

  15. Observation of the low frequency vibrational modes of bacteriophage M13 in water by Raman spectroscopy

    PubMed Central

    Tsen, KT; Dykeman, Eric C; Sankey, Otto F; Lin, Nien-Tsung; Tsen, Shaw-Wei D; Kiang, Juliann G

    2006-01-01

    Background Recently, a technique which departs radically from conventional approaches has been proposed. This novel technique utilizes biological objects such as viruses as nano-templates for the fabrication of nanostructure elements. For example, rod-shaped viruses such as the M13 phage and tobacco mosaic virus have been successfully used as biological templates for the synthesis of semiconductor and metallic nanowires. Results and discussion Low wave number (≤ 20 cm-1) acoustic vibrations of the M13 phage have been studied using Raman spectroscopy. The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode has been shown to belong to one of the Raman-active axial torsion modes of the M13 phage protein coat. Conclusion It is expected that the detection and characterization of this low frequency vibrational mode can be used for applications in nanotechnology such as for monitoring the process of virus functionalization and self-assembly. For example, the differences in Raman spectra can be used to monitor the coating of virus with some other materials and nano-assembly process, such as attaching a carbon nanotube or quantum dots. PMID:16995944

  16. Revealing structural properties of the marine nanolayer from vibrational sum frequency generation spectra

    NASA Astrophysics Data System (ADS)

    Laß, K.; Friedrichs, G.

    2011-08-01

    Natural nanolayers originating from sea surface and subsurface water samples collected in the Baltic Sea have been investigated using surface-sensitive vibrational sum frequency generation (VSFG) spectroscopy. Distinct spectral signatures of CH and OH bond stretch vibrations have been detected at wavenumbers ranging from 2700 to 3900 cm-1. Measured water-air interface spectra as well as observed signal intensity trends are discussed in terms of composition and structure of the natural organic nanolayer. Reasoning was based on the comparison with reference spectra, spectral trends inferred from previous VSFG studies, reported average composition of dissolved organic matter in seawater, and simplified assumption that surfactants can be classified as soluble (wet) and insoluble (dry) surfactants. Wet surfactants have been found to be dominant, and often lipid-like compounds form a very dense surfactant nanolayer. Supported by comparison spectra of xanthan gum solutions, the observed VSFG spectral signatures were tentatively assigned to lipopolysaccharides or other lipid-like compounds embedded in colloidal matrices of polymeric material. In addition, VSFG spectra of a polluted harbor water sample and a water sample covered with diesel oil are reported.

  17. Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.

    1993-01-01

    The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbation estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10, 472 +/- 5, and 2051 +/- 10 cm(exp -1) for omega(sub 1), omega(sub 2), and omega(sub 3), respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental nu(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.

  18. Accurate Quartic Force Fields and Vibrational Frequencies for HCN and HNC

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.; Gazdy, Bela; Bowman, Joel M.

    1993-01-01

    The quartic force fields of HCN and HNC are determined using atomic natural orbital one-particle basis sets of spdf/spd and spdfg/spdf quality in conjunction with the CCSD(T) electron correlation method (singles and doubles coupled-cluster theory plus a perturbational estimate of the effects of connected triple excitations). The HCN force field is in good agreement with a recent experimentally derived force field and also with the force field recently computed by Wong and Bacskay. On the basis of the good agreement obtained for HCN, it is argued that the ab initio quartic force field for HNC is superior to a prior force field derived from experiment. The harmonic frequencies of HNC are predicted to be 3822 +/- 10,472 +/- 5, and 2051 +/-10/cm for omega1, omega2, and omega3, respectively; the experimentally derived values are above these values and fall outside the estimated uncertainties. Using the quartic force field, spectroscopic constants are predicted for HNC based on a vibrational second-order perturbation theory analysis. It is also asserted that the gas-phase fundamental v(sub 3) for HNC is slightly lower than the matrix isolation value. The range of validity of the quartic force fields is investigated by comparison of variational vibrational energies computed with the quartic force fields to those obtained from our recently reported global HCN/HNC potential energy surface and also to experimental data.

  19. Ab Initio Potential Energy Surfaces and the Calculation of Accurate Vibrational Frequencies

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.; Martin, Jan M. L.; Taylor, Peter R.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Due to advances in quantum mechanical methods over the last few years, it is now possible to determine ab initio potential energy surfaces in which fundamental vibrational frequencies are accurate to within plus or minus 8 cm(exp -1) on average, and molecular bond distances are accurate to within plus or minus 0.001-0.003 Angstroms, depending on the nature of the bond. That is, the potential energy surfaces have not been scaled or empirically adjusted in any way, showing that theoretical methods have progressed to the point of being useful in analyzing spectra that are not from a tightly controlled laboratory environment, such as vibrational spectra from the interstellar medium. Some recent examples demonstrating this accuracy will be presented and discussed. These include the HNO, CH4, C2H4, and ClCN molecules. The HNO molecule is interesting due to the very large H-N anharmonicity, while ClCN has a very large Fermi resonance. The ab initio studies for the CH4 and C2H4 molecules present the first accurate full quartic force fields of any kind (i.e., whether theoretical or empirical) for a five-atom and six-atom system, respectively.

  20. Ab Initio Potential Energy Surfaces and the Calculation of Accurate Vibrational Frequencies

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Dateo, Christopher E.; Martin, Jan M. L.; Taylor, Peter R.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Due to advances in quantum mechanical methods over the last few years, it is now possible to determine ab initio potential energy surfaces in which fundamental vibrational frequencies are accurate to within plus or minus 8 cm(exp -1) on average, and molecular bond distances are accurate to within plus or minus 0.001-0.003 Angstroms, depending on the nature of the bond. That is, the potential energy surfaces have not been scaled or empirically adjusted in any way, showing that theoretical methods have progressed to the point of being useful in analyzing spectra that are not from a tightly controlled laboratory environment, such as vibrational spectra from the interstellar medium. Some recent examples demonstrating this accuracy will be presented and discussed. These include the HNO, CH4, C2H4, and ClCN molecules. The HNO molecule is interesting due to the very large H-N anharmonicity, while ClCN has a very large Fermi resonance. The ab initio studies for the CH4 and C2H4 molecules present the first accurate full quartic force fields of any kind (i.e., whether theoretical or empirical) for a five-atom and six-atom system, respectively.

  1. The acute effects of different whole-body vibration amplitudes and frequencies on flexibility and vertical jumping performance.

    PubMed

    Gerodimos, Vassilis; Zafeiridis, Andreas; Karatrantou, Konstantina; Vasilopoulou, Theodora; Chanou, Konstantina; Pispirikou, Eleni

    2010-07-01

    Frequency and amplitude determine the training load of whole-body vibration (WBV) exercise and thereby possible neuromuscular adaptations. We investigated the effects of amplitude and frequency of a single bout of WBV on flexibility and squat jump performance (SJ) and the time-course of these effects. In the amplitude study, twenty-five females performed three vibration protocols (VPs) for 6 min at frequency of 25Hz and amplitudes of 4 mm, 6 mm, and 8 mm and one control protocol (CP). In the frequency study, eighteen females performed three VPs at 6mm amplitude and frequencies of 15 Hz, 20 Hz, and 30 Hz and one CP. Flexibility and SJ were measured before, immediately-post and 15 min recovery. All protocols were performed on a side-to-side alternating vibration plate. In the amplitude study, flexibility was improved (p<0.01) immediately-post in VP4, VP6, VP8 (31.8+/-8.2, 31.9+/-7.6, 31.5+/-7.9, respectively) and at 15 min recovery (31.6+/-8.1, 31.5+/-7.9, 31.0+/-8.2, respectively) vs. pre-vibration (30.2+/-8.6, 30.3+/-8.1, 30.2+/-8.3, respectively), but remained unchanged in CP (30.6+/-8.3 immediately-post, 30.7+/-8.2 at 15 min vs. 30.4+/-8.2 pre-vibration). In the frequency study, flexibility was improved (p<0.01) immediately-post in VP15, VP20, VP30 (31.5+/-5.2, 31.3+/-5, 31.7+/-5.3, respectively) and at 15 min recovery (31.3+/-5.4, 31.3+/-5.0, 31.3+/-5.3, respectively) vs. pre-vibration (30.6+/-5.4, 30.2+/-5.7, 30.3+/-5.9, respectively), but not in CP (30.7+/-5.1 immediately-post, 30.6+/-5 at 15 min vs. pre-vibration 30.5+/-5.7). There were no significant effects of amplitude or frequency on SJ. In conclusion, a single WBV bout using a side-to-side alternating vibration plate may increase flexibility which persists for at least 15 min, without altering jumping performance. These effects were observed irrespective of frequency and amplitude.

  2. Stability of high-frequency periodic motions of a heavy rigid body with a horizontally vibrating suspension point

    NASA Astrophysics Data System (ADS)

    Belichenko, M. V.

    2016-11-01

    The motion of a heavy rigid body one of whose points (the suspension point) executes horizontal harmonic high-frequency vibrations with small amplitude is considered. The problem of existence of high-frequency periodic motions with period equal to the period of the suspension point vibrations is considered. The stability conditions for the revealed motions are obtained in the linear approximation. The following three special cases of mass distribution in the body are considered; a body whose center of mass lies on the principal axis of inertia, a body whose center of mass lies in the principal plane of inertia, and a dynamically symmetric body.

  3. Theoretical study of sum-frequency vibrational spectroscopy on limonene surface.

    PubMed

    Zheng, Ren-Hui; Wei, Wen-Mei; Liu, Hao; Jing, Yuan-Yuan; Wang, Bo-Yang; Shi, Qiang

    2014-03-14

    By combining molecule dynamics (MD) simulation and quantum chemistry computation, we calculate the surface sum-frequency vibrational spectroscopy (SFVS) of R-limonene molecules at the gas-liquid interface for SSP, PPP, and SPS polarization combinations. The distributions of the Euler angles are obtained using MD simulation, the ψ-distribution is between isotropic and Gaussian. Instead of the MD distributions, different analytical distributions such as the δ-function, Gaussian and isotropic distributions are applied to simulate surface SFVS. We find that different distributions significantly affect the absolute SFVS intensity and also influence on relative SFVS intensity, and the δ-function distribution should be used with caution when the orientation distribution is broad. Furthermore, the reason that the SPS signal is weak in reflected arrangement is discussed.

  4. Vibrational Sum Frequency Spectroscopy on Polyelectrolyte Multilayers: Effect of Molecular Surface Structure on Macroscopic Wetting Properties.

    PubMed

    Gustafsson, Emil; Hedberg, Jonas; Larsson, Per A; Wågberg, Lars; Johnson, C Magnus

    2015-04-21

    Adsorption of a single layer of molecules on a surface, or even a reorientation of already present molecules, can significantly affect the surface properties of a material. In this study, vibrational sum frequency spectroscopy (VSFS) has been used to study the change in molecular structure at the solid-air interface following thermal curing of polyelectrolyte multilayers of poly(allylamine hydrochloride) and poly(acrylic acid). Significant changes in the VSF spectra were observed after curing. These changes were accompanied by a distinct increase in the static water contact angle, showing how the properties of the layer-by-layer molecular structure are controlled not just by the polyelectrolyte in the outermost layer but ultimately by the orientation of the chemical constituents in the outermost layers.

  5. Vibrationally resonant sum-frequency generation microscopy with a solid immersion lens

    PubMed Central

    Lee, Eun Seong; Lee, Sang-Won; Hsu, Julie; Potma, Eric O.

    2014-01-01

    We use a hemispheric sapphire lens in combination with an off-axis parabolic mirror to demonstrate high-resolution vibrationally resonant sum-frequency generation (VR-SFG) microscopy in the mid-infrared range. With the sapphire lens as an immersed solid medium, the numerical aperture (NA) of the parabolic mirror objective is enhanced by a factor of 1.72, from 0.42 to 0.72, close to the theoretical value of 1.76 ( = nsapphire). The measured lateral resolution is as high as 0.64 μm. We show the practical utility of the sapphire immersion lens by imaging collagen-rich tissues with and without the solid immersion lens. PMID:25071953

  6. Note: A kinematic shaker system for high amplitude, low frequency vibration testing

    NASA Astrophysics Data System (ADS)

    Swaminathan, Anand; Poese, Matthew E.; Smith, Robert W. M.; Garrett, Steven L.

    2015-11-01

    This note describes a shaker system capable of high peak-velocity, large amplitude, low frequency, near-sinusoidal excitation that has been constructed and employed in experiments on the inhibition of Rayleigh-Bénard convection using acceleration modulation. The production of high peak-velocity vibration is of interest in parametric excitation problems of this type and reaches beyond the capabilities of standard electromagnetic shakers. The shaker system described employs a kinematic linkage to two counter-rotating flywheels, driven by a variable-speed electrical motor, producing peak-to-peak displacements of 15.24 cm to a platform mounted on two guide rails. In operation, this shaker has been demonstrated to produce peak speeds of up to 3.7 m/s without failure.

  7. Note: A kinematic shaker system for high amplitude, low frequency vibration testing.

    PubMed

    Swaminathan, Anand; Poese, Matthew E; Smith, Robert W M; Garrett, Steven L

    2015-11-01

    This note describes a shaker system capable of high peak-velocity, large amplitude, low frequency, near-sinusoidal excitation that has been constructed and employed in experiments on the inhibition of Rayleigh-Bénard convection using acceleration modulation. The production of high peak-velocity vibration is of interest in parametric excitation problems of this type and reaches beyond the capabilities of standard electromagnetic shakers. The shaker system described employs a kinematic linkage to two counter-rotating flywheels, driven by a variable-speed electrical motor, producing peak-to-peak displacements of 15.24 cm to a platform mounted on two guide rails. In operation, this shaker has been demonstrated to produce peak speeds of up to 3.7 m/s without failure.

  8. Sum Frequency Generation Vibrational Spectroscopy of Pyridine Hydrogenation on Platinum Nanoparticles

    SciTech Connect

    Bratlie, Kaitlin M.; Komvopoulos, Kyriakos; Somorjai, Gabor A.

    2008-02-22

    Pyridine hydrogenation in the presence of a surface monolayer consisting of cubic Pt nanoparticles stabilized by tetradecyltrimethylammonium bromide (TTAB) was investigated by sum frequency generation (SFG) vibrational spectroscopy using total internal reflection (TIR) geometry. TIR-SFG spectra analysis revealed that a pyridinium cation (C{sub 5}H{sub 5}NH{sup +}) forms during pyridine hydrogenation on the Pt nanoparticle surface, and the NH group in the C{sub 5}H{sub 5}NH{sup +} cation becomes more hydrogen bound with the increase of the temperature. In addition, the surface coverage of the cation decreases with the increase of the temperature. An important contribution of this study is the in situ identification of reaction intermediates adsorbed on the Pt nanoparticle monolayer during pyridine hydrogenation.

  9. Disturbance rejection control for vibration suppression of smart beams and plates under a high frequency excitation

    NASA Astrophysics Data System (ADS)

    Zhang, Shun-Qi; Schmidt, Rüdiger; Müller, Peter C.; Qin, Xian-Sheng

    2015-09-01

    This paper aims to perfect the method of Disturbance Rejection (DR) control, based on our earlier published work (Zhang et al. 2014 [1]), for vibration suppression of smart structures under high frequency periodic disturbances. Two observation structures are discussed, namely Proportional-Integral (PI) observer which uses step functions as the fictitious model of disturbances and Generalized PI (GPI) observer which can employ any nonlinear functions. In order to stabilize the PI or GPI observer, Lyapunov and Riccati approaches are implemented and discussed. Furthermore, approximate and exact solutions are developed for obtaining control gains. These various possibilities of DR control are simulated and compared with each other, as well as those obtained by conventional control strategies, PID and LQR control.

  10. Mixed Polarization Vibrational Sum Frequency Generation Spectra of Organic Semiconducting Thin Films

    NASA Astrophysics Data System (ADS)

    Kearns, Patrick; Sohrabpour, Zahara; Massari, Aaron M.

    2014-06-01

    The buried interface of an organic semiconductor at the dielectric has a large on influence on the function of organic field effect transistors (OFETs). The use of vibrational sum frequency generation (VSFG) to obtain structural and orientational information on the buried interfaces of organic thin films has historically been complicated by the signals from other interfaces in the system. A thin film of N,N'-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) was deposited on a SiO2 dielectric to simulate the interfaces found in OFETs. We will show how probing the sample with a varying mixture of linear polarizations in the experimental setup can deconvolute contributions to the overall signal from multiple interfaces.

  11. Theoretical study of sum-frequency vibrational spectroscopy on limonene surface

    SciTech Connect

    Zheng, Ren-Hui Liu, Hao; Jing, Yuan-Yuan; Wang, Bo-Yang; Shi, Qiang; Wei, Wen-Mei

    2014-03-14

    By combining molecule dynamics (MD) simulation and quantum chemistry computation, we calculate the surface sum-frequency vibrational spectroscopy (SFVS) of R-limonene molecules at the gas-liquid interface for SSP, PPP, and SPS polarization combinations. The distributions of the Euler angles are obtained using MD simulation, the ψ-distribution is between isotropic and Gaussian. Instead of the MD distributions, different analytical distributions such as the δ-function, Gaussian and isotropic distributions are applied to simulate surface SFVS. We find that different distributions significantly affect the absolute SFVS intensity and also influence on relative SFVS intensity, and the δ-function distribution should be used with caution when the orientation distribution is broad. Furthermore, the reason that the SPS signal is weak in reflected arrangement is discussed.

  12. The effect of low-frequency mechanical vibration on retention in an orthodontic relapse model.

    PubMed

    Yadav, Sumit; Assefnia, Amir; Gupta, Himank; Vishwanath, Meenakshi; Kalajzic, Zana; Allareddy, Veerasathpurush; Nanda, Ravindra

    2016-02-01

    To investigate the effect of low-frequency mechanical vibration (LFMV) on the prevention of relapse after active orthodontic tooth movement, bone volume fraction (BVF), tissue density, and the integrity of periodontal ligament. Thirty male CD1, 12-week-old mice were used for the study. Mice were randomly divided into three groups: 1. control group, 2. relapse group, and 3. relapse + 30 Hz vibration group. In the control group, first molar was moved mesially for 7 days using nickel-titanium coil spring delivering 10g of force, whereas in relapse and relapse + 30 Hz groups, first molar was moved mesially for 7 days and then orthodontic force was removed and molar was allowed to relapse for 7 days. In relapse + 30 Hz group, LFMVs were applied at 30 Hz. Micro-focus computed tomography (micro-CT) was used for tooth movement measurements (relapse), BVF, and tissue density. Additionally, immunostaining for sclerostin, tartrate-resistant acid phosphatase staining, and picro-sirius red staining were performed on histological sections. LFMV at 30 Hz showed a tendency to decrease relapse but was not statistically significant. Micro-CT analysis showed a trend towards increase in BVF and tissue density with application of LFMV. Sclerostin expression was decreased with 30 Hz vibration. Additionally, the picro-sirius staining showed that LFMV at 30 Hz helped in maintaining the thickness and integrity of collagen fibres in periodontal ligament. This is an animal study and extrapolation of the current findings to the clinical situation must be done with caution, as there is no osteonal remodelling (secondary remodelling) in mice when compared to humans. There was no statistically significant difference in the amount of relapse between the relapse-only and relapse + 30 Hz groups. However, there was a trend of decrease in relapse with 30 Hz mechanical vibration. © The Author 2015. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved

  13. First-principles investigation for M(CO)n/Ag(110) (M=Fe, Co, Ni, Cu, Zn, and Ag; n=1, 2) systems: Geometries, STM images, and vibrational frequencies

    NASA Astrophysics Data System (ADS)

    Yuan, Lan-Feng; Yang, Jinlong; Li, Qunxiang; Zhu, Qing-Shi

    2002-01-01

    Fe, Cu atoms and CO molecules were manipulated with a scanning tunneling microscope (STM) on a Ag(110) surface, and one or two CO can transfer from the surface and bond with a metal atom through the STM tip [H. J. Lee and W. Ho, Science 286, 1719 (1999); Phys. Rev. B 61, R16347 (2000)]. We perform a density-functional cluster model investigation for the systems. The experimental geometries are validated and understood using the frontier orbital theory. The STM topographic images are reproduced. The vibrational frequencies of the adsorbate systems are obtained by diagonalizing the second-derivative matrices and are in excellent agreement with the experimental measurements. The geometries and C-O stretch frequencies are predicted for systems with the adsorbate metal atom being Co, Ni, Zn, and Ag. These systems can be divided to two classes, and each class exhibits a different set of properties.

  14. A high figure of merit vibrational energy harvester for low frequency applications

    NASA Astrophysics Data System (ADS)

    Nico, V.; Boco, E.; Frizzell, R.; Punch, J.

    2016-01-01

    Small-scale vibration energy harvesters that respond efficiently at low frequencies are challenging to realize. This paper describes the design and implementation of one such harvester, which achieves a high volumetric Figure of Merit (FoMv = 2.6% at 11.50 Hz) at the scale of a C-type battery and outperforms other state-of-the-art devices in the sub 20 Hz frequency range. The device employs a 2 Degree-of-Freedom velocity-amplified approach and electromagnetic transduction. The harvester comprises two masses oscillating one inside the other, between four sets of magnetic springs. Collisions between the two masses transfer momentum from the heavier to the lighter mass, exploiting velocity amplification. The paper first presents guidelines for designing and optimizing the transduction mechanism, before a nonlinear numerical model for the system dynamics is developed. Experimental characterisation of the harvester design is then presented to validate both the transducer optimization and the dynamics model. The resulting high FoMV demonstrates the effectiveness of the device for low frequency applications, such as human motion.

  15. Nonlinearity in eardrum vibration as a function of frequency and sound pressure.

    PubMed

    Aerts, J R M; Dirckx, J J J

    2010-05-01

    It is generally accepted that the middle ear acts mainly as a linear system for sound pressures up to 130 dB SPL in the auditory frequency range. However, at quasi-static pressure loads a strong nonlinear response has been demonstrated. Consequently, small nonlinear distortions may also be present in the middle ear response in the auditory frequency range. A new measurement method was developed to quickly determine vibration response, nonlinear distortions and noise level of acoustically driven biomechanical systems. Specially designed multisines are used for the excitation of the test system. The method is applied on a gerbil eardrum for sound pressures ranging from 90 to 120 dB SPL and for frequencies ranging from 125 Hz to 16 kHz. The experiments show that nonlinear distortions rise above noise level at a sound pressure of 96 dB SPL, and they grow as sound pressure increases. Post-mortem changes in the middle ear influence the nonlinear distortions rapidly until a stabilization occurs after approximately 3h. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  16. A study of the eigenvectors of the low-frequency vibrational modes in crystalline adenosine via high pressure Raman spectroscopy.

    PubMed

    Lee, Scott A; Pinnick, David A; Anderson, A

    2014-12-01

    High-pressure Raman spectroscopy has been used to study the eigenvectors and eigenvalues of the vibrational modes of crystalline adenosine at 295 K by evaluating the logarithmic derivative of the vibrational frequency with respect to pressure: [Formula: see text]. Crystalline samples of molecular materials such as adenosine will have vibrational modes that are localized within a molecular unit ("internal" modes) as well as modes in which the molecular units vibrate against each other ("external" modes). The value of the logarithmic derivative is found to be a diagnostic probe of the nature of the eigenvector of the vibrational modes. Stretching modes which are predominantly internal to the molecule have low logarithmic derivatives while external modes have higher logarithmic derivatives. Particular interest is paid to the low-frequency (≤150 cm(-1)) modes. Based on the pressure dependence of its logarithmic derivative, a mode near 49 cm(-1) is identified as internal mode. The other modes below 400 cm(-1) have pressure dependences of their logarithmic derivatives consistent with being either (1) modes which are mainly external, meaning that the molecules of the unit cell vibrate against each other in translational or librational motions (or linear combinations thereof), or (2) torsional or bending modes involving a large number of atoms, mainly within a molecule. The modes above 400 cm(-1) all have pressure dependences of their logarithmic derivatives consistent with being mainly internal modes.

  17. The effects of whole-body vibration on the Wingate test for anaerobic power when applying individualized frequencies.

    PubMed

    Surowiec, Rachel K; Wang, Henry; Nagelkirk, Paul R; Frame, Jeffrey W; Dickin, D Clark

    2014-07-01

    Recently, individualized frequency (I-Freq) has been introduced with the notion that athletes may elicit a greater reflex response at differing levels (Hz) of vibration. The aim of the study was to evaluate acute whole-body vibration as a feasible intervention to increase power in trained cyclists and evaluate the efficacy of using I-Freq as an alternative to 30Hz, a common frequency seen in the literature. Twelve highly trained, competitive male cyclists (age, 29.9 ± 10.0 years; body height, 175.4 ± 7.8 cm; body mass, 77.3 ± 13.9 kg) participated in the study. A Wingate test for anaerobic power was administered on 3 occasions: following a control of no vibration, 30 Hz, or I-freq. Measures of peak power, average power (AP), and the rate of fatigue were recorded and compared with the vibration conditions using separate repeated measures analysis of variance. Peak power, AP, and the rate of fatigue were not significantly impacted by either the 30 Hz or I-Freq vibration interventions (p > 0.05). Given the trained status of the individuals in this study, the ability to elicit an acute response may have been muted. Future studies should further refine the vibration parameters used and assess changes in untrained or recreationally trained populations.

  18. A boundary-element method using broadband vibrating-wall sources to predict high-frequency interior sound fields produced by wall vibration

    NASA Astrophysics Data System (ADS)

    Franzoni, Linda P.; Duvall, Tracy A.

    2005-09-01

    In the high-frequency limit, vibrating panels subject to spatially random, temporally broadband forcing are shown to have broadband power and directivity properties than can be characterized by a limited set of parameters, based on numerical simulations. The radiated pressure field is parametrized in terms of direction, wave speed ratio, panel damping, and dimensionless frequency. A source directivity equation dependent on these variables is presented. The radiation properties of this equation are incorporated to simulate vibrating wall panels in an energy/intensity-based boundary-element method (BEM) developed for the prediction of steady-state, broadband, reverberant sound fields in enclosures having either diffusely or specularly reflecting boundaries. The BEM method uses uncorrelated broadband directional intensity sources to construct the source and reflection sound fields and predict mean-square pressure distributions in enclosures. Because uncorrelated broadband directional intensity sources are used, the system does not require a frequency-by-frequency-based solution, thereby reducing computational expense. Simulations are compared to exact solutions obtained by computationally expensive frequency-by-frequency modal methods. When fully developed, the directed application of this method is aircraft interior noise caused by exterior boundary layer excitation on fuselage panels.

  19. Energy Expenditure and Substrate Oxidation in Response to Side-Alternating Whole Body Vibration across Three Commonly-Used Vibration Frequencies

    PubMed Central

    Fares, Elie-Jacques; Charrière, Nathalie; Montani, Jean-Pierre; Schutz, Yves; Dulloo, Abdul G.; Miles-Chan, Jennifer L.

    2016-01-01

    Background and Aim There is increasing recognition about the importance of enhancing energy expenditure (EE) for weight control through increases in low-intensity physical activities comparable with daily life (1.5–4 METS). Whole-body vibration (WBV) increases EE modestly and could present both a useful adjuvant for obesity management and tool for metabolic phenotyping. However, it is unclear whether a “dose-response” exists between commonly-used vibration frequencies (VF) and EE, nor if WBV influences respiratory quotient (RQ), and hence substrate oxidation. We aimed to investigate the EE-VF and RQ-VF relationships across three different frequencies (30, 40, and 50Hz). Methods EE and RQ were measured in 8 healthy young adults by indirect calorimetry at rest, and subsequently during side-alternating WBV at one of 3 VFs (30, 40, and 50 Hz). Each frequency was assessed over 5 cycles of intermittent WBV (30s vibration/30s rest), separated by 5 min seated rest. During the WBV participants stood on the platform with knees flexed sufficiently to maintain comfort, prevent transmission of vibration to the upper body, and minimise voluntary physical exertion. Repeatability was assessed across 3 separate days in a subset of 4 individuals. In order to assess any sequence/habituation effect, an additional group of 6 men underwent 5 cycles of intermittent WBV (30s vibration/30s rest) at 40 Hz, separated by 5 min seated rest. Results Side-alternating WBV increased EE relative to standing, non-vibration levels (+36%, p<0.001). However, no differences in EE were observed across VFs. Similarly, no effect of VF on RQ was found, nor did WBV alter RQ relative to standing without vibration. Conclusion No relationship could be demonstrated between EE and VF in the range of 30-50Hz, and substrate oxidation did not change in response to WBV. Furthermore, the thermogenic effect of intermittent WBV, whilst robust, was quantitatively small (<2 METS). PMID:26974147

  20. Analytical Harmonic Vibrational Frequencies for the Green Fluorescent Protein Computed with ONIOM: Chromophore Mode Character and Its Response to Environment.

    PubMed

    Thompson, Lee M; Lasoroski, Aurélie; Champion, Paul M; Sage, J Timothy; Frisch, Michael J; van Thor, Jasper J; Bearpark, Michael J

    2014-02-11

    A systematic comparison of different environmental effects on the vibrational modes of the 4-hydroxybenzylidene-2,3-dimethylimidazolinone (HBDI) chromophore using the ONIOM method allows us to model how the molecule's spectroscopic transitions are modified in the Green Fluorescent Protein (GFP). ONIOM(QM:MM) reduces the expense of normal mode calculations when computing the majority of second derivatives only at the MM level. New developments described here for the efficient solution of the CPHF equations, including contributions from electrostatic interactions with environment charges, mean that QM model systems of ∼100 atoms can be embedded within a much larger MM environment of ∼5000 atoms. The resulting vibrational normal modes, their associated frequencies, and dipole derivative vectors have been used to interpret experimental difference spectra (GFPI2-GFPA), chromophore vibrational Stark shifts, and changes in the difference between electronic and vibrational transition dipoles (mode angles) in the protein environment.

  1. Accurate Lineshapes from Sub-1 cm-1 Resolution Sum Frequency Generation Vibrational Spectroscopy of α-Pinene at Room Temperature

    SciTech Connect

    Mifflin, Amanda L.; Velarde Ruiz Esparza, Luis A.; Ho, Junming; Psciuk, Brian; Negre, Christian; Ebben, Carlena J.; Upshur, Mary Alice; Lu, Zhou; Strick, Benjamin; Thomson, Regan; Batista, Victor; Wang, Hongfei; Geiger, Franz M.

    2015-02-26

    Room temperature sub-wavenumber high-resolution broadband sum frequency generation (HR-BB-SFG) spectra of the common terpene (+)-α-pinene reveal ten peaks in the C–H stretching region. The spectral resolution exceeds that of Fourier transform infrared, femtosecond stimulated Raman, and traditional BB-SFG and scanning SFG spectroscopy of the same molecule. Experiment and simulation show the spectral lineshapes to be accurate. Homogeneous vibrational decoherence lifetimes of up to 1.7 psec are assigned to specific oscillators and compare favorably to lifetimes computed from density functional tight binding molecular dynamics calculations, while phase-resolved spectra yield orientation information for them. We propose the new spectroscopy as an attractive alternative to time-resolved vibrational spectroscopy or heterodyne-detection schemes for studying vibrational energy relaxation and vibrational coherences in molecules.

  2. Spatial hearing in Cope's gray treefrog: II. Frequency-dependent directionality in the amplitude and phase of tympanum vibrations.

    PubMed

    Caldwell, Michael S; Lee, Norman; Schrode, Katrina M; Johns, Anastasia R; Christensen-Dalsgaard, Jakob; Bee, Mark A

    2014-04-01

    Anuran ears function as pressure difference receivers, and the amplitude and phase of tympanum vibrations are inherently directional, varying with sound incident angle. We quantified the nature of this directionality for Cope's gray treefrog, Hyla chrysoscelis. We presented subjects with pure tones, advertisement calls, and frequency-modulated sweeps to examine the influence of frequency, signal level, lung inflation, and sex on ear directionality. Interaural differences in the amplitude of tympanum vibrations were 1-4 dB greater than sound pressure differences adjacent to the two tympana, while interaural differences in the phase of tympanum vibration were similar to or smaller than those in sound phase. Directionality in the amplitude and phase of tympanum vibration were highly dependent on sound frequency, and directionality in amplitude varied slightly with signal level. Directionality in the amplitude and phase of tone- and call-evoked responses did not differ between sexes. Lung inflation strongly affected tympanum directionality over a narrow frequency range that, in females, included call frequencies. This study provides a foundation for further work on the biomechanics and neural mechanisms of spatial hearing in H. chrysoscelis, and lends valuable perspective to behavioral studies on the use of spatial information by this species and other frogs.

  3. Rovibrational spectroscopic constants and fundamental vibrational frequencies for isotopologues of cyclic and bent singlet HC{sub 2}N isomers

    SciTech Connect

    Inostroza, Natalia; Fortenberry, Ryan C.; Lee, Timothy J.; Huang, Xinchuan

    2013-12-01

    Through established, highly accurate ab initio quartic force fields, a complete set of fundamental vibrational frequencies, rotational constants, and rovibrational coupling and centrifugal distortion constants have been determined for both the cyclic 1 {sup 1} A' and bent 2 {sup 1} A' DCCN, H{sup 13}CCN, HC{sup 13}CN, and HCC{sup 15}N isotopologues of HCCN. Spectroscopic constants are computed for all isotopologues using second-order vibrational perturbation theory (VPT2), and the fundamental vibrational frequencies are computed with VPT2 and vibrational configuration interaction (VCI) theory. Agreement between VPT2 and VCI results is quite good, with the fundamental vibrational frequencies of the bent isomer isotopologues in accord to within a 0.1-3.2 cm{sup –1} range. Similar accuracies are present for the cyclic isomer isotopologues. The data generated here serve as a reference for astronomical observations of these closed-shell, highly dipolar molecules using new, high-resolution telescopes and as reference for laboratory studies where isotopic labeling may lead to elucidation of the formation mechanism for the known interstellar molecule: X {sup 3} A' HCCN.

  4. Rovibrational Spectroscopic Constants and Fundamental Vibrational Frequencies for Isotopologues of Cyclic and Bent Singlet HC2N isomers

    NASA Technical Reports Server (NTRS)

    Inostroza, Natalia; Fortenberry, Ryan C.; Huang, Xinchuan; Lee, Timothy J.

    2013-01-01

    Through established, highly-accurate ab initio quartic force fields (QFFs), a complete set of fundamental vibrational frequencies, rotational constants, and rovibrational coupling and centrifugal distortion constants have been determined for both the cyclic 1(sup 1) 1A' and bent 2(sup 1)A' DCCN, H(C13)CCN, HC(C-13)N, and HCC(N-15) isotopologues of HCCN. Spectroscopic constants are computed for all isotopologues using second-order vibrational perturbation theory (VPT2), and the fundamental vibrational frequencies are computed with VPT2 and vibrational configuration interaction (VCI) theory. Agreement between VPT2 and VCI results is quite good with the fundamental vibrational frequencies of the bent isomer isotopologues in accord to within a 0.1 to 3.2 / cm range. Similar accuracies are present for the cyclic isomer isotopologues. The data generated here serve as a reference for astronomical observations of these closed-shell, highly-dipolar molecules using new, high-resolution telescopes and as reference for laboratory studies where isotopic labeling may lead to elucidation of the formation mechanism for the known interstellar molecule: X 3A0 HCCN.

  5. Using frequency response functions to manage image degradation from equipment vibration in the Daniel K. Inouye Solar Telescope

    NASA Astrophysics Data System (ADS)

    McBride, William R.; McBride, Daniel R.

    2016-08-01

    The Daniel K Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, providing a significant increase in the resolution of solar data available to the scientific community. Vibration mitigation is critical in long focal-length telescopes such as the Inouye Solar Telescope, especially when adaptive optics are employed to correct for atmospheric seeing. For this reason, a vibration error budget has been implemented. Initially, the FRFs for the various mounting points of ancillary equipment were estimated using the finite element analysis (FEA) of the telescope structures. FEA analysis is well documented and understood; the focus of this paper is on the methods involved in estimating a set of experimental (measured) transfer functions of the as-built telescope structure for the purpose of vibration management. Techniques to measure low-frequency single-input-single-output (SISO) frequency response functions (FRF) between vibration source locations and image motion on the focal plane are described. The measurement equipment includes an instrumented inertial-mass shaker capable of operation down to 4 Hz along with seismic accelerometers. The measurement of vibration at frequencies below 10 Hz with good signal-to-noise ratio (SNR) requires several noise reduction techniques including high-performance windows, noise-averaging, tracking filters, and spectral estimation. These signal-processing techniques are described in detail.

  6. Low Intensity, High Frequency Vibration Training to Improve Musculoskeletal Function in a Mouse Model of Duchenne Muscular Dystrophy

    PubMed Central

    Novotny, Susan A.; Mader, Tara L.; Greising, Angela G.; Lin, Angela S.; Guldberg, Robert E.; Warren, Gordon L.; Lowe, Dawn A.

    2014-01-01

    The objective of the study was to determine if low intensity, high frequency vibration training impacted the musculoskeletal system in a mouse model of Duchenne muscular dystrophy, relative to healthy mice. Three-week old wildtype (n = 26) and mdx mice (n = 22) were randomized to non-vibrated or vibrated (45 Hz and 0.6 g, 15 min/d, 5 d/wk) groups. In vivo and ex vivo contractile function of the anterior crural and extensor digitorum longus muscles, respectively, were assessed following 8 wks of vibration. Mdx mice were injected 5 and 1 days prior to sacrifice with Calcein and Xylenol, respectively. Muscles were prepared for histological and triglyceride analyses and subcutaneous and visceral fat pads were excised and weighed. Tibial bones were dissected and analyzed by micro-computed tomography for trabecular morphometry at the metaphysis, and cortical geometry and density at the mid-diaphysis. Three-point bending tests were used to assess cortical bone mechanical properties and a subset of tibiae was processed for dynamic histomorphometry. Vibration training for 8 wks did not alter trabecular morphometry, dynamic histomorphometry, cortical geometry, or mechanical properties (P≥0.34). Vibration did not alter any measure of muscle contractile function (P≥0.12); however the preservation of muscle function and morphology in mdx mice indicates vibration is not deleterious to muscle lacking dystrophin. Vibrated mice had smaller subcutaneous fat pads (P = 0.03) and higher intramuscular triglyceride concentrations (P = 0.03). These data suggest that vibration training at 45 Hz and 0.6 g did not significantly impact the tibial bone and the surrounding musculature, but may influence fat distribution in mice. PMID:25121503

  7. Low intensity, high frequency vibration training to improve musculoskeletal function in a mouse model of Duchenne muscular dystrophy.

    PubMed

    Novotny, Susan A; Mader, Tara L; Greising, Angela G; Lin, Angela S; Guldberg, Robert E; Warren, Gordon L; Lowe, Dawn A

    2014-01-01

    The objective of the study was to determine if low intensity, high frequency vibration training impacted the musculoskeletal system in a mouse model of Duchenne muscular dystrophy, relative to healthy mice. Three-week old wildtype (n = 26) and mdx mice (n = 22) were randomized to non-vibrated or vibrated (45 Hz and 0.6 g, 15 min/d, 5 d/wk) groups. In vivo and ex vivo contractile function of the anterior crural and extensor digitorum longus muscles, respectively, were assessed following 8 wks of vibration. Mdx mice were injected 5 and 1 days prior to sacrifice with Calcein and Xylenol, respectively. Muscles were prepared for histological and triglyceride analyses and subcutaneous and visceral fat pads were excised and weighed. Tibial bones were dissected and analyzed by micro-computed tomography for trabecular morphometry at the metaphysis, and cortical geometry and density at the mid-diaphysis. Three-point bending tests were used to assess cortical bone mechanical properties and a subset of tibiae was processed for dynamic histomorphometry. Vibration training for 8 wks did not alter trabecular morphometry, dynamic histomorphometry, cortical geometry, or mechanical properties (P ≥ 0.34). Vibration did not alter any measure of muscle contractile function (P ≥ 0.12); however the preservation of muscle function and morphology in mdx mice indicates vibration is not deleterious to muscle lacking dystrophin. Vibrated mice had smaller subcutaneous fat pads (P = 0.03) and higher intramuscular triglyceride concentrations (P = 0.03). These data suggest that vibration training at 45 Hz and 0.6 g did not significantly impact the tibial bone and the surrounding musculature, but may influence fat distribution in mice.

  8. Evaluation of range-separated hybrid density functionals for the prediction of vibrational frequencies, infrared intensities, and Raman activities†

    PubMed Central

    Jiménez-Hoyos, Carlos A.; Janesko, Benjamin G.

    2016-01-01

    We present an assessment of different density functionals, with emphasis on range-separated hybrids, for the prediction of fundamental and harmonic vibrational frequencies, infrared intensities, and Raman activities. Additionally, we discuss the basis set convergence of vibrational properties of H2O with long-range corrected hybrids. Our results show that B3LYP is the best functional for predicting vibrational frequencies (both fundamental and harmonic); the screened-PBE hybrid (HSE) density functional works best for infrared intensities, and the long-range corrected PBE (LC-ωPBE), M06-HF, and M06-L density functionals are almost as good as MP2 for predicting Raman activities. We show the predicted Raman spectrum of adenine as an example of a medium-size molecule where a DFT/Sadlej pVTZ calculation is affordable and compare our results against the experimental spectrum. PMID:18989473

  9. Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation

    NASA Astrophysics Data System (ADS)

    Lipovsky, Bradley P.; Dunham, Eric M.

    2015-02-01

    Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis, valid at wavelengths greater than the fracture aperture, that accounts for quasi-static elastic deformation of the fracture walls, as well as fluid viscosity, inertia, and compressibility. In the long-wavelength limit, anomalously dispersed guided waves known as crack or Krauklis waves propagate with restoring force from fracture wall elasticity. At shorter wavelengths, the waves become sound waves within the fluid channel. Wave attenuation in our model is due to fluid viscosity, rather than seismic radiation from crack tips or fracture wall roughness. We characterize viscous damping at both low frequencies, where the flow is always fully developed, and at high frequencies, where the flow has a nearly constant velocity profile away from viscous boundary layers near the fracture walls. Most observable seismic signals from resonating fractures likely arise in the boundary layer crack wave limit, where fluid-solid coupling is pronounced and attenuation is minimal. We present a method to estimate the aperture and length of a resonating hydraulic fracture using both the seismically observed quality factor and characteristic frequency. Finally, we develop scaling relations between seismic moment and characteristic frequency that might be useful when interpreting the statistics of hydraulic fracture events.

  10. Fin Whale Sound Reception Mechanisms: Skull Vibration Enables Low-Frequency Hearing

    PubMed Central

    Cranford, Ted W.; Krysl, Petr

    2015-01-01

    Hearing mechanisms in baleen whales (Mysticeti) are essentially unknown but their vocalization frequencies overlap with anthropogenic sound sources. Synthetic audiograms were generated for a fin whale by applying finite element modeling tools to X-ray computed tomography (CT) scans. We CT scanned the head of a small fin whale (Balaenoptera physalus) in a scanner designed for solid-fuel rocket motors. Our computer (finite element) modeling toolkit allowed us to visualize what occurs when sounds interact with the anatomic geometry of the whale’s head. Simulations reveal two mechanisms that excite both bony ear complexes, (1) the skull-vibration enabled bone conduction mechanism and (2) a pressure mechanism transmitted through soft tissues. Bone conduction is the predominant mechanism. The mass density of the bony ear complexes and their firmly embedded attachments to the skull are universal across the Mysticeti, suggesting that sound reception mechanisms are similar in all baleen whales. Interactions between incident sound waves and the skull cause deformations that induce motion in each bony ear complex, resulting in best hearing sensitivity for low-frequency sounds. This predominant low-frequency sensitivity has significant implications for assessing mysticete exposure levels to anthropogenic sounds. The din of man-made ocean noise has increased steadily over the past half century. Our results provide valuable data for U.S. regulatory agencies and concerned large-scale industrial users of the ocean environment. This study transforms our understanding of baleen whale hearing and provides a means to predict auditory sensitivity across a broad spectrum of sound frequencies. PMID:25633412

  11. Fin whale sound reception mechanisms: skull vibration enables low-frequency hearing.

    PubMed

    Cranford, Ted W; Krysl, Petr

    2015-01-01

    Hearing mechanisms in baleen whales (Mysticeti) are essentially unknown but their vocalization frequencies overlap with anthropogenic sound sources. Synthetic audiograms were generated for a fin whale by applying finite element modeling tools to X-ray computed tomography (CT) scans. We CT scanned the head of a small fin whale (Balaenoptera physalus) in a scanner designed for solid-fuel rocket motors. Our computer (finite element) modeling toolkit allowed us to visualize what occurs when sounds interact with the anatomic geometry of the whale's head. Simulations reveal two mechanisms that excite both bony ear complexes, (1) the skull-vibration enabled bone conduction mechanism and (2) a pressure mechanism transmitted through soft tissues. Bone conduction is the predominant mechanism. The mass density of the bony ear complexes and their firmly embedded attachments to the skull are universal across the Mysticeti, suggesting that sound reception mechanisms are similar in all baleen whales. Interactions between incident sound waves and the skull cause deformations that induce motion in each bony ear complex, resulting in best hearing sensitivity for low-frequency sounds. This predominant low-frequency sensitivity has significant implications for assessing mysticete exposure levels to anthropogenic sounds. The din of man-made ocean noise has increased steadily over the past half century. Our results provide valuable data for U.S. regulatory agencies and concerned large-scale industrial users of the ocean environment. This study transforms our understanding of baleen whale hearing and provides a means to predict auditory sensitivity across a broad spectrum of sound frequencies.

  12. VIBRATION COMPACTION

    DOEpatents

    Hauth, J.J.

    1962-07-01

    A method of compacting a powder in a metal container is described including the steps of vibrating the container at above and below the resonant frequency and also sweeping the frequency of vibration across the resonant frequency several times thereby following the change in resonant frequency caused by compaction of the powder. (AEC)

  13. Vibrational sum-frequency spectroscopy for trace chemical detection on surfaces at stand-off distances.

    PubMed

    Asher, William E; Willard-Schmoe, Ella

    2013-03-01

    Vibrational sum-frequency spectroscopy (VSFS) has been used for some time as a laboratory-based surface chemical analytical tool. Here, theoretical considerations in applying the method as a remote-sensing probe for detecting trace levels of chemicals adsorbed on surfaces are presented. Additionally, a VSFS instrument is configured to operate at a stand-off distance of 2.2 m using near-nadir incidence angles. This system was used to measure VSFS spectra for films of pure 1-amino-4-nitrobenzene (p-nitroaniline, PNA) and pure 2-hydroxy-1,3,5-trinitrobenzene (picric acid, PA) adsorbed on polished T-6061 aluminum alloy. These spectra are used to investigate the effect of optical polarization on the sum-frequency response of these compounds at nadir optical geometries. Detection limits for each compound are also estimated and found to be 0.51 μg cm(2) for PNA and 0.89 μg cm(2) for PA. The implications of these results regarding remote sensing applications of VSFS are discussed.

  14. The thermal effects on high-frequency vibration of beams using energy flow analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Wenbo; Chen, Hualing; Zhu, Danhui; Kong, Xiangjie

    2014-04-01

    In this paper, the energy flow analysis (EFA) method is developed to predict the high-frequency response of beams in a thermal environment, which is a topic of concern in aerospace and automotive industries. The temperature load applied on the structures can generate thermal stresses and change material properties. The wavenumber and group velocity associated with the in-plane axial force arising from thermal stresses are included in the derivation of the governing energy equation, and the input power is obtained from the derived effective bending stiffness. In addition, effect of temperature-dependent material properties is considered in the EFA model. To verify the proposed formulation, numerical simulations are performed for a pinned-pinned beam in a uniform thermal environment. The EFA results are compared with the modal solutions for various frequencies and damping loss factors, and good correlations are observed. The results show that the spatial distributions and levels of energy density can be affected by the thermal effects, and the vibration response of beams increases with temperature.

  15. Efficient procedure for the numerical calculation of harmonic vibrational frequencies based on internal coordinates.

    PubMed

    Miliordos, Evangelos; Xantheas, Sotiris S

    2013-08-15

    We propose a general procedure for the numerical calculation of the harmonic vibrational frequencies that is based on internal coordinates and Wilson's GF methodology via double differentiation of the energy. The internal coordinates are defined as the geometrical parameters of a Z-matrix structure, thus avoiding issues related to their redundancy. Linear arrangements of atoms are described using a dummy atom of infinite mass. The procedure has been automated in FORTRAN90 and its main advantage lies in the nontrivial reduction of the number of single-point energy calculations needed for the construction of the Hessian matrix when compared to the corresponding number using double differentiation in Cartesian coordinates. For molecules of C1 symmetry the computational savings in the energy calculations amount to 36N - 30, where N is the number of atoms, with additional savings when symmetry is present. Typical applications for small and medium size molecules in their minimum and transition state geometries as well as hydrogen bonded clusters (water dimer and trimer) are presented. In all cases the frequencies based on internal coordinates differ on average by <1 cm(-1) from those obtained from Cartesian coordinates.

  16. Phospholipid monolayers probed by vibrational sum frequency spectroscopy: instability of unsaturated phospholipids.

    PubMed

    Liljeblad, Jonathan F D; Bulone, Vincent; Tyrode, Eric; Rutland, Mark W; Johnson, C Magnus

    2010-05-19

    The surface specific technique vibrational sum frequency spectroscopy has been applied to in situ studies of the degradation of Langmuir monolayers of 1,2-diacyl-phosphocholines with various degrees of unsaturation in the aliphatic chains. To monitor the degradation of the phospholipids, the time-dependent change of the monolayer area at constant surface pressure and the sum frequency intensity of the vinyl CH stretch at the carbon-carbon double bonds were measured. The data show a rapid degradation of monolayers of phospholipids carrying unsaturated aliphatic chains compared to the stable lipids carrying fully saturated chains when exposed to the ambient laboratory air. In addition, the degradation of the phospholipids can be inhibited by purging the ambient air with nitrogen. This instability may be attributed to spontaneous degradation by oxidation mediated by various reactive species in the air. To further elucidate the process of lipid oxidation in biological membranes artificial Langmuir monolayers probed by a surface specific spectroscopic technique as in this study can serve as a model system for studying the degradation/oxidation of cell membrane constituents.

  17. Efficient Procedure for the Numerical Calculation of Harmonic Vibrational Frequencies Based on Internal Coordinates

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2013-08-15

    We propose a general procedure for the numerical calculation of the harmonic vibrational frequencies that is based on internal coordinates and Wilson’s GF methodology via double differentiation of the energy. The internal coordinates are defined as the geometrical parameters of a Z-matrix structure, thus avoiding issues related to their redundancy. Linear arrangements of atoms are described using a dummy atom of infinite mass. The procedure has been automated in FORTRAN90 and its main advantage lies in the nontrivial reduction of the number of single-point energy calculations needed for the construction of the Hessian matrix when compared to the corresponding number using double differentiation in Cartesian coordinates. For molecules of C1 symmetry the computational savings in the energy calculations amount to 36N – 30, where N is the number of atoms, with additional savings when symmetry is present. Typical applications for small and medium size molecules in their minimum and transition state geometries as well as hydrogen bonded clusters (water dimer and trimer) are presented. Finally, in all cases the frequencies based on internal coordinates differ on average by <1 cm–1 from those obtained from Cartesian coordinates.

  18. Prediction of high-frequency vibration transmission across coupled, periodic ribbed plates by incorporating tunneling mechanisms.

    PubMed

    Yin, Jianfei; Hopkins, Carl

    2013-04-01

    Prediction of structure-borne sound transmission on built-up structures at audio frequencies is well-suited to Statistical Energy Analysis (SEA) although the inclusion of periodic ribbed plates presents challenges. This paper considers an approach using Advanced SEA (ASEA) that can incorporate tunneling mechanisms within a statistical approach. The coupled plates used for the investigation form an L-junction comprising a periodic ribbed plate with symmetric ribs and an isotropic homogeneous plate. Experimental SEA (ESEA) is carried out with input data from Finite Element Methods (FEM). This indicates that indirect coupling is significant at high frequencies where bays on the periodic ribbed plate can be treated as individual subsystems. SEA using coupling loss factors from wave theory leads to significant underestimates in the energy of the bays when the isotropic homogeneous plate is excited. This is due to the absence of tunneling mechanisms in the SEA model. In contrast, ASEA shows close agreement with FEM and laboratory measurements. The errors incurred with SEA rapidly increase as the bays become more distant from the source subsystem. ASEA provides significantly more accurate predictions by accounting for the spatial filtering that leads to non-diffuse vibration fields on these more distant bays.

  19. Application of image analysis and time-frequency analysis for tracking the rotating blades vibration

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Ting; Hsiung, Wan-Ying; Yang, Yuan-Shen; Loh, Chin-Hsiung

    2014-03-01

    The objective of this paper is to investigate the application of the photogrammetric approach to measuring the vibration of a research-scale wind turbine blade model (both damage and undamaged blade). In order to control the excitation (rotation of the wind turbine blade), a motor was used to spin the blades at controlled angular velocities. Two cameras are set in front of the turbine to tape the video images. Through a sequence of stereo image pairs acquired by high speed camera, the images are studied. The camera we used is the BASLER acA2000-340km (2048x1088, 340FPS). Before taking the photos camera calibration was conducted which include lens distortion and skew factor is examined. To analyze the displacement of the motion target on the turbine blade, after loading the 3D calibration, the 3D positions are calculated by using a stereo triangulation technique. Then the displacement fields by image template matching can be calculated. Application of the technique to track the 3D motion of the rotating wind turbine blade is demonstrated by using data from the research-scale wind turbine. Different from the image processing technique data from the contact sensors (accelerometers) is also used. Through Rodrigues' rotation formula to remove the rotation frequency it is easy to extract the out-of-plane motion of the blade, from which the model frequency of the blade can be identified.

  20. DFT calculation of vibrational frequencies of clusters in GaAs and the Raman spectra

    NASA Astrophysics Data System (ADS)

    Radhika Devi, V.; Shrivastava, Keshav N.

    2012-09-01

    We have calculated the vibrational frequencies of clusters of Ga and As atoms from the first principles using the density-functional theory (DFT) method and the local-density approximation (LDA). We find that the calculated value of 286.2 cm-1 for a linear cluster of Ga2As2 is very near the experimental value of 292 ± 4 cm-1. The calculated value of 289.4 cm-1 for Ga2As6 (dumb bell) cluster is indeed very near the experimental value. There are strong phonon correlations so that the cluster frequency is within the dispersion relation of the crystal LO value. There is a weak line in the experimental Raman spectrum at 268 cm-1 which is very near the value of 267.3 cm-1 calculated for the Ga2As (triangular) cluster. The weak lines corresponding to the linear bonds provide the strength to the amorphous samples. There are clusters of atoms in the glassy state of GaAs.

  1. High-Frequency Vibration of the Organ of Corti in Vitro

    NASA Astrophysics Data System (ADS)

    Scherer, M. P.; Nowotny, M.; Dalhoff, E.; Zenner, H.-P.; Gummer, A. W.

    2003-02-01

    The mechanism by which the electromechanical force generated by the outer hair cells (OHC) produces the exquisite sensitivity, frequency selectivity and dynamic range of the cochlea is unknown. To address this question, we measured the electrically induced radial vibration pattern at different levels within the organ of Corti of the guinea pig. Two in vitro preparations were used: 1) a half turn including modiolar bone and cochlear partition, without tectorial membrane (TM); the basilar membrane (BM) was supported from its tympanal side. 2) A temporal bone preparation, where the bony wall was removed above and below the measurement location to permit introduction of electrodes. In the latter case, the cochlear partition was in its normal mechanical environment, with free swinging BM and with TM. Velocity of BM, reticular lamina (RL), and upper and lower sides of the TM in response to broadband electrical stimulation of the OHCs was measured with a laser Doppler vibrometer. The interferometer was sensitive enough to permit measurement without reflective beads or the like. The frequency range of the stimulation was 480 Hz - 70 kHz. Displacement amplitudes were constant up to 10 kHz, after which they dropped with -14 to -17 dB/oct. Moving across the RL in the radial direction, phase reversals characteristic of pivoting points occurred above the pillar cells and the outer tunnel. No phase reversals were observed on the BM and TM.

  2. A Frequency Model of Vibrational Processes in Gas-Turbine Drives of Compressor Stations of Main Gas Pipelines

    NASA Astrophysics Data System (ADS)

    Chekardovskiy, M. N.; Chekardovskiy, S. M.; Razboynikov, A. A.; Ponomareva, T. G.

    2016-10-01

    At compressor stations, systematic measurements of noise and vibration of power equipment - gas compressor units - are carried out. The article presents basic equations for calculating natural and forced frequencies at which the main defects appear. According to the studied dependences, results of calculations are obtained on the following types of drives for gas-compressor units GTK-10-4, Avon-1534, DG-90.

  3. Strong frequency dependence of vibrational relaxation in bulk and surface water reveals sub-picosecond structural heterogeneity

    PubMed Central

    van der Post, Sietse T.; Hsieh, Cho-Shuen; Okuno, Masanari; Nagata, Yuki; Bakker, Huib J.; Bonn, Mischa; Hunger, Johannes

    2015-01-01

    Because of strong hydrogen bonding in liquid water, intermolecular interactions between water molecules are highly delocalized. Previous two-dimensional infrared spectroscopy experiments have indicated that this delocalization smears out the structural heterogeneity of neat H2O. Here we report on a systematic investigation of the ultrafast vibrational relaxation of bulk and interfacial water using time-resolved infrared and sum-frequency generation spectroscopies. These experiments reveal a remarkably strong dependence of the vibrational relaxation time on the frequency of the OH stretching vibration of liquid water in the bulk and at the air/water interface. For bulk water, the vibrational relaxation time increases continuously from 250 to 550 fs when the frequency is increased from 3,100 to 3,700 cm−1. For hydrogen-bonded water at the air/water interface, the frequency dependence is even stronger. These results directly demonstrate that liquid water possesses substantial structural heterogeneity, both in the bulk and at the surface. PMID:26382651

  4. Calculation and analysis of the harmonic vibrational frequencies in molecules at extreme pressure: methodology and diborane as a test case.

    PubMed

    Cammi, R; Cappelli, C; Mennucci, B; Tomasi, J

    2012-10-21

    We present a new quantum chemical method for the calculation of the equilibrium geometry and the harmonic vibrational frequencies of molecular systems in dense medium at high pressures (of the order of GPa). The new computational method, named PCM-XP, is based on the polarizable continuum model (PCM), amply used for the study of the solvent effects at standard condition of pressure, and it is accompanied by a new method of analysis for the interpretation of the mechanisms underpinning the effects of pressure on the molecular geometries and the harmonic vibrational frequencies. The PCM-XP has been applied at the density functional theory level to diborane as a molecular system under high pressure. The computed harmonic vibrational frequencies as a function of the pressure have shown a satisfactory agreement with the corresponding experimental results, and the parallel application of the method of analysis has reveled that the effects of the pressure on the equilibrium geometry can be interpreted in terms of direct effects on the electronic charge distribution of the molecular solutes, and that the effects on the harmonic vibrational frequencies can be described in terms of two physically distinct effects of the pressure (curvature and relaxation) on the potential energy for the motion of the nuclei.

  5. [Influence of low-frequency magnetotherapy and HF-puncture on the heart rhythm in hypertensive workers exposed to vibration].

    PubMed

    Drobyshev, V A; Loseva, M I; Sukharevskaia, T M; Michurin, A I

    2001-01-01

    The authors present results concerning use of low-frequency magnetic fields and HF-therapy for correction of vegetative homeostasis in workers with variable length of service, exposed to vibration, having early forms of arterial hypertension. The most positive changes of vegetative status and central hemodynamics are seen in workers with low length of service.

  6. Hydrogenation of the alpha,beta-Unsaturated Aldehydes Acrolein, Crotonaldehyde, and Prenal over Pt Single Crystals: A Kinetic and Sum-Frequency Generation Vibrational Spectroscopy Study

    SciTech Connect

    Kliewer, C.J.; Somorjai, G.A.

    2008-11-26

    Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three {alpha},{beta}-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr aldehyde, 100 Torr hydrogen) in the temperature range of 295K to 415K. SFG-VS data showed that acrolein has mixed adsorption species of {eta}{sub 2}-di-{sigma}(CC)-trans, {eta}{sub 2}-di-{sigma}(CC)-cis as well as highly coordinated {eta}{sub 3} or {eta}{sub 4} species. Crotonaldehyde adsorbed to Pt(111) as {eta}{sub 2} surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the {eta}{sub 2} adsorption species, and became more highly coordinated as the temperature was raised to 415K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation 'cracking' product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotylalcohol.

  7. Interfacial Processes in Model Lithium Ion Systems Probed with Vibrational Sum Frequency Generation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Nicolau, Bruno G.; Garcia Rey, Natalia; Dlott, Dana

    2014-06-01

    Vibrational sum frequency generation (SFG) spectroscopy was used to probe electrochemical processes taking place at the interface between metal anodes and the liquid phase in model lithium ion systems. Lithium ion batteries have been extensively studied and characterized by numerous techniques. However, the mechanisms behind many properties are still unclear due to the lack of techniques that can directly probe them in situ. The formation of the electrode passivating layer known as solid-electrolyte interphase (SEI) is one such example. During the first charging cycle of a battery, some of the electrolyte undergoes reduction at the electrode surface forming an electrically isolating barrier that prevents the subsequent reduction of more electrolyte molecules. The SFG selection rules suppress signals from molecules in centrosymmetric environments such as electrolyte layers, so SFG is a selective probe of interfacial environments such as the SEI. In this study, ethylene carbonate's (EC) response to potential cycling was observed. EC is commonly used as a high permittivity solvent in batteries and is widely believed to be the main component of the SEI in its reduced form, lithium ethylene dicarbonyl. EC's carbonyl stretch (1850 cm-1) was measured in conjunction with cyclic voltammetry experiments. The SFG intensity showed remarkable agreement with the changing potential, as seen in the figure below. The shoulders on each side of the peaks in (a) are especially interesting, as they correspond to the potentials where lithium metal is oxidized and reduced. Vibrational modes found at 1300-1400 cm-1, usually assigned to the reduced form of EC, are also being studied in order to provide more information on the nature of the SEI.

  8. Dictums for problem solving and approximation in mathematical acoustics: examples involving low-frequency vibration and radiation.

    PubMed

    Pierce, Allan D; Thiam, Amadou G

    2012-03-01

    A sequence of dictums for mathematical acoustics is given representing opinions intended to be regarded as authoritative, but not necessarily universally agreed upon. The dictums are presented in the context of the detailed solution for a class of problems involving the forced vibration of a long cylinder protruding half-way into a half-space bounded by a compliant surface (impedance boundary) characterized by a spring constant. One limiting case corresponds to a cylinder vibrating within an infinite rigid baffle, and another limiting case corresponds to a vibrating cylinder on the compliant surface of an incompressible fluid. The second limiting case is identified as analogous to that of a floating half-submerged cylinder whose vibrations cause water waves to propagate over the surface. Attention is focused on vibrations at very low frequencies. Difficulties with insuring a causal solution are pointed out and dictums are given as to how one overcomes such difficulties. Various approximation techniques are described. The derivations involve application of the theory of complex variables and the method of matched asymptotic expansions, and the results include the apparent entrained mass in the near field of the cylinder and the radiation resistance per unit length experienced by the vibrating cylinder.

  9. Solvent-induced infrared frequency shifts in aromatic nitriles are quantitatively described by the vibrational Stark effect.

    PubMed

    Levinson, Nicholas M; Fried, Stephen D; Boxer, Steven G

    2012-09-06

    The physical properties of solvents strongly affect the spectra of dissolved solutes, and this phenomenon can be exploited to gain insight into the solvent-solute interaction. The large solvatochromic shifts observed for many dye molecules in polar solvents are due to variations in the solvent reaction field, and these shifts are widely used to estimate the change in the dye's dipole moment upon photoexcitation, which is typically on the order of ∼1-10 D. In contrast, the change in dipole moment for vibrational transitions is approximately 2 orders of magnitude smaller. Nonetheless, vibrational chromophores display significant solvatochromism, and the relative contributions of specific chemical interactions and electrostatic interactions are debated, complicating the interpretation of vibrational frequency shifts in complex systems such as proteins. Here we present a series of substituted benzonitriles that display widely varying degrees of vibrational solvatochromism. In most cases, this variation can be quantitatively described by the experimentally determined Stark tuning rate, coupled with a simple Onsager-like model of solvation, reinforcing the view that vibrational frequency shifts are largely caused by electrostatic interactions. In addition, we discuss specific cases where continuum solvation models fail to predict solvatochromic shifts, revealing the necessity for more advanced theoretical models that capture local aspects of solute-solvent interactions.

  10. A mixed space-time and wavenumber-frequency domain procedure for modelling ground vibration from surface railway tracks

    NASA Astrophysics Data System (ADS)

    Koroma, S. G.; Thompson, D. J.; Hussein, M. F. M.; Ntotsios, E.

    2017-07-01

    This paper presents a methodology for studying ground vibration in which the railway track is modelled in the space-time domain using the finite element method (FEM) and, for faster computation, discretisation of the ground using either FEM or the boundary element method (BEM) is avoided by modelling it in the wavenumber-frequency domain. The railway track is coupled to the ground through a series of rectangular strips located at the surface of the ground; their vertical interaction is described by a frequency-dependent dynamic stiffness matrix whose elements are represented by discrete lumped parameter models. The effectiveness of this approach is assessed firstly through frequency domain analysis using as excitation a stationary harmonic load applied on the rail. The interaction forces at the ballast/ground interface are calculated using the FE track model in the space-time domain, transformed to the wavenumber domain, and used as input to the ground model for calculating vibration in the free field. Additionally, time domain simulations are also performed with the inclusion of nonlinear track parameters. Results are presented for the coupled track/ground model in terms of time histories and frequency spectra for the track vibration, interaction forces and free-field ground vibration. For the linear track model, the results from the mixed formulation are in excellent agreement with those from a semi-analytical model formulated in the wavenumber-frequency domain, particularly in the vicinity of the loading point. The accuracy of the mixed formulation away from the excitation point depends strongly on the inclusion of through-ground coupling in the lumped parameter model, which has been found to be necessary for both track dynamics and ground vibration predictions.

  11. Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters

    SciTech Connect

    Sharpes, Nathan; Abdelkefi, Abdessattar; Priya, Shashank

    2015-08-31

    Vibration-based energy harvesters using piezoelectric materials have long made use of the cantilever beam structure. Surmounting the deficiencies in one-dimensional cantilever-based energy harvesters has been a major focus in the literature. In this work, we demonstrate a strategy of using two-dimensional beam shapes to harvest energy from low frequency excitations. A characteristic Zigzag-shaped beam is created to compare against the two proposed two-dimensional beam shapes, all of which occupy a 25.4 × 25.4 mm{sup 2} area. In addition to maintaining the low-resonance bending frequency, the proposed beam shapes are designed with the goal of realizing a concentrated stress structure, whereby stress in the beam is concentrated in a single area where a piezoelectric layer may be placed, rather than being distributed throughout the beam. It is shown analytically, numerically, and experimentally that one of the proposed harvesters is able to provide significant increase in power production, when the base acceleration is set equal to 0.1 g, with only a minimal change in the resonant frequency compared to the current state-of-the-art Zigzag shape. This is accomplished by eliminating torsional effects, producing a more pure bending motion that is necessary for high electromechanical coupling. In addition, the proposed harvesters have a large effective beam tip whereby large tip mass may be placed while retaining a low-profile, resulting in a low volume harvester and subsequently large power density.

  12. [The effect of betahistine on histological changes in rabbit brain in model of whole body wide-frequency vibration].

    PubMed

    Shimkus, Iu Iu; Sapegin, I D

    2013-01-01

    In acute experiments in conscious rabbits was studied protective action of selective blocker of histamine H3-receptor betahistine (2mg/kg i/v) against histological changes in precentral and postcentral gyrus, as well as in temporal lobe of cerebral cortex, thalamus, hypothalamus, and cerebellum, arising in case of modeling of whole body wide-frequency vibration. Betahistine attenuates edematous and degenerative changes in neurons and reciprocal glial reaction, caused by vibration, but does not eliminate edema in perivascular spaces. This effect may be related to the improvement of blood supply as a result of of vasodilatory action and decrease of oxygen consumption via vestibuloprotective effect.

  13. Time-frequency analysis of nonstationary vibration signals for deployable structures by using the constant-Q nonstationary gabor transform

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Yan, Shaoze; Zhang, Wei

    2016-06-01

    Deployable structures have been widely used in on-orbit servicing spacecrafts, and the vibration properties of such structures have become increasingly important in the aerospace industry. The constant-Q nonstationary Gabor transform (CQ-NSGT) is introduced in this paper to accurately evaluate the variation in the frequency and amplitude of vibration signals along with time. First, an example signal is constructed on the basis of the vibration properties of deployable structures and is processed by the short-time Fourier transform, Wigner-Ville distribution, Hilbert-Huang transform, and CQ-NSGT. Results show that time and frequency resolutions are simultaneously fine only by employing CQ-NSGT. Subsequently, a zero padding operation is conducted to correct the calculation error at the end of the transform results. Finally, a set of experimental devices is constructed. The vibration signal of the experimental mode is processed by CQ-NSGT. On this basis, the experimental signal properties are discussed. This time-frequency method may be useful for formulating the dynamics for complex deployable structures.

  14. Highly Accurate Quartic Force Fields, Vibrational Frequencies, and Spectroscopic Constants for Cyclic and Linear C3H3(+)

    NASA Technical Reports Server (NTRS)

    Huang, Xinchuan; Taylor, Peter R.; Lee, Timothy J.

    2011-01-01

    High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C H + molecular cation, referred to as c-C H + and I-C H +. Specifically the 33 3333 singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants using both vibrational 2nd-order perturbation theory and variational methods to solve the nuclear Schroedinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C H +, 33 obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C H + 33 and I-C H + are the most reliable available for the free gas-phase species and it is hoped that 33 these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations.

  15. Ocular vestibular evoked myogenic potentials to vertex low frequency vibration as a diagnostic test for superior canal dehiscence.

    PubMed

    Verrecchia, Luca; Westin, Magnus; Duan, Maoli; Brantberg, Krister

    2016-04-01

    To explore ocular vestibular evoked myogenic potentials (oVEMP) to low-frequency vertex vibration (125 Hz) as a diagnostic test for superior canal dehiscence (SCD) syndrome. The oVEMP using 125 Hz single cycle bone-conducted vertex vibration were tested in 15 patients with unilateral superior canal dehiscence (SCD) syndrome, 15 healthy controls and in 20 patients with unilateral vestibular loss due to vestibular neuritis. Amplitude, amplitude asymmetry ratio, latency and interaural latency difference were parameters of interest. The oVEMP amplitude was significantly larger in SCD patients when affected sides (53 μVolts) were compared to non-affected (17.2 μVolts) or compared to healthy controls (13.6 μVolts). Amplitude larger than 33.8 μVolts separates effectively the SCD ears from the healthy ones with sensitivity of 87% and specificity of 93%. The other three parameters showed an overlap between affected SCD ears and non-affected as well as between SCD ears and those in the two control groups. oVEMP amplitude distinguishes SCD ears from healthy ones using low-frequency vibration stimuli at vertex. Amplitude analysis of oVEMP evoked by low-frequency vertex bone vibration stimulation is an additional indicator of SCD syndrome and might serve for diagnosing SCD patients with coexistent conductive middle ear problems. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  16. Spectroscopic characterization and constitutional and rotational isomerism of ClC(O)SCN and ClC(O)NCS.

    PubMed

    Ramos, Luis A; Ulic, Sonia E; Romano, Rosana M; Erben, Mauricio F; Vishnevskiy, Yury V; Reuter, Christian G; Mitzel, Norbert W; Beckers, Helmut; Willner, Helge; Zeng, Xiaoqing; Bernhardt, Eduard; Ge, Maofa; Tong, ShengRui; Della Védova, Carlos O

    2013-03-21

    Chlorocarbonylthio- and isothiocyanate (ClC(O)SCN and ClC(O)NCS) have been isolated and characterized by IR (Ar matrix, gas), Raman (liquid), (13)C NMR and UV-visible spectroscopies. Vibrational and quantum chemical studies suggest the presence of the syn and anti conformers (SCN group with respect to the C═O bond) in the gas phase for both constitutional isomers. syn-ClC(O)SCN is preferred by ΔH° (anti/syn) = 1.3(0.3) kcal mol(-1). The solid-state structure of ClC(O)SCN has been determined by single crystal X-ray diffraction analysis at low temperature. The crystalline solid consists exclusively of molecules in the syn conformation. On the other hand, the anti form is more stable for the ClC(O)NCS isomer. The structure of ClC(O)NCS and its conformational composition were determined by gas electron diffraction. An unusual low syn → anti interconversion energy barrier of 0.98 (0.15) kcal mol(-1) was detected for ClC(O)NCS at cryogenic temperatures. The photochemistry of both constitutional isomers isolated in solid argon at 15 K was studied. Rearrangement of ClC(O)SCN to ClC(O)NCS was observed in the neat liquid and under UV-vis irradiation of ClC(O)SCN isolated in solid argon. Properties have been discussed in terms of the valence electronic structure, including the analysis of the He(I) photoelectron spectrum of ClC(O)SCN.

  17. A hybrid single-end-access MZI and Φ-OTDR vibration sensing system with high frequency response

    NASA Astrophysics Data System (ADS)

    Zhang, Yixin; Xia, Lan; Cao, Chunqi; Sun, Zhenhong; Li, Yanting; Zhang, Xuping

    2017-01-01

    A hybrid single-end-access Mach-Zehnder interferometer (MZI) and phase sensitive OTDR (Φ-OTDR) vibration sensing system is proposed and demonstrated experimentally. In our system, the narrow optical pulses and the continuous wave are injected into the fiber through the front end of the fiber at the same time. And at the rear end of the fiber, a frequency-shift-mirror (FSM) is designed to back propagate the continuous wave modulated by the external vibration. Thus the Rayleigh backscattering signals (RBS) and the back propagated continuous wave interfere with the reference light at the same end of the sensing fiber and a single-end-access configuration is achieved. The RBS can be successfully separated from the interference signal (IS) through digital signal process due to their different intermediate frequency based on frequency division multiplexing technique. There is no influence between these two schemes. The experimental results show 10 m spatial resolution and up to 1.2 MHz frequency response along a 6.35 km long fiber. This newly designed single-end-access setup can achieve vibration events locating and high frequency events response, which can be widely used in health monitoring for civil infrastructures and transportation.

  18. A study on the relationship between subjective unpleasantness and body surface vibrations induced by high-level low-frequency pure tones.

    PubMed

    Takahashi, Yukio; Kanada, Kazuo; Yonekawa, Yoshiharu; Harada, Noriaki

    2005-07-01

    Human body surface vibrations induced by high-level low-frequency pure tones were measured at the chest and the abdomen. At the same time, the subject rated the unpleasantness that he had just perceived during the exposure to low-frequency noise stimulus. Examining the relationship between the measured vibration and the rating score of the unpleasantness revealed that the unpleasantness was in close correlation with the vibration acceleration level (VAL) of the vibration measured. Taking previous results into account, this finding suggests that noise-induced vibrations primarily induce vibratory sensations and through the vibratory sensation or together with some other factors, secondarily contribute to the unpleasantness. The present results suggest that in evaluating high-level low-frequency noise, the effect of vibration should be taken into account.

  19. The Effects of Vibration Frequencies on Physical, Perceptual and Cognitive Performance

    DTIC Science & Technology

    2006-10-01

    the problems related to low-altitude, high-speed flight ( Grether , 1971; Shoenberger, 1972). Problems arising from vibration exposure can also exist in...review papers on this topic. In a review by Grether (1971), it was concluded that decrements in tracking performance have been found for vertical...and y-axis) vibrations, tracking errors were the greatest between 1 and 3 Hz. Grether concluded that the magnitude of the vibration had a larger

  20. Correlation of the bond-length change and vibrational frequency shift in model hydrogen-bonded complexes of pyrrole

    NASA Astrophysics Data System (ADS)

    McDowell, Sean A. C.

    2017-04-01

    An MP2 computational study of model hydrogen-bonded pyrrole⋯YZ (YZ = NH3, NCH, BF, CO, N2, OC, FB) complexes was undertaken in order to examine the variation of the Nsbnd H bond length change and its associated vibrational frequency shift. The chemical hardness of Y, as well as the YZ dipole moment, were found to be important parameters in modifying the bond length change/frequency shift. The basis set effect on the computed properties was also assessed. A perturbative model, which accurately reproduced the ab initio Nsbnd H bond length changes and frequency shifts, was useful in rationalizing the observed trends.

  1. Simulated vibrational sum frequency generation from a multilayer thin film system with two active interfaces.

    PubMed

    O'Brien, Daniel B; Massari, Aaron M

    2013-04-21

    In the field of surface-specific vibrational sum frequency generation spectroscopy (VSFG) on organic thin films, optical interferences combined with the two-interface problem presents a challenge in terms of qualitative assessment of the data and quantitative modeling. The difficulty is amplified when considering systems comprised of more than a single material thin film layer. Recently, in our lab we have developed a generalized model that describes thin film interference in interface-specific nonlinear optical spectroscopies from arbitrary multilayer systems. Here, we apply the model to simulate VSFG spectra from the simplest multilayer: a system of two thin films, one of which is an organic small molecule and the other is a dielectric layer on a semiconductor substrate system where we idealize that the organic interfaces are equally VSFG active. Specifically, we consider the molecule N,N'-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) deposited on a silicon wafer with a thermally grown oxide dielectric. We present results for the four polarization experiments that sample the nonzero nonlinear susceptibility elements of macroscopically centrosymmetric materials (ssp, sps, pss, and ppp) and in two mIR frequency windows (the imide carbonyl stretches around 1680 cm(-1) and the alkyl stretches around 2900 cm(-1)) as a function of both thin film thicknesses with fixed input beam angles. We use frequency dependent refractive indices for all materials. The goal is to illustrate some of the intricacies contained in the intensity data of such systems. Of particular interest is the effect of the relative polar orientation of modes at the interfaces and the possibility of designing a system where the collected signal is exclusively attributable to a single interface. Our calculations indicate that in order to unambiguously identify the relative polar orientation one must experimentally vary an additional system parameter such as thin film thickness or input beam angle

  2. Empirical equations for the bond energies and vibrational frequencies at chemisorptive bonds on surfaces

    NASA Astrophysics Data System (ADS)

    Chang, Chin-An

    1982-09-01

    Empirical equations derived for bond energies and force constants of gaseous molecules are applied to chemisorptive bonds on surfaces. For two adsorbed atoms from the same family of the periodic table, A and B, the chemisorptive bond energies, E, to the same metal, M, can be approximated by EA-M/ EB-M ≈ ( EA 2/ EB 2) 1/2, where EA 2 and EB 2 are the bonds energies of diatomic molecules A 2 and B 2, respectively The corresponding vibrational frequencies, ν, can be approximated by ν 2A-M/ν 2B-M ≈ ( mB/ mA)( FA 2/ FB 2) 1/2 · mA and mB are the masses of atoms A and B, respectively; FA 2 and FB 2 are the force constants of molecules A 2 and B 2, respectively. These relations are applied to the chemisorption of halogens on metals and showed good agreement with experiment.

  3. Ab Initio Calculation of Accurate Vibrational Frequencies for Molecules of Interest in Atmospheric Chemistry

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Langhoff, Stephen R. (Technical Monitor)

    1996-01-01

    Due to advances in quantum mechanical methods over the last few years, it is now possible to determine ab initio potential energy surfaces in which fundamental vibrational frequencies are accurate to within +/- 8 cm(sup -1) on average, and molecular bond distances are accurate to within +/- 0.001-0.003 A, depending on the nature of the bond. That is, the potential energy surfaces have not been scaled or empirically adjusted in any way, showing that theoretical methods have progressed to the point of being useful in analyzing spectra that are not from a tightly controlled laboratory environment, such as rovibrational spectra from the interstellar medium. Some recent examples demonstrating this accuracy win be presented and discussed. These include the HNO, CH4, C2H4, and ClCN molecules. The HNO molecule is interesting due to the very large H-N anharmonicity, while ClCN has a very large Fermi resonance. The ab initio studies for the CH4 and C2H4 molecules present the first accurate full quartic force fields of any kind (i.e., whether theoretical or empirical) for a five-atom and six-atom system, respectively.

  4. Exploring the Underlying Biophysics of Eukaryotic Plasma Membrane Asymmetry by Sum-Frequency Vibrational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Conboy, John

    2010-03-01

    A central issue in molecular biology is the movement of lipids across the cellular membrane. The translocation of lipids is involved in cell apoptosis, the viral infection of living cells, the functioning of antibiotics, antiseptics and drugs, and the regulation and growth of cells. There have been a number of studies attempting to find the putative proteins responsive for lipid transbilayer movement in eukaryotic cells. This has led to a large number of theories about the mechanism of transbilayer movement of lipids in cellular systems and the physical process by which lipid compositional asymmetry in the plasma membrane of eukaryotic cells is maintained. Using methods of classical surface chemistry coupled with nonlinear optical methods, we have developed a novel analytical approach, using sum-frequency vibrational spectroscopy (SFVS), to selectively probe lipid compositional asymmetry in a planar supported lipid bilayer. This new method allows for the detection of lipid flip-flop kinetics and compositional asymmetry without the need for a fluorescent or spin-labeled lipid species. The effect of lipid composition, headgroup and fatty acid chemical structure, on the rate and thermodynamics of lipid transbilayer migration and the electrostatic induction of lipid asymmetry will be discussed.

  5. Poisson ratio and excess low-frequency vibrational states in glasses.

    PubMed

    Duval, Eugène; Deschamps, Thierry; Saviot, Lucien

    2013-08-14

    In glass, starting from a dependence of the Angell's fragility on the Poisson ratio [V. N. Novikov and A. P. Sokolov, Nature 431, 961 (2004)], and a dependence of the Poisson ratio on the atomic packing density [G. N. Greaves, A. L. Greer, R. S. Lakes, and T. Rouxel, Nature Mater. 10, 823 (2011)], we propose that the heterogeneities are predominantly density fluctuations in strong glasses (lower Poisson ratio) and shear elasticity fluctuations in fragile glasses (higher Poisson ratio). Because the excess of low-frequency vibration modes in comparison with the Debye regime (boson peak) is strongly connected to these fluctuations, we propose that they are breathing-like (with change of volume) in strong glasses and shear-like (without change of volume) in fragile glasses. As a verification, it is confirmed that the excess modes in the strong silica glass are predominantly breathing-like. Moreover, it is shown that the excess breathing-like modes in a strong polymeric glass are replaced by shear-like modes under hydrostatic pressure as the glass becomes more compact.

  6. Mass properties calibration of the NASA Langley low frequency vibration test apparatus

    NASA Technical Reports Server (NTRS)

    Javeed, Mehzad; Russell, James W.

    1995-01-01

    This report presents a description and calibration results of the modified NASA Langley Low Frequency Vibration Test Apparatus. The description includes both the suspension system and the data acquisition system. The test apparatus consists of a 2 inch thick, 21 inch diameter aluminum plate that is suspended from an advanced suspension system using a 40 foot long cable system. The test apparatus employed three orthogonally aligned pairs of Sundstrand QA-700 servo accelerometers that can measure accelerations as low as 1 micro-g. The calibration involved deriving the mass and moments of inertia of the test platform from measured input forces and measured acceleration responses. The derived mass and moments were compared to test platform mass properties obtained initially from measurements with a special mass properties instrument. Results of the calibration tests showed that using the product of the test apparatus mass and the measured accelerations, the disturbance force at the center of gravity (CG) can be determined within 4 percent on all three axes. Similarly the disturbance moments about the X, Y, and Z axes can be determined within 5 percent by using the product of the measured moments of inertia and the angular accelerations about the X, Y, and Z axes.

  7. Structure and orientation of interfacial proteins determined by sum frequency generation vibrational spectroscopy: method and application.

    PubMed

    Ye, Shuji; Wei, Feng; Li, Hongchun; Tian, Kangzhen; Luo, Yi

    2013-01-01

    In situ and real-time characterization of molecular structures and orientation of proteins at interfaces is essential to understand the nature of interfacial protein interaction. Such work will undoubtedly provide important clues to control biointerface in a desired manner. Sum frequency generation vibrational spectroscopy (SFG-VS) has been demonstrated to be a powerful technique to study the interfacial structures and interactions at the molecular level. This paper first systematically introduced the methods for the calculation of the Raman polarizability tensor, infrared transition dipole moment, and SFG molecular hyperpolarizability tensor elements of proteins/peptides with the secondary structures of α-helix, 310-helix, antiparallel β-sheet, and parallel β-sheet, as well as the methodology to determine the orientation of interfacial protein secondary structures using SFG amide I spectra. After that, recent progresses on the determination of protein structure and orientation at different interfaces by SFG-VS were then reviewed, which provides a molecular-level understanding of the structures and interactions of interfacial proteins, specially understanding the nature of driving force behind such interactions. Although this review has focused on analysis of amide I spectra, it will be expected to offer a basic idea for the spectral analysis of amide III SFG signals and other complicated molecular systems such as RNA and DNA. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. Vibrational sum frequency spectroscopy of surfactants and phospholipid monolayers at liquid-liquid interfaces

    NASA Astrophysics Data System (ADS)

    Smiley, Beth L.; Walker, R. A.; Gragson, D. E.; Hannon, T. E.; Richmond, Geraldine L.

    1998-04-01

    Work from our laboratory on vibrational sum frequency spectroscopic investigations of molecular ordering at the carbon tetrachloride-water interface is reviewed. Simple charged surfactants adsorbed at the liquid-liquid interface are seen to induce alignment of interfacial water molecules to a degree which is dependent on the induced surface potential. Saturation of water molecule alignment occurs at a surfactant surface concentration corresponding to a calculated surface potential of approximately 160 mV. In complementary studies, the relative degree of hydrocarbon chain ordering within monolayers of symmetric phosphatidylcholines of different chain lengths is inferred by the relative signal contributions of the methyl and methylene symmetric stretch modes. The degree of hydrocarbon chain disorder observed depends strongly on the method of monolayer preparation. By one method, a decrease in hydrocarbon chain order is seen with increasing chain length. Another method of monolayer formation yielded very well ordered hydrocarbon chains for the longest chain phosphatidylcholine studied, and showed much greater disorder in shorter chain species which was comparable to the other preparation method. These studies are a foundation for further work with this technique geared towards understanding molecular-level structural features in membrane-like assemblies and surface biochemical interactions of relevance to biomedical research.

  9. Drug-Membrane Interactions Studied by Vibrational Sum-Frequency Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wolf, Lauren; Briggman, Kimberly

    2008-03-01

    The activity of a number of drugs depends directly on their interaction with cell membranes and, thus, an understanding of drug-membrane interactions is necessary for improving their pharmacological performance. Drug molecules can interact with membranes by directly binding to membrane-bound proteins or by intercalating into the lipid matrix itself, altering membrane properties such as fluidity, thickness, internal pressure, and phase transition temperature. Here, we focus on the effects of local anesthetics incorporated into the lipid matrix, studying the structural changes induced in supported lipid bilayers by vibrational sum-frequency spectroscopy (VSFS). We find that in addition to depressing the phase transition temperature of the lipid bilayers, most anesthetics also sharpen the gel to liquid- crystalline transition, suggesting an increase in membrane constituent cooperativity. This behavior contrasts the effects of cholesterol on lipid bilayers, which increases membrane rigidity and broadens the phase transition. The structure of the membrane-intercalated anesthetics themselves will also be discussed. This work demonstrates the potential of using supported lipid bilayers and surface-sensitive techniques for future pharmacological studies.

  10. Characterization of starch polymorphic structures using vibrational sum frequency generation spectroscopy.

    PubMed

    Kong, Lingyan; Lee, Christopher; Kim, Seong H; Ziegler, Gregory R

    2014-02-20

    The polymorphic structures of starch were characterized with vibrational sum frequency generation (SFG) spectroscopy. The noncentrosymmetry requirement of SFG spectroscopy allows for the detection of the ordered domains without spectral interferences from the amorphous phase and also the distinction of the symmetric elements among crystalline polymorphs. The V-type amylose was SFG-inactive due to the antiparallel packing of single helices in crystal unit cells, whereas the A- and B-type starches showed strong SFG peaks at 2904 cm(-1) and 2952-2968 cm(-1), which were assigned to CH stretching of the axial methine group in the ring and CH2 stretching of the exocyclic CH2OH side group, respectively. The CH2/CH intensity ratios of the A- and B-type starches are significantly different, indicating that the conformation of hydroxymethyl groups in these two polymorphs may be different. Cyclodextrin inclusion complexes were also analyzed as a comparison to the V-type amylose and showed that the head-to-tail and head-to-head stacking patterns of cyclodextrin molecules govern their SFG signals and peak positions. Although the molecular packing is different between V-type amylose and cyclodextrin inclusion complexes, both crystals show the annihilation of SFG signals when the functional group dipoles are arranged pointing in opposite directions.

  11. Theoretical vibrational sum-frequency generation spectroscopy of water near lipid and surfactant monolayer interfaces

    SciTech Connect

    Roy, S.; Gruenbaum, S. M.; Skinner, J. L.

    2014-11-14

    Understanding the structure of water near cell membranes is crucial for characterizing water-mediated events such as molecular transport. To obtain structural information of water near a membrane, it is useful to have a surface-selective technique that can probe only interfacial water molecules. One such technique is vibrational sum-frequency generation (VSFG) spectroscopy. As model systems for studying membrane headgroup/water interactions, in this paper we consider lipid and surfactant monolayers on water. We adopt a theoretical approach combining molecular dynamics simulations and phase-sensitive VSFG to investigate water structure near these interfaces. Our simulated spectra are in qualitative agreement with experiments and reveal orientational ordering of interfacial water molecules near cationic, anionic, and zwitterionic interfaces. OH bonds of water molecules point toward an anionic interface leading to a positive VSFG peak, whereas the water hydrogen atoms point away from a cationic interface leading to a negative VSFG peak. Coexistence of these two interfacial water species is observed near interfaces between water and mixtures of cationic and anionic lipids, as indicated by the presence of both negative and positive peaks in their VSFG spectra. In the case of a zwitterionic interface, OH orientation is toward the interface on the average, resulting in a positive VSFG peak.

  12. Phase reference in phase-sensitive sum-frequency vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Shumei; Liang, Rongda; Xu, Xiaofan; Zhu, Heyuan; Shen, Y. Ron; Tian, Chuanshan

    2016-06-01

    Phase-sensitive sum-frequency vibrational spectroscopy (PS-SFVS) has been established as a powerful technique for surface characterization, but for it to generate a reliable spectrum, accurate phase measurement with a well-defined phase reference is most important. Incorrect phase measurement can lead to significant distortion of a spectrum, as recently seen in the case for the air/water interface. In this work, we show theoretically and experimentally that a transparent, highly nonlinear crystal, such as quartz and barium borate, can be a good phase reference if the surface is clean and unstrained and the crystal is properly oriented to yield a strong SF output. In such cases, the reflected SF signal is dominated by the bulk electric dipole contribution and its phase is either +90° or -90°. On the other hand, materials with inversion symmetry, such as water, fused quartz, and CaF2 are not good phase references due to the quadrupole contribution and phase dispersion at the interface. Using a proper phase reference in PS-SFVS, we have found the most reliable OH stretching spectrum for the air/water interface. The positive band at low frequencies in the imaginary component of the spectrum, which has garnered much interest and been interpreted by many to be due to strongly hydrogen-bonded water species, is no longer present. A weak positive feature however still exists. Its magnitude approximately equals to that of air/D2O away from resonances, suggesting that this positive feature is unrelated to surface resonance of water.

  13. Cardiac reflections and natural vibrations: Force-frequency relation recording system in the stress echo lab

    PubMed Central

    Bombardini, Tonino; Gemignani, Vincenzo; Bianchini, Elisabetta; Venneri, Lucia; Petersen, Christina; Pasanisi, Emilio; Pratali, Lorenza; Pianelli, Mascia; Faita, Francesco; Giannoni, Massimo; Picano, Eugenio

    2007-01-01

    Background The inherent ability of ventricular myocardium to increase its force of contraction in response to an increase in contraction frequency is known as the cardiac force-frequency relation (FFR). This relation can be easily obtained in the stress echo lab, where the force is computed as the systolic pressure/end-systolic volume index ratio, and measured for increasing heart rates during stress. Ideally, the noninvasive, imaging independent, objective assessment of FFR would greatly enhance its practical appeal. Objectives 1 – To evaluate the feasibility of the cardiac force measurement by a precordial cutaneous sensor. 2 – To build the curve of force variation as a function of the heart rate. 3 – To compare the standard stress echo results vs. this sensor operator-independent built FFR. Methods The transcutaneous force sensor was positioned in the precordial region in 88 consecutive patients referred for exercise, dipyridamole, or pacing stress. The force was measured as the myocardial vibrations amplitude in the isovolumic contraction period. FFR was computed as the curve of force variation as a function of heart rate. Standard echocardiographic FFR measurements were performed. Results A consistent FFR was obtained in all patients. Both the sensor built and the echo built FFR identifiy pts with normal or abnormal contractile reserve. The best cut-off value of the sensor built FFR was 15.5 g * 10-3 (Sensitivity = 0.85, Specificity = 0.77). Sensor built FFR slope and shape mirror pressure/volume relation during stress. This approach is extendable to daily physiological exercise and could be potentially attractive in home monitoring systems. PMID:18031588

  14. Impact-based piezoelectric energy harvester for multidimensional, low-level, broadband, and low-frequency vibrations

    NASA Astrophysics Data System (ADS)

    Zhang, Hongjiang; Jiang, Senlin; He, Xuefeng

    2017-05-01

    This letter proposes an impact-based piezoelectric energy harvester that uses a rolling bead contained in a bracket that is supported by a spring. Under either translational or rotational base excitation, the bead moves within the bracket and collides with piezoelectric cantilevers that are located around the bracket; these collisions cause the piezoelectric beams to vibrate and thus produce electrical outputs. The low rolling friction and the motion amplification effect of the spring make the resulting device suitable for collection of low-level vibration energy. Experiments show that the proposed harvester is promising for use in scavenging of energy from the multidimensional, low-level, broadband, and low-frequency vibrations that occur in natural environments.

  15. Improvement of vibration energy harvesters through a two-stage design: power production at single frequency excitation.

    PubMed

    Fernando, Joseph S; Sun, Qiao

    2013-11-01

    A vibration harvester is usually designed to work in resonance responding to source vibration. Many existing types of harvesters use a single mechanical resonator to amplify the excitation vibrations. However, these harvesters are inherently limited in the amount of power that they can produce, due to their design, particularly in the limited number of design parameters. In our study, we propose a two-stage design to improve a harvester's performance both in power production and in bandwidth widening. In this paper, we demonstrate that a two-stage design can increase the power production when the device is intended to operate under a single frequency excitation. Harvester parameters are optimized to provide maximum power production. Power production comparisons between single-stage and two-stage harvesters are made through numerical simulation and experiments.

  16. Research on vibration response of a multi-faulted rotor system using LMD-based time-frequency representation

    NASA Astrophysics Data System (ADS)

    Jiao, Weidong; Qian, Suxiang; Chang, Yongping; Yang, Shixi

    2012-12-01

    Unbalance, fatigue crack and rotor-stator rub are the three common and important faults in a rotor-bearing system. They are originally interconnected each other, and their vibration behaviors do often show strong nonlinear and transient characteristic, especially when more than one of them coexist in the system. This article is aimed to study the vibration response of the rotor system in presence of multiple rotor faults such as unbalance, crack, and rotor-stator rub, using local mean decomposition-based time-frequency representation. Equations of motion of the multi-faulted Jeffcott rotor, including unbalance, crack, and rub, are presented. By solving the motion equations, steady-state vibration response is obtained in presence of multiple rotor faults. As a comparison, Hilbert-Huang transformation, based on empirical mode decomposition, is also applied to analyze the multi-faults data. By the study some diagnostic recommendations are derived.

  17. Low-magnitude high-frequency loading via whole body vibration enhances bone-implant osseointegration in ovariectomized rats.

    PubMed

    Chen, BaiLing; Li, YiQiang; Xie, DengHui; Yang, XiaoXi

    2012-05-01

    Osseointegration is vital to avoid long-time implants loosening after implantation surgery. This study investigated the effect of low-magnitude high-frequency (LMHF) loading via whole body vibration on bone-implant osseointegration in osteoporotic rats, and a comparison was made between LMHF vibration and alendronate on their effects. Thirty rats were ovariectomized to induce osteoporosis, and then treated with LMHF vibration (VIB) or alendronate (ALN) or a control treatment (OVX). Another 10 rats underwent sham operation to establish Sham control group. Prior to treatment, hydroxyapatite (HA)-coated titanium implants were inserted into proximal tibiae bilaterally. Both LMHF vibration and alendronate treatment lasted for 8 weeks. Histomorphometrical assess showed that both group VIB, ALN and Sham significantly increased bone-to-implant contact and peri-implant bone fraction (p < 0.05) when compared with group OVX. Nevertheless the bone-to-implant contact and peri-implant bone fraction of group VIB were inferior to group ALN and Sham (p < 0.05). Biomechanical tests also revealed similar results in maximum push out force and interfacial shear strength. Accordingly, it is concluded that LMHF loading via whole body vibration enhances bone-to-implant osseointegration in ovariectomized rats, but its effectiveness is weaker than alendronate. Copyright © 2011 Orthopaedic Research Society.

  18. Effect of low-magnitude, high-frequency vibration on osteogenic differentiation of rat mesenchymal stromal cells

    PubMed Central

    Lau, Esther; Lee, Whitaik David; Li, Jason; Xiao, Andrew; Davies, John E.; Wu, Qianhong; Wang, Liyun; You, Lidan

    2011-01-01

    Whole body vibration (WBV), consisting of a low-magnitude, high-frequency (LMHF) signal, has been found to be anabolic to bone in vivo, which may act through alteration of the lineage commitment of mesenchymal stromal cells (MSC). Here, we investigated the effect of LMHF vibration on rat bone marrow-derived MSCs (rMSCs) in an in vitro system. We subjected rMSCs to repeated (six) bouts of 1-hour vibration at 0.3g and 60 Hz in the presence of osteogenic induction medium. The osteogenic differentiation of rMSCs under the loaded and non-loaded conditions was assessed by examining cell proliferation, alkaline phosphatase (ALP) activity, mRNA expression of various osteoblast-associated markers (ALP, Runx2, osterix, collagen type I alpha 1, bone sialoprotein, osteopontin, and osteocalcin), as well as matrix mineralization. We observed that LMHF vibration did not enhance the osteogenic differentiation of rMSCs. Surprisingly, we found that the mRNA level of osterix, a transcription factor necessary for osteoblast formation, was decreased, and matrix mineralization was inhibited. Our findings suggest that LMHF vibration may exert its anabolic effects in vivo via mechanosensing of a cell type different from MSCs. PMID:21344497

  19. Vibration-induced drop atomization and the numerical simulation of low-frequency single-droplet ejection

    NASA Astrophysics Data System (ADS)

    James, Ashley J.; Smith, Marc K.; Glezer, Ari

    2003-02-01

    Vibration-induced droplet ejection is a novel way to create a spray. In this method, a liquid drop is placed on a vertically vibrating solid surface. The vibration leads to the formation of waves on the free surface. Secondary droplets break off from the wave crests when the forcing amplitude is above a critical value. When the forcing frequency is small, only low-order axisymmetric wave modes are excited, and a single secondary droplet is ejected from the tip of the primary drop. When the forcing frequency is high, many high-order non-axisymmetric modes are excited, the motion is chaotic, and numerous small secondary droplets are ejected simultaneously from across the surface of the primary drop. In both frequency regimes a crater may form that collapses to create a liquid spike from which droplet ejection occurs. An axisymmetric, incompressible, Navier Stokes solver was developed to simulate the low-frequency ejection process. A volume-of-fluid method was used to track the free surface, with surface tension incorporated using the continuum-surface-force method. A time sequence of the simulated interface shape compared favourably with an experimental sequence. The dynamics of the droplet ejection process was investigated, and the conditions under which ejection occurs and the effect of the system parameters on the process were determined.

  20. Layer-number dependent high-frequency vibration modes in few-layer transition metal dichalcogenides induced by interlayer couplings

    NASA Astrophysics Data System (ADS)

    Tan, Qing-Hai; Zhang, Xin; Luo, Xiang-Dong; Zhang, Jun; Tan, Ping-Heng

    2017-03-01

    Two-dimensional transition metal dichalcogenides (TMDs) have attracted extensive attention due to their many novel properties. The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds, while van der Waals interactions combine the layers together. This makes its lattice dynamics layer-number dependent. The evolutions of ultralow frequency (< 50 cm‑1) modes, such as shear and layer-breathing modes have been well-established. Here, we review the layer-number dependent high-frequency (> 50 cm‑1) vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes, known as Davydov splitting. Such Davydov splitting can be well described by a van der Waals model, which directly links the splitting with the interlayer coupling. Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials. Project supported by the National Basic Research Program of China (No. 2016YFA0301200), the National Natural Science Foundation of China (Nos. 11225421, 11474277, 11434010, 61474067, 11604326, 11574305 and 51527901), and the National Young 1000 Talent Plan of China.

  1. Probing water and biomolecules at the air-water interface with a broad bandwidth vibrational sum frequency generation spectrometer from 3800 to 900 cm(-1).

    PubMed

    Ma, Gang; Liu, Jian; Fu, Li; Yan, Elsa C Y

    2009-05-01

    We have built a broad bandwidth vibrational sum frequency generation (VSFG) spectrometer that can provide high-quality spectra over the range of 3800 to 900 cm(-1). The spectrometer contains a commercial Ti:sapphire based 6 W regenerative amplifier as the master light source, a home-built pulse shaper to produce a narrow bandwidth 800 nm beam, a commercial optical parametric amplifier to generate a broad bandwidth femtosecond infrared (IR) pulse, and a detection system with a monochromator and a charge-coupled device (CCD). We applied this spectrometer to obtain VSFG spectra of a lipid monolayer at the air-water interface in the O-H stretching region (3800-3000 cm(-1)), the C-H stretching region (3100-2700 cm(-1)), the C-D stretching region (2300-2000 cm(-1)), the C=O stretching region (1800-1700 cm(-1)), and the PO(2)(-) symmetric stretching region (1200-1000 cm(-1)). We also obtained the VSFG spectrum of neat water in the O-H stretching region (3800-3000 cm(-1)) and the VSFG spectrum of a protein, alpha-synuclein, in the amide I region (1700-1600 cm(-1)) at the air-water interface. The spectrometer can provide a VSFG spectrum in the O-H stretching region (3800-3000 cm(-1)) without scanning the IR frequency. This feature will be useful in probing water dynamics at interfaces because the free OH and H-bonded OH can be investigated simultaneously. We have also provided instrumental details and discussed further improvements that should be beneficial to other researchers interested in setting up VSFG instrumentation.

  2. Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry.

    PubMed

    Wang, G; Wu, K; Hu, H; Li, G; Wang, L J

    2016-10-01

    To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

  3. Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry

    NASA Astrophysics Data System (ADS)

    Wang, G.; Wu, K.; Hu, H.; Li, G.; Wang, L. J.

    2016-10-01

    To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

  4. Low Frequency and Broadband Vibration Energy Harvesting Using Base Mounted Piezoelectric Transducers.

    PubMed

    Koven, Robert; Mills, Matthew; Gale, Richard; Aksak, Burak

    2017-08-14

    Piezoelectric vibration energy harvesters often consist of a cantilevered beam composed of a support layer and one or two piezoelectric layers with a tip mass. While this configuration is advantageous for maximizing electromechanical coupling, the mechanical properties of the piezoelectric material can place limitations on harvester size and resonant frequency. Here, we present numerical and experimental results from a new type of piezoelectric energy harvester in which the mechanical properties and the resonant frequency of the cantilever beam resonator are effectively decoupled from the piezoelectric component. Referred to as a Base Mounted Piezoelectric (BMP) harvester in this paper, this new design features a piezoelectric transducer mounted beneath the base of the cantilevered beam resonator. The flexibility in the material choice for the cantilever beam resonator means that the resonant frequency and the beam dimensions are essentially free parameters. A prototype made with a 1.6 mm × 4.9 mm × 20.0 mm polyurethane beam, a PZT-5H piezoelectric transducer, and an 8.36 g tip mass is shown to produce an average power of 8.75 μW and 113 μW at 45 Hz across a 13.0 M Ω load under harmonic base excitations of constant peak acceleration at 0.25g and 1.0g, respectively. We also show an increase in full-width half-maximum bandwidth approximately from 1.5 Hz to 5.6 Hz using an array of four individual BMP harvesters of similar dimensions with peak power generation of 10.38 μW at 37.6 Hz across a 1.934M Ω load at 0.25g peak base excitation. Finite elements based numerical simulations are shown to be in reasonable agreement with experimental results, indicating that the harvester behaves like a damped mass-spring system as proposed in the paper. Fabricated using casting and laser machining techniques, this harvester shows potential as a low cost option for powering small, low power wireless sensor nodes and other low power devices.

  5. Therapeutic impact of low amplitude high frequency whole body vibrations on the osteogenesis imperfecta mouse bone.

    PubMed

    Vanleene, Maximilien; Shefelbine, Sandra J

    2013-04-01

    Osteogenesis imperfecta (OI) is characterized by extremely brittle bone. Currently, bisphosphonate drugs allow a decrease of fracture by inhibiting bone resorption and increasing bone mass but with possible long term side effects. Whole body mechanical vibrations (WBV) treatment may offer a promising route to stimulate bone formation in OI patients as it has exhibited health benefits on both muscle and bone mass in human and animal models. The present study has investigated the effects of WBV (45Hz, 0.3g, 15minutes/days, 5days/week) in young OI (oim) and wild type female mice from 3 to 8weeks of age. Vibration therapy resulted in a significant increase in the cortical bone area and cortical thickness in the femur and tibia diaphysis of both vibrated oim and wild type mice compared to sham controls. Trabecular bone was not affected by vibration in the wild type mice; vibrated oim mice, however, exhibited significantly higher trabecular bone volume fraction in the proximal tibia. Femoral stiffness and yield load in three point bending were greater in the vibrated wild type mice than in sham controls, most likely attributed to the increase in femur cortical cross sectional area observed in the μCT morphology analyses. The vibrated oim mice showed a trend toward improved mechanical properties, but bending data had large standard deviations and there was no significant difference between vibrated and non-vibrated oim mice. No significant difference of the bone apposition was observed in the tibial metaphyseal trabecular bone for both the oim and wild type vibrated mice by histomorphometry analyses of calcein labels. At the mid diaphysis, the cortical bone apposition was not significantly influenced by the WBV treatment in both the endosteum and periosteum of the oim vibrated mice while a significant change is observed in the endosteum of the vibrated wild type mice. As only a weak impact in bone apposition between the vibrated and sham groups is observed in the

  6. An approach for modeling the influence of wheel tractor loads and vibration frequencies on soil compaction

    NASA Astrophysics Data System (ADS)

    Verotti, M.; Servadio, P.; Belfiore, N. P.; Bergonzoli, S.

    2012-04-01

    -soil-man interaction. In particular, a model based on elasto-visco-plastic concentrated parameters, with multiple degrees of freedom, will be used in order to build a method for detecting a soil damage index, especially expressed in terms of increasing of soil compaction. Besides the axle load, the model will take into account the frequency of the vibrations that the vehicle is transmitting to the soil. Such model expresses a numerical value for the transmissibility coefficient and also allows evaluating the damage at the surface and on the bulk medium where the agricultural crops initially develop. Key words: vehicle-soil interaction, vibration, compaction, models. Acknowledgements This work was carried out under the auspices of the special project "Sceneries of adaptation of the Italian agriculture to the climatic changes" (AGROSCENARI) of the Agricultural Research Council, and Italian Ministry of the Agricultural and Forestry Politics.

  7. Measurement of correlations between low-frequency vibrational modes and particle rearrangements in quasi-two-dimensional colloidal glasses.

    PubMed

    Chen, Ke; Manning, M L; Yunker, Peter J; Ellenbroek, Wouter G; Zhang, Zexin; Liu, Andrea J; Yodh, A G

    2011-09-02

    We investigate correlations between low-frequency vibrational modes and rearrangements in two-dimensional colloidal glasses composed of thermosensitive microgel particles, which readily permit variation of the sample packing fraction. At each packing fraction, the particle displacement covariance matrix is measured and used to extract the vibrational spectrum of the "shadow" colloidal glass (i.e., the particle network with the same geometry and interactions as the sample colloid but absent damping). Rearrangements are induced by successive, small reductions in the packing fraction. The experimental results suggest that low-frequency quasilocalized phonon modes in colloidal glasses, i.e., modes that present low energy barriers for system rearrangements, are spatially correlated with rearrangements in this thermal system.

  8. Experiments on Suppression of Thermocapillary Oscillations in Float-Zones by High-Frequency End-Wall Vibrations

    NASA Technical Reports Server (NTRS)

    Anilkumar, A. V.; Grugel, R. N.; Lee, C. P.; Bhowmick, J.; Wang, T. G.

    2003-01-01

    Experiments to suppress thermocapillary oscillations using high-frequency vibrations were performed on float-zones. Such a float-zone is formed by melting one end of a vertically held sodium nitrate-barium nitrate crystal rod in contact with a hot surface at the top. In the experiments, when thermocapillary oscillation occurred, the bottom end of the rod was vibrated at a high frequency to generate fine ripples on the melt surface, driving a streaming flow in the opposite direction to that of the thermocapillary convection. It was observed that by generating a sufficiently strong streaming flow the thermocapillary flow can be offset enough such that the associated thermocapillarity oscillations can be quenched.

  9. Control of the low-frequency vibrations of elastic metamaterial shafts with discretized arc-rubber layers

    NASA Astrophysics Data System (ADS)

    Lixia, Li; Anjiang, Cai

    2016-06-01

    We propose a new kind of elastic metamaterial (EM) shaft with discretized arc-shaped rubber layers, which shows excellent low-frequency vibration properties. The band gaps of the shaft structure were analyzed by employing the finite element method. The proposed EM shaft exhibits much lower band gaps than the corresponding structures with the whole rubber ring. Furthermore, the band gaps can be modulated by tuning the arc angle and the number of the arc-shaped rubbers. Additionally, we observed that the first complete band gap tends to disappear when the arc angle of each arc-shaped rubber section is decreased but the arc number remains fixed because the arc angle more strongly affects the rotational stiffness than the transverse stiffness of the rubber layers. This new type of EM shafts could find potential application as a means to control the low-frequency vibrations of rotor shafts in mechanical engineering.

  10. Effect of Vibration Frequency on Serratus Anterior Muscle Activity during Performance of the Push-up Plus with a Redcord Sling.

    PubMed

    Kim, Eui-Ryong; Oh, Jae-Seop; Yoo, Won-Gyu

    2014-08-01

    [Purpose] We investigated the effect of vibration at various frequencies on serratus anterior (SA) muscle activity. [Subjects] Ten male subjects were recruited. [Methods] The subjects performed the push-up plus exercise supported by straps above the surface and vertical ropes in the Redcord sling. During the push-up plus, vibrations of 0, 30, 50, or 90 Hz were applied to the Redcord sling using a mechanical vibration apparatus attached to the rope. SA muscle activity was recorded using electromyography. [Results] SA muscle activity at the 50 Hz vibration frequency was significantly higher than that of no vibration. [Conclusion] Performing the push-up plus using a Redcord sling with mechanical vibration of 50 Hz effectively increased SA muscle activity.

  11. On-the-fly ab intito calculations of anharmonic vibrational frequencies: Local-monomer theory and application to HCl clusters

    NASA Astrophysics Data System (ADS)

    Mancini, John S.; Bowman, Joel M.

    2013-10-01

    We present an on-the-fly quantum mechanical method to obtain anharmonic vibrational frequencies for molecular clusters. The basis for the method is the local-monomer model, a "divide and conquer" approach to theoretical spectroscopy, previously applied using full-dimensional surfaces [Y. Wang and J. M. Bowman, J. Chem. Phys. 134, 154510 (2011)]. The model consists of performing a local normal-mode analysis for each monomer in a cluster in the field of the surrounding monomers. Anharmonic vibrational frequencies are then determined for each monomer by numerically solving the Schrödinger equation in terms of the local coordinates using ab initio energies obtained directly. Residual monomer-monomer coupling is accounted for using the Hückel-coupling extension [Y. Wang and J. M. Bowman, J. Chem. Phys. 136, 144113 (2012)]. In addition to the direct local-monomer approach, we propose and demonstrate a composite ab initio technique to reduce computational costs for calculating the anharmonic frequencies of large clusters. This technique utilizes two ab initio methods, a lower level of theory to compute geometries and perform harmonic analyses and a subsequent higher level of theory to compute the energies used in the anharmonic frequency calculations. We demonstrate the on-the-fly approach on hydrogen chloride clusters ranging in size from the dimer to the hexamer. Comparisons of the theoretical frequencies are made to previous experiments. We find the method to be an effective and computationally efficient approach to compute anharmonic frequencies.

  12. High-frequency skull vibration-induced nystagmus test in partial vestibular lesions.

    PubMed

    Dumas, Georges; Karkas, Alexandre; Perrin, Philippe; Chahine, Karim; Schmerber, Sébastien

    2011-10-01

    To establish the effectiveness of the skull vibration-induced nystagmus test (SVINT) as a rapid high-frequency stimulation test, in the evaluation of partial unilateral vestibular lesions (pUVL). SVINT (30, 60, and 100 Hz), caloric, and head-shaking tests were performed in 99 patients with pUVL. These results were compared with those in 9 patients with symmetrical partial bilateral labyrinthine malformations, 131 patients with total unilateral vestibular lesions (tUVL), and 95 control subjects. A skull vibratory nystagmus (SVN) was found in 75% of patients with pUVL and 98% with tUVL. In pUVL: SVINT revealed asymmetric responses in 20% of patients where other tests were normal; SVN direction at 100 Hz was opposite to the head-shaking nystagmus direction in 30% and opposite to SVN at 30 Hz in 10% of cases. At 100 Hz, SVN beat toward the safe side in 91% of cases; SVN values at 60 and 100 Hz were higher than those at 30 Hz (p < 0.005). SVN was found in unilateral superior canal dehiscences. Partial bilateral labyrinthine malformations revealed no nystagmus. SVINT complements head-shaking and caloric tests in multifrequency assessment of patients with pUVL, as a global vestibular test. In contrast with tUVL results, SVINT does not always indicate the side of partial lesions, neither does it locate their level on the vestibulo-ocular pathway. This test is useful to reveal a vestibular asymmetry as a bedside examination test and may be used as a "vestibular Weber."

  13. Effect of Ca(2+) to Sphingomyelin Investigated by Sum Frequency Generation Vibrational Spectroscopy.

    PubMed

    Feng, Rong-Juan; Lin, Lu; Li, Yi-Yi; Liu, Ming-Hua; Guo, Yuan; Zhang, Zhen

    2017-05-23

    The interactions between Ca(2+) ions and sphingomyelin play crucial roles in a wide range of cellular activities. However, little is known about the molecular details of the interactions at interfaces. In this work, we investigated the interactions between Ca(2+) ions and egg sphingomyelin (ESM) Langmuir monolayers at the air/water interface by subwavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS). We show that Ca(2+) ions can induce ordering of the acyl chains in the ESM monolayer. An analysis of the one alkyl-chain-deuterated ESM revealed that the Ca(2+) ions do not affect the N-linked saturated fatty acid chain, although they make the sphingosine backbone become ordered. Further analysis of the SFG-VS spectra shows that the interactions between ESM and Ca(2+) ions make the orientation of the methyl group at the end of sphingosine backbone change from pointing downward to pointing upward. Moreover, a large blue shift of the phosphate group at the CaCl2 solution interface indicates, to our knowledge, new cation binding modes. Such binding causes the phosphate moiety to dehydrate, resulting in the conformation change of the phosphate moiety. Based on these results, we propose the molecular mechanism that Ca(2+) ions can bind to the phosphate group and subsequently destroy the intramolecular hydrogen bond between the 3-hydroxyl group and the phosphate oxygen, which results in an ordering change of the sphingosine backbone. These findings illustrate the potential application of HR-BB-SFG-VS to investigate lipid-cation interactions and the calcium channel modulated by lipid domain formation through slight structural changes in the membrane lipid. It will also shed light on the interactions of complex molecules at surfaces and interfaces. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  14. Characterizing the effects of amplitude, frequency and limb position on vibration induced movement illusions: Implications in sensory-motor rehabilitation

    PubMed Central

    Schofield, Jonathon S.; Dawson, Michael R.; Carey, Jason P.; Hebert, Jacqueline S.

    2015-01-01

    BACKGROUND Strategic vibration of musculotendinous regions of a limb elicits illusionary sensations of movement. As a rehabilitation technique, this ‘kinesthetic illusion’ has demonstrated beneficial results for numerous sensory-motor disorders. However, literature shows little consistency in the vibration parameters or body positioning used, and their effects have yet to be comprehensively investigated. OBJECTIVE To characterize the effects of the vibration amplitude, frequency, and limb position on the kinesthetic illusion. METHODS Movement illusions were induced in 12 participants’ biceps and triceps. The effect of amplitude (0.1 to 0.5 mm), frequency (70 to 110 Hz), and two limb positions were quantified on the strength of illusion (SOI), range of motion (ROM) and velocity. RESULTS Amplitude significantly affected the illusionary SOI, ROM and velocity in the biceps and triceps (p < 0.05). Increasing amplitude resulted in an increase of all three output variables. Limb position showed an effect on illusionary velocity in the biceps as well as ROM and velocity in the triceps (p < 0.05). Frequency demonstrated no statistical effect. CONCLUSIONS Amplitude demonstrated the most profound impact on the kinesthetic illusion in the experimental ranges tested. This work may help guide clinicians and researchers in selecting appropriate vibratory parameters and body positions to consistently elicit and manipulate the kinesthetic illusion. PMID:25425585

  15. A hybrid wave propagation and statistical energy analysis on the mid-frequency vibration of built-up plate systems

    NASA Astrophysics Data System (ADS)

    Ma, Yongbin; Zhang, Yahui; Kennedy, David

    2015-09-01

    Based on the concept of the hybrid finite element (FE) analysis and statistical energy analysis (SEA), a new hybrid method is developed for the mid-frequency vibration of a system comprising rectangular thin plates. The wave propagation method based on symplectic analysis is used to describe the vibration of the deterministic plate component. By enforcing the displacement continuity and equilibrium of force at the connection interface, the dynamic coupling between the deterministic plate component and the statistical plate component described by SEA is established. Furthermore, the hybrid solution formulation for the mid-frequency vibration of the system built up by plates is proposed. The symplectic analytical wave describing the deterministic plate component eliminates the boundary condition limitation of the traditional analytical wave propagation method and overcomes the numerical instability of numerical wave propagation methods. Numerical examples compare results from the proposed method with those from the hybrid FE-SEA method and the Monte Carlo method. The comparison illustrates that the proposed method gives good predictions for the mid-frequency behavior of the system considered here with low computational time. In addition, a constant proportionality coefficient between the system coupling power and the energy difference between the plate components can be found, when external forces are applied at different locations on a line perpendicular to the wave propagation direction. Based on this finding, two fast solution techniques are developed for the energy response of the system, and are validated by numerical examples.