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Sample records for vibrational frequency shift

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

    Science.gov (United States)

    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.

  2. Nature of the Frequency Shift of Hydrogen Valence Vibrations

    CERN Document Server

    Zhyganiuk, I V

    2015-01-01

    The physical nature of a frequency shift of hydrogen valence vibrations in a water molecule due to its interaction with neighbor molecules has been studied. Electrostatic forces connected with the multipole moments of molecules are supposed to give a dominating contribution to the intermolecular interaction. The frequency shift was calculated in the case where two neighbor molecules form a dimer. The obtained result is in qualitative agreement with the frequency shifts observed for water vapor, hexagonal ice, and liquid water, as well as for aqueous solutions of alcohols. This fact testifies to the electrostatic nature of H-bonds used to describe both the specific features of the intermolecular interaction in water and the macroscopic properties of the latter.

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

    Science.gov (United States)

    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.

  4. Quasi-optical coherence vibration tomography technique for damage detection in beam-like structures based on auxiliary mass induced frequency shift

    Science.gov (United States)

    Zhong, Shuncong; Zhong, Jianfeng; Zhang, Qiukun; Maia, Nuno

    2017-09-01

    A novel quasi-optical coherence vibration tomography (Quasi-OCVT) measurement system suitable for structural damage detection is proposed by taking the concept of two-dimensional optical coherence vibration tomography (2D-OCVT) technique. An artificial quasi-interferogram fringe pattern (QIFP) similar to the interferogram of 2D-OCVT system, as a sensor, was pasted on the surface of a vibrating structure. Image sequences of QIFP were captured by a high-speed camera that worked as a detector. The period density of the imaged QIFP changed due to the structural vibration, from which the vibration information of the structure could be obtained. Noise influence on the measurement accuracy, torsional sensitivity and optical distortion effect of the Quasi-OCVT system were investigated. The efficiency and reliability of the proposed method were demonstrated by applying the system to damage detection of a cracked beam-like structure with a roving auxiliary mass. The roving of the mass along the cracked beam brings about the change of natural frequencies that could be obtained by the Quasi-OCVT technique. Therefore, frequency-shift curves can be achieved and these curves provide additional spatial information for structural damage detection. Same cases were also analyzed by the finite element method (FEM) and conventional accelerometer-based measurement method. Comparisons were carried out among these results. Results obtained by the proposed Quasi-OCVT method had a good agreement with the ones obtained by FEM, from which the damage could be directly detected. However, the results obtained by conventional accelerometer showed misleading ambiguous peaks at damage position owing to the mass effect on the structure, where the damage location cannot be identified confidently without further confirmation. The good performance of the cost-effective Quasi-OCVT method makes it attractive for vibration measurement and damage detection of beam-like structures.

  5. The Role of Symmetric-Stretch Vibration in Asymmetric-Stretch Vibrational Frequency Shift: the Case of 2CH Excitation Infrared Spectra of Acetylene-Hydrogen Van Der Waals Complex

    Science.gov (United States)

    Hou, Dan; Ma, Yong-Tao; Zhang, Xiao-Long; Zhai, Yu; Li, Hui

    2016-06-01

    Direct infrared spectra predictions for van der Waals (vdW) complexes rely on accurate intra-molecular vibrationally excited inter-molecular potential. Due to computational cost increasing with number of freedom, constructing an effective reduced-dimension potential energy surface, which only includes direct relevant intra- molecular modes, is the most feasible way and widely used in the recent potential studies. However, because of strong intra-molecular vibrational coupling, some indirect relevant modes are also play important roles in simulating infrared spectra of vdW complexes. The questions are how many intra-molecular modes are needed, and which modes are most important in determining the effective potential and direct infrared spectra simulations. Here, we explore these issues using a simple, flexible and efficient vibration-averaged approach, and apply the method to vdW complex C_2H_2-H_2. With initial examination of the intra-molecular vibrational coupling, an effective seven-dimensional ab initio potential energy surface(PES) for C_2H_2-H_2, which explicitly takes into account the Q_1,Q_2 symmetric-stretch and Q_3 asymmetric-stretch normal modes of the C_2H_2 monomer, has been generated. Analytic four-dimensional PESs are obtained by least-squares fitting vibrationally averaged interaction energies for νb{3}(C_2H_2)=0 and 1 to the Morse/long-range(MLR) potential function form. We provide the first prediction of the infrared spectra and band origin shifts for C_2H_2-H_2 dimer. We particularly examine the dependence of the symmetric-stretch normal mode on asymmetric-stretch frequency shift for the complex.

  6. An oxorhenium complex bearing a chiral cyclohexane-1-olato-2-thiolato ligand: Synthesis, stereochemistry, and theoretical study of parity violation vibrational frequency shifts.

    Science.gov (United States)

    Saleh, Nidal; Bast, Radovan; Vanthuyne, Nicolas; Roussel, Christian; Saue, Trond; Darquié, Benoît; Crassous, Jeanne

    2017-11-15

    In our effort towards measuring the parity violation energy difference between two enantiomers, a simple chiral oxorhenium complex 5 bearing enantiopure 2-mercaptocyclohexan-1-ol has been prepared as a potential candidate species. Vibrational circular dichroism revealed a chiral environment surrounding the rhenium atom, even though the rhenium is not a stereogenic center itself, and enabled to assign the (1S,2S)-(-) and (1R,2R)-(+) absolute configuration for 5. For both compound 5 and complex 4, previously studied by us and bearing a propane-2-olato-3-thiolato ligand, relativistic calculations predict parity violating vibrational frequency differences of a few hundreds of millihertz, above the expected sensitivity attainable by a molecular beam Ramsey interferometer that we are constructing. © 2017 Wiley Periodicals, Inc.

  7. Vulnerability of Codes Using Frequency Shift Keying.

    Science.gov (United States)

    CODING, FREQUENCY SHIFT KEYERS, DATA TRANSMISSION SYSTEMS , RADIO JAMMING, FREQUENCY MODULATION, WHITE NOISE, PROBABILITY DENSITY FUNCTIONS, ERRORS, CORRECTIONS, BANDPASS FILTERS, ELECTRONIC COUNTER COUNTERMEASURES.

  8. Hippocampal theta frequency shifts and operant behaviour

    NARCIS (Netherlands)

    Lopes da Silva, F.H.; Kamp, A.

    1. 1. A shift of hippocampal dominant theta frequency to 6 c/sec has been demonstrated in the post-reward period in two dogs, which occurs consistently related in time to a well defined behavioural pattern in the course of an operant conditioning paradigm. 2. 2. The frequency shift was detected and

  9. Vibration modes and frequencies of structures

    Science.gov (United States)

    Durling, R. J.; Kvaternik, R. G.

    1980-01-01

    SUDAN, Substructuring in Direct Analysis, analyzes natural modes and frequencies of vibration of structural systems. Based on direct method of analysis that employs substructures methodology, program is used with structures that may be represented as equivalent system of beam, springs, and rigid bodies.

  10. Geometry optimization and vibrational frequencies of tetracene ...

    African Journals Online (AJOL)

    Tetracene is an organic semiconductor with chemical formula C18H12 used in organic field effecttransistor (OFET) and organic light emitting diode (OLED). In this work, the molecular geometry (optimized bond lengths and bond angles), vibrational frequencies and intensities, HOMO-LUMO Energy gap and Atomic charge ...

  11. Nonlinear frequency response analysis of structural vibrations

    Science.gov (United States)

    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.

  12. Data for phase angle shift with frequency

    Directory of Open Access Journals (Sweden)

    T. Paul

    2016-06-01

    Full Text Available Phase angle shift between the current and voltage with frequency has been reported for a single phosphoric acid fuel cell in the cell temperature from 100 °C to 160 °C and the humidifier temperature from 40 °C to 90 °C. An electrochemical workbench is employed to find the shift. The figure of phase angle shift shows a peak in high humidifier temperatures. The peak in phase angle shift directs to lower frequency side with decreasing humidifier temperature. The estimation of electrochemical reaction time is also evaluated in the humidifier temperature zone from 50 °C to 90 °C.

  13. The vibrational Stokes shift of water (HOD in D2O)

    Science.gov (United States)

    Wang, Zhaohui; Pang, Yoonsoo; Dlott, Dana D.

    2004-05-01

    The vibrational Stokes shift of the OH stretching transition νOH of water is the shift between the ground-state absorption and the excited-state (v=1) emission. A recent measurement on HOD in D2O solvent [S. Woutersen and H. J. Bakker, Phys. Rev. Lett. 83, 2077 (1999)] of a 70 cm-1 redshift, and a subsequent calculation of a 57 cm-1 redshift using equilibrium molecular dynamics simulations [C. P. Lawrence and J. L. Skinner, J. Chem. Phys. 117, 8847 (2002)] were in good agreement. We now report extensive measurements of the vibrational Stokes shift in HOD/D2O using an ultrafast IR pump, Raman probe method. The vibrational Stokes shift is seen to depend on the pump pulse frequency and on time delay; by varying these parameters it can be made to range from 112 to -32 cm-1 (negative values indicate a blueshift in the excited state). The equilibrium vibrational Stokes shift is actually a negative rather than a positive quantity. Possible reasons for the disagreement between experiment and theory are briefly discussed.

  14. Hippocampal frequency shifts in different behavioural situations

    NARCIS (Netherlands)

    Kamp, A.; Lopes da Silva, F.H.; Storm van Leeuwen, W.

    1971-01-01

    Electrical activity of the dog's hippocampus was recorded in (a) an operant behaviour situation, and (b) a field situation by a radio-telemetering system. The dominant frequency of the theta rhythm shifted consistently from 4–5 c/sec to 6–7 c/sec when a dog (a) withdrew from a pedal after being

  15. Energetics, structures, vibrational frequencies, vibrational absorption, vibrational circular dichroism and Raman intensities of Leu-enkephalin

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.

    2003-01-01

    Here we present several low energy conformers of Leu-enkephalin (LeuE) calculated with the density functional theory using the Becke 3LYP hybrid functional and the 6-31G* basis set. The structures, conformational energies, vibrational frequencies, vibrational absorption (VA) intensities......, vibrational circular dichroism (VCD) intensities and Raman scattering intensities are reported for the conformers of LeuE which are expected to be populated at room temperature. The species of LeuE-present in non-polar solvents is the neutral non-ionic species with the NH2 and CO2H groups, in contrast...... to the zwitterionic neutral species with the NH3+ and CO2- groups which predominates in aqueous solution and in the crystal. All of our attempts to find the zwitterionic species in the isolated state failed, with the result that a hydrogen atom from the positively charged N-terminus ammonium group transferred either...

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

    Science.gov (United States)

    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.

  17. Influence of Temperature on Vibrational Frequency of Graphene Sheet Used as Nano-Scale Sensing

    Directory of Open Access Journals (Sweden)

    Toshiaki Natsuki

    2017-01-01

    Full Text Available In this study, the vibrational properties of single- and double-layer graphene sheets (GSs with attached nanoparticles are analyzed based on the nonlocal elasticity theory. The potential applications of atomic-scale mass sensing are presented using GSs with simply supported boundary condition. The frequency equation for GSs with an attached nanoparticle is derived to investigate the vibration frequency of the GSs under thermal environment. Using the proposed model, the relationship between the frequency shifts of graphene-based mass sensor and the attached nanoparticles is obtained. The nonlocal effect and the temperature dependence on the variation of frequency shifts with the attached nanomass and the positions on the GS are investigated and discussed in detail. The obtained results show that the nanomass can be easily detected by using GS resonator which provides a highly sensitive nanomechanical element in sensor systems. The vibrational frequency shift of GS increases with increasing the temperature dependence. The double-layer GSs (DLGSs have higher sensitivity than the single-layer GSs (SLGSs due to high frequency shifts.

  18. Realization of fiber-based laser Doppler vibrometer with serrodyne frequency shifting.

    Science.gov (United States)

    Li, Yanlu; Meersman, Stijn; Baets, Roel

    2011-06-10

    We demonstrate a laser Doppler vibrometer (LDV) based on the serrodyne frequency shifting technique. A proof-of-principle system is implemented on the basis of fiber-optic components but opens the way toward an ultracompact integrated LDV system on a silicon chip. With a low laser power of 50  μW, the serrodyne LDV was able to measure submicrometer vibrations with frequencies in the audio range.

  19. Frequency Shifts of Micro and Nano Cantilever Beam Resonators Due to Added Masses

    KAUST Repository

    Bouchaala, Adam M.

    2016-03-21

    We present analytical and numerical techniques to accurately calculate the shifts in the natural frequencies of electrically actuated micro and nano (carbon nanotubes (CNTs)) cantilever beams implemented as resonant sensors for mass detection of biological entities, particularly Escherichia coli (E. coli) and prostate specific antigen (PSA) cells. The beams are modeled as Euler-Bernoulli beams, including the nonlinear electrostatic forces and the added biological cells, which are modeled as discrete point masses. The frequency shifts due to the added masses of the cells are calculated for the fundamental and higher-order modes of vibrations. Analytical expressions of the natural frequency shifts under a direct current (DC) voltage and an added mass have been developed using perturbation techniques and the Galerkin approximation. Numerical techniques are also used to calculate the frequency shifts and compared with the analytical technique. We found that a hybrid approach that relies on the analytical perturbation expression and the Galerkin procedure for calculating accurately the static behavior presents the most computationally efficient approach. We found that using higher-order modes of vibration of micro-electro-mechanical-system (MEMS) beams or miniaturizing the sizes of the beams to nanoscale leads to significant improved frequency shifts, and thus increased sensitivities. © 2016 by ASME.

  20. Photoisomerization of stilbene - a theoretical study of deuteration shifts and limited internal vibrational redistribution

    Science.gov (United States)

    Nordholm, Sture

    1989-10-01

    Very detailed experimental studies of the isomerization of trans-stilbene in the S 1 excited electronic state show features which are not readily explained by current theory, e.g., of RRKM type. In this work the deuteration shifts seen in the series C 14H 12, C 14H 10D 2, C 14D 10H 2, C 14D 12, where in the middle two species the ethylenic bridge positions are listed last, are investi RRKM theory modified so as to allow for a finite energy transfer rate between a critical oscillator and the remaining modes of the molecule. Vibrational frequencies are estimated on the basis of experimental results for the ground state molecule with the help of a product rule for deuteration shifts.

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

    Directory of Open Access Journals (Sweden)

    Xinhua Mao

    2014-01-01

    Full Text Available 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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 harvester

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Kyung Ho; Kim, Young-Cheol [Department of System Dynamics, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 305-343 (Korea, Republic of); Kim, Jae Eun, E-mail: jekim@cu.ac.kr [School of Mechanical and Automotive Engineering, Catholic University of Daegu, 13-13 Hayang-Ro, Hayang-Eup, Gyeongsan-Si, Gyeongsangbuk-Do 712-702 (Korea, Republic of)

    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.

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

    Directory of Open Access Journals (Sweden)

    Kyung Ho Sun

    2014-10-01

    Full Text Available 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.

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

    Science.gov (United States)

    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.

  8. Vibrational frequencies in Car-Parrinello molecular dynamics.

    Science.gov (United States)

    Ong, Sheau Wei; Tok, Eng Soon; Kang, Hway Chuan

    2010-12-07

    Car-Parrinello molecular dynamics (CPMD) are widely used to investigate the dynamical properties of molecular systems. An important issue in such applications is the dependence of dynamical quantities such as molecular vibrational frequencies upon the fictitious orbital mass μ. Although it is known that the correct Born-Oppenheimer dynamics are recovered at zero μ, it is not clear how these dynamical quantities are to be rigorously extracted from CPMD calculations. Our work addresses this issue for vibrational frequencies. We show that when the system is sufficiently close to the ground state the calculated ionic vibrational frequencies are ω(M) = ω(0M)[1 -C(μ/M)] for small μ/M, where ω(0M) is the Born-Oppenheimer ionic frequency, M the ionic mass, and C a constant that depends upon the ion-orbital coupling force constants. Our analysis also provides a quantitative understanding of the orbital oscillation amplitudes, leading to a relationship between the adiabaticity of a system and the ion-orbital coupling constants. In particular, we show that there is a significant systematic dependence of calculated vibrational frequencies upon how close the CPMD trajectory is to the Born-Oppenheimer surface. We verify our analytical results with numerical simulations for N(2), Sn(2), and H/Si(100)-(2×1).

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

    Science.gov (United States)

    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.

  10. Gearbox Vibration Signal Amplitude and Frequency Modulation

    Directory of Open Access Journals (Sweden)

    Fakher Chaari

    2012-01-01

    Full Text Available Gearboxes usually run under fluctuating load conditions during service, however most of papers available in the literature describe models of gearboxes under stationary load conditions. Main task of published papers is fault modeling for their detection. Considering real situation from industry, the assumption of stationarity of load conditions cannot be longer kept. Vibration signals issued from monitoring in maintenance operations differ from mentioned models (due to load non-stationarity and may be difficult to analyze which lead to erroneous diagnosis of the system. The objective of this paper is to study the influence of time varying load conditions on a gearbox dynamic behavior. To investigate this, a simple spur gear system without defects is modeled. It is subjected to a time varying load. The speed-torque characteristic of the driving motor is considered. The load variation induces speed variation, which causes a variation in the gearmesh stiffness period. Computer simulation shows deep amplitude modulations with sidebands that don't differ from those obtained when there is a defective tooth. In order to put in evidence the time varying load effects, Short Time Fourier Transform and then Smoothed Wigner-Ville distribution are used. Results show that the last one is well suited for the studied case.

  11. Theoretical molecular structure, vibrational frequencies and NMR ...

    African Journals Online (AJOL)

    Theoretical results have been successfully compared with available experimental data in the literature. Regarding the calculations, 2mpe-4bb prefers enol-imine form and DFT method is superior to HF approach except for predicting bond lengths. KEY WORDS: Schiff bases, Normal mode frequencies, HF, DFT, NMR. Bull.

  12. Analysis of vibration frequency in transversely-isotropic semilinear ...

    African Journals Online (AJOL)

    Analysis of vibration frequency in transversely-isotropic semilinear elastic thin plate. AP Akinola, BA Olokuntoye, OO Fadodun, AS Botokinni. Abstract. No Abstract. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · AJOL African Journals Online. HOW TO USE ...

  13. Analysis of vibration frequency in transversely-isototropic semilinear ...

    African Journals Online (AJOL)

    Analysis of vibration frequency in transversely-isototropic semilinear elastic thin plate. A.P. Akinola, B.A. Olokuntoye, O.O. Fadodun, A.S. Borokinni. Abstract. No Abstract. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · AJOL African Journals Online.

  14. Vibrational echo spectral observables and frequency fluctuations of ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 129; Issue 7. Vibrational echo spectral observables and frequency fluctuations of hydration shell water around a fluoride ion from first principles simulations. DEEPAK OJHA AMALENDU CHANDRA. REGULAR ARTICLE Volume 129 Issue 7 July 2017 pp 1069-1080 ...

  15. Vibrational echo spectral observables and frequency fluctuations of ...

    Indian Academy of Sciences (India)

    Deepak Ojha

    Vibrational echo; frequency fluctuations; hydration shell water; fluoride ion; ab initio molecular dynamics. 1. Introduction. Ions dissolved in liquid water play important roles in several chemical and biological processes.1,2 Simi- larly, water molecules in aqueous ionic solutions exhibit different dynamics in comparison to pure ...

  16. Nonlinear Vibration of Oscillation Systems using Frequency-Amplitude Formulation

    Directory of Open Access Journals (Sweden)

    A. Fereidoon

    2012-01-01

    Full Text Available In this paper we study the periodic solutions of free vibration of mechanical systems with third and fifth-order nonlinearity for two examples using He's Frequency-Amplitude Formulation (HFAF.The effectiveness and convenience of the method is illustrated in these examples. It will be shown that the solutions obtained with current method have a fabulous conformity with those achieved from time marching solution. HFAF is easy with powerful concepts and the high accuracy, so it can be found widely applicable in vibrations, especially strong nonlinearity oscillatory problems.

  17. Atomic frequency standard relativistic Doppler shift experiment

    Science.gov (United States)

    Peters, H. E.; Reinhardt, V. S.

    1974-01-01

    An experiment has been performed to measure possible space anisotropy as it would effect the frequency of a cesium atomic beam standard clock in a laboratory on earth due to motion relative to external coordinate frames. The cesium frequency was measured as a function of orientation with respect to an atomic hydrogen maser standard. Over a period of 34 days 101 measurements were made. The results are consistent with a conclusion that no general orientation dependance attributable to spacial anisotropy was observed. It is shown that both the airplane clock results, and the null results for the atomic beam clock, are consistent with Einstein general or special relativity, or with the Lorentz transformations alone.

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

    Directory of Open Access Journals (Sweden)

    Chia-Hung Wu

    2012-10-01

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

  19. Frequency Shift During Mass Properties Testing Using Compound Pendulum Method

    Science.gov (United States)

    Wolfe, David; Regan, Chris

    2012-01-01

    During mass properties testing on the X-48B Blended Wing Body aircraft (The Boeing Company, Chicago, Illinois) at the National Aeronautics and Space Administration Dryden Flight Research Center, Edwards, California, large inertia measurement errors were observed in results from compound pendulum swings when compared to analytical models. By comparing periods of oscillations as measured from an average over the test period versus the period of each oscillation, it was noticed that the frequency of oscillation was shifting significantly throughout the test. This phenomenon was only noticed during compound pendulum swings, and not during bifilar pendulum swings. The frequency shift was only visible upon extensive data analysis of the frequency for each oscillation, and did not appear in averaged frequency data over the test period. Multiple test articles, test techniques, and hardware setups were used in attempts to eliminate or identify the cause of the frequency shift. Plotting the frequency of oscillation revealed a region of minimal shift that corresponded to a larger amplitude range. This region of minimal shift provided the most accurate results compared to a known test article; however, the amplitudes that produce accurate inertia measurements are amplitudes larger than those generally accepted in mass properties testing. This paper examines two case studies of the frequency shift, using mass properties testing performed on a dummy test article, and on the X-48B Blended Wing Body aircraft.

  20. Vibration modes of injured spine at resonant frequencies under vertical vibration.

    Science.gov (United States)

    Guo, Li-Xin; Zhang, Ming; Zhang, Yi-Min; Teo, Ee-Chon

    2009-09-01

    A detailed three-dimensional finite element model of the spine segment T12-Pelvis was developed to investigate dynamic characteristics of whole lumbar spine with injured cases. This study investigates the motion mechanism of the human lumbar spine and the effect of component injuries on adjacent spinal components under whole body vibration. Several investigations have analyzed the influence of injured spines on adjacent spinal components under static loadings. However, it is not clear how the spine injury affects dynamic characteristics of whole lumbar spine and adjacent components of the injured segment under vibration. The T12-Pelvis model was used to obtain the modal vibration modes of the spine at resonant frequencies. Injury conditions of the spine were simulated and tested, including denucleation and/or facetectomy with removal of capsular ligaments. The results indicate the first-order vertical resonant frequency of the intact model is 7.21 Hz. After the denucleation at L4-L5, it decreases by more than 4% compared with the intact condition. All the injured conditions including disc injury and ligament injury decrease the resonant frequency of the spine. Due to the denucleation at L4-L5 the anteroposterior displacements of the vertebrae from L2 to L5 decrease and the vertical displacements of the vertebrae from L1 to L4 increase under vibration. The denucleation also decreases the rotational deformations of the vertebrae from L1 to L5. The material property sensitivity analysis shows intervertebral discs have a dominating effect on variation of vertical resonant frequency of the spine. The denucleation may decrease cushioning effects of adjacent motion segments at the injured level under vibration. The injured condition may increase the vertical displacement amplitudes of the spine above the injured level. All the injured conditions may decrease the resonant frequency of the spine system.

  1. Soliton self-frequency shift versus Galilean-like symmetry.

    Science.gov (United States)

    Gagnon, L; Bélanger, P A

    1990-05-01

    We show that the soliton self-frequency shift (SSFS) law as well as an approximate analytical description of the pulse deformation can be obtained on the basis of a Galilean-like symmetry of the simplest SSFS model.

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

    Science.gov (United States)

    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

  3. Adaptive Semiactive Cable Vibration Control: A Frequency Domain Perspective

    Directory of Open Access Journals (Sweden)

    Z. H. Chen

    2017-01-01

    Full Text Available An adaptive solution to semiactive control of cable vibration is formulated by extending the linear quadratic Gaussian (LQG control from time domain to frequency domain. Frequency shaping is introduced via the frequency dependent weights in the cost function to address the control effectiveness and robustness. The Hilbert-Huang transform (HHT technique is further synthesized for online tuning of the controller gain adaptively to track the cable vibration evolution, which also obviates the iterative optimal gain selection for the trade-off between control performance and energy in the conventional time domain LQG (T-LQG control. The developed adaptive frequency-shaped LQG (AF-LQG control is realized by collocated self-sensing magnetorheological (MR dampers considering the nonlinear damper dynamics for force tracking control. Performance of the AF-LQG control is numerically validated on a bridge cable transversely attached with a self-sensing MR damper. The results demonstrate the adaptivity in gain tuning of the AF-LQG control to target for the dominant cable mode for vibration energy dissipation, as well as its enhanced control efficacy over the optimal passive MR damping control and the T-LQG control for different excitation modes and damper locations.

  4. Vibration of Cracked Circular Plates at Resonance Frequencies

    Science.gov (United States)

    HUANG, CHI-HUNG; MA, CHIEN-CHING

    2000-09-01

    It is well known that the presence of cracks will affect the dynamic characteristics of the vibrating plate. Such a problem is complicated because it combines the field of vibration analysis and fracture mechanics. In this study, an optical system called the AF-ESPI method with the out-of-plane displacement measurement is employed to investigate the vibration characteristics of a free circular plate with a radial crack emanating from the edge. The boundary conditions along the circular edge are free. As compared with the film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Based on the fact that clear fringe patterns will appear only at resonant frequencies, both resonant frequencies and corresponding mode shapes can be obtained experimentally at the same time by the proposed AF-ESPI method. Numerical finite element calculations are also performed and the results are compared with the experimental measurements. Good agreements are obtained for both results. The vibrating mode shapes obtained in this study can be classified into two types, symmetric and antisymmetric modes with respect to the crack line. The influence of crack length on resonant frequencies is also investigated in terms of the dimensionless frequency parameter (λ2) versus crack length ratio (a/D). We find that if the crack face displacement is out of phase, i.e., the antisymmetric type, a large value of stress intensity factor may be induced and the cracked circular plate will be dangerous, from the fracture mechanics point of view. However, there are some resonant frequencies for which the crack face displacements are completely in phase, i.e., the symmetric type, which yields a zero stress intensity factor and the cracked plate will be safe.

  5. Beyond local group modes in vibrational sum frequency generation.

    Science.gov (United States)

    Chase, Hilary M; Psciuk, Brian T; Strick, Benjamin L; Thomson, Regan J; Batista, Victor S; Geiger, Franz M

    2015-04-09

    We combine deuterium labeling, density functional theory calculations, and experimental vibrational sum frequency generation spectroscopy into a form of "counterfactual-enabled molecular spectroscopy" for producing reliable vibrational mode assignments in situations where local group mode approximations are insufficient for spectral interpretation and vibrational mode assignments. We demonstrate the method using trans-β-isoprene epoxydiol (trans-β-IEPOX), a first-generation product of isoprene relevant to atmospheric aerosol formation, and one of its deuterium-labeled isotopologues at the vapor/silica interface. We use our method to determine that the SFG responses that we obtain from trans-β-IEPOX are almost exclusively due to nonlocal modes involving multiple C-H groups oscillating at the same frequency as one vibrational mode. We verify our assignments using deuterium labeling and use DFT calculations to predict SFG spectra of additional isotopologues that have not yet been synthesized. Finally, we use our new insight to provide a viable alternative to molecular orientation analysis methods that rely on local mode approximations in cases where the local mode approximation is not applicable.

  6. Demodulation of Vibration Signals Generated by Defects in Rolling Element Bearings Using Complex Shifted Morlet Wavelets

    Science.gov (United States)

    Nikolaou, N. G.; Antoniadis, I. A.

    2002-07-01

    Vibration signals resulting from rolling element bearing defects, present a rich content of physical information, the appropriate analysis of which can lead to the clear identification of the nature of the fault. The envelope detection or demodulation methods have been established as the dominant analysis methods for this purpose, since they can separate the useful part of the signal from its redundant contents. This paper proposes an effective demodulation method, based on the use of a complex shifted Morlet wavelet family. The method is designed in a way that can fully exploit the underlying physical concepts of the modulation mechanism, present in the vibration response of faulty bearings, using a time-frequency representation of the signal. A key element of the proposed method is the systematic introduction of selection criteria for the automated choice of the critical parameters that characterise the Morlet wavelet family used. Experimental results and industrial measurements for two different types of bearing faults confirm the validity of the overall approach.

  7. Low-frequency shift dispersive Raman spectroscopy for the analysis of respirable dosage forms.

    Science.gov (United States)

    Wang, Hui; Boraey, Mohammed A; Williams, Lisa; Lechuga-Ballesteros, David; Vehring, Reinhard

    2014-07-20

    A high performance Raman system equipped with a CCD (charged coupled device) sensor and recently developed optical filter technology is described. It provides high sensitivity, high resolution, and access to low-frequency vibrations enabling resolution of spectral features due to lattice vibrational modes and internal vibrational modes, greatly improving the ability to detect small changes due to variations in the three dimensional molecular arrangement, e.g., during loss of crystallinity. Applications to solid state analysis, such as solid phase identification and differentiation of glycopyrronium bromide and formoterol fumarate in pharmaceutical powders, and identification of active pharmaceutical ingredients, e.g., salmeterol xinafoate, fluticasone propionate, mometasone furoate, and salbutamol sulphate, as well as excipients, e.g., amino acids, in different formulations, are presented. For the first time, low-frequency shift Raman spectra of mannitol polymorphs were measured and used for solid phase identification. Unambiguous identification of two similar bronchodilator metered dose inhalers, Ventolin(®) HFA and Airomir(®), was accomplished. The low-frequency shift Raman signals can be used for the analysis of crystallinity of small samples (weight of the component of interest. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Frequency Constrained ShiftCP Modeling of Neuroimaging Data

    DEFF Research Database (Denmark)

    Mørup, Morten; Hansen, Lars Kai; Madsen, Kristoffer H.

    2011-01-01

    The shift invariant multi-linear model based on the CandeComp/PARAFAC (CP) model denoted ShiftCP has proven useful for the modeling of latency changes in trial based neuroimaging data[17]. In order to facilitate component interpretation we presently extend the shiftCP model such that the extracted...... components can be constrained to pertain to predefined frequency ranges such as alpha, beta and gamma activity. To infer the number of components in the model we propose to apply automatic relevance determination by imposing priors that define the range of variation of each component of the shiftCP model...

  9. Multiple vibrations measurement using phase-sensitive OTDR merged with Mach-Zehnder interferometer based on frequency division multiplexing.

    Science.gov (United States)

    He, Haijun; Shao, Li-Yang; Luo, Bin; Li, Zonglei; Zou, Xihua; Zhang, Zhiyong; Pan, Wei; Yan, Lianshan

    2016-03-07

    A novel measurement scheme for multiple high-frequency vibrations has been demonstrated by combining phase-sensitive optical time domain reflectometry (Ф-OTDR) and Mach-Zehnder interferometer (MZI) based on frequency division multiplexing. The light source is directly launched into the MZI structure, while it was modulated by an acoustic optical modulator (AOM) with a frequency shift of 200 MHz for the Ф-OTDR part. The vibration frequency is obtained by demodulating the interference signal obtained by the MZI structure, while the vibration position is located by Ф-OTDR system. The spatial resolution of 10m is obtained over 3 km sensing fiber. And the detectable vibration frequency reaches up to 40 kHz. Compared to the previous schemes, this system works without dead zone in the detectable frequency range. Furthermore, the frequency spectrum mapping method has been adopted to determine multiple high-frequency vibrations simultaneously. The experimental results prove the concept and match well with the theoretical analysis.

  10. Internal resonance and low frequency vibration energy harvesting

    Science.gov (United States)

    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.

  11. An Impact-Based Frequency Up-Converting Hybrid Vibration Energy Harvester for Low Frequency Application

    Directory of Open Access Journals (Sweden)

    Zhenlong Xu

    2017-11-01

    Full Text Available In this paper, a novel impact-based frequency up-converting hybrid energy harvester (FUCHEH was proposed. It consisted of a piezoelectric cantilever beam and a driving beam with a magnetic tip mass. A solenoid coil was attached at the end of the piezoelectric beam. This innovative configuration amplified the relative motion velocity between magnet and coil, resulting in an enhancement of the induced electromotive force in the coil. An electromechanical coupling model was developed and a numerical simulation was performed to study the principle of impact-based frequency up-converting. A prototype was fabricated and experimentally tested. The time-domain and frequency-domain analyses were performed. Fast Fourier transform (FFT analysis verified that fundamental frequencies and coupled vibration frequency contributes most of the output voltage. The measured maximum output power was 769.13 µW at a frequency of 13 Hz and an acceleration amplitude of 1 m/s2, which was 3249.4%- and 100.6%-times larger than that of the frequency up-converting piezoelectric energy harvesters (FUCPEH and frequency up-converting electromagnetic energy harvester (FUCEMEH, respectively. The root mean square (RMS voltage of the piezoelectric energy harvester subsystem (0.919 V was more than 16 times of that of the stand-alone PEH (0.055 V. This paper provided a new scheme to improve generating performance of the vibration energy harvester with high resonant frequency working in the low-frequency vibration environment.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. High Frequency Longitudinal Damped Vibrations of a Cylindrical Ultrasonic Transducer

    Directory of Open Access Journals (Sweden)

    Mihai Valentin Predoi

    2014-01-01

    Full Text Available Ultrasonic piezoelectric transducers used in classical nondestructive testing are producing in general longitudinal vibrations in the MHz range. A simple mechanical model of these transducers would be very useful for wave propagation numerical simulations, avoiding the existing complicated models in which the real components of the transducer are modeled by finite elements. The classical model for longitudinal vibrations is not adequate because the generated longitudinal wave is not dispersive, the velocity being the same at any frequency. We have adopted the Rayleigh-Bishop model, which avoids these limitations, even if it is not converging to the first but to the second exact longitudinal mode in an elastic rod, as obtained from the complicated Pochhammer-Chree equations. Since real transducers have significant vibrations damping, we have introduced a damping term in the Rayleigh-Bishop model, increasing the imaginary part and keeping almost identical real part of the wavenumber. Common transducers produce amplitude modulated signals, completely attenuated after several periods. This can be modeled by two close frequencies, producing a “beat” phenomenon, superposed on the high damping. For this reason, we introduce a two-rod Rayleigh-Bishop model with damping. Agreement with measured normal velocity on the transducer free surface is encouraging for continuation of the research.

  15. Experimental investigation on frequency shifting of imperfect adhesively bonded pipe joints

    Science.gov (United States)

    Haiyam, F. N.; Hilmy, I.; Sulaeman, E.; Firdaus, T.; Adesta, E. Y. T.

    2018-01-01

    Inspection tests for any manufactured structure are compulsory in order to detect the existence of damage.It is to ensure the product integrity, reliability and to avoid further catastrophic failure. In this research, modal analysis was utilized to detect structural damage as one of the Non Destructive Testing (NDT) methods. Comparing the vibration signal of a healthy structure with a non-healthy signal was performed. A modal analysis of an adhesively bonded pipe joint was investigated with a healthy joint as a reference. The damage joint was engineered by inserting a nylon fiber, which act as an impurity at adhesive region. The impact test using hammer was utilized in this research. Identification of shifting frequency of a free supported and clamped pipe joint was performed.It was found that shifting frequency occurred to the lower side by 5%.

  16. High force vibration testing with wide frequency range

    Science.gov (United States)

    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.

  17. Modified Pippard relationship describing the Raman frequency shifts ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. We relate in this study the thermal expansivity, αP, to the Raman frequency shift (1/ν)(∂ν/∂P)T for the rotatory lattice (librational) mode in ammonia solid II near its melting point. We have used our calculated Raman frequencies of this mode for pressures of 3⋅65, 5⋅02 and 6⋅57 kbars for this crystalline system.

  18. Review of sensors for low frequency seismic vibration measurement

    CERN Document Server

    Collette, C; Janssens, S; Artoos, K; Guinchard, M; Hauviller, C

    2011-01-01

    The objective of this report is to review the main different types of sensors used to measure seismic vibrations at low frequencies. After some basic background preliminaries, the main different types of relative measurements are first reviewed. Then, the following inertial sensors are treated: geophones, accelerometers and broadband seismometers. For each of these sensors, the basic working principle is explained, along with the main performances limitations. Each section ends with a tentative comparison of some commercial products, far from being exhaustive, but hopefully representative of the average characteristics of each family of sensors. The report finishes with a brief discussion on the modelling and measurement of the sensor noise

  19. Frequency-shift vs phase-shift characterization of in-liquid quartz crystal microbalance applications

    Energy Technology Data Exchange (ETDEWEB)

    Montagut, Y. J.; Garcia, J. V.; Jimenez, Y.; Arnau, A. [Grupo de Fenomenos Ondulatorios, Departamento de Ingenieria Electronica, Universitat Politecnica de Valencia (Spain); March, C.; Montoya, A. [Instituto Interuniversitario de Investigacion en Bioingenieria y Tecnologia Orientada al Ser Humano, Universitat Politecnica de Valencia (Spain)

    2011-06-15

    The improvement of sensitivity in quartz crystal microbalance (QCM) applications has been addressed in the last decades by increasing the sensor fundamental frequency, following the increment of the frequency/mass sensitivity with the square of frequency predicted by Sauerbrey. However, this sensitivity improvement has not been completely transferred in terms of resolution. The decrease of frequency stability due to the increase of the phase noise, particularly in oscillators, made impossible to reach the expected resolution. A new concept of sensor characterization at constant frequency has been recently proposed. The validation of the new concept is presented in this work. An immunosensor application for the detection of a low molecular weight contaminant, the insecticide carbaryl, has been chosen for the validation. An, in principle, improved version of a balanced-bridge oscillator is validated for its use in liquids, and applied for the frequency shift characterization of the QCM immunosensor application. The classical frequency shift characterization is compared with the new phase-shift characterization concept and system proposed.

  20. Frequency Up-Converted Low Frequency Vibration Energy Harvester Using Trampoline Effect

    Science.gov (United States)

    Ju, S.; Chae, S. H.; Choi, Y.; Jun, S.; Park, S. M.; Lee, S.; Lee, H. W.; Ji, C.-H.

    2013-12-01

    This paper presents a non-resonant vibration energy harvester based on magnetoelectric transduction mechanism and mechanical frequency up-conversion using trampoline effect. The harvester utilizes a freely movable spherical permanent magnet which bounces off the aluminum springs integrated at both ends of the cavity, achieving frequency up-conversion from low frequency input vibration. Moreover, bonding method of magnetoelectric laminate composite has been optimized to provide higher strain to piezoelectric material and thus obtain a higher output voltage. A proof-of-concept energy harvesting device has been fabricated and tested. Maximum open-circuit voltage of 11.2V has been obtained and output power of 0.57μW has been achieved for a 50kΩ load, when the fabricated energy harvester was hand-shaken.

  1. Analytical Harmonic Vibrational Frequencies for the Green Fluorescent Protein Computed with ONIOM: Chromophore Mode Character and Its Response to Environment.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  4. Noise-free quantum optical frequency shifting driven by mechanics

    CERN Document Server

    Fan, Linran; Poot, Menno; Cheng, Risheng; Guo, Xiang; Han, Xu; Tang, Hong X

    2016-01-01

    The ability to manipulate single photons is of critical importance for fundamental quantum optics studies and practical implementations of quantum communications. While extraordinary progresses have been made in controlling spatial, temporal, spin and orbit angular momentum degrees of freedom, frequency-domain control of single photons so far relies on nonlinear optical effects, which have faced obstacles such as noise photons, narrow bandwidth and demanding optical filtering. Here we demonstrate the first integrated near-unity efficiency frequency manipulation of single photons, by stretching and compressing a waveguide at 8.3 billion cycles per second. Frequency shift up to 150 GHz at telecom wavelength is realized without measurable added noise and the preservation of quantum coherence is verified through quantum interference between twin photons of different colors. This single photon frequency control approach will be invaluable for increasing the channel capacity of quantum communications and compensati...

  5. Damping and Frequency Shift of Large Amplitude Electron Plasma Waves

    DEFF Research Database (Denmark)

    Thomsen, Kenneth; Juul Rasmussen, Jens

    1983-01-01

    The initial evolution of large-amplitude one-dimensional electron waves is investigated by applying a numerical simulation. The initial wave damping is found to be strongly enhanced relative to the linear damping and it increases with increasing amplitude. The temporal evolution of the nonlinear...... damping rate γ(t) shows that it increases with time within the initial phase of propagation, t≲π/ωB (ωB is the bounce frequency), whereafter it decreases and changes sign implying a regrowth of the wave. The shift in the wave frequency δω is observed to be positive for t≲π/ωB; then δω changes sign...

  6. Tapered amplifier laser with frequency-shifted feedback

    Directory of Open Access Journals (Sweden)

    A. Bayerle, S. Tzanova, P. Vlaar, B. Pasquiou, F. Schreck

    2016-10-01

    Full Text Available We present a frequency-shifted feedback (FSF laser based on a tapered amplifier. The laser operates as a coherent broadband source with up to 370GHz spectral width and 2.3us coherence time. If the FSF laser is seeded by a continuous-wave laser a frequency comb spanning the output spectrum appears in addition to the broadband emission. The laser has an output power of 280mW and a center wavelength of 780nm. The ease and flexibility of use of tapered amplifiers makes our FSF laser attractive for a wide range of applications, especially in metrology.

  7. Brillouin frequency shift measurement with virtually controlled sensitivity

    Science.gov (United States)

    Tanaka, Yosuke; Ozaki, Yuta

    2017-06-01

    We propose measuring the change in Brillouin frequency shift (BFS) in an optical fiber with virtually controlled sensitivity based on the Vernier effect using a multimode pump and probe light. We measure BFS from the envelope curve of the spectra for multimode Stokes light without scanning the probe frequency. The sensitivity of BFS is virtually controlled by changing the difference in the mode spacing between the pump and the probe. It is experimentally demonstrated that the virtual sensitivity is controlled from -1.1 to 1.1 GHz/K, the maximum value of which is 1,100 times higher than the standard BFS of 1 MHz/K.

  8. Enhancement of vibration desensitising capability of iterative algorithms for phase-shifting interferometers

    Science.gov (United States)

    Liu, Qian; Yuan, Daocheng; He, Huabin

    2017-11-01

    The sensitivity of phase-shifting interferometers (PSIs) to vibration impairs their application in unsteady environment. Iterative algorithms were developed to desensitise the effect of vibration on PSIs, but their desensitising capability is restricted by the estimated initial value. In this paper, a spatial carrier-assisted method is proposed, in which a wavefront phase retrieved from an additional spatial-carrier interferogram is used as the initial value. Because of the benefits of spatial carrier, vibration immunity and sign determination, iteration could converge to accurate value even when interferometers are under severe vibration. To reduce the possibility of transverse movement of the measured surface, subsampling strategy is further proposed to decrease the required tilt angle, with the additional benefit of decreasing the calculation time of iteration. Computer simulations and experiments are performed to verify the effectiveness of the proposed method. Results indicate that the vibration desensitising capability of an iterative algorithm is significantly enhanced by the proposed method. The proposed method improves the vibration desensitising capability with low cost and is thus highly compatible.

  9. Modeling of Doppler frequency shift in multipath radiochannels

    Science.gov (United States)

    Penzin, Maksim; Iyin, Nikolay

    2016-06-01

    We discuss the modeling of propagation of a quasi-monochromatic radio signal, represented by a coherent pulse sequence, in a non-stationary multipath radio channel. In such a channel, signal propagation results in the observed frequency shift for each ray (Doppler effect). The modeling is based on the assumption that during propagation of a single pulse a channel can be considered stationary. A phase change in the channel transfer function is shown to cause the observed frequency shift in the received signal. Thus, instead of measuring the Doppler frequency shift, we can measure the rate of change in the mean phase of one pulse relative to another. The modeling is carried out within the framework of the method of normal waves. The method enables us to model the dynamics of the electromagnetic field at a given point with the required accuracy. The modeling reveals that a local change in ionospheric conditions more severely affects the rays whose reflection region is in the area where the changes occur.

  10. Natural vibration frequencies of horizontal tubes partially filled with liquid

    Science.gov (United States)

    Santisteban Hidalgo, Juan Andrés; Gama, Antonio Lopes; Moreira, Roger Matsumoto

    2017-11-01

    This work presents an experimental and numerical study on the flexural vibration of horizontal circular tubes partially filled with liquid. The tube is configured as a free-free beam with attention being directed to the case of small amplitudes of transverse oscillation whereas the axial movements of the tube and liquid are disregarded. At first vertical and horizontal polarizations of the flexural tube are investigated experimentally for different amounts of filling liquid. In contrast with the empty and fully-filled tubes, it is observed that natural frequencies of the vertical and horizontal polarizations are different due to asymmetry induced by the liquid layer, which acts like an added mass. Less mass of liquid is added to the tube when oscillating horizontally; as a consequence, eigenfrequencies for the horizontal polarization are found to be greater than the case of the vertically polarized tube. A simple method to calculate the natural vibration frequencies using coefficients of added mass of liquid is proposed. It is shown that the added mass coefficient increases with the liquid's level and viscosity. At last a numerical investigation of the interaction between the liquid and the tube is carried out by solving in two-dimensions the full Navier-Stokes equations via a finite volume method, with the free-surface flow being modeled with a homogeneous multiphase Eulerian-Eulerian fluid approach. Vertical and horizontal polarizations are imposed to the tube with pressure and shear stresses being determined numerically to assess the liquid's forcing onto the tube's wall. The coefficient of added mass of liquid is then estimated by the ratio between the resulting force and the acceleration imposed to the wall. A good agreement is found between experimental and numerical results, especially for the horizontally oscillating tube. It is also shown that viscosity can noticeably affect the added mass coefficients, particularly at low filling levels.

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

    Science.gov (United States)

    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

  12. High-accuracy Brillouin frequency shift measurement system based on stimulated Brillouin scattering phase shift

    Science.gov (United States)

    Li, Yongqian; An, Qi; Li, Xiaojuan; Zhang, Lixin

    2017-05-01

    A high-accuracy Brillouin frequency shift (BFS) measurement system for vector Brillouin optical time-domain analysis-based temperature sensor is proposed, in which double sideband modulation is used and the stimulated Brillouin scattering (SBS) gain and loss processes work together to generate a superimposed SBS phase-shift spectrum. The measurement principle is analyzed by mathematical modeling and the proof-of-concept experiment is performed by using a 100-m long standard single-mode fiber. The theoretical and experimental results reveal that the temperature sensitivity of BFS obtained from the measured SBS phase-shift spectrum is 1.059 MHz/°C, and the measurement error of temperature is only half that in traditional single sideband-based system, which indicates that the proposed technique can realize high-accuracy temperature measurement and have huge potential in the field of long-distance and high-accuracy sensing.

  13. High Frequency Vibration Based Fatigue Testing of Developmental Alloys

    Science.gov (United States)

    Holycross, Casey M.; Srinivasan, Raghavan; George, Tommy J.; Tamirisakandala, Seshacharyulu; Russ, Stephan M.

    Many fatigue test methods have been previously developed to rapidly evaluate fatigue behavior. This increased test speed can come at some expense, since these methods may require non-standard specimen geometry or increased facility and equipment capability. One such method, developed by George et al, involves a base-excited plate specimen driven into a high frequency bending resonant mode. This resonant mode is of sufficient frequency (typically 1200 to 1700 Hertz) to accumulate 107 cycles in a few hours. One of the main limitations of this test method is that fatigue cracking is almost certainly guaranteed to be surface initiated at regions of high stress. This brings into question the validity of the fatigue test results, as compared to more traditional uniaxial, smooth-bar testing, since high stresses are subjecting only a small volume to fatigue damage. This limitation also brings into question the suitability of this method to screen developmental alloys, should their initiation life be governed by subsurface flaws. However, if applicable, the rapid generation of fatigue data using this method would facilitate faster design iterations, identifying more quickly, material and manufacturing process deficiencies. The developmental alloy used in this study was a powder metallurgy boron-modified Ti-6Al-4V, a new alloy currently being considered for gas turbine engine fan blades. Plate specimens were subjected to fully reversed bending fatigue. Results are compared with existing data from commercially available Ti-6Al-4V using both vibration based and more traditional fatigue test methods.

  14. Frequency shifting approach towards textual transcription of heartbeat sounds

    Directory of Open Access Journals (Sweden)

    Safar Khorasani Ehsan

    2011-10-01

    Full Text Available Abstract Auscultation is an approach for diagnosing many cardiovascular problems. Automatic analysis of heartbeat sounds and extraction of its audio features can assist physicians towards diagnosing diseases. Textual transcription allows recording a continuous heart sound stream using a text format which can be stored in very small memory in comparison with other audio formats. In addition, a text-based data allows applying indexing and searching techniques to access to the critical events. Hence, the transcribed heartbeat sounds provides useful information to monitor the behavior of a patient for the long duration of time. This paper proposes a frequency shifting method in order to improve the performance of the transcription. The main objective of this study is to transfer the heartbeat sounds to the music domain. The proposed technique is tested with 100 samples which were recorded from different heart diseases categories. The observed results show that, the proposed shifting method significantly improves the performance of the transcription.

  15. Joint Multilevel Turbo Equalization and Continuous Phase Frequency Shift Keying

    Directory of Open Access Journals (Sweden)

    Odabasioglu Niyazi

    2008-01-01

    Full Text Available A novel type of turbo coded modulation scheme, called multilevel turbo coded-continuous phase frequency shift keying (MLTC-CPFSK, is designed to improve the overall bit error rate (BER and bandwidth efficiency. Then, this scheme is combined with a new double decision feedback equalizer (DDFE to remove the interference and to enhance BER performance for the intersymbol interference (ISI channels. The entire communication scheme is called multilevel turbo equalization-continuous phase frequency shift keying (MLTEQ-CPFSK. In these schemes, parallel input data sequences are encoded using the multilevel scheme and mapped to CPFSK signals to obtain a powerful code with phase continuity over the air. The performances of both MLTC-CPFSK and MLTEQ-CPFSK systems were simulated over nonfrequency and frequency-selective channels, respectively. The superiority of the two level turbo codes with 4CPFSK modulation is shown against the trellis-coded 4CPFSK, multilevel convolutional coded 4CPFSK, and TTCM schemes. Finally, the bit error rate curve of MLTEQ-CPFSK system over Proakis B channel is depicted and ISI cancellation performance of DDFE equalizer is shown against linear and decision feedback equalizers

  16. Frequencies in the Vibration Induced by the Rotor Stator Interaction in a Centrifugal Pump Turbine

    DEFF Research Database (Denmark)

    Rodriguez, Cristian; Egusquiza, Eduard; Santos, Ilmar

    2007-01-01

    The highest vibration levels in large pump turbines are, in general, originated in the rotor stator interaction (RSI). This vibration has specific characteristics that can be clearly observed in the frequency domain: harmonics of the moving blade passing frequency and a particular relationship am...

  17. Frequency-shift-keyer circuit improves PCM conversion for radio transmission

    Science.gov (United States)

    Mikszan, D. P.

    1964-01-01

    A data logic circuit employing a fixed frequency, square-wave oscillator and flip-flop gates allows for the shifting from one frequency to the other at the end of a whole number of cycles of one shift frequency and at the beginning of a cycle of the second shift frequency.

  18. Acid-hemolytic stability of erythrocytes of intense erythropoiesis under conditions of low-frequency vibration

    Directory of Open Access Journals (Sweden)

    O. I. Dotsenko

    2014-04-01

    Full Text Available This paper deals with the peculiarities of functioning of murine erythron system under vibrational stress on the basis of experimental data about erythrocytes acid resistance. Experiments were made on the outbred male mice at about one age and weight that were maintained in vivarium conditions on usual diet. Animals were divided into 5 groups. Animals of 1–4 groups were exposed to daily thirty-minute vibration at frequencies of 8, 16, 24 and 32 Hz respectively, with amplitude of 0.8 ±0.12 mmduring 14 days. Animal exposure to vibration was provided by the electromechanical converter connected to the generator of low frequency signals. The fifth group of animals was not exposed to vibration and it was used as a control. Kinetic dependences of acid hemolysis of erythrocytes was registered daily, from the 1st to the 5th day, and further at the 7th, 9th and 14th days of experiment. Blood for analysis was taken from tail veins in 15–20 min after stopping of vibration. As the basic indicators characterizing resistance of erythrocytes to the hemolytic agent influence we used the hemolysis rate constant, i.e. the value inverse to cell half-life time. For analysis of acid erythrograms we also used such indicators as hemolysis duration, maximum erythrogram’s time and width of the interval of erythrocyte group dominating in the population. We processed the results of research statistically. The study showed that acid resistance of erythrocytes decreased during the first five days of vibration influence at frequencies of 8–16 Hz. Besides, erythrocytes were divided into fractions that indicated the erythrocytes aging and strengthening of the population heterogeneity. On the fifth day of 16 Hz influence the emission of reticulocytes was recorded. At 8 Hz influence these processes were registered on the 7th day of the experiment. During the subsequent days the hemolysis curves were slightly displaced in relation to the control. Increase in hemolysis

  19. Raman induced soliton self-frequency shift in microresonator Kerr frequency combs

    CERN Document Server

    Karpov, Maxim; Kordts, Arne; Brasch, Victor; Pfeiffer, Martin; Zervas, Michail; Geiselmann, Michael; Kippenberg, Tobias J

    2015-01-01

    The formation of temporal dissipative solitons in continuous wave laser driven microresonators enables the generation of coherent, broadband and spectrally smooth optical frequency combs as well as femtosecond pulses with compact form factor. Here we report for the first time on the observation of a Raman-induced soliton self-frequency shift for a microresonator soliton. The Raman effect manifests itself in amorphous SiN microresonator based single soliton states by a spectrum that is hyperbolic secant in shape, but whose center is spectrally red-shifted (i.e. offset) from the continuous wave pump laser. The Raman induced spectral red-shift is found to be tunable via the pump laser detuning and grows linearly with peak power. The shift is theoretically described by the first order shock term of the material's Raman response, and we infer a Raman shock time of 20 fs for amorphous SiN. Moreover, we observe that the Raman induced frequency shift can lead to a cancellation or overcompensation of the soliton recoi...

  20. Analytical predictions for vibration phase shifts along fluid-conveying pipes due to Coriolis forces and imperfections

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel; Dahl, Jonas

    2010-01-01

    Resonant vibrations of a fluid-conveying pipe are investigated, with special consideration to axial shifts in vibration phase accompanying fluid flow and various imperfections. This is relevant for understanding elastic wave propagation in general, and for the design and trouble-shooting of phase...

  1. Frequency-Shift Detectors Bind Binaural as Well as Monaural Frequency Representations

    Science.gov (United States)

    Carcagno, Samuele; Semal, Catherine; Demany, Laurent

    2011-01-01

    Previous psychophysical work provided evidence for the existence of automatic frequency-shift detectors (FSDs) that establish perceptual links between successive sounds. In this study, we investigated the characteristics of the FSDs with respect to the binaural system. Listeners were presented with sound sequences consisting of a chord of pure…

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

    Science.gov (United States)

    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.

  3. A hybrid single-end-access MZI and Φ-OTDR vibration sensing system with high frequency response

    Science.gov (United States)

    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.

  4. Cancellation of Collisional Frequency Shifts in Optical Lattice Clocks with Rabi Spectroscopy

    OpenAIRE

    Lee, Sangkyung; Park, Chang Yong; Lee, Won-Kyu; Yu, Dai-Hyuk

    2015-01-01

    We analyze both the s- and p-wave collision induced frequency shifts and propose a over-$\\pi$ pulse scheme to cancel the shifts in optical lattice clocks interrogated by a Rabi pulse. The collisional frequency shifts are analytically solved as a function of the pulse area and the inhomogeneity of the Rabi frequencies. Experimentally measured collisional frequency shifts in an Yb optical lattice clock are in good agreement with the analytical calculations. Based on our analysis, the over-$\\pi$...

  5. Effect of Frequency and Vibration Time on Shaker Performance for Mechanized Harvesting of Orange (Thomson cultivar

    Directory of Open Access Journals (Sweden)

    H Ghorbanpour

    2012-09-01

    Full Text Available Manual citrus harvesting is commonly performing hard, expensive and time consuming. In this study, a factorial experiment with a completely randomized design in three replications was performed to find out the effect of frequency (three levels of 5, 7.5 and 10 Hz, vibration time (three levels of 10, 15 and 20 seconds on harvesting capacity and losses of Thomson cultivar of orange. The results indicated that the effect of frequency and vibration time was significant (P≤0.01 on the harvesting capacity and losses, but their interaction effects weren’t significant. The harvesting capacity significantly increased by increasing frequency, and the highest harvesting capacity was 62.8 % at 10 Hz frequency. Although the harvesting capacity increased by increasing the vibration time, but there was no significant difference in vibration times between 15 and 20 seconds at 10 Hz frequency. Also the fruit loss was increased by increasing the vibration time. Due to these reasons, frequency of 10 Hz and vibration time of 15 seconds were selected as the most suitable condition for mechanized harvesting of this cultivar of orange. Finally a linear mathematical model was developed based on the frequency and vibration time for the harvesting capacity and fruit loss of Thomson cultivar of orange.

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

    Science.gov (United States)

    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.

  7. Contact area affects frequency-dependent responses to vibration in the peripheral vascular and sensorineural systems.

    Science.gov (United States)

    Krajnak, Kristine; Miller, G R; Waugh, Stacey

    2018-01-01

    Repetitive exposure to hand-transmitted vibration is associated with development of peripheral vascular and sensorineural dysfunctions. These disorders and symptoms associated with it are referred to as hand-arm vibration syndrome (HAVS). Although the symptoms of the disorder have been well characterized, the etiology and contribution of various exposure factors to development of the dysfunctions are not well understood. Previous studies performed using a rat-tail model of vibration demonstrated that vascular and peripheral nervous system adverse effects of vibration are frequency-dependent, with vibration frequencies at or near the resonant frequency producing the most severe injury. However, in these investigations, the amplitude of the exposed tissue was greater than amplitude typically noted in human fingers. To determine how contact with vibrating source and amplitude of the biodynamic response of the tissue affects the risk of injury occurring, this study compared the influence of frequency using different levels of restraint to assess how maintaining contact of the tail with vibrating source affects the transmission of vibration. Data demonstrated that for the most part, increasing the contact of the tail with the platform by restraining it with additional straps resulted in an enhancement in transmission of vibration signal and elevation in factors associated with vascular and peripheral nerve injury. In addition, there were also frequency-dependent effects, with exposure at 250 Hz generating greater effects than vibration at 62.5 Hz. These observations are consistent with studies in humans demonstrating that greater contact and exposure to frequencies near the resonant frequency pose the highest risk for generating peripheral vascular and sensorineural dysfunction.

  8. High Security Chipless RFID Tags Using Frequency Shift Coding Technique

    Directory of Open Access Journals (Sweden)

    M. Sumi

    2017-09-01

    Full Text Available A high security chipless RFID tag designed using E shaped resonator is presented in this paper. The tag identity is encoded using Frequency Shift Coding technique. 144 different code words are possible in 2.78 to 3.85 GHz band using two E shaped resonators. The tag identity can be decoded from either amplitude or group delay information. The resonators are designed and fabricated on substrate C-MET LK4.3 of dielectric constant 4.3 and loss tangent 0.0018. Different tag combinations are designed and tested using bistatic measurement setup. Measurement results on realized prototypes are provided to ensure the reliability of the proposed design.

  9. Mathematical model for the adsorption-induced nonlocal frequency shift in adatoms-nanobeam system

    Science.gov (United States)

    Bourouina, Hicham; Yahiaoui, Réda; Kerid, Rachid; Amine Benamar, Mohammed El; Brioua, Fathi

    2017-09-01

    This paper models and investigates the resonance frequency shift induced by the adsorption phenomena for an adatoms-nanobeam system including the small scale effect as well as rotary inertia and shear distortion effects. The Lennard-Jones (6-12) type potential is used to determine the adsorption-induced energy owing van der Waals (vdW) interaction mechanism between adatom-adatom and adatom-substrate. The small scale effect is introduced by using Eringen's nonlocal elasticity theory while the explicit expressions of inertia moment and shear force are derived from the standard Timoshenko beam equations in which the residual stress effect is accounted as an additive axial load. Numerical results showed that the resonance frequency shift is depended on each of the adsorption density, mode number and small scale effects. Thus, numerical results are discussed in detail for a proper analysis of dynamic vibration behavior of adatoms-nanobeam systems which are of interest in the development of mass sensing devices.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  12. Magnetic field shift due to mechanical vibration in functional magnetic resonance imaging.

    Science.gov (United States)

    Foerster, Bernd U; Tomasi, Dardo; Caparelli, Elisabeth C

    2005-11-01

    Mechanical vibrations of the gradient coil system during readout in echo-planar imaging (EPI) can increase the temperature of the gradient system and alter the magnetic field distribution during functional magnetic resonance imaging (fMRI). This effect is enhanced by resonant modes of vibrations and results in apparent motion along the phase encoding direction in fMRI studies. The magnetic field drift was quantified during EPI by monitoring the resonance frequency interleaved with the EPI acquisition, and a novel method is proposed to correct the apparent motion. The knowledge on the frequency drift over time was used to correct the phase of the k-space EPI dataset. Since the resonance frequency changes very slowly over time, two measurements of the resonance frequency, immediately before and after the EPI acquisition, are sufficient to remove the field drift effects from fMRI time series. The frequency drift correction method was tested "in vivo" and compared to the standard image realignment method. The proposed method efficiently corrects spurious motion due to magnetic field drifts during fMRI. (c) 2005 Wiley-Liss, Inc.

  13. Diagnosis of industrial gearboxes condition by vibration and time-frequency, scale-frequency, frequency-frequency analysis

    Directory of Open Access Journals (Sweden)

    P. Czech

    2012-10-01

    Full Text Available In the article methods of vibroacoustic diagnostics of high-power toothed gears are described. It is shown below, that properly registered and processed acoustic signal or vibration signal may serve as an explicitly interpreted source of diagnostic symptoms. The presented analysis were based on vibration signals registered during the work of the gear of a rolling stand working in Katowice Steel Plant (presently one of the branches of Mittal Steel Poland JSC.

  14. Determining carotid plaque vulnerability using ultrasound center frequency shifts.

    Science.gov (United States)

    Erlöv, Tobias; Cinthio, Magnus; Edsfeldt, Andreas; Segstedt, Simon; Dias, Nuno; Nilsson, Jan; Gonçalves, Isabel

    2016-03-01

    The leading cause of morbidity and mortality worldwide is atherosclerotic cardiovascular disease, most commonly caused by rupture of a high-risk plaque and subsequent thrombosis resulting in stroke, myocardial infarction or sudden death depending on the affected arterial territory. Accurate, non-invasive methods to identify such lesions known as vulnerable or high-risk plaques are currently sub-optimal. Our aim was to validate a new non-invasive ultrasound method to identify high-risk carotid plaques. We evaluated a new method based on the center frequency shift (CFS) of the ultrasound radio frequency data obtained from carotid plaques compared to a reference phantom. We evaluated the method both ex vivo, on 157 sections from 18 plaques, and in vivo, in 39 patients 1-day prior to carotid plaque removal, and correlated the data with histology. The CFS correlated with a plaque vulnerability index based on histological areas stained for lipids, macrophages, hemorrhage, smooth muscle cells and collagen (r = -0.726, P = 1.7 × 10(-8)). Plaques with CFS below median had larger cores, more macrophages and were less rich in collagen in agreement with the definition of rupture-prone plaques. The accuracy to detect plaques with high vulnerability index was 78% (confidence interval (CI) 61-89%), with sensitivity 77% (CI 61-89%) and specificity 78% (CI 62-89%). Our method is the first to characterize atherosclerotic plaque components that affect plaque vulnerability using CFS. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  15. Investigation into high-frequency-vibration assisted micro-blanking of pure copper foils

    Directory of Open Access Journals (Sweden)

    Wang Chunju

    2015-01-01

    Full Text Available The difficulties encountered during the manufacture of microparts are often associated with size effects relating to material, process and tooling. Utilizing acoustoplastic softening, achieved through a high-frequency vibration assisted micro-blanking process, was introduced to improve the surface finish in micro-blanking. A frequency of 1.0 kHz was chosen to activate the longitudinal vibration mode of the horn tip, using a piezoelectric actuator. A square hole with dimensions of 0.5 mm × 0.5 mm was made, successfully, from a commercial rolled T2 copper foil with 100 μm in thickness. It was found that the maximum blanking force could be reduced by 5% through utilizing the high-frequency vibration. Proportion of the smooth, burnished area in the cut cross-section increases with an increase of the plasticity to fracture, under the high-frequency vibration, which suggests that the vibration introduced is helpful for inhibiting evolution of the crack due to its acoustoplastic softening effect. During blanking, roughness of the burnished surface could be reduced by increasing the vibration amplitude of the punch, which played a role as surface polishing. The results obtained suggest that the high-frequency vibration can be adopted in micro-blanking in order to improve quality of the microparts.

  16. Structure-borne sound structural vibrations and sound radiation at audio frequencies

    CERN Document Server

    Cremer, L; Petersson, Björn AT

    2005-01-01

    Structure-Borne Sound"" is a thorough introduction to structural vibrations with emphasis on audio frequencies and the associated radiation of sound. The book presents in-depth discussions of fundamental principles and basic problems, in order to enable the reader to understand and solve his own problems. It includes chapters dealing with measurement and generation of vibrations and sound, various types of structural wave motion, structural damping and its effects, impedances and vibration responses of the important types of structures, as well as with attenuation of vibrations, and sound radi

  17. Modelling of tuning of an ultra low frequency Roberts Linkage vibration isolator

    Energy Technology Data Exchange (ETDEWEB)

    Dumas, Jean-Charles, E-mail: jcdumas@physics.uwa.edu.a [School of Physics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Ju Li; Blair, David G. [School of Physics, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

    2010-08-09

    We present an analytical model for a Roberts Linkage used as an ultra low frequency vibration isolator. The Roberts Linkage is a structure that simulates a very long radius conical pendulum, at a relatively small height. We show through an analytical solution that it is possible to independently tune the centre of percussion and the resonant frequency for arbitrary geometrical configurations. The result is shown to provide a practical tuning solution, which achieves near ideal vibration isolation.

  18. Modelling of tuning of an ultra low frequency Roberts Linkage vibration isolator

    Science.gov (United States)

    Dumas, Jean-Charles; Ju, Li; Blair, David G.

    2010-08-01

    We present an analytical model for a Roberts Linkage used as an ultra low frequency vibration isolator. The Roberts Linkage is a structure that simulates a very long radius conical pendulum, at a relatively small height. We show through an analytical solution that it is possible to independently tune the centre of percussion and the resonant frequency for arbitrary geometrical configurations. The result is shown to provide a practical tuning solution, which achieves near ideal vibration isolation.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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/s2 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.

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

    Science.gov (United States)

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

    2012-01-01

    The A 1B1 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

  3. Estimation of the running speed and bearing defect frequencies of an induction motor from vibration data

    Science.gov (United States)

    Ocak, Hasan; Loparo, Kenneth A.

    2004-05-01

    This paper presents two separate algorithms for estimating the running speed and the bearing key frequencies of an induction motor using vibration data. Bearing key frequencies are frequencies at which roller elements pass over a defect point. Most frequency domain-based bearing fault detection and diagnosis techniques (e.g. envelope analysis) rely on vibration measurements and the bearing key frequencies. Thus, estimation of the running speed and the bearing key frequencies are required for failure detection and diagnosis. The paper also incorporates the estimation algorithms with the most commonly used bearing fault detection technique, high-frequency demodulation, to detect bearing faults. Experimental data were used to verify the validity of the algorithms. Data were collected through an accelerometer measuring the vibration from the drive-end ball bearing of an induction motor (Reliance Electric 2HP IQPreAlert)-driven mechanical system. Both inner and outer race defects were artificially introduced to the bearing using electrical discharge machining. A linear vibration model was also developed for generating simulated vibration data. The simulated data were also used to validate the performance of the algorithms. The test results proved the algorithms to be very reliable.

  4. DIAGNOSIS SHAFT BEARINGS NODE KNIFE CUTTER FOR LOW-FREQUENCY VIBRATION

    Directory of Open Access Journals (Sweden)

    S. T. Antipov

    2015-01-01

    Full Text Available The currently used system of preventive maintenance is not effective enough. Vibration diagnostics is one of the modern methods of non-destructive testing equipment components, allowing to define the appearance of defects in the early stages. The paper identifies the main areas of research, as well as selected research object, selected non-destructive testing method for efficiently determining the actual state of dynamically operating equipment. Is a schematic of vibration sensors. Measuring point vibration parameters were determined experimentally based on the conditions for obtaining the most informative vibroacoustic signal. Determine the behavior of the cutter under which minimizes the occurrence of a wide range of fluctuations that affects the accuracy of the measurements. For vibration analysis method was chosen direct spectral analysis, which involves the detection of repetitive vibrations. Presented graphically vibration spectra and spectra of vibration signals. Analysis of a wide range of vibration spectrum allowed to allocate land on which showed a significant increase in the values of vibration. Processing of the selected portion of the spectrum has led to the conclusion that in the bearing, shock pulses are in contact with each rolling body shell, and as a result, a number of harmonics in the individual frequencies. Was made a comparative analysis of the spectra of working with a defective bearing bearing on the same frequencies and determine the average increase in the values of vibration. Spectral analysis is an effective method to determine not only the extent of the defect and its location, but also allows you to effectively predict its development. The results may be useful for specialists involved in vibration diagnostics, calculation and design of rotary machines.

  5. A smart and self-sufficient frequency tunable vibration energy harvester

    Science.gov (United States)

    Eichhorn, C.; Tchagsim, R.; Wilhelm, N.; Woias, P.

    2011-10-01

    We present a piezoelectric energy-harvesting system, which is able to self-tune its resonance frequency in an energy-autonomous way, in order to extend its efficient operation over a large frequency range. The system consists of a resonant and frequency-tunable piezoelectric generator and a control unit. In predefined temporal intervals, the control unit analyzes the ambient vibration frequency, decides whether an adjustment of the generator's resonance frequency is necessary or not and delivers the appropriate voltage to a piezoelectric actuator which alters the generator's mechanical stiffness to tune its resonance frequency. The control unit has been optimized to an ultralow power consumption which means that up to 90% of the harvested energy can be fed to the powered electrical load, which could be an embedded system. With frequency-tunable generators, the application range of vibration energy harvesters can be extended to environments with a non-constant vibration frequency, like e.g. the surface of an engine with a varying number of revolutions per minute. Furthermore, the presented system opens the door to off-the-shelf solutions for environments with constant but uncommon vibration frequencies. With the smart tuning algorithm presented in this work, our system is even able to compensate typical weak points of piezoelectrically tunable harvesters, like e.g. hysteresis effects, the temperature dependence of the mechanical stiffness and aging effects.

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

    Science.gov (United States)

    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 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 noisy vibration (peak coherence ~40 Hz), and

  7. Influence of surface micro-beams with large deflection on the resonance frequency of a quartz crystal resonator in thickness-shear mode vibrations

    Directory of Open Access Journals (Sweden)

    Chi Luo

    2017-03-01

    Full Text Available We study the dynamic behavior of a quartz crystal resonator (QCR in thickness-shear vibrations with the upper surface covered by an array of micro-beams (MBs under large deflection. Through taking into account the continuous conditions of shear force and bending moment at the interface of MBs/resonator, dependences of frequency shift of the compound QCR system versus material parameter and geometrical parameter are illustrated in detail for nonlinear and linear vibrations. It is found that the frequency shift produces a little right (left translation for increasing elastic modulus (length/radius ratio of MBs. Moreover, the frequency right (left translation distance caused by nonlinear deformation becomes more serious in the second-order mode than in the first-order one.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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 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.

  10. The modeling of frequency Doppler shift in multibeam weakly non-stationary radio channels

    Science.gov (United States)

    Penzin, M. S.; Ilyin, N. V.

    2015-11-01

    Under measurement of Doppler shift for signal frequency one define the characteristic average on time or Doppler spectrum. The use of impulses coherent sequence allows to measure Doppler shift of frequency taking into account its small variations caused by non-stationarity of the ionospheric radio channel. In the report we consider the changes of frequency Doppler shift for each beam depending on time under modeling the propagation of impulses coherent sequence through weakly non-stationary ionospheric radio channel.

  11. A Stepwise Optimal Design of a Dynamic Vibration Absorber with Tunable Resonant Frequency

    Directory of Open Access Journals (Sweden)

    Jiejian DI

    2014-08-01

    Full Text Available A new kind of dynamic vibration absorber (DVA with tunable resonant frequency is presented. The kinematics differential equation about it is built and the stepwise optimization is performed. Firstly, four main system parameters involving the ratios of mass m, natural frequency f, vibration frequency g and damping z are solved by small-step-search method to obtain optimal steady state amplitude. Secondly, the sizing optimization of the dynamic vibration absorber is proceeded to search an optimal damping effect based on the optimal parameters (g, m, z, f. And such the damping effect is simulated in a flat structure, and the results show that the working frequency band and damping effect of the DVA after optimization won 20 % of the effect of ascension compared with that before optimization.

  12. Influence of low-frequency vibration on the erythrocytes acid resistance

    Directory of Open Access Journals (Sweden)

    O. I. Dotsenko

    2011-02-01

    Full Text Available The influence of low-frequency vibration (frequency range 8–32 Hz, amplitudes 0.5 ± 0.04 and 0.9 ± 0.08 mm on the erythrocytes’ acid resistance was studied. The kinetics of various hemolysis stages was investigated. The time-frequency dependences of the kinetics constants of hemolysis stages were obtained and discussed. It was shown that 8–16 Hz vibration with the 0.5 mm amplitude and 8 Hz with 0.9 mm causes destructive reorganizations of a cytoplasm’s water-protein structure. It leads to decrease in a permeability barrier for a hemolytic agent. As a result of oxidizing stress the vibration in the frequency range of 20–32 Hz causes the modifying reactions leading to the aggregation of cellular proteins and, in particular, the band 3 protein.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  16. Measurement of Mechatronic Property of Biological Gel with Micro-Vibrating Electrode at Ultrasonic Frequency

    Directory of Open Access Journals (Sweden)

    Shigehiro Hashimoto

    2008-10-01

    Full Text Available A measurement system has been designed with a micro-vibrating electrode at ultrasonic frequency to measure local impedance of biological gel in vitro. The designed system consists of two electrodes, where one of the electrodes vibrates with a piezoelectric actuator. The component of variation at impedance between two electrodes with vibration of one electrode is analyzed at the corresponding spectrum. The manufactured system was applied to measure impedance of a physiological saline solution, a potassium chloride solution, a dextran aqueous solution, and an egg. The experimental results show that the designed system is effective to measure local mechatronic property of biological gel.

  17. Effect of different vibration frequencies on heart rate variability and driving fatigue in healthy drivers.

    Science.gov (United States)

    Jiao, Kun; Li, Zengyong; Chen, Ming; Wang, Chengtao; Qi, Shaohua

    2004-04-01

    This investigation was to assess the effect of different vibration frequencies on heart rate variability (HRV) and driving fatigue in healthy subjects during simulated driving, by the use of power spectrum analysis and subjective evaluation. Sixty healthy subjects (29.6+/-3.3 years) were randomly divided into three groups, A, B and C, and the subjects of each group participated in the simulated driving for 90 min with vertical sinusoidal vibration (acceleration 0.05 g) of 1.8 Hz (group A), 6 Hz (group B) and no vibration (group C), respectively. Low-frequency (LF) and high-frequency (HF) components of HRV, reflecting sympathetic and parasympathetic activities, and the LF:HF ratio, indicating sympathovagal balance, were measured throughout all periods. All indices of HRV were calculated in the pre-experiment period, mid-experiment period and end-experiment period, and were analyzed by repeated measures analysis of variance. Subjective responses to a questionnaire were obtained after the simulated task for the three groups. Significant differences in all indices of HRV were observed between different experiment periods and between any two groups. The ratings of subjective fatigue exhibited significant differences between any two groups. The drivers' fatigue ratings were associated with vibration frequencies in simulated driving. The study quantitatively demonstrated that different effects on autonomic nerve activities were induced by different vibration frequencies.

  18. Low frequency vibrations induce malformations in two aquatic species in a frequency-, waveform-, and direction-specific manner.

    Directory of Open Access Journals (Sweden)

    Laura N Vandenberg

    Full Text Available 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.

  19. Energy calibration issues in nuclear resonant vibrational spectroscopy: observing small spectral shifts and making fast calibrations.

    Science.gov (United States)

    Wang, Hongxin; Yoda, Yoshitaka; Dong, Weibing; Huang, Songping D

    2013-09-01

    The conventional energy calibration for nuclear resonant vibrational spectroscopy (NRVS) is usually long. Meanwhile, taking NRVS samples out of the cryostat increases the chance of sample damage, which makes it impossible to carry out an energy calibration during one NRVS measurement. In this study, by manipulating the 14.4 keV beam through the main measurement chamber without moving out the NRVS sample, two alternative calibration procedures have been proposed and established: (i) an in situ calibration procedure, which measures the main NRVS sample at stage A and the calibration sample at stage B simultaneously, and calibrates the energies for observing extremely small spectral shifts; for example, the 0.3 meV energy shift between the 100%-(57)Fe-enriched [Fe4S4Cl4](=) and 10%-(57)Fe and 90%-(54)Fe labeled [Fe4S4Cl4](=) has been well resolved; (ii) a quick-switching energy calibration procedure, which reduces each calibration time from 3-4 h to about 30 min. Although the quick-switching calibration is not in situ, it is suitable for normal NRVS measurements.

  20. Vibration characteristics of composite piezoceramic plates at resonant frequencies: experiments and numerical calculations.

    Science.gov (United States)

    Huang, C H; Ma, C C

    2001-07-01

    The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. In this paper, we employ an optical interferometry method called the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) to investigate the vibration characteristics of piezoceramic/aluminum laminated plates. The AF-ESPI is a powerful tool for the full-field, noncontact, and real-time measurement method of surface displacement for vibrating bodies. As compared with the conventional film recording and optical reconstruction procedures used for holographic interferometry, the interferometric fringes of AF-ESPI are produced instantly by a video recording system. Because the clear fringe patterns measured by the AF-ESPI method will be shown only at resonant frequencies, both the resonant frequencies and corresponding vibration mode shapes are obtained experimentally at the same time. Excellent quality of the interferometric fringe patterns for both the in-plane and out-of-plane vibration mode shapes are demonstrated. Two different configurations of piezoceramic/aluminum laminated plates, which exhibit different vibration characteristics because of the polarization direction, are investigated in detail. From experimental results, we find that some of the out-of-plane vibration modes (Type A) with lower resonant frequencies cannot be measured by the impedance analysis; however, all of the vibration modes of piezoceramic/aluminum laminated plates can be obtained by the AF-ESPI method. Finally, the numerical finite element calculations are also performed, and the results are compared with the experimental measurements. Excellent agreements of the resonant frequencies and mode shapes are obtained for both results.

  1. A Simulation Study of the Fundamental Vibrational Shifts of HCl Diluted in Ar, Kr, and Xe: Anharmonic Corrections Effects

    Directory of Open Access Journals (Sweden)

    A. Padilla

    2012-01-01

    Full Text Available We have calculated the vibrational solvent shifts of the fundamental bands of HCl diluted in Ar, Kr, and Xe solutions at different thermodynamic conditions by means of the molecular dynamics technique and a model for the isotropic part of the interaction depending on the vibration. The theoretical vibrational shifts, which were compared with the available experimental data, have been determined by considering both, the usual linear Buckingham terms and the nonlinear anharmonic corrections, and the latter omitted in a previous work for the HCl in Ar and Kr. We have found that the Buckingham contributions dominate the solvent shifts of the fundamental bands of HCl in Ar, Kr, and Xe, although the anharmonic shifts’ present significant greater values than those obtained previously for N2 diluted in liquid Ar and pure liquid N2, both at normal conditions. We have analyzed the solvent shifts influence of the linear and quadratic (in the vibrational coordinate oscillator-bath interaction terms and also the Dunham intramolecular potential effects on the anharmonic contributions.

  2. An analytical model for a piezoelectric vibration energy harvester with resonance frequency tunability

    Directory of Open Access Journals (Sweden)

    Yun Wang

    2015-06-01

    Full Text Available This article conceptually proposes a new method to tune the resonance frequency of piezoelectric vibration energy harvesters, in which the supporting position of the vibrator can be adjusted for frequency tuning. The corresponding analytical model is established to predict the performances of the harvester based on the principles of energy. First, the equivalent stiffness and mass of the vibrator in bending mode are derived explicitly for the different supporting positions. A simple analysis method is then established for the frequency, output voltage, and output power. Finally, some numerical examples are given to demonstrate the presented method. The results are also compared with those by finite element method and good agreement is observed.

  3. Experimental investigation on low-frequency vibration assisted micro-WEDM of Inconel 718

    Directory of Open Access Journals (Sweden)

    Deepak Rajendra Unune

    2017-02-01

    Full Text Available The micro-wire electric discharge machining (micro-WEDM has emerged as the popular micromachining processes for fabrication of micro-features. However, the low machining rate and poor surface finish are restricting wide applications of this process. Therefore, in this study, an attempt was made to improve machining rate of micro-WEDM with low-frequency workpiece vibration assistance. The gap voltage, capacitance, feed rate and vibrational frequency were chosen as control factors, whereas, the material removal rate (MRR and kerf width were selected as performance measures while fabricating microchannels in Inconel 718. It was observed that in micro-WEDM, the capacitance is the most significant factor affecting both MRR and kerf width. It was witnessed that the low-frequency workpiece vibration improves the performance of micro-WEDM by improving the MRR due to enhanced flushing conditions and reduced electrode-workpiece adhesion.

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

    Directory of Open Access Journals (Sweden)

    Vytautas Ostasevicius

    2015-05-01

    Full Text Available 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.

  5. Photonic radio frequency phase-shift amplification by radio frequency interferometry.

    Science.gov (United States)

    Ayun, Moshe Ben; Schwarzbaum, Arye; Rosenberg, Seva; Pinchas, Monika; Sternklar, Shmuel

    2015-11-01

    We present a new technique for radio frequency (RF) phase-shift amplification based on RF interferometry and demonstrate it in an optical system. A striking feature of this amplifier is that the input phase noise is not amplified together with the input phase signal, so the phase sensitivity improves with higher phase amplification. We also predict that in the case of correlated amplitude noise, the sensitivity is not affected by the amplitude noise. With 600 MHz of modulated light and a phase amplification of 100, we demonstrate a phase resolution of 0.2 mrad, giving a distance resolution of 8 μm. We postulate that nanometric distance resolution can be achieved with sub-gigahertz modulation.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yuksek, N. S.; Almasri, M. [Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Feng, Z. C. [Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211 (United States)

    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.

  7. Dual resonant structure for energy harvesting from random vibration sources at low frequency

    Directory of Open Access Journals (Sweden)

    Shanshan Li

    2016-01-01

    Full Text Available We introduce a design with dual resonant structure which can harvest energy from random vibration sources at low frequency range. The dual resonant structure consists of two spring-mass subsystems with different frequency responses, which exhibit strong coupling and broad bandwidth when the two masses collide with each other. Experiments with piezoelectric elements show that the energy harvesting device with dual resonant structure can generate higher power output than the sum of the two separate devices from random vibration sources.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hong, E-mail: h-yu@seu.edu.cn; Chen, Hong-Bo [Key Lab of MEMS of Ministry of Education, Nanjing, Jiangsu, 210096 (China)

    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).

  9. An induction motor model for high-frequency torsional vibration analysis

    Science.gov (United States)

    Widdle, R. D.; Krousgrill, C. M.; Sudhoff, S. D.

    2006-03-01

    High-frequency torsional oscillations of a 50 horsepower (hp) induction motor are investigated up to approximately 30 kHz. It is experimentally determined that torsional oscillations, due to the switching harmonics of the motor drive, contribute significantly to the torsional oscillation of the output shaft. Two torsional vibration models are developed. One model assumes the rotor to be rigid, while the other has a compliant rotor. The compliant model allows for greater transmission of high-frequency oscillations, and a better prediction of the measured output shaft vibration.

  10. Vibration Mode Observation of Piezoelectric Disk-type Resonator by High Frequency Laser Doppler Vibrometer

    Science.gov (United States)

    Matsumura, Takeshi; Esashi, Masayoshi; Harada, Hiroshi; Tanaka, Shuji

    For future mobile phones based on cognitive radio technology, a compact multi-band RF front-end architecture is strongly required and an integrated multi-band RF filter bank is a key component in it. Contour-mode resonators are receiving increased attention for a multi-band filter solution, because its resonant frequency is mainly determined by its size and shape, which are defined by lithography. However, spurious responses including flexural vibration are also excited due to its thin structure. To improve resonator performance and suppress spurious modes, visual observation with a laser probe system is very effective. In this paper, we have prototyped a mechanically-coupled disk-array filter, which consists of a Si disk and 2 disk-type resonators of higher-order wine-glass mode, and observed its vibration modes using a high-frequency laser-Doppler vibrometer (UHF-120, Polytec, Inc.). As a result, it was confirmed that higher order wine-glass mode vibration included a compound displacement, and that its out-of-plane vibration amplitude was much smaller than other flexural spurious modes. The observed vibration modes were compared with FEM (Finite Element Method) simulation results. In addition, it was also confirmed that the fabrication error, e.g. miss-alignment, induced asymmetric vibration.

  11. Cancellation of Collisional Frequency Shifts in Optical Lattice Clocks with Rabi Spectroscopy

    CERN Document Server

    Lee, Sangkyung; Lee, Won-Kyu; Yu, Dai-Hyuk

    2015-01-01

    We analyze both the s- and p-wave collision induced frequency shifts and propose a over-$\\pi$ pulse scheme to cancel the shifts in optical lattice clocks interrogated by a Rabi pulse. The collisional frequency shifts are analytically solved as a function of the pulse area and the inhomogeneity of the Rabi frequencies. Experimentally measured collisional frequency shifts in an Yb optical lattice clock are in good agreement with the analytical calculations. Based on our analysis, the over-$\\pi$ pulse combined with a small inhomogeneity below 0.1 allows a fractional uncertainty on a level of $10^{-18}$ in both Sr and Yb optical lattice clocks by canceling the collisional frequency shift. \\end{abstract}

  12. Cancellation of collisional frequency shifts in optical lattice clocks with Rabi spectroscopy

    Science.gov (United States)

    Lee, Sangkyung; Park, Chang Yong; Lee, Won-Kyu; Yu, Dai-Hyuk

    2016-03-01

    We analyze both the s- and p-wave collision induced frequency shifts and propose an over-π pulse scheme to cancel the shifts in optical lattice clocks interrogated by a Rabi pulse. The collisional frequency shifts are analytically solved as a function of the pulse area and the inhomogeneity of the Rabi frequencies. Experimentally measured collisional frequency shifts in an Yb optical lattice clock are in good agreement with the analytical calculations. Based on our analysis, the over-π pulse combined with a small inhomogeneity below 0.1 allows a fractional uncertainty on a level of 10-18 in both Sr and Yb optical lattice clocks by canceling the collisional frequency shift.

  13. Resonances in BSO with frequency shifted input beams

    DEFF Research Database (Denmark)

    Buchhave, Preben; Vasnetsov, M.; Lyuksyutov, S.

    1996-01-01

    In this publication we report experiments with a frequency modulated offset frequency, which illustrate in which situations the problem may be considered linear, and in which it may not. Surprisingly we find, that even in the region of subharmonic generation, the space-charge field of the primary...

  14. Spin-exchange frequency shift in a cesium atomic fountain

    NARCIS (Netherlands)

    Tiesinga, E.; Verhaar, B.J.; Stoof, H.T.C.; Bragt, D. van

    1992-01-01

    In connection with experiments aiming at the improvement of the cesium atomic beam clock by means of a fountain of laser-cooled cesium atoms, we present expressions for the line shift and line broadening due to collisions between cesium atoms. The coherent collision cross sections occurring in these

  15. Active Mechanisms of Vibration Encoding and Frequency Filtering in Central Mechanosensory Neurons.

    Science.gov (United States)

    Azevedo, Anthony W; Wilson, Rachel I

    2017-10-11

    To better understand biophysical mechanisms of mechanosensory processing, we investigated two cell types in the Drosophila brain (A2 and B1 cells) that are postsynaptic to antennal vibration receptors. A2 cells receive excitatory synaptic currents in response to both directions of movement: thus, twice per vibration cycle. The membrane acts as a low-pass filter, so that voltage and spiking mainly track the vibration envelope rather than individual cycles. By contrast, B1 cells are excited by only forward or backward movement, meaning they are sensitive to vibration phase. They receive oscillatory synaptic currents at the stimulus frequency, and they bandpass filter these inputs to favor specific frequencies. Different cells prefer different frequencies, due to differences in their voltage-gated conductances. Both Na + and K + conductances suppress low-frequency synaptic inputs, so cells with larger voltage-gated conductances prefer higher frequencies. These results illustrate how membrane properties and voltage-gated conductances can extract distinct stimulus features into parallel channels. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    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.

  17. Effects of low frequency vibration of a limb

    Science.gov (United States)

    Agarwal, G. C.; Gottlieb, G. L.

    1975-01-01

    Low frequency oscillations were applied on the ankle joint in plantarflexion/dorsiflexion rotation using a torque motor. The torque, the angular rotation and the evoked electromyogram from the gastronemius soleus and the anterior tibial muscles were recorded. Significant nonlinearities were observed in the angular rotation from 8 to 12 Hz. The following methods are used for data analysis: (1) Two cycle averaged response; (2) Fourier transform; and (3) Fourier analysis at the driving frequency. Important observations are: (1) resonance near 6 to 8 Hz; (2) slowly increasing amplitudes of oscillation near resonance; (3) self sustaining oscillations after the motor is turned off, particularly in the fatigued limb; and (4) distortion of angular rotation during which there are spontaneous recurrences of oscillation at the driving frequency.

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

    Science.gov (United States)

    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.

  19. Modeling Carbon Dioxide Vibrational Frequencies in Ionic Liquids: II. Spectroscopic Map.

    Science.gov (United States)

    Daly, Clyde A; Berquist, Eric J; Brinzer, Thomas; Garrett-Roe, Sean; Lambrecht, Daniel S; Corcelli, Steven A

    2016-12-15

    The primary challenge for connecting molecular dynamics (MD) simulations to linear and two-dimensional infrared measurements is the calculation of the vibrational frequency for the chromophore of interest. Computing the vibrational frequency at each time step of the simulation with a quantum mechanical method like density functional theory (DFT) is generally prohibitively expensive. One approach to circumnavigate this problem is the use of spectroscopic maps. Spectroscopic maps are empirical relationships that correlate the frequency of interest to properties of the surrounding solvent that are readily accessible in the MD simulation. Here, we develop a spectroscopic map for the asymmetric stretch of CO2 in the 1-butyl-3-methylimidazolium hexafluorophosphate ([C4C1im][PF6]) ionic liquid (IL). DFT is used to compute the vibrational frequency of 500 statistically independent CO2-[C4C1im][PF6] clusters extracted from an MD simulation. When the map was tested on 500 different CO2-[C4C1im][PF6] clusters, the correlation coefficient between the benchmark frequencies and the predicted frequencies was R = 0.94, and the root-mean-square error was 2.7 cm-1. The calculated distribution of frequencies also agrees well with experiment. The spectroscopic map required information about the CO2 angle, the electrostatics of the surrounding solvent, and the Lennard-Jones interaction between the CO2 and the IL. The contribution of each term in the map was investigated using symmetry-adapted perturbation theory calculations.

  20. Compact and Low-Frequency Vibration Energy Scavenger using the longitudinal excitation of a piezoelectric bar

    Science.gov (United States)

    Colin, M.; Mortier, Q.; Basrour, S.; Bencheikh, N.

    2013-12-01

    This paper introduces an innovative architecture of a piezoelectric harvester, which enables harvesting vibration energy at low frequency using the {33}-transduction mode of a piezoelectric element. Unlike cantilevers integrating ferroelectric material combined with interdigitated electrodes, the concept that we propose is based on the elongation/compression excitation of a piezoelectric bar.

  1. High frequency vibration conditioning stimulation centrally reduces myoelectrical manifestation of fatigue in healthy subjects.

    Science.gov (United States)

    Casale, Roberto; Ring, Haim; Rainoldi, Alberto

    2009-10-01

    Vibration conditioning has been adopted as a tool to improve muscle force and reduce fatigue onset in various rehabilitation settings. This study was designed to asses if high frequency vibration can induce some conditioning effects detectable in surface EMG (sEMG) signal; and whether these effects are central or peripheral in origin. 300 Hz vibration was applied for 30 min during 5 consecutive days, to the right biceps brachii muscle of 10 healthy males aged from 25 to 50 years. sEMG was recorded with a 16 electrode linear array placed on the skin overlying the vibrated muscle. The test protocol consisted of 30% and 60% maximal voluntary contraction (MVC) as well as involuntary (electrically elicited) contractions before and after treatment. No statistically significant differences were found between PRE and POST vibration conditioning when involuntary stimulus-evoked contraction and 30% MVC were used. Significant differences in the initial values and rates of change of muscle fibre conduction velocity were found only at 60% MVC. 300 Hz vibration did not induce any peripheral changes as demonstrated by the lack of differences when fatigue was electrically induced. Differences were found only when the muscle was voluntarily fatigued at 60% MVC suggesting a modification in the centrally driven motor unit recruitment order, and interpreted as an adaptive response to the reiteration of the vibratory conditioning.

  2. Modified Pippard relationship describing the Raman frequency shifts ...

    Indian Academy of Sciences (India)

    1/)( /) for the rotatory lattice (librational) mode in ammonia solid II near its melting point. We have used our calculated Raman frequencies of this mode for pressures of 3.65, 5.02 and 6.57 kbars for this crystalline system. The values of ...

  3. Non-linear Vibration of Oscillation Systems using Frequency-Amplitude Formulation

    DEFF Research Database (Denmark)

    Fereidoon, A.; Ghadimi, M.; Barari, Amin

    2012-01-01

    In this paper we study the periodic solutions of free vibration of mechanical systems with third and fifthorder nonlinearity for two examples using He’s Frequency Amplitude Formulation (HFAF).The effectiveness and convenience of the method is illustrated in these examples. It will be shown...... that the solutions obtained with current method have a fabulous conformity with those achieved from time marching solution. HFAF is easy with powerful concepts and the high accuracy, so it can be found widely applicable in vibrations, especially strong nonlinearity oscillatory problems....

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-09-01

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

  5. In vivo measurement of basilar membrane vibration in the unopened chinchilla cochlea using high frequency ultrasound.

    Science.gov (United States)

    Landry, Thomas G; Bance, Manohar L; Leadbetter, Jeffrey; Adamson, Robert B; Brown, Jeremy A

    2017-06-01

    The basilar membrane and organ of Corti in the cochlea are essential for sound detection and frequency discrimination in normal hearing. There are currently no methods used for real-time high resolution clinical imaging or vibrometry of these structures. The ability to perform such imaging could aid in the diagnosis of some pathologies and advance understanding of the causes. It is demonstrated that high frequency ultrasound can be used to measure basilar membrane vibrations through the round window of chinchilla cochleas in vivo. The basic vibration characteristics of the basilar membrane agree with previous studies that used other methods, although as expected, the sensitivity of ultrasound was not as high as optical methods. At the best frequency for the recording location, the average vibration velocity amplitude was about 4 mm/s/Pa with stimulus intensity of 50 dB sound pressure level. The displacement noise floor was about 0.4 nm with 256 trial averages (5.12 ms per trial). Although vibration signals were observed, which likely originated from the organ of Corti, the spatial resolution was not adequate to resolve any of the sub-structures. Improvements to the ultrasound probe design may improve resolution and allow the responses of these different structures to be better discriminated.

  6. The influence of high-frequency vibrations on derailment stability coefficient of cars at wheel flange climbing on the rail

    Directory of Open Access Journals (Sweden)

    N. Bezrukavyy

    2013-08-01

    Full Text Available Purpose. Taking into account the traffic safety priority on the railway transport the search of factors promoting increase of derailment stability coefficient is an actual task. Purpose of the paper is the influence researches of the high-frequency vibrations on the train traffic safety parameter. In this case the special form of the wheel rim, at which its rigidity changes according to the harmonious law, was considered as a source of vibrations. Methodology. For the analysis of the vibration influence on the change of friction coefficient values the methods of so called vibrational mechanics were used. For determination of vibration amplitudes through moving the wheel flange points the finite-elements method was also used in the paper. Findings. During calculations it was established that the derailment stability coefficient to a great extent depends on the friction coefficient between wheel and rail. The paper shows that the friction coefficient in turn is influenced by the high-frequency vibrations. The form of the wheel rim was considered as a vibration source and the parameters characterizing vibration were calculated. It was given the quantitative estimation of the friction coefficient change under the vibration influence. It was also scientifically based the high-frequency vibration influence on the derailment stability coefficient. Originality. The paper proved the possibility of high-frequency vibration influence on the derailment stability coefficient. The studies theoretically substantiated the traffic safety increase in the presence of vibrations in the contact area of the wheel flange with the rail caused by special form of the wheel disc. Practical value. It is shown that the use of undulating wheel disc form do not constitute a threat to the traffic safety, and the availability of high-frequency vibration can reduce the derailment probability.

  7. Elastic Metamaterial Insulator for Broadband Low-Frequency Flexural Vibration Shielding

    Science.gov (United States)

    Oh, Joo Hwan; Qi, Shuibao; Kim, Yoon Young; Assouar, Badreddine

    2017-11-01

    Achieving stop band over broadband at low-frequency range has remained a great scientific challenge in spite of various efforts made using metamaterials or other technologies. In this work, we propose an idea that creates a stop band for broadband at low-frequency range. The dual mechanism of shear stiffening and rotation softening is initiated here to achieve a broad stop band at low-frequency range. Through analytical, numerical, and experimental studies, we reveal the underlying physical mechanism and confirm the effectiveness of this metamaterial on vibration shielding for flexural elastic wave covering 235 to 4520 Hz. This work opens an avenue for the development of elastic metamaterials with performance and functionalities that are highly desirable in many fields such as vibration shielding.

  8. Coupled analysis of multi-impact energy harvesting from low-frequency wind induced vibrations

    Science.gov (United States)

    Zhu, Jin; Zhang, Wei

    2015-04-01

    Energy need from off-grid locations has been critical for effective real-time monitoring and control to ensure structural safety and reliability. To harvest energy from ambient environments, the piezoelectric-based energy-harvesting system has been proven very efficient to convert high frequency vibrations into usable electrical energy. However, due to the low frequency nature of the vibrations of civil infrastructures, such as those induced from vehicle impacts, wind, and waves, the application of a traditional piezoelectric-based energy-harvesting system is greatly restrained since the output power drops dramatically with the reduction of vibration frequencies. This paper focuses on the coupled analysis of a proposed piezoelectric multi-impact wind-energy-harvesting device that can effectively up-convert low frequency wind-induced vibrations into high frequency ones. The device consists of an H-shape beam and four bimorph piezoelectric cantilever beams. The H-shape beam, which can be easily triggered to vibrate at a low wind speed, is originated from the first Tacoma Narrows Bridge, which failed at wind speeds of 18.8 m s-1 in 1940. The multi-impact mechanism between the H-shape beam and the bimorph piezoelectric cantilever beams is incorporated to improve the harvesting performance at lower frequencies. During the multi-impact process, a series of sequential impacts between the H-shape beam and the cantilever beams can trigger high frequency vibrations of the cantilever beams and result in high output power with a considerably high efficiency. In the coupled analysis, the coupled structural, aerodynamic, and electrical equations are solved to obtain the dynamic response and the power output of the proposed harvesting device. A parametric study for several parameters in the coupled analysis framework is carried out including the external resistance, wind speed, and the configuration of the H-shape beam. The average harvested power for the piezoelectric cantilever

  9. Occurrence of fatigue induced by a whole-body vibration session is not frequency dependent.

    Science.gov (United States)

    Zory, Raphael F; Raphael, Zory F; Aulbrook, Wesley; Wesley, Aulbrook; Keir, Daniel A; Daniel, Keir A; Serresse, Olivier; Olivier, Serresse

    2013-09-01

    The aim of this study was to determine whether neuromuscular adaptations (magnitude and location) induced by isometric exercise performed on an oscillating platform are dependent on whole-body vibration (WBV) frequency. Eleven young men performed 4 separate fatigue sessions of static squatting exercise at 3 frequencies of WBV (V20, V40, and V60) and 1 session without vibration (V0). Isometric torque and electromyographic activity of the vastus lateralis, rectus femoris, and biceps femoris were recorded during maximal voluntary and evoked contractions of the knee extensor muscles before and after each fatigue session to examine both peripheral and central adaptations. Isometric torque decreased significantly after each of the 4 frequency sessions (V0: -9.4 ± 6.1%, p = 0.003; V20: -8.1 ± 9.9%, p = 0.010; V40: -11.9 ± 12.7%, p = 0.011; and V60: -7.8 ± 9.2%, p = 0.001, respectively), but this reduction was not significantly different between frequencies. The torque produced by evoked contraction significantly decreased from pre-exercise values after each session (V0: -14.9 ± 15.6%, p = 0.012; V20: -15.8 ± 16.4%, p = 0.010; V40: -21.0 ± 14.3%, p = 0.004; and V60: -17.3 ± 11.6%, p = 0.005, respectively); however, there was no effect of vibration frequency. In both conditions, the maximal voluntary contraction torque reduction observed was mainly attributable to peripheral fatigue and was not because of central modifications of the neuromuscular system. The present study demonstrates that the frequency of vibration does not significantly influence the magnitude and location of neuromuscular fatigue, suggesting that adding WBV to static squat exercise (on a vertically oscillating platform) does not provide an additional training stimulus.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Dezhi; Liu, Yixuan, E-mail: xuan61x@163.com; Guo, Zhanshe; Fan, Shangchun [School of Instrument Science and Opto-electronics Engineering, Beihang University, Beijing 100191 (China); Zhao, Xiaomeng [Laser Medicine Laboratory, Institute of Biomedical Engineering, Chinese Academy of medical Sciences and Peking Union Medical College, Tianjin 300192 (China)

    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.

  11. Hyperfine contributions to spin-exchange frequency shifts in the hydrogen maser

    NARCIS (Netherlands)

    Verhaar, B.J.; Koelman, J.M.V.A.; Stoof, H.T.C.; Luiten, O.J.; Crampton, S.B.

    1987-01-01

    We have rigorously included hyperfine interactions during electron-spin-exchange collisions between ground state hydrogen atoms. We predict additional frequency shifts which are not compensated for by the usual methods of tuning maser cavities. These shifts are large compared to the potential

  12. Influence of Two Photon Absorption on Soliton Self-Frequency Shift

    DEFF Research Database (Denmark)

    Steffensen, Henrik; Rottwitt, Karsten; Jepsen, Peter Uhd

    2011-01-01

    The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect.......The creation of mid-infrared supercontinua necessitates the use of soft-glass fibers. However, some materials, like chalcogenide, have a substantial two photon absorption. We introduce a model for soliton self-frequency shift that successfully includes this effect....

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

    Science.gov (United States)

    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.

  14. Gigantic blue shift of the H-Ar stretch vibration in pi hydrogen-bonded C(2)H(2)...HArCCF complex.

    Science.gov (United States)

    Cheng, Jianbo; Wang, Yilei; Li, Qingzhong; Liu, Zhenbo; Li, Wenzuo; Gong, Baoan

    2009-04-30

    Quantum chemical calculations have been performed to study the structure and properties of the pi hydrogen-bonded complex formed between acetylene and HArCCF at the MP2/6-311++G(2d,2p) level. The C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes were also studied for comparison with the C(2)H(2)...HArCCF complex. The basis set superposition errors (BSSE)-counterpoise corrected potential-energy surface (PES) has a larger influence on the structure and properties of the C(2)H(2)...HArCCF complex than those of the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes. The C(2)H(2)...HArCCF complex exhibits a very large harmonic vibrational frequency blue shift of 574 cm(-1) for the H-Ar stretch, whereas the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes exhibit a small red shift of 35 and 47 cm(-1) for the H-C stretch, respectively; upon complexation the IR intensity decreases in the former, whereas it increases in the latter. The origin of the frequency shift and nature of the hydrogen bond in these complexes have been unveiled with the natural bond orbital analysis and energy decomposition.

  15. Signature Analysis and Discrimination Method of Preceded Frequency-shift False Target

    Directory of Open Access Journals (Sweden)

    Feng Dejun

    2017-08-01

    Full Text Available Due to the effect of range-Doppler coupling between the time delay and shifted frequency of an LFM waveform, LFM radar is particularly susceptible to shift frequency jamming. A new deceptive jamming method, the Preceded Frequency-shift False Target (PFFT, has a similar signature to real radar targets, which indicates that conventional ECCM, such as leading-edge tracking, could be invalid when countering it. In this paper, the basic principle of PFFT is introduced and its signatures analyzed. Then, a new method for discrimination between a preceded false target generated by Digital Radio Frequency Memory (DRFM and a radar target is proposed. By comparing the echo arrival time at the radar receiver front end with that estimated after a matched filter, the new method can extract the frequency modulation jamming signature and make a correct judgment. Simulation results are presented to verify the validity of the proposed method.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Nian; Yang, Jin, E-mail: yangjin@cqu.edu.cn; Yu, Qiangmo; Zhao, Jiangxin; Liu, Jun; Wen, Yumei; Li, Ping [Department of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China)

    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.

  19. Phase-shift cavity ring-down spectroscopy using mid-IR light from a difference frequency generation PPLN waveguide.

    Science.gov (United States)

    Grilli, Roberto; Ciaffoni, Luca; Orr-Ewing, Andrew J

    2010-05-01

    Approximately 200 microW of mid-infrared (mid-IR) light around 3081 cm(-1), produced by difference frequency generation (DFG) in a periodically poled lithium niobate crystal waveguide, has been used for phase-shift cavity ring-down spectroscopy measurements. The overlapping (12)C(2)H(4) (R)P(0)(14) and (P)R(6)(10) and (12)CH(2) (13)CH(2) (P)Q(3)(10) rotational lines of the nu(9) fundamental ethene vibrational band at 3081.0016 cm(-1) were probed in proof-of-principle experiments, and ethene detection was demonstrated with a minimum absorption coefficient of 1.4 x 10(-7) cm(-1) (approximately 4 min acquisition time). The compact DFG system, with a >35 cm(-1) tuning range, has a considerable potential for use in trace gas detection and in molecular spectroscopy.

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

    Science.gov (United States)

    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

  1. Health State Monitoring of Bladed Machinery with Crack Growth Detection in BFG Power Plant Using an Active Frequency Shift Spectral Correction Method.

    Science.gov (United States)

    Sun, Weifang; Yao, Bin; He, Yuchao; Chen, Binqiang; Zeng, Nianyin; He, Wangpeng

    2017-08-09

    Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG) in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information) belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages.

  2. Health State Monitoring of Bladed Machinery with Crack Growth Detection in BFG Power Plant Using an Active Frequency Shift Spectral Correction Method

    Directory of Open Access Journals (Sweden)

    Weifang Sun

    2017-08-01

    Full Text Available Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages.

  3. Development of Low Frequency Vibration Method of Direct-Write Deposition Relevant to Layer Manufacturing Application

    Directory of Open Access Journals (Sweden)

    Susilo Widyanto

    2010-10-01

    Full Text Available The research of deposition process is the first step in development process of multi materials selective laser sintering. The deposition process enables to settle multi materials powder in horizontal formation on one layer. In this research we use low frequency (70 - 200Hz to vibrate a hopper nozzle in which powder is settled. The research method consists of two steps, the first step is to determine flow-ability parameters and the second is to join flow ability parameter with other parameters such that the line width can be controlled. The results show that the line width depends on uniformity of particle size, particle size, frequency of vibration, deposition gap, particle shape and feed-rate of hopper-nozzle.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Shengwei He

    2017-01-01

    Full Text Available 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 k-B ligan, and pre-collagen type 1 a 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 k-B ligand, and pre-collagen type 1 a 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.

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

    Directory of Open Access Journals (Sweden)

    Bo Zhu

    2016-03-01

    Full Text Available 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.

  7. Algorithm for the calculation of vibration inherent frequencies bending from two-shafts transmission

    Directory of Open Access Journals (Sweden)

    Grigore Jan-Cristian

    2017-01-01

    Full Text Available The operation of the speed shaft transmissions at or near the natural frequency of the pulses at the resonance phenomenon leads to bending, when the amplitude of the oscillations increases sharply, causing deterioration or complete destruction thereof. To avoid system resonance operation is necessary to know the most accurate values its pulsations and taking appropriate constructive measures to avoid overlapping with disturbing frequency harmonics (operating speeds.This paper presents an algorithm for calculating the pulsation and vibration modes in bending, and based on numerical simulations performed on a real two-shafts transmission and will draw conclusions drawn diagrams.

  8. Conformational energetics and low-frequency vibrations of cyclohexene and its oxygen analogs

    Science.gov (United States)

    Ocola, Esther J.; Brito, Teresa; McCann, Kathleen; Laane, Jaan

    2010-08-01

    Ab initio and DFT calculations with MP2/cc-pVTZ and B3LYP/cc-pVTZ basis sets have been carried out for cyclohexene and four of its oxygen analogs. All of the molecules possess a twisted structure while the bent forms represent saddle points in two-dimensional surfaces. The structures, relative energies, and frequencies for the lowest energy vibrations of the twisted, bent, and planar forms were calculated and compared to experimental results. The calculated results agree very well with the microwave data but the computed barriers are somewhat less than those based on low-frequency infrared data.

  9. Bi-resonant structure with piezoelectric PVDF films for energy harvesting from random vibration sources at low frequency

    DEFF Research Database (Denmark)

    Liang, Shanshan; Crovetto, Andrea; Peng, Zhuoteng

    2016-01-01

    and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity...

  10. Effect of vibration frequency on microstructure and performance of high chromium cast iron prepared by lost foam casting

    Directory of Open Access Journals (Sweden)

    Wen-qi Zou

    2016-07-01

    Full Text Available In the present research, high chromium cast irons (HCCIs were prepared using the lost foam casting (LFC process. To improve the wear resistance of the high chromium cast irons (HCCIs, mechanical vibration was employed during the solidification of the HCCIs. The effects of vibration frequency on the microstructure and performance of the HCCIs under as-cast, as-quenched and as-tempered conditions were investigated. The results indicated that the microstructures of the LFC-produced HCCIs were refined due to the introduction of mechanical vibration, and the hardness was improved compared to that of the alloy without vibration. However, only a slight improvement in hardness was found in spite of the increase of vibration frequency. In contrast, the impact toughness of the as-tempered HCCIs increased with an increase in the vibration frequency. In addition, the wear resistance of the HCCIs was improved as a result of the introduction of vibration and increased with an increase in the vibration frequency.

  11. Comparison of resonance frequencies between normal and tangential vibration modes of graphene-nanoribbon-resonators.

    Science.gov (United States)

    Kwon, Oh Kuen; Hwang, Ho Jung; Park, Jungcheol

    2013-12-01

    We investigate tunable graphene-nanoribbon (GNR)-resonators actuated in the tangential direction, and their properties are compared to those actuated in the normal direction, via classical molecular dynamics simulations. These GNR-resonators can be tuned both by the initial strain and the gate. The relationships between the frequency-versus-gate and the initial strain in this work are in good agreement with those in previous experimental works. With increasing initial strain, the resonance frequencies are greatly upshifted, whereas the tunable ranges in frequency are greatly decreased. The tunability in the dynamic operating range decreases with increasing initial strain. For very small strains, the GNR-resonators have large dynamic operating ranges in the normal vibration mode, and for large strains, the GNR-resonators have higher operating frequencies in the tangential vibration mode. The resonance frequencies are estimated by a classical continuum model, with tension acting on the GNR-resonators consisting of both initial tension by initial strain and induced tension by gate actuating.

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Anelise Sonza

    2015-01-01

    Full Text Available 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.

  14. Vibration Frequencies Extraction of the Forth Road Bridge Using High Sampling GPS Data

    Directory of Open Access Journals (Sweden)

    Jian Wang

    2016-01-01

    Full Text Available This paper proposes a scheme for vibration frequencies extraction of the Forth Road Bridge in Scotland from high sampling GPS data. The interaction between the dynamic response and the ambient loadings is carefully analysed. A bilinear Chebyshev high-pass filter is designed to isolate the quasistatic movements, the FFT algorithm and peak-picking approach are applied to extract the vibration frequencies, and a GPS data accumulation counter is suggested for real-time monitoring applications. To understand the change in the structural characteristics under different loadings, the deformation results from three different loading conditions are presented, that is, the ambient circulation loading, the strong wind under abrupt wind speed change, and the specific trial with two 40 t lorries passing the bridge. The results show that GPS not only can capture absolute 3D deflections reliably, but also can be used to extract the frequency response accurately. It is evident that the frequencies detected using the filtered deflection time series in different direction show quite different characteristics, and more stable results can be obtained from the height displacement time series. The frequency responses of 0.105 and 0.269 Hz extracted from the lateral displacement time series correlate well with the data using height displacement time series.

  15. Investigation of the frequency shift of a SAD circuit loop and the internal micro-cantilever in a gas sensor.

    Science.gov (United States)

    Guan, Liu; Zhao, Jiahao; Yu, Shijie; Li, Peng; You, Zheng

    2010-01-01

    Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF) and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF). A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD) circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficient α related to the two frequency shifts is confirmed.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2014-11-17

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

  20. Investigation of the Frequency Shift of a SAD Circuit Loop and the Internal Micro-Cantilever in a Gas Sensor

    Directory of Open Access Journals (Sweden)

    Zheng You

    2010-07-01

    Full Text Available Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF. A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed.Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF. A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed.

  1. Nonlinear modification of the laser noise power spectrum induced by a frequency-shifted optical feedback

    CERN Document Server

    Lacot, Eric; Girardeau, Vadim; Hugon, Olivier; Jacquin, Olivier

    2016-01-01

    In this article, we study the non-linear coupling between the stationary (i.e. the beating modulation signal) and transient (i.e. the laser quantum noise) dynamics of a laser subjected to frequency shifted optical feedback. We show how the noise power spectrum and more specifically the relaxation oscillation frequency of the laser are modified under different optical feedback condition. Specifically we study the influence of (i) the amount of light returning to the laser cavity and (ii) the initial detuning between the frequency shift and intrinsic relaxation frequency. The present work shows how the relaxation frequency is related to the strength of the beating signal and the shape of the noise power spectrum gives an image of the Transfer Modulation Function (i.e. of the amplification gain) of the nonlinear-laser dynamics.The theoretical predictions, confirmed by numerical resolutions, are in good agreements with the experimental data.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  4. Effects of GPR antenna configuration on subpavement drain detection based on the frequency-shift phenomenon

    Science.gov (United States)

    Bai, Hao; Sinfield, Joseph V.

    2017-11-01

    The water and clay content of subsurface soil can significantly influence the detection results obtained from ground penetrating radar (GPR). Due to the variation of the material properties underground, the center frequency of transmitted GPR signals shifts to a lower range as wave attenuation increases. Examination of wave propagation in the subsurface employing an attenuation filter based on a linear system model shows that received GPR signals will be shifted to lower frequencies than those originally transmitted. The amount of the shift is controlled by a wave attenuation factor, which is determined by the dielectric constant, electric conductivity, and magnetic susceptibility of the transmitted medium. This paper introduces a receiver-transmitter-receiver dual-frequency configuration for GPR that employs two operational frequencies for a given test - one higher and one slightly lower - to take advantage of this phenomenon to improve subpavement drain detection results. In this configuration, the original signal is transmitted from the higher frequency transmitter. After traveling through underground materials, the signal is received by two receivers with different frequencies. One of the receivers has the same higher center frequency as the transmitter, and the other receiver has a lower center frequency. This configuration can be expressed as Rx(low-frequency)-Tx(high-frequency)-Rx(high-frequency) and was applied in both laboratory experiments and field tests. Results are analyzed in the frequency domain to evaluate and compare the properties of the signal obtained by both receivers. The laboratory experiment used the configuration of Rx(400MHz)-Tx(900MHz)-Rx(900MHz). The field tests, in addition to the configuration used in the lab tests, employed another configuration of Rx(270MHz)-Tx(400MHz)-Rx(400MHz) to obtain more information about this phenomenon. Both lab and field test results illustrate the frequency-shift phenomenon described by theoretical

  5. Hyperfine frequency shift of atomic hydrogen in the presence of helium buffer gas

    Energy Technology Data Exchange (ETDEWEB)

    Jochemsen, R.; Berlinsky, A.J. (British Columbia Univ., Vancouver (Canada). Dept. of Physics)

    1982-02-01

    A quantum mechanical thermal average is performed to obtain the temperature dependence of the hyperfine frequency shift (HFS) of hydrogen atoms in the presence of He buffer gas. The calculations are based on existing ab initio calculations of the hyperfine frequency shift as a function of internuclear separation and of the interatomic potential. We find that the HFS changes sign at fairly low temperature and has a small negative value at T = 1 K in agreement with recent measurements. The overall temperature dependence is shown to be quite sensitive to the interatomic potential.

  6. Accurate measurements of transition frequencies and isotope shifts of laser-trapped francium.

    Science.gov (United States)

    Sanguinetti, S; Calabrese, R; Corradi, L; Dainelli, A; Khanbekyan, A; Mariotti, E; de Mauro, C; Minguzzi, P; Moi, L; Stancari, G; Tomassetti, L; Veronesi, S

    2009-04-01

    An interferometric method is used to improve the accuracy of the 7S-7P transition frequencies of three francium isotopes by 1 order of magnitude. The deduced isotope shifts for 209-211Fr confirm the ISOLDE data. The frequency of the D2 transition of 212Fr--the accepted reference for all Fr isotope shifts--is revised, and a significant difference with the ISOLDE value is found. Our results will be a benchmark for the accuracy of the theory of Fr energy levels, a necessary step to investigate fundamental symmetries.

  7. Wide tunable shift of the reflection band in dual frequency cholesteric liquid crystals.

    Science.gov (United States)

    Oton, Eva; Netter, Estelle

    2017-06-12

    Technologies featuring external control of reflected and transmitted light are lately being explored for a wide range of optical and photonic applications. Yet, the options for spectral band tuning are scarce, especially if dynamic control of either reflected or transmitted light is required. In this work we demonstrate a tunable device capable of shifting the reflected light spectrum of an impinging light using dual frequency cholesteric liquid crystals. Modulating the frequency of the applied signal, the Bragg reflection can be dynamically shifted over a wide spectral range and also switched off. This feature can be applied to color filters, augmented reality, multi-color lasers or tunable windows.

  8. Energy Expenditure and Substrate Oxidation in Response to Side-Alternating Whole Body Vibration across Three Commonly-Used Vibration Frequencies.

    Directory of Open Access Journals (Sweden)

    Elie-Jacques Fares

    Full Text Available 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.

  9. Analytical Expressions for Frequency and Buckling of Large Amplitude Vibration of Multilayered Composite Beams

    Directory of Open Access Journals (Sweden)

    R. A. Jafari-Talookolaei

    2011-01-01

    Full Text Available The aim of this paper is to present analytical and exact expressions for the frequency and buckling of large amplitude vibration of the symmetrical laminated composite beam (LCB with simple and clamped end conditions. The equations of motion are derived by using Hamilton's principle. The influences of axial force, Poisson effect, shear deformation, and rotary inertia are taken into account in the formulation. First, the geometric nonlinearity based on the von Karman's assumptions is incorporated in the formulation while retaining the linear behavior for the material. Then, the displacement fields used for the analysis are coupled using the equilibrium equations of the composite beam. Substituting this coupled displacement fields in the potential and kinetic energies and using harmonic balance method, we obtain the ordinary differential equation in time domain. Finally, applying first order of homotopy analysis method (HAM, we get the closed form solutions for the natural frequency and deflection of the LCB. A detailed numerical study is carried out to highlight the influences of amplitude of vibration, shear deformation and rotary inertia, slenderness ratios, and layup in the case of laminates on the natural frequency and buckling load.

  10. Vibrational frequencies of anti-diabetic drug studied by terahertz time-domain spectroscopy

    Science.gov (United States)

    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.

  11. A piezoelectric pulse generator for low frequency non-harmonic vibration

    Science.gov (United States)

    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.

  12. Non-Seismology Seismology: Using QuakeCatchers to Analyze the Frequency of Bridge Vibrations

    Science.gov (United States)

    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.

  13. An approach to compatible multiple nonlinear vibrational spectroscopy measurements using a commercial sum frequency generation system.

    Science.gov (United States)

    Ye, Shuji; Wei, Feng

    2011-06-21

    In this paper, we designed a compatible multiple nonlinear vibrational spectroscopy system that can be used for recording infrared-visible sum frequency generation vibrational spectra (SFG) and infrared-infrared-visible three-pump-field four-wave-mixing (IIV-TPF-FWM) spectra using a commercial EKSPLA SFG system. This is the first time IIV-TPF-FWM signals were obtained using picosecond laser pulses. We have applied this compatible system to study the surface and vibrational structures of riboflavin molecules (also known as vitamin B2). The SFG spectra of eight polarization combinations have non-vanishing signals. The signals with incoming s-polarized IR are relatively weaker than the signals with incoming p-polarized IR. Under the double resonant conditions, the SFG signals of the conjugated tricyclic ring are greatly enhanced. For the IIV-TPF-FWM spectra with incoming p-polarized IR, only the sspp and pppp polarization combinations have non-vanishing signals. The IIV-TPF-FWM spectra show a very strong peak at 1585 cm(-1) that is mainly dominated by the N(5)-C(4a) stretch. The method developed in this study will be helpful for researchers, either using a home-built or commercial (EKSPLA) SFG system, to obtain independent and complementary measurements for SFG spectroscopy and more detailed structural information of interfacial molecules.

  14. Time and frequency characteristics of temporary threshold shifts caused by pure tone exposures

    DEFF Research Database (Denmark)

    Ordoñez, Rodrigo Pizarro; Hammershøi, Dorte

    2011-01-01

    The time-frequency characteristics of Temporary Threshold Shifts (TTS) caused by pure tones were determined using the Békésy audiometric method with narrow-band noise of short duration as the probe stimuli. Two experiments were done using exposures of 3 min at 100 dB above threshold. In the first...

  15. Matrix effect on vibrational frequencies: Experiments and simulations for HCl and HNgCl (Ng = Kr and Xe)

    Energy Technology Data Exchange (ETDEWEB)

    Kalinowski, Jaroslaw; Räsänen, Markku; Lignell, Antti; Khriachtchev, Leonid, E-mail: leonid.khriachtchev@helsinki.fi [Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 (Finland); Gerber, R. Benny [Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 (Finland); Department of Physical Chemistry, Hebrew University, Jerusalem 91904, Israel and Department of Chemistry, University of California, Irvine, California 92697 (United States)

    2014-03-07

    We study the environmental effect on molecules embedded in noble-gas (Ng) matrices. The experimental data on HXeCl and HKrCl in Ng matrices is enriched. As a result, the H−Xe stretching bands of HXeCl are now known in four Ng matrices (Ne, Ar, Kr, and Xe), and HKrCl is now known in Ar and Kr matrices. The order of the H−Xe stretching frequencies of HXeCl in different matrices is ν(Ne) < ν(Xe) < ν(Kr) < ν(Ar), which is a non-monotonous function of the dielectric constant, in contrast to the “classical” order observed for HCl: ν(Xe) < ν(Kr) < ν(Ar) < ν(Ne). The order of the H−Kr stretching frequencies of HKrCl is consistently ν(Kr) < ν(Ar). These matrix effects are analyzed theoretically by using a number of quantum chemical methods. The calculations on these molecules (HCl, HXeCl, and HKrCl) embedded in single Ng{sup ′} layer cages lead to very satisfactory results with respect to the relative matrix shifts in the case of the MP4(SDQ) method whereas the B3LYP-D and MP2 methods fail to fully reproduce these experimental results. The obtained order of frequencies is discussed in terms of the size available for the Ng hydrides in the cages, probably leading to different stresses on the embedded molecule. Taking into account vibrational anharmonicity produces a good agreement of the MP4(SDQ) frequencies of HCl and HXeCl with the experimental values in different matrices. This work also highlights a number of open questions in the field.

  16. Accompanying the frequency shift of the nonlinear resonance of a gas bubble using a dual-frequency excitation.

    Science.gov (United States)

    Guédra, Matthieu; Inserra, Claude; Gilles, Bruno

    2017-09-01

    An asymptotic method is applied to analyze the nonlinear oscillations of a gas bubble driven by a dual-frequency excitation. More specifically, the latter is considered as a combination of two neighboring, incommensurate frequencies and is treated as a nonstationary excitation. This implies that both amplitude and phase of the bubble response are slowly oscillating at the time scale of the frequency difference, thus leading to a regime of aperiodic oscillations. The approximate solution is successfully compared with numerical simulations and reveals the possibility of achieving larger bubble response amplitude compared to the monofrequency excitation for sufficiently high driving pressure and specific values of the frequency difference. The asymptotic theory captures the generation of additional spectral components coming from the nonlinear mixing of both driving frequencies. This mechanism is responsible for a global enhancement of the dual-frequency bubble response as it enables an energy transfer towards more efficient components which are successively tuned with the nonlinearly shifted resonance frequency of the bubble, thus limiting the saturation due to softening. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Damping and frequency shift in the oscillations of two colliding Bose-Einstein condensates

    Science.gov (United States)

    Modugno, M.; Fort, C.; Maddaloni, P.; Minardi, F.; Inguscio, M.

    2001-12-01

    We have investigated the center-of-mass oscillations of a 87Rb Bose-Einstein condensate in an elongated magneto-static trap. We start from a trapped condensate and we transfer part of the atoms to another trapped level, by applying a radio-frequency pulse. The new condensate is produced far from its equilibrium position in the magnetic potential, and periodically collides with the parent condensate. We discuss how both the damping and the frequency shift of the oscillations are affected by the mutual interaction between the two condensates, in a wide range of trapping frequencies. The experimental data are compared with the prediction of a mean-field model.

  18. From frequency to time-average-frequency a paradigm shift in the design of electronic system

    CERN Document Server

    Xiu, Liming

    2015-01-01

    Written in a simple, easy to understand style, this book will teach PLL users how to use new clock technology in their work in order to create innovative applications.       Investigates the clock frequency concept from a different perspective--at an application level       Teaches engineers to use this new clocking technology to create innovations in chip/system level, through real examples extracted from commercial products  

  19. Low resonance frequency vibration affects strength of paretic and non-paretic leg differently in patients with stroke.

    Science.gov (United States)

    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.

  20. Comparative Study of Time-Frequency Decomposition Techniques for Fault Detection in Induction Motors Using Vibration Analysis during Startup Transient

    Directory of Open Access Journals (Sweden)

    Paulo Antonio Delgado-Arredondo

    2015-01-01

    Full Text Available Induction motors are critical components for most industries and the condition monitoring has become necessary to detect faults. There are several techniques for fault diagnosis of induction motors and analyzing the startup transient vibration signals is not as widely used as other techniques like motor current signature analysis. Vibration analysis gives a fault diagnosis focused on the location of spectral components associated with faults. Therefore, this paper presents a comparative study of different time-frequency analysis methodologies that can be used for detecting faults in induction motors analyzing vibration signals during the startup transient. The studied methodologies are the time-frequency distribution of Gabor (TFDG, the time-frequency Morlet scalogram (TFMS, multiple signal classification (MUSIC, and fast Fourier transform (FFT. The analyzed vibration signals are one broken rotor bar, two broken bars, unbalance, and bearing defects. The obtained results have shown the feasibility of detecting faults in induction motors using the time-frequency spectral analysis applied to vibration signals, and the proposed methodology is applicable when it does not have current signals and only has vibration signals. Also, the methodology has applications in motors that are not fed directly to the supply line, in such cases the analysis of current signals is not recommended due to poor current signal quality.

  1. Energy Expenditure and Substrate Oxidation in Response to Side-Alternating Whole Body Vibration across Three Commonly-Used Vibration Frequencies.

    Science.gov (United States)

    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%, pvibration. 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).

  2. Frequency shift and hysteresis suppression in contact-mode AFM using contact stiffness modulation

    Directory of Open Access Journals (Sweden)

    Belhaq M.

    2012-07-01

    Full Text Available In this paper the frequency response shift and hysteresis suppression of contact-mode atomic force microscopy is investigated using parametric modulation of the contact stiffness. Based on the Hertzian contact theory, a lumped single degree of freedom oscillator is considered for modeling the cantilever dynamics contact-mode atomic force microscopy. We use the technique of direct partition of motion and the method of multiple scales to obtain, respectively, the slow dynamic and the corresponding slow flow of the system. As results, this study shows that the amplitude of the contact stiffness modulation has a significant effect on the frequency response. Specifically, increasing the amplitude of the stiffness modulation suppresses hysteresis, decreases the peak amplitude and produces shifts towards higher and lower frequencies.

  3. Fast vibrational calculation of anharmonic OH-stretch frequencies for two low-energy noradrenaline conformers

    Science.gov (United States)

    Benoit, David M.

    2008-12-01

    We introduce a new reduced-coupling technique to accelerate direct calculations of a selected number of vibrational frequencies in large molecular systems. Our method combines the advantages of the single-to-all correlation-corrected vibrational self-consistent field (STA-CC-VSCF) approach [D. M. Benoit, J. Chem. Phys. 125, 244110 (2006)] with those of the fast-CC-VSCF technique [D. M. Benoit, J. Chem. Phys. 120, 562 (2004)] and allows the ab initio calculation of only the relevant parts of the required potential energy surface (PES). We demonstrate, using a set of five aliphatic alcohol molecules, that the new fast-STA-CC-VSCF method is accurate and leads to very substantial time gains for the computations of the PES. We then use the fast-STA-CC-VSCF method to accelerate the computation of the OH-stretch and NH-stretch frequencies of the two lowest-energy conformers of noradrenaline, namely, AG1a and GG1a. Our new approach enables us to run the calculation 89 times faster than the standard CC-VSCF technique and makes it possible to use a high-level MP2/TZP description of the PES. We demonstrate that the influence of the strong mode-mode couplings is crucial for a realistic description of the particular OH-stretch vibrational signature of each conformer. Finally, of the two possible low-energy conformers, we identify AG1a as the one most likely to have been observed in the experiments of Snoek et al. [Mol. Phys. 101, 1239 (2003)].

  4. Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Pengwei, E-mail: lipengwei@tyut.edu.cn; Wang, Yanfen; Luo, Cuixian; Li, Gang; Hu, Jie; Zhang, Wendong [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Liu, Ying [MicroNano System Research Center of College of Information Engineering and Key Lab of Advanced Transducers and Intelligent Control System of the Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China); Liu, Wei [Baicheng Ordnance Test Center of China, Baicheng 137000, Jilin (China)

    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.

  5. Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure

    Directory of Open Access Journals (Sweden)

    Pengwei Li

    2015-04-01

    Full Text Available 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.

  6. Natural frequency and vibration analysis of jacket type foundation for offshore wind power

    Science.gov (United States)

    Hung, Y.-C.; Chang, Y.-Y.; Chen, S.-Y.

    2017-12-01

    There are various types of foundation structure for offshore wind power, engineers may assess the condition of ocean at wind farm, and arrange the transportation, installation of each structure members, furthermore, considering the ability of manufacture steel structure as well, then make an optimum design. To design jacket offshore structure, unlike onshore cases, offshore structure also need to estimate the wave excitation effect. The aim of this paper is to study the difference of natural frequency between different kinds of structural stiffness and discuss the effect of different setting of boundary condition during analysis, besides, compare this value with the natural frequency of sea wave, in order to avoid the resonance effect. In this paper, the finite element analysis software ABAQUS is used to model and analyze the natural vibration behavior of the jacket structure.

  7. Delays of stimulus-frequency otoacoustic emissions and cochlear vibrations contradict the theory of coherent reflection filtering

    NARCIS (Netherlands)

    Siegel, JH; Cerka, AJ; Recio-Spinoso, A; Temchin, AN; van Dijk, P; Ruggero, MA

    2005-01-01

    When stimulated by tones, the ear appears to emit tones of its own, stimulus-frequency otoacoustic emissions (SFOAEs). SFOAEs were measured in 17 chinchillas and their group delays were compared with a place map of basilar-membrane vibration group delays measured at the characteristic frequency. The

  8. Frequency shift keying by current modulation in a MTJ-based STNO with high data rate

    Science.gov (United States)

    Ruiz-Calaforra, A.; Purbawati, A.; Brächer, T.; Hem, J.; Murapaka, C.; Jiménez, E.; Mauri, D.; Zeltser, A.; Katine, J. A.; Cyrille, M.-C.; Buda-Prejbeanu, L. D.; Ebels, U.

    2017-08-01

    Spin torque nano-oscillators are nanoscopic microwave frequency generators which excel due to their large frequency tuning range and agility for amplitude and frequency modulation. Due to their compactness, they are regarded as suitable candidates for applications in wireless communications, where cost-effective and complementary metal-oxide semiconductor-compatible standalone devices are required. In this work, we study the ability of a magnetic-tunnel-junction based spin torque nano-oscillator to respond to a binary input sequence encoded in a square-shaped current pulse for its application as a frequency-shift-keying (FSK) based emitter. We demonstrate that below the limit imposed by the spin torque nano-oscillator intrinsic relaxation frequency, an agile variation between discrete oscillator states is possible. For this kind of devices, we demonstrate FSK up to data rates of 400 Mbps, which is well suited for the application of such oscillators in wireless networks.

  9. A Large Span Crossbeam Vibration Frequencies Analysis Based on an Analogous Beam Method

    Directory of Open Access Journals (Sweden)

    Zhifeng Liu

    2013-01-01

    Full Text Available The novel method of an analogous beam is studied, which the flexural rigidity and mass per unit length correspond was described as the reciprocal of the mass per unit and the reciprocal of the flexural rigidity of the beam. It is shown that both beams possess the same natural frequencies of flexural vibration. In order to approximate calculation of these frequencies, the continuously distributed mass of the original beam is substituted for a number of concentrated masses. The analogous beam then becomes a chain of rigid links connected by pins and equipped with springs restraining the relative rotation of adjacent links. The equations of motion for the analogous beam can be solved by a procedure which consists of assuming a value for the natural frequency and calculating the deflections successively from one end of the beam to the other. Under normal circumstances, there will be a certain error, and one boundary condition will not be satisfied. The procedure is repeated with different values of the frequency until the error is removed. The method is illustrated by an example of a Crossbeam for which the fundamental frequency is found.

  10. Effect of higher frequency components and duration of vibration on bone tissue alterations in the rat-tail model

    Science.gov (United States)

    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

  11. Time-frequency analysis of DC bias vibration of transformer core on the basis of Hilbert–Huang transform

    Directory of Open Access Journals (Sweden)

    Xingmou Liu

    2016-01-01

    Full Text Available This paper presents a time–frequency analysis of the vibration of transformer under direct current (DC bias through Hilbert–Huang transform (HHT. First, the theory of DC bias for the transformer was analyzed. Next, the empirical mode decomposition (EMD process, which is the key in HHT, was introduced. The results of EMD, namely, intrinsic mode functions (IMFs, were calculated and summed by Hilbert transform(HT to obtain time-dependent series in a 2D time–frequency domain. Lastly, a test system of vibration measurement for the transformer was set up. Three direction (x, y, and z axes components of core vibration were measured. Decomposition of EMD and HHT spectra showed that vibration strength increased, and odd harmonics were produced with DC bias. Results indicated that HHT is a viable signal processing tool for transformer health monitoring.

  12. Performance Analysis of Frequency Shift Keyed Signals in a Sonar Ranging System

    Science.gov (United States)

    Kodama, Tetsuji; Nakahira, Kenji; Koyama, Yuu; Murakami, Junichi

    Pulsed ultrasonic distance measurement systems are frequently used in robotics applications, thanks to their low cost and small size. The pulse compression techniques, originally developed by radar engineers, were adopted to eliminate frequent misreadings caused by crosstalk or external ultrasound sources. High-performance computing systems for the implementation of pulse compression techniques enable reliable and accurate distance measurement. In most cases however, they significantly increase the complexity of the total system, cutting down one of the advantages of ultrasonic systems. The ultrasonic ranging using a digital polarity correlator can overcome this drawback, because the cost of realizing delay and multiplication for each point on the polarity correlation function as a parallel operation is very low. This paper presents an analysis of the binary coded frequency shift keyed signals for the ultrasonic ranging using a digital polarity correlator. The spectra of the frequency shift keyed signals have been observed to be narrow compared with the spectra of the corresponding phase shift keyed signals. This suggests the possibility of a more reliable and accurate distance measurement with the frequency shift keyed signals in terms of occupied bandwidth.

  13. CONTRIBUTIONS TO THE STUDY OF THE VIBRATIONS FREQUENCY OF THE DRILL TOOL IN THE PROCESS OF MANUFACTURING THE BRONZE MATERIALS

    Directory of Open Access Journals (Sweden)

    Cosmin-Mihai MIRIŢOIU

    2013-05-01

    Full Text Available In this paper we present the experimental testings used to study the vibration of the drill tool, during the drilling of the bronze products. We have used the experimental setup presented in Miriţoiu (2013[1]. In this paper the vibrations are analyzed during the drilling on the universal lathe machines. The main purpose of to find a correlation between the cutting speed and the frequency of the vibration by using the experimental results and the regression analysis

  14. Collective excitations in liquid DMSO : FIR spectrum, Low frequency vibrational density of states and ultrafast dipolar solvation dynamics

    OpenAIRE

    Hazra, Milan; Bagchi, Biman

    2016-01-01

    Valuable dynamical and structural information about neat liquid DMSO at ambient conditions can be obtained through study of low frequency vibrations in the far infrared (FIR), that is, terahertz regime. For DMSO, collective excitations as well as single molecule stretches and bends have been measured by different kinds of experiments such as OHD-RIKES and terahertz spectroscopy. In the present work we investigate the intermolecular vibrational spectrum of DMSO through three different computat...

  15. Recording of unexpectedly high frequency vibrations of blood vessel walls in experimental arteriovenous fistulae of rabbits using a laser vibrometer.

    Science.gov (United States)

    Stehbens, W E; Liepsch, D W; Poll, A; Erhardt, W

    1995-01-01

    Because arteriovenous fistulae are associated with a palpable thrill and an audible murmur, the vibrational activity of the blood vessel walls about experimental arteriovenous fistulae in rabbits was investigated using, for the first time, a high-resolution laser vibrometer. Frequencies of mural vibrations up to 2200 Hz were recorded at different sites about the fistulae. The relationship of this vibratory activity of blood vessel walls to physiological and pathological conditions warrants further investigation.

  16. A novel scheme for the discrete prediction of high-frequency vibration response: Discrete singular convolution-mode superposition approach

    Science.gov (United States)

    Seçgin, Abdullah; Saide Sarıgül, A.

    2009-03-01

    This study introduces a novel scheme for the discrete high-frequency forced vibration analysis based on discrete singular convolution (DSC) and mode superposition (MS) approaches. The accuracy of the DSC-MS is validated for thin beams and plates by comparing with available analytical solutions. The performance of the DSC-MS is evaluated by predicting spatial distribution and discrete frequency spectra of the vibration response of thin plates with two different boundary conditions. The frequency spectra of the time-harmonic excitation forces are in the form of ideal and band-limited white noise so that the natural modes in the frequency band are provoked. The solution exposes high-frequency response behaviour definitely. Therefore, it is hoped with this paper to contribute the studies on the treatment of uncertainties in the high-frequency design applications.

  17. Red shift of the SF6 vibration spectrum induced by the electron absorption: An ab initio study

    Directory of Open Access Journals (Sweden)

    Bin Tang

    2018-01-01

    Full Text Available As a widely used gas insulator, sulfur hexafluoride (SF6 has a large cross section for electron absorption, which may make the molecule ionized to the -1 charge state in the high-voltage environment. Using ab initio calculations, we show that the absorbed electron is located averagely on the six F atoms, occupying the antibonding level of the s-p σ bonds and increasing the S-F bond length. The ionized SF6- molecule decreases its decomposition energy to only 1.5 eV, much lower than that of the neutral molecule (4.8 eV, which can be understood according to the occupying of the antibonding orbital and thus weakening of the s-p σ bonds. The weakening of the bonds results in an obvious red shift in the vibrational modes of the ionized SF6- molecule by 120-270 cm-1, compared to those of the neutral molecule. The detailed origin of these vibrational modes is analyzed. Since the appearance of the ionized SF6- molecules is before the decomposition reaction of the SF6- molecule into low-fluoride sulfides, this method may improve the sensitivity of the defection of the partial discharge and save more time for the prevention of the insulation failure in advance.

  18. A second, low-frequency mode of vibration in the intact mammalian cochlea

    Science.gov (United States)

    Lukashkin, Andrei N.; Russell, Ian J.

    2003-03-01

    The mammalian cochlea is a structure comprising a number of components connected by elastic elements. A mechanical system of this kind is expected to have multiple normal modes of oscillation and associated resonances. The guinea pig cochlear mechanics was probed using distortion components generated in the cochlea close to the place of overlap between two tones presented simultaneously. Otoacoustic emissions at frequencies of the distortion components were recorded in the ear canal. The phase behavior of the emissions reveals the presence of a nonlinear resonance at a frequency about a half octave below that of the high-frequency primary tone. The location of the resonance is level dependent and the resonance shifts to lower frequencies with increasing stimulus intensity. This resonance is thought to be associated with the tectorial membrane. The resonance tends to minimize input to the cochlear receptor cells at frequencies below the high-frequency primary and increases the dynamic load to the stereocilia of the receptor cells at the primary frequency when the tectorial membrane and reticular lamina move in counterphase.

  19. Theory and measurement of the soliton self-frequency shift and efficiency in optical microcavities.

    Science.gov (United States)

    Yi, Xu; Yang, Qi-Fan; Yang, Ki Youl; Vahala, Kerry

    2016-08-01

    Dissipative Kerr cavity solitons experience a so-called self-frequency shift (SFS) as a result of Raman interactions. The frequency shift has been observed in several microcavity systems. The Raman process has also been shown numerically to influence the soliton pumping efficiency. Here, a perturbed Lagrangian approach is used to derive simple analytical expressions for the SFS and the soliton efficiency. The predicted dependences of these quantities on soliton pulse width are compared with measurements in a high-Q silica microcavity. The Raman time constant in silica is also inferred. Analytical expressions for the Raman SFS and soliton efficiency greatly simplify the prediction of soliton behavior over a wide range of microcavity platforms.

  20. Gravitational frequency shift of light in equatorial plane of a radially moving Schwarzschild black hole

    Science.gov (United States)

    He, G.; Lin, W.

    2017-10-01

    The kinematical effect induced by the transversal motion of a gravitational lens on the frequency shift of light has been investigated in detail, while the effect of the radial motion is thought to be much smaller than the transversal one and thus has usually been neglected. In this work, we find that the radial velocity effect on the frequency shift has the same order of magnitude as that of the transversal velocity effect, when the light emitter (or the receiver) is close to the gravitational lens with the distance between them being an impact parameter scale. The significant velocity effect is usually transient due to the motion of the gravitational lens relative to the light emitter or the receiver.

  1. Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity - the Boson peak of PIM-1.

    Science.gov (United States)

    Zorn, Reiner; Yin, Huajie; Lohstroh, Wiebke; Harrison, Wayne; Budd, Peter M; Pauw, Brian R; Böhning, Martin; Schönhals, Andreas

    2018-01-17

    Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, the vibrational density of states (VDOS) for PIM-1, the prototypical polymer with intrinsic microporosity, is investigated by means of inelastic neutron scattering. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid). The measured data show the characteristic low frequency excess contribution to VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers. For an annealed PIM-1 sample, the Boson peak shifts to higher frequencies in comparison to the un-annealed sample. These changes in the VDOS of the annealed PIM-1 sample are related to changes in the microporous structure as confirmed by X-ray scattering.

  2. Photonic analog-to-digital converter using soliton self-frequency shift and interleaving spectral filters.

    Science.gov (United States)

    Xu, Chris; Liu, Xiang

    2003-06-15

    We propose a novel ultrafast photonic analog-to-digital converter that uses the soliton self-frequency shift in an optical fiber as an optical power-to-frequency conversion mechanism and a set of interleaving spectral filters as the optical comparators. Our method does all the signal processing in the optical domain and requires binary receivers in only the electronic domain. In contrast to the usual exponential scaling, the simultaneous binary search architecture that we propose results in a flash analog-to-digital converter with remarkable linear scaling between the number of comparators and the number of bits resolved.

  3. Investigating lipids as a source of chemical exchange-induced MRI frequency shifts.

    Science.gov (United States)

    Shmueli, K; Dodd, S J; van Gelderen, P; Duyn, J H

    2017-04-01

    While magnetic susceptibility is a major contributor to NMR resonance frequency variations in the human brain, a substantial contribution may come from the chemical exchange of protons between water and other molecules. Exchange-induced frequency shifts fe have been measured in tissue and protein solutions, but relatively lipid-rich white matter (WM) has a larger fe than gray matter, suggesting that lipids could contribute. Galactocerebrosides (GC) are a prime candidate as they are abundant in WM and susceptible to exchange. To investigate this, fe was measured in a model of WM lipid membranes in the form of multilamellar vesicles (MLVs), consisting of a 1:2 molar ratio of GC and phospholipids (POPC), and in MLVs with POPC only. Chemical shift imaging with 15% volume fraction of dioxane, an internal reference whose protons are assumed not to undergo chemical exchange, was used to remove susceptibility-induced frequency shifts in an attempt to measure fe in MLVs at several lipid concentrations. Initial analysis of these measurements indicated a necessity to correct for small unexpected variations in dioxane concentration due to its effect on the water frequency shift. To achieve this, the actual dioxane concentration was inferred from spectral analysis and its additional contribution to fe was removed through separate experiments which showed that the water-dioxane frequency shift depended linearly on the dioxane concentration at low concentrations with a proportionality constant of -0.021 ± 0.002 ppb/mM in agreement with published experiments. Contrary to expectations and uncorrected results, for GC + POPC vesicles, the dependence of the corrected fe on GC concentration was insignificant (0.023 ± 0.037 ppb/mM; r(2)  = 0.085, p > 0.57), whereas for the POPC-only vesicles a small but significant linear increase with POPC concentration was found: 0.044 ± 0.008 ppb/mM (r(2)  = 0.877, p lipids to frequency contrast in WM may be

  4. Sum Frequency Generation Vibrational Spectroscopy of Colloidal Platinum Nanoparticle Catalysts: Disordering versus Removal of Organic Capping

    KAUST Repository

    Krier, James M.

    2012-08-23

    Recent work with nanoparticle catalysts shows that size and shape control on the nanometer scale influences reaction rate and selectivity. Sum frequency generation (SFG) vibrational spectroscopy is a powerful tool for studying heterogeneous catalysis because it enables the observation of surface intermediates during catalytic reactions. To control the size and shape of catalytic nanoparticles, an organic ligand was used as a capping agent to stabilize nanoparticles during synthesis. However, the presence of an organic capping agent presents two major challenges in SFG and catalytic reaction studies: it blocks a significant fraction of active surface sites and produces a strong signal that prevents the detection of reaction intermediates with SFG. Two methods for cleaning Pt nanoparticles capped with poly (vinylpyrrolidone) (PVP) are examined in this study: solvent cleaning and UV cleaning. Solvent cleaning leaves more PVP intact and relies on disordering with hydrogen gas to reduce the SFG signal of PVP. In contrast, UV cleaning depends on nearly complete removal of PVP to reduce SFG signal. Both UV and solvent cleaning enable the detection of reaction intermediates by SFG. However, solvent cleaning also yields nanoparticles that are stable under reaction conditions, whereas UV cleaning results in aggregation during reaction. The results of this study indicate that solvent cleaning is more advantageous for studying the effects of nanoparticle size and shape on catalytic selectivity by SFG vibrational spectroscopy. © 2012 American Chemical Society.

  5. Ab Initio Potential Energy Surfaces and the Calculation of Accurate Vibrational Frequencies

    Science.gov (United States)

    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.

  6. Analysis of subsystem randomness effects on the mid-frequency vibrations of built-up structures

    Science.gov (United States)

    Ji, Lin; Huang, Zhenyu

    2013-06-01

    The paper concerns the analysis of subsystem randomness effects on the mid-frequency vibration responses of built-up systems. The system model considered, in the first instance, is a long-wavelength finite element (FE) subsystem connected with a short-wavelength statistical energy analysis (SEA) subsystem via discrete couplings. The randomness effects of the SEA subsystem on both the displacement response of the FE subsystem and the energy response of the SEA subsystem are then investigated under the frame of the hybrid FE/SEA theory [P. Shorter, R. Langley, Vibro-acoustic analysis of complex systems, Journal of Sound and Vibration, 288 (2005) 669-700]. It is found that the subsystem randomness effects may be well indicated by a dimensionless parameter α, which is a function of the number of coupling points, the dynamic mismatch between the FE and SEA subsystems and the modal overlap factor of the SEA subsystem. The smaller the value of α is, the more insignificant the randomness effects are. As a result, a so-called "α-criterion" is derived which states that, if a built-up structure satisfies the condition of α≪1, the randomness effects of the SEA subsystem can be neglected. In this case, the SEA subsystem can be simply treated as an infinite (or semi-infinite as appropriate) structure regardless of its mode count being sufficiently high or not. Numerical examples are presented to illustrate the validity of the present theory.

  7. Observation of the low frequency vibrational modes of bacteriophage M13 in water by Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Tsen Shaw-Wei D

    2006-09-01

    Full Text Available Abstract Background Recently, a technique which departs radically from conventional approaches has been proposed. This novel technique utilizes biological objects such as viruses as nano-templates for the fabrication of nanostructure elements. For example, rod-shaped viruses such as the M13 phage and tobacco mosaic virus have been successfully used as biological templates for the synthesis of semiconductor and metallic nanowires. Results and discussion Low wave number (≤ 20 cm-1 acoustic vibrations of the M13 phage have been studied using Raman spectroscopy. The experimental results are compared with theoretical calculations based on an elastic continuum model and appropriate Raman selection rules derived from a bond polarizability model. The observed Raman mode has been shown to belong to one of the Raman-active axial torsion modes of the M13 phage protein coat. Conclusion It is expected that the detection and characterization of this low frequency vibrational mode can be used for applications in nanotechnology such as for monitoring the process of virus functionalization and self-assembly. For example, the differences in Raman spectra can be used to monitor the coating of virus with some other materials and nano-assembly process, such as attaching a carbon nanotube or quantum dots.

  8. Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures

    Science.gov (United States)

    den Haan, A. M. J.; Wagenaar, J. J. T.; de Voogd, J. M.; Koning, G.; Oosterkamp, T. H.

    2015-12-01

    We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to 25 mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two-dimensional system of electron spins. We approach the sample with a 3.43 μ m -diameter magnetic particle attached to an ultrasoft cantilever and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time T1=0.39 ±0.08 ms and spin density σ =0.14 ±0.01 spins per nm 2. Our analysis shows that at temperatures ≤500 mK magnetic dissipation is an important source of noncontact friction.

  9. Stability of high-frequency periodic motions of a heavy rigid body with a horizontally vibrating suspension point

    Science.gov (United States)

    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.

  10. Structure of the ethylammonium nitrate surface: an X-ray reflectivity and vibrational sum frequency spectroscopy study.

    Science.gov (United States)

    Niga, Petru; Wakeham, Deborah; Nelson, Andrew; Warr, Gregory G; Rutland, Mark; Atkin, Rob

    2010-06-01

    X-ray reflectivity and vibrational sum frequency spectroscopy are used to probe the structure of the ethylammonium nitrate (EAN)-air interface. X-ray reflectivity reveals that the EAN-air interface is structured and consists of alternating nonpolar and charged layers that extend 31 A into the bulk. Vibrational sum frequency spectroscopy reveals interfacial cations have their ethyl moieties oriented toward air, with the CH(3) C(3) axis positioned approximately 36.5 degrees from interface normal. This structure is invariant between 15 and 51 degrees C. On account of its molecular symmetry, the orientation of the nitrate anion cannot be determined with certainty.

  11. A study of the eigenvectors of the low-frequency vibrational modes in crystalline adenosine via high pressure Raman spectroscopy.

    Science.gov (United States)

    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.

  12. The effects of whole-body vibration on the Wingate test for anaerobic power when applying individualized frequencies.

    Science.gov (United States)

    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.

  13. Theoretical study of sum-frequency vibrational spectroscopy on limonene surface

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Ren-Hui, E-mail: zrh@iccas.ac.cn; Liu, Hao; Jing, Yuan-Yuan; Wang, Bo-Yang; Shi, Qiang [Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190 (China); Wei, Wen-Mei [Department of Chemistry, College of Basic Medicine, Anhui Medical University, Hefei, Anhui 230032 (China)

    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.

  14. Note: A kinematic shaker system for high amplitude, low frequency vibration testing.

    Science.gov (United States)

    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.

  15. Sum Frequency Generation Vibrational Spectroscopy of Pyridine Hydrogenation on Platinum Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters

    Science.gov (United States)

    Sharpes, Nathan; Abdelkefi, Abdessattar; Priya, Shashank

    2015-08-01

    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 mm2 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.

  17. Coupled rotor-fuselage vibration reduction with multiple frequency blade pitch control

    Science.gov (United States)

    Papavassiliou, I.; Friedmann, P. P.; Venkatesan, C.

    1991-01-01

    A nonlinear coupled rotor/flexible fuselage analysis has been developed and used to study the effects of higher harmonic blade pitch control on the vibratory hub loads and fuselage acceleration levels. Previous results, obtained with this model have shown that conventional higher harmonic control (HHC) inputs aimed at hub shear reduction cause an increase in the fuselage accelerations and vice-versa. It was also found that for simultaneous reduction of hub shears and fuselage accelerations, a pitch input representing a combination of two higher harmonic components of different frequencies was needed. Subsequently, it was found that this input could not be implemented through a conventional swashplate. This paper corrects a mistake originally made in the representation of the multiple frequency pitch input and shows that such a pitch input can be only implemented in the rotating reference frame. A rigorous mathematical solution is found, for the pitch input in the rotating reference frame, which produces simultaneous reduction of hub shears and fuselage acceleration. New insight on vibration reduction in coupled rotor/fuselage systems is obtained from the sensitivity of hub shears to the frequency and amplitude of the open loop HHC signal in the rotating reference frame. Finally the role of fuselage flexibility in this class of problems is determined.

  18. Fundamental Frequencies of Vibration of Footbridges in Portugal: From In Situ Measurements to Numerical Modelling

    Directory of Open Access Journals (Sweden)

    C. S. Oliveira

    2014-01-01

    Full Text Available Since 1995, we have been measuring the in situ dynamic characteristics of different types of footbridges built in Portugal (essentially steel and precast reinforced concrete decks with single spans running from 11 to 110 m long, using expedite exciting and measuring techniques. A database has been created, containing not only the fundamental dynamic characteristics of those structures (transversal, longitudinal, and vertical frequencies but also their most important geometric and mechanical properties. This database, with 79 structures organized into 5 main typologies, allows the setting of correlations of fundamental frequencies as a negative power function of span lengths L  (L-0.6 to L-1.4. For 63 footbridges of more simple geometry, it was possible to obtain these correlations by typology. A few illustrative cases representing the most common typologies show that linear numerical models can reproduce the in situ measurements with great accuracy, not only matching the frequencies of vibration but also the amplitudes of motion caused by several pedestrian load patterns.

  19. Accurate Lineshapes from Sub-1 cm-1 Resolution Sum Frequency Generation Vibrational Spectroscopy of α-Pinene at Room Temperature

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. Influence of high-frequency vibrations on the onset of convection in a two-layer system

    Science.gov (United States)

    Zenkovskaya, Svetlana M.; Novosiadliy, Vasili A.

    2008-03-01

    This Note deals with the influence of high-frequency translational oscillations on the onset of convection in a two-layer system of weakly heterogeneous immiscible fluids with deformable interface. The averaging method is applied to the generalized Oberbeck-Boussinesq equations. Vibration-generated forces and tensions appear as the result. A transition to the Oberbeck-Boussinesq approximation is made in the averaged equations. Analysis of averaged equations leads to the following conclusions. Horizontal vibrations are obtained not influencing the onset of convection, and in the cases of other directions the influence of vibration is determined by a single parameter, depending on velocity amplitude and direction. Vibration is shown to generate effective surface tension, smoothing the interface. Critical parameters are calculated for the case of homogeneous fluids. To cite this article: S.M. Zenkovskaya, V.A. Novosiadliy, C. R. Mecanique 336 (2008).

  1. Design of serial linkage-type vibration energy harvester with three resonant frequencies

    Science.gov (United States)

    Kim, Hyun Soo; Kim, Jun Woo; Park, Shi-Baek; Choi, Yong Je

    2017-11-01

    This paper presents a new design method of a planar 3 degrees-of-freedom(DOF) serial linkage-type vibration energy harvester with a single proof mass. The harvester is designed to generate electrical power at equally spaced three target resonant frequencies which can be chosen arbitrarily. For given target frequencies and a proof mass, the design method involves (1) the determination of the stiffness matrix, (2) the synthesis of the stiffness by means of a parallel connection of three line springs and (3) its conversion into a 3DOF device connected serially by torsional springs. The torsional springs are realized by the flexible hinge joints and the polyvinylidene fluoride(PVDF) films are attached on the joints. Upon determination of the desired stiffness matrix, the SQP algorithm is utilized to find the optimum locations and spring constants of the serial hinge joints for the minimum difference among three electrical power peaks. The FEM analysis and experiments are conducted to verify the proposed design method. Three measured resonant power peaks occur at 24.7, 30.4 and 33.6 Hz comparing to the target frequencies of 25, 30 and 35 Hz. The normalized maximum power of 14.5 {{uW}}/{({{{ms}}}-2)}2 is generated at 24.7 Hz. The experimental results also demonstrate that the harvester can generate at least 18.6% of the peak power throughout the frequency range from 23.1 to 36.5 Hz, which ensures consistently acquirable power within the operating frequency range by virtue of the coupled effect of a serial linkage-type structure.

  2. Non-steady-state photoelectromotive force effect under linear and periodical phase modulation: application to detection of Doppler frequency shift.

    Science.gov (United States)

    Mansurova, S; Zarate, P Moreno; Rodriguez, P; Stepanov, S; Köber, S; Meerholz, K

    2012-02-01

    Non-steady-state photoelectromotive force effect in the presence of periodical and linear phase shift was investigated both theoretically and experimentally. It was shown that superposition of oscillating and linear movements of the interference pattern leads to the appearance of the sharp peak in the frequency dependence of the photoelectromotive force output current when the frequency of periodical modulation matches the frequency of the linear phase shift. We demonstrated experimentally that this effect can be used for determination of a Doppler frequency shift between signal and reference beam.

  3. Using frequency response functions to manage image degradation from equipment vibration in the Daniel K. Inouye Solar Telescope

    Science.gov (United States)

    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.

  4. Rovibrational spectroscopic constants and fundamental vibrational frequencies for isotopologues of cyclic and bent singlet HC{sub 2}N isomers

    Energy Technology Data Exchange (ETDEWEB)

    Inostroza, Natalia; Fortenberry, Ryan C.; Lee, Timothy J. [NASA Ames Research Center, Moffett Field, CA 94035-1000 (United States); Huang, Xinchuan, E-mail: Timothy.J.Lee@nasa.gov [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States)

    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.

  5. Low intensity, high frequency vibration training to improve musculoskeletal function in a mouse model of Duchenne muscular dystrophy.

    Directory of Open Access Journals (Sweden)

    Susan A Novotny

    Full Text Available 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.

  6. FREQUENCY SHIFTS OF RESONANT MODES OF THE SUN DUE TO NEAR-SURFACE CONVECTIVE SCATTERING

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, J.; Hanasoge, S.; Antia, H. M. [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai-400005 (India)

    2015-06-20

    Measurements of oscillation frequencies of the Sun and stars can provide important independent constraints on their internal structure and dynamics. Seismic models of these oscillations are used to connect structure and rotation of the star to its resonant frequencies, which are then compared with observations, the goal being that of minimizing the difference between the two. Even in the case of the Sun, for which structure models are highly tuned, observed frequencies show systematic deviations from modeled frequencies, a phenomenon referred to as the “surface term.” The dominant source of this systematic effect is thought to be vigorous near-surface convection, which is not well accounted for in both stellar modeling and mode-oscillation physics. Here we bring to bear the method of homogenization, applicable in the asymptotic limit of large wavelengths (in comparison to the correlation scale of convection), to characterize the effect of small-scale surface convection on resonant-mode frequencies in the Sun. We show that the full oscillation equations, in the presence of temporally stationary three-dimensional (3D) flows, can be reduced to an effective “quiet-Sun” wave equation with altered sound speed, Brünt–Väisäla frequency, and Lamb frequency. We derive the modified equation and relations for the appropriate averaging of 3D flows and thermal quantities to obtain the properties of this effective medium. Using flows obtained from 3D numerical simulations of near-surface convection, we quantify their effect on solar oscillation frequencies and find that they are shifted systematically and substantially. We argue therefore that consistent interpretations of resonant frequencies must include modifications to the wave equation that effectively capture the impact of vigorous hydrodynamic convection.

  7. Frequency of spontaneous BOLD signal shifts during infancy and correlates with cognitive performance

    Directory of Open Access Journals (Sweden)

    Sarael Alcauter

    2015-04-01

    Full Text Available Numerous studies have been conducted to delineate the early development of different functional networks, based on measuring the temporal synchronization of spontaneous blood oxygenation level-dependent (BOLD signals acquired using resting state functional MRI (rsfMRI. However, little attention has been paid to the change of the frequency properties of these signals during early brain development. Such frequency properties may reflect important physiological changes and potentially have significant cognitive consequences. In this study, leveraging a large (N = 86 subjects, longitudinal sample of human infants scanned during the first two years of life, we aimed to specifically delineate the developmental changes of the frequency characteristics of spontaneous BOLD signals. Both whole-brain and network-level examinations were carried out and the frequency–behavior relationship was explored. Our results revealed a clear right-ward shift of BOLD signal frequency during the first year of life. Moreover, the power at the peak-frequency for sensorimotor and lateral visual networks correlates with domain-specific Mullen Scales in 1-year-olds, suggesting the behavioral significance of the BOLD signal frequency during infancy. Findings from this study shed light into early functional brain development and provide a new perspective for future searches for functional developmental abnormalities.

  8. Audiometric notch and extended high-frequency hearing threshold shift in relation to total leisure noise exposure: An exploratory analysis

    Directory of Open Access Journals (Sweden)

    Wenjia Wei

    2017-01-01

    Full Text Available Background: Studies investigating leisure noise effect on extended high frequency hearing are insufficient and they have inconsistent results. The aim of this study was to investigate if extended high-frequency hearing threshold shift is related to audiometric notch, and if total leisure noise exposure is associated with extended high-frequency hearing threshold shift. Materials and Methods: A questionnaire of the Ohrkan cohort study was used to collect information on demographics and leisure time activities. Conventional and extended high-frequency audiometry was performed. We did logistic regression between extended high-frequency hearing threshold shift and audiometric notch as well as between total leisure noise exposure and extended high-frequency hearing threshold shift. Potential confounders (sex, school type, and firecrackers were included. Results: Data from 278 participants (aged 18–23 years, 53.2% female were analyzed. Associations between hearing threshold shift at 10, 11.2, 12.5, and 14 kHz with audiometric notch were observed with a higher prevalence of threshold shift at the four frequencies, compared to the notch. However, we found no associations between total leisure noise exposure and hearing threshold shift at any extended high frequency. Conclusion: This exploratory analysis suggests that while extended high-frequency hearing threshold shifts are not related to total leisure noise exposure, they are strongly associated with audiometric notch. This leads us to further explore the hypothesis that extended high-frequency threshold shift might be indicative of the appearance of audiometric notch at a later time point, which can be investigated in the future follow-ups of the Ohrkan cohort.

  9. Fin whale sound reception mechanisms: skull vibration enables low-frequency hearing.

    Directory of Open Access Journals (Sweden)

    Ted W Cranford

    Full Text Available 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.

  10. Fin whale sound reception mechanisms: skull vibration enables low-frequency hearing.

    Science.gov (United States)

    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.

  11. Fin Whale Sound Reception Mechanisms: Skull Vibration Enables Low-Frequency Hearing

    Science.gov (United States)

    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

  12. Frequency-doubled microwave waveforms generation using a dual-polarization quadrature phase shift keying modulator driven by a single frequency radio frequency signal

    Science.gov (United States)

    Zhu, Zihang; Zhao, Shanghong; Li, Xuan; Qu, Kun; Lin, Tao

    2018-01-01

    A photonic approach to generate frequency-doubled microwave waveforms using an integrated dual-polarization quadrature phase shift keying (DP-QPSK) modulator driven by a sinusoidal radio frequency (RF) signal is proposed. By adjusting the dc bias points of the DP-QPSK modulator, the obtained second-order and six-order harmonics are in phase while the fourth-order harmonics are complementary when the orthogonal polarized outputs of the modulator are photodetected. After properly setting the modulation indices of the modulator, the amplitude of the second-order harmonic is 9 times of that of the six-order harmonic, indicating a frequency-doubled triangular waveform is generated. If a broadband 90° microwave phase shifter is attached after the photodetector (PD) to introduce a 90° phase shift, a frequency-doubled square waveform can be obtained after adjusting the amplitude of the second-order harmonic 3 times of that of the six-order harmonic. The proposal is first theoretically analyzed and then validated by simulation. Simulation results show that a 10 GHz triangular and square waveform sequences are successfully generated from a 5 GHz sinusoidal RF drive signal.

  13. Calculation and analysis of the harmonic vibrational frequencies in molecules at extreme pressure: Methodology and diborane as a test case

    Science.gov (United States)

    Cammi, R.; Cappelli, C.; Mennucci, B.; Tomasi, J.

    2012-10-01

    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.

  14. Search for the Variation in (mp/me) Using Two Vibrational Transition Frequencies of Molecular Ions

    Science.gov (United States)

    Kajita, Masatoshi

    2017-12-01

    We propose a method to search for the variation in the proton-to-electron mass ratio μ = (mp/me) based on the precise measurement of Q(v') = [f(v') - f(2v')/2]/f(v'), where f(v') is the 16O2+ X2Π 1/2(v,J) = (0,1/2) \\to (v',1/2) transition frequency. Q(v') is proportional to μ-1/2, and it can be measured with an uncertainty of 10-18. This method is also applicable to other molecular transition frequencies (i) J = 0 → 0 or 1/2 → 1/2 transition, (ii) transition between stretched states, and (iii) the same sign for the light shift induced by the clock lasers in f(v') and f(2v').

  15. Hybrid nanogenerators for low frequency vibration energy harvesting and self-powered wireless locating

    Science.gov (United States)

    Yuan, Ying; Zhang, Hulin; Wang, Jie; Xie, Yuhang; Khan, Saeed Ahmed; Jin, Long; Yan, Zhuocheng; Huang, Long; Pan, Taisong; Yang, Weiqing; Lin, Yuan

    2018-01-01

    Hybrid energy harvesters based on different physical effects is fascinating, but a rational design for multiple energy harvesting is challenging. In this work, a spring-magnet oscillator-based triboelectric-electromagnetic generator (EMG) with a solar cell cap is proposed. A power was produced by a triboelectric nanogenerator (TENG) and an EMG independently or simultaneously by using a shared spring-magnet oscillator. The oscillator configuration enables versatile energy harvesting with the excellent size scalability and self-packaged structure which can perform well at low frequency ranging from 3.5 to 5 Hz. The solar cell cap mounted above the oscillator can harvest solar energy. Under vibrations at the frequency of 4 Hz, the TENG and the EMG produced maximum output power of 5.46 nW cm‑3 and 378.79 μW cm‑3, respectively. The generated electricity by the hybrid nanogenerator can be stored in a capacitor or Li-ion battery, which is capable of powering a wireless locator for real-time locating data reporting to a personal cell phone. The light-weight and handy hybrid nanogenerator can directly light a caution light or play as a portable flashlight by shaking hands at night.

  16. Prediction of high-frequency vibration transmission across coupled, periodic ribbed plates by incorporating tunneling mechanisms.

    Science.gov (United States)

    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.

  17. Stain-free Histopathology of Basal Cell Carcinoma by Dual Vibration Resonance Frequency CARS Microscopy.

    Science.gov (United States)

    Kiss, Norbert; Krolopp, Ádám; Lőrincz, Kende; Bánvölgyi, András; Szipőcs, Róbert; Wikonkál, Norbert

    2017-11-04

    Basal cell carcinoma (BCC) is the most common malignancy in Caucasians. Nonlinear microscopy has been previously utilized for the imaging of BCC, but the captured images do not correlate with H&E staining. Recently, Freudiger et al. introduced a novel method to visualize tissue morphology analogous to H&E staining, using coherent anti-Stokes Raman scattering (CARS) technique. In our present work, we introduce a novel algorithm to post-process images obtained from dual vibration resonance frequency (DVRF) CARS measurements to acquire high-quality pseudo H&E images of BCC samples. We adapted our CARS setup to utilize the distinct vibrational properties of CH 3 (mainly in proteins) and CH 2 bonds (primarily in lipids). In a narrowband setup, the central wavelength of the pump laser is set to 791 nm and 796 nm to obtain optimal excitation. Due to the partial overlap of the excitation spectra and the 5-10 nm FWHM spectral bandwidth of our lasers, we set the wavelengths to 790 nm (proteins) and 800 nm (lipids). Nonresonant background from water molecules also reduces the chemical selectivity which can be significantly improved if we subtract the DVRF images from each other. As a result, we acquired two images: one for "lipids" and one for" proteins" when we properly set a multiplication factor to minimize the non-specific background. By merging these images, we obtained high contrast H&E "stained" images of BBC's. Nonlinear microscope systems upgraded for real time DVRF CARS measurements, providing pseudo H&E images can be suitable for in vivo assessment of BCC in the future.

  18. Correlates shift work with increased risk of gastrointestinal complaints or frequency of gastritis or peptic ulcer in H. pylori-infected shift workers?

    Science.gov (United States)

    van Mark, Anke; Spallek, Michael; Groneberg, David A; Kessel, Richard; Weiler, Stephan W

    2010-04-01

    There is an ongoing discussion whether work under shift work conditions enhances the ulcerogenic potential of Helicobacter pylori infections. This may be induced by a disruption of the circadian rhythm. The present study assessed whether there is an association between H. pylori infection and an increased risk of gastrointestinal complaints or frequency of gastritis or peptic ulcer in H. pylori-infected shift workers. We analyzed 615 workers divided in shift and daytime. Upper gastrointestinal diseases, medication or operation, unspecific gastrointestinal complaints, smoking habits, subjective job strain and private stress factors were monitored. The H. pylori status was analyzed using IgA and IgG antibody concentration in blood and qualitative ELISA for feces. It was observed that 27.6% of all workers, 34.6% of the shift workers and 16% of daytime workers were Hp positive (P = 0.004). Shift workers reported reflux or pyrosis less frequently than daytime workers. No increased lifetime prevalence for gastritis, ulcus or eradication therapy was found for shift workers. Analysis revealed a weak regression between age and Hp-positive gastritis or upper gastrointestinal complaints, smoking habits were a major confounding factor for ulcus disease. Clinical manifestation of gastritis or ulcus disease did not correlate with shift work or especially shift work including night work. As a result of the present study, it cannot be confirmed that there is a causal connection between shift work and upper or unspecific gastrointestinal complaints or gastritis or peptic ulcer in dependency of a H. pylori colonization.

  19. Rigorous intensity and phase-shift manipulation in optical frequency conversion.

    Science.gov (United States)

    Yang, Bo; Yue, Yang-Yang; Lu, Rong-Er; Hong, Xu-Hao; Zhang, Chao; Qin, Yi-Qiang; Zhu, Yong-Yuan

    2016-06-07

    A simple method is employed to investigate the nonlinear frequency conversion in optical superlattices (OSL) with pump depletion. Four rigorous phase-matching conditions for different purposes are obtained directly from the nonlinear coupled equations, and the resulting OSL domain structures are generally aperiodic rather than periodic. With this method, not only the intensity but also the phase-shift of the harmonic waves can be manipulated at will. The second-harmonic generation of Gaussian beam is further investigated. This work may provide a guidance for the practical applications of designing nonlinear optical devices with high conversion efficiency.

  20. Hydrostatic pressure dependence of Brillouin frequency shift in polymer optical fibers

    Science.gov (United States)

    Mizuno, Yosuke; Lee, Heeyoung; Hayashi, Neisei; Nakamura, Kentaro

    2018-01-01

    We experimentally investigate the pressure dependence of the Brillouin frequency shift (BFS) in a polymer optical fiber. The BFS dependence on pressure shows a hysteresis, but after several cycles of increasing/decreasing pressure, the hysteresis is mitigated. The pressure dependence coefficient at this state is +4.3 MHz/MPa, the absolute value of which is 5.8 times as large as that of bare silica fibers (the sign is opposite). The reason for this unique behavior is discussed. This result indicates that, by using plastic optical fibers instead of silica fibers, distributed pressure sensing with a higher sensitivity is potentially feasible.

  1. Origin of the frequency shift of Raman scattering in chalcogenide glasses

    DEFF Research Database (Denmark)

    Han, X.C.; Tao, H.Z.; Gong, L.J.

    2014-01-01

    of the shift is associated with the topological connectivity of global network and/or the local environment of structural units, (e.g., tetrahedral GeSe4). Here we show the compositional evolution of the main Raman scattering frequency in Ge(SxSe1−x)2 glasses, and then clarify its structural origin. We keep...... units such as GeS4 tetrahedra. The ab-initio calculations of normal Raman mode combined with group theory analysis provide insight into the structural evolution of chalcogenide glasses with varying composition....

  2. Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters

    Energy Technology Data Exchange (ETDEWEB)

    Sharpes, Nathan [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Abdelkefi, Abdessattar [Department of Mechanical and Aerospace Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States); Priya, Shashank [Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech, Blacksburg, Virginia 24061 (United States); Bio-Inspired Materials and Devices Laboratory (BMDL), Virginia Tech, Blacksburg, Virginia 24061 (United States)

    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.

  3. Low-Frequency and Broadband Vibration Energy Harvesting Using Base-Mounted Piezoelectric Transducers.

    Science.gov (United States)

    Koven, Robert; Mills, Matthew; Gale, Richard; Aksak, Burak

    2017-11-01

    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 mm 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 and at 45 Hz across a 13.0- load under harmonic base excitations of constant peak acceleration at 0.25 and 1.0-g, respectively. We also show an increase in full-width half-maximum bandwidth approximately from 1.5 to 5.6 Hz using an array of four individual BMP harvesters of similar dimensions with peak power generation of at 37.6 Hz across a 1.934- load at 0.25-g 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 this 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.

  4. Vibrational frequency analysis, FT-IR, FT-Raman, ab initio, HF and DFT studies, NBO, HOMO-LUMO and electronic structure calculations on pycolinaldehyde oxime

    Science.gov (United States)

    Suvitha, A.; Periandy, S.; Boomadevi, S.; Govindarajan, M.

    2014-01-01

    In this work, the vibrational spectral analysis is carried out by using Raman and infrared spectroscopy in the range 100-4000 cm-1and 50-4000 cm-1, respectively, for pycolinaldehyde oxime (PAO) (C6H6N2O) molecule. The vibrational frequencies have been calculated and scaled values are compared with experimental FT-IR and FT-Raman spectra. The structure optimizations and normal coordinate force field calculations are based on HF and B3LYP methods with 6-311++G(d,p) basis set. The results of the calculation shows excellent agreement between experimental and calculated frequencies in B3LYP/6-311++G(d,p) basis set. The optimized geometric parameters are compared with experimental values of PAO. The non linear optical properties, NBO analysis, thermodynamics properties and mulliken charges of the title molecule are also calculated and interpreted. A study on the electronic properties, such as HOMO and LUMO energies, are performed by time-dependent DFT (TD-DFT) approach. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) are performed. The effects due to the substitutions of CHdbnd NOH ring are investigated. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.

  5. Spectral assignment and orientational analysis in a vibrational sum frequency generation study of DPPC monolayers at the air/water interface.

    Science.gov (United States)

    Feng, Rong-Juan; Li, Xia; Zhang, Zhen; Lu, Zhou; Guo, Yuan

    2016-12-28

    The interfacial behavior of the benchmark zwitterionic phospholipid molecule dipalmitoylphosphatidylcholine (DPPC) has been extensively investigated by surface-selective vibrational sum frequency generation spectroscopy (VSFG). However, there is still a lack of agreement between various orientational measurements of phospholipid monolayers at the air/water interface, mainly because of the difficulty in assigning congested VSFG features. In this study, polarization-dependent VSFG measurements reveal a frequency shift between the in-plane and out-of-plane antisymmetric stretching modes of the terminal methyl groups in the DPPC alkyl tails, favoring the model of Cs local symmetry rather than the previously assumed C3v symmetry. Further VSFG experiments of isotopically labeled DPPC successfully capture the vibrational signatures of the glycerol backbone. With the newly derived VSFG polarization selection rules for Cs symmetry and the refreshed spectral assignments, the average tilt angles of the alkyl tail groups, choline headgroup, and glycerol backbone of DPPC molecules can all be determined, showing the powerful capability of VSFG spectroscopy in revealing the structural details at interfaces. The VSFG polarization dependence rules and the orientational analysis procedures developed for Cs symmetry in this work are applicable to other bulky molecules in which the methyl group cannot freely rotate, and they therefore have general applications in future VSFG studies.

  6. Frequency-Shifted Interferometry — A Versatile Fiber-Optic Sensing Technique

    Directory of Open Access Journals (Sweden)

    Fei Ye

    2014-06-01

    Full Text Available Fiber-optic sensing is a field that is developing at a fast pace. Novel fiber-optic sensor designs and sensing principles constantly open doors for new opportunities. In this paper, we review a fiber-optic sensing technique developed in our research group called frequency-shifted interferometry (FSI. This technique uses a continuous-wave light source, an optical frequency shifter, and a slow detector. We discuss the operation principles of several FSI implementations and show their applications in fiber length and dispersion measurement, locating weak reflections along a fiber link, fiber-optic sensor multiplexing, and high-sensitivity cavity ring-down measurement. Detailed analysis of FSI system parameters is also presented.

  7. Measurements of quadrupole frequency shift in the SPS at 26 GeV/c

    CERN Document Server

    Bohl, T; Shaposhnikova, E; Tückmantel, Joachim; CERN. Geneva. AB Department

    2008-01-01

    Measurements of the quadrupole frequency shift with intensity at 26 GeV/c using the peak detected signal were performed in the SPS from 1999 to monitor the evolution of the low-frequency longitudinal impedance [1]. While the large changes, first, due to the impedance reduction and then due to the re-installation of the MKE kickers,are easy to see, to observe small variations of impedance (as shielding or removal of a few kickers) much higher accuracy of measurements is required. This was difficult to achieve so far, mainly due to the insufficient reproducibility of the longitudinal parameters of the injected beam for different intensities as well as for different MDs. In this Note the important role of longitudinal emittance in addition to the bunch length is also revealed.

  8. Measurement of Carrier-Envelope-Phase shifts using spectral interferometry with a broad frequency laser source

    Science.gov (United States)

    Gobert, O.; Fedorov, N.; Tcherbakoff, O.; Hergott, J. F.; Perdrix, M.; Lepetit, F.; Guillaumet, D.; Comte, M.

    2012-02-01

    We investigate and analyze in detail an approach to measure Carrier Envelope Phase shifts by using spectral interferometry. The method which uses a broadband laser source is applied to the characterization of an Electro Optic Carrier Envelope Phase shifter and leads to quick and accurate measurements on a large frequency domain. The shifter is inserted in one arm of a Mach-Zehnder interferometer illuminated by a wide frequency spectrum coherent source. By carefully analyzing the observed fringes, we successfully derived, with a very good accuracy, the main useful parameters of the CEP shifter on the whole investigated wavelength spectrum. The laser source which delivers pulses with a Gaussian spatial distribution and a nearly flat spatial phase does not need to be CEP stabilized and no control of the spectral phase of the pulses is necessary. This has specific advantages compared to other methods.

  9. FM echolocating bats shift frequencies to avoid broadcast-echo ambiguity in clutter.

    Science.gov (United States)

    Hiryu, Shizuko; Bates, Mary E; Simmons, James A; Riquimaroux, Hiroshi

    2010-04-13

    Sonar broadcasts are followed by echoes at different delays from objects at different distances. When broadcasts are emitted rapidly in cluttered surroundings, echo streams from successive broadcasts overlap and cause ambiguity in matching echoes to corresponding broadcasts. To identify reactions to ambiguity in clutter, echolocating bats that emit multiple-harmonic FM sounds were trained to fly into a dense, extended array of obstacles (multiple rows of vertically hanging chains) while the sonar sounds the bat emitted were recorded with a miniature radio microphone carried by the bat. Flight paths were reconstructed from thermal-infrared video recordings. Successive rows of chains extended more than 6 m in depth, so each broadcast was followed by a series of echoes from multiple rows of chains that lasted up to 40 ms. Bats emitted sounds in pairs ("strobe groups") at short (20-40 ms) interpulse intervals (IPIs) alternating with longer IPIs (>50 ms). For many short IPIs, the stream of echoes from the first broadcast was still arriving when the second broadcast was emitted. This overlap caused ambiguity about matching echoes with broadcasts. Bats shifted frequencies of the first sound in each strobe group upward and the second sound downward by 3-6 kHz. When overlap and ambiguity ceased, frequency shifts ceased also. Frequency differences were small compared with the total broadcast band, which was 75-80 kHz wide, but the harmonic structure of echoes enhances the differences in spectrograms. Bats could use time-frequency comparisons of echoes with broadcasts to assign echoes to the corresponding broadcasts and thus avoid ambiguity.

  10. Application of a commercially-manufactured Doppler-shift laser velocimeter to the measurement of basilar-membrane vibration*

    Science.gov (United States)

    Ruggero, Mario A.; Rich, Nola C.

    2013-01-01

    A commercially-available laser Doppler-shift velocimeter has been coupled to a compound microscope equipped with ultra-long-working-distance objectives for the purpose of measuring basilar membrane vibrations in the chinchilla. The animal preparation is nearly identical to that used in our laboratory for similar measurements using the Mössbauer technique. The vibrometer head is mounted on the third tube of the microscope’s trinocular head and its laser beam is focused on high-refractive-index glass microbeads (10–30 µm) previously dropped, through the perilymph of Scala tympani, on the basilar membrane. For equal sampling times, overall sensitivity of the laser velocimetry system is at least one order of magnitude greater than usually attained using the Mössbauer technique. However, the most important advantage of laser velocimetry vis-à-vis the Mössbauer technique is its linearity, which permits undistorted recording of signals over a wide velocity range. Thus, for example, we have measured basilar-membrane responses to clicks whose waveforms have dynamic ranges exceeding 60 dB. PMID:1827787

  11. On the relation between activity-related frequency shifts and the sunspot distribution over the solar cycle 23

    Directory of Open Access Journals (Sweden)

    Santos Ângela R. G.

    2017-01-01

    Full Text Available The activity-related variations in the solar acoustic frequencies have been known for 30 years. However, the importance of the different contributions is still not well established. With this in mind, we developed an empirical model to estimate the spot-induced frequency shifts, which takes into account the sunspot properties, such as area and latitude. The comparison between the model frequency shifts obtained from the daily sunspot records and those observed suggests that the contribution from a stochastic component to the total frequency shifts is about 30%. The remaining 70% is related to a global, long-term variation. We also propose a new observable to investigate the short-and mid-term variations of the frequency shifts, which is insensitive to the long-term variations contained in the data. On the shortest time scales the variations in the frequency shifts are strongly correlated with the variations in the total area covered by sunspots. However, a significant loss of correlation is still found, which cannot be fully explained by ignoring the invisible side of the Sun when accounting for the total sunspot area. We also verify that the times when the frequency shifts and the sunspot areas do not vary in a similar way tend to coincide with the times of the maximum amplitude of the quasi-biennial variations found in the seismic data.

  12. A handy-motion driven, frequency up-converted hybrid vibration energy harvester using PZT bimorph and nonmagnetic ball

    Science.gov (United States)

    Halim, M. A.; Cho, H. O.; Park, J. Y.

    2014-11-01

    We have presented a frequency up-converted hybrid type (Piezoelectric and Electromagnetic) vibration energy harvester that can be used in powering portable and wearable smart devices by handy motion. A transverse impact mechanism has been employed for frequency up-conversion. Use of two transduction mechanisms increases the output power as well as power density. The proposed device consists of a non-magnetic spherical ball (freely movable at handy motion frequency) to impact periodically on the parabolic top of a piezoelectric (PZT) cantilevered mass by sliding over it, allowing it to vibrate at its higher resonant frequency and generates voltage by virtue of piezoelectric effect. A magnet attached to the cantilever vibrates along with it at the same frequency and a relative motion between the magnet and a coil placed below it, induces emf voltage across the coil terminals as well. A macro-scale prototype of the harvester has been fabricated and tested by handy motion. With an optimum magnet-coil overlap, a maximum 0.98mW and 0.64mW peak powers have been obtained from the piezoelectric and the electromagnetic transducers of the proposed device while shaken, respectively. It offers 84.4μWcm-3 peak power density.

  13. Biomolecular stiffness detection based on positive frequency shift of CMOS compatible gigahertz solidly mounted resonators.

    Science.gov (United States)

    Yang, Qingrui; Pan, Shuting; Zhao, Yuan; Zhang, Hao; Pang, Wei; Duan, Xuexin

    2017-10-15

    In this work, gigahertz solidly mounted resonators (SMRs) (2.5GHz) were designed and fabricated to construct a novel particle-resonator system to achieve the biomolecular stiffness sensing in real time. The positive frequency shift of the system was used to estimate the stiffness of biomolecules connecting between the SMR and attached particles. The working principle was revealed by the mathematical analysis of the general block-spring model of the system. Further interpretations about the mechanism of such elastic interaction from the perspective of acoustic resonant modes of SMRs were given by finite element method. Biotin-streptavidin, antibody and antigen binding system were used as model molecular linkers to study the frequency shift varied with different particle diameters and particle densities. Different linker stiffness was realized by adjusting the concentrations of antigens connected with particles which form specific binding with antibodies immobilized on the SMR. The results fairly agree with the simulation results demonstrating the proposed particle-resonator system as an effective method to realize the real-time biomolecular stiffness detection. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Cahokia’s emergence and decline coincided with shifts of flood frequency on the Mississippi River

    Science.gov (United States)

    Munoz, Samuel E.; Gruley, Kristine E.; Massie, Ashtin; Fike, David A.; Schroeder, Sissel; Williams, John W.

    2015-01-01

    Here we establish the timing of major flood events of the central Mississippi River over the last 1,800 y, using floodwater sediments deposited in two floodplain lakes. Shifts in the frequency of high-magnitude floods are mediated by moisture availability over midcontinental North America and correspond to the emergence and decline of Cahokia—a major late prehistoric settlement in the Mississippi River floodplain. The absence of large floods from A.D. 600 to A.D. 1200 facilitated agricultural intensification, population growth, and settlement expansion across the floodplain that are associated with the emergence of Cahokia as a regional center around A.D. 1050. The return of large floods after A.D. 1200, driven by waning midcontinental aridity, marks the onset of sociopolitical reorganization and depopulation that culminate in the abandonment of Cahokia and the surrounding region by A.D. 1350. Shifts in the frequency and magnitude of flooding may be an underappreciated but critical factor in the formation and dissolution of social complexity in early agricultural societies. PMID:25941363

  15. Cahokia's emergence and decline coincided with shifts of flood frequency on the Mississippi River.

    Science.gov (United States)

    Munoz, Samuel E; Gruley, Kristine E; Massie, Ashtin; Fike, David A; Schroeder, Sissel; Williams, John W

    2015-05-19

    Here we establish the timing of major flood events of the central Mississippi River over the last 1,800 y, using floodwater sediments deposited in two floodplain lakes. Shifts in the frequency of high-magnitude floods are mediated by moisture availability over midcontinental North America and correspond to the emergence and decline of Cahokia--a major late prehistoric settlement in the Mississippi River floodplain. The absence of large floods from A.D. 600 to A.D. 1200 facilitated agricultural intensification, population growth, and settlement expansion across the floodplain that are associated with the emergence of Cahokia as a regional center around A.D. 1050. The return of large floods after A.D. 1200, driven by waning midcontinental aridity, marks the onset of sociopolitical reorganization and depopulation that culminate in the abandonment of Cahokia and the surrounding region by A.D. 1350. Shifts in the frequency and magnitude of flooding may be an underappreciated but critical factor in the formation and dissolution of social complexity in early agricultural societies.

  16. Analytic description of Raman-induced frequency shift in the case of non-soliton ultrashort pulses

    Energy Technology Data Exchange (ETDEWEB)

    Bugay, Aleksandr N., E-mail: bugay_aleksandr@mail.ru [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980, Dubna, Moscow Region (Russian Federation); Khalyapin, Vyacheslav A., E-mail: slavasxi@gmail.com [Immanuel Kant Baltic Federal University, Kaliningrad, 236041 (Russian Federation); Kaliningrad State Technical University, Kaliningrad, 236000 (Russian Federation)

    2017-01-30

    Raman-induced frequency shift of ultrashort pulses have been studied extensively for the soliton propagation regime. Here we derive explicit analytic expressions for the evolution of Raman-induced frequency shift in much less studied case of non-soliton ultrashort pulses. Pulse spectra may belong to any region of group velocity dispersion including zero group dispersion point. The analysis is based on the moment method. Obtained expressions fit well to the numerical solution of the nonlinear wave equation. - Highlights: • Explicit analytic formulas for the evolution of Raman-induced frequency shift are derived in the case of non-soliton pulses. • Dynamics of non-soliton ultrashort pulses in the cases of positive and zero group dispersion is considered. • The deceleration and the saturation of Raman-induced frequency shift are analyzed. • The calculation relies on the moment method and fit well to the numerical solution of the nonlinear wave equation.

  17. Nonnegative Matrix Factorization of time frequency representation of vibration signal for local damage detection - comparison of algorithms

    Science.gov (United States)

    Wodecki, Jacek

    2018-01-01

    Local damage detection in rotating machine elements is very important problem widely researched in the literature. One of the most common approaches is the vibration signal analysis. Since time domain processing is often insufficient, other representations are frequently favored. One of the most common one is time-frequency representation hence authors propose to separate internal processes occurring in the vibration signal by spectrogram matrix factorization. In order to achieve this, it is proposed to use the approach of Nonnegative Matrix Factorization (NMF). In this paper three NMF algorithms are tested using real and simulated data describing single-channel vibration signal acquired on damaged rolling bearing operating in drive pulley in belt conveyor driving station. Results are compared with filtration using Spectral Kurtosis, which is currently recognized as classical method for impulsive information extraction, to verify the validity of presented methodology.

  18. Impact-based piezoelectric energy harvester for multidimensional, low-level, broadband, and low-frequency vibrations

    Science.gov (United States)

    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.

  19. Damping of vibrational excitations in glasses at terahertz frequency: The case of 3-methylpentane

    KAUST Repository

    Baldi, Giacomo

    2017-10-24

    We report a compared analysis of inelastic X ray scattering (IXS) and of low frequency Raman data of glassy 3-methylpentane. The IXS spectra have been analysed allowing for the existence of two distinct excitations at each scattering wavevector obtaining a consistent interpretation of the spectra. In particular, this procedure allows us to interpret the linewidth of the modes in terms of a simple model which relates them to the width of the first sharp diffraction peak in the static structure factor. In this model, the width of the modes arises from the blurring of the dispersion curves which increases approaching the boundary of the first pseudo-Brillouin zone. The position of the boson peak contribution to the density of vibrational states derived from the Raman scattering measurements is in agreement with the interpretation of the two excitations in terms of a longitudinal mode and a transverse mode, the latter being a result of the mixed character of the transverse modes away from the center of the pseudo-Brillouin zone.

  20. Ultrahigh-frequency microwave phase shifts mediated by ultrafast dynamics in quantum-dot semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2010-01-01

    We present a novel scheme to achieve tunable microwave phase shifts at frequencies exceeding 100 GHz based on wavelength conversion induced by high-speed cross-gain modulation in quantum-dot semiconductor optical amplifiers.......We present a novel scheme to achieve tunable microwave phase shifts at frequencies exceeding 100 GHz based on wavelength conversion induced by high-speed cross-gain modulation in quantum-dot semiconductor optical amplifiers....

  1. Proton Transfer and Low-Barrier Hydrogen Bonding: a Shifting Vibrational Landscape Dictated by Large Amplitude Tunneling

    Science.gov (United States)

    Vealey, Zachary; Foguel, Lidor; Vaccaro, Patrick

    2017-06-01

    Our fundamental understanding of synergistic hydrogen-bonding and proton-transfer phenomena has been advanced immensely by studies of model systems in which the coherent transduction of hydrons is mediated by two degenerate equilibrium configurations that are isolated from one another by a potential barrier of substantial height. This topography advantageously affords unambiguous signatures for the underlying state-resolved dynamics in the form of tunneling-induced spectral bifurcations, the magnitudes of which encode both the overall efficacy and the detailed mechanism of the unimolecular transformation. As a prototypical member of this class of compounds, 6-hydroxy-2-formylfulvene (HFF) supports an unusual quasi-linear O-H...O \\leftrightarrow O...H-O reaction coordinate that presents a minimal impediment to proton migration - a situation commensurate with the concepts of low-barrier hydrogen bonding (which are characterized by great strength, short distance, and a vanishingly small barrier for hydron migration). A variety of fluorescence-based, laser-spectroscopic probes have been deployed in a cold supersonic free-jet expansion to explore the vibrational landscape and anomalously large tunneling-induced shifts that dominate the ˜{X}^{1}A_{1} potential-energy surface of HFF, thus revealing the most rapid proton tunneling ever reported for a molecular ground state (τ_{pt}≤120fs). The surprising efficiency of such tunneling-mediated processes stems from proximity of the zero-point level to the barrier crest and produces a dramatic alteration in the canonical pattern of vibrational features that reflects, in part, the subtle transition from quantum-mechanical barrier penetration to classical over-the-barrier dynamics. The ultrafast proton-transfer regime that characterizes the ˜{X}^{1}A_{1} manifold will be juxtaposed against analogous findings for the lowest-lying singlet excited state ˜{A}^{1}B_{2} (π*←π), where a marked change in the nature of the

  2. Low-frequency vibration isolation in six degrees of freedom: the Hummingbird

    NARCIS (Netherlands)

    Rijnveld, N.; Braber, R. van den; Fraanje, P.R.; Dool, T.C. van den

    2010-01-01

    TNO Science and Industry and MECAL have developed a six degree of freedom vibration isolation system that suppresses both floor vibrations and direct forces on a table top. The achieved reduction of transmissibility and compliance is 40 dB between 1 and 50 Hz in vertical direction, and 30 dB between

  3. Low-frequency vibrational excitations in the amorphous and crystalline states of triphenyl phosphite: A neutron and Raman scattering investigation

    Science.gov (United States)

    Hédoux, Alain; Derollez, Patrick; Guinet, Yannick; Dianoux, Albert José; Descamps, Marc

    2001-04-01

    The vibrational density of states in the triphenyl phosphite, measured by inelastic neutron scattering, were obtained during isothermal aging at Ta=210, 213, and 216 K. The low-frequency ωn behavior of the vibrational density of states was observed to be time dependent. This is suggestive of an abortive crystallization process because the ω exponent has not reached the characteristic value of the crystalline state (n=2) at the end of the transformation. The confrontation of inelastic neutron scattering and Raman data in the low-frequency range reveals interesting information about the structural organization in the liquid, the glass, the undercooled liquid, and the glacial state, through the observation of the boson peak.

  4. Theoretical study of the frequency shift in bimodal FM-AFM by fractional calculus

    Directory of Open Access Journals (Sweden)

    Elena T. Herruzo

    2012-03-01

    Full Text Available Bimodal atomic force microscopy is a force-microscopy method that requires the simultaneous excitation of two eigenmodes of the cantilever. This method enables the simultaneous recording of several material properties and, at the same time, it also increases the sensitivity of the microscope. Here we apply fractional calculus to express the frequency shift of the second eigenmode in terms of the fractional derivative of the interaction force. We show that this approximation is valid for situations in which the amplitude of the first mode is larger than the length of scale of the force, corresponding to the most common experimental case. We also show that this approximation is valid for very different types of tip–surface forces such as the Lennard-Jones and Derjaguin–Muller–Toporov forces.

  5. Theoretical study of the frequency shift in bimodal FM-AFM by fractional calculus.

    Science.gov (United States)

    Herruzo, Elena T; Garcia, Ricardo

    2012-01-01

    Bimodal atomic force microscopy is a force-microscopy method that requires the simultaneous excitation of two eigenmodes of the cantilever. This method enables the simultaneous recording of several material properties and, at the same time, it also increases the sensitivity of the microscope. Here we apply fractional calculus to express the frequency shift of the second eigenmode in terms of the fractional derivative of the interaction force. We show that this approximation is valid for situations in which the amplitude of the first mode is larger than the length of scale of the force, corresponding to the most common experimental case. We also show that this approximation is valid for very different types of tip-surface forces such as the Lennard-Jones and Derjaguin-Muller-Toporov forces.

  6. Bragg-Scattering Four-Wave Mixing in Nonlinear Fibers with Intracavity Frequency-Shifted Laser Pumps

    Directory of Open Access Journals (Sweden)

    Katarzyna Krupa

    2012-01-01

    Full Text Available We experimentally study four-wave mixing in highly nonlinear fibers using two independent and partially coherent laser pumps and a third coherent signal. We focus our attention on the Bragg-scattering frequency conversion. The two pumps were obtained by amplifying two Intracavity frequency-shifted feedback lasers working in a continuous wave regime.

  7. Bandwidth Widening of Piezoelectric Cantilever Beam Arrays by Mass-Tip Tuning for Low-Frequency Vibration Energy Harvesting

    Directory of Open Access Journals (Sweden)

    Eduard Dechant

    2017-12-01

    Full Text Available Wireless sensor networks usually rely on internal permanent or rechargeable batteries as a power supply, causing high maintenance efforts. An alternative solution is to supply the entire system by harvesting the ambient energy, for example, by transducing ambient vibrations into electric energy by virtue of the piezoelectric effect. The purpose of this paper is to present a simple engineering approach for the bandwidth optimization of vibration energy harvesting systems comprising multiple piezoelectric cantilevers (PECs. The frequency tuning of a particular cantilever is achieved by changing the tip mass. It is shown that the bandwidth enhancement by mass tuning is limited and requires several PECs with close resonance frequencies. At a fixed frequency detuning between subsequent PECs, the achievable bandwidth shows a saturation behavior as a function of the number of cantilevers used. Since the resonance frequency of each PEC is different, the output voltages at a particular excitation frequency have different amplitudes and phases. A simple power-transfer circuit where several PECs with an individual full wave bridge rectifier are connected in parallel allows one to extract the electrical power close to the theoretical maximum excluding the diode losses. The experiments performed on two- and three-PEC arrays show reasonable agreement with simulations and demonstrate that this power-transfer circuit additionally influences the frequency dependence of the harvested electrical power.

  8. Capturing inhomogeneous broadening of the -CN stretch vibration in a Langmuir monolayer with high-resolution spectra and ultrafast vibrational dynamics in sum-frequency generation vibrational spectroscopy (SFG-VS)

    Energy Technology Data Exchange (ETDEWEB)

    Velarde Ruiz Esparza, Luis A.; Wang, Hongfei

    2013-08-28

    Even though in principle the frequency-domain and time-domain spectroscopic measurement should generate identical information for a given molecular system, inhomogeneous character of surface vibrations in the sum-frequency generation vibrational spectroscopy (SFG-VS) studies has only been studied with the time-domain SFGVS by mapping the decay of the vibrational polarization using ultrafast lasers, due to the lack of SFG vibrational spectra with high enough spectral resolution and accurate enough line shape. Here with recently developed high-resolution broadband SFG-VS (HR-BB-SFG-VS) we show that the inhomogeneous line shape can be obtained in the frequency-domain, for the anchoring CN stretch of the 4-n-octyl-4'-cyanobiphenyl (8CB) Langmuir monolayer at the air-water interface, and that an excellent agreement with the time-domain SFG free-induction-decay (FID) results can be established. We found that the 8CB CN stretch spectrum consists of a single peak centered at 2234.00 + * 0.01 cm-1 with a total line width of 10.9 + - 0.3 cm-1 at half maximum. The Lorentzian contribution accounts only for 4:7 + -0:4 cm-1 to this width and the Gaussian (inhomogeneous) broadening for as much as 8:1+*0:2 cm-1. Polarization analysis of the -CN spectra showed that the -CN group is tilted 57 + - 2 degrees from the surface normal. The large heterogeneity in the -CN spectrum is tentatively attributed to the -CN group interactions with the interfacial water molecules penetrated/accomodated into the 8CB monolayer, a unique phenomenon for the nCB Langmuir monolayers reported previously.

  9. Theoretical molecular structure, vibrational frequencies and NMR investigations of 2-[(1E-2-aza-2-(5-methyl(2-pyridylethenyl]-4-bromobenzen-1-ol

    Directory of Open Access Journals (Sweden)

    Cemal Parlak

    2012-08-01

    Full Text Available The normal mode frequencies and corresponding vibrational assignments, 1H and 13C NMR chemical shifts and structural parameters (bond lengths, bond and dihedral angles of 2-[(1E-2-aza-2-(5-methyl(2-pyridylethenyl]-4-bromobenzen-1-ol (2mpe-4bb Schiff base compound have been theoretically examined by means of Hartree-Fock (HF and Becke-3-Lee-Yang-Parr (B3LYP density functional methods with 6-31G(d and 6-311++G(d,p basis sets. Furthermore, reliable vibrational assignments have made on the basis of potential energy distribution (PED calculated and the thermodynamics functions, highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO of 2mpe-4bb have been predicted. Theoretical results have been successfully compared with available experimental data in the literature. Regarding the calculations, 2mpe-4bb prefers enol-imine form and DFT method is superior to HF approach except for predicting bond lengths.DOI: http://dx.doi.org/10.4314/bcse.v26i2.11

  10. Layer-number dependent high-frequency vibration modes in few-layer transition metal dichalcogenides induced by interlayer couplings

    Science.gov (United States)

    Tan, Qing-Hai; Zhang, Xin; Luo, Xiang-Dong; Zhang, Jun; Tan, Ping-Heng

    2017-03-01

    Two-dimensional transition metal dichalcogenides (TMDs) have attracted extensive attention due to their many novel properties. The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds, while van der Waals interactions combine the layers together. This makes its lattice dynamics layer-number dependent. The evolutions of ultralow frequency ( 50 cm-1) vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes, known as Davydov splitting. Such Davydov splitting can be well described by a van der Waals model, which directly links the splitting with the interlayer coupling. Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials. Project supported by the National Basic Research Program of China (No. 2016YFA0301200), the National Natural Science Foundation of China (Nos. 11225421, 11474277, 11434010, 61474067, 11604326, 11574305 and 51527901), and the National Young 1000 Talent Plan of China.

  11. Balancing Vibrations at Harmonic Frequencies by Injecting Harmonic Balancing Signals into the Armature of a Linear Motor/Alternator Coupled to a Stirling Machine

    Science.gov (United States)

    Holliday, Ezekiel S. (Inventor)

    2014-01-01

    Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

  12. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization

    Directory of Open Access Journals (Sweden)

    Laurent Segers

    2015-07-01

    Full Text Available This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy.

  13. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization.

    Science.gov (United States)

    Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris

    2015-07-30

    This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy.

  14. Evaluation of the CERN Super Proton Synchrotron longitudinal impedance from measurements of the quadrupole frequency shift

    Directory of Open Access Journals (Sweden)

    A. Lasheen

    2017-06-01

    Full Text Available Longitudinal instabilities are one of the main limitations in the CERN Super Proton Synchrotron (SPS to reach the beam parameters required for the High Luminosity LHC project. In preparation to the SPS upgrade, possible remedies are studied by performing macroparticle simulations using the machine impedance model obtained from electromagnetic simulations and measurements. To benchmark the impedance model, the results of simulations are compared with various beam measurements. In this study, the reactive part of the impedance was probed by measuring the quadrupole frequency shift with intensity, obtained from bunch length oscillations at mismatched injection into the SPS. This method was applied over many last years to follow up the evolution of the SPS impedance, injecting bunches with the same bunch length. A novel approach, giving significantly more information, consists in varying the injected bunch length. The comparison of these measurements with macroparticle simulations allowed us to test the existing model, identify some missing SPS impedance and to obtain its possible dependence on frequency.

  15. Three-Dimensional Vibration Isolator for Suppressing High-Frequency Responses for Sage III Contamination Monitoring Package (CMP)

    Science.gov (United States)

    Li, Y.; Cutright, S.; Dyke, R.; Templeton, J.; Gasbarre, J.; Novak, F.

    2015-01-01

    The Stratospheric Aerosol and Gas Experiment (SAGE) III - International Space Station (ISS) instrument will be used to study ozone, providing global, long-term measurements of key components of the Earth's atmosphere for the continued health of Earth and its inhabitants. SAGE III is launched into orbit in an inverted configuration on SpaceX;s Falcon 9 launch vehicle. As one of its four supporting elements, a Contamination Monitoring Package (CMP) mounted to the top panel of the Interface Adapter Module (IAM) box experiences high-frequency response due to structural coupling between the two structures during the SpaceX launch. These vibrations, which were initially observed in the IAM Engineering Development Unit (EDU) test and later verified through finite element analysis (FEA) for the SpaceX launch loads, may damage the internal electronic cards and the Thermoelectric Quartz Crystal Microbalance (TQCM) sensors mounted on the CMP. Three-dimensional (3D) vibration isolators were required to be inserted between the CMP and IAM interface in order to attenuate the high frequency vibrations without resulting in any major changes to the existing system. Wire rope isolators were proposed as the isolation system between the CMP and IAM due to the low impact to design. Most 3D isolation systems are designed for compression and roll, therefore little dynamic data was available for using wire rope isolators in an inverted or tension configuration. From the isolator FEA and test results, it is shown that by using the 3D wire rope isolators, the CMP high-frequency responses have been suppressed by several orders of magnitude over a wide excitation frequency range. Consequently, the TQCM sensor responses are well below their qualification environments. It is indicated that these high-frequency responses due to the typical instrument structural coupling can be significantly suppressed by a vibration passive control using the 3D vibration isolator. Thermal and contamination

  16. Non-Gaussian statistics of amide I mode frequency fluctuation of N-methylacetamide in methanol solution: Linear and nonlinear vibrational spectra

    Science.gov (United States)

    Kwac, Kijeong; Lee, Hochan; Cho, Minhaeng

    2004-01-01

    By carrying out molecular dynamics simulations of an N-methylacetamide (NMA) in methanol solution, the amide I mode frequency fluctuation and hydrogen bonding dynamics were theoretically investigated. Combining an extrapolation formula developed from systematic ab initio calculation studies of NMA-(CH3OH)n clusters with a classical molecular dynamics simulation method, we were able to quantitatively describe the solvatochromic vibrational frequency shift induced by the hydrogen-bonding interaction between NMA and solvent methanol. It was found that the fluctuating amide I mode frequency distribution is notably non-Gaussian and it can be decomposed into two Gaussian peaks that are associated with two distinctively different solvation structures. The ensemble-average-calculated linear response function associated with the IR absorption is found to be oscillating, which is in turn related to the doublet amide I band shape. Numerically calculated infrared absorption spectra are directly compared with experiment and the agreement was found to be excellent. By using the Onsager's regression hypothesis, the rate constants of the interconversion process between the two solvation structures were obtained. Then, the nonlinear response functions associated with two-dimensional infrared pump-probe spectroscopy were simulated. The physics behind the two-dimensional line shape and origin of the cross peaks in the time-resolved pump-probe spectra is explained and the result is compared with 2D spectra experimentally measured recently by Woutersen et al. [S. Woutersen, Y. Mu, G. Stock, and P. Hamm, Chem. Phys. 266, 137 (2001)].

  17. Relationship Between Psychomotor Efficiency and Sensation Seeking of People Exposed to Noise and Low Frequency Vibration Stimuli

    Science.gov (United States)

    Korchut, Aleksander; Kowalska-Koczwara, Alicja; Romanska – Zapała, Anna; Stypula, Krzysztof

    2017-10-01

    At the workplace of the machine operator, low frequency whole body and hand- arm vibrations are observed. They occur together with noise. Whole body vibration in the range of 3-25 Hz are detrimental to the human body due to the location of the resonant frequency of large organs of the human body in this range. It can be assumed that for this reason people working every day in such conditions can have reduced working efficiency. The influence of low frequency vibration and noise on the human body leads to both physiological and functional changes. The result of the impact of noise and vibration stimuli depends largely on the specific characteristics of the objects, which include among other personality traits, temperament and emotional factor. The pilot study conducted in the laboratory was attended by 30 young men. The aim of the study was to look for correlations between the need for stimulation of the objects and their psychomotor efficiency in case of vibration exposure and vibration together with noise exposure in variable conditions task. The need for stimulation of the objects as defined in the study is based on theoretical assumptions of one dimensional model of temperament developed by Marvin Zuckerman. This theory defines the need for stimulation as the search for different, new, complex and intense sensations, as well as the willingness to take risks. The aim of research was to verify if from four factors such as: the search for adventure and horror, sensation seeking, disinhibition and susceptibility to boredom, we can choose the ones that in conjunction with varying operating conditions, may significantly determine the efficiency of the task situation. The objects performed the test evaluation of their motor skills which consisted in keeping the cursor controlled by a joystick through the path. The number of exceeds of the cursor beyond the path and its maximum deviation was recorded. The collected data were used to determine the correlation between the

  18. Analytical and experimental comparisons between the frequency-modulated–frequency-shift measurement and the pulsed-wave–time-shift measurement Doppler systems

    DEFF Research Database (Denmark)

    Wilhjelm, Jens Erik; Pedersen, P. C.

    1996-01-01

    is in this paper compared with its PW counterpart, the Pulsed Wave - time shift measurement (PW-tsm) Doppler system. When using transmitted PW and FM signals with a Gaussian envelope, the parallelism between the two systems can be stated explicitly, and comparison be made between the main performance indices...

  19. A computational investigation of the red and blue shifts in hydrogen ...

    Indian Academy of Sciences (India)

    MITRADIP Das

    Abstract. The present work reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic ...

  20. A computational investigation of the red and blue shifts in hydrogen ...

    Indian Academy of Sciences (India)

    The presentwork reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic parameters ...

  1. Vibrational sum‐frequency generation as a probe for composition, chemical reactivity, and film formation dynamics of the sea surface nanolayer

    National Research Council Canada - National Science Library

    Laβ, Kristian; Kleber, Joscha; Friedrichs, Gernot

    2010-01-01

    Vibrational Sum Frequency Generation (VSFG) is a surface sensitive nonlinear laser spectroscopic technique, which has been widely used in physics and physical chemistry to investigate interface processes and heterogeneous chemistry...

  2. Comparisons of the Structure of Water at Neat Oil/Water and Air/Water Interfaces as Determined by Vibrational Sum Frequency Generation

    National Research Council Canada - National Science Library

    Gragson, D

    1997-01-01

    We have employed vibrational sum frequency generation (VSFG) to investigate the structure of water at neat oil/water and air/water interfaces through the OH stretching modes of the interfacial water molecules...

  3. Coherent control of flexural vibrations in dual-nanoweb fibers using phase-modulated two-frequency light

    Science.gov (United States)

    Koehler, J. R.; Noskov, R. E.; Sukhorukov, A. A.; Novoa, D.; Russell, P. St. J.

    2017-12-01

    Coherent control of the resonant response in spatially extended optomechanical structures is complicated by the fact that the optical drive is affected by the backaction from the generated phonons. Here we report an approach to coherent control based on stimulated Raman-like scattering, in which the optical pressure can remain unaffected by the induced vibrations even in the regime of strong optomechanical interactions. We demonstrate experimentally coherent control of flexural vibrations simultaneously along the whole length of a dual-nanoweb fiber, by imprinting steps in the relative phase between the components of a two-frequency pump signal, the beat frequency being chosen to match a flexural resonance. Furthermore, sequential switching of the relative phase at time intervals shorter than the lifetime of the vibrations reduces their amplitude to a constant value that is fully adjustable by tuning the phase modulation depth and switching rate. The results may trigger new developments in silicon photonics, since such coherent control uniquely decouples the amplitude of optomechanical oscillations from power-dependent thermal effects and nonlinear optical loss.

  4. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    Directory of Open Access Journals (Sweden)

    X. H. Liu

    2015-10-01

    Full Text Available We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  5. Analytical study of the frequency shifts of micro and nano clamped–clamped beam resonators due to an added mass

    KAUST Repository

    Bouchaala, Adam M.

    2016-03-18

    We present analytical formulations to calculate the induced resonance frequency shifts of electrically actuated clamped–clamped micro and nano (Carbon nanotube) beams due to an added mass. Based on the Euler–Bernoulli beam theory, we investigate the linear dynamic responses of the beams added masses, which are modeled as discrete point masses. Analytical expressions based on perturbation techniques and a one-mode Galerkin approximation are developed to calculate accurately the frequency shifts under a DC voltage as a function of the added mass and position. The analytical results are compared to numerical solution of the eigenvalue problem. Results are shown for the fundamental as well as the higher-order modes of the beams. The results indicate a significant increase in the frequency shift, and hence the sensitivity of detection, when scaling down to nano scale and using higher-order modes. © 2016 Springer Science+Business Media Dordrecht

  6. Optimization of linear zigzag insert metastructures for low-frequency vibration attenuation using genetic algorithms

    Science.gov (United States)

    Abdeljaber, Osama; Avci, Onur; Kiranyaz, Serkan; Inman, Daniel J.

    2017-02-01

    Vibration suppression remains a crucial issue in the design of structures and machines. Recent studies have shown that with the use of metamaterial inspired structures (or metastructures), considerable vibration attenuation can be achieved. Optimization of the internal geometry of metastructures maximizes the suppression performance. Zigzag inserts have been reported to be efficient for vibration attenuation. It has also been reported that the geometric parameters of the inserts affect the vibration suppression performance in a complex manner. In an attempt to find out the most efficient parameters, an optimization study has been conducted on the linear zigzag inserts and is presented here. The research reported in this paper aims at developing an automated method for determining the geometry of zigzag inserts through optimization. This genetic algorithm based optimization process searches for optimal zigzag designs which are properly tuned to suppress vibrations when inserted in a specific host structure (cantilever beam). The inserts adopted in this study consist of a cantilever zigzag structure with a mass attached to its unsupported tip. Numerical simulations are carried out to demonstrate the efficiency of the proposed zigzag optimization approach.

  7. Collective excitations in liquid DMSO : FIR spectrum, Low frequency vibrational density of states and ultrafast dipolar solvation dynamics

    CERN Document Server

    Hazra, Milan

    2016-01-01

    Valuable dynamical and structural information about neat liquid DMSO at ambient conditions can be obtained through study of low frequency vibrations in the far infrared (FIR), that is, terahertz regime. For DMSO, collective excitations as well as single molecule stretches and bends have been measured by different kinds of experiments such as OHD-RIKES and terahertz spectroscopy. In the present work we investigate the intermolecular vibrational spectrum of DMSO through three different computational techniques namely (i) the far-infra red spectrum obtained through Fourier transform of total dipole moment auto time correlation function, (ii) from Fourier transform of the translational and angular velocity time autocorrelation functions and a (iii) quenched normal mode analysis of the parent liquid at 300K. The three spectrum, although exhibit differences among each other, reveal similar features which are in good, semi-quantitative, agreement with experimental results. Study of participation ratio of the density...

  8. A laser-cooled cesium fountain frequency standard and a measurement of the frequency shift due to ultra-cold collisions

    Science.gov (United States)

    Gibble, Kurt; Kasapi, Steven; Chu, Steven

    1993-01-01

    A frequency standard based on an atomic fountain of cesium atoms may have an accuracy of 10(exp -16) due to longer interaction times and smaller anticipated systematic errors. All of the known systematic effects that now limit the accuracy of the Cs frequency standard increase either linearly or as some higher power of the atom's velocity. The one systematic frequency shift which is dramatically different is the frequency shift due to the collisions between the laser cooled atoms. At a temperature of a few micro-K, the de Broglie wavelength (lambda(sub deB) = h/p, where h is Planck's constant and p is the momentum of the atom) is much larger than the scale of the interatomic potential. Under these conditions the collision cross sections can be as large as (lambda(sub deB)(sup 2))/Pi and the frequency shift due to these collisions was recently calculated. In our Cs atomic fountain, we laser cooled and trapped 10(exp 10) Cs atoms in 0.4 s. By shifting the frequencies of the laser beams, the atoms were launched upwards at 2.5 m/s and a fraction of the atoms were optically pumped into the F=3 ground state. The unwanted atoms in the F=4 ground state were removed from the fountain with radiation pressure from a laser beam tuned to excite only those atoms. The Cs atoms in the F=3 state traveled ballistically upwards, were excited by the microwave cavity, and then returned back through the same cavity in the atomic fountain configuration. By varying the cold atom density, a density dependent shift of -12.9 +/- 0.7 mHz or -1.4 x 10-12 for an average fountain density of (2.7 +/- 1.5) 10(exp 9) atoms/cm(sup 3) was measured.

  9. Determination of vibration frequency depending on abrasive mass flow rate during abrasive water jet cutting

    Czech Academy of Sciences Publication Activity Database

    Hreha, P.; Radvanská, A.; Hloch, Sergej; Peržel, V.; Krolczyk, G.; Monková, K.

    2014-01-01

    Roč. 77, 1-4 (2014), s. 763-774 ISSN 0268-3768 Institutional support: RVO:68145535 Keywords : Abrasive water jet * Abrasive mass flow rate * Vibration Subject RIV: JQ - Machines ; Tools Impact factor: 1.458, year: 2014 http://link.springer.com/article/10.1007%2Fs00170-014-6497-9#page-1

  10. Vibration-induced displacement using high-frequency resonators and friction layers

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    1998-01-01

    A mathematical model is set up to quantify vibration-induced motions of a slider with an imbedded resonator. A simple approximate expression is presented for predicting average velocities of the slider, agreeing fairly well with numerical integration of the full equations of motion. The simple ex...

  11. Natural Frequencies and Modal Damping Ratios Identification of Civil Structures from Ambient Vibration Data

    Directory of Open Access Journals (Sweden)

    Minh-Nghi Ta

    2006-01-01

    Full Text Available Damping is a mechanism that dissipates vibration energy in dynamic systems and plays a key role in dynamic response prediction, vibration control as well as in structural health monitoring during service. In this paper a time domain and a time-scale domain approaches are used for damping estimation of engineering structures, using ambient response data only. The use of tests under ambient vibration is increasingly popular today because they allow to measure the structural response in service. In this paper we consider two engineering structures excited by ambient forces. The first structure is the 310 m tall TV tower recently constructed in the city of Nanjing in China. The second example concerns the Jinma cable-stayed bridge that connects Guangzhou and Zhaoqing in China. It is a single tower, double row cable-stayed bridge supported by 112 stay cables. Ambient vibration of each cable is carried out using accelerometers. From output data only, the modal parameter are extracted using a subspace method and the wavelet transform method.

  12. MRI thermometry in phantoms by use of the proton resonance frequency shift method: application to interstitial laser thermotherapy

    OpenAIRE

    Olsrud, Johan; Wirestam, Ronnie; Brockstedt, Sara; Nilsson, Annika M K; Tranberg, Karl-Göran; Ståhlberg, Freddy; Persson, Bertil R

    1998-01-01

    In this work the temperature dependence of the proton resonance frequency was assessed in agarose gel with a high melting temperature (95 degrees C) and in porcine liver in vitro at temperatures relevant to thermotherapy (25-80 degrees C). Furthermore, an optically tissue-like agarose gel phantom was developed and evaluated for use in MRI. The phantom was used to visualize temperature distributions from a diffusing laser fibre by means of the proton resonance frequency shift method. An approx...

  13. Benchmark Structures and Harmonic Vibrational Frequencies Near the CCSD(T) Complete Basis Set Limit for Small Water Clusters: (H2O)n = 2, 3, 4, 5, 6.

    Science.gov (United States)

    Howard, J Coleman; Tschumper, Gregory S

    2015-05-12

    A series of (H2O)n clusters ranging from the dimer to the hexamer have been characterized with the CCSD(T) and the 2-body:Many-body CCSD(T):MP2 methods near the complete basis set (CBS) limit to generate benchmark-quality optimized structures and harmonic vibrational frequencies for these important systems. Quadruple-ζ correlation-consistent basis sets that augment the O atoms with diffuse functions have been employed in the analytic computation of harmonic vibrational frequencies for the global minima of the dimer, trimer, tetramer, and pentamer as well as the ring, book, cage, and prism isomers of the hexamer. Prior calibration [J. Chem. Phys. 2013, 139, 184113 and J. Chem. Theory Comput. 2014, 10, 5426] suggests that harmonic frequencies computed with this approach will lie within a few cm(-1) of the canonical CCSD(T) CBS limit. These data are used as reference values to gauge the performance of harmonic frequencies obtained with other ab initio methods (e.g., LCCSD(T) and MP2) and water potentials (e.g., TTM3-F and WHBB). This comparison reveals that it is far more challenging to converge harmonic vibrational frequencies for the bound OH stretching modes in these (H2O)n clusters to the CCSD(T) CBS limit than the free OH stretches, the n intramonomer HOH bending modes and even the 6n - 6 intermonomer modes. Deviations associated with the bound OH stretching harmonic frequencies increase rapidly with the size of the cluster for all methods and potentials examined, as do the corresponding frequency shifts relative to the monomer OH stretches.

  14. Molecular structures and vibrational frequencies of xanthine and its methyl derivatives (caffeine and theobromine) by ab initio Hartree-Fock and density functional theory calculations

    Science.gov (United States)

    Ucun, Fatih; Sağlam, Adnan; Güçlü, Vesile

    2007-06-01

    The molecular structures, vibrational frequencies and corresponding vibrational assignments of xanthine and its methyl derivatives (caffeine and theobromine) have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-31G(d, p) basis set level. The calculations were utilized to the CS symmetries of the molecules. The obtained vibrational frequencies and optimised geometric parameters (bond lengths and bond angles) were seen to be well agreement with the experimental data. The used scale factors which have been obtained the ratio of the frequency values of the strongest peaks in the calculated and experimental spectra seem to cause the gained vibrations well corresponding to the experimental ones. Theoretical infrared intensities and Raman activities are also reported.

  15. Effects of cations and cholesterol with sphingomyelin membranes investigated by high-resolution broadband sum frequency vibrational spectroscopy

    Science.gov (United States)

    Zhang, Zhen; Feng, Rong-juan; Li, Yi-yi; Liu, Ming-hua; Guo, Yuan

    2017-08-01

    Sphingomyelin(SM) is specifically enriched in the plasma membrane of mammalian cells. Its molecular structure is compose by N-acyl-Derythro-sphingosylphosphorylcholine. The function of the SM related to membrane signaling and protein trafficking are relied on the interactions of the SM, cations, cholesterol and proteins. In this report, the interaction of three different nature SMs, cations and cholesterol at air/aqueous interfaces studied by high-resolution broadband sum frequency vibrational spectroscopy, respectively. Our results shed lights on understanding the relationship between SMs monolayer, cholesterol and Cations.

  16. Properties of axial or torsional free-vibration frequency of rods

    Science.gov (United States)

    Segenreich, S. A.; Rizzi, P.

    1975-01-01

    The investigation reported shows that for a clamped rod with an odd number of degrees of freedom, the middle frequency is independent of any nonuniformity in the area distribution. The frequencies in the lower half of the spectrum of a rod are found to be conjugate to the frequencies in the upper half. In the case of a design modification which leaves a certain frequency in the lower half spectrum unchanged, the conjugate frequency in the upper half will also remain unchanged.

  17. Impact of frequency modulation ratio on capacitor cells balancing in phase-shifted PWM based chain-link STATCOM

    DEFF Research Database (Denmark)

    Behrouzian, Ehsan; Bongiorno, Massimo; Teodorescu, Remus

    2014-01-01

    The purpose of this paper is to investigate the impact of switching harmonics on the instantaneous power that flows in the cells of a chain-link based STATCOM when using Phase-Shifted PWM. Two different cases are investigated for the converter cells: low, and high switching frequency. It is shown...

  18. Ultrafast OH-stretching frequency shifts of hydrogen- bonded 2-naphthol photoacid-base complexes in solution

    Directory of Open Access Journals (Sweden)

    Batista VictorS.

    2013-03-01

    Full Text Available We characterize the transient solvent-dependent OH-stretching frequency shifts of photoacid 2-naphthol hydrogen-bonded with CH3CN in the S0- and S1-states using a combined experimental and theoretical approach, and disentangle specific hydrogen-bonding contributions from nonspecific dielectric response.

  19. Broadband-tunable LP$_{01}$ mode frequency shifting by Raman coherence waves in H$_2$-filled hollow-core PCF

    CERN Document Server

    Bauerschmidt, S T; Abdolvand, Amir; Russell, Philip S J

    2015-01-01

    When a laser pump beam of sufficient intensity is incident on a Raman-active medium such as hydrogen gas, a strong Stokes signal, red-shifted by the Raman transition frequency {\\Omega}$_R$, is generated. This is accompanied by the creation of a "coherence wave" of synchronized molecular oscillations with wavevector {\\Delta}{\\beta} determined by the optical dispersion. Within its lifetime, this coherence wave can be used to shift by {\\Omega}$_R$ the frequency of a third "mixing" signal, provided phase-matching is satisfied, i.e., {\\Delta}{\\beta} is matched. Conventionally this can be arranged using non-collinear beams or higher-order waveguide modes. Here we report collinear phase-matched frequency shifting of an arbitrary mixing signal using only the fundamental LP$_{01}$ modes of a hydrogen-filled hollow-core PCF. This is made possible by the S-shaped dispersion curve that occurs around the pressure-tunable zero dispersion point. Phase-matched frequency shifting by 125 THz is possible from the UV to the near...

  20. The Effect of Doppler Frequency Shift, Frequency Offset of the Local Oscillators, and Phase Noise on the Performance of Coherent OFDM Receivers

    Science.gov (United States)

    Xiong, Fuqin; Andro, Monty

    2001-01-01

    This paper first shows that the Doppler frequency shift affects the frequencies of the RF carrier, subcarriers, envelope, and symbol timing by the same percentage in an Orthogonal Frequency Division Multiplexing (OFDM) signal or any other modulated signals. Then the SNR degradation of an OFDM system due to Doppler frequency shift, frequency offset of the local oscillators and phase noise is analyzed. Expressions are given and values for 4-, 16-, 64-, and 256-QAM OFDM systems are calculated and plotted. The calculations show that the Doppler shift of the D3 project is about 305 kHz, and the degradation due to it is about 0.01 to 0.04 dB, which is negligible. The degradation due to frequency offset and phase noise of local oscillators will be the main source of degradation. To keep the SNR degradation under 0.1 dB, the relative frequency offset due to local oscillators must be below 0.01 for the 16 QAM-OFDM. This translates to an offset of 1.55 MHz (0.01 x 155 MHz) or a stability of 77.5 ppm (0.01 x 155 MHz/20 GHz) for the DI project. To keep the SNR degradation under 0.1 dB, the relative linewidth (0) due to phase noise of the local oscillators must be below 0.0004 for the 16 QAM-OFDM. This translates to a linewidth of 0.062 MHz (0.0004 x 155 MHz) of the 20 GHz RIF carrier. For a degradation of 1 dB, beta = 0.04, and the linewidth can be relaxed to 6.2 MHz.

  1. Combined effects of phase-shift and power distribution on efficiency of dual-high-frequency sonochemistry.

    Science.gov (United States)

    Waldo, Nicholas B; Vecitis, Chad D

    2018-03-01

    In an effort to increase the efficiency of sonochemical reactors, this study investigates a single-source, dual-high-frequency ultrasound reactor. Experiments were conducted with a variety of piezoelectric crystals and reactor components, and for each reactor design a range of power distributions and phase shifts between the two frequencies were evaluated. Certain dual-frequency configurations produced up to a threefold increase in sonochemical efficiency, while others yeilded no improvement over a single frequency. These results led to two significant findings. First, phase-shift had a strong effect on sonochemical efficiency for both harmonic and non-harmonic frequency combinations. Second, the most efficient dual-harmonic-frequency waveforms had a single peak per half-cycle, rather than two unique peaks. If dual-frequency, single-source ultrasound reactors are to become more efficient they must be able to consistently control the phase angle of and power distribution between harmonic waves to create an optimal waveform. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Frequency Dependence of Helioseismic Measurements of the Center-to-Limb Effect and Flow-induced Travel-time Shifts

    Science.gov (United States)

    Chen, Ruizhu; Zhao, Junwei

    2018-02-01

    Time–distance helioseismology measures acoustic travel times to infer the structure and flow field of the solar interior; however, both the mean travel times and the travel-time shifts suffer systematic center-to-limb variations, which complicate the interpretation and inversions of the time–distance measurements. In particular, the center-to-limb variation in travel-time shifts (CtoL effect) has a significant impact on the inference of the Sun’s meridional circulation, and needs to be removed from the helioseismic measurements, although the observational properties and the physical cause of the CtoL effect have yet to be investigated. In this study, we measure the CtoL effect in the frequency domain using Doppler-velocity data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, and study its properties as a function of disk-centric distance, travel distance, and frequency of acoustic waves. It is found that the CtoL effect has a significant frequency dependence—it reverses sign at a frequency around 5.4 mHz and reaches maximum at around 4.0 mHz before the sign reversal. The tendency of frequency dependence varies with disk-centric distance in a way that both the sign-reversal frequency and the maximum-value frequency decrease closer to the limb. The variation tendency does not change with travel distance, but the variation magnitude is approximately proportional to travel distance. For comparison, the flow-induced travel-time shifts show little frequency dependence. These observational properties provide more clues on the nature of the CtoL effect, and also possibly lead to new ways of effect-removal for a more robust determination of the deep meridional flow.

  3. The acute effects of local muscle vibration frequency on peak torque, rate of torque development, and EMG activity.

    Science.gov (United States)

    Pamukoff, Derek N; Ryan, Eric D; Blackburn, J Troy

    2014-12-01

    Vibratory stimuli enhance muscle activity and may be used for rehabilitation and performance enhancement. Efficacy of vibration varies with the frequency of stimulation, but the optimal frequency is unclear. The purpose of this study was to examine the effects of 30 Hz and 60 Hz local muscle vibration (LMV) on quadriceps function. Twenty healthy volunteers (age = 20.4 ± 1.4 years, mass = 68.1 ± 11.0 kg, height = 170.1 ± 8.8 cm, males = 9) participated. Isometric knee extensor peak torque (PT), rate of torque development (RTD), and electromyography (EMG) of the quadriceps were assessed followed by one of the three LMV treatments (30 Hz, 60 Hz, control) applied under voluntary contraction, and again immediately, 5, 15, and 30 min post-treatment in three counterbalanced sessions. Dependent variables were analyzed using condition by time repeated-measures ANOVA. The condition × time interaction was significant for EMG amplitude (p = 0.001), but not for PT (p=0.324) or RTD (p = 0.425). The increase in EMG amplitude following 30 Hz LMV was significantly greater than 60 Hz LMV and control. These findings suggest that 30 Hz LMV may elicit an improvement in quadriceps activation and could be used to treat quadriceps dysfunction resulting from knee pathologies. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. N-H stretching modes around 3300 wavenumber from peptide backbones observed by chiral sum frequency generation vibrational spectroscopy.

    Science.gov (United States)

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

    2014-09-01

    We present a detailed analysis of the molecular origin of the chiral sum frequency generation (SFG) signals of proteins and peptides at interfaces in the N-H stretching vibrational region. The N-H stretching can be a probe for investigating structural and functional properties of proteins, but remains technically difficult to analyze due to the overlapping with the O-H stretching of water molecules. Chiral SFG spectroscopy offers unique tools to study the N-H stretching from proteins at interfaces without interference from the water background. However, the molecular origin of the N-H stretching signals of proteins is still unclear. This work provides a justification of the origin of chiral N-H signals by analyzing the vibrational frequencies, examining chiral SFG theory, studying proton (hydrogen/deuterium) exchange kinetics, and performing optical control experiments. The results demonstrate that the chiral N-H stretching signals at ~3300 cm(-1) originate from the amide group of the protein backbones. This chiral N-H stretching signal offers an in situ, real-time, and background-free probe for interrogating the protein structures and dynamics at interfaces at the molecular level. © 2014 Wiley Periodicals, Inc.

  5. Collective excitations in liquid dimethyl sulfoxide (DMSO): FIR spectrum, low frequency vibrational density of states, and ultrafast dipolar solvation dynamics

    Science.gov (United States)

    Hazra, Milan K.; Bagchi, Biman

    2017-01-01

    Valuable dynamical and structural information about neat liquid DMSO at ambient conditions can be obtained through a study of low frequency vibrations in the far infrared (FIR), that is, terahertz regime. For DMSO, collective excitations as well as single molecule stretches and bends have been measured by different kinds of experiments such as OHD-RIKES and terahertz spectroscopy. In the present work, we investigate the intermolecular vibrational spectrum of DMSO through three different computational techniques namely (i) the far-infrared spectrum obtained through the Fourier transform of total dipole moment auto-time correlation function, (ii) from the Fourier transform of the translational and angular velocity time autocorrelation functions, and (iii) a quenched normal mode analysis of the parent liquid at 300 K. The three spectra, although exhibit differences among each other, reveal similar features which are in good, semi-quantitative, agreement with experimental results. The study of participation ratio of the density of states obtained from the normal mode analysis shows that the broad spectrum around 100 cm-1 involves collective oscillations of 300-400 molecules. Dipolar solvation dynamics exhibit ultrafast energy relaxation with an initial time constant around 157 fs which can be attributed to the coupling to the collective excitations. We compare the properties of DMSO with those of water vis-a-vis the existence of the low frequency collective modes. Last, we find that the collective excitation spectrum exhibits strong temperature dependence.

  6. Collective excitations in liquid dimethyl sulfoxide (DMSO): FIR spectrum, low frequency vibrational density of states, and ultrafast dipolar solvation dynamics.

    Science.gov (United States)

    Hazra, Milan K; Bagchi, Biman

    2017-01-14

    Valuable dynamical and structural information about neat liquid DMSO at ambient conditions can be obtained through a study of low frequency vibrations in the far infrared (FIR), that is, terahertz regime. For DMSO, collective excitations as well as single molecule stretches and bends have been measured by different kinds of experiments such as OHD-RIKES and terahertz spectroscopy. In the present work, we investigate the intermolecular vibrational spectrum of DMSO through three different computational techniques namely (i) the far-infrared spectrum obtained through the Fourier transform of total dipole moment auto-time correlation function, (ii) from the Fourier transform of the translational and angular velocity time autocorrelation functions, and (iii) a quenched normal mode analysis of the parent liquid at 300 K. The three spectra, although exhibit differences among each other, reveal similar features which are in good, semi-quantitative, agreement with experimental results. The study of participation ratio of the density of states obtained from the normal mode analysis shows that the broad spectrum around 100 cm -1 involves collective oscillations of 300-400 molecules. Dipolar solvation dynamics exhibit ultrafast energy relaxation with an initial time constant around 157 fs which can be attributed to the coupling to the collective excitations. We compare the properties of DMSO with those of water vis-a-vis the existence of the low frequency collective modes. Last, we find that the collective excitation spectrum exhibits strong temperature dependence.

  7. The Effects of Vibration Frequencies on Physical, Perceptual and Cognitive Performance

    Science.gov (United States)

    2006-10-01

    l’intégration d’un réseau multicouches de vétronique, dans lequel tous les systèmes pourront être accessibles sur chacun des postes de travail de l’équipe...fournir ainsi un environnement de travail suffisamment stable pour utiliser le réseau de vétronique. Une suspension active absorbe l’énergie dynamique...du sol , l’analyse, puis applique un signal d’énergie équivalent visant à compenser les aspérités du sol , ce qui permet d’amortir les vibrations lors

  8. A New High Frequency Injection Method Based on Duty Cycle Shifting without Maximum Voltage Magnitude Loss

    DEFF Research Database (Denmark)

    Wang, Dong; Lu, Kaiyuan; Rasmussen, Peter Omand

    2015-01-01

    The conventional high frequency signal injection method is to superimpose a high frequency voltage signal to the commanded stator voltage before space vector modulation. Therefore, the magnitude of the voltage used for machine torque production is limited. In this paper, a new high frequency...

  9. A frequency-domain multichannel optimal adaptive algorithm for active control of sound and vibration

    Science.gov (United States)

    Shen, Qun

    A frequency-domain multichannel optimal adaptive algorithm has been described in this paper. The domain multichannel optimal adaptive (FOMA) algorithm is an exact implementation of the multichannel optimal block adaptive (MOBA) algorithm in the frequency domain. It therefore converges to the same optimal solution with the same stability characteristics. The time-varying convergence factor was computed efficiently in the frequency domain to minimize a frequency-domain cost function at each step. The FMOA becomes efficient when the filter order is high. Different updating schemes, from block-by-block to sample-by-sample, can also be implemented with the proposed algorithm.

  10. The Influence of Amplitude- and Frequency-Dependent Stiffness of Rail Pads on the Random Vibration of a Vehicle-Track Coupled System

    Directory of Open Access Journals (Sweden)

    Kai Wei

    2016-01-01

    Full Text Available The nonlinear curves between the external static loads of Thermoplastic Polyurethane Elastomer (TPE rail pads and their compressive deformations were measured. A finite element model (FEM for a rail-fastener system was produced to determine the nonlinear compressive deformations of TPE rail pads and their nonlinear static stiffness under the static vehicle weight and the preload of rail fastener. Next, the vertical vehicle-track coupled model was employed to investigate the influence of the amplitude- and frequency-dependent stiffness of TPE rail pads on the vehicle-track random vibration. It is found that the static stiffness of TPE rail pads ranges from 19.1 to 37.9 kN/mm, apparently different from the classical secant stiffness of 26.7 kN/mm. Additionally, compared with the nonlinear amplitude- and frequency-dependent stiffness of rail pads, the classical secant stiffness would not only severely underestimate the random vibration acceleration levels of wheel-track coupled system at frequencies of 65–150 Hz but also alter the dominant frequency-distribution of vehicle wheel and steel rail. Considering that these frequencies of 65–150 Hz are the dominant frequencies of ground vibration accelerations caused by low-speed railway, the nonlinear amplitude- and frequency-dependent stiffness of rail pads should be taken into account in prediction of environment vibrations due to low-speed railway.

  11. Design, Simulation, and Optimization of a Frequency-Tunable Vibration Energy Harvester That Uses a Magnetorheological Elastomer

    Directory of Open Access Journals (Sweden)

    Wan Sun

    2015-01-01

    Full Text Available This study focuses on the design, simulation, and load power optimization for the development of a novel frequency-tunable electromagnetic vibrational energy harvester. The unique characteristic of a magnetorheological elastomer (MRE is utilized, that the shear modulus can be varied by changing the strength of an applied magnetic field. The electromagnetic energy harvester is fabricated, the external electric circuit is connected, and the performance is evaluated through a series of experiments. The resonant frequencies and the parasitic damping constant are measured experimentally for different tuning magnet gap distances, which validate the application of the MRE to the development of a frequency-tunable energy harvesting system. The harvested energy of the system is measured by the voltage across the load resistor. The maximum load power is attained by optimizing the external circuit connected to the coil system. The analysis results are presented for harvesting the maximum load power in terms of the coil parameters and external circuit resistance. The optimality of the load resistance is validated by comparing the analytical results with experimental results. The optimal load resistances under various resonance frequencies are also found for the design and composition of the optimal energy harvesting circuit of the energy harvester system.

  12. Low magnitude high frequency vibration promotes adipogenic differentiation of bone marrow stem cells via P38 MAPK signal.

    Directory of Open Access Journals (Sweden)

    Qian Zhao

    Full Text Available Low magnitude high frequency vibration (LMHFV has been mainly reported for its influence on the musculoskeletal system, particularly the bone tissue. In the bone structure, osteogenic activity is the main focus of study with regards to LMHFV. However, adipogenesis, another important mode of differentiation in the bone marrow cavity that might be affected by LMHFV, is much less researched. Furthermore, the molecular mechanism of how LMHFV influences adipogenesis still needs to be understood. Here, we tested the effect of LMHFV (0.3g, 40 Hz, amplitude: 50μm, 15min/d, on multipotent stem cells (MSCs, which are the common progenitors of osteogenic, chondrogenic, adipogenic and myogenic cells. It is previously shown that LMHFV promotes osteogenesis of MSCs. In this study, we further revealed its effect on adipo-differentiation of bone marrow stem cells (BMSCs and studied the underlying signaling pathway. We found that when treated with LMHFV, the cells showed a higher expression of PPARγ, C/EBPα, adiponectin and showed more oil droplets. After vibration, the protein expression of PPARγ increased, and the phosphorylation of p38 MAPK was enhanced. After treating cells with SB203580, a specific p38 inhibitor, both the protein level of PPARγ illustrated by immunofluorescent staining and the oil droplets number, were decreased. Altogether, this indicates that p38 MAPK is activated during adipogenesis of BMSCs, and this is promoted by LMHFV. Our results demonstrating that specific parameters of LMHFV promotes adipogenesis of MSCs and enhances osteogenesis, highlights an unbeneficial side effect of vibration therapy used for preventing obesity and osteoporosis.

  13. Characterization of the frequency and muscle responses of the lumbar and thoracic spines of seated volunteers during sinusoidal whole body vibration.

    Science.gov (United States)

    Baig, Hassam A; Dorman, Daniel B; Bulka, Ben A; Shivers, Bethany L; Chancey, Valeta C; Winkelstein, Beth A

    2014-10-01

    Whole body vibration has been postulated to contribute to the onset of back pain. However, little is known about the relationship between vibration exposure, the biomechanical response, and the physiological responses of the seated human. The aim of this study was to measure the frequency and corresponding muscle responses of seated male volunteers during whole body vibration exposures along the vertical and anteroposterior directions to define the transmissibility and associated muscle activation responses for relevant whole body vibration exposures. Seated human male volunteers underwent separate whole body vibration exposures in the vertical (Z-direction) and anteroposterior (X-direction) directions using sinusoidal sweeps ranging from 2 to 18 Hz, with a constant amplitude of 0.4 g. For each vibration exposure, the accelerations and displacements of the seat and lumbar and thoracic spines were recorded. In addition, muscle activity in the lumbar and thoracic spines was recorded using electromyography (EMG) and surface electrodes in the lumbar and thoracic region. Transmissibility was determined, and peak transmissibility, displacement, and muscle activity were compared in each of the lumbar and thoracic regions. The peak transmissibility for vertical vibrations occurred at 4 Hz for both the lumbar (1.55 ± 0.34) and thoracic (1.49 ± 0.21) regions. For X-directed seat vibrations, the transmissibility ratio in both spinal regions was highest at 2 Hz but never exceeded a value of 1. The peak muscle response in both spinal regions occurred at frequencies corresponding to the peak transmissibility, regardless of the direction of imposed seat vibration: 4 Hz for the Z-direction and 2-3 Hz for the X-direction. In both vibration directions, spinal displacements occurred primarily in the direction of seat vibration, with little off-axis motion. The occurrence of peak muscle responses at frequencies of peak transmissibility suggests that such

  14. Relationship of the vibrational frequency of the uranyl ion with the uranium electronegativity; Relacion de la frecuencia vibracional del ion uranilo con la electronegatividad del uranio

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez S, A.; Martinez Q, E

    1990-07-15

    It has been demonstrated that the vibrational asymmetric frequency of the uranyl ion, it experiences a consistent spectrochemical displacement with the variations of electronegativity of the uranium in their complexes. The values of the electronegativity of the uranium they were dear by means of calculations that it involves measures of those lengths of the connection uranium-oxygen, obtained by vibrational spectroscopy, effective nuclear charges and the Allred and Rochow equation. The results show the evidence of a natural order that relates to the vibrational frequency with the electronegativity of the uranium atom; settling down that if the electronegativity is graph against it bond length to the oxygen or to it frequency value, a simple relationship is obtained as a form to obtain clear responses in absence of complementary information. (Author)

  15. Time and Frequency Domain Optimization with Shift, Convolution and Smoothness in Factor Analysis Type Decompositions

    DEFF Research Database (Denmark)

    Madsen, Kristoffer Hougaard; Hansen, Lars Kai; Mørup, Morten

    2009-01-01

    We propose the Time Frequency Gradient Method (TFGM) which forms a framework for optimization of models that are constrained in the time domain while having efficient representations in the frequency domain. Since the constraints in the time domain in general are not transparent in a frequency......-negative Matrix Factorization, Convolutive Sparse Coding as well as Smooth and Sparse Matrix Factorization. Matlab implementation of the proposed algorithms are available for download at www.erpwavelab.org....

  16. O modelo AM1 na previsão de frequências vibracionais The vibration frequencies predicted by the AM1 model

    Directory of Open Access Journals (Sweden)

    João Carlos Silva Ramos

    1999-09-01

    Full Text Available We analyse vibrational frequencies of 168 compounds with the AM1 model concerning its experimentally observed gaseous frequencies. Stretching of CH, NH, OH and CO bonds, its related bending frequencies, and the CC frame movements are the studied vibrations. The results show problems with the AM1 vibrational splittings. Often symmetric stretching frequencies, like in CH3, CH2 and NH3, appear switched with the corresponding antisymmetrical ones. Among the studied vibrations many stretchings are overestimated, while bendings oscillate around experimental values. Fluorine stretchings, NN, OO, CH, double and triples CC bonds and cyclic hydrocarbon breathing modes are always overestimated while torsions, umbrella modes and OH/SH stretching are, in average, underestimated. Graphical analysis show that compounds with the lowest molecular masses are the ones with the largest difference to the experimental values. From our results it is not possible to fit confortably the calculated frequencies by a simple linear relationship of the type, n(obs=a*n(AM1. Better aggreement is obtained when different curves are adjusted for the stretching and bending modes, and when a complete linear function is used. Among our studies the best obtained statistical results are for CH, NH and OH. The conclusions obtained in this work will improve the AM1 calculated frequencies leading to accurate results for these properties.

  17. Case study of system effects on high frequency vibration isolation in aircraft structure

    Science.gov (United States)

    Simmons, William E.; Marshall, Steven E.

    In an attempt to improve isolator selection criteria for use in commercial airplanes, a modeling technique was developed. This technique was used to map the vibrational energy transfer from a resiliently mounted electric motor-driven hydraulic pump (or ACMP) to its foundation, a keel beam in the main wheelwell of a large airplane. The system level parameters that strongly influence mount transmissibility were investigated. Using common elastomeric material properties model, predictions were found to compare favorably to measured transmissibility data. The present study discusses the modeling technique and test data comparison, Potential improvements in isolator performance are evaluated. Isolator properties are then identified whch, when combined with transmissibility data, would enhance the isolator selection process.

  18. Sum Frequency Generation Vibrational Spectroscopy of Adsorbed Amino Acids, Peptides and Proteins of Hydrophilic and Hydrophobic Solid-Water Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Holinga IV, George Joseph [Univ. of California, Berkeley, CA (United States)

    2010-09-01

    Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the interfacial properties of several amino acids, peptides, and proteins adsorbed at the hydrophilic polystyrene solid-liquid and the hydrophobic silica solid-liquid interfaces. The influence of experimental geometry on the sensitivity and resolution of the SFG vibrational spectroscopy technique was investigated both theoretically and experimentally. SFG was implemented to investigate the adsorption and organization of eight individual amino acids at model hydrophilic and hydrophobic surfaces under physiological conditions. Biointerface studies were conducted using a combination of SFG and quartz crystal microbalance (QCM) comparing the interfacial structure and concentration of two amino acids and their corresponding homopeptides at two model liquid-solid interfaces as a function of their concentration in aqueous solutions. The influence of temperature, concentration, equilibration time, and electrical bias on the extent of adsorption and interfacial structure of biomolecules were explored at the liquid-solid interface via QCM and SFG. QCM was utilized to quantify the biological activity of heparin functionalized surfaces. A novel optical parametric amplifier was developed and utilized in SFG experiments to investigate the secondary structure of an adsorbed model peptide at the solid-liquid interface.

  19. The effect of the training with the different combinations of frequency and peak-to-peak vibration displacement of whole-body vibration on the strength of knee flexors and extensors

    Directory of Open Access Journals (Sweden)

    M Stania

    2017-01-01

    Full Text Available Whole-body vibration training has become a popular method used in sports and physiotherapy. The study aimed to evaluate the effect of different vibration frequency and peak-to-peak displacement combinations on men knee flexors and extensors strength in isokinetic conditions. The sample consisted of 49 male subjects randomly allocated to seven comparative groups, six of which exercised on a vibration platform with parameters set individually for the groups. The experimental groups were exposed to vibrations 3 times a week for 4 weeks. The pre- and post- isokinetic strength tests, with the angular velocities of 240°/s and 30°/s, were recorded prior to and 2 days after the training. After 4 weeks of whole-body vibration training, a significant increase was noted regarding the mean values of peak torque, average peak torque and total work for knee flexors at high angular velocity in Groups I (60 Hz/ 4 mm and V (40 Hz/ 2 mm (p<0.05. The mean percentage values of post-training changes to study parameters suggest that the training had the most beneficial effect in Groups I (60 Hz/4 mm and IV (60 Hz/2 mm (p<0.05. Whole-body vibrations during static exercise beneficially affected knee flexor strength profile in young men at high angular velocity. The combinations of 60 Hz/4 mm seem to have the most advantageous effects on muscle strength parameters.

  20. Topology Optimization of Distributed Mass Dampers for Low-frequency Vibration Suppression

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard; Lazarov, Boyan Stefanov

    2007-01-01

    In this paper the method of topology optimization is used to find optimized parameter distributions for a multiple mass damper system with the purpose of minimizing the low-frequency steady-state response of a carrier structure. An effective density model that describes the steady-state effect...... of the dampers is derived based on a continuous approximation of the damper distribution. The dampers are optimized with respect to the point-wise distribution of mass ratio, natural frequency, and damping ratio....

  1. A Practical Method to Increase the Frequency Readability for Vibration Signals

    Directory of Open Access Journals (Sweden)

    Jean Loius Ntakpe

    2016-10-01

    Full Text Available Damage detection and nondestructive evaluation of mechanical and civil engineering structures are nowadays very important to assess the integrity and ensure the reliability of structures. Thus, frequency evaluation becomes a crucial issue, since this modal parameter is mainly used in structural integrity assessment. The herein presented study highligts the possibility of increasing the frequency readability by involving a simple and cost-effective method.

  2. A Novel Tunable Multi-Frequency Hybrid Vibration Energy Harvester Using Piezoelectric and Electromagnetic Conversion Mechanisms

    Directory of Open Access Journals (Sweden)

    Zhenlong Xu

    2016-01-01

    Full Text Available This paper presents a novel tunable multi-frequency hybrid energy harvester (HEH. It consists of a piezoelectric energy harvester (PEH and an electromagnetic energy harvester (EMEH, which are coupled with magnetic interaction. An electromechanical coupling model was developed and numerically simulated. The effects of magnetic force, mass ratio, stiffness ratio, and mechanical damping ratios on the output power were investigated. A prototype was fabricated and characterized by experiments. The measured first peak power increases by 16.7% and 833.3% compared with that of the multi-frequency EMEH and the multi-frequency PEH, respectively. It is 2.36 times more than the combined output power of the linear PEH and linear EMEH at 22.6 Hz. The half-power bandwidth for the first peak power is also broadened. Numerical results agree well with the experimental data. It is indicated that magnetic interaction can tune the resonant frequencies. Both magnetic coupling configuration and hybrid conversion mechanism contribute to enhancing the output power and widening the operation bandwidth. The magnitude and direction of magnetic force have significant effects on the performance of the HEH. This proposed HEH is an effective approach to improve the generating performance of the micro-scale energy harvesting devices in low-frequency range.

  3. Impact of acoustic airflow on intrasinus drug deposition: New insights into the vibrating mode and the optimal acoustic frequency to enhance the delivery of nebulized antibiotic.

    Science.gov (United States)

    Leclerc, Lara; Merhie, Amira El; Navarro, Laurent; Prévôt, Nathalie; Durand, Marc; Pourchez, Jérémie

    2015-10-15

    We investigated the impact of vibrating acoustic airflow, the high frequency (f≥100 Hz) and the low frequency (f≤45 Hz) sound waves, on the enhancement of intrasinus drug deposition. (81m)Kr-gas ventilation study was performed in a plastinated human cast with and without the addition of vibrating acoustic airflow. Similarly, intrasinus drug deposition in a nasal replica using gentamicin as a marker was studied with and without the superposition of different modes of acoustic airflow. Ventilation experiments demonstrate that no sinus ventilation was observed without acoustic airflow although sinus ventilation occurred whatever the modes of acoustic airflow applied. Intrasinus drug deposition experiments showed that the high frequency acoustic airflow led to 4-fold increase in gentamicin deposition into the left maxillary sinus and to 2-fold deposition increase into the right maxillary sinus. Besides, the low frequency acoustic airflow demonstrated a significant increase of 4-fold and 2-fold in the right and left maxillary sinuses, respectively. We demonstrated the benefit of different modes of vibrating acoustic airflow for maxillary sinus ventilation and intrasinus drug deposition. The degree of gentamicin deposition varies as a function of frequency of the vibrating acoustic airflow and the geometry of the ostia. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Spatial hearing in Cope’s gray treefrog: II. Frequency-dependent directionality in the amplitude and phase of tympanum vibrations

    Science.gov (United States)

    Lee, Norman; Schrode, Katrina M.; Johns, Anastasia R.; Christensen-Dalsgaard, Jakob; Bee, Mark A.

    2014-01-01

    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. PMID:24504183

  5. Investigation of polyvinylidene fluoride (PVDF) films in identifying high-frequency vibration modes of flexible plates.

    Science.gov (United States)

    Chuang, Kuo-Chih; Liou, Hong-Cin; Ma, Chien-Ching

    2014-06-01

    Compared with piezoelectric ceramics such as lead zirconate titanate (PZT) ceramics, the low density and high compliance of the PVDF films make them a more suitable choice in modal testing, especially for detecting high-frequency modes in flexible or inflatable structures. In this work, dynamic sensing performances of PVDF films for flexible structures in modal testing are examined, with considerations including the repeatability of the impact source, the accuracy of the sensing responses, and the influences of the nodal lines on the frequency spectra of the transient responses. Two flexible plates with different boundary conditions and thickness are considered. Experimental results, compared with FEM computations or theoretical predictions, demonstrate the excellent dynamic sensing performance of the PVDF film in modal testing applications, especially for identification of high-frequency modes on flexible structures.

  6. Using strong nonlinearity and high-frequency vibrations to control effective mechanical stiffness

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    2008-01-01

    High-frequency excitation (HFE) can be used to change the effective stiffness of an elastic structure, and related quanti-ties such as resonance frequencies, wave speed, buckling loads, and equilibrium states. There are basically two ways to do this: By using parametrical HFE (with or without non...... the method of direct separation of motions with results of a modified multiple scales ap-proach, valid also for strong nonlinearity, the stiffening ef-fect is predicted for a generic 1-dof system, and results are tested against numerical simulation and ((it is planned)) laboratory experiments....

  7. Frequency Comb Driven Raman Transitions in the THz Range: High Precision Isotope Shift Measurements in Ca+

    DEFF Research Database (Denmark)

    Meyer, Steffen

    2017-01-01

    to picoseconds in the previous experiments. For the broad spectrum, the additional effect of group delay dispersion (GDD) has to be taken into account, since the Raman process relies on the coherent interaction of all frequency components of the spectrum, with GDD influencing the relative phase which leads......This thesis presents for the first time the experimental implementation of coherent Raman oscillations with a femtosecond frequency comb for transition frequencies in the THz range. The technique has been successfully demonstrated before to drive Raman transitions between hyperfine structure states...... to destructive interference. Therefore, GDD is compensated using a prism compressor and it is shown quantitatively that the measured GDD matches the theoretically predicted effect on the total Raman Rabi frequency. For the measurements and compensation of GDD, the techniques of interferometric autocorrelation...

  8. Linear- and nonlinear-electromyographic analysis of supracutaneous vibration stimuli of the forearm using diverse frequencies and considering skin physiological properties.

    Science.gov (United States)

    Ko, Chang-Yong; Chang, Yunhee; Kim, Sol-Bi; Kim, Shinki; Kim, Gyoosuk; Ryu, Jeicheong; Mun, Musung

    2014-01-01

    Numerous studies have reported the efficacy of vibration in sensory feedback or substitution devices for users of myoelectric hand prostheses. Although most myoelectric hand prostheses are presently manipulated by a surface electromyogram (sEMG), only a few studies have been conducted on the effect of vibration on an sEMG. This study aimed to determine whether vibration stimulation affects the linear and nonlinear properties of surface electromyography (sEMG) considering the skin properties. The vibration stimuli, with frequencies ranging from 37 to 258 Hz, were applied to the proximal part of the arms of the eight female and seven male subjects. The skinfold thickness, hardness, and vibration threshold at the stimuli loci were measured. The root mean square (rms) and fractal dimension (DF) of the sEMG were measured at a distance of 1 cm in the upward direction from the stimuli loci. Above 223 Hz there were no differences between the rms of the genders in between the vibration stimuli (p > 0.05). Moreover, no differences were observed between the DF of the genders for any frequency (p > 0.05). Above 149 Hz, there were correlations between the rms and the skin hardness in the females. Otherwise, no correlations were observed between the rms and DF and the skin properties in both genders for most of the frequencies (all p > 0.05). These results suggest that vibration stimuli affect the linear properties of the sEMG, but not the nonlinear properties.

  9. Analysis of the dominant vibration frequencies of rail bridges for structure-borne noise using a power flow method

    Science.gov (United States)

    Li, Q.; Wu, D. J.

    2013-09-01

    The use of concrete bridges in urban rail transit systems has raised many concerns regarding low-frequency (20-200 Hz) structure-borne noise due to the vibration of bridges when subjected to moving trains. Understanding the mechanism that determines the dominant frequencies of bridge vibrations is essential for both vibration and noise reduction. This paper presents a general procedure based on the force method to obtain the power flows within a coupled vehicle-track-bridge system, the point mobility of the system and the dynamic interaction forces connecting various components. The general coupling system consists of multi-rigid-bodies for the vehicles, infinite Euler beams representing the rails, two-dimensional or three-dimensional elements of the concrete bridges, and spring-dashpot pairs to model the wheel-rail contacts, the vehicle suspensions, the rail pads and the bridge bearings. The dynamic interaction of the coupled system is solved in the frequency domain by assuming the combined wheel-rail roughness moves forward relative to the stationary vehicles. The proposed procedure is first applied to a rail on discrete supports and then to a real urban rail transit U-shaped concrete bridge. The computed results show that the wheel-rail contact forces, the power flows to the rail/bridge subsystem and the accelerations of the bridge are primarily dominated by the contents around the natural frequency of a single wheel adhered to the elastically supported rail. If the ath node of the mth spring-dashpot pair and the bth node of the nth spring-dashpot pair are connected to the same rigid body, then δmnab(ω) can be expressed as δmnab(ω)=-{(}/{Mlω}, where Ml is the mass of the lth rigid body. If the ath node of the mth spring-dashpot pair and the bth node of the nth spring-dashpot pair are connected to the same infinite rail, δmnab(ω) can be expressed as [8] δmnab(ω)=-j{((e-je)}/{4EIk}, where xm and xn are the x-coordinates of the mth and nth spring

  10. Vibration isolation performance of an ultra-low frequency folded pendulum resonator

    Science.gov (United States)

    Liu, Jiangfeng; Ju, Li; Blair, David G.

    1997-02-01

    We present an analysis of the transfer function of a very low frequency folded pendulum resonator. It is shown that performance depends critically on centre of percussion tuning of the pendulum arms. Experimental measurements of the transfer function are shown to agree well with theory. The isolator achieves 90 dB isolation at 7 Hz.

  11. Design and fabrication of a PZT cantilever for low frequency vibration energy harvesting.

    Science.gov (United States)

    Kim, Moonkeun; Hwang, Beomseok; Min, Nam Ki; Jeong, Jaehwa; Kwon, Kwang-Ho; Park, Kang-Bak

    2011-07-01

    In this study, a PZT cantilever with a Si proof mass is designed and fabricated for a low frequency energy harvesting application. A mathematical model of a multi-layer composite beam was derived and applied in a parametric analysis of the piezoelectric cantilever. Finally, the dimensions of the cantilever were determined for the resonant frequency of the cantilever. Our cantilever design was based on MATLAB and ANSYS simulations. For this simulation, the proof mass volumes were varied from 0 to 0.5 mm3 and resonant frequencies were calculated from 833.5 Hz to 125.5 Hz, respectively. Based on simulation, we fabricated a device with beam dimensions of about 4.10 mm x 0.48 mm x 0.012 mm, and an integrated Si proof mass with dimensions of about 0.481 mm x 0.48 mm x 0.45 mm. The resonant frequency, maximum peak voltage, and highest average power of the cantilever device were 224.8 Hz, 4.8 mV, and 2.24 nW, respectively.

  12. Vibrational power flow and structural intensity: Measurements and limitations at low frequencies

    DEFF Research Database (Denmark)

    Ohlrich, Mogens

    1991-01-01

    The cross-spectral methods and their sensitivity to phase errors are investigated for the two and four-accelerometer arrays. From experiments on a beam structure it is attempted to verify the influence of phase errors and to determine the usable frequency ranges of the two methods. Measurements a...

  13. Using strong nonlinearity and high-frequency vibrations to control effective properties of discrete elastic waveguides

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Thomsen, Jon Juel; Snaeland, Sveinn Orri

    2008-01-01

    The aim of this article is to investigate how highfrequency (HF) excitation, combined with strong nonlinear elastic material behavior, influences the effective material or structural properties for low-frequency excitation and wave propagation. The HF effects are demonstrated on discrete linear...

  14. The larmor frequency shift in magnetically heterogeneous media depends on their mesoscopic structure.

    Science.gov (United States)

    Ruh, Alexander; Scherer, Harald; Kiselev, Valerij G

    2017-05-19

    Recent studies have addressed the determination of the NMR precession frequency in biological tissues containing magnetic susceptibility differences between cell types. The purpose of this study is to investigate the dependence of the precession frequency on medium microstructure using a simple physical model. This dependence is governed by diffusion of NMR-visible molecules in magnetically heterogeneous microenvironments. In the limit of fast diffusion, the precession frequency is determined by the average susceptibility-induced magnetic field, whereas in the limit of slow diffusion it is determined by the average local phase factor of precessing spins. The main method used is Monte Carlo simulation of isotropic suspensions of impermeable magnetized spheres. In addition, NMR spectroscopy was performed in aqueous suspensions of polystyrene microbeads. The precession frequency depends on the structural organization of magnetized objects in the medium. Monte Carlo simulations demonstrated a nonmonotonic transition between the regimes of fast and slow diffusion. NMR experiments confirmed the transition, but were unable to confirm its precise form. Results for a given pattern of structural organization obey a scaling law. The NMR precession frequency exhibits a complex dependence on medium structure. Our results suggest that the commonly assumed limit of fast water diffusion holds for biological tissues with small cells. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  15. Density functional theory for prediction of far-infrared vibrational frequencies: molecular crystals of astrophysical interest

    Science.gov (United States)

    Ennis, C.; Auchettl, R.; Appadoo, D. R. T.; Robertson, E. G.

    2017-11-01

    Solid-state density functional theory code has been implemented for the structure optimization of crystalline methanol, acetaldehyde and acetic acid and for the calculation of infrared frequencies. The results are compared to thin film spectra obtained from low-temperature experiments performed at the Australian Synchrotron. Harmonic frequency calculations of the internal modes calculated at the B3LYP-D3/m-6-311G(d) level shows higher deviation from infrared experiment than more advanced theory applied to the gas phase. Importantly for the solid-state, the simulation of low-frequency molecular lattice modes closely resembles the observed far-infrared features after application of a 0.92 scaling factor. This allowed experimental peaks to be assigned to specific translation and libration modes, including acetaldehyde and acetic acid lattice features for the first time. These frequency calculations have been performed without the need for supercomputing resources that are required for large molecular clusters using comparable levels of theory. This new theoretical approach will find use for the rapid characterization of intermolecular interactions and bonding in crystals, and the assignment of far-infrared spectra for crystalline samples such as pharmaceuticals and molecular ices. One interesting application may be for the detection of species of prebiotic interest on the surfaces of Kuiper-Belt and Trans-Neptunian Objects. At such locations, the three small organic molecules studied here could reside in their crystalline phase. The far-infrared spectra for their low-temperature solid phases are collected under planetary conditions, allowing us to compile and assign their most intense spectral features to assist future far-infrared surveys of icy Solar system surfaces.

  16. Random vibration of linear and nonlinear structural systems with singular matrices: A frequency domain approach

    Science.gov (United States)

    Kougioumtzoglou, I. A.; Fragkoulis, V. C.; Pantelous, A. A.; Pirrotta, A.

    2017-09-01

    A frequency domain methodology is developed for stochastic response determination of multi-degree-of-freedom (MDOF) linear and nonlinear structural systems with singular matrices. This system modeling can arise when a greater than the minimum number of coordinates/DOFs is utilized, and can be advantageous, for instance, in cases of complex multibody systems where the explicit formulation of the equations of motion can be a nontrivial task. In such cases, the introduction of additional/redundant DOFs can facilitate the formulation of the equations of motion in a less labor intensive manner. Specifically, relying on the generalized matrix inverse theory, a Moore-Penrose (M-P) based frequency response function (FRF) is determined for a linear structural system with singular matrices. Next, relying on the M-P FRF a spectral input-output (excitation-response) relationship is derived in the frequency domain for determining the linear system response power spectrum. Further, the above methodology is extended via statistical linearization to account for nonlinear systems. This leads to an iterative determination of the system response mean vector and covariance matrix. Furthermore, to account for singular matrices, the generalization of a widely utilized formula that facilitates the application of statistical linearization is proved as well. The formula relates to the expectation of the derivatives of the system nonlinear function and is based on a Gaussian response assumption. Several linear and nonlinear MDOF structural systems with singular matrices are considered as numerical examples for demonstrating the validity and applicability of the developed frequency domain methodology.

  17. Model Catalysis of Ammonia Synthesis ad Iron-Water Interfaces - ASum Frequency Generation Vibrational Spectroscopic Study of Solid-GasInterfaces and Anion Photoelectron Spectroscopic Study of Selected Anionclusters

    Energy Technology Data Exchange (ETDEWEB)

    Ferguson, Michael James [Univ. of California, Berkeley, CA (United States)

    2005-01-01

    The ammonia synthesis reaction has been studied using single crystal model catalysis combined with sum frequency generation (SFG) vibrational spectroscopy. The adsorption of gases N2, H2, O2 and NH3 that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by sum frequency generation vibrational spectroscopy using an integrated Ultra-High Vacuum (UHV)/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH2 (~3325 cm-1) and NH (~3235 cm-1) under high pressure of ammonia or equilibrium concentrations of reactants and products on Fe(111) surfaces. Special attention was paid to understand how potassium promotion of the iron catalyst affects the intermediates of ammonia synthesis. An Fe(111) surface promoted with 0.2 monolayers of potassium red shifts the vibrational frequencies of the reactive surface intermediates, NH and NH2, providing evidence for weakened the nitrogen-hydrogen bonds relative to clean Fe(111). Spectral features of these surface intermediates persisted to higher temperatures for promoted iron surfaces than for clean Fe(111) surfaces implying that nitrogen-iron bonds are stronger for the promoted surface. The ratio of the NH to NH2 signal changed for promoted surfaces in the presence of equilibrium concentrations of reactants and products. The order of adding oxygen and potassium to promoted surfaces does not alter the spectra indicating that ammonia induces surface reconstruction of the catalyst to produce the same surface morphology. When oxygen is co-adsorbed with nitrogen, hydrogen, ammonia or potassium on Fe(111), a relative phase shift of the spectra occurs as compared to the presence of adsorbates on clean iron surfaces. Water adsorption on iron was also probed using SFG vibrational spectroscopy. For both H2O and D2O, the only spectral feature was in the range of

  18. MRI thermometry in phantoms by use of the proton resonance frequency shift method: application to interstitial laser thermotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Olsrud, Johan; Wirestam, Ronnie; Brockstedt, Sara; Persson, Bertil R.R. [Department of Radiation Physics, Lund University Hospital, SE-221 85 Lund (Sweden); Nilsson, Annika M.K. [Department of Physics, Lund Institute of Technology, SE-221 00 Lund (Sweden); Tranberg, Karl-Goeran [Department of Surgery, Lund University Hospital, SE-221 85 Lund (Sweden); Staahlberg, Freddy [Department of Radiation Physics, Lund University Hospital, SE-221 85 Lund (Sweden); Department of Diagnostic Radiology, Lund University Hospital, SE-221 85 Lund (Sweden)

    1998-09-01

    In this work the temperature dependence of the proton resonance frequency was assessed in agarose gel with a high melting temperature (95 deg. C) and in porcine liver in vitro at temperatures relevant to thermotherapy (25-80 deg. C). Furthermore, an optically tissue-like agarose gel phantom was developed and evaluated for use in MRI. The phantom was used to visualize temperature distributions from a diffusing laser fibre by means of the proton resonance frequency shift method. An approximately linear relationship (0.0085 ppm deg. C{sup -1}) between proton resonance frequency shift and temperature change was found for agarose gel, whereas deviations from a linear relationship were observed for porcine liver. The optically tissue-like agarose gel allowed reliable MRI temperature monitoring, and the MR relaxation times (T{sub 1} and T{sub 2}) and the optical properties were found to be independently alterable. Temperature distributions around a diffusing laser fibre, during irradiation and subsequent cooling, were assessed with high spatial resolution (voxel size = 4.3 mm{sup 3}) and with random uncertainties ranging from 0.3 deg. C to 1.4 deg. C (1 SD) with a 40 s scan time. (author)

  19. Nonlinear frequency shift on an electron plasma wave: hysteresis, nonlocality and multidimensional effects in an inhomogeneous plasma

    Science.gov (United States)

    Benisti, Didier

    2017-10-01

    We provide a general derivation of the nonlinear frequency shift, δω , for a sinusoidal electron plasma wave (EPW) that varies slowly enough for neo-adiabatic theory to apply. We first consider the situation when the EPW monotonously grows and then monotonously decays in a homogeneous plasma. In this situation, we show a hysteresis in the wave frequency, which does not converge back to its linear value as the wave decays to small amplitudes. We then address the derivation of δω for an EPW that keeps growing in a one-dimensional (1-D) inhomogeneous plasma. We show that, usually, the frequency shift does not only depend on the local EPW amplitude and wavenumber. It also depends on the whole history of the density variations, as experienced by the wave. In a multidimensional inhomogeneous plasma, the values assumed by δω are usually different from those derived in 1-D because, due to the transverse electron motion, one must account for the hysteresis in δω in addition to plasma inhomogeneity. Hence, unless the EPW keeps growing in a homogeneous 1-D plasma, one cannot derive δω a priori as a function of the local wave amplitude and wavenumber. Due to the nonlocality in the action distribution function, δω depends on the whole history of the variations of the EPW amplitude and plasma density.

  20. Doppler-shift compensation behavior in horseshoe bats revisited: auditory feedback controls both a decrease and an increase in call frequency.

    Science.gov (United States)

    Metzner, Walter; Zhang, Shuyi; Smotherman, Michael

    2002-06-01

    Among mammals, echolocation in bats illustrates the vital role of proper audio-vocal feedback control particularly well. Bats adjust the temporal, spectral and intensity parameters of their echolocation calls depending on the characteristics of the returning echo signal. The mechanism of audio-vocal integration in both mammals and birds is, however, still largely unknown. Here, we present behavioral evidence suggesting a novel audio-vocal control mechanism in echolocating horseshoe bats (Rhinolophus ferrumequinum). These bats compensate for even subtle frequency shifts in the echo caused by flight-induced Doppler effects by adjusting the frequency of their echolocation calls. Under natural conditions, when approaching background targets, the bats usually encounter only positive Doppler shifts. Hence, we commonly believed that, during this Doppler-shift compensation behavior, horseshoe bats use auditory feedback to compensate only for these increases in echo frequency (=positive shifts) by actively lowering their call frequency below the resting frequency (the call frequency emitted when not flying and not experiencing Doppler shifts). Re-investigation of the Doppler-shift compensation behavior, however, shows that decreasing echo frequencies (=negative shifts) are involved as well: auditory feedback from frequencies below the resting frequency, when presented at similar suprathreshold intensity levels as higher echo frequencies, cause the bat's call frequency to increase above the resting frequency. However, compensation for negative shifts is less complete than for positive shifts (22% versus 95%), probably because of biomechanical restrictions in the larynx of bats. Therefore, Doppler-shift compensation behavior involves a quite different neural substrate and audio-vocal control mechanism from those previously assumed. The behavioral results are no longer consistent with solely inhibitory feedback originating from frequencies above the resting frequency. Instead

  1. Effect of Two-Photon Stark Shift on the Multi-Frequency Raman Spectra

    Directory of Open Access Journals (Sweden)

    Hao Yan

    2014-09-01

    Full Text Available High order Raman generation has received considerable attention as a possible method for generating ultrashort pulses. A large number of Raman orders can be generated when the Raman-active medium is pumped by two laser pulses that have a frequency separation equal to the Raman transition frequency. High order Raman generation has been studied in the different temporal regimes, namely: adiabatic, where the pump pulses are much longer than the coherence time of the transition; transient, where the pulse duration is comparable to the coherence time; and impulsive, where the bandwidth of the ultrashort pulse is wider than the transition frequency. To date, almost all of the work has been concerned with generating as broad a spectrum as possible, but we are interested in studying the spectra of the individual orders when pumped in the transient regime. We concentrate on looking at extra peaks that are generated when the Raman medium is pumped with linearly chirped pulses. The extra peaks are generated on the low frequency side of the Raman orders. We discuss how linear Raman scattering from two-photon dressed states can lead to the generation of these extra peaks.

  2. Center of Mass Estimation for a Spinning Spacecraft Using Doppler Shift of the GPS Carrier Frequency

    Science.gov (United States)

    Sedlak, Joseph E.

    2016-01-01

    A sequential filter is presented for estimating the center of mass (CM) of a spinning spacecraft using Doppler shift data from a set of onboard Global Positioning System (GPS) receivers. The advantage of the proposed method is that it is passive and can be run continuously in the background without using commanded thruster firings to excite spacecraft dynamical motion for observability. The NASA Magnetospheric Multiscale (MMS) mission is used as a test case for the CM estimator. The four MMS spacecraft carry star cameras for accurate attitude and spin rate estimation. The angle between the spacecraft nominal spin axis (for MMS this is the geometric body Z-axis) and the major principal axis of inertia is called the coning angle. The transverse components of the estimated rate provide a direct measure of the coning angle. The coning angle has been seen to shift slightly after every orbit and attitude maneuver. This change is attributed to a small asymmetry in the fuel distribution that changes with each burn. This paper shows a correlation between the apparent mass asymmetry deduced from the variations in the coning angle and the CM estimates made using the GPS Doppler data. The consistency between the changes in the coning angle and the CM provides validation of the proposed GPS Doppler method for estimation of the CM on spinning spacecraft.

  3. Atomization off thin water films generated by high-frequency substrate wave vibrations

    Science.gov (United States)

    Collins, David J.; Manor, Ofer; Winkler, Andreas; Schmidt, Hagen; Friend, James R.; Yeo, Leslie Y.

    2012-11-01

    Generating aerosol droplets via the atomization of thin aqueous films with high frequency surface acoustic waves (SAWs) offers several advantages over existing nebulization methods, particularly for pulmonary drug delivery, offering droplet sizes in the 1-5-μm range ideal for effective pulmonary therapy. Nevertheless, the physics underlying SAW atomization is not well understood, especially in the context of thin liquid film formation and spreading and how this affects the aerosol production. Here, we demonstrate that the film geometry, governed primarily by the applied power and frequency of the SAW, indeed plays a crucial role in the atomization process and, in particular, the size of the atomized droplets. In contrast to the continuous spreading of low surface energy liquids atop similar platforms, high surface energy liquids such as water, in the present case, are found to undergo transient spreading due to the SAW to form a quasisteady film whose height is determined by self-selection of the energy minimum state associated with the acoustic resonance in the film and whose length arises from a competition between acoustic streaming and capillary effects. This is elucidated from a fundamental model for the thin film spreading behavior under SAW excitation, from which we show good agreement between the experimentally measured and theoretically predicted droplet dimension, both of which consistently indicate a linear relationship between the droplet diameter and the mechanical power coupled into the liquid by the SAW (the latter captured by an acoustic Weber number to the two thirds power, and the reciprocal of the SAW frequency).

  4. Effect of Shift Work on the Frequency of Depression in Nursing Staff of Yazd University of Medical Sciences

    Directory of Open Access Journals (Sweden)

    Gholam Hossein Halvani

    2012-12-01

    Full Text Available Introduction: Depression as a disorder is relatively common in all societies; several factors are involved in depression development, that shift work is one of these factors. This study compared the frequency of depression in different shifts of nurses in hospitals of Yazd University of medical sciences. Materials & Methods: This study is a descriptive analytical study. Based on statistical methods, 150 nurses participated in this study. The research tool was a questionnaire that included 15 personal questions and 21 questions related to Beck test. The results were analysed by SPSS software. Results: 13.3% of all subjects were males and 86.7% were females. Results showed that, there is no significant relationship between gender, education, type of job, employment status and satisfaction levels of income with depression. Marital status (P-Value = 0.009 and F = 6.93, shift work (day working and shift work (P-Value = 0.032 and F = 1.11, job satisfaction (P-Value = 0.000 and F = 7.641 and the satisfaction of the employer (P-Value = 0.001 and F = 5.414 were significantly associated with depression. 3.49% of the nurses were in normal status, 7.26% had mild depression, 3.9% required consultation with the psychiatrist,% 7.8% suffered from moderate depression, 75.4% from severe depression and 3.1% from very severe depression. Conclusion: It seems that shift work can not cause depression alone, but depression is the result of the interaction of several factors.

  5. Dynamic stiffness of chemically and physically ageing rubber vibration isolators in the audible frequency range. Part 1: constitutive equations

    Science.gov (United States)

    Kari, Leif

    2017-09-01

    The constitutive equations of chemically and physically ageing rubber in the audible frequency range are modelled as a function of ageing temperature, ageing time, actual temperature, time and frequency. The constitutive equations are derived by assuming nearly incompressible material with elastic spherical response and viscoelastic deviatoric response, using Mittag-Leffler relaxation function of fractional derivative type, the main advantage being the minimum material parameters needed to successfully fit experimental data over a broad frequency range. The material is furthermore assumed essentially entropic and thermo-mechanically simple while using a modified William-Landel-Ferry shift function to take into account temperature dependence and physical ageing, with fractional free volume evolution modelled by a nonlinear, fractional differential equation with relaxation time identical to that of the stress response and related to the fractional free volume by Doolittle equation. Physical ageing is a reversible ageing process, including trapping and freeing of polymer chain ends, polymer chain reorganizations and free volume changes. In contrast, chemical ageing is an irreversible process, mainly attributed to oxygen reaction with polymer network either damaging the network by scission or reformation of new polymer links. The chemical ageing is modelled by inner variables that are determined by inner fractional evolution equations. Finally, the model parameters are fitted to measurements results of natural rubber over a broad audible frequency range, and various parameter studies are performed including comparison with results obtained by ordinary, non-fractional ageing evolution differential equations.

  6. Calculated vibrational frequencies for FeMo-co, the active site of nitrogenase, bearing hydrogen atoms and carbon monoxide.

    Science.gov (United States)

    Dance, Ian

    2011-06-28

    The intramolecular hydrogenation paradigm for the reducing actions of the enzyme nitrogenase postulates that the iron-molybdenum cofactor (FeMo-co, Fe(7)MoS(9)N(homocitrate)) as active site contains H atoms bound to Fe and S during the catalytic cycle, and that these H atoms are the reducing agents. The reduction of N(2) and of all other non-physiological substrates is strongly inhibited by carbon monoxide, except for the formation of H(2) from protons. It has been recently reported that vanadium nitrogenase and modified molybdenum nitrogenase reduce CO to hydrocarbons. Therefore many questions now arise about relationships between CO and H on the nitrogenase cofactors. In order to assist the interpretation of kinetic infrared spectral data, vibrational frequencies and modes have been calculated for a variety of possible structures in which FeMo-co bears H atoms, or CO ligands, or both. Fe-H stretching frequencies occur in the same spectral window as the C-O stretching frequencies, with lesser intensity, and both stretches are strongly coupled in some structures. Symmetrical bridging of CO between two Fe atoms of FeMo-co is destabilised by the presence of other ligands on Fe, and the reason for this is evident. Two results for bound formyl, HCO, are reported. These calculations of reference structures allow some interpretation of existing experimental spectra, but, more significantly, they suggest further kinetic infrared experiments to elucidate the chemical mechanism of catalysis by nitrogenase under normal turnover conditions. This journal is © The Royal Society of Chemistry 2011

  7. Amplitude and Frequency Control: Stability of Limit Cycles in Phase-Shift and Twin-T Oscillators

    Directory of Open Access Journals (Sweden)

    J. P. Dada

    2008-01-01

    Full Text Available We show a technique for external direct current (DC control of the amplitudes of limit cycles both in the Phase-shift and Twin-T oscillators. We have found that amplitudes of the oscillator output voltage depend on the DC control voltage. By varying the total impedance of each oscillator oscillatory network, frequencies of oscillations are controlled using potentiometers. The main advantage of the proposed circuits is that both the amplitude and frequency of the waveforms generated can be independently controlled. Analytical, numerical, and experimental methods are used to determine the boundaries of the states of the oscillators. Equilibrium points, stable limit cycles, and divergent states are found. Analytical results are compared with the numerical and experimental solutions, and a good agreement is obtained.

  8. Resonance frequency shifts due to quantized electronic states in atomically thin NEMS

    Science.gov (United States)

    Chen, Changyao; Deshpande, Vikram; Koshino, Mikito; Lee, Sunwoo; Gondarenko, Alexander; MacDonald, Allan; Kim, Philip; Hone, James

    The classic picture of the force exerted on a parallel plate capacitor assumes infinite density of states (DOS), which implies identical electrochemical and electrostatic potential. However, such assumption can breakdown in low-dimensional devices where the DOS is finite or quantized. Here we consider the mechanical resonance shift of a nanoelectromechanical (NEMS) resonator with small DOS, actuated and detected capacitively at fixed electrochemical potential. We found three leading correction terms to the classical picture: the first term leads to the modulation of static force due to the variation in chemical potential, and the second and third terms are related to the static and dynamic changes in spring constants, caused by quantum capacitance. The theory agrees well with recent experimental findings from graphene resonator in quantum Hall regimes, where the chemical potential and quantum capacitance are tuned by magnetic field, while the gate voltage is kept constant.

  9. Phase- and tilt-shift determinations by analysis of spectra sidebands for phase-shift interferometers.

    Science.gov (United States)

    Liu, Qian; Wang, Yang; Ji, Fang; He, Jianguo

    2013-11-01

    A spatial frequency domain method is presented to deal with tilt-shift errors and random phase shift in temporal phase-shift interferometry. The proposed method determines tilt shift and phase shift by analyzing positions and phase variances of sidebands in spatial frequency domain. The method is computationally fast for it is noniterative and needs only one 2D Fourier transform for each spatial carrier interferogram. No initial estimations are required and no ambiguous results are generated with the proposed method. Simulations indicate that the proposed method could detect tilt shift and piston phase shift with high accuracy. Results of experiments conducted in the presence of vibration demonstrate that the proposed method could alleviate fluctuations in the retrieved phase map. The method could be applied to interferometers that are uncalibrated or with an unbalanced piezoelectric transducer, besides interferometers in unsteady conditions.

  10. Stochastic resonance energy harvesting for a rotating shaft subject to random and periodic vibrations: influence of potential function asymmetry and frequency sweep

    Science.gov (United States)

    Kim, Hongjip; Che Tai, Wei; Zhou, Shengxi; Zuo, Lei

    2017-11-01

    Stochastic resonance is referred to as a physical phenomenon that is manifest in nonlinear systems whereby a weak periodic signal can be significantly amplified with the aid of inherent noise or vice versa. In this paper, stochastic resonance is considered to harvest energy from two typical vibrations in rotating shafts: random whirl vibration and periodic stick-slip vibration. Stick-slip vibrations impose a constant offset in centrifugal force and distort the potential function of the harvester, leading to potential function asymmetry. A numerical analysis based on a finite element method was conducted to investigate stochastic resonance with potential function asymmetry. Simulation results revealed that a harvester with symmetric potential function generates seven times higher power than that with asymmetric potential function. Furthermore, a frequency-sweep analysis also showed that stochastic resonance has hysteretic behavior, resulting in frequency difference between up-sweep and down-sweep excitations. An electromagnetic energy harvesting system was constructed to experimentally verify the numerical analysis. In contrast to traditional stochastic resonance harvesters, the proposed harvester uses magnetic force to compensate the offset in the centrifugal force. System identification was performed to obtain the parameters needed in the numerical analysis. With the identified parameters, the numerical simulations showed good agreement with the experiment results with around 10% error, which verified the effect of potential function asymmetry and frequency sweep excitation condition on stochastic resonance. Finally, attributed to compensating the centrifugal force offset, the proposed harvester generated nearly three times more open-circuit output voltage than its traditional counterpart.

  11. Vibration and acoustic frequency spectra for industrial process modeling using selective fusion multi-condition samples and multi-source features

    Science.gov (United States)

    Tang, Jian; Qiao, Junfei; Wu, ZhiWei; Chai, Tianyou; Zhang, Jian; Yu, Wen

    2018-01-01

    Frequency spectral data of mechanical vibration and acoustic signals relate to difficult-to-measure production quality and quantity parameters of complex industrial processes. A selective ensemble (SEN) algorithm can be used to build a soft sensor model of these process parameters by fusing valued information selectively from different perspectives. However, a combination of several optimized ensemble sub-models with SEN cannot guarantee the best prediction model. In this study, we use several techniques to construct mechanical vibration and acoustic frequency spectra of a data-driven industrial process parameter model based on selective fusion multi-condition samples and multi-source features. Multi-layer SEN (MLSEN) strategy is used to simulate the domain expert cognitive process. Genetic algorithm and kernel partial least squares are used to construct the inside-layer SEN sub-model based on each mechanical vibration and acoustic frequency spectral feature subset. Branch-and-bound and adaptive weighted fusion algorithms are integrated to select and combine outputs of the inside-layer SEN sub-models. Then, the outside-layer SEN is constructed. Thus, ;sub-sampling training examples;-based and ;manipulating input features;-based ensemble construction methods are integrated, thereby realizing the selective information fusion process based on multi-condition history samples and multi-source input features. This novel approach is applied to a laboratory-scale ball mill grinding process. A comparison with other methods indicates that the proposed MLSEN approach effectively models mechanical vibration and acoustic signals.

  12. Relativistic down-shift frequency effect on the application of electron cyclotron emission measurements to JT-60U tokamak plasmas. Second harmonics

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Masayasu; Isei, Nobuaki; Ishida, Sinichi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    1995-11-01

    Effect of relativistic frequency down-shift on the determination of the electron temperature profile from electron cyclotron emission(ECE) in JT-60U tokamak plasmas is studied. The radial shift of the electron temperature profile due to the effects is not negligible, compared with the spatial resolution of ECE measurement systems of JT-60U. Therefore it is necessary to correct the effect for precise measurement of the electron temperature profile. Dependencies of the shifted frequency on the electron density, electron temperature and toroidal magnetic field are studied for the uniform electron density and parabolic electron temperature profile in JT-60U. It is revealed to be necessary for the estimation of shift due to the relativistic down-shift frequency to take into account of the optical thickness. (author).

  13. High-frequency phase shift measurement greatly enhances the sensitivity of QCM immunosensors.

    Science.gov (United States)

    March, Carmen; García, José V; Sánchez, Ángel; Arnau, Antonio; Jiménez, Yolanda; García, Pablo; Manclús, Juan J; Montoya, Ángel

    2015-03-15

    In spite of being widely used for in liquid biosensing applications, sensitivity improvement of conventional (5-20MHz) quartz crystal microbalance (QCM) sensors remains an unsolved challenging task. With the help of a new electronic characterization approach based on phase change measurements at a constant fixed frequency, a highly sensitive and versatile high fundamental frequency (HFF) QCM immunosensor has successfully been developed and tested for its use in pesticide (carbaryl and thiabendazole) analysis. The analytical performance of several immunosensors was compared in competitive immunoassays taking carbaryl insecticide as the model analyte. The highest sensitivity was exhibited by the 100MHz HFF-QCM carbaryl immunosensor. When results were compared with those reported for 9MHz QCM, analytical parameters clearly showed an improvement of one order of magnitude for sensitivity (estimated as the I50 value) and two orders of magnitude for the limit of detection (LOD): 30μgl(-1) vs 0.66μgL(-1)I50 value and 11μgL(-1) vs 0.14μgL(-1) LOD, for 9 and 100MHz, respectively. For the fungicide thiabendazole, I50 value was roughly the same as that previously reported for SPR under the same biochemical conditions, whereas LOD improved by a factor of 2. The analytical performance achieved by high frequency QCM immunosensors surpassed those of conventional QCM and SPR, closely approaching the most sensitive ELISAs. The developed 100MHz QCM immunosensor strongly improves sensitivity in biosensing, and therefore can be considered as a very promising new analytical tool for in liquid applications where highly sensitive detection is required. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Method of hybrid multiplexing for fiber-optic Fabry-Perot sensors utilizing frequency-shifted interferometry.

    Science.gov (United States)

    Ou, Yiwen; Zhou, Ciming; Zheng, Angui; Cheng, Chunfu; Fan, Dian; Yin, Jiadi; Tian, Hui; Li, Mengmeng; Lu, Ying

    2014-12-10

    Experimental and theoretical research on hybrid multiplexing for fiber-optic Fabry-Perot (F-P) sensors based on frequency-shifted interferometry is presented. Four F-P sensors multiplexed in a hybrid configuration were experimentally investigated. The location of each multiplexed sensor was retrieved by performing the fast Fourier transform, and the reflection spectrum of each sensor was also obtained in spite of the spectral overlap, which was consistent with the results measured by an optical spectrum analyzer. With theoretical modeling, the maximum sensor number of a two-channel hybrid multiplexing system reaches 26 with crosstalk of less than -50  dB and a maximum frequency-domain signal-to-noise ratio (SNR) of ∼25  dB, when the source power is 2 mW and the sensor separation is optimal, i.e., 40 m. And the sensor number is almost twice that multiplexed by a serial system under the same conditions. An SNR improvement of 3.9 dB can be achieved by using a Hamming window in a noise-free system compared with a Hanning window. In addition, we applied the experimental multiplexing system to a strain sensing test. The cavity lengths and cavity-length shifts of the four F-P sensors were demodulated, which was consistent with the actual situation. It provides a new feasible method to multiplex F-P sensors at large scale.

  15. Macrocycle and substituent vibrational modes of nonplanar nickel (II) octaethyltetraphenylporphyrin from its resonance Raman, near-infrared-excited FT Raman, and FT-IR spectra and deuterium isotope shifts

    Energy Technology Data Exchange (ETDEWEB)

    Stichternath, A.; Schweitzer-Stenner, R.; Dreybrodt, W. (Univ. of Bremen (Germany)); Mak, R.S.W.; Li, X.Y. (Hong Kong Univ. of Science and Technology (Hong Kong)); Sparks, L.D.; Shelnutt, J.A. (Sandia National Lab., Albuquerque, NM (United States) Univ. of New Mexico, Albuquerque (United States)); Medforth, C.J.; Smith, K.M. (Univ. of California, Davis (United States))

    1993-04-15

    We have employed Raman dispersion, FT Raman, and FT-IR spectroscopy to identify a large number of resonance Raman lines of Ni(II) octaethyltetraphenylporphyrin dissolved in CS[sub 2]. The Raman depolarization dispersion technique was used to derive the symmetry of the normal modes giving rise to the observed Raman lines. By combining this information and the already available normal coordinates of Ni(II) tetraphenylporphyrin and Ni(II) octaethylporphyrin, many of the Raman-modes of the macrocycle could be assigned. Some resonance-enhanced Raman lines were found to arise from vibrations of the ethyl and phenyl substituents. They were identified by comparing resonance Raman, FT Raman, and FT infrared spectra of the Ni(II) octaethyltetraphenylporphyrin and its d[sub 20] isotopomer. All Raman lines normally referred to as core-size markers are found to be significantly shifted to lower frequencies with respect to their positions in Ni(II) octaethylporphyrin, in accordance with earlier findings (Shelnutt et al., J. Am. Chem. Soc. 113, 4077, 1991). This suggests that the molecule is in a highly nonplanar conformation. This notion is further corroborated by the strong dispersion of the depolarization ratio observed for nearly all A[sub 1g] and A[sub 2g] modes of the macrocycle. 27 refs., 13 figs., 2 tabs.

  16. Multimodal Broadband Vibrational Sum Frequency Generation (MM-BB-V-SFG) Spectrometer and Microscope.

    Science.gov (United States)

    Lee, Christopher M; Kafle, Kabindra; Huang, Shixin; Kim, Seong H

    2016-01-14

    A broadband sum frequency generation (BB-SFG) spectrometer with multimodal (MM) capabilities was constructed, which could be routinely reconfigured for tabletop experiments in reflection, transmission, and total internal reflection (TIR) geometries, as well as microscopic imaging. The system was constructed using a Ti:sapphire amplifier (800 nm, pulse width = 85 fs, repetition rate = 2 kHz), an optical parameter amplification (OPA) system for production of broadband IR pulses tunable between 1000 and 4000 cm(-1), and two Fabry-Pérot etalons arranged in series for production of narrowband 800 nm pulses. The key feature allowing the MM operation was the nearly collinear alignment of the visible (fixed, 800 nm) and infrared (tunable, 1000-4000 cm(-1)) pulses which were spatially separated. Physical insights discussed in this paper include the comparison of spectral bandwidth produced with 40 and 85 fs pump beams, the improvement of spectral resolution using etalons, the SFG probe volume in bulk analysis, the normalization of SFG signals, the stitching of multiple spectral segments, and the operation in different modes for air/liquid and adsorbate/solid interfaces, bulk samples, as well as spectral imaging combined with principle component analysis (PCA). The SFG spectral features obtained with the MM-BB-SFG system were compared with those obtained with picosecond-scanning-SFG system and high-resolution BB-SFG system (HR-BB-SFG) for dimethyl sulfoxide, α-pinene, and various samples containing cellulose (purified commercial products, Cladophora cell wall, cotton and flax fibers, and onion epidermis cell wall).

  17. Analysis of algorithms for detection of resonance frequencies in vibration measurements on super heater tubes; Analys av algoritmer foer detektering av resonansfrekvenser i vibrationsmaetningar paa oeverhettartuber

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Daniel

    2010-07-01

    Combustion of fuel in thermal power plants emits particles which creates coatings on the super heater tubes. The coatings isolate the tubes and impairs the efficiency of the heat transfer. Cleaning the tubes occurs while the power plant is running but without any knowledge of the actual coating. A change in frequency corresponds to a change in mass of the coatings. This thesis has been focusing in estimating resonance frequencies in vibration measurements made by strain gauges on the tubes. To improve the estimations a target tracking algorithm had been added. The results indicates that it is possible to estimate the resonance frequencies but the algorithms need to be verified on more signals.

  18. Ultrasound computed tomography by frequency-shift low-pass filtering and least mean square adaptive filtering

    Science.gov (United States)

    Wang, Shanshan; Song, Junjie; Peng, Yang; Zhou, Liang; Ding, Mingyue; Yuchi, Ming

    2017-03-01

    In recent years, many research studies have been carried out on ultrasound computed tomography (USCT) for improving the detection and management of breast cancer. This paper investigates a signal pre-processing method based on frequency-shift low-pass filtering (FSLF) and least mean square adaptive filtering (LMSAF) for USCT image quality enhancement (proposed in our previous work). FSLF is designed base on Zoom Fast Fourier Transform algorithm (ZFFT) for processing the ultrasound signals in the frequency domain, while LMSAPF is based on the least mean square (LMS) algorithm in the time domain. Through the combination of the two filters, the ultrasound image is expected to have less noises and artifacts, and higher resolution and contrast. The proposed method was verified with the radio-frequency (RF) data of the nylon threads and the breast phantom captured by the USCT system developed in the Medical Ultrasound Laboratory. Experimental results show that the reconstructed images of nylon threads by the proposed method had narrower main lobe width and lower side lobe level comparing to the delay-and-sum (DAS). The background noises and artifacts could also be efficiently restrained. The reconstructed image of breast phantom by the proposed method had a higher resolution and the contrast ratio (CR) could be enhanced for about 12dB to 18dB at different region of interest (ROI).

  19. Experimental Investigation of the Effect of Radial Gap and Impeller Blade Exit on Flow-Induced Vibration at the Blade-Passing Frequency in a Centrifugal Pump

    Directory of Open Access Journals (Sweden)

    A. Al-Qutub

    2009-01-01

    Full Text Available It has been recognized that the pressure pulsation excited by rotor-stator interaction in large pumps is strongly influenced by the radial gap between impeller and volute diffusers/tongues and the geometry of impeller blade at exit. This fluid-structure interaction phenomenon, as manifested by the pressure pulsation, is the main cause of flow-induced vibrations at the blade-passing frequency. In the present investigation, the effects of the radial gap and flow rate on pressure fluctuations, vibration, and pump performance are investigated experimentally for two different impeller designs. One impeller has a V-shaped cut at the blade's exit, while the second has a straight exit (without the V-cut. The experimental findings showed that the high vibrations at the blade-passing frequency are primarily raised by high pressure pulsation due to improper gap design. The existence of V-cut at blades exit produces lower pressure fluctuations inside the pump while maintaining nearly the same performance. The selection of proper radial gap for a given impeller-volute combination results in an appreciable reduction in vibration levels.

  20. Transferring linear motion of an optical wedge to rotational frequency shift in an orbital angular momentum interferometer

    Science.gov (United States)

    Jia, Qikun; Qiu, Xiaodong; Wu, Ziwen; Zhang, Wuhong; Chen, Lixiang

    2017-08-01

    We build a modified Mach-Zehnder (M-Z) interferometer with an embedded Dove prism in one arm to observe the interference between two conjugate orbital angular momentum (OAM) beams. By inserting and moving an optical wedge vertically in the other arm, we find that its linear motion can induce a rotational frequency shift equivalently, as a consequence of phase transfer from the path difference to the azimuthal difference between two OAM beams. The micron-scale movement of the wedge is driven by a compact motorized translation stage and is manifested by a significant rotation of the interference petal-like patterns. Our scheme offers an accurate method to measure the optical wedge angle with a simple method of digital image processing. This work may also find potential applications in the field of velocity sensing or temperature sensing.

  1. Characterisation of the membrane affinity of an isoniazide peptide conjugate by tensiometry, atomic force microscopy and sum-frequency vibrational spectroscopy, using a phospholipid Langmuir monolayer model.

    Science.gov (United States)

    Hill, Katalin; Pénzes, Csanád Botond; Schnöller, Donát; Horváti, Kata; Bosze, Szilvia; Hudecz, Ferenc; Keszthelyi, Tamás; Kiss, Eva

    2010-10-07

    Tensiometry, sum-frequency vibrational spectroscopy, and atomic force microscopy were employed to assess the cell penetration ability of a peptide conjugate of the antituberculotic agent isoniazide. Isoniazide was conjugated to peptide (91)SEFAYGSFVRTVSLPV(106), a functional T-cell epitope of the immunodominant 16 kDa protein of Mycobacterium tuberculosis. As a simple but versatile model of the cell membrane a phospholipid Langmuir monolayer at the liquid/air interface was used. Changes induced in the structure of the phospholipid monolayer by injection of the peptide conjugate into the subphase were followed by tensiometry and sum-frequency vibrational spectroscopy. The drug penetrated lipid films were transferred to a solid support by the Langmuir-Blodgett technique, and their structures were characterized by atomic force microscopy. Peptide conjugation was found to strongly enhance the cell penetration ability of isoniazide.

  2. Experiments on Suppression of Thermocapillary Oscillations in Sodium Nitrate Floating Half-Zones by High-frequency End-wall Vibrations

    Science.gov (United States)

    Anilkumar, A.; Grugel, R. N.; Bhowmick, J.; Wang, T.

    2004-01-01

    Experiments to suppress thermocapillary oscillations using high-frequency vibrations were carried out in sodium nitrate floating half-zones. Such a half-zone is formed by melting one end of a vertically held sodium nitrate crystal rod in contact with a hot surface at the top. Thermocapillary convection occurs in the melt because of the temperature gradient at the free surface of the melt. In the experiments, when thermocapillary oscillations occurred, the bottom end of the crystal rod was vibrated at a high frequency to generate a streaming flow in a direction opposite to that of the thermocapillary convection. It is observed that, by generating a sufficiently strong streaming flow, the thermocapillary flow can be offset enough such that the associated thermocapillary oscillations can be quenched.

  3. Genetic Adaptation to Climate in White Spruce Involves Small to Moderate Allele Frequency Shifts in Functionally Diverse Genes.

    Science.gov (United States)

    Hornoy, Benjamin; Pavy, Nathalie; Gérardi, Sébastien; Beaulieu, Jean; Bousquet, Jean

    2015-11-11

    Understanding the genetic basis of adaptation to climate is of paramount importance for preserving and managing genetic diversity in plants in a context of climate change. Yet, this objective has been addressed mainly in short-lived model species. Thus, expanding knowledge to nonmodel species with contrasting life histories, such as forest trees, appears necessary. To uncover the genetic basis of adaptation to climate in the widely distributed boreal conifer white spruce (Picea glauca), an environmental association study was conducted using 11,085 single nucleotide polymorphisms representing 7,819 genes, that is, approximately a quarter of the transcriptome.Linear and quadratic regressions controlling for isolation-by-distance, and the Random Forest algorithm, identified several dozen genes putatively under selection, among which 43 showed strongest signals along temperature and precipitation gradients. Most of them were related to temperature. Small to moderate shifts in allele frequencies were observed. Genes involved encompassed a wide variety of functions and processes, some of them being likely important for plant survival under biotic and abiotic environmental stresses according to expression data. Literature mining and sequence comparison also highlighted conserved sequences and functions with angiosperm homologs.Our results are consistent with theoretical predictions that local adaptation involves genes with small frequency shifts when selection is recent and gene flow among populations is high. Accordingly, genetic adaptation to climate in P. glauca appears to be complex, involving many independent and interacting gene functions, biochemical pathways, and processes. From an applied perspective, these results shall lead to specific functional/association studies in conifers and to the development of markers useful for the conservation of genetic resources. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular

  4. Vibrational sum frequency spectroscopy studies at solid/liquid interfaces : Influence of the experimental geometry in the spectral shape and enhancement

    OpenAIRE

    Liljeblad, Jonathan F.D.; Tyrode, Eric

    2012-01-01

    The influence of the experimental geometry, specifically the angles of incidence (AOI) of the exciting beams, on the enhancement of the vibrational sum frequency spectroscopy (VSFS) spectra has been systematically investigated, particularly when approaching total internal reflection (TIR) conditions. Theoretical simulations of the spectral intensity as a function of the AOI and infrared wavelength at three different polarization combinations were critically compared to experimental data obtai...

  5. Classical electricity analysis of the coupling mechanisms between admolecule vibrations and localized surface plasmons in STM for vibration detectability

    Science.gov (United States)

    Inaoka, Takeshi; Uehara, Yoich

    2017-08-01

    The presence of a dynamic dipole moment in the gap between the tip of a scanning tunneling microscope (STM) and a substrate, both of which are made of metal, produces a large dynamic dipole moment via the creation of localized surface plasmons (LSPLs). With regard to the vibration-induced structures that have been experimentally observed in STM light emission spectra, we have incorporated the effect of the phonon vibrations of an admolecule below the STM tip into the local response theory, and we have evaluated the enhancement of the dynamic dipole involving phonon vibrations. Our analysis shows how effectively this vibration becomes coupled with the LSPLs. This was shown using three mechanisms that considered the vibrations of a dipole-active molecule and the vibrations of a charged molecule emitting and receiving tunneling electrons. In each of the mechanisms, phonon vibrations with angular frequency ωp shifted each LSPL resonance by ℏωp or by a multiple of ℏωp . The phonon effect was negligibly small when the position of the dipole-active molecule vibrated with ωp, but it was largest and most detectable when the point charge corresponding to the admolecule at the surface of the tip vibrated with ωp. It was found that a series of LSPL resonances with or without phonon-energy shifts can be characterized by a few dominant orders of multipole excitations, and these orders become higher as the resonance energy increases.

  6. Morphological determinants of signal carrier frequency in katydids (Orthoptera): a comparative analysis using biophysical evidence of wing vibration.

    Science.gov (United States)

    Montealegre-Z, F; Ogden, J; Jonsson, T; Soulsbury, C D

    2017-11-01

    Male katydids produce mating calls by stridulation using specialized structures on the forewings. The right wing (RW) bears a scraper connected to a drum-like cell known as the mirror and a left wing (LW) that overlaps the RW and bears a serrated vein on the ventral side, the stridulatory file. Sound is generated with the scraper sweeping across the file, producing vibrations that are amplified by the mirror. Using this sound generator, katydids exploit a range of song carrier frequencies (CF) unsurpassed by any other insect group, with species singing as low as 600 Hz and others as high as 150 kHz. Sound generator size has been shown to scale negatively with CF, but such observations derive from studies based on few species, without phylogenetic control, and/or using only the RW mirror length. We carried out a phylogenetic comparative analysis involving 94 species of katydids to study the relationship between LW and RW components of the sound generator and the CF of the male's mating call, while taking into account body size and phylogenetic relationships. The results showed that CF negatively scaled with all morphological measures, but was most strongly related to components of the sound generation system (file, LW and RW mirrors). Interestingly, the LW mirror (reduced and nonfunctional) predicted CF more accurately than the RW mirror, and body size is not a reliable CF predictor. Mathematical models were verified on known species for predicting CF in species for which sound is unknown (e.g. fossils or museum specimens). © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

  7. Surface and buried interfacial structures of epoxy resins used as underfills studied by sum frequency generation vibrational spectroscopy.

    Science.gov (United States)

    Vázquez, Anne V; Holden, Brad; Kristalyn, Cornelius; Fuller, Mike; Wilkerson, Brett; Chen, Zhan

    2011-05-01

    Flip chip technology has greatly improved the performance of semiconductor devices, but relies heavily on the performance of epoxy underfill adhesives. Because epoxy underfills are cured in situ in flip chip semiconductor devices, understanding their surface and interfacial structures is critical for understanding their adhesion to various substrates. Here, sum frequency generation (SFG) vibrational spectroscopy was used to study surface and buried interfacial structures of two model epoxy resins used as underfills in flip chip devices, bisphenol A digylcidyl ether (BADGE) and 1,4-butanediol diglycidyl ether (BDDGE). The surface structures of these epoxies were compared before and after cure, and the orientations of their surface functional groups were deduced to understand how surface structural changes during cure may affect adhesion properties. Further, the effect of moisture exposure, a known cause of adhesion failure, on surface structures was studied. It was found that the BADGE surface significantly restructured upon moisture exposure while the BDDGE surface did not, showing that BADGE adhesives may be more prone to moisture-induced delamination. Lastly, although surface structure can give some insight into adhesion, buried interfacial structures more directly correspond to adhesion properties of polymers. SFG was used to study buried interfaces between deuterated polystyrene (d-PS) and the epoxies before and after moisture exposure. It was shown that moisture exposure acted to disorder the buried interfaces, most likely due to swelling. These results correlated with lap shear adhesion testing showing a decrease in adhesion strength after moisture exposure. The presented work showed that surface and interfacial structures can be correlated to adhesive strength and may be helpful in understanding and designing optimized epoxy underfill adhesives.

  8. Nanoscale chemical and mechanical characterization of thin films:sum frequency generation (SFG) vibrational spectroscopy at buriedinterfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kweskin, Sasha Joseph [Univ. of California, Berkeley, CA (United States)

    2006-01-01

    Sum frequency generation (SFG) surface vibrational spectroscopy was used to characterize interfaces pertinent to current surface engineering applications, such as thin film polymers and novel catalysts. An array of advanced surface science techniques like scanning probe microscopy (SPM), x-ray photoelectron spectroscopy (XPS), gas chromatography (GC) and electron microscopy were used to obtain experimental measurements complementary to SFG data elucidating polymer and catalyst surface composition, surface structure, and surface mechanical behavior. Experiments reported in this dissertation concentrate on three fundamental questions: (1) How does the interfacial molecular structure differ from that of the bulk in real world applications? (2) How do differences in chemical environment affect interface composition or conformation? (3) How do these changes correlate to properties such as mechanical or catalytic performance? The density, surface energy and bonding at a solid interface dramatically alter the polymer configuration, physics and mechanical properties such as surface glass transition, adhesion and hardness. The enhanced sensitivity of SFG at the buried interface is applied to three systems: a series of acrylates under compression, the compositions and segregation behavior of binary polymer polyolefin blends, and the changes in surface structure of a hydrogel as a function of hydration. In addition, a catalytically active thin film of polymer coated nanoparticles is investigated to evaluate the efficacy of SFG to provide in situ information for catalytic reactions involving small mass adsorption and/or product development. Through the use of SFG, in situ total internal reflection (TIR) was used to increase the sensitivity of SFG and provide the necessary specificity to investigate interfaces of thin polymer films and nanostructures previously considered unfeasible. The dynamic nature of thin film surfaces is examined and it is found that the non

  9. Research on Free Vibration Frequency Characteristics of Rotating Functionally Graded Material Truncated Conical Shells with Eccentric Functionally Graded Material Stringer and Ring Stiffeners

    Directory of Open Access Journals (Sweden)

    Dao Van Dung

    Full Text Available Abstract In this research work, an exact analytical solution for frequency characteristics of the free vibration of rotating functionally graded material (FGM truncated conical shells reinforced by eccentric FGM stringers and rings has been investigated by the displacement function method. Material properties of shell and stiffeners are assumed to be graded in the thickness direction according to a simple power law distribution. The change of spacing between stringers is considered. Using the Donnell shell theory, Leckhnisky smeared stiffeners technique and taking into account the influences of centrifugal force and Coriolis acceleration the governing equations are derived. For stiffened FGM conical shells, it is difficult that free vibration equations are a couple set of three variable coefficient partial differential equations. By suitable transformations and applying Galerkin method, this difficulty is overcome in the paper. The sixth order polynomial equation for w is obtained and it is used to analyze the frequency characteristics of rotating ES-FGM conical shells. Effects of stiffener, geometrics parameters, cone angle, vibration modes and rotating speed on frequency characteristics of the shell forward and backward wave are discussed in detail. The present approach proves to be reliable and accurate by comparing with published results available in the literature.

  10. Design of a hybrid reconfigurable Software Defined Radio transceiver based on frequency shift keying using multiple encoding schemes

    Directory of Open Access Journals (Sweden)

    Nikhil Marriwala

    2016-03-01

    The aim of this paper was to analyze Frequency Shift Keying (FSK Transceiver built using Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW and to measure the reduction in data errors in the presence of Forward Error Correction (FEC channel coding algorithms namely the Convolution and the Turbo Codes. Through this design a graphical representation of Bit Error Rate (BER vs Eb/N0 where (Eb is Energy per bit and (N0 is Spectral noise density has been given in the presence of Additive White Gaussian Noise (AWGN introduced in the channel. FSK is widely used for data transmission over band pass channels; hence, we have chosen FSK for the implementation of SDR. The SDR transceiver module designed has been fully implemented and has the ability to navigate over a wide range of frequencies with programmable channel bandwidth and modulation characteristics. We are able to build an interactive FSK based SDR transceiver in a shorter time with the use of LabVIEW. The outputs achieved show a low BER for very high data rates in the presence of AWGN noise.

  11. Energy Finite Element Analysis for Computing the High Frequency Vibration of the Aluminum Testbed Cylinder and Correlating the Results to Test Data

    Science.gov (United States)

    Vlahopoulos, Nickolas

    2005-01-01

    The Energy Finite Element Analysis (EFEA) is a finite element based computational method for high frequency vibration and acoustic analysis. The EFEA solves with finite elements governing differential equations for energy variables. These equations are developed from wave equations. Recently, an EFEA method for computing high frequency vibration of structures either in vacuum or in contact with a dense fluid has been presented. The presence of fluid loading has been considered through added mass and radiation damping. The EFEA developments were validated by comparing EFEA results to solutions obtained by very dense conventional finite element models and solutions from classical techniques such as statistical energy analysis (SEA) and the modal decomposition method for bodies of revolution. EFEA results have also been compared favorably with test data for the vibration and the radiated noise generated by a large scale submersible vehicle. The primary variable in EFEA is defined as the time averaged over a period and space averaged over a wavelength energy density. A joint matrix computed from the power transmission coefficients is utilized for coupling the energy density variables across any discontinuities, such as change of plate thickness, plate/stiffener junctions etc. When considering the high frequency vibration of a periodically stiffened plate or cylinder, the flexural wavelength is smaller than the interval length between two periodic stiffeners, therefore the stiffener stiffness can not be smeared by computing an equivalent rigidity for the plate or cylinder. The periodic stiffeners must be regarded as coupling components between periodic units. In this paper, Periodic Structure (PS) theory is utilized for computing the coupling joint matrix and for accounting for the periodicity characteristics.

  12. Fermi resonance and solvent dependence of the vC=O frequency shifts of Raman spectra: cyclohexanone and 2-cyclohexene-1-one

    CERN Document Server

    Nam, S I; Lee, M S; Jung, Y M

    2001-01-01

    The carbonyl stretching vibration, vC=O of 2-cyclohexene-1-one , is in Fermi resonance with a combination tone. The amount of Fermi resonance interaction between these two modes is dependent upon the amount of solute/solvent interaction due to hydrogen bonding between the carbonyl oxygen and the solvent proton. The corrected vC=O frequency of 2-cyclohexene-1-one occurs at a lower frequency than the observed vC=O mode of cyclohexanone, possibly caused by expanded conjugation effects. The carbonyl stretching modes of cyclic ketones were also affected by interaction with the ROH/CCl sub 4 mixed solvent system.

  13. Laser Doppler vibrometer employing active frequency feedback.

    Science.gov (United States)

    Chijioke, Akobuije; Lawall, John

    2008-09-20

    We present a heterodyne Michelson interferometer for vibration measurement in which feedback is used to obviate the need to unwrap phase data. The Doppler shift of a vibrating target mirror is sensed interferometrically and compensated by means of a voltage-controlled oscillator driving an acousto-optic modulator. For frequencies within the servo bandwidth, the oscillator control voltage provides a direct measurement of the target velocity. Outside the servo bandwidth, phase-sensitive detection is used to evaluate high-frequency displacements. This approach is of great interest for the frequently-occurring situation where vibration amplitudes at low frequency exceed an optical wavelength, but knowledge of the vibration spectrum at high frequency is important as well.

  14. Intrinsic Chirality and Prochirality at Air/R-(+)- and S-(-)-Limonene Interfaces: Spectral Signatures with Interference Chiral Sum-Frequency Generation Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Li; Zhang, Yun; Wei, Zhehao; Wang, Hongfei

    2014-06-04

    We report in this work detailed measurements on the chiral and achiral sum-frequency vibrational spectra in the C-H stretching vibration region (2800-3050cm-1) of the air/liquid interfaces of R-limonene and S-limonene, using the recently developed high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS). The achiral SFG spectra of R-limonene and S-limonene, as well as the equal amount (50/50) racemic mixture show that the enantiomers are with the same interfacial orientations. The interference chiral SFG spectra of the limonene enantiomers exhibit spectral signature from chiral response of the Cα-H stretching mode, and spectral signature from prochiral response of the CH2 asymmetric stretching mode, respectively. The chiral spectral feature of the Cα-H stretching mode changes sign from R-limonene to S-limonene, and disappears for the 50/50 racemic mixture. While the prochiral spectral feature of the CH2 asymmetric stretching mode is the same for R-limonene and S-limonene, and also surprisingly remains the same for the 50/50 racemic mixture. These results provided detail information in understanding the structure and chirality of molecular interfaces, and demonstrated the sensitivity and potential of SFG-VS as unique spectroscopic tool for chirality characterization and chiral recognition at the molecular interface.

  15. The Effect of an Added Mass on the Frequency Shifts of a Clamped-Clamped Microbeam for Bio-Mass Detection

    KAUST Repository

    Bouchaala, Adam M.

    2016-12-05

    We present analytical formulations to calculate the induced resonance frequency shifts of electrically actuated clamped-clamped microbeams due to an added mass. Based on the Euler-Bernoulli beam theory, we investigate the linear dynamic responses of the beams added masses, which are modeled as discrete point masses. Analytical expressions based on perturbation techniques and a one-mode Galerkin approximation are developed to calculate accurately the frequency shifts under a DC voltage as a function of the added mass and position. The analytical results are compared to numerical solution of the eigenvalue problem. Results are shown for the fundamental as well as the higher-order modes of the beams. The results indicate a significant increase in the frequency shift, and hence the sensitivity of detection, when scaling down to nano scale and using higher-order modes.

  16. Phase shift cavity ring down and Fourier transform infrared measurements of C-H vibrational transitions, energy levels, and intensities of (CH3)3Si-C≡C-H

    Science.gov (United States)

    Barroso, Jenny Z.; Perez-Delgado, Yasnahir; Manzanares, Carlos E.

    2013-07-01

    Phase shift cavity ring down and Fourier transform IR techniques have been used to observe the C-H stretch fundamental and overtone absorptions of the acetylenic (Δυ = 1-5) and methyl (Δυ = 1-6) C-H bonds of trimethyl-silyl-acetylene [(CH3)3CSi≡CH] at 295 K. Harmonic frequencies ω(ν1), ωa, and ωs and anharmonicities x(ν1), ωaxa, ωsxs were calculated for the acetylenic, methyl out-of-plane, and methyl in-plane C-H bonds, respectively. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. A hot band, assigned as υν1 + ν24 - ν24 is observed for transitions with Δυ = 1-5 in a region near the acetylenic stretch. The intensity of the hot band is reduced considerably at 240 K. The strength of a Fermi resonance between C-Ha transition (υνa) and the combination band ((υ-1)νa + 2νbend) with (υ = 3-6) was calculated using the experimental perturbed energies and relative intensities. The main bands are separated by computer deconvolution and are integrated at each level to get the experimental band strengths. For methyl absorptions, the dipole moment function is expanded as a function of two C-H stretching coordinates and the intensities are calculated in terms of the HCAO model where only the C-H modes are considered. Acetylenic intensities are derived with a one dimensional dipole moment function. The expansion coefficients are obtained from molecular orbital calculations. The intensities are calculated without using adjustable parameters and they are of the same order of magnitude of the experimental intensities for all C-H transitions.

  17. Dependence of the frequency spectrum of small amplitude vibrations superimposed on finite deformations of a nonlinear, cylindrical elastic body on residual stress

    KAUST Repository

    Gorb, Yuliya

    2010-11-01

    We model and analyze the response of nonlinear, residually stressed elastic bodies subjected to small amplitude vibrations superimposed upon large deformations. The problem derives from modeling the use of intravascular ultrasound (IVUS) imaging to interrogate atherosclerotic plaques in vivo in large arteries. The goal of this investigation is twofold: (i) introduce a modeling framework for residual stress that unlike traditional Fung type classical opening angle models may be used for a diseased artery, and (ii) investigate the sensitivity of the spectra of small amplitude high frequency time harmonic vibrations superimposed on a large deformation to the details of the residual stress stored in arteries through a numerical simulation using physiologic parameter values under both low and high blood pressure loadings. The modeling framework also points the way towards an inverse problem using IVUS techniques to estimate residual stress in healthy and diseased arteries. © 2010 Elsevier Ltd. All rights reserved.

  18. An electroactive polymer based concept for vibration reduction via adaptive supports

    Science.gov (United States)

    Wolf, Kai; Röglin, Tobias; Haase, Frerk; Finnberg, Torsten; Steinhoff, Bernd

    2008-03-01

    A concept for the suppression of resonant vibration of an elastic system undergoing forced vibration coupled to electroactive polymer (EAP) actuators based on dielectric elastomers is demonstrated. The actuators are utilized to vary the stiffness of the end support of a clamped beam, which is forced to harmonic vibration via a piezoelectric patch. Due to the nonlinear dependency of the elastic modulus of the EAP material, the modulus can be changed by inducing an electrostrictive deformation. The resulting change in stiffness of the EAP actuator leads to a shift of the resonance frequencies of the vibrating beam, enabling an effective reduction of the vibration amplitude by an external electric signal. Using a custom-built setup employing an aluminum vibrating beam coupled on both sides to electrodized strips of VHB tape, a significant reduction of the resonance amplitude was achieved. The effectiveness of this concept compared to other active and passive concepts of vibration reduction is discussed.

  19. Analysis of motion of inverted pendulum with vibrating suspension axis at low-frequency excitation as an illustration of a new approach for solving equations without explicit small parameter

    DEFF Research Database (Denmark)

    Sorokin, Vladislav

    2014-01-01

    In the classical papers (see, e.g. P.L. Kapitsa, Pendulum with vibrating axis of suspension. Usp. Fiz. Nauk 44 1 (1954) 7-20 (in Russian)) motion of pendulum with vibrating suspension axis was considered in the case when frequency of external loading is much higher than the natural frequency...... of the pendulum in the absence of this loading. The present paper is concerned with the analysis of inverted pendulums motion at unconventional values of parameters. Case when frequency of external loading and the natural frequency of the pendulum in the absence of this loading are of the same order is studied...

  20. Development of a semi-active dynamic vibration absorber for longitudinal vibration of propulsion shaft system based on magnetorheological elastomer

    Science.gov (United States)

    Liu, Gaoyu; Lu, Kun; Zou, Donglin; Xie, Zhongliang; Rao, Zhushi; Ta, Na

    2017-07-01

    The control of the longitudinal pulsating force and the vibration generated is very important to improve the stealth performance of a submarine. Magnetorheological elastomer (MRE) is a kind of intelligent composite material, whose mechanical properties can be continuously, rapidly and reversibly controlled by an external magnetic field. It can be used as variable-stiffness components in the design of a semi-active dynamic vibration absorber (SDVA), which is one of the effective means of longitudinal vibration control. In this paper, an SDVA is designed based on the MRE’s magnetic-induced variable stiffness characteristic. Firstly, a mechanical model of the propulsion shaft system with the SDVA is proposed, theoretically discussed and numerically validated. Then, the mechanical performance of the MRE under different magnetic fields is tested. In addition, the magnetic circuit and the overall structure of the SDVA are designed. Furthermore, electromagnetic and thermodynamic simulations are carried out to guarantee the structural design. The frequency shift property of the SDVA is found through dynamic simulations and validated by a frequency shift experiment. Lastly, the vibration absorption capacity of the SDVA is investigated. The results show that the magnetorheological effect of the MRE and the frequency shift of the SDVA are obvious; the SDVA has relatively acceptable vibration absorption capacity.

  1. External-field shifts in precision spectroscopy of hydrogen molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Bakalov, Dimitar, E-mail: dbakalov@inrne.bas.bg [INRNE, Bulgarian Academy of Sciences (Bulgaria); Korobov, Vladimir [Joint Institute for Nuclear Research (Russian Federation); Schiller, Stephan [Heinrich-Heine-Universitat Dusseldorf, Institut fur Experimentalphysik (Germany)

    2015-08-15

    The Effective Hamiltonian of the hydrogen molecular ions is a convenient tool for the evaluation of the shift of the energy levels of the ro-vibrational states and the frequencies of the transitions between them, due to external electric and magnetic fields. Using the Effective Hamiltonian, composite frequencies of suppressed susceptibility to external fields are constructed.

  2. The acoustic power of a vibrating clamped circular plate revisited in the wide low frequency range using expansion into the radial polynomials.

    Science.gov (United States)

    Rdzanek, Wojciech P

    2016-06-01

    This study deals with the classical problem of sound radiation of an excited clamped circular plate embedded into a flat rigid baffle. The system of the two coupled differential equations is solved, one for the excited and damped vibrations of the plate and the other one-the Helmholtz equation. An approach using the expansion into radial polynomials leads to results for the modal impedance coefficients useful for a comprehensive numerical analysis of sound radiation. The results obtained are accurate and efficient in a wide low frequency range and can easily be adopted for a simply supported circular plate. The fluid loading is included providing accurate results in resonance.

  3. Landslides in Vibrating Sand-Box; Preliminary Results Reporting Types of Slope-Failure and Apparent Frequency Magnitude (Area) Power Law Relations.

    Science.gov (United States)

    Aharonov, E.; Katz, O.

    2004-12-01

    It is recognized that hazardous natural phenomena such as earthquakes, forest fires and landslides often follow a power-law frequency-magnitude relations. Naturally occurring landslides populations, both seismic and hydrologically triggered, show non-cumulative power law frequency-magnitude (area) relations with slope of 2.3-3 for the large landslides part of the population. Numerical simulations of sand pile avalanches obtain a non-cumulative frequency-size distribution which also follows a power-law but with a slope of 1. In this work we study the nature and area distribution of slope failure triggered in a vibrating wet (1%wt) sand box. We used a 28 cubic cm box with sand pile crest resting on the top of one inner face and foot on the opposite face base. Initial slope angle was about 50deg, vibrating frequency 10Hz and individual test duration lasted a few minutes. Three different accelerations directions were tested: vertical, slope perpendicular, and normal horizontal accelerations. Acceleration magnitudes ranged from 0.1 to 1.2g. Slope performance was continuously recorded using a digital video camera. We observed that vertical vibrations larger than 1.0 g, induced mainly a few centimeter wide block-slides and toppling from a step like scarp that migrated up the slope. Block sliding rate was approximately one every few seconds. Final slope cross-section is S shaped with normal faulting at its crest. Final slope angle was about 35deg. Lower accelerations or lower initial slope angles yielded only surface grain flow. Horizontal shaking yielded different behavior: Above a threshold acceleration (0.5g and 0.7g for shaking parallel and normal to slope direction, respectively), surface flow occurred initially. It was followed by a box-wide slump, which first remained coherent and then progressively disintegrated. Lower accelerations or initial slope angle yield only surface grain flow. Finally, the upper surface areas of tens of block-slides induced in the above

  4. Imaging spectroscopy of the missing REMPI bands of methyl radicals: Final touches on all vibrational frequencies of the 3p Rydberg states.

    Science.gov (United States)

    Pan, Huilin; Liu, Kopin

    2018-01-07

    (2 + 1) resonance-enhanced multiphoton ionization (REMPI) detection of methyl radicals, in particular that via the intermediate 3p Rydberg states, has shown to be a powerful method and thus enjoyed a wide range of applications. Methyl has six vibrational modes. Among them-including partially and fully deuterated isotopologs-four out of twenty vibrational frequencies in the intermediate 3p states have so far eluded direct spectroscopic determination. Here, by exploiting the imaging spectroscopy approach to a few judiciously selected chemical reactions, the four long-sought REMPI bands-CHD2(611), CH2D(311), CH2D(511), and CH2D(611)-are discovered, which complete the REMPI identification for probing any vibrational mode of excitation of methyl radical and its isotopologs. These results, in conjunction with those previously reported yet scattered in the literature, are summarized here for ready reference, which should provide all necessary information for further spectral assignments and future studies of chemical dynamics using this versatile REMPI scheme.

  5. Minimization of the Vibration Energy of Thin-Plate Structures and the Application to the Reduction of Gearbox Vibration

    Science.gov (United States)

    Inoue, Katsumi; Krantz, Timothy L.

    1995-01-01

    While the vibration analysis of gear systems has been developed, a systematic approach to the reduction of gearbox vibration has been lacking. The technique of reducing vibration by shifting natural frequencies is proposed here for gearboxes and other thin-plate structures using the theories of finite elements, modal analysis, and optimization. A triangular shell element with 18 degrees of freedom is developed for structural and dynamic analysis. To optimize, the overall vibration energy is adopted as the objective function to be minimized at the excitation frequency by varying the design variable (element thickness) under the constraint of overall constant weight. Modal analysis is used to determine the sensitivity of the vibration energy as a function of the eigenvalues and eigenvectors. The optimum design is found by the gradient projection method and a unidimensional search procedure. By applying the computer code to design problems for beams and plates, it was verified that the proposed method is effective in reducing vibration energy. The computer code is also applied to redesign the NASA Lewis gear noise rig test gearbox housing. As one example, only the shape of the top plate is varied, and the vibration energy levels of all the surfaces are reduced, yielding an overall reduction of 1/5 compared to the initial design. As a second example, the shapes of the top and two side plates are varied to yield an overall reduction in vibration energy of 1/30.

  6. The study of the effects of mechanical vibration at infrasound frequency on [(3)H]-thymidine incorporation into DNA of E. coli K-12.

    Science.gov (United States)

    Martirosyan, Varsik; Baghdasaryan, Naira; Ayrapetyan, Sinerik

    2013-03-01

    The aim of the present work was to investigate the frequency-dependent effects of mechanical vibration at infrasound frequency (MV at IS frequency or MV) on E. coli K-12 growth by investigating the cell proliferation, using radioactive [(3)H]-thymidine assay. The frequency-dependent effects of MV were shown that it could either stimulate or inhibit the growth of microbes. However, the mechanism through which the MV effects affect the bacterial cells is not clear yet. It was suggested that the aqua medium can serve as a target through which the biological effect of MV on microbes could be realized. To check this hypothesis the frequency-dependent effect (2, 4, 6, 8, 10 Hz) of MV on the bacterial growth in cases of exposure the preliminary treated microbes-free medium and microbes containing medium were studied. It has been shown that MV at 4, 8, and 10 Hz frequency has inhibition effects, while at 2 and 6 Hz has stimulation effects on cell proliferation.

  7. A batch-fabricated electret-biased wideband MEMS vibration energy harvester with frequency-up conversion behavior powering a UHF wireless sensor node

    Science.gov (United States)

    Lu, Y.; O'Riordan, E.; Cottone, F.; Boisseau, S.; Galayko, D.; Blokhina, E.; Marty, F.; Basset, P.

    2016-12-01

    This paper reports a batch-fabricated, low-frequency and wideband MEMS electrostatic vibration energy harvester (e-VEH), which implements corona-charged vertical electrets and nonlinear elastic stoppers. A numeric model is used to perform parametric study, where we observe a wideband bi-modality resulting from nonlinearity. The nonlinear stoppers improve the bandwidth and induce a frequency-up feature at low frequencies. When the e-VEH works with a bias of 45 V, the power reaches a maximum value of 6.6 μW at 428 Hz and 2.0 g rms, and is above 1 μW at 50 Hz. When the frequency drops below 60 Hz, a ‘frequency-up’ conversion behavior is observed with peaks of power at 34 Hz and 52 Hz. The  -3 dB bandwidth is more than 60% of its central frequency, both including and excluding the hysteresis introduced by the nonlinear stoppers. We also perform experiments with wideband Gaussian noise. The device is eventually tested with an RF data transmission setup, where a communication node with an internal temperature sensor is powered. Every 2 min, a data transmission at 868 MHz is performed by the sensor node supplied by the e-VEH, and received at a distance of up to 15 m.

  8. Effects of 18-month low-magnitude high-frequency vibration on fall rate and fracture risks in 710 community elderly--a cluster-randomized controlled trial.

    Science.gov (United States)

    Leung, K S; Li, C Y; Tse, Y K; Choy, T K; Leung, P C; Hung, V W Y; Chan, S Y; Leung, A H C; Cheung, W H

    2014-06-01

    This study is a prospective cluster-randomized controlled clinical trial involving 710 elderly subjects to investigate the long-term effects of low-magnitude high-frequency vibration (LMHFV) on fall and fracture rates, muscle performance, and bone quality. The results confirmed that LMHFV is effective in reducing fall incidence and enhancing muscle performance in the elderly. Falls are direct causes of fragility fracture in the elderly. LMHFV has been shown to improve muscle function and bone quality. This study is to investigate the efficacy of LMHFV in preventing fall and fractures among the elderly in the community. A cluster-randomized controlled trial was conducted with 710 postmenopausal females over 60 years. A total of 364 participants received daily 20 min LMHFV (35 Hz, 0.3 g), 5 days/week for 18 months; 346 participants served as control. Fall or fracture rate was taken as the primary outcome. Also, quadriceps muscle strength, balancing abilities, bone mineral density (BMD), and quality of life (QoL) assessments were done at 0, 9, and 18 months. With an average of 66.0% compliance in the vibration group, 18.6% of 334 vibration group subjects reported fall or fracture incidences compared with 28.7% of 327 in the control (adjusted HR = 0.56, p = 0.001). The fracture rate of vibration and control groups were 1.1 and 2.3 % respectively (p = 0.171). Significant improvements were found in reaction time, movement velocity, and maximum excursion of balancing ability assessment, and also the quadriceps muscle strength (p < 0.001). No significant differences were found in the overall change of BMD. Minimal adverse effects were documented. LMHFV is effective in fall prevention with improved muscle strength and balancing ability in the elderly. We recommend its use in the community as an effective fall prevention program and to decrease related injuries.

  9. Heterogeneous Dynamics of Coupled Vibrations

    NARCIS (Netherlands)

    Cringus, Dan; Jansen, Thomas I. C.; Pshenichnikov, Maxim S.; Schoenlein, RW; Corkum, P; DeSilvestri, S; Nelson, KA; Riedle, E

    2009-01-01

    Frequency-dependent dynamics of coupled stretch vibrations of a water molecule are revealed by 2D IR correlation spectroscopy. These are caused by non-Gaussian fluctuations of the environment around the individual OH stretch vibrations.

  10. Low-frequency vibrational spectrum of molecular nitrogen complex rhenium(1) chloro(dinitrogen) tetrakis(dimethylphenylphosphine)

    Energy Technology Data Exchange (ETDEWEB)

    Kachapina, L.M.; Kichigina, G.A.; Makhaev, V.D.; Borisov, A.P. (AN SSSR, Chernogolovka. Inst. Khimicheskoj Fiziki)

    1981-10-01

    The investigation results of IR and Raman spectra in the region of 600-170 cm/sup -1/ of molecular nitrogen complex-rhenium (1) chloro (dinitrogen) tetrakis (dimethyl-phenylphosphine)- Cl(PMe/sub 2/Ph)/sub 4/ReN/sub 2/ are presented. The IR spectra have been recorded using the ''Perkin-Elmer 325'' spectrophotometer. The samples have been prepared in the form of tablets with KBr (650-400 cm/sup -1/) and CsI (450-200 cm/sup -1/) and suspensions in vaseline oil. The Raman spectra have been measured using the ''Coderg-PHO'' spectrometer with the recording by FEhU-106. The samples have been taken in the form of polycrystals. The lines attributed to the valent vibration of the Re-N bond and deformation vibration of ReNN fragment have been identified in the spectra.

  11. Influence of Low-Frequency Vibration and Modification on Solidification and Mechanical Properties of Al-Si Casting Alloy

    Directory of Open Access Journals (Sweden)

    Vadim Selivorstov

    2017-05-01

    Full Text Available One of the major aims of the modern materials foundry industry is the achievement of advanced mechanical properties of metals, especially of light non-ferrous alloys such as aluminum. Usually an alloying process is applied to obtain the required properties of aluminum alloys. However, the presented work describes an alternative approach through the application of vibration treatment, modification by ultrafine powder and a combination of these two methods. Microstructural studies followed by image analysis revealed the refinement of α-Al grains with an increase in the Si network area around them. As evidence, the improvement of the mechanical properties of Al casting alloy was detected. It was found that the alloys subjected to the vibration treatment displayed an increase in tensile and yield strengths by 20% and 10%, respectively.

  12. Analytical expressions for bulk moduli and frequencies of volumetrical vibrations of fullerenes C20 and C60

    OpenAIRE

    KOVALEV OLEG; KUZKIN VITALY

    2011-01-01

    In the present paper simple analytical expressions connecting bulk moduli for fullerenes C20 and C60 with stiffness of interatomic bond and geometrical characteristics of the fullerenes are derived. Ambiguities related to definition of the bulk modulus are discussed. Nonlinear volumetrical deformation of the fullerenes is considered. Pressure-volume dependence for the fullerenes under volumetrical compression are derived. Simple analytical model for volumetrical vibrations of the fullerenes i...

  13. Optimal geometries and harmonic vibrational frequencies of the global minima of water clusters (H2O)n, n = 2–6, and several hexamer local minima at the CCSD(T) level of theory

    Energy Technology Data Exchange (ETDEWEB)

    Miliordos, Evangelos; Aprà, Edoardo; Xantheas, Sotiris S.

    2013-01-01

    We report the first optimum geometries and harmonic vibrational frequencies for the ring pentamer and several water hexamer (prism, cage, cyclic and two book) at the CCSD(T)/aug-cc-pVDZ level of theory. All five hexamer isomer minima previously reported by MP2 are also minima on the CCSD(T) potential energy surface (PES). In addition, all CCSD(T) minimum energy structures for the n=2-6 cluster isomers are quite close to the ones previously obtained by MP2 on the respective PESs, as confirmed by a modified Procrustes analysis that quantifies the difference between any two cluster geometries. The CCSD(T) results confirm the cooperative effect of the homodromic ring networks (systematic contraction of the nearest-neighbor (nn) intermolecular separations with cluster size) previously reported by MP2, albeit with O-O distances shorter by ~0.02 Å, indicating that MP2 overcorrects this effect. The harmonic frequencies at the minimum geometries were obtained by the double differentiation of the CCSD(T) energy using an efficient scheme based on internal coordinates that reduces the number of required single point energy evaluations by ~15% when compared to the corresponding double differentiation using Cartesian coordinates. Negligible differences between MP2 and CCSD(T) are found for the librational modes, while uniform increases of ~15 and ~25 cm-1 are observed for the bending and “free” OH harmonic frequencies. The largest differences between MP2 and CCSD(T) are observed for the harmonic hydrogen bonded frequencies. The CCSD(T) red shifts from the monomer frequencies (Δω) are smaller than the MP2 ones, due to the fact that the former produces shorter elongations (ΔR) of the respective hydrogen bonded OH lengths from the monomer value with respect to the latter. Both the MP2 and CCSD(T) results for the hydrogen bonded frequencies were found to closely follow the relation - Δω = s · ΔR, with a rate of s = 20.3 cm-1 / 0.001 Å. The CCSD

  14. Comparative study of time-dependent effects of 4 and 8 Hz mechanical vibration at infrasound frequency on E. coli K-12 cells proliferation.

    Science.gov (United States)

    Martirosyan, Varsik; Ayrapetyan, Sinerik

    2015-01-01

    The aim of the present work is to study the time-dependent effects of mechanical vibration (MV) at infrasound (IS) frequency at 4 and 8 Hz on E. coli K-12 growth by investigating the cell proliferation, using radioactive [(3)H]-thymidine assay. In our previous work it was suggested that the aqua medium can serve as a target through which the biological effect of MV on microbes could be realized. At the same time it was shown that microbes have mechanosensors on the surface of the cells and can sense small changes of the external environment. The obtained results were shown that the time-dependent effects of MV at 4 and 8 Hz frequency could either stimulate or inhibit the growth of microbes depending from exposure time. It more particularly, the invention relates to a method for controlling biological functions through the application of mechanical vibration, thus making it possible to artificially control the functions of bacterial cells, which will allow us to develop method that can be used in agriculture, industry, medicine, biotechnology to control microbial growth.

  15. Sensing Performance Analysis on Quartz Tuning Fork-Probe at the High Order Vibration Mode for Multi-Frequency Scanning Probe Microscopy

    Directory of Open Access Journals (Sweden)

    Xiaofei Zhang

    2018-01-01

    Full Text Available Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the low mode and detect near-field optically induced forces (based on the 2nd in-plane mode called the high mode. Particularly, the high mode sensing performance of the QTF-p is an important issue for characterizing the tip-sample interactions and achieving higher resolution microscopic imaging but the related researches are insufficient. Here, we investigate the vibration performance of QTF-p at high mode based on the experiment and finite element method. The frequency spectrum characteristics are obtained by our homemade laser Doppler vibrometer system. The effects of the properties of the connecting glue layer and the probe features on the dynamic response of the QTF-p sensor at the high mode are investigated for optimization design. Finally, compared with the low mode, an obvious improvement of quality factor, of almost 50%, is obtained at the high mode. Meanwhile, the QTF-p sensor has a high force sensing sensitivity and a large sensing range at the high mode, indicating a broad application prospect for force sensing.

  16. Interfacial Water Structure and Cation Binding with the Dppc Phosphate at Air /aqueous Interfaces Studied by Vibrational Sum Frequency Generation Spectroscopy

    Science.gov (United States)

    Hua, Wei; Allen, Heather C.

    2012-06-01

    Molecular-level knowledge of water structure and cation binding specificity to lipid headgroups at lipid/water interfaces plays a key role in many relevant chemical, biological, and environmental processes. To obtain information on the molecular organization at aqueous interfaces, vibrational sum frequency generation (VSFG) has been applied extensively as an interface-specific technique. Dipalmitoylphosphocholine (DPPC) is a major component of cell membranes and has been used as a proxy for the organic coating on fat-coated aerosols. In the present work, in addition to conventional VSFG studies on cation interaction with the phosphate headgroup moiety of DPPC, we employ phase-sensitive vibrational sum frequency generation (PS-VSFG) to investigate the average direction of the transition dipole moment of interfacial water molecules. The average orientation of water structure at DPPC/water interfaces is inferred. DPPC orients interfacial water molecules on average with their net transition dipole moment pointing towards the surface. The influence of Na+, K+, Mg2+, Ca2+ is identified in regard to interfacial water structure and DPPC headgroup organization. Ca2+ is observed to have greater impact on the water structure and a unique binding affinity to the phosphate headgroup relative to other cations tested. In highly concentrated Ca2+ regimes the already disturbed interfacial hydrogen-bonding network reorganizes to resemble that of the neat salt solution interface.

  17. Sensing Performance Analysis on Quartz Tuning Fork-Probe at the High Order Vibration Mode for Multi-Frequency Scanning Probe Microscopy.

    Science.gov (United States)

    Zhang, Xiaofei; Gao, Fengli; Li, Xide

    2018-01-24

    Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p) sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the low mode) and detect near-field optically induced forces (based on the 2nd in-plane mode called the high mode). Particularly, the high mode sensing performance of the QTF-p is an important issue for characterizing the tip-sample interactions and achieving higher resolution microscopic imaging but the related researches are insufficient. Here, we investigate the vibration performance of QTF-p at high mode based on the experiment and finite element method. The frequency spectrum characteristics are obtained by our homemade laser Doppler vibrometer system. The effects of the properties of the connecting glue layer and the probe features on the dynamic response of the QTF-p sensor at the high mode are investigated for optimization design. Finally, compared with the low mode, an obvious improvement of quality factor, of almost 50%, is obtained at the high mode. Meanwhile, the QTF-p sensor has a high force sensing sensitivity and a large sensing range at the high mode, indicating a broad application prospect for force sensing.

  18. Molecular structure, Normal Coordinate Analysis, harmonic vibrational frequencies, Natural Bond Orbital, TD-DFT calculations and biological activity analysis of antioxidant drug 7-hydroxycoumarin

    Science.gov (United States)

    Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.

    2013-01-01

    In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the σ* and π* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis.

  19. Investigation on Phase Shifting Effect on The Voltage Output of Piezoelectric Cantilever Array

    Science.gov (United States)

    Jing, B. Y.; Leong, K. S.

    2017-06-01

    This paper analyses the phase shifting of the output waveform produced by piezoelectric cantilevers under a range of vibration frequencies. The phase shift of four piezoelectric cantilevers with different resonant frequency are inspected while it is excited with the vibration from the electrodynamics shaker at a range of frequencies from 100 Hz to 500 Hz with the acceleration level (g-force) fixed at constant magnitude of 1g-level (9.81 m/s2). Time different and Lissajous pattern methods were used in this research to measure the phase shift of the output waveform. Both methods show similar result where the major phase shift happened at the resonant frequency of respective cantilevers. The phase difference remains low around 0 degrees or in other term in phase before the resonant frequency of the cantilever. When the frequency of the vibration source approaches the resonant frequency of respective cantilever, the phase different start to increase rapidly and reach 180 degree which is out of phase after the resonant frequency. This major phase shifting contributes to the significant rise of the gap in between the peaks formed when multiple piezoelectric cantilevers are connected together. As a result, it indirectly improves the output performance of the piezoelectric cantilevers array.

  20. Doppler-shifting effects on frequency spectra of gravity waves observed near the summer mesopause at high latitude

    Science.gov (United States)

    Fritts, David C.; Wang, Ding-Yi

    1991-01-01

    Results are presented of radar observations of horizontal and vertical velocities near the summer mesopause at Poker Flat (Alaska), showing that the observed vertical velocity spectra were influenced strongly by Doppler-shifting effects. The horizontal velocity spectra, however, were relatively insensitive to horizontal wind speed. The observed spectra are compared with predicted spectra for various models of the intrinsic motion spectrum and degrees of Doppler shifting.

  1. Local vibrations and lift performance of low Reynolds number airfoil

    Directory of Open Access Journals (Sweden)

    TariqAmin Khan

    2017-06-01

    Full Text Available The 2D incompressible Navier-Stokes equations are solved based on the finite volume method and dynamic mesh technique is used to carry out partial fluid structure interaction. The local flexible structure (hereinafter termed as flexible structure vibrates in a single mode located on the upper surface of the airfoil. The Influence of vibration frequency and amplitude are examined and the corresponding fluid flow characteristics are investigated which add complexity to the inherent problem in unsteady flow. The study is conducted for flow over NACA0012 airfoil at 600≤Re≤3000 at a low angle of attack. Vibration of flexible structure induces a secondary vortex which modifies the pressure distribution and lift performance of the airfoil. At some moderate vibration amplitude, frequency synchronization or lock-in phenomenon occurs when the vibration frequency is close to the characteristic frequency of rigid airfoil. Evolution and shedding of vortices corresponding to the deformation of flexible structure depends on the Reynolds number. In the case of Re≤1000, the deformation of flexible structure is considered in-phase with the vortex shedding i.e., increasing maximum lift is linked with the positive deformation of flexible structure. At Re=1500 a phase shift of about 1/π exists while they are out-of-phase at Re>1500. Moreover, the oscillation amplitude of lift coefficient increases with increasing vibration amplitude for Re≤1500 while it decreases with increasing vibration amplitude for Re>1500. As a result of frequency lock-in, the average lift coefficient is increased with increasing vibration amplitude for all investigated Reynolds numbers (Re. The maximum increase in the average lift coefficient is 19.72% within the range of investigated parameters.

  2. Frequency tuning and directional sensitivity of tympanal vibrations in the field cricket Gryllus bimaculatus

    DEFF Research Database (Denmark)

    Lankheet, Martin J.; Cerkvenik, Uroš; Larsen, Ole Næsbye

    2017-01-01

    Female field crickets use phonotaxis to locate males by their calling song. Male song production and female behavioural sensitivity form a pair of matched frequency filters, which in Gryllus bimaculatus are tuned to a frequency of about 4.7 kHz. Directional sensitivity is supported by an elaborat...

  3. Shifted dispersion-induced radio-frequency fading in microwave photonic filters using a dual-input Mach-Zehnder electro-optic modulator.

    Science.gov (United States)

    Li, Liwei; Yi, Xiaoke; Huang, Thomas X H; Minasian, Robert A

    2013-04-01

    A simple microwave photonic processor structure with single passband response, and widely tunable capability, is demonstrated. It is based on the principle of shifted dispersion-induced radio-frequency (RF) fading by using a dual-input Mach-Zehnder electro-optic modulator (EOM) that is fed from a broadband optical source with unbalanced input fiber lengths into the upper and lower arms of the EOM, in combination with a dispersive medium. This topology consequently produces a spectral response equivalent to the curve of the dispersion-induced RF fading that is shifted from the conventional baseband location to high frequencies. Therefore, an equivalent single passband is formed without the requirement of the conventional tap coefficients. Experimental results verify the structure and demonstrate a continuously tunable microwave filter exhibiting shape invariance and a single passband. In addition, the filter response sidelobe suppression is also significantly improved by applying a Gaussian windowed profile to the broadband optical source.

  4. Evolution of the frequency-dependent polarization-angle phase-shift in the microwave radiation-induced magnetoresistance oscillations

    Science.gov (United States)

    Liu, Han-Chun; Samaraweera, Rasanga L.; Reichl, C.; Wegscheider, W.; Mani, R. G.

    2017-06-01

    We report the evolution of the phase shift, θ 0, extracted from traces of the diagonal resistance, Rxx , vs. the linear polarization angle, θ, at oscillatory extrema of the microwave radiation induced magnetoresistance oscillations over the 36 ≤ f ≤ 40 GHz band in GaAs/AlGaAs system. A reference phase shift for the linear polarization angle in the vicinity of the specimen is obtained with the help of a sensitive carbon resistor. We fit an empirical cosine square law to the sinusoidal responses of Rxx vs. θ to extract the phase shift θ 0. The quasi-continuous variation θ 0 vs. f trace suggests a preferable polarization orientation for the specimen, and the f- and B- independence of overall average of θ 0.

  5. Evaluation of hand-arm vibration reducing effect of anti-vibration glove

    OpenAIRE

    樹野, 淳也; 前田, 節雄; 横田, 和樹; 平, 雄一郎

    2015-01-01

    Many kinds of the anti-vibration glove have been developed for reducing hand-arm vibration during the operation with vibration tools. International standard ISO 10819 evaluates the physical effect of gloves' vibration transmissibility but not evaluates the physiological effect of human hands. Thus, in this paper, we proposed the evaluation using the temporary threshold shift of vibrotactile perception threshold to evaluate the hand-arm vibration reducing effect of anti-vibration glove. We per...

  6. Low-Magnitude High-Frequency Vibration Accelerated the Foot Wound Healing of n5-streptozotocin-induced Diabetic Rats by Enhancing Glucose Transporter 4 and Blood Microcirculation.

    Science.gov (United States)

    Yu, Caroline Oi-Ling; Leung, Kwok-Sui; Jiang, Jonney Lei; Wang, Tina Bai-Yan; Chow, Simon Kwoon-Ho; Cheung, Wing-Hoi

    2017-09-14

    Delayed wound healing is a Type 2 diabetes mellitus (DM) complication caused by hyperglycemia, systemic inflammation, and decreased blood microcirculation. Skeletal muscles are also affected by hyperglycemia, resulting in reduced blood flow and glucose uptake. Low Magnitude High Frequency Vibration (LMHFV) has been proven to be beneficial to muscle contractility and blood microcirculation. We hypothesized that LMHFV could accelerate the wound healing of n5-streptozotocin (n5-STZ)-induced DM rats by enhancing muscle activity and blood microcirculation. This study investigated the effects of LMHFV in an open foot wound created on the footpad of n5-STZ-induced DM rats (DM_V), compared with no-treatment DM (DM), non-DM vibration (Ctrl_V) and non-DM control rats (Ctrl) on Days 1, 4, 8 and 13. Results showed that the foot wounds of DM_V and Ctrl_V rats were significantly reduced in size compared to DM and Ctrl rats, respectively, at Day 13. The blood glucose level of DM_V rats was significantly reduced, while the glucose transporter 4 (GLUT4) expression and blood microcirculation of DM_V rats were significantly enhanced in comparison to those of DM rats. In conclusion, LMHFV can accelerate the foot wound healing process of n5-STZ rats.

  7. Finite element analysis and frequency shift studies for the bridge coupler of the coupled cavity linear accelerator of the spallation neutron source.

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z. (Zukun)

    2001-01-01

    The Spallation Neutron Source (SNS) is an accelerator-based neutron scattering research facility. The linear accelerator (linac) is the principal accelerating structure and divided into a room-temperature linac and a superconducting linac. The normal conducting linac system that consists of a Drift Tube Linac (DTL) and a Coupled Cavity Linac (CCL) is to be built by Los Alamos National Laboratory. The CCL structure is 55.36-meters long. It accelerates H- beam from 86.8 Mev to 185.6 Mev at operating frequency of 805 MHz. This side coupled cavity structure has 8 cells per segment, 12 segments and 11 bridge couplers per module, and 4 modules total. A 5-MW klystron powers each module. The number 3 and number 9 bridge coupler of each module are connected to the 5-MW RF power supply. The bridge coupler with length of 2.5 {beta}{gamma} is a three-cell structure and located between the segments and allows power flow through the module. The center cell of each bridge coupler is excited during normal operation. To obtain a uniform electromagnetic filed and meet the resonant frequency shift, the RF induced heat must be removed. Thus, the thermal deformation and frequency shift studies are performed via numerical simulations in order to have an appropriate cooling design and predict the frequency shift under operation. The center cell of the bridge coupler also contains a large 4-inch slug tuner and a tuning post that used to provide bulk frequency adjustment and field intensity adjustment, so that produce the proper total field distribution in the module assembly.

  8. Using high-frequency vibrations and non-linear inclusions to create metamaterials with adjustable effective properties

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov; Thomsen, Jon Juel

    2009-01-01

    We investigate how high-frequency (HF) excitation combined with strongly non-linear elasticity may influence the effective properties for low-frequency wave propagation. The HF effects are demonstrated for linear spring-mass chains with embedded non-linear parts. The investigated mechanical syste...... static displacements and forces can be created by using HF excitation with structures having asymmetric displacement-force characteristics....

  9. Recovery model of temporary threshold shifts from exposures with the same L_Aeq,T and different frequency components

    DEFF Research Database (Denmark)

    Ordonez, Rodrigo; Hammershøi, Dorte

    2005-01-01

    Temporary Threshold Shifts (TTS) were determined for 9 subjects exposed to three different band-passed signals taken from one channel of a binaural recording of an industrial mill. The three 2-octave bands were: Low (125 to 500 Hz), mid (500 Hz to 2 kHz), and high (2 kHz to 8 kHz). The band...

  10. Amine Chemistry at Aqueous Interfaces: The Study of Organic Amines in Neutralizing Acidic Gases at an Air/Water Surface Using Vibrational Sum Frequency Spectroscopy

    Science.gov (United States)

    McWilliams, L.; Wren, S. N.; Valley, N. A.; Richmond, G.

    2014-12-01

    Small organic bases have been measured in atmospheric samples, with their sources ranging from industrial processing to animal husbandry. These small organic amines are often highly soluble, being found in atmospheric condensed phases such as fogwater and rainwater. Additionally, they display acid-neutralization ability often greater than ammonia, yet little is known regarding their kinetic and thermodynamic properties. This presentation will describe the molecular level details of a model amine system at the vapor/liquid interface in the presence of acidic gas. We find that this amine system shows very unique properties in terms of its bonding, structure, and orientation at aqueous surfaces. The results of our studies using a combination of computation, vibrational sum frequency spectroscopy, and surface tension will report the properties inherent to these atmospherically relevant species at aqueous surfaces.

  11. Sum frequency generation vibrational spectroscopy (SFG-VS) for complex molecular surfaces and interfaces: Spectral lineshape measurement and analysis plus some controversial issues

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hong-Fei

    2016-12-01

    Sum-frequency generation vibrational spectroscopy (SFG-VS) was first developed in the 1980s and it has been proven a uniquely sensitive and surface/interface selective spectroscopic probe for characterization of the structure, conformation and dynamics of molecular surfaces and interfaces. In recent years, there has been significant progress in the development of methodology and instrumentation in the SFG-VS toolbox that has significantly broadened the application to complex molecular surfaces and interfaces. In this review, after presenting a unified view on the theory and methodology focusing on the SFG-VS spectral lineshape, as well as the new opportunities in SFG-VS applications with such developments, some of the controversial issues that have been puzzling the community are to be discussed. The aim of this review is to present to the researchers and students interested in molecular surfaces and interfacial sciences up-to-date perspectives complementary to the existing textbooks and reviews on SFG-VS.

  12. Sum Frequency Generation Vibrational Spectroscopy and Kinetic Study of 2-Methylfuran and 2,5-Dimethylfuran Hydrogenation over 7 nm Platinum Cubic Nanoparticles

    KAUST Repository

    Aliaga, Cesar

    2011-04-28

    Sum frequency generation vibrational spectroscopy and kinetic measurements obtained from gas chromatography were used to study the adsorption and hydrogenation of 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) over cubic Pt nanoparticles of 7 nm average size, synthesized by colloidal methods and cleaned by ultraviolet light and ozone treatment. Reactions carried out at atmospheric pressure in the temperature range of 20-120 °C produced dihydro and tetrahydro species, as well as ring-opening products (alcohols) and ring-cracking products, showing high selectivity toward ring opening throughout the entire temperature range. The aromatic rings (MF and DMF) adsorbed parallel to the nanoparticle surface. Results yield insight into various surface reaction intermediates and the reason for the significantly lower selectivity for ring cracking in DMF hydrogenation compared to MF hydrogenation. © 2011 American Chemical Society.

  13. VIBRATION ISOLATION SYSTEM PROBABILITY ANALYSIS

    Directory of Open Access Journals (Sweden)

    Smirnov Vladimir Alexandrovich

    2012-10-01

    Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.

  14. Catalyzed hydrogenation of nitrogen and ethylene on metal (Fe, Pt) single crystal surfaces and effects of coadsorption: A sum frequency generation vibrational spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Westerberg, Staffan Per Gustav [Univ. of California, Berkeley, CA (United States)

    2004-01-01

    High-pressure catalytic reactions and associated processes, such as adsorption have been studied on a molecular level on single crystal surfaces. Sum Frequency Generation (SFG) vibrational spectroscopy together with Auger Electron Spectroscopy (AES), Temperature Programmed Desorption (TPD) and Gas Chromatography (GC) were used to investigate the nature of species on catalytic surfaces and to measure the catalytic reaction rates. Special attention has been directed at studying high-pressure reactions and in particular, ammonia synthesis in order to identify reaction intermediates and the influence of adsorbates on the surface during reaction conditions. The adsorption of gases N2, H2, O2 and NH3 that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by sum frequency generation vibrational spectroscopy using an integrated Ultra-High Vacuum (UHV)/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH2 (~3325 cm-1) and NH (~3235 cm-1) under high pressure of ammonia (200 Torr) on the clean Fe(111) surface. Addition of 0.5 Torr of oxygen to 200 Torr of ammonia does not significantly change the bonding of dissociation intermediates to the surface. However, it leads to a phase change of nearly 180° between the resonant and non-resonant second order non-linear susceptibility of the surface, demonstrated by the reversal of the SFG spectral features. Heating the surface in the presence of 200 Torr ammonia and 0.5 Torr oxygen reduces the oxygen coverage, which can be seen from the SFG spectra as another relative phase change of 180°. The reduction of the oxide is also supported by Auger electron spectroscopy. The result suggests that the phase change of the spectral features could serve as a sensitive indicator of the chemical environment of the adsorbates.

  15. Electronic and vibrational spectroscopy and vibrationally mediated photodissociation of V+(OCO).

    Science.gov (United States)

    Citir, Murat; Altinay, Gokhan; Metz, Ricardo B

    2006-04-20

    Electronic spectra of gas-phase V+(OCO) are measured in the near-infrared from 6050 to 7420 cm(-1) and in the visible from 15,500 to 16,560 cm(-1), using photofragment spectroscopy. The near-IR band is complex, with a 107 cm(-1) progression in the metal-ligand stretch. The visible band shows clearly resolved vibrational progressions in the metal-ligand stretch and rock, and in the OCO bend, as observed by Brucat and co-workers. A vibrational hot band gives the metal-ligand stretch frequency in the ground electronic state nu3'' = 210 cm(-1). The OCO antisymmetric stretch frequency in the ground electronic state (nu1'') is measured by using vibrationally mediated photodissociation. An IR laser vibrationally excites ions to nu1'' = 1. Vibrationally excited ions selectively dissociate following absorption of a second, visible photon at the nu1' = 1 CO2, due to interaction with the metal. Larger blue shifts observed for complexes with fewer ligands agree with trends seen for larger V+(OCO)n clusters.

  16. Shaping frequency response of a vibrating plate for passive and active control applications by simultaneous optimization of arrangement of additional masses and ribs. Part II: Optimization

    Science.gov (United States)

    Wrona, Stanislaw; Pawelczyk, Marek

    2016-03-01

    It was shown in Part I that an ability to shape frequency response of a vibrating plate according to precisely defined demands has a very high practical potential. It can be used to improve acoustic radiation of the plate for required frequencies or enhance acoustic isolation of noise barriers and device casings. It can be used for both passive and active control. The proposed method is based on mounting several additional ribs and masses (passive and/or active) to the plate surface at locations followed from an optimisation process. In Part I a relevant model of such structure, as a function of arrangement of the additional elements was derived and validated. The model allows calculating natural frequencies and mode-shapes of the whole structure. The aim of this companion paper, Part II, is to present the second stage of the method. This is an optimization process that results in arrangement of the elements guaranteeing desired plate frequency response, and enhancement of controllability and observability measures. For that purpose appropriate cost functions, and constraints followed from technological feasibility are defined. Then, a memetic algorithm is employed to obtain a numerical solution with parameters of the arrangement. The optimization results are initially presented for simple cases to validate the method. Then, more complex scenarios are analysed with very special demands concerning the frequency response to present the full potential of the method. Subsequently, a laboratory experiment is presented and discussed. Finally, other areas of applications of the proposed method are shown and conclusions for future research are drawn.

  17. Temperature Compensated Crystal Oscillator (TCXO) Design Aids: Frequency-Temperature Resonator Characteristics as Shifted by Series Capacitors

    Science.gov (United States)

    1977-05-01

    factor, while X is defined as X = (T/2)(f/f(1 )), (3) with f the frequency variable ( w/27), and f(l) the antiresonance frequency at the fundamental...the frequency spectruml, cioLi-negtigibly. For coatings of mass in- per unit area lumped on each surface, the reduced mass-loading variable is j= Fi/ph...2. The quantity multiplying Tk in (40) is called the Onoe funcion : 46 G (M) = +2k2/D. is plotted versus 0 for various k values and for M = 1, 3, and

  18. Detecting Molecular Rotational Dynamics Complementing the Low-Frequency Terahertz Vibrations in a Zirconium-Based Metal-Organic Framework

    Science.gov (United States)

    Ryder, Matthew R.; Van de Voorde, Ben; Civalleri, Bartolomeo; Bennett, Thomas D.; Mukhopadhyay, Sanghamitra; Cinque, Gianfelice; Fernandez-Alonso, Felix; De Vos, Dirk; Rudić, Svemir; Tan, Jin-Chong

    2017-06-01

    We show clear experimental evidence of cooperative terahertz (THz) dynamics observed below 3 THz (˜100 cm-1 ), for a low-symmetry Zr-based metal-organic framework structure, termed MIL-140A [ZrO (O2C-C 6H4-CO2) ]. Utilizing a combination of high-resolution inelastic neutron scattering and synchrotron radiation far-infrared spectroscopy, we measured low-energy vibrations originating from the hindered rotations of organic linkers, whose energy barriers and detailed dynamics have been elucidated via ab initio density functional theory calculations. The complex pore architecture caused by the THz rotations has been characterized. We discovered an array of soft modes with trampolinelike motions, which could potentially be the source of anomalous mechanical phenomena such as negative thermal expansion. Our results demonstrate coordinated shear dynamics (2.47 THz), a mechanism which we have shown to destabilize the framework structure, in the exact crystallographic direction of the minimum shear modulus (Gmin ).

  19. Palladium(II) and platinum(II) complexes containing benzimidazole ligands: Molecular structures, vibrational frequencies and cytotoxicity

    Science.gov (United States)

    Abdel Ghani, Nour T.; Mansour, Ahmed M.

    2011-04-01

    (1H-benzimidazol-2-ylmethyl)-(4-methoxyl-phenyl)-amine (L 1), (1H-benzimidazol-2-ylmethyl)-(4-methyl-phenyl)-amine (L 2) and their Pd(II) and Pt(II) complexes have been synthesized as potential anticancer compounds and their structures were elucidated using a variety of physico-chemical techniques. Theoretical calculations invoking geometry optimization, vibrational assignments, 1H NMR, charge distribution and molecular orbital description HOMO and LUMO were done using density functional theory. Natural bond orbital analysis (NBO) method was performed to provide details about the type of hybridization and the nature of bonding in the studied complexes. Strong coordination bonds (LP(1)N11 → σ *(M sbnd Cl22)) and (LP(1)N21 → σ *(M sbnd Cl23)) (M = Pd or Pt) result from donation of electron density from a lone pair orbital on the nitrogen atoms to the acceptor metal molecular orbitals. The experimental results and the calculated molecular parameters revealed square-planar geometries around the metallic centre through the pyridine-type nitrogen of the benzimidazole ring and secondary amino group and two chlorine atoms. The activation thermodynamic parameters were calculated using non-isothermal methods. The synthesized ligands, in comparison to their metal complexes were screened for their antibacterial activity. In addition, the studied complexes showed activity against three cell lines of different origin, breast cancer (MCF-7), Colon Carcinoma (HCT) and human heptacellular carcinoma (Hep-G2) comparable to cis-platin.

  20. Vibrational Probes: From Small Molecule Solvatochromism Theory and Experiments to Applications in Complex Systems.

    Science.gov (United States)

    Błasiak, Bartosz; Londergan, Casey H; Webb, Lauren J; Cho, Minhaeng

    2017-04-18

    vibrational Stark effect theory has been considered to be quite appealing and, even in some cases, e.g., carbonyl stretch modes in amide, ester, ketone, and carbonate compounds or proteins, it works quantitatively well, which makes it highly useful in determining the strength of local electric field around the IR chromophore. However, noting that the vibrational frequency shift results from changes of solute-solvent intermolecular interaction potential along its normal coordinate, Pauli exclusion repulsion, polarization, charge transfer, and dispersion interactions, in addition to the electrostatic interaction between distributed charges of both vibrational chromophore and solvent molecules, are to be properly included in the theoretical description of vibrational solvatochromism. Since the electrostatic and nonelectrostatic intermolecular interaction components have distinctively different distance and orientation dependences, they affect the solvatochromic vibrational properties in a completely different manner. Over the past few years, we have developed a systematic approach to simulating vibrational solvatochromic data based on the effective fragment potential approach, one of the most accurate and rigorous theories on intermolecular interactions. We have further elucidated the interplay of local electric field with the general vibrational solvatochromism of small IR probes in either solvents or complicated biological systems, with emphasis on contributions from non-Coulombic intermolecular interactions to vibrational frequency shifts and fluctuations. With its rigorous foundation and close relation to quantitative interpretation of experimental data, this and related theoretical approaches and experiments will be of use in studying and quantifying the structure and dynamics of biomolecules with unprecedented time and spatial resolution when combined with time-resolved vibrational spectroscopy and chemically sensitive vibrational imaging techniques.

  1. Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study.

    Science.gov (United States)

    Villa, Federica; Magnani, Alessandro; Maggioni, Martina A; Stahn, Alexander; Rampichini, Susanna; Merati, Giampiero; Castiglioni, Paolo

    2016-05-11

    Bioelectrical Impedance Spectroscopy (BIS) allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments simultaneously, over a broad frequency range, for long periods and with high measurements rate. These needs are often required to evaluate exercise tests in sports or rehabilitation medicine, or to assess gravitational stresses in aerospace medicine. Therefore, the aim of this work is to present a new wearable prototype for monitoring multi-segment and multi-frequency BIS unobtrusively over long periods. Our prototype guarantees low weight, small size and low power consumption. An analog board with current-injecting and voltage-sensing electrodes across three body segments interfaces a digital board that generates square-wave current stimuli and computes impedance at 10 frequencies from 1 to 796 kHz. To evaluate the information derivable from our device, we monitored the BIS of three body segments in a volunteer before, during and after physical exercise and postural shift. We show that it can describe the dynamics of exercise-induced changes and the effect of a sit-to-stand maneuver in active and inactive muscular districts separately and simultaneously.

  2. Wearable Multi-Frequency and Multi-Segment Bioelectrical Impedance Spectroscopy for Unobtrusively Tracking Body Fluid Shifts during Physical Activity in Real-Field Applications: A Preliminary Study

    Directory of Open Access Journals (Sweden)

    Federica Villa

    2016-05-01

    Full Text Available Bioelectrical Impedance Spectroscopy (BIS allows assessing the composition of body districts noninvasively and quickly, potentially providing important physiological/clinical information. However, neither portable commercial instruments nor more advanced wearable prototypes simultaneously satisfy the demanding needs of unobtrusively tracking body fluid shifts in different segments simultaneously, over a broad frequency range, for long periods and with high measurements rate. These needs are often required to evaluate exercise tests in sports or rehabilitation medicine, or to assess gravitational stresses in aerospace medicine. Therefore, the aim of this work is to present a new wearable prototype for monitoring multi-segment and multi-frequency BIS unobtrusively over long periods. Our prototype guarantees low weight, small size and low power consumption. An analog board with current-injecting and voltage-sensing electrodes across three body segments interfaces a digital board that generates square-wave current stimuli and computes impedance at 10 frequencies from 1 to 796 kHz. To evaluate the information derivable from our device, we monitored the BIS of three body segments in a volunteer before, during and after physical exercise and postural shift. We show that it can describe the dynamics of exercise-induced changes and the effect of a sit-to-stand maneuver in active and inactive muscular districts separately and simultaneously.

  3. High-Frequency Signal Injection Method Based on Duty Cycle Shifting Without Maximum Fundamental Voltage Magnitude Loss

    DEFF Research Database (Denmark)

    Wang, Dong; Lu, Kaiyuan; Rasmussen, Peter Omand

    2017-01-01

    position estimation algorithm using the proposed HFSI method is developed and applied to a synchronous reluctance machine drive system. The proposed algorithm focuses on the medium- to high-speed range with the advantage of no filter needed for position information extraction and a machine......-frequency signal at half of the switching frequency without the necessity to sacrifice the machine fundamental voltage amplitude. This may be utilized to develop a new position estimation algorithm without involving the machine inductance in the medium- to high-speed range. As an application example, a new...

  4. Analysis of mechanical vibrations in large vertical pumps: two cases of natural frequency excitations; Analisis de vibraciones mecanicas en grandes bombas verticales: dos casos de excitacion de frecuencias naturales

    Energy Technology Data Exchange (ETDEWEB)

    Ercoli, L.; La Malfa, S. [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), Bahia Blanca (Argentina). Inst. de Mecanica Aplicada]|[Universidad Tecnologica Nacional (Argentina). Grupo Analisis de Sistemas Mecanicos

    1995-07-01

    This study presents experimental dynamic analysis of two big vertical pumps induced to vibrate due to the excitation of natural frequencies of the structural systems: pump-mounting. It is demonstrated that a proper diagnostic of the working condition avoids unecessary and time-consuming equipment stops, with the consequent saving in the production costs. (author)

  5. Shifts in gamma phase-amplitude coupling frequency from theta to alpha over posterior cortex during visual tasks

    Directory of Open Access Journals (Sweden)

    Bradley Voytek

    2010-10-01

    Full Text Available The phase of ongoing theta (4-8 Hz and alpha (8-12 Hz electrophysiological oscillations is coupled to high gamma (80-150 Hz amplitude, which suggests that low frequency oscillations modulate local cortical activity. While this phase-amplitude coupling (PAC has been demonstrated in a variety of tasks and cortical regions, it has not been shown whether task demands differentially affect the regional distribution of the preferred low-frequency coupling to high gamma. To address this issue we investigated multiple-rhythm theta/alpha phase to high gamma amplitude PAC in two subjects with implanted subdural electrocorticographic grids. We show that high gamma amplitude couples to the theta and alpha troughs and demonstrate that, during visual tasks, alpha/high gamma coupling preferentially increases in visual cortical regions. These results suggest that low-frequency phase to high-frequency amplitude PAC is modulated by behavioral task and may reflect a mechanism for selection between communicating neuronal networks.

  6. A Novel Type of Series Load Resonant High Frequency Soft Switching Inverter with Phase Shift Control Scheme

    Science.gov (United States)

    Kifune, Hiroyasu; Yamaguchi, Takumi; Hatanaka, Yoshihiro; Nakaoka, Mutsuo

    The voltage source full bridge series load resonant high frequency soft switching inverter using pulse phaseshift modulation (PSM) strategy is proposed, which can operate ZVS in the left hand side bridge leg and ZCS in the right side bridge leg. This inverter using IGBTs employs two passive components and does not need any additional auxiliary circuit for the active power switch to achieve soft switching commutation, and it has wide soft switching operation region from full power to 3% light power. Furthermore, constant frequency power regulation that is required for induction-heating power applications is introduced on the basis of PSM. In this paper, steady state switching modes of the inverter treated here and its power regulation scheme by PSM are described under a soft switching scheme. Because the proposed inverter can operate at series resonant frequency of series resonant circuit under soft switching condition, it is easy to design the value of series resonant capacitor. The design methods of loss-less snubbing circuit components for soft switching are described to reduce switching losses effectively. The feasible experiment of the proposed inverter is implemented to demonstrate the power regulation performance of proposed high frequency inverter, high efficiency 97.6% at full power condition is obtained.

  7. Stochastic modelling of shifts in allele frequencies reveals a strongly polygynous mating system in the re-introduced Asiatic wild ass.

    Science.gov (United States)

    Renan, Sharon; Greenbaum, Gili; Shahar, Naama; Templeton, Alan R; Bouskila, Amos; Bar-David, Shirli

    2015-04-01

    Small populations are prone to loss of genetic variation and hence to a reduction in their evolutionary potential. Therefore, studying the mating system of small populations and its potential effects on genetic drift and genetic diversity is of high importance for their viability assessments. The traditional method for studying genetic mating systems is paternity analysis. Yet, as small populations are often rare and elusive, the genetic data required for paternity analysis are frequently unavailable. The endangered Asiatic wild ass (Equus hemionus), like all equids, displays a behaviourally polygynous mating system; however, the level of polygyny has never been measured genetically in wild equids. Combining noninvasive genetic data with stochastic modelling of shifts in allele frequencies, we developed an alternative approach to paternity analysis for studying the genetic mating system of the re-introduced Asiatic wild ass in the Negev Desert, Israel. We compared the shifts in allele frequencies (as a measure of genetic drift) that have occurred in the wild ass population since re-introduction onset to simulated scenarios under different proportions of mating males. We revealed a strongly polygynous mating system in which less than 25% of all males participate in the mating process each generation. This strongly polygynous mating system and its potential effect on the re-introduced population's genetic diversity could have significant consequences for the long-term persistence of the population in the Negev. The stochastic modelling approach and the use of allele-frequency shifts can be further applied to systems that are affected by genetic drift and for which genetic data are limited. © 2015 John Wiley & Sons Ltd.

  8. Experimental investigation of torsional vibration isolation using Magneto Rheological Elastomer

    Directory of Open Access Journals (Sweden)

    Praveen Shenoy K

    2018-01-01

    Full Text Available Rotating systems suffer from lateral and torsional vibrations which have detrimental effect on the roto-dynamic performance. Many available technologies such as vibration isolators and vibration absorbers deal with the torsional vibrations to a certain extent, however passive isolators and absorbers find less application when the input conditions are dynamic. The present work discusses use of a smart material called as Magneto Rheological Elastomer (MRE, whose properties can be changed based on magnetic field input, as a potential isolator for torsional vibrations under dynamic loading conditions. Carbonyl Iron Particles (CIP of average size 5 μm were mixed with RTV Silicone rubber to form the MRE. The effect of magnetic field on the system parameters was comprehended under impulse loading conditions using a custom built in-house system. Series arrangement of accelerometers were used to differentiate between the torsional and the bending modes of vibration of the system. Impact hammer tests were carried out on the torsional system to study its response, in the presence and absence of magnetic field. The tests revealed a shift in torsional frequency in the presence of magnetic field which elucidates the ability of MRE to work as a potential vibration isolator for torsional systems.

  9. Rectangular Parallelepiped Vibration in Plane Strain State

    OpenAIRE

    Hanckowiak, Jerzy

    2004-01-01

    In this paper we present a vibration spectrum of a homogenous parallelepiped (HP) under the action of volume and surface forces resulting from the exponent displacements entering the Fourier transforms. Vibration under the action of axial surface tractions and the free vibration are described separately. A relationship between the high frequency vibration and boundary conditions (BC) is also considered.

  10. High-Pressure Catalytic Reactions of C6 Hydrocarbons on PlatinumSingle-Crystals and nanoparticles: A Sum Frequency Generation VibrationalSpectroscopic and Kinetic Study

    Energy Technology Data Exchange (ETDEWEB)

    Bratlie, Kaitlin [Univ. of California, Berkeley, CA (United States)

    2007-01-01

    Catalytic reactions of cyclohexene, benzene, n-hexane, 2-methylpentane, 3-methylpentane, and 1-hexene on platinum catalysts were monitored in situ via sum frequency generation (SFG) vibrational spectroscopy and gas chromatography (GC). SFG is a surface specific vibrational spectroscopic tool capable of monitoring submonolayer coverages under reaction conditions without gas-phase interference. SFG was used to identify the surface intermediates present during catalytic processes on Pt(111) and Pt(100) single-crystals and on cubic and cuboctahedra Pt nanoparticles in the Torr pressure regime and at high temperatures (300K-450K). At low pressures (<10-6 Torr), cyclohexene hydrogenated and dehydrogenates to form cyclohexyl (C6H11) and π-allyl C6H9, respectively, on Pt(100). Increasing pressures to 1.5 Torr form cyclohexyl, π-allyl C6H9, and 1,4-cyclohexadiene, illustrating the necessity to investigate catalytic reactions at high-pressures. Simultaneously, GC was used to acquire turnover rates that were correlated to reactive intermediates observed spectroscopically. Benzene hydrogenation on Pt(111) and Pt(100) illustrated structure sensitivity via both vibrational spectroscopy and kinetics. Both cyclohexane and cyclohexene were produced on Pt(111), while only cyclohexane was formed on Pt(100). Additionally, π-allyl c-C6H9 was found only on Pt(100), indicating that cyclohexene rapidly dehydrogenates on the (100) surface. The structure insensitive production of cyclohexane was found to exhibit a compensation effect and was analyzed using the selective energy transfer (SET) model. The SET model suggests that the Pt-H system donates energy to the E2u mode of free benzene, which leads to catalysis. Linear C6 (n-hexane, 2-methylpentane, 3-methylpentane, and 1-hexene) hydrocarbons were also investigated in the presence and absence of excess hydrogen on Pt

  11. Probing the structure and nano-scale mechanical properties of polymer surfaces with scanning force microscopy and sum frequency vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gracias, David Hugo [Univ. of California, Berkeley, CA (United States)

    1999-05-01

    Scanning Force Microscopy (SFM) has been used to quantitatively measure the elastic modulus, friction and hardness of polymer surfaces with special emphasis on polyethylene and polypropylene. In the experiments, tips of different radii of curvature ranging from 20 nm to 1000 nm have been used and the high pressure applied by the SFM have been observed to affect the values obtained in the measurements. The contact of the SFM tip with the polymer surface is explained by fitting the experimental curves to theoretical predictions of contact mechanics. Sum Frequency Generation (SFG) Vibrational Spectroscopy has been used to measure vibrational spectra of polymer surfaces in the vibrational range of 2700 to 3100 cm-1. Strong correlations are established between surface chemistry and surface structure as probed by SFG and mechanical properties measured by SFM on the surfaces. In these studies segregation of low surface energy moieties, from the bulk of the polymer to the surface have been studied. It was found that surface segregation occurs in miscible polymer blends and a small concentration of surface active polymer can be used to totally modify the surface properties of the blend. A novel high vacuum SFM was built to do temperature dependent measurements of mechanical changes occurring at the surface of polypropylene during the glass transition of the polymer. Using this instrument the modulus and friction of polypropylene was measured in the range of room temperature to ˜-60°C. An increase in the ordering of the backbone of the polymer chains below the glass transition measured by SFG correlates well with the increase in modulus measured on the same surface with SFM. Friction measurements have been done on polyethylene with three different instruments by applying loads ranging from nN to sub newton i.e. over eight orders of magnitude. Pressure and contact area effects were observed to play a significant role in determining the frictional response of the polymer

  12. The effects of two different frequencies of whole-body vibration on knee extensors strength in healthy young volunteers: a randomized trial

    Science.gov (United States)

    Esmaeilzadeh, S.; Akpinar, M.; Polat, S.; Yildiz, A.; Oral, A.

    2015-01-01

    The aim of this study was to investigate the effects of two different frequencies of whole-body vibration (WBV) training on knee extensors muscle strength in healthy young volunteers. Twenty-two eligible healthy untrained young women aged 22-31 years were allocated randomly to the 30-Hz (n=11) and 50-Hz (n=11) groups. They participated in a supervised WBV training program that consisted of 24 sessions on a synchronous vertical vibration platform (peak-to-peak displacement: 2-4 mm; type of exercises: semi-squat, one-legged squat, and lunge positions on right leg; set numbers: 2-24) three times per week for 8 weeks. Isometric and dynamic strength of the knee extensors were measured prior to and at the end of the 8-week training. In the 30-Hz group, there was a significant increase in the maximal voluntary isometric contraction (p=0.039) and the concentric peak torque (p=0.018) of knee extensors and these changes were significant (p<0.05) compared with the 50-Hz group. In addition, the eccentric peak torque of knee extensors was increased significantly in both groups (p<0.05); however, there was no significant difference between the two groups (p=0.873). We concluded that 8 weeks WBV training in 30 Hz was more effective than 50 Hz to increase the isometric contraction and dynamic strength of knee extensors as measured using peak concentric torque and equally effective with 50 Hz in improving eccentric torque of knee extensors in healthy young untrained women. PMID:26636279

  13. Suggestions for improving the long-term effects of treatments for stuttering: A Review and synthesis of frequency-shifted feedback and operant techniques

    Science.gov (United States)

    Reed, Phil; Howell, Peter

    2008-01-01

    The present article outlines the potential benefits to the treatment of stuttering, if altered auditory feedback methods, especially frequency-shifted feedback, were to be combined with behaviour modification techniques. A potential framework for understanding the integration of these approaches is presented in the context of assessing the limitations of each approach in isolation. A number of suggestions concerning the use of partial prompting and partial reinforcement, drawn from the animal conditioning literature, that may promote the efficacy of such a treatment are also made. PMID:18259587

  14. Analysis of the resonance frequency shift in cylindrical cavities containing a sphere and its prediction based on the Boltzmann-Ehrenfest principle

    DEFF Research Database (Denmark)

    Orozco Santillán, Arturo; Cutanda Henriquez, Vicente

    2008-01-01

    It is known that forces generated by high-level acoustic waves can compensate for the weight of small samples, which can be suspended in a fluid. To achieve this, a standing wave is created in a resonant enclosure, which can be open or closed to the external medium. This phenomenon, called Acoustic...... levitation, has numerous applications in containerless study and processing of materials. Although it is possible to levitate a sample for long periods of time, instabilities can appear under certain conditions. One of the causes of oscillational instabilities is the change of the resonance frequency...... of the cavity due to the presence of the levitated object. The Boltzmann-Ehrenfest principle has been used to obtain an analytical expression for the resonance frequency shift in a cylindrical cavity produced by a small sphere, with kR

  15. Vibration Attenuation of Plate Using Multiple Vibration Absorbers

    Directory of Open Access Journals (Sweden)

    Zaman Izzuddin

    2014-07-01

    Full Text Available Vibrations are undesired phenomenon and it can cause harm, distress and unsettling influence to the systems or structures, for example, aircraft, automobile, machinery and building. One of the approach to limit this vibration by introducing passive vibration absorber attached to the structure. In this paper, the adequacy of utilizing passive vibration absorbers are investigated. The vibration absorber system is designed to minimize the vibration of a thin plate fixed along edges. The plate’s vibration characteristics, such as, natural frequency and mode shape are determined using three techniques: theoretical equations, finite element (FE analysis and experiment. The results demonstrate that the first four natural frequencies of fixed-fixed ends plate are 48, 121, 193 and 242 Hz, and these results are corroborated well with theoretical, FE simulation and experiment. The experiment work is further carried out with attached single and multiple vibration absorbers onto plate by tuning the absorber’s frequency to match with the excitation frequency. The outcomes depict that multiple vibration absorbers are more viable in lessening the global structural vibration.

  16. High-resolution, high-frequency wavelength shift detection of optical signals with low-cost, compact readouts

    Science.gov (United States)

    Schuh, A.; Hegyi, A.; Raghavan, A.; Lochbaum, A.; Schwartz, J.,; Kiesel, P.

    2015-05-01

    Fiber-optics (FO) have great potential for distributed sensing in various harsh environment applications. Their advantages include high resolution and multiplexing capabilities, inherent immunity to electromagnetic interference, and low weight/volume. However, their widespread adoption in commercial applications has been considerably limited by the high cost, size, weight, and lack of capabilities of the readout unit used to interpret the FO signals. PARC has developed a breakthrough wavelength shift detection (WSD) technology that is capable of reading out signals from wavelength-encoded FO and other optical sensors with high sensitivity using a compact, high-speed and low-cost unit. In this paper, its calibration and noise performance is demonstrated for high-resolution (up to 1,45 fm/√Hz) acoustic emission (AE) detection of fast (up to 1 MHz) dynamic strain signals.

  17. Image-Guided Ultrasound Characterization of Volatile Sub-Micron Phase-Shift Droplets in the 20-40 MHz Frequency Range.

    Science.gov (United States)

    Sheeran, Paul S; Daghighi, Yasaman; Yoo, Kimoon; Williams, Ross; Cherin, Emmanuel; Foster, F Stuart; Burns, Peter N

    2016-03-01

    Phase-shift perfluorocarbon droplets are designed to convert from the liquid to the gas state by the external application of acoustic or optical energy. Although droplet vaporization has been investigated extensively at ultrasonic frequencies between 1 and 10 MHz, few studies have characterized performance at the higher frequencies commonly used in small animal imaging. In this study, we use standard B-mode imaging sequences on a pre-clinical ultrasound platform to both image and activate sub-micron decafluorobutane droplet populations in vitro and in vivo at center frequencies in the range of 20-40 MHz. Results show that droplets remain stable against vaporization at low imaging pressures but are vaporized at peak negative pressures near 3.5 MPa at the three frequencies tested. This study also found that a small number of size outliers present in the distribution can greatly influence droplet performance. Removal of these outliers results in a more accurate assessment of the vaporization threshold and produces free-flowing microbubbles upon vaporization in the mouse kidney. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  18. Vibrations of rotating machinery

    CERN Document Server

    Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick

    2017-01-01

    This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...

  19. High-resolution quantization based on soliton self-frequency shift and spectral compression in a bi-directional comb-fiber architecture

    Science.gov (United States)

    Zhang, Xuyan; Zhang, Zhiyao; Wang, Shubing; Liang, Dong; Li, Heping; Liu, Yong

    2018-03-01

    We propose and demonstrate an approach that can achieve high-resolution quantization by employing soliton self-frequency shift and spectral compression. Our approach is based on a bi-directional comb-fiber architecture which is composed of a Sagnac-loop-based mirror and a comb-like combination of N sections of interleaved single-mode fibers and high nonlinear fibers. The Sagnac-loop-based mirror placed at the terminal of a bus line reflects the optical pulses back to the bus line to achieve additional N-stage spectral compression, thus single-stage soliton self-frequency shift (SSFS) and (2 N - 1)-stage spectral compression are realized in the bi-directional scheme. The fiber length in the architecture is numerically optimized, and the proposed quantization scheme is evaluated by both simulation and experiment in the case of N = 2. In the experiment, a quantization resolution of 6.2 bits is obtained, which is 1.2-bit higher than that of its uni-directional counterpart.

  20. On the influence of freight trains on humans: a laboratory investigation of the impact of nocturnal low frequency vibration and noise on sleep and heart rate.

    Science.gov (United States)

    Smith, Michael G; Croy, Ilona; Ogren, Mikael; Persson Waye, Kerstin

    2013-01-01

    A substantial increase in transportation of goods on railway may be hindered by public fear of increased vibration and noise leading to annoyance and sleep disturbance. As the majority of freight trains run during night time, the impact upon sleep is expected to be the most serious adverse effect. The impact of nocturnal vibration on sleep is an area currently lacking in knowledge. We experimentally investigated sleep disturbance with the aim to ascertain the impact of increasing vibration amplitude. The impacts of various amplitudes of horizontal vibrations on sleep disturbance and heart rate were investigated in a laboratory study. Cardiac accelerations were assessed using a combination of polysomnography and ECG recordings. Sleep was assessed subjectively using questionnaires. Twelve young, healthy subjects slept for six nights in the sleep laboratory, with one habituation night, one control night and four nights with a variation of vibration exposures whilst maintaining the same noise exposure. With increasing vibration amplitude, we found a decrease in latency and increase in amplitude of heart rate as well as a reduction in sleep quality and increase in sleep disturbance. We concluded that nocturnal vibration has a negative impact on sleep and that the impact increases with greater vibration amplitude. Sleep disturbance has short- and long-term health consequences. Therefore, it is necessary to define levels that protect residents against sleep disruptive vibrations that may arise from night time railway freight traffic.

  1. On the influence of freight trains on humans: a laboratory investigation of the impact of nocturnal low frequency vibration and noise on sleep and heart rate.

    Directory of Open Access Journals (Sweden)

    Michael G Smith

    Full Text Available BACKGROUND: A substantial increase in transportation of goods on railway may be hindered by public fear of increased vibration and noise leading to annoyance and sleep disturbance. As the majority of freight trains run during night time, the impact upon sleep is expected to be the most serious adverse effect. The impact of nocturnal vibration on sleep is an area currently lacking in knowledge. We experimentally investigated sleep disturbance with the aim to ascertain the impact of increasing vibration amplitude. METHODOLOGY/PRINCIPAL FINDINGS: The impacts of various amplitudes of horizontal vibrations on sleep disturbance and heart rate were investigated in a laboratory study. Cardiac accelerations were assessed using a combination of polysomnography and ECG recordings. Sleep was assessed subjectively using questionnaires. Twelve young, healthy subjects slept for six nights in the sleep laboratory, with one habituation night, one control night and four nights with a variation of vibration exposures whilst maintaining the same noise exposure. With increasing vibration amplitude, we found a decrease in latency and increase in amplitude of heart rate as well as a reduction in sleep quality and increase in sleep disturbance. CONCLUSIONS/SIGNIFICANCE: We concluded that nocturnal vibration has a negative impact on sleep and that the impact increases with greater vibration amplitude. Sleep disturbance has short- and long-term health consequences. Therefore, it is necessary to define levels that protect residents against sleep disruptive vibrations that may arise from night time railway freight traffic.

  2. Probing crystal structure and mesoscale assembly of cellulose microfibrils in plant cell walls, tunicate tests, and bacterial films using vibrational sum frequency generation (SFG) spectroscopy.

    Science.gov (United States)

    Lee, Christopher M; Kafle, Kabindra; Park, Yong Bum; Kim, Seong H

    2014-06-14

    This study reports that the noncentrosymmetry and phase synchronization requirements of the sum frequency generation (SFG) process can be used to distinguish the three-dimensional organization of crystalline cellulose distributed in amorphous matrices. Crystalline cellulose is produced as microfibrils with a few nanometer diameters by plants, tunicates, and bacteria. Crystalline cellulose microfibrils are embedded in wall matrix polymers and assembled into hierarchical structures that are precisely designed for specific biological and mechanical functions. The cellulose microfibril assemblies inside cell walls are extremely difficult to probe. The comparison of vibrational SFG spectra of uniaxially-aligned and disordered films of cellulose Iβ nanocrystals revealed that the spectral features cannot be fully explained with the crystallographic unit structure of cellulose. The overall SFG intensity, the alkyl peak shape, and the alkyl/hydroxyl intensity ratio are sensitive to the lateral packing and net directionality of the cellulose microfibrils within the SFG coherence length scale. It was also found that the OH SFG stretch peaks could be deconvoluted to find the polymorphic crystal structures of cellulose (Iα and Iβ). These findings were used to investigate the cellulose crystal structure and mesoscale cellulose microfibril packing in intact plant cell walls, tunicate tests, and bacterial films.

  3. Studies of Heterogeneously Catalyzed Liquid-Phase Alcohol Oxidation on Platinum bySum-frequency Generation Vibrational Spectroscopy and Reaction Rate Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Christopher [Univ. of California, Berkeley, CA (United States)

    2014-05-15

    Compared to many branches of chemistry, the molecular level study of catalytically active surfaces is young. Only with the invention of ultrahigh vacuum technology in the past half century has it been possible to carry out experiments that yield useful molecular information about the reactive occurrences at a surface. The reason is two-fold: low pressure is necessary to keep a surface clean for an amount of time long enough to perform an experiment, and most atomic scale techniques that are surface speci c (x-ray photoelectron spectroscopy, electron energy loss spectroscopy, Auger electron spectroscopy, etc.) cannot be used at ambient pressures, because electrons, which act as chemical probes in these techniques, are easily scattered by molecules. Sum-frequency generation (SFG) vibrational spectroscopy is one technique that can provide molecular level information from the surface without the necessity for high vacuum. Since the advent of SFG as a surface spectroscopic tool it has proved its worth in the studies of surface catalyzed reactions in the gas phase, with numerous reactions in the gas phase having been investigated on a multitude of surfaces. However, in situ SFG characterization of catalysis at the solid-liquid interface has yet to be thoroughly pursued despite the broad interest in the use of heterogeneous catalysts in the liquid phase as replacements for homogeneous counterparts. This work describes an attempt to move in that direction, applying SFG to study the solid-liquid interface under conditions of catalytic alcohol oxidation on platinum.

  4. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM).

    Science.gov (United States)

    Wu, Heng-Liang; Tong, Yujin; Peng, Qiling; Li, Na; Ye, Shen

    2016-01-21

    The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and per-protonated monolayers, i.e., DPPC-d75/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational ordering of the supported bilayer does not decrease (even slightly increases) during the phase transition process. The conformational defects in the bilayer can be removed after the complete melting process. The phase transition enthalpy for the bottom leaflet was found to be approximately three times greater than that for the top leaflet, indicating a strong interaction of the lipids with the substrate. The present SFG and AFM observations revealed similar temperature dependent profiles. Based on these results, the temperature-induced structural changes in the supported lipid bilayer during its phase transition process are discussed in comparison with previous studies.

  5. Water Orientation at Ceramide/Water Interfaces Studied by Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy and Molecular Dynamics Simulation

    KAUST Repository

    Adhikari, Aniruddha

    2016-10-10

    Lipid/water interaction is essential for many biological processes. The water structure at the nonionic lipid interface remains little known, and there is no scope of a priori prediction of water orientation at nonionic interfaces, either. Here, we report our study combining advanced nonlinear spectroscopy and molecular dynamics simulation on the water orientation at the ceramide/water interface. We measured χ spectrum in the OH stretch region of ceramide/isotopically diluted water interface using heterodyne-detected vibrational sum-frequency generation spectroscopy and found that the interfacial water prefers an overall hydrogen-up orientation. Molecular dynamics simulation indicates that this preferred hydrogen-up orientation of water is determined by a delicate balance between hydrogen-up and hydrogen-down orientation induced by lipid-water and intralipid hydrogen bonds. This mechanism also suggests that water orientation at neutral lipid interfaces depends highly on the chemical structure of the lipid headgroup, in contrast to the charged lipid interfaces where the net water orientation is determined solely by the charge of the lipid headgroup.

  6. Low energy electron diffraction (LEED) and sum frequency generation (SFG) vibrational spectroscopy studies of solid-vacuum, solid-air and solid-liquid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoffer, Saskia [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    Electron based surface probing techniques can provide detailed information about surface structure or chemical composition in vacuum environments. The development of new surface techniques has made possible in situ molecular level studies of solid-gas interfaces and more recently, solid-liquid interfaces. The aim of this dissertation is two-fold. First, by using novel sample preparation, Low Energy Electron Diffraction (LEED) and other traditional ultra high vacuum (UHV) techniques are shown to provide new information on the insulator/vacuum interface. The surface structure of the classic insulator NaCl has been determined using these methods. Second, using sum frequency generation (SFG) surface specific vibrational spectroscopy studies were performed on both the biopolymer/air and electrode/electrolyte interfaces. The surface structure and composition of polyetherurethane-silicone copolymers were determined in air using SFG, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). SFG studies of the electrode (platinum, gold and copper)/electrolyte interface were performed as a function of applied potential in an electrochemical cell.

  7. Surface structures of an amphiphilic tri-block copolymer in air and in water probed using sum frequency generation vibrational spectroscopy.

    Science.gov (United States)

    Kristalyn, Cornelius B; Lu, Xiaolin; Weinman, Craig J; Ober, Christopher K; Kramer, Edward J; Chen, Zhan

    2010-07-06

    Sum frequency generation (SFG) vibrational spectroscopy has been applied to investigate surface structures of an amphiphilic surface-active block copolymer (SABC) film deposited on a CaF(2) substrate, in air and in water in situ. Developed as a surface-active component of an antifouling coating for marine applications, this amphiphilic triblock copolymer contains both hydrophobic fluorinated alkyl groups as well as hydrophilic ethoxy groups. It was found that surface structures of the copolymer film in air and in water cannot be probed directly using the SFG experimental geometry we adopted because SFG signals can be contributed from the polymer/air (or polymer/water) interface as well as the buried polymer/CaF(2) substrate interface. Using polymer films with varied thicknesses, structural information about the polymer surfaces in air and in water can be deduced from the detected SFG signals. With SFG, surface restructuring of this polymer has been observed in water, especially the methyl and methylene groups change orientations upon contact with water. However, the hydrophobic fluoroalkyl group was present on the surface in both air and water, and we believe that it was held near the surface in water by its neighboring ethoxy groups.

  8. Red-Shifting versus Blue-Shifting Hydrogen Bonds: Perspective from Ab Initio Valence Bond Theory.

    Science.gov (United States)

    Chang, Xin; Zhang, Yang; Weng, Xinzhen; Su, Peifeng; Wu, Wei; Mo, Yirong

    2016-05-05

    Both proper, red-shifting and improper, blue-shifting hydrogen bonds have been well-recognized with enormous experimental and computational studies. The current consensus is that there is no difference in nature between these two kinds of hydrogen bonds, where the electrostatic interaction dominates. Since most if not all the computational studies are based on molecular orbital theory, it would be interesting to gain insight into the hydrogen bonds with modern valence bond (VB) theory. In this work, we performed ab initio VBSCF computations on a series of hydrogen-bonding systems, where the sole hydrogen bond donor CF3H interacts with ten hydrogen bond acceptors Y (═NH2CH3, NH3, NH2Cl, OH(-), H2O, CH3OH, (CH3)2O, F(-), HF, or CH3F). This series includes four red-shifting and six blue-shifting hydrogen bonds. Consistent with existing findings in literature, VB-based energy decomposition analyses show that electrostatic interaction plays the dominating role and polarization plays the secondary role in all these hydrogen-bonding systems, and the charge transfer interaction, which denotes the hyperconjugation effect, contributes only slightly to the total interaction energy. As VB theory describes any real chemical bond in terms of pure covalent and ionic structures, our fragment interaction analysis reveals that with the approaching of a hydrogen bond acceptor Y, the covalent state of the F3C-H bond tends to blue-shift, due to the strong repulsion between the hydrogen atom and Y. In contrast, the ionic state F3C(-) H(+) leads to the red-shifting of the C-H vibrational frequency, owing to the attraction between the proton and Y. Thus, the relative weights of the covalent and ionic structures essentially determine the direction of frequency change. Indeed, we find the correlation between the structural weights and vibrational frequency changes.

  9. Hydrogen Bonding and Vibrational Spectroscopy: A Theoretical Study

    Science.gov (United States)

    Chaban, Galina M.

    2005-01-01

    Effects of hydrogen bonding on vibrational spectra are studied for several hydrogen-bonded complexes, in which hydrogen bonding ranges from weak (25 kcal/mol). The systems studied include complexes of inorganic acids and salts with water and ammonia, as well as complexes of several organic molecules (nitriles and amino acids) with water. Since anharmonic effects are very strong in hydrogen-bonded systems, anharmonic vibrational frequencies and infrared intensities are computed using the correlation-corrected vibrational self-consistent field (CC-VSCF) method with ab initio potential surfaces at the MP2 and CCSD(T) levels. The most common spectral effects induced by hydrogen bonding are red shifts of stretching vibrational frequencies ranging from approx.200/cm to over 2000/cm and significant increases of infrared intensities for those bonds that participate in hydrogen bonding. However, some systems (e.g. nitrile-water complexes) exhibit shifts in the opposite direction (to the blue) upon formation of hydrogen bonds.

  10. Dependence on the electric power of the immersion-angle dependence of the resonant-frequency shift of a quartz crystal microbalance in a liquid.

    Science.gov (United States)

    Yoshimoto, Minoru; Maruyama, Yasuhiro; Kurosawa, Shigeru; Kanazawa, K Keiji

    2007-04-18

    We have investigated the immersion-angle dependence of the series resonant-frequency shift, DeltaF, of the quartz crystal microbalance, QCM, in a Newtonian liquid from the point of view of the supplied electric power level. In the low electric power levels, the immersion-angle dependence and the transition phenomenon of the DeltaF are observed. However, when the higher electric power levels are supplied to the QCM, the region of the transition phenomenon of the DeltaF decreases rapidly with an increase in the electric power level and disappears above 1.5 dBm. That is, above 1.5 dBm, the DeltaF values have only the values of 90 degrees immersion angle in all immersion angles. We suggest that the electric power is very important factor for the DeltaF in a liquid.

  11. Effects of 8 weeks of vibration training at different frequencies (1 or 15 Hz) in senior sportsmen on torque and force development and of 1 year of training on muscle fibers.

    Science.gov (United States)

    Kern, H; Kovarik, J; Franz, C; Vogelauer, M; Löfler, S; Sarabon, N; Grim-Stieger, M; Biral, D; Adami, N; Carraro, U; Zampieri, S; Hofer, Ch

    2010-02-01

    To examine the effects of 8 weeks of vibration training at different frequencies (1 and 15 Hz) on maximal isometric torque and force development in senior sportsmen, and of 1 year of heavy-resistance and vibration trainings on muscle fibers. Seven healthy senior sportsmen (mean age: 69.0 +/- 5.4 years) performed an 8 weeks of strength training of knee extensors. Vibrations were applied vertically to the axis of movement during training. One leg of each subject was trained at a frequency of 1 Hz, while the other leg was trained at 15 Hz. Measures of isometric peak torque (at knee-angles of 60, 90 and 120 degrees ) and force development were recorded before and after training. Four sportsmen continued a year-long heavy-resistance training adding every second week a session of vibration training. After training, muscle biopsies were harvested from their quadriceps muscles and used for structural analyses. Morphometry of muscle fibers was performed by light microscopy. Immunohistochemistry using anti-MHCemb and anti-N-CAM antibodies was performed to measure potential muscle damage. Data from muscle morphometry were compared to that of a series of vastus lateralis biopsies harvested from 12 young sportsmen and four healthy elderly. Our results showed a significant increase in isometric peak torque at both 1 and 15 Hz vibration frequency in all three measured angles of the knee. There was no significant difference between the two frequencies, but we could find a higher increase in percentage of maximum power after the 1 Hz training. The results of force development showed a slight increase at the 1 Hz training in measured time frames from 0 to 50 and 200 ms, without statistical significance. A trend to significance was found at the 1 Hz training at the time window up to 200 ms. The 15 Hz training showed no significant changes of force development. Muscle biopsies show that the muscles of these well trained senior sportsmen contain muscle fibers which are 35% larger than

  12. Quality Structures, Vibrational Frequencies, and Thermochemistry of the Products of Reaction of BrHg(•) with NO2, HO2, ClO, BrO, and IO.

    Science.gov (United States)

    Jiao, Yuge; Dibble, Theodore S

    2015-10-22

    Quantum chemical calculations have been carried out to investigate the structures, vibrational frequencies, and thermochemistry of the products of BrHg(•) reactions with atmospherically abundant radicals Y(•) (Y = NO2, HO2, ClO, BrO, or IO). The coupled cluster method with single and double excitations (CCSD), combined with relativistic effective core potentials, is used to determine the equilibrium geometries and harmonic vibrational frequencies of BrHgY species. The BrHg-Y bond energies are refined using CCSD with a noniterative estimate of the triple excitations (CCSD(T)) combined with core-valence correlation consistent basis sets. We also assess the performances of various DFT methods for calculating molecular structures and vibrational frequencies of BrHgY species. We attempted to estimate spin-orbit coupling effects on bond energies computed by comparing results from standard and two-component spin-orbit density functional theory (DFT) but obtained unphysical results. The results of the present work will provide guidance for future studies of the halogen-initiated chemistry of mercury.

  13. Inter-echo variance as a weighting factor for multi-channel combination in multi-echo acquisition for local frequency shift mapping.

    Science.gov (United States)

    Liu, Junmin; Rudko, David A; Gati, Joseph S; Menon, Ravi S; Drangova, Maria

    2015-04-01

    To develop and evaluate a local frequency shift (LFS) mapping method specifically designed for multi-echo acquisitions and multi-channel receive coils. The proposed method uses the pixel-by-pixel inter-echo variance (IEV) as a weighting factor during channel-combination. Five healthy volunteers were scanned at 7 T. The IEV-weighted method was quantitatively compared to established (adaptive and Hermitian product) channel-combination methods with respect to IEV of LFS over the entire brain. In all experiments, the IEV-weighted method generated LFS maps free of artifacts caused by unwrapping errors. Based on measurements of the inter-echo frequency variance throughout the whole brain, the IEV-weighted method produced the lowest variation and the best contrast at the edge of the brain. The primary finding of the present study is that accurate LFS maps are achievable if the data from each channel is processed independently prior to combination followed by a weighted combination using IEV as the weighting term. The software is freely available to the scientific community. © 2014 Wiley Periodicals, Inc.

  14. Rabi-vibronic resonance with large number of vibrational quanta

    OpenAIRE

    Glenn, R.; Raikh, M. E.

    2011-01-01

    We study theoretically the Rabi oscillations of a resonantly driven two-level system linearly coupled to a harmonic oscillator (vibrational mode) with frequency, \\omega_0. We show that for weak coupling, \\omega_p \\ll \\omega_0, where \\omega_p is the polaronic shift, Rabi oscillations are strongly modified in the vicinity of the Rabi-vibronic resonance \\Omega_R = \\omega_0, where \\Omega_R is the Rabi frequency. The width of the resonance is (\\Omega_R-\\omega_0) \\sim \\omega_p^{2/3} \\omega_0^{1/3} ...

  15. Damping element for reducing the vibration of an airfoil

    Science.gov (United States)

    Campbell, Christian X; Marra, John J

    2013-11-12

    An airfoil (10) is provided with a tip (12) having an opening (14) to a center channel (24). A damping element (16) is inserted within the opening of the center channel, to reduce an induced vibration of the airfoil. The mass of the damping element, a spring constant of the damping element within the center channel, and/or a mounting location (58) of the damping element within the center channel may be adjustably varied, to shift a resonance frequency of the airfoil outside a natural operating frequency of the airfoil.

  16. Size variation of infrared vibrational spectra from molecules to hydrogenated diamond nanocrystals: a density functional theory study

    Directory of Open Access Journals (Sweden)

    Mudar A. Abdulsattar

    2013-04-01

    Full Text Available Infrared spectra of hydrogenated diamond nanocrystals of one nanometer length are calculated by ab initio methods. Positions of atoms are optimized via density functional theory at the level of the generalized gradient approximation of Perdew, Burke and Ernzerhof (PBE using 3-21G basis states. The frequencies in the vibrational spectrum are analyzed against reduced masses, force constants and intensities of vibration. The spectrum can be divided into two regions depending on the properties of the vibrations or the gap separating them. In the first region, results show good matching to several experimentally obtained lines. The 500 cm−1 broad-peak acoustical branch region is characterized by pure C–C vibrations. The optical branch is centered at 1185 cm−1. Calculations show that several C–C vibrations are mixed with some C–H vibrations in the first region. In the second region the matching also extends to C–H vibration frequencies that include different modes such as symmetric, asymmetric, wagging, scissor, rocking and twisting modes. In order to complete the picture of the size dependence of the vibrational spectra, we analyzed the spectra of ethane and adamantane. The present analysis shows that acoustical and optical branches in diamond nanocrystals approach each other and collapse at 963 cm−1 in ethane. Variation of the highest reduced-mass-mode C–C vibrations from 1332 cm−1 of bulk diamond to 963 cm−1 for ethane (red shift is shown. The analysis also shows the variation of the radial breathing mode from 0 cm−1 of bulk diamond to 963 cm−1 for ethane (blue shift. These variations compare well with experiment. Experimentally, the above-mentioned modes appear shifted from their exact positions due to overlap with neighboring modes.

  17. Force illusions and drifts observed during muscle vibration.

    Science.gov (United States)

    Reschechtko, Sasha; Cuadra, Cristian; Latash, Mark L

    2018-01-01

    We explored predictions of a scheme that views position and force perception as a result of measuring proprioceptive signals within a reference frame set by ongoing efferent process. In particular, this hypothesis predicts force illusions caused by muscle vibration and mediated via changes in both afferent and efferent components of kinesthesia. Healthy subjects performed accurate steady force production tasks by pressing with the four fingers of one hand (the task hand) on individual force sensors with and without visual feedback. At various times during the trials, subjects matched the perceived force using the other hand. High-frequency vibration was applied to one or both of the forearms (over the hand and finger extensors). Without visual feedback, subjects showed a drop in the task hand force, which was significantly smaller under the vibration of that forearm. Force production by the matching hand was consistently higher than that of the task hand. Vibrating one of the forearms affected the matching hand in a manner consistent with the perception of higher magnitude of force produced by the vibrated hand. The findings were consistent between the dominant and nondominant hands. The effects of vibration on both force drift and force mismatching suggest that vibration led to shifts in both signals from proprioceptors and the efferent component of perception, the referent coordinate and/or coactivation command. The observations fit the hypothesis on combined perception of kinematic-kinetic variables with little specificity of different groups of peripheral receptors that all contribute to perception of forces and coordinates. NEW & NOTEWORTHY We show that vibration of hand/finger extensors produces consistent errors in finger force perception. Without visual feedback, finger force drifted to lower values without a drift in the matching force produced by the other hand; hand extensor vibration led to smaller finger force drift. The findings fit the scheme with

  18. Acute effects of vibration from a chipping hammer and a grinder on the hand-arm system.

    Science.gov (United States)

    Kihlberg, S; Attebrant, M; Gemne, G; Kjellberg, A

    1995-11-01

    The purpose of this study was to compare various effects on the hand-arm system of vibration exposure from a chipping hammer and a grinder with the same frequency weighted acceleration. Grip and push forces were measured and monitored during the exposure. The various effects were: muscle activity (measured with surface electrodes), discomfort ratings for different parts of the hand-arm system (made during and after exposure), and vibration perception threshold (for 10 minutes before and 10 minutes after the exposure). No increase in muscle activity due to exposure to vibration was found in the hand muscle studied. In the forearm, conversely, there was an increase in both muscle studied. For the upper arm the muscle activity only increased when exposed to impact vibration. Subjective ratings in the hand and shift in vibration perception threshold were effected more by the grinder than the hammer exposure. These results show that the reaction of the hand-arm system to vibration varies with frequency quantitatively as well as qualitatively. They do not support the notion that one single frequency weighted curve would be valid for the different health effects of hand-arm vibration (vascular, musculoskeletal, neurological, and psychophysiological).

  19. The origins of vibration theory

    Science.gov (United States)

    Dimarogonas, A. D.

    1990-07-01

    The Ionian School of natural philosophy introduced the scientific method of dealing with natural phenomena and the rigorous proofs for abstract propositions. Vibration theory was initiated by the Pythagoreans in the fifth century BC, in association with the theory of music and the theory of acoustics. They observed the natural frequency of vibrating systems and proved that it is a system property and that it does not depend on the excitation. Pythagoreans determined the fundamental natural frequencies of several simple systems, such as vibrating strings, pipes, vessels and circular plates. Aristoteles and the Peripatetic School founded mechanics and developed a fundamental understanding of statics and dynamics. In Alexandrian times there were substantial engineering developments in the field of vibration. The pendulum as a vibration, and probably time, measuring device was known in antiquity, and was further developed by the end of the first millennium AD.

  20. A new isolator for vibration control

    Science.gov (United States)

    Behrooz, Majid; Sutrisno, Joko; Wang, Xiaojie; Fyda, Robert; Fuchs, Alan; Gordaninejad, Faramarz

    2011-03-01

    This study presents the feasibility of a new variable stiffness and damping isolator (VSDI) in an integrated vibratory system. The integrated system comprised of two VSDIs, a connecting plate and a mass. The proposed VSDI consists of a traditional steel-rubber vibration absorber, as the passive element, and a magneto-rheological elastomer (MRE), with a controllable (or variable) stiffness and damping, as the semi-active element. MREs' stiffness and damping properties can be altered by a magnetic field. Dynamic testing on this integrated system has been performed to investigate the effectiveness of the VSDIs for vibration control. Experimental results show significant shift in natural frequency, when activating the VSDIs. Transmissibility and natural frequency of the integrated system are obtained from properties of single device. The experimental and predicted results show good agreement between the values of the natural frequency of the system at both off and on states. However, system damping predictions are different from experimental results. This might be due to unforeseen effects of pre-stressed MREs and nonlinear material properties.

  1. Non-linear vibrational modes in biomolecules: A periodic orbits description

    Energy Technology Data Exchange (ETDEWEB)

    Kampanarakis, Alexandros [Department of Chemistry, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (FORTH), Vasilika Vouton, Heraklion 71110, Crete (Greece); Farantos, Stavros C., E-mail: farantos@iesl.forth.gr [Department of Chemistry, University of Crete, and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (FORTH), Vasilika Vouton, Heraklion 71110, Crete (Greece); Daskalakis, Vangelis; Varotsis, Constantinos [Department of Environmental Science and Technology, Cyprus University of Technology, 31 Archbishop Kyprianos St., P.O. Box 50329, 3603 Lemesos (Cyprus)

    2012-05-03

    Graphical abstract: Vibrational frequency shifts in Fe{sup IV} = O species of the active site of cytochrome c oxidase are attributed to changes in the surrounding Coulomb field. Periodic orbits analysis assists to find the most anharmonic modes in model biomolecules. Highlights: Black-Right-Pointing-Pointer Periodic orbits are extended to multidimensional potentials of biomolecules. Black-Right-Pointing-Pointer Highly anharmonic vibrational modes and center-saddle bifurcations are detected. Black-Right-Pointing-Pointer Vibrational frequencies shifts in Oxoferryl species of CcO are observed. - Abstract: The vibrational harmonic normal modes of a molecule, which are valid at energies close to an equilibrium point (a minimum, maximum or saddle of the potential energy surface), are extended by periodic orbits to high energies where anharmonicity and coupling of the degrees of freedom are significant. In this way the assignment of the spectra, and thus the extraction of dynamics in highly excited molecules, can be obtained. New vibrational modes emanating from bifurcations of periodic orbits and long living localized trajectories signal the birth and localization of new quantum states. In this article we review and further study non-linear vibrational modes for model biomolecules such as alanine dipeptide and the active site in the oxoferryl oxidation state of the enzyme cytochrome c oxidase. We locate periodic orbits which exhibit high anhamonicity and lead to center-saddle bifurcations. These modes are associated to an isomerization process in alanine dipeptide and to frequency shifts in the oxoferryl observed by modifying the Coulomb field around the Imidazole-Fe{sup IV} = O species.

  2. Frequency and damping ratio assessment of high-rise buildings using an Automatic Model-Based Approach applied to real-world ambient vibration recordings

    Science.gov (United States)

    Nasser, Fatima; Li, Zhongyang; Gueguen, Philippe; Martin, Nadine

    2016-06-01

    This paper deals with the application of the Automatic Model-Based Approach (AMBA) over actual buildings subjected to real-world ambient vibrations. In a previous paper, AMBA was developed with the aim of automating the estimation process of the modal parameters and minimizing the estimation error, especially that of the damping ratio. It is applicable over a single-channel record, has no parameters to be set, and no manual initialization phase. The results presented in this paper should be regarded as further documentation of the approach over real-world ambient vibration signals.

  3. Resonant vibration control of rotating beams

    DEFF Research Database (Denmark)

    Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker

    2011-01-01

    Rotatingstructures,like e.g.wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor–actuator system, governed by a resonant controller. The theory is here demonstrated...... modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency....

  4. Efficient cooling of quantized vibrations using a four-level configuration

    Science.gov (United States)

    Yan, Lei-Lei; Zhang, Jian-Qi; Zhang, Shuo; Feng, Mang

    2016-12-01

    Cooling vibrational degrees of freedom down to ground states is essential to observation of quantum properties of systems with mechanical vibration. We propose two cooling schemes employing four internal levels of the systems, which achieve the ground-state cooling in an efficient fashion by completely deleting the carrier and first-order blue-sideband transitions. The schemes, based on quantum interference and Stark-shift gates, are robust to fluctuations of laser intensity and frequency. The feasibility of the schemes is justified using current laboratory technology. In practice, our proposal readily applies to a nanodiamond nitrogen-vacancy center levitated in an optical trap or attached to a cantilever.

  5. Tissue vibration in prolonged running.

    Science.gov (United States)

    Friesenbichler, Bernd; Stirling, Lisa M; Federolf, Peter; Nigg, Benno M

    2011-01-04

    The impact force in heel-toe running initiates vibrations of soft-tissue compartments of the leg that are heavily dampened by muscle activity. This study investigated if the damping and frequency of these soft-tissue vibrations are affected by fatigue, which was categorized by the time into an exhaustive exercise. The hypotheses were tested that (H1) the vibration intensity of the triceps surae increases with increasing fatigue and (H2) the vibration frequency of the triceps surae decreases with increasing fatigue. Tissue vibrations of the triceps surae were measured with tri-axial accelerometers in 10 subjects during a run towards exhaustion. The frequency content was quantified with power spectra and wavelet analysis. Maxima of local vibration intensities were compared between the non-fatigued and fatigued states of all subjects. In axial (i.e. parallel to the tibia) and medio-lateral direction, most local maxima increased with fatigue (supporting the first hypothesis). In anterior-posterior direction no systematic changes were found. Vibration frequency was minimally affected by fatigue and frequency changes did not occur systematically, which requires the rejection of the second hypothesis. Relative to heel-strike, the maximum vibration intensity occurred significantly later in the fatigued condition in all three directions. With fatigue, the soft tissue of the triceps surae oscillated for an extended duration at increased vibration magnitudes, possibly due to the effects of fatigue on type II muscle fibers. Thus, the protective mechanism of muscle tuning seems to be reduced in a fatigued muscle and the risk of potential harm to the tissue may increase. Copyright © 2010 Elsevier Ltd. All rights reserved.

  6. Optical properties of a vibrationally modulated solid state Mott insulator.

    Science.gov (United States)

    Kaiser, S; Clark, S R; Nicoletti, D; Cotugno, G; Tobey, R I; Dean, N; Lupi, S; Okamoto, H; Hasegawa, T; Jaksch, D; Cavalleri, A

    2014-01-22

    Optical pulses at THz and mid-infrared frequencies tuned to specific vibrational resonances modulate the lattice along chosen normal mode coordinates. In this way, solids can be switched between competing electronic phases and new states are created. Here, we use vibrational modulation to make electronic interactions (Hubbard-U) in Mott-insulator time dependent. Mid-infrared optical pulses excite localized molecular vibrations in ET-F2TCNQ, a prototypical one-dimensional Mott-insulator. A broadband ultrafast probe interrogates the resulting optical spectrum between THz and visible frequencies. A red-shifted charge-transfer resonance is observed, consistent with a time-averaged reduction of the electronic correlation strength U. Secondly, a sideband manifold inside of the Mott-gap appears, resulting from a periodically modulated U. The response is compared to computations based on a quantum-modulated dynamic Hubbard model. Heuristic fitting suggests asymmetric holon-doublon coupling to the molecules and that electron double-occupancies strongly squeeze the vibrational mode.

  7. Effect of combining traction and vibration on back muscles, heart rate and blood pressure.

    Science.gov (United States)

    Wang, Lizhen; Zhao, Meiya; Ma, Jian; Tian, Shan; Xiang, Pin; Yao, Wei; Fan, Yubo

    2014-11-01

    Eighty-five percent of the population has experienced low back pain (LBP), which may result in decreasing muscle strength and endurance, functional capacity of the spine, and so on. Traction and vibration are commonly used to relieve the low back pain. The effect of the combing traction and vibration on back muscles, heart rate (HR) and blood pressure (BP) was investigated in this study. Thirty healthy subjects participated in 12 trials lying supine on the spine-combing bed with different tilt angle (0°, 10°, 20° and 30°) and vibration modes (along with the sagittal and coronal axis with 0 Hz, 2 Hz and 12 Hz separately). EMG was recorded during each trial. Power spectral frequency analysis was applied to evaluate muscle fatigue by the shift of median power frequency (MPF). Pulse pressure (PP) was calculated from BP. HR and PP were used to estimate the effect of the combination of traction and vibration on the cardio-vascular system. It was shown that vibration could increase HR and decrease PP. The combination of traction and vibration (2 Hz vibration along Z-axis and 12 Hz vibration along Y-axis) had no significant effect on the cardio-vascular system. The MPF of lumbar erector spinae (LES) and upper trapezius (UT) decreased significantly when the angle reached 20° under the condition of 2 Hz vibration along Z-axis compared with it of 0°. Furthermore, the MPF also decreased significantly compared with it of static mode at 20° for LES and at 30° for UT. However at 12 Hz vibration along Y-axis, the MPF had significant increase when the angle reached 20° in LES and 30° in UT compared to 0°. For LES, the MPF also had significant difference when the angle was increased from 10° to 20°. Therefore, combining 2 Hz vibration along Z-axis and traction (tilt angles that less than 20°) may to reduce muscle fatigue both for LES and UT compared with either vibration or traction alone. The combination of 12 Hz vibration along Y-axis and traction (tilt angles

  8. Hydrogen Bonds and the Vibrational Modes of Water at Interfaces: ab-initio Molecular Dynamics meets Neutron Scattering

    Science.gov (United States)

    Kumar, Nitin; Neogi, Sanghamitra; Kent, Paul; Bandura, Andrei; Kubicki, James; Wesolowski, David; Sofo, Jorge

    2008-03-01

    We study the vibrational density of states (VDOS) of a thin water layer on the rutile (110) surface. The VDOS is obtained from the velocity-velocity autocorrelation function calculated from trajectories of large scale ab-initio molecular dynamics simulations. The rutile surface induces a shift to lower frequencies of the stretching modes with respect to pure water. The water vapor surface shows a peak at the vibrational frequency of free hydroxyls. Overall, the average stretching mode vibrational frequency increases with decreasing hydrogen bonding density. This density depends strongly on temperature. The water dissociation percentage at the surface can be correlated with the ratio between the weights of the stretching and the bending modes. Our results are in good agreement with inelastic neutron scattering measurements done on wet titania nanoparticles.

  9. A novel vibration sensor based on phase grating interferometry

    Science.gov (United States)

    Li, Qian; Liu, Xiaojun; Zhao, Li; Lei, Zili; Lu, Zhen; Guo, Lei

    2017-05-01

    Vibration sensors with high accuracy and reliability are needed urgently for vibration measurement. In this paper a vibration sensor with nanometer resolution is developed. This sensor is based on the principle of phase grating interference for displacement measurement and spatial polarization phase-shift interference technology, and photoelectric counting and A/D signal subdivision are adopted for vibration data output. A vibration measurement system consisting of vibration actuator and displacement adjusting device has been designed to test the vibration sensor. The high resolution and high reliability of the sensor are verified through a series of comparison experiments with Doppler interferometer.

  10. Whole-body vibration dosage alters leg blood flow

    NARCIS (Netherlands)

    Lythgo, Noel; Eser, Prisca; de Groot, Patricia; Galea, Mary

    The effect of whole-body vibration dosage on leg blood flow was investigated. Nine healthy young adult males completed a set of 14 random vibration and non-vibration exercise bouts whilst squatting on a Galileo 900 plate. Six vibration frequencies ranging from 5 to 30 Hz (5 Hz increments) were used

  11. Vibrational probes and determinants of the S = 0 ⇌ S = 2 spin crossover in five-coordinate [Fe(TPP)(CN)]-.

    Science.gov (United States)

    Li, Jianfeng; Peng, Qian; Barabanschikov, Alexander; Pavlik, Jeffrey W; Alp, E Ercan; Sturhahn, Wolfgang; Zhao, Jiyong; Sage, J Timothy; Scheidt, W Robert

    2012-11-05

    The low-frequency vibrational characterization of the spin-crossover complex, five-coordinate cyano(tetraphenylporphyrinato)iron(II), [Fe(TPP)(CN)](-), is reported. Nuclear resonance vibrational spectroscopy has been used to measure all low-frequency vibrations involving iron at several temperatures; this yields vibrational spectra of both the low- (S = 0) and high-spin (S = 2) states. Multitemperature oriented single-crystal measurements facilitate assignments of the vibrational character of all modes and are consistent with the DFT-predicted spectra. The availability of the entire iron vibrational spectrum allows for the complete correlation of the modes between the two spin states. These data demonstrate that not only do the frequencies of the vibrations shift to lower values for the high-spin species as would be expected owing to the weaker bonds in the high-spin state, but also the mixing of iron modes with ligand modes changes substantially. Diagrams illustrating the changing character of the modes and their correlation are given. The reduced iron-ligand frequencies are the primary factor in the entropic stabilization of the high-spin state responsible for the spin crossover.

  12. Hybrid approaches to magnetic resonance thermometry using the proton resonance frequency shift and the spin-lattice relaxation time T1

    Science.gov (United States)

    Diakite, Mahamadou

    Minimally invasive thermal therapy under Magnetic Resonance Imaging (MRI) guidance is becoming popular with several applications in the process of getting FDA approval. The ability to determine in near real-time the temperature map of a tumor and its surrounding tissue makes MR thermometry very attractive and well suited for thermal treatment. The proton resonance frequency shift (PRF) is currently the gold standard method for temperature monitoring using MRI. However, its incapacity to measure temperature in fatty tissue limits the scope of its applicability. The spin lattice relaxation time T1, on the other hand, has shown good temperature sensitivity and works well in all types of tissues. In this dissertation, we have addressed a number of challenges currently affecting MRI thermometry. A non-CPMG Turbo Spin Echo (TSE) sequence has been implemented to monitor the temperature rise due to the high RF power deposition inherent to this sequence at high field (3T and higher). This new implementation allows TSE sequences to be used safely without altering their high contrast properties which make them appealing in clinical settings. Tissue damage assessment during thermal therapy is critical for the safety of the patient. We have developed a new hybrid PRF-T1 sequence that has the capability to provide simultaneously in near real-time the temperature map and T1 information, which is a good indication of the state of the tissue. The simplicity and the real-time capability of the newly developed sequence make it an ideal tool for tissue damage assessment. Temperature monitoring during thermal therapy in organs with large fat content have been hindered by the lack of an MRI thermometry method that can provide simultaneous temperature in fat and aqueous tissue. A new sequence and acquisition scheme have been developed to address this issue. In sum, this dissertation proposed several pulse sequence implementation techniques and an acquisition scheme to overcome some of

  13. Monitoring vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Tiryaki, B. [Hacettepe University (Turkey). Dept. of Mining Engineering

    2003-12-01

    The paper examines the prediction and optimisation of machine vibrations in longwall shearers. Underground studies were carried out at the Middle Anatolian Lignite Mine, between 1993 and 1997. Several shearer drums with different pick lacing arrangements were designed and tested on double-ended ranging longwall shearers employed at the mine. A computer program called the Vibration Analysis Program (VAP) was developed for analysing machine vibrations in longwall shearers. Shearer drums that were tested underground, as well as some provided by leading manufacturers, were analyzed using these programs. The results of the experiments and computer analyses are given in the article. 4 refs., 9 figs.

  14. Vibration characteristics of casing string under the exciting force of an electric vibrator

    Directory of Open Access Journals (Sweden)

    Yiyong Yin

    2017-11-01

    Full Text Available Vibration cementing is a new technique that can significantly improve the bond strength of cementing interface. To popularize this technique, it is necessary to solve the key problem of how to make cementing string generate downhole radial vibration in the WOC stage. For this purpose, an electric vibrator was developed. With this vibrator, electric energy is converted into mechanical energy by means of a high-temperature motor vibration unit. The motor vibration unit rotates the eccentric block through an output shaft to generate an exciting source, which produces an axial-rotating exciting force at the bottom of the casing string. Then, the vibration characteristics of vertical well casing string under the exciting force were analyzed by using the principal coordinate analysis method, and the response model of casing string to an electric vibrator was developed. Finally, the effects of casing string length, exciting force and vibration frequency on the vibration amplitude at the lowermost of the casing string were analyzed based on a certain casing program. It is indicated that the casing string length and the square of vibration frequency are inversely proportional to the vibration amplitude at the lowermost of the casing string, and the exciting force is proportional to the vibration amplitude at the lowermost of the casing string. These research results provide a theoretical support for the application of vibration cementing technology to the cementing sites with different requirements on well depth and amplitude.

  15. Davisson-Germer Prize Talk: Surface vibrations of adsorbates on Si(111): From small clusters to infinite lattices

    Science.gov (United States)

    Raghavachari, Krishnan

    2009-03-01

    Organic functionalization of semiconductor surfaces is a growing research area that offers the possibility of molecular level control of surface features and tailored electronic properties. In this work, quantum chemical cluster calculations are used in conjunction with surface vibrational spectroscopy to determine the structures of functionalized Si(111) surfaces. Interestingly, the interpretation of these spectra even for simple adsorbates is not straightforward. In the limit of high coverage, most calculations using small cluster models lack the long range coupling of the real surface that is required to make definitive assignments. In order to understand the relationship between clusters and infinite periodic vibrations, we have investigated the geometries and harmonic vibrational frequencies of the methyl, acetylenyl, methylacetylenyl, hydrogen, deuterium and chlorine functionalized Si(111) surfaces. From a careful analysis of these systems, we have derived a technique where the collective vibrational modes corresponding to the vibrations of the infinite periodic system can be derived from relatively small cluster models. The calculated frequencies are in good agreement with available experimental values and yield novel insights about the coupling between low frequency adsorbate frequencies and surface phonons. The efficacy of this approach for surfaces of varying adsorbate coverage and the prediction of novel frequency shifts will be discussed along with more complex systems.

  16. Support Effects in Catalysis Studied by in-situ Sum Frequency Generation Vibrational Spectroscopy and in-situ X-Ray Spectroscopies

    Science.gov (United States)

    Kennedy, Griffin John

    Kinetic measurements are paired with in-situ spectroscopic characterization tools to investigate colloidally based, supported Pt catalytic model systems in order to elucidate the mechanisms by which metal and support work in tandem to dictate activity and selectivity. The results demonstrate oxide support materials, while inactive in absence of Pt nanoparticles, possess unique active sites for the selective conversion of gas phase molecules when paired with an active metal catalyst. In order to establish a paradigm for metal-support interactions using colloidally synthesized Pt nanoparticles the ability of the organic capping agent to inhibit reactivity and interaction with the support must first be assessed. Pt nanoparticles capped by poly(vinylpyrrolidone) (PVP), and those from which the PVP is removed by UV light exposure, are investigated for two reactions, the hydrogenation of ethylene and the oxidation of methanol. It is shown that prior to PVP removal the particles are moderately active for both reactions. Following removal, the activity for the two reactions diverges, the ethylene hydrogenation rate increases 10-fold, while the methanol oxidation rate decreases 3-fold. To better understand this effect the capping agent prior to, and the residual carbon remaining after UV treatment are probed by sum frequency generation vibrational spectroscopy. Prior to removal no major differences are observed when the particles are exposed to alternating H2 and O2 environments. When the PVP is removed, carbonaceous fragments remain on the surface that dynamically restructure in H2 and O2. These fragments create a tightly bound shell in an oxygen environment and a porous coating of hydrogenated carbon in the hydrogen environment. Reaction rate measurements of thermally cleaned PVP and oleic acid capped particles show this effect to be independent of cleaning method or capping agent. In all this demonstrates the ability of the capping agent to mediate nanoparticle catalysis

  17. Blade Vibration Measurement System

    Science.gov (United States)

    Platt, Michael J.

    2014-01-01

    The Phase I project successfully demonstrated that an advanced noncontacting stress measurement system (NSMS) could improve classification of blade vibration response in terms of mistuning and closely spaced modes. The Phase II work confirmed the microwave sensor design process, modified the sensor so it is compatible as an upgrade to existing NSMS, and improved and finalized the NSMS software. The result will be stand-alone radar/tip timing radar signal conditioning for current conventional NSMS users (as an upgrade) and new users. The hybrid system will use frequency data and relative mode vibration levels from the radar sensor to provide substantially superior capabilities over current blade-vibration measurement technology. This frequency data, coupled with a reduced number of tip timing probes, will result in a system capable of detecting complex blade vibrations that would confound traditional NSMS systems. The hardware and software package was validated on a compressor rig at Mechanical Solutions, Inc. (MSI). Finally, the hybrid radar/tip timing NSMS software package and associated sensor hardware will be installed for use in the NASA Glenn spin pit test facility.

  18. Vibrational Diver

    Science.gov (United States)

    Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef

    2014-10-01

    The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.

  19. Fast frequency-tuning of superconducting resonant rf cavities for heavy ion linear accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Peebles, Jr., Peyton Z.

    1971-12-01

    Superconducting resonant radio frequency (RF) cavities which utilize helices for producing ''slow'' wave velocities are prime candidates for creating the large accelerating electric fields needed in linear heavy ion accelerators. Because such structures are subject to mechanical vibrations, these vibrations may cause fast shifts in the cavity resonance, frequency. The result of such shifts is to cause undesirable phase modulation of the accelerating field. This report describes results of a study of an all-electronic method of fast tuning of the cavity to compensate for the vibration. Two types of control are discussed. The first employs only two electrical entrance points (ports) to the cavity. It is mechanically simpler than the second type, which uses three ports, but suffers some undesirable features not present in the three-port method.

  20. Stimulated angiogenesis for fracture healing augmented by low-magnitude, high-frequency vibration in a rat model-evaluation of pulsed-wave doppler, 3-D power Doppler ultrasonography and micro-CT microangiography.

    Science.gov (United States)

    Cheung, Wing-Hoi; Sun, Ming-Hui; Zheng, Yong-Ping; Chu, Winnie Chiu-Wing; Leung, Andraay Hon-Chi; Qin, Ling; Wei, Fang-Yuan; Leung, Kwok-Sui

    2012-12-01

    This study aimed to investigate the mechanism of low-magnitude high-frequency vibration (LMHFV) treatment on angiogenesis and blood flow for enhancement of fracture healing. Nine-month-old ovariectomized (OVX) and sham-operated (Sham) rats received closed fractures creation at the femora and were randomized into LMHFV treatment (Sham-V, OVX-V) or control (Sham-C, OVX-C) groups. Pulsed-wave Doppler indicated an increase in blood flow velocity of the femoral artery at weeks 2 (OVX pair: p = 0.030) and 4 (OVX pair: p = 0.012; Sham pair: p = 0.020) post-treatment. Significantly enhanced vascular volume (VV) at the fracture site in the vibration groups was demonstrated by 3-D high-frequency power Doppler at week 2 (Sham pair: p = 0.021) and micro-computed tomography (microCT) microangiography at weeks 2 (OVX pair: p = 0.009) and 4 (OVX pair: p = 0.034), which echoed the osteogenesis findings by radiographic and microCT analysis. VV in the OVX groups was inferior to the Sham groups. However, OVX-V showed higher percentages of angiogenic enhancement than Sham-V. Despite impaired neo-angiogenesis in osteoporotic fractures, LMHFV could increase blood flow and angiogenesis in both normal and osteoporotic fractures, thus enhancing fracture healing. Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.