VIBRATIONAL FREQUENCIES VIA FROZEN PHONONS
Harmon, B.; Weber, W.; Hamann, D
1981-01-01
We have used a first principles linear combination of atomic orbitals (LCAO) method to calculate the total ground state energy for crystals of Si, Nb and Mo involving lattice distortions. From these calculations the equilibriunm lattice constant, cohesive energy, and bulk modulus as well as the vibrational frequencies for selected phonons were determined.
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.
Low-frequency vibrational modes of glutamine
Wang, Wei-Ning; Wang, Guo; Zhang, Yan
2011-12-01
High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy. Based on the experimental and the computational results, the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations. Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.
Low-frequency vibrational modes of glutamine
Wang Wei-Ning; Wang Guo; Zhang Yan
2011-01-01
High-resolution terahertz absorption and Raman spectra of glutamine in the frequency region 0.2 THz-2.8 THz are obtained by using THz time domain spectroscopy and low-frequency Raman spectroscopy.Based on the experimental and the computational results,the vibration modes corresponding to the terahertz absorption and Raman scatting peaks are assigned and further verified by the theoretical calculations.Spectral investigation of the periodic structure of glutamine based on the sophisticated hybrid density functional B3LYP indicates that the vibrational modes come mainly from the inter-molecular hydrogen bond in this frequency region.
A model of crystalline acetanilide, ACN accounting for the C=O and N-H vibrational self-trappings is presented. We develop a fully discrete version of ACN. We show that acetanilide can be described by a set of two coupled discrete nonlinear Schroedinger (DNLS) equations. Modulational instabilities (MI) are studied both theoretically and numerically. Dispersion laws for the wave numbers and frequencies of the linear modulation waves are determined. We also derived the criterion for the existence of MI. Numerical simulations are carried out for a variety of selected wave amplitudes in the unstable zone. It is shown that instabilities grow as the wave numbers and amplitudes of the modulated waves increase. MI grow faster in the N-H mode than in the C=O mode. Temporal evolution of the density probabilities of the vibrational excitons are obtained by the numerical integration of the coupled DNLS equations governing the ACN molecule. These investigations confirm the generation of localized modes by the phenomenon of MI and the predominance of the N-H vibrational mode in the MI process of the acetanilide. (author)
A model of crystalline acetanilide, ACN accounting for the C=O and N-H vibrational self-trappings is presented. We develop a fully discrete version of ACN. We show that ACN can be described by a set of two coupled discrete nonlinear Schroedinger (DNLS) equations. Modulational instabilities (MI) are studied both theoretically and numerically. Dispersion laws for the wavenumbers and frequencies of the linear modulation waves are determined. We also derived the criterion for the existence of MI. Numerical simulations are carried out for a variety of selected wave amplitudes in the unstable zone. It is shown that instabilities grow as the wavenumbers and amplitudes of the modulated waves increase. MI grow faster in the N-H mode than in the C=O mode. Temporal evolution of the density probabilities of the vibrational excitons are obtained by the numerical integration of the coupled DNLS equations governing the ACN molecule. These investigations confirm the generation of localized modes by the phenomenon of MI and the predominance of the N-H vibrational mode in the MI process of the ACN
Low-frequency characteristics extension for vibration sensors
杨学山; 高峰; 候兴民
2004-01-01
Traditional magneto-electric vibration sensors and servo accelerometers have severe shortcomings when used to measure vibration where low frequency components predominate. A low frequency characteristic extension for velocity vibration sensors is presented in this paper. The passive circuit technology, active compensation technology and the closedcycle pole compensation technology are used to extend the measurable range and to improve low frequency characteristics of sensors. Thses three types of low frequency velocity vibration sensors have been developed and widely adopted in China.
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...
Investigation on upsetting assisted by low-frequency vibration
Zhang M.
2015-01-01
Full Text Available The application of vibration load in metal forming processes has been demonstrated to be effective in reducing the forming load. In this paper, upsetting processes assisted by low-frequency vibration at room temperature was investigated based on finite element simulations. The vibration load was applied by the reciprocating movement of the upsetting punch. The influence of vibration frequency and feeding rate were analysed. It was revealed that low-frequency vibration was effective to reduce the mean forming load and increase the friction between billets and tools.
Vibration monitor for rotating machines using average frequency technique
A vibration monitoring technique has been developed which can be applied to continuous monitoring and to patrol checking of many kinds of rotating machines in nuclear power plants. In this method, the vibrating condition in such equipment are represented in terms of two parameters, i.e. a vibration amplitude (RMS value) and an average frequency. The average frequency is defined as the root value of the second moment of the vibration frequency weighted by the power spectrum. The average frequency can be calculated by simple analogue circuits and does not need the spectrum analysis. Using these two parameter, not only the occurrence of abnormal vibration but also the type of vibration can be detected. (author)
Capacitance-Based Frequency Adjustment of Micro Piezoelectric Vibration Generator
2014-01-01
Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach th...
Multireflection sum frequency generation vibrational spectroscopy.
Zhang, Chi; Jasensky, Joshua; Chen, Zhan
2015-08-18
We developed a multireflection data collection method in order to improve the signal-to-noise ratio (SNR) and sensitivity of sum frequency generation (SFG) spectroscopy, which we refer to as multireflection SFG, or MRSFG for short. To achieve MRSFG, a collinear laser beam propagation geometry was adopted and trapezoidal Dove prisms were used as sample substrates. An in-depth discussion on the signal and SNR in MRSFG was performed. We showed experimentally, with "m" total internal reflections in a Dove prism, MRSFG signal is ∼m times that of conventional SFG; SNR of the SFG signal-to-background is improved by a factor of >m(1/2) and
A long-stroke horizontal electromagnetic vibrator for ultralow-frequency vibration calibration
A novel long-stroke horizontal electromagnetic vibrator with maximum stroke of 1 m is proposed. To reply to the strong nonlinearity arising from long stroke, a closed double-magnetic circuit with optimal air gap, an electro-viscoelastic-suspension device and a track following device are adopted in the vibrator. Also, a compact moving component with a higher first-order natural frequency is designed to increase the operating frequency of the vibrator. Finally, experimental results show that the vibrator could output low distortion acceleration on its working platform from 0.002 Hz to 100 Hz, which verifies the validity of the proposed technologies and the applicability of the vibrator for an ultralow-frequency vibration calibration system. (paper)
Sweeping tuneable vibration absorbers for low-mid frequencies vibration control
Gardonio, P.; Zilletti, M.
2015-10-01
This paper presents a simulation study concerning the low-mid frequencies control of flexural vibration in a lightly damped thin plate, which is equipped with three sweeping tuneable vibration absorbers and is excited by a rain on the roof broad frequency band stationary disturbance. The sweeping tuneable vibration absorbers are semi-active mass-spring-dashpot systems whose stiffness and damping properties can be varied uniformly within given ranges. They are operated in such a way as their characteristic natural frequencies are continuously varied to control the response of flexural modes that resonate within given frequency bands. More specifically, in this study the three sweeping tuneable vibration absorbers are operated asynchronously, each within one of three sequential frequency bands comprised between 20 and 120, 120 and 220, 220 and 320 Hz. The flexural vibration control effects produced by the three sweeping tuneable vibration absorbers are compared to those produced by three classical tuneable vibration absorbers, each set to control the response of a specific flexural mode of the plate resonating in one of these three frequency bands. The study shows that the proposed sweeping tuneable vibration absorbers outperform the classical tuneable vibration absorbers and produce about 6, 5, 4 dB reduction of the plate overall flexural response in the three frequency bands of operation. Also, the study indicates that the sweeping tuneable vibration absorbers are robust to variations in the plate flexural response. For instance they still produce about 5.1, 5.3, 4.6 dB reductions of the flexural response in the three frequency bands of operation when the plate is tensioned such that the flexural natural frequencies are shifted up from about 40 percent, for the first resonance, to 7 percent, for the tenth resonance.
Vibration velocity and frequency of underwater short-hole blasting
无
2002-01-01
Based on the measuring data of underwater blasting vibrationand the regression analysis results of these data, two formulae usually used of blasting vibration velocity were compared. Factors that canaffect blasting vibration and frequency were summarized and analyzed.It is thought that the effect of the number of freedom face and burden direction on blasting vibration should be considered during blastingdesign. Based on the relevant research results and the regression results of these data, a formula to calculate under water blasting frequency was put forward.
A vibration energy harvesting device with bidirectional resonance frequency tunability
Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibrating structures, a general requirement independent of the energy transfer mechanism is that the vibration energy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ± 20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22–32 Hz to enable a continuous power output 240–280 µW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined
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 to one of the oxygens of the carboxylate group of the C-terminus or to the oxygen of the amide group of one of the other residues. Hence we conclude that the zwitterionic species of LeuE is not stable in the isolated state. Spectral simulations of the species expected to be found in the isolated state can be compared to the measured VA, VCD and Raman spectra of LeuE in non-polar solvents to identify which conformer or conformers of LeuE are present in these media. Characteristic features in the VCD spectra are more sensitive to conformational changes than those in either the VA or Raman spectra, similar to the characteristic features in electronic circular dichroism spectra with respect to those in the UV-vis electronic absorption spectra. Finally, we have also attempted to stabilize the zwitterionic species by treating the aqueous environment by using a continuum solvent approach, the Onsager model. Here we found that the zwitterionic species is now stable. The neutral species in an aqueous environment was also modelled by the continuum solvent approaches to determine the
Neuropathy in female dental personnel exposed to high frequency vibrations.
Akesson, I; Lundborg, G.; Horstmann, V; Skerfving, S
1995-01-01
OBJECTIVE--To evaluate early neuropathy in dental personnel exposed to high frequency vibrations. METHODS--30 dentists and 30 dental hygienists who used low and high speed hand pieces and ultrasonic scalers were studied, and 30 dental assistants and 30 medical nurses not exposed to vibration (all women). Vibrotactile sensibility, strength, motor performance, sensorineural symptoms and signs, and vascular symptoms in the hands, as well as mercury concentrations in biological samples and cervic...
Capacitance-Based Frequency Adjustment of Micro Piezoelectric Vibration Generator
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.
Frequency of Optical Vibrations in Fluorite (CaF2)
The authors studied the optical vibration frequencies of fluorite. Particular attention was paid to determining the frequencies at q ≅ 0. The use of a time-of-flight basis of 8.30 m and a resolution of 6 μs/m permitted the frequencies to be determined to an accuracy of 1%. The findings were as follows: Raman frequency νR = 9. 66 x l012 c/sec infra-red absorption frequency (transverse vibration) νT = 7. 75 x 1012 c/sec; longitudinal infra-red frequency νL, = 14.3 6 x 1012 c/sec. Within experimental errors, the Lyddane-Sachs-Teller correlation was verified. (author)
Low-frequency vibration control of floating slab tracks using dynamic vibration absorbers
Zhu, Shengyang; Yang, Jizhong; Yan, Hua; Zhang, Longqing; Cai, Chengbiao
2015-09-01
This study aims to effectively and robustly suppress the low-frequency vibrations of floating slab tracks (FSTs) using dynamic vibration absorbers (DVAs). First, the optimal locations where the DVAs are attached are determined by modal analysis with a finite element model of the FST. Further, by identifying the equivalent mass of the concerned modes, the optimal stiffness and damping coefficient of each DVA are obtained to minimise the resonant vibration amplitudes based on fixed-point theory. Finally, a three-dimensional coupled dynamic model of a metro vehicle and the FST with the DVAs is developed based on the nonlinear Hertzian contact theory and the modified Kalker linear creep theory. The track irregularities are included and generated by means of a time-frequency transformation technique. The effect of the DVAs on the vibration absorption of the FST subjected to the vehicle dynamic loads is evaluated with the help of the insertion loss in one-third octave frequency bands. The sensitivities of the mass ratio of DVAs and the damping ratio of steel-springs under the floating slab are discussed as well, which provided engineers with the DVA's adjustable room for vibration mitigation. The numerical results show that the proposed DVAs could effectively suppress low-frequency vibrations of the FST when tuned correctly and attached properly. The insertion loss due to the attachment of DVAs increases as the mass ratio increases, whereas it decreases with the increase in the damping ratio of steel-springs.
Multiple vibration intensities and frequencies for bone mineral density improvement.
Ezenwa, Bertram; Burns, Edith; Wilson, Charles
2008-01-01
Devices that deliver controlled quantum vibration intensities at multiple frequencies (QVIMF) provide optimal stress to the musculoskeletal system for improved bone mineral density and muscle strength. This paper presents development of a QVIMF system and pilot study to determine device performance. Development is centered on specially-designed actuators that comprise multiple nodes of controlled and smooth, but variable rates of contact on a telescoping platform through sets of damping subsystems. The combination of specially-designed actuators and damping subsystems, powered by a DC controlled motor, delivers quantum busts of vibration at multiple frequencies resulting in whole body vibration. An initial feasibility study involved a 79 year old adult male. After IRB approval from both the University of Wisconsin-Milwaukee (UWM) and the Zablocki VA Medical Center, Milwaukee, the subject's bone mineral density (BMD) was measured by dual x-ray absorptimetry (DXA) at baseline. The subject then visited the UWM laboratory for two fifteen-minute vibration sessions per visit, three times a week for a total of 60 visits. Post-vibration BMD was again measured by DXA. Comparison pre- and post-vibration test results showed increases in BMD at the femoral neck, trochanter, total hip, forearm and lower lumbar spine (L1-4). PMID:19163635
Sun, Shuaishuai; Yang, Jian; Li, Weihua; Deng, Huaxia; Du, Haiping; Alici, Gursel; Yan, Tianhong
2016-05-01
A new design of adaptive tuned vibration absorber was proposed in this study for vibration reduction. The innovation of the new absorber is the adoption of the eccentric mass on the top of the multilayered magnetorheological elastomer (MRE) structure so that this proposed absorber has two vibration modes: one in the torsional direction and the other in translational direction. This property enables the absorber to expand its effective bandwidth and to be more capable of reducing the vibrations especially dealing with those vibrations with multi-frequencies. The innovative MRE absorber was designed and tested on a horizontal vibration table. The test results illustrate that the MRE absorber realized double natural frequencies, both of which are controllable. Inertia’s influence on the dynamic behavior of the absorber is also investigated in order to guide the design of the innovative MRE absorber. Additionally, the experimentally obtained natural frequencies coincide with the theoretical data, which sufficiently verifies the feasibility of this new design. The last part in terms of the vibration absorption ability also proves that both of these two natural frequencies play a great role in absorbing vibration energy.
Gearbox Vibration Signal Amplitude and Frequency Modulation
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.
Han, Jae-Hung; Youn, Se-Hyun; Jeong, Ho-Kyung; Jang, Young-Soon
2012-04-01
Launch vehicles, satellites and aircrafts often experience harsh vibration and pyroshock loads during the flight including maneuvering and separation events, which may cause the malfunction of equipped electronic devices. Furthermore, this minor malfunction can generate catastrophic failure of the whole mission. To prevent malfunction of the electronic devices from severe shock and vibration loads, elastomeric isolators are commonly applied between the electronic device and the equipment bay structure in the aerospace fields. However, this rubber type elastomeric material is vulnerable to the low-frequency vibration load which involves large amount of displacement due to its low stiffness. Recently, the present authors proposed new type of isolator, called as pseudoelastic hybrid mesh isolator. This talk introduces the key features of this new pseudoelastic hybrid mesh isolator which shows better isolation performance throughout all frequency range than conventional isolators.
About resonance frequencies of aluminium alloy bending vibrations
Using ultrasonic method resonance frequencies of bending vibrations and elastic moduli of aluminium alloy SAV-1 samples are investigated. On the base of spectra of bending vibrations in low-frequency range data on values of a number of elastic properties are obtained as well as dispersion characteristics of main moduli for number of frequencies before and after ionizing irradiation (60Co, 5x103-1.6x107 Gy) of samples. Considerable stability of sample elastic moduli during common storage conditions and nonlinear dose dependence of these parameters within wide range of absorbed doses are pointed out. Possible causes of revealed effects of radiation modification of elastic properties of SAV-1 alloy are analyzed
Frequency Identification of Vibration Signals Using Video Camera Image Data
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.
A low frequency vibration energy harvester using magnetoelectric laminate composite
In this paper, we present a vibration energy harvester using magnetoelectric laminate composite and a springless spherical permanent magnet as a proof mass. The harvester utilizes a freely movable spherical permanent magnet to transform external vibration into a time varying magnetic field applied to the magnetoelectric transducer. The laminate composite consists of a Ni–Mn–Ga-based MSMA (magnetic shape memory alloy) element and a PZT (lead zirconate titanate) plate. A proof-of-concept harvester has been fabricated and characterized at various input accelerations and frequencies. A maximum open circuit voltage of 1.18 V has been obtained in response to a 3g vibration at 17 Hz with the fabricated device. Moreover, a maximum output voltage of 10.24 V and output power of 4.1 μW have been achieved on a 950 Ω load, when the fabricated energy harvester was mounted on a smartphone and shaken by hand. (paper)
Investigating buried polymer interfaces using sum frequency generation vibrational spectroscopy
Chen, Zhan
2010-01-01
This paper reviews recent progress in the studies of buried polymer interfaces using sum frequency generation (SFG) vibrational spectroscopy. Both buried solid/liquid and solid/solid interfaces involving polymeric materials are discussed. SFG studies of polymer/water interfaces show that different polymers exhibit varied surface restructuring behavior in water, indicating the importance of probing polymer/water interfaces in situ. SFG has also been applied to the investigation of interfaces b...
High-frequency vibrations of sandwich plates and delamination detection
Jensen, Alf E.; Irgens, Fridtjov
1998-06-01
In multi-hull marine vehicles assembled by FRP sandwich composite materials problems with delamination and skin/core debonding are reported. High frequency vibrations in foam core sandwich materials are investigated to see if it was possible to apply them, together with bending vibrations, in an early damage warning system for delamination detection in marine vessels. This manuscript presents a theory for high frequency vibration in sandwich plates and beams. The core is modeled as a two parameter foundation with shearing interaction effects as well as normal stress effects in the core included. The skins are modeled as ordinary plates or beams on a foundation. Expressions for both anti-symmetric and symmetric modes are given. In addition to the theoretical development, experiments with a simply supported sandwich beam, using a TV-Holography technic, were performed and good accordance between theory and experiments were achieved. The results indicates that disappearance of symmetric modes may be used a parameter for delamination detection. The anti-symmetric modes may be interchangeable with higher bending modes by an early damage warning system. To avoid this, the theory presented may be applied to determine the anti-symmetric frequency values in forehand.
Simulation applied to working frequency selection in large-scale vibrating screen's design
PENG Chen-yu; SU Rong-hua
2011-01-01
The working frequency selection of the ZK30525 vibrating screen was studied using ANSYS.Integrating the dynamic performance simulation analysis of the vibrating screen structure,the variation laws of beams' vibration displacements changing with different exciting frequencies were researched.These beams include six beams,with one discharging beam and one in-material beam.Results indicate that vibration displacements in the middle of these beams increase with the augmentation of exciting frequency.When exciting frequency exceeds a certain value,there exists a flat change region for vibration displacement.According to vibrator characteristics,the vibrating screen's working frequency should be selected in the flat change region,and be far away from modal frequencies.The study provides theoretical guidance for the reasonable working frequency selection of the large-scale vibrating screen.
Low-Frequency Meandering Piezoelectric Vibration Energy Harvester
Berdy, David F.; Srisungsitthisunti, Pornsak; Jung, Byunghoo; Xu, Xianfan; Rhoads, Jeff F.; Peroulis, Dimitrios
2012-01-01
The design, fabrication, and characterization of a novel low-frequency meandering piezoelectric vibration energy harvester is presented. The energy harvester is designed for sensor node applications where the node targets a width-to-length aspect ratio close to 1: 1 while simultaneously achieving a low resonant frequency. The measured power output and normalized power density are 118 mu W and 5.02 mu W/mm(3)/g(2), respectively, when excited by an acceleration magnitude of 0.2 g at 49.7 Hz. Th...
Low-frequency meandering piezoelectric vibration energy harvester.
Berdy, David F; Srisungsitthisunti, Pornsak; Jung, Byunghoo; Xu, Xianfan; Rhoads, Jeffrey F; Peroulis, Dimitrios
2012-05-01
The design, fabrication, and characterization of a novel low-frequency meandering piezoelectric vibration energy harvester is presented. The energy harvester is designed for sensor node applications where the node targets a width-to-length aspect ratio close to 1:1 while simultaneously achieving a low resonant frequency. The measured power output and normalized power density are 118 μW and 5.02 μW/mm(3)/g(2), respectively, when excited by an acceleration magnitude of 0.2 g at 49.7 Hz. The energy harvester consists of a laser-machined meandering PZT bimorph. Two methods, strain-matched electrode (SME) and strain-matched polarization (SMP), are utilized to mitigate the voltage cancellation caused by having both positive and negative strains in the piezoelectric layer during operation at the meander's first resonant frequency. We have performed finite element analysis and experimentally demonstrated a prototype harvester with a footprint of 27 x 23 mm and a height of 6.5 mm including the tip mass. The device achieves a low resonant frequency while maintaining a form factor suitable for sensor node applications. The meandering design enables energy harvesters to harvest energy from vibration sources with frequencies less than 100 Hz within a compact footprint. PMID:22622969
Cross-Propagation Sum-Frequency Generation Vibrational Spectroscopy
Fu, Li; Chen, Shunli; Gan, Wei; Wang, Hongfei
2016-02-01
Here we report the theory formulation and the experiment realization of sum-frequency generation vibrational spectroscopy (SFG-VS) in the cross-propagation (XP) geometry or configuration. In the XP geometry, the visible and the infrared (IR) beams in the SFG experiment are delivered to the same location on the surface from visible and IR incident planes perpendicular to each other, avoiding the requirement to have windows or optics to be transparent to both the visible and IR frequencies. Therefore, the XP geometry is applicable to study surfaces in the enclosed vacuum or high pressure chambers with far infrared (FIR) frequencies that can directly access the metal oxide and other lower frequency surface modes, with much broader selection of visible and IR transparent window materials.
In this paper, we investigate a two electronic level system with vibrational modes coupled to a Brownian oscillator bath. The difference frequency generation (DFG) signals and sum frequency generation (SFG) signals are calculated. It is shown that, for the same model, the SFG signals are more sensitive than the DFG signals to the changes of the vibrational modes of the electronic two-level system. Because the SFG conversion efficiency can be improved by using the time-delay method, the findings in this paper predict that the SFG spectrum may probe the changes of the microstructure more effectively. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
GU An-Na; LIANG Xian-Ting
2011-01-01
In this paper, we investigate a two electronic level system with vibrational modes coupled to a Brownian oscillator bath. The difference frequency generation (DFG) signals and sum frequency generation (SFG) signals are calculated. It is shown that, for the same model, the SFG signals are more sensitive than the DFG signals to the changes of the vibrational modes of the electronic two-level system. Because the SFG conversion efficiency can be improved by using the time-delay method, the findings in this paper predict that the SFG spectrum may probe the changes of the microstructure more effectively.
Nature of the Frequency Shift of Hydrogen Valence Vibrations
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.
High-frequency and low-frequency effects on vibrational resonance in a synthetic gene network
The high-frequency and low-frequency effects on vibrational resonance (VR) in a synthetic gene network are studied. Results show that the role of the high-frequency signal in VR acts as that of noise in stochastic resonance (SR), namely a high-frequency signal can change the effective value of the control parameter such that the random state–state transitions of the switch can happen. A low-frequency signal with lower frequency and higher amplitude tends to favor the response of the system. When VR occurs, the ratio of the optimal amplitude (Bopt) to the corresponding frequency (Ω) of the high-frequency signal is a definite constant. Furthermore, if noise is introduced into the system, noise plays a suppressive role for VR, and various resonance phenomena including the bell-shaped VR and VR without tuning are exhibited in the system
Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies
Wang, Zenghui; Jia, Hao; Zheng, Xuqian; Yang, Rui; Wang, Zefang; Ye, G. J.; Chen, X. H.; Shan, Jie; Feng, Philip X.-L.
2014-12-01
We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ~100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ~200 nm down to ~20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory devices and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus.We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ~100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ~200 nm down to ~20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory
High force vibration testing with wide frequency range
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.
DESIGN AND DYNAMICAL SIMULATION TO NEW VIBRATING CENTRIFUGE WITH WIDER FREQUENCY RANGE
无
2006-01-01
A new type of vibrating centrifuge with wider frequency range is designed instead of the traditional one with a single frequency to improve the vibrating effect. With the aid of a new dynamical model, one simulation without considering the visco-elasticity of basis is presented, then the dynamical responses of time and frequency in different scheme are given. The computational results show that the improved vibrating centrifuge possesses a remarkably widened frequency range.
A Study on the Vibration Frequency of Blasting Excavation in Highly Stressed Rock Masses
Yang, Jianhua; Lu, Wenbo; Jiang, Qinghui; Yao, Chi; Jiang, Shuihua; Tian, Lin
2016-07-01
During blasting excavation in deep-buried tunnels and mines characterized by high in situ stress, the rock vibration is attributed not only to blast loading, but also to dynamic unloading caused by transient release of the in situ stress on excavation faces in the process of rock fragmentation by blasting. Understanding the vibration frequency characteristics under these two excitation sources is of important signification to determine appropriate vibration threshold limits for structure damage in deep-buried opening excavations. With a theoretical model developed for a deep-buried circular tunnel excavation by the millisecond delay blasting sequence, frequency characteristics and their influence factors are investigated and discussed for the vibrations induced by the blast loading, the dynamic unloading and the combined effects, respectively. The results show that the rising time of blast loading, the duration of dynamic unloading and the dimension of excavation boundaries are the main factors that affect the vibration frequency of blasting excavation in highly stressed rock masses. It is found that, the blast loading with a much shorter rising time accentuates higher vibration frequency than the dynamic unloading with a long duration, and it causes the blast loading vibration to be more readily attenuated as the propagation distance increases. Thus, the unloading vibration may become the main vibration component at far distances where its low-frequency vibration may exceed the vibration limits. The vibration induced by the combined effects has two distinctly dominant frequency bands corresponding to the two vibration excitation sources. The frequency analyses of the vibration records from two underground projects excavated by blasting are presented to demonstrate this finding. The findings of this study also clearly reveal that, reducing the dimension of excavation boundaries is one of the most effective means to prevent the vibrational damage to structures as it
Complete WKB asymptotics of high frequency vibrations in a stiff problem
Babych, N
2008-01-01
Asymptotic behaviour of eigenvalues and eigenfunctions of a stiff problem is described in the case of the fourth-order ordinary differential operator. Considering the stiffness coefficient that depends on a small parameter epsilon and vanishes as epsilon tends to zero on a subinterval, we prove the existence of low and high frequency resonance vibrations. The low frequency vibrations admit the power series expansions on epsilon but this method is not applicable to the description of high frequency vibrations. However, the nonclassical asymptotics on epsilon of the high frequency vibrations were constructed using the WKB method.
Studies of structure, vibrational frequencies and thermodynamics of UF6
LU Chun-Hai; SUN Ying; CHEN Wen-Kai; QIU Shao-Yu
2005-01-01
After molecular structure of UF6 is optimized, molecular vibrational frequencies are calculated by LDA and GGA approaches. Some thermodynamic parameters are calculated based on the principle of statistic mechanics.Various functionals such as PWC, VWN, VWNPB, PW91, BP, PBE, RPBE, BOP with various basis sets such as MIN, DN, DND and DNP are used. The small basis sets, MIN and DN, can arrive at self-consistency. DMol3 can save more CPU's time and resource than all electron calculations including Hartree-Fock and DFT with Gaussian code, so it should be introduced in some research, especially on compounds of lanthanide and actinide. However,comparing with the results from classical DFT, the new calculation may accompany a rather large error.
Grid Cell Relaxation Effects on the High Frequency Vibration Characteristics
The plate structure of the grid of fuel assembly is always exposed to serious vortex induced vibration. Also, High Frequency flow induced Vibration (HFV) is primarily generated by vortex-shedding effect. When it comes to grid design as a fuel assembly component, HFV should be considered in advance since it is one of the critical factors. Excessive HFV has a possibility of making degradation of the fuel reliability that is directly related to the fuel robustness and operating performance. KEPCO NF (KNF) has performed HFV tests with various grid designs. While studying the HFV characteristics through the HFV tests, it has been observed that HFV amplitudes show different levels according to grid cell relaxation. It means that the testing could give different interpretations due to the condition of grid cell. Since the amount of relaxation is different under operating conditions and environments in a reactor, test specimens should be modified as much as possible to the real state of the fuel. Therefore, in order to consider the grid cell relaxation effects on the HFV tests, it is important to use cell sized or non-cell sized grids. The main focus of this study is to find out how the HFV characteristics such as amplitude and frequency are affected by grid cell relaxation. Three cases of the grid cell sized specimen which is nickel alloy were prepared and tested. Through the comparison of the test results, it could be concluded that HFV amplitudes show decreasing trend according to the grid cell relaxation in the case of nickel alloy grid. It is also possible to expect the tendency of grid cell relaxation of a zirconium alloy grid based on test results
Tang, Qiaochu; Yang, Yongliang; Li, Xinxin
2014-04-01
An electromagnetic kinetic energy harvester has been developed, which can convert ultra-low-frequency motion and vibration energy into electrical power. This harvester employs a two-stage vibratory structure to collect low-frequency kinetic energy and effectively transfer it into electric power by using a pair of high-frequency resonant generators. Non-contact magnetic repulsive force is herein utilized for the 1st-stage sliding vibrator to drive the 2nd-stage resonators into frequency-up-conversion resonance. The non-contact actuation is helpful for durable and long-life working of the device. The prototyped device is fabricated and the design is well confirmed by experimental test. The harvester can be well operated at the frequency as low as 0.25 Hz. Under driving acceleration of 1 g at 0.5 Hz, the miniaturized harvester can generate a peak power of 4.42 mW and an average power of 158 μW.
Tang, Qiaochu; Yang, Yongliang; Li, Xinxin
2014-04-01
An electromagnetic kinetic energy harvester has been developed, which can convert ultra-low-frequency motion and vibration energy into electrical power. This harvester employs a two-stage vibratory structure to collect low-frequency kinetic energy and effectively transfer it into electric power by using a pair of high-frequency resonant generators. Non-contact magnetic repulsive force is herein utilized for the 1st-stage sliding vibrator to drive the 2nd-stage resonators into frequency-up-conversion resonance. The non-contact actuation is helpful for durable and long-life working of the device. The prototyped device is fabricated and the design is well confirmed by experimental test. The harvester can be well operated at the frequency as low as 0.25 Hz. Under driving acceleration of 1 g at 0.5 Hz, the miniaturized harvester can generate a peak power of 4.42 mW and an average power of 158 μW. PMID:24784650
Tsujino, J; Ihara, S; Harada, Y; Kasahara, K; Sakamaki, N
2004-04-01
Welding characteristic of thin coated copper wires were studied using 40, 60, 100 kHz ultrasonic complex vibration welding equipments with elliptical to circular vibration locus. The complex vibration systems consisted of a longitudinal-torsional vibration converter and a driving longitudinal vibration system. Polyurethane coated copper wires of 0.036 mm outer diameter and copper plates of 0.3 mm thickness and the other dimension wires were used as welding specimens. The copper wire part is completely welded on the copper substrate and the insulated coating material is driven from welded area to outsides of the wire specimens by high frequency complex vibration. PMID:15047272
Low frequency vibration tests on a floating slab track in an underground laboratory
De-yun DING; Wei-ning LIU; Ke-fei LI; Xiao-jing SUN; Wei-feng LIU
2011-01-01
Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating slab track (FST), low frequency vibration tests on an FST in an underground laboratory at Beijing Jiaotong University were carried out. The FST and an unbalanced shaker SBZ30 for dynamic simulation were designed for use in low frequency vibration experiments. Vibration measurements were performed on the bogie of the unbalanced shaker, the rail, the slab, the tunnel invert, the tunnel wall, the tunnel apex, and on the ground surface at distances varying from 0 to 80 m from the track. Measurements were also made on several floors of an adjacent building. Detailed results of low frequency vibration tests were reported. The attenuation of low frequency vibrations with the distance from the track was presented, as well as the responses of different floors of the building. The experimental results could be regarded as a reference for developing methods to control low frequency vibrations and for adopting countermeasures.
Nan, Yi-Bing; Tang, Yi; Zhang, Li-Jun; Zheng, Cheng; Wang, Jing
2015-05-01
Satellite vibrations during exposure will lead to pixel aliasing of remote sensors, resulting in the deterioration of image quality. In this paper, we expose the problem and discuss the characteristics of satellite vibrations, and then present a pixel mixing model. The idea of mean mixing ratio (MMR) is proposed. MMR computations for different frequencies are implemented. In the mixing model, a coefficient matrix is introduced to estimate each mixed pixel. Thus, the simulation of degraded image can be performed when the vibration attitudes are known. The computation of MMR takes into consideration the influences of various frequencies and amplitudes. Therefore, the roles of these parameters played in the degradation progress are identified. Computations show that under the same vibration amplitude, the influence of vibrations fluctuates with the variation of frequency. The fluctuation becomes smaller as the frequency rises. Two kinds of vibration imaging experiments are performed: different amplitudes with the same frequency and different frequencies with the same amplitude. Results are found to be in very good agreement with the theoretical results. MMR has a better description of image quality than modulation transfer function (MTF). The influence of vibrations is determined mainly by the amplitude rather than the frequency. The influence of vibrations on image quality becomes gradually stable with the increase of frequency. Project supported by the National Basic Research Program of China (Grant No. 2013CB329202) and the Basic Industrial Technology Project of China (Grant No. J312012B002).
High frequency pneumatic vibrator to clean the heating surfaces of boiler units
Byalik, E.I.; Kulakov, M.M.; Guzenko, S.I.; Vishnevetskii, A.I.
1977-02-01
The design, operation, and performance of a high-frequency cooled pneumatic vibrator with directional, i.e., axial agitation, action for removal of external deposits from boiler heating surfaces are described. In comparison with the electric-powered mechanical vibrators widely used at power stations, the pneumatic vibrator with the same driving force creates double the acceleration, has weight of 2 to 3 times less, is safer for operation under conditions of high temperature, moisture and pollution and permits smooth regulation of the frequency of the oscillations, thus avoiding dangerous resonance phenomena in parts of the system subject to vibration. For reliable and efficient operation of the pneumatic vibrator it is necessary to maintain an air pressure ahead of it of not less than 4 kgF/cm/sup 2/. At a vibration plate temperature of over 60/sup 0/C it is necessary to use water cooling of the vibrator housing. (LCL)
Suppression of Leidenfrost effect via low frequency vibrations
Ng, Boon Thiam; Hung, Yew Mun; Tan, Ming Kwang
2015-11-01
Leidenfrost effect occurs when vapor layer forms in between the coolant and the hot surface above Leidenfrost point, which dramatically reduces the cooling efficiency due to low thermal conductivity of the vapor layer. To prevent surface overheating, there have been number of reported methods to suppress the Leidenfrost effect that were mainly based on functionalization of the substrate surface and application of electric field across the droplet and substrate. In this work, we induce low frequency vibrations (f ~ 100 Hz) to the heated substrate to suppress the Leidenfrost effect. Three distinct impact dynamics are observed based on different magnitudes of surface acceleration and surface temperature. In gentle film boiling regime, formation of thin spreading lamella around the periphery of the impinged droplet is observed; in film boiling regime, due to thicker vapor cushion, rebound of the impinged droplet is observed; in contact boiling regime, due to the direct contact between the impinged droplet and heated substrate, ejection of the tiny droplet is observed. Also, estimated cooling enhancement ratio for contact boiling regime shows an improvement from 95% to 105%.
Active low-frequency vertical vibration isolation system for precision measurements
Wu, Kang; Li, Gang; Hu, Hua; Wang, Lijun
2016-06-01
Low-frequency vertical vibration isolation systems play important roles in precision measurements to reduce seismic and environmental vibration noise. Several types of active vibration isolation systems have been developed. However, few researches focus on how to optimize the test mass install position in order to improve the vibration transmissibility. An active low-frequency vertical vibration isolation system based on an earlier instrument, the Super Spring, is designed and implemented. The system, which is simple and compact, consists of two stages: a parallelogram-shaped linkage to ensure vertical motion, and a simple spring-mass system. The theoretical analysis of the vibration isolation system is presented, including terms erroneously ignored before. By carefully choosing the mechanical parameters according to the above analysis and using feedback control, the resonance frequency of the system is reduced from 2.3 to 0.03 Hz, a reduction by a factor of more than 75. The vibration isolation system is installed as an inertial reference in an absolute gravimeter, where it improved the scatter of the absolute gravity values by a factor of 5. The experimental results verifies the improved performance of the isolation system, making it particularly suitable for precision experiments. The improved vertical vibration isolation system can be used as a prototype for designing high-performance active vertical isolation systems. An improved theoretical model of this active vibration isolation system with beam-pivot configuration is proposed, providing fundamental guidelines for vibration isolator design and assembling.
Xu, Qing-Hua; Fayer, M. D.
2002-08-01
Frequency-selected vibrational echo experiments were used to investigate the temperature dependences of vibrational dephasing associated with the 0-1 transition of the CO stretching mode of RuTPPCOPy (TPP=5,10,15,20-tetraphenylporphyrin, Py=pyridine) in two solvents: polymethylmethacrylate (PMMA) and 2-methyltetrahydrofuran (2-MTHF). In PMMA, a glass, the echo decay is exponential at all the temperatures studied, and the dephasing rate increases linearly with increasing temperature. In 2-MTHF, there is a change in the functional form of the temperature dependence when the solvent goes through the glass transition temperature (Tg). Below Tg, the dephasing rate increases linearly with temperature, while above Tg, it rises very steeply in a nonlinear manner. In the liquid at higher temperatures, the vibrational echo decays are nonexponential. A model frequency-frequency correlation function (FFCF) is proposed in which the FFCF differs for a glass and a liquid because of the intrinsic differences in the nature of the dynamics. At least two motions, inertial and diffusive, contribute to the vibrational dephasing in the liquids. The different temperature dependences of inertial and diffusive motions are discussed. Comparison of the model calculations of the vibrational echo temperature dependence and the data show reasonable, but not quantitative agreement.
Dispersion of low frequency vibrations in the deuterated naphthalene crystal
The dispersion curves of the lattice vibrations and of the two lowest intramolecular vibrations in d8-naphthalene (C10D8) crystal have been measured by coherent inelastic neutron scattering for the [010] and the [100] directions at the temperature of 98 K and partially at 5 K. The results are compared with calculations based on the Kitaigorodskii parameters for C-C, C-H and H-H interactions in organic molecular crystals. (author)
In order to research the effects of vibration aging on micro-scale thin films, a high frequency vibration system is designed for the aging of a polymer AZ4620 photoresist film. The profile method is adopted to predict the residual stresses in the film. A laser measuring device is constructed to measure the sample profiles in the experiment. The excitation frequencies for vibration aging are determined using the finite element method. The effects of vibration parameters on aging results are studied, such as excitation frequency, vibration aging time, exciting power and vibration acceleration. Results show that the more vibration nodes that existed in sample’s inherent mode, the better vibration aging results can be obtained under this excitation frequency. Under the excitation frequency of 6932 Hz and excitation current 5 A, and vibration aging for only 14 min, the residual stress elimination rate already reached 51.52%. (paper)
Modeling of metallic surface topography modification by high-frequency vibration
Yao, Zhehe; Mei, Deqing; Chen, Zichen
2016-02-01
High-frequency vibration is capable of modifying metallic surface topography significantly, while the underlying mechanisms are still unclear. In this study, the acoustic softening effect is considered to explain and model the effects of high-frequency normal vibration on surface topography. The surface asperities can be softened by the high-frequency vibration due to acoustic softening, leading to the enhancement of surface topography modification. A theoretical model for metallic surface topography modification by high-frequency vibration is proposed based on the acoustic plasticity. Numerical predictions of surface roughness evolution were conducted under various working conditions based on the model developed. It was found that the reduction of surface roughness (RSR) after vibration-assisted forming was affected by static stress, vibration amplitude, material properties and initial specimen surface roughness. The predictions using the developed model were compared with experimental data. Results showed that the predicted RSR agreed well with the experimental results, indicating that the analytical model is able to accurately capture surface topography evolution during vibration-assisted metal forming. This study provides a basis for understanding the underlying mechanisms of surface topography modification in vibration-assisted manufacturing.
Investigation into high-frequency-vibration assisted micro-blanking of pure copper foils
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.
Zhang, Hua A.; Zhu, Yonghao; He, Yun
1993-05-01
This article reports the application of laser range imaging radar in the measurement of mechanical vibration frequency and the mode distribution, and the periodic motion of the mechanical parts such as a piston rod. The principle of the laser range imaging radar is based on the phase shift of the reflected amplitude modulated laser beam. The mechanical vibration frequency up to 20 KHZ and the minimal retrieved amplitude (or the motion displacement) of 0.5 mm have been achieved with the laser modulating frequency of 40 MHZ. With appropriate modulating frequency, this laser range system can measure the mechanical vibration amplitude, or the moving displacement, from 10-1 mm up to 102 mm, or even higher to the order of meters, which will be useful to measure the vibration and the periodic motion of machines and their parts for field test.
Vibration frequency control of a polymer beam using embedded shape-memory-alloy fibres
The possibility to actively change the natural vibration frequencies of a composite beam by electrically activating a series of embedded shape-memory-alloy fibres is investigated. A model system composed of an epoxy matrix with prestrained shape-memory-alloy fibres is used. The natural frequencies of vibration of the composite are measured in a clamped beam configuration. When electrically heated, the fibres undergo a reverse martensite to austenite transformation. Since this transformation is restrained by the constraints of both the matrix and the clamping device, a recovery force is generated. This force produces an increase of the natural frequency of vibration of the whole composite beam. Vibration frequency changes of more than 50% are obtained. The glass-to-rubber transition of the matrix affects the reversibility of the effect. The role of the matrix thermal expansion is discussed. (orig.)
Statistical analysis of low frequency vibrations in variable speed wind turbines
The spectral content of the low frequency vibrations in the band from 0 to 10 Hz measured in full scale wind turbines has been statistically analyzed as a function of the whole range of steady operating conditions. Attention has been given to the amplitudes of the vibration peaks and their dependency on rotating speed and power output. Two different wind turbine models of 800 and 2000 kW have been compared. For each model, a sample of units located in the same wind farm and operating during a representative period of time have been considered. A condition monitoring system installed in each wind turbine has been used to register the axial acceleration on the gearbox casing between the intermediate and the high speed shafts. The average frequency spectrum has permitted to identify the vibration signature and the position of the first tower natural frequency in both models. The evolution of the vibration amplitudes at the rotor rotating frequency and its multiples has shown that the tower response is amplified by resonance conditions in one of the models. So, it is concluded that a continuous measurement and control of low frequency vibrations is required to protect the turbines against harmful vibrations of this nature
A smart and self-sufficient frequency tunable vibration energy harvester
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/
The effects of low-frequency vibrations on hepatic profile of blood
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
An extension of command shaping methods for controlling residual vibration using frequency sampling
Singer, Neil C.; Seering, Warren P.
1992-01-01
The authors present an extension to the impulse shaping technique for commanding machines to move with reduced residual vibration. The extension, called frequency sampling, is a method for generating constraints that are used to obtain shaping sequences which minimize residual vibration in systems such as robots whose resonant frequencies change during motion. The authors present a review of impulse shaping methods, a development of the proposed extension, and a comparison of results of tests conducted on a simple model of the space shuttle robot arm. Frequency shaping provides a method for minimizing the impulse sequence duration required to give the desired insensitivity.
Lu, Cheng; Liu, Guodong; Liu, Bingguo; Chen, Fengdong; Zhuang, Zhitao; Xu, Xinke; Gan, Yu
2015-10-01
Absolute distance measurement systems are of significant interest in the field of metrology, which could improve the manufacturing efficiency and accuracy of large assemblies in fields such as aircraft construction, automotive engineering, and the production of modern windmill blades. Frequency scanning interferometry demonstrates noticeable advantages as an absolute distance measurement system which has a high precision and doesn't depend on a cooperative target. In this paper , the influence of inevitable vibration in the frequency scanning interferometry based absolute distance measurement system is analyzed. The distance spectrum is broadened as the existence of Doppler effect caused by vibration, which will bring in a measurement error more than 103 times bigger than the changes of optical path difference. In order to decrease the influence of vibration, the changes of the optical path difference are monitored by a frequency stabilized laser, which runs parallel to the frequency scanning interferometry. The experiment has verified the effectiveness of this method.
An Analysis of the High Frequency Vibrations in Early Thematic Mapper Scenes
Kogut, J.; Larduinat, E.
1985-01-01
The motion of the mirrors in the thematic mapper (TM) and multispectral scanner (MSS) instruments, and the motion of other devices, such as the TDRSS antenna drive, and solar array drives onboard LANDSAT-4 cause vibrations to propagate through the spacecraft. These vibrations as well as nonlinearities in the scanning motion of the TM mirror can cause the TM detectors to point away from their nominal positions. Two computer programs, JITTER and SCDFT, were developed as part of the LANDSAT-D Assessment System (LAS), Products and Procedures Analysis (PAPA) program to evaluate the potential effect of high frequency vibrations on the final TM image. The maximum overlap and underlap which were observed for early TM scenes are well within specifications for the ground processing system. The cross scan and scan high frequency vibrations are also within the specifications cited for the flight system.
S-shape spring sensor: Sensing specific low-frequency vibration by energy harvesting
Zhang, Lan; Lu, Jian; Takei, Ryohei; Makimoto, Natsumi; Itoh, Toshihiro; Kobayashi, Takeshi
2016-08-01
We have developed a Si-based microelectromechanical systems sensor with high sensitivity for specific low-frequency vibration-sensing and energy-harvesting applications. The low-frequency vibration sensor contains a disk proof mass attached to two or three lead zirconate titanate (PZT) S-shape spring flexures. To obtain a faster and less expensive prototype, the design and optimization of the sensor structure are studied via finite-element method analysis. To validate the sensor structure to detect low-frequency vibration, the effects of geometrical dimensions, including the width and diameter of the S-shape spring of the proof mass, were analyzed and measured. The functional features, including the mechanical property and electrical performance of the vibration sensor, were evaluated. The results demonstrated that a very low resonant frequency of 0.2g can be typically achieved. Given a low-frequency vibration sensor with ideal performance and mass fabrication, many advanced civilian and industrial applications can be possibly realized.
S-shape spring sensor: Sensing specific low-frequency vibration by energy harvesting.
Zhang, Lan; Lu, Jian; Takei, Ryohei; Makimoto, Natsumi; Itoh, Toshihiro; Kobayashi, Takeshi
2016-08-01
We have developed a Si-based microelectromechanical systems sensor with high sensitivity for specific low-frequency vibration-sensing and energy-harvesting applications. The low-frequency vibration sensor contains a disk proof mass attached to two or three lead zirconate titanate (PZT) S-shape spring flexures. To obtain a faster and less expensive prototype, the design and optimization of the sensor structure are studied via finite-element method analysis. To validate the sensor structure to detect low-frequency vibration, the effects of geometrical dimensions, including the width and diameter of the S-shape spring of the proof mass, were analyzed and measured. The functional features, including the mechanical property and electrical performance of the vibration sensor, were evaluated. The results demonstrated that a very low resonant frequency of 0.2g can be typically achieved. Given a low-frequency vibration sensor with ideal performance and mass fabrication, many advanced civilian and industrial applications can be possibly realized. PMID:27587151
Effect of vibration frequency on agonist and antagonist arm muscle activity
Rodríguez Jiménez, Sergio; Benítez Herrera, Adolfo; García González, Miguel Ángel; Moras-Feliu, Gerard; Maffiuletti, Nicola A
2015-01-01
Purpose This study aimed to assess the effect of vibration frequency (fout) on the electromyographic (EMG) activity of the biceps brachii (BB) and triceps brachii (TB) muscles when acting as agonist and antagonist during static exercises with different loads. Methods Fourteen healthy men were asked to hold a vibratory bar as steadily as possible for 10 s during lying row (pulling) and bench press (pushing) exercise at fout of 0 (non-vibration condition), 18, 31 and 42 Hz with loads of 20, ...
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.
Wong, Werner
2013-01-01
We propose a simplest detector of harmonic vibrations with micro amplitudes and low frequencies, i.e. the detector consisting of one atomic beam. Here the atomic beam is induced by a plane harmonic wave and has a classical collective harmonic vibrations, which vibrant directions are perpendicular to the wave vectors of atomic beam. Compared with the detector consisting of atomic Mach-Zehnder interferometer, the new detector has two advantages: (1) it is suitable for the detection of the harmonic vibrations induced either by a longitudinal plane harmonic wave or by a transverse plane harmonic wave; (2) the quantum noise fluctuation of the atomic beam is exactly zero.
Structure, Anharmonic Vibrational Frequencies, and Intensities of NNHNN(+).
Yu, Qi; Bowman, Joel M; Fortenberry, Ryan C; Mancini, John S; Lee, Timothy J; Crawford, T Daniel; Klemperer, William; Francisco, Joseph S
2015-11-25
A semiglobal potential energy surface (PES) and quartic force field (QFF) based on fitting high-level electronic structure energies are presented to describe the structures and spectroscopic properties of NNHNN(+). The equilibrium structure of NNHNN(+) is linear with the proton equidistant between the two nitrogen groups and thus of D(∞h) symmetry. Vibrational second-order perturbation theory (VPT2) calculations based on the QFF fails to describe the proton "rattle" motion, i.e., the antisymmetric proton stretch, due to the very flat nature of PES around the global minimum but performs properly for other modes with sharper potential wells. Vibrational self-consistent field/virtual state configuration interaction (VSCF/VCI) calculations using a version of MULTIMODE without angular momentum terms successfully describe this motion and predict the fundamental to be at 759 cm(-1). This is in good agreement with the value of 746 cm(-1) from a fixed-node diffusion Monte Carlo calculation and the experimental Ar-tagged result of 743 cm(-1). Other VSCF/VCI energies are in good agreement with other experimentally reported ones. Both double-harmonic intensity and rigorous MULTIMODE intensity calculations show the proton-transfer fundamental has strong intensity. PMID:26529262
The Effect of the Weight Scheme on DFT Vibrational Frequencies
Bauschlicher, Charles; Ricca, Alessandra
1999-01-01
All-electron B3LYP harmonic frequencies of Ge2H5 and Ge2H6 are computed for several choices of grid and using both the Becke and the Stratmann, Scuseria, and Frisch atomic partition functions (weight scheme). For large grids, the results are independent of the weighting scheme. The lowest frequency mode is much more stable with respect to the number of grid points when the Stratmann, Scuseria, and Frisch weights are used.
Calculations of the vibrational frequency and isotopic shift of UF6 and U2F6
Zhang Yun-Guang; Zha Xin-Wei
2012-01-01
Molecular structure,vibrational frequency and infrared intensity of UF6 are investigated by using the revised Perdew-Burke-Enzerhof function with the triple-zeta polarized basis set.The calculation results are in good agreement with the experimental values and indicate the existence of a stable U2F6 molecule with a multiple bonded U2 unit.The calculation results also predict that the D3d symmetry of U2F6 is more stable than D3h.The optimized geometries,vibrational frequencies,and infrared intensities are also reported for U2F6 molecules in D3d symmetry.In addition,the isotopic shift of vibrational frequencies of the two molecules under isotopic substitution of uranium atom are also investigated with the same method.The U2F6 molecule is predicted to be better than UF6 for laser uranic isotope separation.
Application of coupled analysis methods for prediction of blast-induced dominant vibration frequency
Li, Haibo; Li, Xiaofeng; Li, Jianchun; Xia, Xiang; Wang, Xiaowei
2016-03-01
Blast-induced dominant vibration frequency (DVF) involves a complex, nonlinear and small sample system considering rock properties, blasting parameters and topography. In this study, a combination of grey relational analysis and dimensional analysis procedures for prediction of dominant vibration frequency are presented. Six factors are selected from extensive effect factor sequences based on grey relational analysis, and then a novel blast-induced dominant vibration frequency prediction is obtained by dimensional analysis. In addition, the prediction is simplified by sensitivity analysis with 195 experimental blast records. Validation is carried out for the proposed formula based on the site test database of the firstperiod blasting excavation in the Guangdong Lufeng Nuclear Power Plant (GLNPP). The results show the proposed approach has a higher fitting degree and smaller mean error when compared with traditional predictions.
Relationship of the vibrational frequency of the uranyl ion with the uranium electronegativity
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)
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.
Wike, E. L.; Wike, S. S.
1972-01-01
Seven experiments are reported on low-frequency whole-body vibration and rats' escape conditioning in a modified Skinner box. In the first three studies, conditioning was observed but was independent of frequency. In experiment four, the number of escape responses was directly related to vibration amplitude. Experiment five was a control for vibration noise and noise termination; experiments six and seven studied vibration-induced activation. Noise termination did not produce conditioning. In experiment six, subjects made more responses when responding led to termination than when it did not. In experiment seven, subjects preferred a bar which terminated vibration to one which did not.
Detailed Vibration Analysis of Pinion Gear with Time-Frequency Methods
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.
DESIGN AND ANALYSIS OF NOVEL ACTIVE ACTUATOR TO CONTROL LOW FREQUENCY VIBRATIONS OF SHAFT SYSTEM
无
2008-01-01
Aiming at providing with high-load capability in active vibration control of large-scale rotor system, a new type of active actuator to simultaneously reduce the dangers of low frequency flexural and torsional vibrations is designed. The actuator employs electro-hydraulic system and can provide a high and circumferential load. To initialize new research, the characteristics of various kinds of active actuators to control rotor shaft vibration are briefly introduced. The purpose of this paper is to introduce the preliminary results via presenting the structure, functions and operating principles, in particular, the working process of the electro-hydraulic system of the new actuator which includes a set of high speed electromagnetic valves and a series of sloping cone-shaped openings, and presenting the transmission relationships among the control parameters from control signals into the valves to active load onto shaft. The course of the work is dynamic, and a series of spatial forces and moments are put on the shaft to get an external resultant force to reduce excitations that induce vibration of shafts. By checking states of vibration, the actuator can control the impulse width and the interval of injection time for applying different control force to a vibration shaft in two circumference directions through the regulating action of a set of combination directional control valves. The results from simulating analysis and experiment show evidence of that this design can satisfy the case of active process of decreasing of flexural and torsional vibrations.
A two-degree-of-freedom spherical parallel mechanism with low-frequency vibration isolation
Xiaowei ZHANG
2016-02-01
Full Text Available Aiming at the requirements of the vibration isolation with two rotational degrees of freedom under specific conditions, a spherical 2-DOF parallel vibration isolation platform is proposed based on the theory of spherical parallel mechanism. From the view point of theory of mechanism, the operating principle is analyzed and the degree of freedom is calculated, and the virtual prototype design of vibration isolation platform is carried out. With D-H representation method of robot mechanism, the constraint equation is developed under the constraint conditions of the above link arc angle, and the inverse kinematics is realized. The kinematics positive solution process is given based on numerical method, and the solution examples of positive and inverse solution are given. Analysis and simulation results show that the 2-DOF spherical parallel mechanism proposed in this paper has the characteristics of good controllability, and the kinematic model is reasonable and effective, meeting the need of low-frequency vibration isolation performance.
Haroun, Ahmed; Yamada, Ichiro; Warisawa, Shin`ichi
2015-08-01
This paper presents study of an electromagnetic vibration energy harvesting configuration that can work effectively at low frequencies. Unlike the conventional form of vibration energy harvesters in which the mass is directly connected to a vibrating frame with spring suspension, in the proposed configuration a permanent magnet mass is allowed to move freely within a certain distance inside a frame-carrying coil and make impacts with spring end stops. The free motion distance allows matching lower vibration frequencies with an increase in the relative amplitude at resonance. Hence, significant power could be generated at low frequencies. A nonlinear mathematical model including impact and electromagnetic induction is derived. Study of the dynamic behaviour and investigation of the system performance is carried out with the aid of case study simulation. The proposed harvester shows a unique dynamic behaviour in which different ways of response of the internal relative oscillation appear over the range of input frequencies. A mathematical condition for the response type at which the higher relative amplitude appears is derived, followed by an investigation of the system resonant frequency and relative amplitude. The resonant frequency shows a dependency on the free motion distance as well as the utilized mass and spring stiffness. Simulation and experimental comparisons are carried out between the proposed harvester and similar conventional one tuned at the same input frequency. The power generated by the proposed harvesting configuration can reach more than 12 times at 11 Hz in the simulation case and about 10 times at 10 Hz in the experimental case. Simulation comparison also shows that this power magnification increases by matching lower frequencies which emphasize the advantages of the proposed configuration for low frequency operation.
Vocal fold vibrations at high soprano fundamental frequencies.
Echternach, Matthias; Döllinger, Michael; Sundberg, Johan; Traser, Louisa; Richter, Bernhard
2013-02-01
Human voice production at very high fundamental frequencies is not yet understood in detail. It was hypothesized that these frequencies are produced by turbulences, vocal tract/vocal fold interactions, or vocal fold oscillations without closure. Hitherto it has been impossible to visually analyze the vocal mechanism due to technical limitations. Latest high-speed technology, which captures 20,000 frames/s, using transnasal endoscopy was applied. Up to 1568 Hz human vocal folds do exhibit oscillations with complete closure. Therefore, the recent results suggest that human voice production at very high F0s up to 1568 Hz is not caused by turbulence, but rather by airflow modulation from vocal fold oscillations. PMID:23363198
Distributed vibration sensing with time-resolved optical frequency-domain reflectometry.
Zhou, Da-Peng; Qin, Zengguang; Li, Wenhai; Chen, Liang; Bao, Xiaoyi
2012-06-01
The distributed vibration or dynamic strain information can be obtained using time-resolved optical frequency-domain reflectometry. Time-domain information is resolved by measuring Rayleigh backscatter spectrum in different wavelength ranges which fall in successive time sequence due to the linear wavelength sweep of the tunable laser source with a constant sweeping rate. The local Rayleigh backscatter spectrum shift of the vibrated state with respect to that of the non-vibrated state in time sequence can be used to determine dynamic strain information at a specific position along the fiber length. Standard single-mode fibers can be used as sensing head, while the measurable frequency range of 0-32 Hz with the spatial resolution of 10 cm can be achieved up to the total length of 17 m. PMID:22714342
Landmann, A. E.; Tillema, H. F.; Macgregor, G. R.
1992-01-01
Finite element analysis (FEA), statistical energy analysis (SEA), and a power flow method (computer program PAIN) were used to assess low frequency interior noise associated with advanced propeller installations. FEA and SEA models were used to predict cabin noise and vibration and evaluate suppression concepts for structure-borne noise associated with the shaft rotational frequency and harmonics (less than 100 Hz). SEA and PAIN models were used to predict cabin noise and vibration and evaluate suppression concepts for airborne noise associated with engine radiated propeller tones. Both aft-mounted and wing-mounted propeller configurations were evaluated. Ground vibration test data from a 727 airplane modified to accept a propeller engine were used to compare with predictions for the aft-mounted propeller. Similar data from the 767 airplane was used for the wing-mounted comparisons.
Andryushkevichyus, A. I.; Ragulskis, K. M.
1973-01-01
Torsional vibration systems, with finite numbers of degrees of freedom are investigated. In designing such systems, it is important to select parameters, so that the frequency spectrum of the natural vibrations is beyond the limits of the resonance danger region. In the case when the system has a large number of degrees of freedom, calculation of its natural frequencies, as well as tuning out the resonance danger zones is laborious. When the system being investigated has one group symmetry or another, solution of the problem mentioned above is facilitated, as a consequence of breaking down the frequency equations into several, which are smaller in size. An algorithm is given for tuning out the natural frequency spectrum from the forbidden region, by means of varying the rigidity of systems having group symmetries or group quasi-symmetries.
A New Ultra-low Frequency Passive Vertical Vibration Isolation System
赵鹏飞; 黄玉盈; 唐孟希
2002-01-01
A new ultra-low frequency passive vertical vibration isolation system is constructed by connecting the torsion spring isolator with a reverse pendulum. The theoretical analysis shows that the new system can achieve a much longer resonant period and have a smaller size than the current torsion spring isolators with the same geometric parameters.
Vibration frequencies for searches of free triatomic molecules in interstellar space
More and more cold interstellar molecules are being discovered, the majority of them being organic. Perhaps it is time to consider the numerous small molecules that also await observation. We report progress in tabulating symmetric-stretch vibration frequencies for neutral main-group ground-state triatomic molecules, formed from period-2 atoms, which are not yet studied
SHIFTS IN ADSORBATE VIBRATIONAL FREQUENCIES DUE TO INTERNAL ELECTRIC-FIELDS
BAGUS, PS; ILLAS, F
1994-01-01
A new physical mechanism is proposed to explain the shifts in vibrational frequency of negatively adsorbed species on a metal surface. Ab initio cluster model calculations for NO adsorbed Dn Ag(111) in two different orientations, N-down and O-down, suggest that the low-coverage HREELS peak appearing
Accurate calculation of vibrational frequencies using explicitly correlated coupled-cluster theory.
Rauhut, Guntram; Knizia, Gerald; Werner, Hans-Joachim
2009-02-01
The recently proposed explicitly correlated CCSD(T)-F12x (x = a,b) approximations [T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106 (2007)] are applied to compute equilibrium structures and harmonic as well as anharmonic vibrational frequencies for H(2)O, HCN, CO(2), CH(2)O, H(2)O(2), C(2)H(2), CH(2)NH, C(2)H(2)O, and the trans-isomer of 1,2-C(2)H(2)F(2). Using aug-cc-pVTZ basis sets, the CCSD(T)-F12a equilibrium geometries and harmonic vibrational frequencies are in very close agreement with CCSD(T)/aug-cc-pV5Z values. The anharmonic frequencies are evaluated using vibrational self-consistent field and vibrational configuration interaction methods based on automatically generated potential energy surfaces. The mean absolute deviation of the CCSD(T)-F12a/aug-cc-pVTZ anharmonic frequencies from experimental values amounts to only 4.0 cm(-1). PMID:19206956
Research on a new type of precision cropping method with variable frequency vibration
无
2007-01-01
Aiming at the cropping operations widely applied in practical industry production, a new method of bar cropping is presented. The rotational speeds of actuating motor of eccentric blocks are controlled by a frequency-changer, and the shearing die provides the bar with the controllable force, frequency and amplitude of vibration. By utilizing the stress concentration at the bottom of V shape groove on the bar, the low stress bar cropping is realized. The bar cropping experiments of duralumin alloy and steel ...
Low-frequency elastic vibrations localized near fracture in solid
We propose a consistent macroscopic description of the thermodynamic and dynamical properties of two-dimensional surface layers on the interface between two crystals or between different media. Such description enables one to elucidate the effect of two-dimensional defects (fracture) on the frequency, dispersion and polarization characteristics of surface waves and scattered on two-dimensional defects bulk waves of various nature, starting from rather general assumptions and without using of the microscopic models of surface or interface layers. A new thermodynamic variable for two-dimensional defect with an internal dynamical degree of freedom is introduced. The coupled long-wavelength and low-frequency equations of motion of the defect layer are obtained as a set of nontraditional boundary conditions for the bulk equations of the theory of elasticity. New types of surface and pseudo-surface (resonance) waves caused by two-dimensional absorbed or segregated layers with different strength of bonding with elastic substrate are analyzed. (author). 31 refs, 4 figs
Zhang, Libing; Lu, Zhou; Velarde Ruiz Esparza, Luis A.; Fu, Li; Pu, Yunqiao; Ding, Shi-You; Ragauskas, Art J.; Wang, Hongfei; Yang, Bin
2015-06-01
Here we reported the first sub-wavenumber high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) study on both the C-H and O-H region spectra of crystalline cellulose. HR-BB-SFG-VS has about 10 times better resolution than the conventional scanning SFG-VS and is known to be able to measure the intrinsic spectral lineshape and to resolve much more spectral details. With HR-BB-SFG-VS, we found that in cellulose from different sources, including Avicel and cellulose crystals isolated from algae Valonia (Iα) and tunicates (Iβ), the spectral signatures in the OH regions were unique for different allomorphs, i.e. Iα and Iβ, while the spectral signatures in the C-H regions varied in all samples examined. Even though the origin of the different behaviors of the crystalline cellulose in the O-H and C-H vibrational frequency regions is yet to be correlated to the structure of cellulose, these results provided new spectroscopic methods and opportunities to classify and understand the basic crystalline structure, as well as variations, in polymorphism of the crystalline cellulose structure.
A hybrid electromagnetic energy harvesting device for low frequency vibration
Jung, Hyung-Jo; Kim, In-Ho; Min, Dong Yi; Sim, Sung-Han; Koo, Jeong-Hoi
2013-04-01
An electromagnetic energy harvesting device, which converts a translational base motion into a rotational motion by using a rigid bar having a moving mass pivoted on a hinged point with a power spring, has been recently developed for use of civil engineering structures having low natural frequencies. The device utilizes the relative motion between moving permanent magnets and a fixed solenoid coil in order to harvest electrical power. In this study, the performance of the device is enhanced by introducing a rotational-type generator at a hinged point. In addition, a mechanical stopper, which makes use of an auxiliary energy harvesting part to further improve the efficiency, is incorporated into the device. The effectiveness of the proposed hybrid energy harvesting device based on electromagnetic mechanism is verified through a series of laboratory tests.
Improving harmonic vibrational frequencies calculations in density functional theory
Stratmann, R. Eric; Burant, John C.; Scuseria, Gustavo E.; Frisch, Michael J.
1997-06-01
Using a previously introduced weight scheme, microbatching, and grid compression [R. E. Stratmann, G. E. Scuseria and M. J. Frisch, Chem. Phys. Lett. 257, 213 (1996)], we significantly speed up the numerical integration of the exchange-correlation contribution to the Coupled-Perturbed Kohn-Sham equations. In addition, we find that the nature of the integrand is such that it is possible to employ substantially fewer grid points in the quadrature and to use the Gaussian very Fast Multipole Method (GvFMM) with very short multipole expansions for the Coulomb contribution, with negligible loss in accuracy. As a representative example, the computational demand for the exchange-correlation portion of a coronene (C24H12) frequency calculation with a 3-21G basis is reduced by more than one order of magnitude. The overall speed up achieved in this calculation is between a factor of 4 to 6, depending on the specific functional. We also present sample calculations using polarized bases, gradient-corrected functionals, and on even larger systems (C54H18 and C96H24), to illustrate the various effects and improvements that we have accomplished.
Two-dimensional resonance frequency tuning approach for vibration-based energy harvesting
Dong, Lin; Prasad, M. G.; Fisher, Frank T.
2016-06-01
Vibration-based energy harvesting seeks to convert ambient vibrations to electrical energy and is of interest for, among other applications, powering the individual nodes of wireless sensor networks. Generally it is desired to match the resonant frequencies of the device to the ambient vibration source to optimize the energy harvested. This paper presents a two-dimensionally (2D) tunable vibration-based energy harvesting device via the application of magnetic forces in two-dimensional space. These forces are accounted for in the model separately, with the transverse force contributing to the transverse stiffness of the system while the axial force contributes to a change in axial stiffness of the beam. Simulation results from a COMSOL magnetostatic 3D model agree well with the analytical model and are confirmed with a separate experimental study. Furthermore, analysis of the three possible magnetization orientations between the fixed and tuning magnets shows that the transverse parallel magnetization orientation is the most effective with regards to the proposed 2D tuning approach. In all cases the transverse stiffness term is in general significantly larger than the axial stiffness contribution, suggesting that from a tuning perspective it may be possible to use these stiffness contributions for coarse and fine frequency tuning, respectively. This 2D resonant frequency tuning approach extends earlier 1D approaches and may be particularly useful in applications where space constraints impact the available design space of the energy harvester.
Anelise Sonza; Robinson, Caroline C.; Matilde Achaval; Milton A. Zaro
2015-01-01
The aim of this study was to investigate the effects of whole body vibration (WBV) on physiological parameters, cutaneous temperature, tactile sensitivity, and balance. Twenty-four healthy adults (25.3 ± 2.6 years) participated in four WBV sessions. They spent 15 minutes on a vibration platform in the vertical mode at four different frequencies (31, 35, 40, and 44 Hz) with 1 mm of amplitude. All variables were measured before and after WBV exposure. Pressure sensation in five anatomical regio...
Analysis of Frequency Spectrum of Laser-Induced Vibration of Microbeam Resonators
FANG Dai-Ning; SUN Yu-xin; SOH Ai-Kah
2006-01-01
The vibration phenomenon during pulsed laser heating of micro-beams is investigated.The beam is made of silicon and js heated by a laser pulse with a non-Gaussian temporal profile and with an ultrashort pulse duration of 2ps.which incites vibration due to the thermoelastic damping effect.This coupled thermoelastic problem is solved using an analytical-numerical technique based on the Laplace transformation.The damping ratio and resonant frequency shift ratio of beams due t0 the air damping effect and the thermoelastic damping ettect are also examined and discusssed.
Non-linear Vibration of Oscillation Systems using Frequency-Amplitude Formulation
Fereidoon, A.; Ghadimi, M.; Barari, Amin; Kaliji, H. D.; Domairry, G.
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....
Cuisset, Arnaud; Drumel, Marie-Aline Martin; Hindle, Francis; Mouret, Gaël; Sadovskií, Dmitrií A.
2013-10-01
We report on the successful extended analysis of the high-frequency (200-700 GHz) part of the gas phase (sub)mm-wave spectra of dimethylsulfoxide (DMSO). The spectrum was recorded at 100 kHz resolution using a solid state subTHz spectrometer. The five lowest energy fundamental vibrational states of DMSO with frequencies below 400 cm-1 were observed as sidebands along with the main 0←0 band. Neglecting the internal rotation of methyls, our rotational Hamiltonian reproduced the spectrum to the subMHz accuracy. We have found that the asymmetric bending state ν23 is the only low frequency fundamental vibrational state with the "anomalous" rotational structure uncovered in Cuisset et al. [1]. dmsomw 2013-09-04 15:03
Multi-frequency vibration-driven electret generator for wireless sensor applications
We had reported the power output enhancement of an electret harvester and the operation of wireless sensor modules only on electricity from our electret harvester[1]. Since vibration is random and irregular in actual fields, there is the issue that power output of vibration harvesters can't be obtained outside the range of frequencies designed to resonate the inner mass. As a way to solve, we fabricated four electret harvesters tuned to different resonant frequencies only by assembling different springs and weights, and developed voltage conversion circuits with 73% efficiency from 70V AC to 3.6V DC. We demonstrated to obtain stable DC power output at a broad range of frequencies from 27.6Hz to 30.6Hz by combining the four electret harvesters and voltage conversion circuits
Low-frequency band gap mechanism of torsional vibration of lightweight elastic metamaterial shafts
Li, Lixia; Cai, Anjiang
2016-07-01
In this paper, the low-frequency band gap mechanism of torsional vibration is investigated for a kind of light elastic metamaterial (EM) shafts architecture comprised of a radial double-period element periodically as locally resonant oscillators with low frequency property. The dispersion relations are calculated by a method combining the transfer matrix and a lumped-mass method. The theoretical results agree well with finite method simulations, independent of the density of the hard material ring. The effects of the material parameters on the band gaps are further explored numerically. Our results show that in contrast to the traditional EM shaft, the weight of our proposed EM shaft can be reduced by 27% in the same band gap range while the vibration attenuation is kept unchanged, which is very convenient to instruct the potential engineering applications. Finally, the band edge frequencies of the lower band gaps for this light EM shaft are expressed analytically using physical heuristic models.
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.
Theory and experiment research for ultra-low frequency maglev vibration sensor
Zheng, Dezhi; Liu, Yixuan; Guo, Zhanshe; Zhao, Xiaomeng; Fan, Shangchun
2015-10-01
A new maglev sensor is proposed to measure ultra-low frequency (ULF) vibration, which uses hybrid-magnet levitation structure with electromagnets and permanent magnets as the supporting component, rather than the conventional spring structure of magnetoelectric vibration sensor. Since the lower measurement limit needs to be reduced, the equivalent bearing stiffness coefficient and the equivalent damping coefficient are adjusted by the sensitivity unit structure of the sensor and the closed-loop control system, which realizes both the closed-loop control and the solving algorithms. A simple sensor experimental platform is then assembled based on a digital hardware system, and experimental results demonstrate that the lower measurement limit of the sensor is increased to 0.2 Hz under these experimental conditions, indicating promising results of the maglev sensor for ULF vibration measurements.
Theory and experiment research for ultra-low frequency maglev vibration sensor
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.
Experimental research on anti-vibration interferometry based on time-frequency-domain analysis
Hu, Yao; Hao, Qun; Zhang, Fanghua; Tian, Yuhan
2013-10-01
Phase-shifting interferometry is a non-contact precision precise measuring method for optical surface, but it is highly sensitive to external vibrations. A time-and-frequency-domain (TFD) anti-noise phase-shifting interferometry is proposed to eliminate the effect of vibrations and improve the precision of measurement. According to simulations and preliminary experiments, active phase-shifting speed as well as interferogram capture speed should be increased to improve the anti-vibration capability of the TFD method. In this paper, a fast phase-shifting approach based on PZT actuator and interferogram detection with high-speed camera is proposed. Preliminary experimental results are given to demonstrate the approach.
Using a surface piezoresistor diffusion method and front-side only micromachining process, a planar piezoresistive vibration sensor was successfully developed with a simple structure, lower processing cost and fewer packaging difficulties. The vibration sensor had a large sector proof mass attached to a narrow flexure. Optimization of the boron diffusion piezoresistor placed on the edge of the narrow flexure greatly improved the sensitivity. Planar vibration sensors were fabricated and measured in order to analyze the effects of the sensor dimensions on performance, including the values of flexure width and the included angle of the sector. Sensitivities of fabricated planar sensors of 0.09–0.46 mV/V/g were measured up to a test frequency of 60 Hz. The sensor functioned at low voltages (<3 V) and currents (<1 mA) with a high sensitivity and low drift. At low background noise levels, the sensor had performance comparable to a commercial device
Combined Amplitude and Frequency Measurements for Non-Contacting Turbomachinery Blade Vibration
Platt, Michael J. (Inventor); Jagodnik, John J. (Inventor)
2013-01-01
A method and apparatus for measuring the vibration of rotating blades, such as turbines, compressors, fans, or pumps, including sensing the return signal from projected energy and/or field changes from a plurality of sensors mounted on the machine housing. One or more of the sensors has a narrow field of measurement and the data is processed to provide the referenced time of arrival of each blade, and therefore the blade tip deflection due to vibration. One or more of the sensors has a wide field of measurement, providing a time history of the approaching and receding blades, and the data is processed to provide frequency content and relative magnitudes of the active mode(s) of blade vibration. By combining the overall tip deflection magnitude with the relative magnitudes of the active modes, the total vibratory stress state of the blade can be determined.
Theory and experiment research for ultra-low frequency maglev vibration sensor
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
Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment. (paper)
Lee, Jungshin; Rhim, Jaewook
2012-09-01
Differential vibrating accelerometer (DVA) is a resonant-type sensor which detects the change in the resonant frequency in the presence of acceleration input, i.e. inertial loading. However, the resonant frequency of micromachined silicon resonators is sensitive to the temperature change as well as the input acceleration. Therefore, to design a high-precision vibrating accelerometer, the temperature sensitivity of the resonant frequency has to be predicted and compensated accurately. In this study, a temperature compensation method for resonant frequency is proposed which controls the electrostatic stiffness of the dual-ended tuning fork (DETF) using the temperature-dependent dc voltage between the parallel plate electrodes. To do this, the electromechanical model is derived first to predict the change in the electrostatic stiffness and the resonant frequency resulting from the dc voltage between the resonator and the electrodes. Next, the temperature sensitivity of the resonant frequency is modeled, estimated and compared with the measured values. Then it is shown that the resonant frequency of the DETF can be kept constant in the operating temperature range by applying the temperature-dependent driving voltage to the parallel plate electrodes. The proposed method is validated through experiment.
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.
Effect of High-Frequency Vertical Vibration of Track on Formation and Evolution of Corrugations
金学松; 温泽峰; 王开云; 张卫华
2004-01-01
The effect of high-frequency curved track vibrations in the vertical direction on the formation and development of rail corrugation was analyzed.Kalker's non-Hertzian rolling contact theory was modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling when a wheelset is steadily curving.The material loss unit area was assumed to be proportional to the frictional work density to determine the wear depth of the contact surface of the rail.The combined influences of the corrugation and the coupled dynamics of the railway vehicle and track were taken into consideration in the numerical simulation.For simplicity, the model considered one fourth of freight car without lateral motion, namely, a wheelset and the equivalent one fourth freight car body above it.The Euler beam was used to model the rails with the track structure under the rails replaced with equivalent springs, dumpers, and mass bodies.The numerical results show that the high-frequency track vibration causes formation of the initial corrugation on the smooth contact surface of the rail when a wheelset is steadily curving.The corrugation wave length depends on the frequencies and the rolling speed of the wheelset.The vibration frequencies also affect the depth and increase the corrugation.
Effect of vehicle weight on natural frequencies of bridges measured from traffic-induced vibration
无
2003-01-01
Recently, ambient vibration test (AVT) is widely used to estimate dynamic characteristics of large civil structures. Dynamic characteristics can be affected by various environmental factors such as humidity, intensity of wind, and temperature. Besides these environmental conditions, the mass of vehicles may change the measured values when traffic-induced vibration is used as a source of AVT for bridges. The effect of vehicle mass on dynamic characteristics is investigated through traffic-induced vibration tests on three bridges; (1) three-span suspension bridge (128m+404m+128m), (2) five-span continuous steel box girder bridge (59m+3@95m+59m), (3) simply supported plate girder bridge (46m). Acceleration histories of each measurement location under normal traffic are recorded for 30 minutes at field. These recorded histories are divided into individual vibrations and are combined into two groups according to the level of vibration; one by heavy vehicles such as trucks and buses and the other by light vehicles such as passenger cars. Separate processing of the two groups of signals shows that, for the middle and long-span bridges, the difference can be hardly detected, but, for the short span bridges whose mass is relatively small, the measured natural frequencies can change up to 5.4%.
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.
Zhao, Nian; Yang, Jin; Yu, Qiangmo; Zhao, Jiangxin; Liu, Jun; Wen, Yumei; Li, Ping
2016-01-01
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. PMID:26827346
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
An Accurate Quartic Force Field and Vibrational Frequencies for HNO and DNO
Dateo, Christopher E.; Lee, Timothy J.; Schwenke, David W.
1994-01-01
An accurate ab initio quartic force field for HNO has been determined using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, CCSD(T), in conjunction with the correlation consistent polarized valence triple zeta (cc-pVTZ) basis set. Improved harmonic frequencies were determined with the cc-pVQZ basis set. Fundamental vibrational frequencies were determined using a second-order perturbation theory analysis and also using variational calculations. The N-0 stretch and bending fundamentals are determined well from both vibrational analyses. The H-N stretch, however, is shown to have an unusually large anharmonic correction, and is not well determined using second-order perturbation theory. The H-N fundamental is well determined from the variational calculations, demonstrating the quality of the ab initio quartic force field. The zero-point energy of HNO that should be used in isodesmic reactions is also discussed.
Low frequency noise and vibrations measurements at a modern wind farm
Low frequency noise and vibration levels at a modern wind farm have been measured at distances up to 1km. Noise and vibration levels have been found to comply with recommended residential criteria even on the wind turbine site itself and the acoustic signal is below accepted thresholds of perception below 20 Hz. Nevertheless low level infrasonic, periodic noise from the windfarm may occasionally be detected by instrumentation at distances up to 1 km, despite other sources of noise. Subjective detection of the wind turbines may also be just apparent at this distance but is due to higher frequency components. A greater knowledge of building sound transmission functions would be useful in assessing the effects of both audible and infrasonic noise inside dwellings. (author)
Tomono, Yuzo; Takaoka, Tosihide; Yajima, Masaaki; Tanokura, Yosiko; Jinda, Nan
1990-02-01
Temperature dependence of three infrared active modes of vibrations were measured for KNiF3 powdered specimen. A characteristic temperature dependence was observed for the highest mode, which is about 450 cm-1, at room temperature. This mode is due to a bending motion of F-Ni-F bond, which is expected to modulate superexchange interaction between nearest neighboring Ni ions. Therefore the anomalous increase of the highest mode frequency was interpreted by superexchange interaction, which increases at lower temperatures.
Akhtyamov, A. M.; Utyashev, I. M.
2015-11-01
The form and parameters of boundary conditions are identified for the boundary-value problem of string vibrations. It is shown that, to identify both the form and parameters of boundary conditions, two natural frequencies are sufficient. The correctness set of the given problem is determined, and its well-posedness according to Tikhonov is proved. Based on the proven theorem, a method of finding approximate solutions is proposed.
Sum-Frequency Vibrational Spectroscopic Study of a Rubbed Polymer Surface
Wei, Xing; Zhuang, Xiaowei; Hong, Seok-Cheol; Goto, Tomohisa; Shen, Y. R.
1999-05-01
Sum-frequency vibrational spectroscopy has been used to probe the chain orientation of polyvinyl alcohol at the surface after rubbing. The distribution function of the chain orientation is determined quantitatively. The orientational order parameter of the chains deduced from the distribution matches well with that of a liquid crystal monolayer deposited on the polymer, proving that the polymer surface can align a liquid crystal film through orientational epitaxy.
CALCULATION OF ELASTICITY MATERIAL CONSTANTS BY OWN VIBRATION FREQUENCY OF ROUND PLATE
V. T. Minchenya; D. A. Stepanenko; E. N. Yurchik
2014-01-01
The paper analyses existing methods for determination of elastic material properties and reveals perspectives for usage of resonant methods which make it possible to execute a non-contact and non-destructive control. As an example of a resonant method application a problem on determination of elastic material properties by own vibration frequency of a specimen in the form of a round plate is considered in the paper. Solution efficiency of the investigated problem using a gradient-search metho...
Low-frequency interlayer vibration modes in two-dimensional layered materials
Ji, Jianting; Dong, Shan; Zhang, Anmin; Zhang, Qingming
2016-06-01
Two-dimensional (2D) layered materials have been attracted tremendous research interest because of their novel photoelectric properties. If a single atomic layer instead of individual atoms is taken as a rigid motion object, two unique interlayer vibrations, i.e. compression/breathing and shear motions, at ultra-low frequencies can be expected and actually have been observed in many layered materials. The vibrations stem from the interlayer van der Waals interaction and can be well described by a conventional linear-chain model in most cases. The vibration frequencies strongly depend on layer thickness, which enables an accurate determination of layer numbers. A quick and nondestructive determination of flake thickness is particularly important for the materials, since the physical properties can be dramatically changed in the cases of several atomic layers. As a measure of interlayer coupling, the low-frequency modes are also sensitive to the stacking methods of atomic layers and the overlapping of different kinds of 2D materials. This allows the modes to play a key role in the applications like van der Waals heterojunctions. In this paper, we will give a brief review on the experimental observations and theoretical understanding of the interlayer modes in several typical 2D systems, as well as their actual and potential applications.
Haghshenas, Javad
2015-09-01
Performance of high resolution remote sensing payloads is often limited due to satellite platform vibrations. Effects of Linear and high frequency vibrations on the overall MTF are known exactly in closed form but the low frequency vibration effect is a random process and must be considered statistically. It should be considered in system level payload designing to know whether or not the overall MTF is limited by the vibration blur radius. Usually the vibration MTF budget is defined based on the mission requirements and the overall MTF limitations. With a good understanding of harmful vibration frequencies and amplitudes in the system preliminary design phase, their effects could be removed totally or partially. This procedure is cost effective and let designer to just eliminate the harmful vibrations and avoids over-designing. In this paper we have analyzed the effects of low-frequency platform vibrations on the payload's modulation transfer function. We have used a statistical analysis to find the probability of imaging with a MTF greater or equal to a pre-defined budget for different missions. After some discussions on the worst and average cases, we have proposed some "look-up figures" which would help the remote sensing payload designers to avoid the vibration effects. Using these figures, designer can choose the electro-optical parameters in such a way, that vibration effects be less than its pre-defined budget. Furthermore, using the results, we can propose a damping profile based on which vibration frequencies and amplitudes must be eliminated to stabilize the payload system.
We present a low frequency vibration driven 2-DOF piezoelectric energy harvester with increased performance, in terms of both bandwidth and output power, by mechanical impact. It consists of two series spring-mass systems (positioned in a parallel manner) one of which responds to low frequency vibration, engages with the harvester base stopper periodically by piecewise linear impact, and transfers a secondary shock to the second spring- mass system comprising of power generating element. It introduces a non-linear frequency up- conversion mechanism which, in turn, generates increased output power within a wide range of applied frequency. A 2-DOF prototype harvester without stopper shows two narrow resonant peaks and delivers maximum 2.11μW peak power to its matched load resistance at 17Hz frequency and 0.5g acceleration. On the other hand, it offers a -3dB bandwidth of 15Hz (9Hz- 24Hz) and delivers maximum 202.4μW peak power to its matched load resistance at the same operating condition when a stopper is placed below the primary mass at 0.5mm distance. Generated power increases up to 449μW as the acceleration increases to 1g
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.
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.
Zhu, Bo; Zhao, Hongwei; Zhao, Dan; Zhang, Peng; Yang, Yihan; Han, Lei; Kui, Hailin
2016-03-01
It has always been a critical issue to understand the material removal behavior of Vibration-Assisted Machining (VAM), especially on atomic level. To find out the effects of vibration frequency on material removal response, a three-dimensional molecular dynamics (MD) model has been established in this research to investigate the effects of scratched groove, crystal defects on the surface quality, comparing with the Von Mises shear strain and tangential force in simulations during nano-scratching process. Comparisons are made among the results of simulations from different vibration frequency with the same scratching feed, depth, amplitude and crystal orientation. Copper potential in this simulation is Embedded-Atom Method (EAM) potential. Interaction between copper and carbon atoms is Morse potential. Simulational results show that higher frequency can make groove smoother. Simulation with high frequency creates more dislocations to improve the machinability of copper specimen. The changing frequency does not have evident effects on Von Mises shear strain. Higher frequency can decrease the tangential force to reduce the consumption of cutting energy and tool wear. In conclusion, higher vibration frequency in VAM on mono-crystalline copper has positive effects on surface finish, machinablility and tool wear reduction.
Vibration modal frequency measurement of a turbine blade was investigated by using fiber Bragg grating (FBG) sensors for their adaptation for a low level of strain at high frequency. However, the signal-to-noise ratio was so low that it was very difficult to identify dominant modal frequency from a raw signal acquired. An attempt was made to solve this problem. First, a bi-linear transform elliptic filter with pass-band and stop-band was proposed to remove electromagnetic interference noise. Second, discrete stationary wavelet transform with a soft threshold was utilized to de-noise the high-frequency part. Third, wavelet packet transform was exploited to decompose the time signal and to obtain the power spectrum and identification of dominant modal frequency. Experimental and analytic results demonstrated that four stages of dominant modal frequencies of the turbine blade without any constraint condition (free vibration) and three stages of dominant modal frequencies with a constraint condition (A-type vibration) were obtained, respectively. To testify to the validity of analytic results, a professional computer random signal and vibration analysis system (CRAS) was used to measure modal frequency. The results illustrated that modal frequencies obtained by the CRAS platform yielded close agreement with those based on FBG sensors. Obviously, wavelet analysis is successfully employed to decode vibration modal frequency from a raw signal of FBG sensors
An automated fringe counting laser interferometer for low frequency vibration measurements
Payne, B. F.; Federman, Charles
Low-frequency accelerometers and velocity transducers are widely used to investigate vibrations on structures such as buildings, bridges, aircraft, ships, power plant equipment, and in seismic applications. Previous work at NBS in this area has focused on the development of accurate calibration methods for transducers by optical methods in the frequency range of 2-100 Hz. This paper describes a computer-controlled fringe-counting interferometric system for transducer calibration. The calibration system uses digital signal analysis for accurate low-frequency voltage measurements. The measurement procedures are fully automated, with menu-driven programs using the computer soft keys for controlling the test frequencies and acceleration, setting test parameters, collecting and storing data and producing reports and graphs. An error analysis is given and experimental data are presented for a typical transducer calibrated on this system.
Ye, Ying; Griffin, Michael J.
2014-01-01
Purpose: this study investigated how the vasoconstriction induced by vibration depends on the frequency of vibration when the vibration magnitude is defined by individual thresholds for perceiving vibration [i.e. sensation levels (SL)]. Methods: fourteen healthy subjects attended the laboratory on seven occasions: for six vibration frequencies (8, 16, 31.5, 63, 125, or 250 Hz) and a static control condition. Finger blood flow (FBF) was measured in the middle fingers of both hands at 30-se...
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.
Toshiki Yamada
2014-11-01
Full Text Available 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.
Design of piezoelectric MEMS cantilever for low-frequency vibration energy harvester
Takei, Ryohei; Makimoto, Natsumi; Okada, Hironao; Itoh, Toshihiro; Kobayashi, Takeshi
2016-06-01
We report the design of piezoelectric MEMS cantilevers formed on a silicon-on-insulator wafer to efficiently harvest electrical power from harmonic vibration with a frequency of approximately 30 Hz. Numerical simulation indicates that a >4-µm-thick top silicon layer and >3-µm-thick piezoelectric film are preferable to maximize the output electrical power. An in-plane structure of the cantilever is also designed retaining the footprint of the cantilever. The simulation results indicate that the output power is maximized when the length ratio of the proof mass to the cantilever beam is 1.5. To ensure the accuracy of the simulation, we fabricated and characterized cantilevers with a 10-µm-thick top silicon layer and a 1.8-µm-thick piezoelectric film, resulting in 0.21 µW at a vibration of 0.5 m/s2 and 25.1 Hz. The measured output power is in agreement with the simulated value, meaning that the design is significantly reliable for low-frequency vibration energy harvesters.
Electron transfer reaction in the Marcus inverted region: Role of high frequency vibrational modes
A theoretical study of the dynamics of photo-electron transfer reactions in the Marcus inverted regime is presented. This study is motivated partly by the recent proposal of Barbara et al. (J. Phys. Chem. 96, 3728, 1991) that a minimal model of an electron transfer reaction should consist of a polar solvent mode (X), a low frequency vibrational mode (Q) and one high frequency mode (q). Interplay between these modes may be responsible for the crossover observed in the dynamics from a solvent controlled to a vibrational controlled electron transfer. The following results have been obtained. (i) In the case of slowly relaxing solvents, the proximity of the point of excitation to an effective sink on the excited surface is critical in determining the decay of the reactant population. This is because the Franck-Condon overlap between the reactant ground and the product excited states decreases rapidly with increase in the quantum number of the product vibrational state. (ii) Non-exponential solvation dynamics has an important effect in determining the rates of electron transfer. Especially, a biphasic solvation and a large coupling between the reactant and the product states both may be needed to explain the experimental results
Palagummi, S.; Yuan, F. G.
2016-04-01
This article identifies and studies key parameters that characterize a horizontal diamagnetic levitation (HDL) mechanism based low frequency vibration energy harvester with the aim of enhancing performance metrics such as efficiency and volume figure of merit (FoMv). The HDL mechanism comprises of three permanent magnets and two diamagnetic plates. Two of the magnets, aka lifting magnets, are placed co-axially at a distance such that each attract a centrally located magnet, aka floating magnet, to balance its weight. This floating magnet is flanked closely by two diamagnetic plates which stabilize the levitation in the axial direction. The influence of the geometry of the floating magnet, the lifting magnet and the diamagnetic plate are parametrically studied to quantify their effects on the size, stability of the levitation mechanism and the resonant frequency of the floating magnet. For vibration energy harvesting using the HDL mechanism, a coil geometry and eddy current damping are critically discussed. Based on the analysis, an efficient experimental system is setup which showed a softening frequency response with an average system efficiency of 25.8% and a FoMv of 0.23% when excited at a root mean square acceleration of 0.0546 m/s2 and at frequency of 1.9 Hz.
Composite 3D-printed metastructures for low-frequency and broadband vibration absorption.
Matlack, Kathryn H; Bauhofer, Anton; Krödel, Sebastian; Palermo, Antonio; Daraio, Chiara
2016-07-26
Architected materials that control elastic wave propagation are essential in vibration mitigation and sound attenuation. Phononic crystals and acoustic metamaterials use band-gap engineering to forbid certain frequencies from propagating through a material. However, existing solutions are limited in the low-frequency regimes and in their bandwidth of operation because they require impractical sizes and masses. Here, we present a class of materials (labeled elastic metastructures) that supports the formation of wide and low-frequency band gaps, while simultaneously reducing their global mass. To achieve these properties, the metastructures combine local resonances with structural modes of a periodic architected lattice. Whereas the band gaps in these metastructures are induced by Bragg scattering mechanisms, their key feature is that the band-gap size and frequency range can be controlled and broadened through local resonances, which are linked to changes in the lattice geometry. We demonstrate these principles experimentally, using advanced additive manufacturing methods, and inform our designs using finite-element simulations. This design strategy has a broad range of applications, including control of structural vibrations, noise, and shock mitigation. PMID:27410042
Zhang, Fanghua; Hao, Qun; Hu, Yao; Zhu, Qiudong
2012-11-01
This paper introduces a time-and-frequency-domain (TFD) anti-noise phase-shifting interferometry, and designs an experimental system to test the anti-vibration ability of this method. In the system, a plane mirror is measured under the external vibrations simulated by the standard mirror propelled by PZT. During the measurement, each of the key parameters is assigned different values. By analyzing the testing results, the law of the parameters' influence on system anti-vibration capability can be obtained. According to the law, the optimization parameters can be determined so that the system has the maximum anti- vibration capability.
Topology optimization and fabrication of low frequency vibration energy harvesting microdevices
Topological design of miniaturized resonating structures capable of harvesting electrical energy from low frequency environmental mechanical vibrations encounters a particular physical challenge, due to the conflicting design requirements: low resonating frequency and miniaturization. In this paper structural static stiffness to resist undesired lateral deformation is included into the objective function, to prevent the structure from degenerating and forcing the solution to be manufacturable. The rational approximation of material properties interpolation scheme is introduced to deal with the problems of local vibration and instability of the low density area induced by the design dependent body forces. Both density and level set based topology optimization (TO) methods are investigated in their parameterization, sensitivity analysis, and applicability for low frequency energy harvester TO problems. Continuum based variation formulations for sensitivity analysis and the material derivative based shape sensitivity analysis are presented for the density method and the level set method, respectively; and their similarities and differences are highlighted. An external damper is introduced to simulate the energy output of the resonator due to electrical damping and the Rayleigh proportional damping is used for mechanical damping. Optimization results for different scenarios are tested to illustrate the influences of dynamic and static loads. To demonstrate manufacturability, the designs are built to scale using a 3D microfabrication method and assembled into vibration energy harvester prototypes. The fabricated devices based on the optimal results from using different TO techniques are tested and compared with the simulation results. The structures obtained by the level set based TO method require less post-processing before fabrication and the structures obtained by the density based TO method have resonating frequency as low as 100 Hz. The electrical voltage response
Dynamics of liquid films exposed to high-frequency surface vibration
Manor, Ofer; Rezk, Amgad R.; Friend, James R.; Yeo, Leslie Y.
2015-05-01
We derive a generalized equation that governs the spreading of liquid films under high-frequency (MHz-order) substrate vibration in the form of propagating surface waves and show that this single relationship is universally sufficient to collectively describe the rich and diverse dynamic phenomena recently observed for the transport of oil films under such substrate excitation, in particular, Rayleigh surface acoustic waves. In contrast to low-frequency (Hz- to kHz-order) vibration-induced wetting phenomena, film spreading at such high frequencies arises from convective drift generated by the viscous periodic flow localized in a region characterized by the viscous penetration depth β-1≡(2μ /ρ ω ) 1 /2 adjacent to the substrate that is invoked directly by its vibration; μ and ρ are the viscosity and the density of the liquid, respectively, and ω is the excitation frequency. This convective drift is responsible for driving the spreading of thin films of thickness h ≪kl-1 , which spread self-similarly as t1 /4 along the direction of the drift corresponding to the propagation direction of the surface wave, kl being the wave number of the compressional acoustic wave that forms in the liquid due to leakage of the surface wave energy from the substrate into the liquid and t the time. Films of greater thicknesses h ˜kl-1≫β-1 , in contrast, are observed to spread with constant velocity but in a direction that opposes the drift and surface wave propagation due to the attenuation of the acoustic wave in the liquid. The universal equation derived allows for the collective prediction of the spreading of these thin and thick films in opposing directions.
ZHU Wu; ZHANG Jia-min; LIU Hong-li; MENG Feng-feng; ZHANG Zhi-ming
2009-01-01
In order to realize automatic tracking drift of resonance frequency of ultrasonic vibration system with high power and high quality factor Q, adaptive fuzzy control was studied with a self-fabricated ultrasonic plastic welding machine. At first, relations between amplitude of vibration and frequency as well as main loop current and amplitude of vibration were analyzed. From this analysis, we deduced that frequency tracking process of the vibration system can be concluded as an optimizing problem of one dimensional fluctuant extremum of main loop current in vibration system. Then a method of self-optimizing fuzzy control, used for the realization of automatic frequency tracking in vibration system, is presented on the basis of self-optimizing adaptive control approach and fuzzy control approach. The result of experiments shows that the fuzzy self-optimizing method can solve the problem of tracking frequency drift very well. Response time of tracking in the system is less than 50 ms, which basically meets the requirements of frequency tracking in ultrasonic plastic welding machine.
Research on a new type of precision cropping method with variable frequency vibration
无
2007-01-01
Aiming at the cropping operations widely applied in practical industry production, a new method of bar cropping is presented. The rotational speeds of actuating motor of eccentric blocks are controlled by a frequency-changer, and the shearing die provides the bar with the controllable force, frequency and amplitude of vibration. By utilizing the stress concentration at the bottom of V shape groove on the bar, the low stress bar cropping is realized. The bar cropping experiments of duralumin alloy and steel show that the shear surface has no radial distortion and deviation angle, the cutting force is lower and the die life is longer compared with the common bar cropping method. According to the special feature of cutting surface obtained by the new method, a new method of measurement is proposed and applied to assess the cutting surfaces obtained by the different control curves of frequency. The results show that the linear decrease control method is the best.
Natural Frequencies and Vibrating Modes for a Magnetic Planetary Gear Drive
Lizhong Xu
2012-01-01
Full Text Available In this paper, a dynamic model for a magnetic planetary gear drive is proposed. Based on the model, the dynamic equations for the magnetic planetary gear drive are given. From the magnetic meshing forces and torques between the elements for the drive system, the tangent and radial magnetic meshing stiffness is obtained. Using these equations, the natural frequencies and the modes of the magnetic planetary gear drive are investigated. The sensitivity of the natural frequencies to the system parameters is discussed. Results show that the pole pair number and the air gap have obvious effects on the natural frequencies. For the planetary gear number larger than two, the vibrations of the drive system include the torsion mode of the center elements, the translation mode of the center elements, and the planet modes. For the planetary gear number equal to two, the planet mode does not occur, the crown mode and the sun gear mode occur.
Liang, Shanshan; Crovetto, Andrea; Peng, Zhuoteng;
2016-01-01
This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15 Hz and 22 Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision...... 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...
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.
Multiscale wireless sensor node for impedance-based SHM and low-frequency vibration data acquisition
Taylor, Stuart G [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory; Farrar, Charles R [Los Alamos National Laboratory; Todd, Michael D [UCSD
2009-01-01
This paper presents recent developments in an extremely compact, wireless impedance sensor node (WID3, Wireless Impedance Device) at Los Alamos National Laboratory for use in impedance-based structural health monitoring (SHM), Sensor diagnostics and low-frequency vibrational data acquisition. The current generation WID3 is equipped with an Analog Devices AD5933 impedance chip that can resolve measurements up to 100 kHz, a frequency range ideal for many SHM applications. An integrated set of multiplexers allows the end user to monitor seven piezoelectric sensors from a single sensor node. The WID3 combines on-board processing using an Atmega1281 microcontroller, data storage using flash memory, wireless communications capabilities, and a series of internal and external triggering options into a single package to realize a truly comprehensive, self-contained wireless active-sensor node for SHM applications. Furthermore, we recently extended the capability of this device by implementing low-frequency analog to digital and digital and analog converters so that the same device can measure structural vibration data. The WID3 requires less than 70 mW of power to operate, and it can operate in various wireless network paradigms. The performance of this miniaturized and portable device is compared to our previous results and its broader capabilities are demonstrated.
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.
The trans-HOCO radical: Quartic force fields, vibrational frequencies, and spectroscopic constants
Fortenberry, Ryan C.; Huang, Xinchuan; Francisco, Joseph S.; Crawford, T. Daniel; Lee, Timothy J.
2011-10-01
In the search for a full mechanism creating CO2 from OH + CO, it has been suggested that creation of the hydroxyformyl or HOCO radical may be a necessary step. This reaction and its transient intermediate may also be responsible for the regeneration of CO2 in such high quantities in the atmosphere of Mars. Past spectroscopic observations of this radical have been limited and a full gas phase set of the fundamental vibrational frequencies of the HOCO radical has not been reported. Using established, highly accurate quantum chemical coupled cluster techniques and quartic force fields, we are able to compute all six fundamental vibrational frequencies and other spectroscopic constants for trans-HOCO in the gas phase. These methods have yielded rotational constants that are within 0.01 cm-1 for A0 and 10-4 cm-1 for B0 and C0 compared with experiment as well as fundamental vibrational frequencies within 4 cm-1 of the known gas phase experimental ν1 and ν2 modes. Such results lead us to conclude that our prediction of the other four fundamental modes of trans-HOCO are also quite reliable for comparison to future experimental observation, though the discrepancy for the torsional mode may be larger since it is fairly anharmonic. With the upcoming European Space Agency/NASA ExoMars Trace Gas Orbiter, these data may help to establish whether HOCO is present in the Martian sky and what role it may play in the retention of a CO2-rich atmosphere. Furthermore, these data may also help to clear up questions built around the fundamental chemical process of how exactly the OH + CO reaction progresses.
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.
INFLUENCE OF HOUSING RIBBING MODIFICATION ON FREQUENCIES AND SHAPES OF VIBRATIONS
Piotr FOLĘGA
2014-03-01
Full Text Available In article an experimental and theoretical modal analysis of selected structural solutions of housings gear was carried out. Results of the examinations enabled to determine a rate of FEM modal parameters conformity with parameters of actual objects by determination of MAC ratio value. Basing on obtained results of the experimental modal analysis, the numerical models of housings were fine tuned. The obtained conformity of the results of experimental and theoretical modal analysis of examined housings’ solutions enabled to ascertain the correctness of prepared FEM models. The executed modal analysis of various housing versions enabled to estimate influence of made ribbing modifications on form and frequency of its own vibrations.
Vibrational frequencies of anti-diabetic drug studied by terahertz time-domain spectroscopy
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.
CALCULATION OF ELASTICITY MATERIAL CONSTANTS BY OWN VIBRATION FREQUENCY OF ROUND PLATE
V. T. Minchenya
2009-01-01
Full Text Available The paper analyses existing methods for determination of elastic material properties and reveals perspectives for usage of resonant methods which make it possible to execute a non-contact and non-destructive control. As an example of a resonant method application a problem on determination of elastic material properties by own vibration frequency of a specimen in the form of a round plate is considered in the paper. Solution efficiency of the investigated problem using a gradient-search method is given in the paper.
Directional algorithms for the frequency isolation problem in undamped vibrational systems
Moro, Julio; Egaña, Juan C.
2016-06-01
A new algorithm is presented to solve the frequency isolation problem for vibrational systems with no damping: given an undamped mass-spring system with resonant eigenvalues, the system must be re-designed, finding some close-by non-resonant system at a reasonable cost. Our approach relies on modifying masses and stiffnesses along directions in parameter space which produce a maximal variation in the resonant eigenvalues, provided the non-resonant ones do not undergo large variations. The algorithm is derived from first principles, implemented, and numerically tested. The numerical experiments show that the new algorithms are considerably faster and more robust than previous algorithms solving the same problem.
Wan, Quan; Galli, Giulia
2015-12-01
We present a first-principles framework to compute sum-frequency generation (SFG) vibrational spectra of semiconductors and insulators. The method is based on density functional theory and the use of maximally localized Wannier functions to compute the response to electric fields, and it includes the effect of electric field gradients at surfaces. In addition, it includes quadrupole contributions to SFG spectra, thus enabling the verification of the dipole approximation, whose validity determines the surface specificity of SFG spectroscopy. We compute the SFG spectra of ice Ih basal surfaces and identify which spectra components are affected by bulk contributions. Our results are in good agreement with experiments at low temperature.
Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)
1997-01-01
The vibrational frequencies of MO2 are computed at many levels of theory, including HF, B3LYP, BP86, CASSCF, MP2, and CCSD(T). The computed results are compared with the available experimental results. Most of the methods fail for at least one state of the systems considered. The accuracy of the results and the origin of the observed failures are discussed. The B3LYP bond energies are compared with traditional methods for a variety of systems, ranging from FeCOn+ to SiCln and its positive ions. The cases where B3LYP differs from the traditional methods are discussed.
Narrowband frequency-hopping radars for the range estimation of moving and vibrating targets
Zhang, Yimin; Amin, Moeness G.; Ahmad, Fauzia
2008-04-01
An important task in urban sensing operation is accurate estimation and positioning tracking of moving targets. Equally important is target identifications and classifications based on distinctions in the respective motion signatures, such as targets encountering translation versus rotation or vibration motions or targets exhibiting linear versus nonlinear motions. Dual-frequency radars, which estimate the range of a target based on the phase difference between two closely spaced frequencies, have been shown to be a cost-effective method for this purpose. In particular, when time-frequency signal representation techniques are incorporated, Doppler signature enhancement and localization in the time-frequency domain enables robust range estimation of multiple targets with different motion profiles and small radar cross-sections. In this paper, the dual-frequency radar concept is extended to develop a narrowband (NB) frequency-hopping (FH) radar. The proposed NB-FH radar provides multifold advantages such as low probability of intercept, low interference to/from other systems, and flexible bandwidth usage for the improvement of range accuracy and phase unwrapping.
Low-frequency and wideband vibration energy harvester with flexible frame and interdigital structure
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
Investigation of Microstructure, Natural Frequencies and Vibration Modes of Dragonfly Wing
H. Rajabi; M. Moghadami; A. Darvizeh
2011-01-01
In the present work, a thorough investigation on the microstructural and morphological aspects of dragonfly wings was carried out using scanning electron microscope. Then, based on this study and the previous reports, a precise three-dimensional numerical model was developed and natural frequencies and vibration modes of dragonfly forewing were determined by finite element method. The results shown that dragonfly wings are made of a series of adaptive materials, which form a very complex composite structure. This bio-composite fabrication has some unique features and potential benefits. Furthermore, the numerical results show that the first natural frequency of dragonfly wings is about 168 Hz and bending is the predominant deformation mode in this stage. The accuracy of the present analysis is verified by comparison of calculated results with experimental data.This paper may be helpful for micro aerial vehicle design concerning dynamic response.
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.
A vibrating reed apparatus to measure the natural frequency of multilayered thin films
Gamboa, F.; López, A.; Avilés, F.; Corona, J. E.; Oliva, A. I.
2016-04-01
An apparatus for measuring the natural frequency of sub-micrometric layered films in cantilever beam configuration is presented. The instrument comprises a specially designed test rig with a sample holder, an electronic excitation source, a vibration sensor and an automated software for the excitation and data recollection. The beam is excited by means of an air pulse and the oscillation amplitude of its free end is measured through a laser diode-photosensor arrangement. The instrument provides a very low uncertainty (˜1 mHz, for frequencies of the order of tens Hz) for repeated sequential tests and the major source of uncertainty (˜0.2 Hz, corresponding to a coefficient of variation of 0.18%) arises from the difficulty of placing the sample in an exactly identical location upon clamping. This high sensitivity renders the capability of measuring very small frequency shifts upon deposition of sub-micrometric films over thicker substrates. In order to assess the reliability of the apparatus, cantilever beams of 125 μm thick neat Kapton (substrate) and thin layered films of Au/Kapton and Al/Au/Kapton of 200-250 nm film thickness were fabricated and their natural frequency and damping factor were measured. Calculations of the natural frequency of such beams by finite element analysis further support the accuracy of the experimental measurements.
A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency
Guo, Yan-bo; Liu, Zi-zhong; Liu, Hong-xia; Zhang, Feng-ying; Yin, Jun-qing
2016-07-01
A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L = C, Si, Ge, n = 3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.0). There are high positive correlations between the theoretical calculated the NICS values and the value of the RSVRSF (A1g/A1‧) of the LnHn (L = C, Si, Ge, n = 3, 5-8). The bigger the aromatic degree, the bigger the RSVRSF is. The value of the RSVRSF is a new probe of aromaticity. Expectedly, it is predicted that the experimental determination of the aromatic degree can be achieved by the determination of the ring stretching vibration (A1g/A1‧) Raman spectrum frequencies for the aromatic target molecules.
A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency.
Guo, Yan-Bo; Liu, Zi-Zhong; Liu, Hong-Xia; Zhang, Feng-Ying; Yin, Jun-Qing
2016-07-01
A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L=C, Si, Ge, n=3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.0). There are high positive correlations between the theoretical calculated the NICS values and the value of the RSVRSF (A1g/A1') of the LnHn (L=C, Si, Ge, n=3, 5-8). The bigger the aromatic degree, the bigger the RSVRSF is. The value of the RSVRSF is a new probe of aromaticity. Expectedly, it is predicted that the experimental determination of the aromatic degree can be achieved by the determination of the ring stretching vibration (A1g/A1') Raman spectrum frequencies for the aromatic target molecules. PMID:27085169
Guided wave structural health monitoring offers the prospect of continuous interrogation of large plate-like structures with a sparse network of permanently attached sensors. Currently, the most common approach is to monitor changes in the received signals by subtraction from a reference signal obtained when the structure was known to be defect-free. In this paper a comparison is made between this defect-free subtraction approach and a technique in which low-frequency vibration modulation of guided wave signals is used to detect nonlinear scatterers. The modulation technique potentially overcomes the need for the defect-free reference measurement as the subtraction is now made between different parts of an externally applied low-frequency vibration. Linear defects were simulated by masses bonded onto a plate and nonlinear scatterers were simulated by loading a similar mass against the plate. The experimental results show that the defect-free subtraction technique performs well in detecting the bonded mass whereas the modulation technique is able to discriminate between the bonded and loaded masses. Furthermore, because the modulation technique does not require a defect-free reference, it is shown to be relatively independent of temperature effects, a significant problem for reference based subtraction techniques
Xingmou Liu
2016-04-01
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.
Rahm, Martin; Tyrode, Eric; Brinck, Tore; Johnson, Magnus
2011-01-01
Vibrational sum frequency spectroscopy (VSFS) and quantum chemical modeling have been employed to investigate the molecular surface structure of ammonium and potassium dinitramide (ADN and KDN) crystals. Identification of key vibrational modes was made possible by performing density functional theory calculations of molecular clusters. The surface of KDN was found to be partly covered with a thin layer of the decomposition product KNO3, which due to its low thickness was not detectable by inf...
LIANG, YONG-QIANG; QI, MENG-CHUN; Xu, Jiang; Xu, Juan; Liu, Hua-Wei; Dong, Wei; LI, JIN-YUAN; Hu, Min
2014-01-01
Osteoporosis deteriorates jaw bone quality and may compromise early implant osseointegration and early implant loading. The influence of low-magnitude, high-frequency (LMHF) vibration on peri-implant bone healing and implant integration in osteoporotic bones remains poorly understood. LMHF loading via whole-body vibration (WBV) for 8 weeks has previously been demonstrated to significantly enhance bone-to-implant contact, peri-implant bone fraction and implant mechanical properties in osteopor...
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
Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy
An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2–3 cm−1. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance
Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy
Reppert, Mike; Tokmakoff, Andrei
2015-08-01
An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2-3 cm-1. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance.
Communication: Quantitative multi-site frequency maps for amide I vibrational spectroscopy
Reppert, Mike [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States); Tokmakoff, Andrei, E-mail: tokmakoff@uchicago.edu [Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States)
2015-08-14
An accurate method for predicting the amide I vibrational spectrum of a given protein structure has been sought for many years. Significant progress has been made recently by sampling structures from molecular dynamics simulations and mapping local electrostatic variables onto the frequencies of individual amide bonds. Agreement with experiment, however, has remained largely qualitative. Previously, we used dipeptide fragments and isotope-labeled constructs of the protein G mimic NuG2b as experimental standards for developing and testing amide I frequency maps. Here, we combine these datasets to test different frequency-map models and develop a novel method to produce an optimized four-site potential (4P) map based on the CHARMM27 force field. Together with a charge correction for glycine residues, the optimized map accurately describes both experimental datasets, with average frequency errors of 2–3 cm{sup −1}. This 4P map is shown to be convertible to a three-site field map which provides equivalent performance, highlighting the viability of both field- and potential-based maps for amide I spectral modeling. The use of multiple sampling points for local electrostatics is found to be essential for accurate map performance.
Vibrational spectroscopy at interfaces by IR-VIS sum-frequency generation using CLIO FEL
IR-vis sum-frequency generation (SFG) has developed into a versatile technique for probing the vibrational structure of interfaces. To overcome the limited spectral range accessible by benchtop IR lasers, we have developed an SFG spectrometer that makes use of the broad band tuneable infrared beam provided by the CLIO-FEL. We will evaluate the gain in sensitivity of the FEL-SFG spectrometer in comparison to that of benchtop lasers, taking account of the surface damage by laser heating. Thereafter, we review the different research projects undertaken using this facility: (1) The interface selectivity of SFG makes it particularly suitable for probing buried liquid/solid interface. We took advantage of the spectrometer sensitivity to monitor the electrochemical deposition of hydrogen on platinum single crystals at under- and overpotential (2) Because of its sensitivity to the molecular symmetry, SFG allows probing the conformation of self assembled monolayers deposited on metals. We discuss SFG spectra of ω(4-nitroanilino)-dodecane adsorbed on polycrystalline gold and silver films; in the 1550 - 900 cm-1 spectral range. (3) We have undertaken a spectroscopic approach for the investigation of polymer films adhesion on glass. Polyurethane/glass interface is investigated in the 2200 - 1600 cin-1 spectral region. (4) The use of the CLIO FEL allows probing of the vibrational dynamics of the prominent IR active vibrations between 1500 and 500 cm-1 of fullerene epitaxial films. These modes are modified upon charge transfer from the substrate to the C60 molecules. Preliminary SFG spectra of C60/Ag interface are presented. (5) Site specific detection of CO adsorption and CO + O coadsorption on Pd(111) are studied
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.
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.
Luo, Jiawei; Banerjee, Joy; Pantano, Carlo G; Kim, Seong H
2016-06-21
It is generally accepted that the mechanical properties of soda lime silica (SLS) glass can be affected by the interaction between sodium ions and hydrous species (silanol groups and water molecules) in its surface region. While the amount of these hydrous species can be estimated from hydrogen profiles and infrared spectroscopy, their chemical environment in the glass network is still not well understood. This work employed vibrational sum frequency generation (SFG) spectroscopy to investigate the chemical environment of hydrous species in the surface region of SLS float glass. SLS float glass shows sharp peaks in the OH stretching vibration region in SFG spectra, while the OH stretch peaks of glasses that do not have leachable sodium ions and the OH peaks of water molecules in condensed phases are normally broad due to fast hydrogen bonding dynamics. The hydrous species responsible for the sharp SFG peaks for the SLS float glass were found to be thermodynamically more stable than physisorbed water molecules, did not exchange with D2O, and were associated with the sodium concentration gradient in the dealkalized subsurface region. These results suggested that the hydrous species reside in static solvation shells defined by the silicate network with relatively slow hydrogen bonding dynamics, compared to physisorbed water layers on top of the glass surface. A putative radial distribution of the hydrous species within the SLS glass network was estimated based on the OH SFG spectral features, which could be compared with theoretical distributions calculated from computational simulations. PMID:27254814
Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters
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.
A high figure of merit vibrational energy harvester for low frequency applications
Nico, V.; Boco, E.; Frizzell, R.; Punch, J.
2016-01-01
Small-scale vibration energy harvesters that respond efficiently at low frequencies are challenging to realize. This paper describes the design and implementation of one such harvester, which achieves a high volumetric Figure of Merit (FoMv = 2.6% at 11.50 Hz) at the scale of a C-type battery and outperforms other state-of-the-art devices in the sub 20 Hz frequency range. The device employs a 2 Degree-of-Freedom velocity-amplified approach and electromagnetic transduction. The harvester comprises two masses oscillating one inside the other, between four sets of magnetic springs. Collisions between the two masses transfer momentum from the heavier to the lighter mass, exploiting velocity amplification. The paper first presents guidelines for designing and optimizing the transduction mechanism, before a nonlinear numerical model for the system dynamics is developed. Experimental characterisation of the harvester design is then presented to validate both the transducer optimization and the dynamics model. The resulting high FoMV demonstrates the effectiveness of the device for low frequency applications, such as human motion.
Low frequency vibrational modes of oxygenated myoglobin, hemoglobins, and modified derivatives.
Jeyarajah, S; Proniewicz, L M; Bronder, H; Kincaid, J R
1994-12-01
The low frequency resonance Raman spectra of the dioxygen adducts of myoglobin, hemoglobin, its isolated subunits, mesoheme-substituted hemoglobin, and several deuteriated heme derivatives are reported. The observed oxygen isotopic shifts are used to assign the iron-oxygen stretching (approximately 570 cm-1) and the heretofore unobserved delta (Fe-O-O) bending (approximately 420 cm-1) modes. Although the delta (Fe-O-O) is not enhanced in the case of oxymyoglobin, it is observed for all the hemoglobin derivatives, its exact frequency being relatively invariable among the derivatives. The lack of sensitivity to H2O/D2O buffer exchange is consistent with our previous interpretation of H2O/D2O-induced shifts of v(O-O) in the resonance Raman spectra of dioxygen adducts of cobalt-substituted heme proteins; namely, that those shifts are associated with alterations in vibrational coupling of v(O-O) with internal modes of proximal histidyl imidazole rather than to steric or electronic effects of H/D exchange at the active site. No evidence is obtained for enhancement of the v(Fe-N) stretching frequency of the linkage between the heme iron and the imidazole group of the proximal histidine. PMID:7983043
Note: A kinematic shaker system for high amplitude, low frequency vibration testing
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.
Theoretical study of sum-frequency vibrational spectroscopy on limonene surface
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.
Theoretical study of sum-frequency vibrational spectroscopy on limonene surface
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
Ohta, Kaoru; Tayama, Jumpei; Saito, Shinji; Tominaga, Keisuke
2012-11-20
In liquid water, hydrogen bonds form three-dimensional network structures, which have been modeled in various molecular dynamics simulations. Locally, the hydrogen bonds continuously form and break, and the network structure continuously fluctuates. In aqueous solutions, the water molecules perturb the solute molecules, resulting in fluctuations of the electronic and vibrational states. These thermal fluctuations are fundamental to understanding the activation processes in chemical reactions and the function of biopolymers. In this Account, we review studies of the vibrational frequency fluctuations of solute molecules in aqueous solutions using three-pulse infrared photon echo experiments. For comparison, we also briefly describe dynamic fluorescence Stokes shift experiments for investigating solvation dynamics in water. The Stokes shift technique gives a response function, which describes the energy relaxation in the nonequilibrium state and corresponds to the transition energy fluctuation of the electronic state at thermal equilibrium in linear response theorem. The dielectric response of water in the megahertz to terahertz frequency region is a key physical quantity for understanding both of these frequency fluctuations because of the influence of electrostatic interactions between the solute and solvent. We focus on the temperature dependence of the three experiments to discuss the molecular mechanisms of both the frequency fluctuations in aqueous solutions. We used a biexponential function with sub-picosecond and picosecond time constants to characterize the time-correlation functions of both the vibrational and electronic frequency fluctuations. We focus on the slower component, with time constants of 1-2 ps for both the frequency fluctuations at room temperature. However, the temperature dependence and isotope effect for the time constants differ for these two types of fluctuations. The dielectric interactions generally describe the solvation dynamics of
A generalized theory of frequency- and time-resolved vibrational sum-frequency generation (SFG) spectroscopy of adsorbates at surfaces is presented using the density matrix formalism. Our theoretical treatment is specifically aimed at addressing issues that accompany the relatively novel SFG approach using broadband infrared pulses. The ultrashort duration of these pulses makes them ideally suited for time-resolved investigations, for which we present a complete theoretical treatment. A second key characteristic of these pulses is their large bandwidth and high intensity, which allow for highly non-linear effects, including vibrational ladder climbing of surface vibrations. We derive general expressions relating the density matrix to SFG spectra, and apply these expressions to specific experimental results by solving the coupled optical Bloch equations of the density matrix elements. Thus, we can theoretically reproduce recent experimentally demonstrated hot band SFG spectra using femtosecond broadband infrared excitation of carbon monoxide (CO) on a Ru(001) surface
Caldwell, Michael S; Lee, Norman; Schrode, Katrina M; Johns, Anastasia R; Christensen-Dalsgaard, Jakob; Bee, Mark A
2014-04-01
Anuran ears function as pressure difference receivers, and the amplitude and phase of tympanum vibrations are inherently directional, varying with sound incident angle. We quantified the nature of this directionality for Cope's gray treefrog, Hyla chrysoscelis. We presented subjects with pure tones, advertisement calls, and frequency-modulated sweeps to examine the influence of frequency, signal level, lung inflation, and sex on ear directionality. Interaural differences in the amplitude of tympanum vibrations were 1-4 dB greater than sound pressure differences adjacent to the two tympana, while interaural differences in the phase of tympanum vibration were similar to or smaller than those in sound phase. Directionality in the amplitude and phase of tympanum vibration were highly dependent on sound frequency, and directionality in amplitude varied slightly with signal level. Directionality in the amplitude and phase of tone- and call-evoked responses did not differ between sexes. Lung inflation strongly affected tympanum directionality over a narrow frequency range that, in females, included call frequencies. This study provides a foundation for further work on the biomechanics and neural mechanisms of spatial hearing in H. chrysoscelis, and lends valuable perspective to behavioral studies on the use of spatial information by this species and other frogs. PMID:24504183
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.
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. PMID:26580050
Fin whale sound reception mechanisms: skull vibration enables low-frequency hearing.
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.
The thermal effects on high-frequency vibration of beams using energy flow analysis
Zhang, Wenbo; Chen, Hualing; Zhu, Danhui; Kong, Xiangjie
2014-04-01
In this paper, the energy flow analysis (EFA) method is developed to predict the high-frequency response of beams in a thermal environment, which is a topic of concern in aerospace and automotive industries. The temperature load applied on the structures can generate thermal stresses and change material properties. The wavenumber and group velocity associated with the in-plane axial force arising from thermal stresses are included in the derivation of the governing energy equation, and the input power is obtained from the derived effective bending stiffness. In addition, effect of temperature-dependent material properties is considered in the EFA model. To verify the proposed formulation, numerical simulations are performed for a pinned-pinned beam in a uniform thermal environment. The EFA results are compared with the modal solutions for various frequencies and damping loss factors, and good correlations are observed. The results show that the spatial distributions and levels of energy density can be affected by the thermal effects, and the vibration response of beams increases with temperature.
A micromachined low-frequency piezoelectric harvester for vibration and wind energy scavenging
To efficiently scavenge ambient vibration energy and wind energy at the same time, a low-frequency piezoelectric harvester was designed, fabricated and tested. A lumped-parameter model of the cantilevered piezoelectric energy harvester with a proof mass was established and the closed-form expressions of voltage and power on a resistance load under base acceleration excitation were derived. After effects of the lengths of the proof mass and electrodes on output power were analyzed, a MEMS harvester was optimally designed. By using aluminum nitride as piezoelectric layer, a MEMS energy harvester was fabricated with bulk micromachining process. Experimental results show that the open-circuit frequency of the MEMS harvester is about 134.8 Hz and the matched resistance is about 410 kΩ. Under the harmonic acceleration excitation of ±0.1 g, the maximum output power is about 1.85 µW, with the normalized power density of about 6.3 mW cm−3 g−2. The critical wind speed of the device is between 12.7 and 13.2 m s−1 when the wind direction is from the proof mass to the fixed end of the cantilever. The maximum output power under 16.3 m s−1 wind is about 2.27 µW. (paper)
Kliewer, C.J.; Somorjai, G.A.
2008-11-26
Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three {alpha},{beta}-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr aldehyde, 100 Torr hydrogen) in the temperature range of 295K to 415K. SFG-VS data showed that acrolein has mixed adsorption species of {eta}{sub 2}-di-{sigma}(CC)-trans, {eta}{sub 2}-di-{sigma}(CC)-cis as well as highly coordinated {eta}{sub 3} or {eta}{sub 4} species. Crotonaldehyde adsorbed to Pt(111) as {eta}{sub 2} surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the {eta}{sub 2} adsorption species, and became more highly coordinated as the temperature was raised to 415K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation 'cracking' product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotylalcohol.
Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters
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
Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters
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.
Huang, Xinchuan; Taylor, Peter R.; Lee, Timothy J.
2011-01-01
High levels of theory have been used to compute quartic force fields (QFFs) for the cyclic and linear forms of the C H + molecular cation, referred to as c-C H + and I-C H +. Specifically the 33 3333 singles and doubles coupled-cluster method that includes a perturbational estimate of connected triple excitations, CCSD(T), has been used in conjunction with extrapolation to the one-particle basis set limit and corrections for scalar relativity and core correlation have been included. The QFFs have been used to compute highly accurate fundamental vibrational frequencies and other spectroscopic constants using both vibrational 2nd-order perturbation theory and variational methods to solve the nuclear Schroedinger equation. Agreement between our best computed fundamental vibrational frequencies and recent infrared photodissociation experiments is reasonable for most bands, but there are a few exceptions. Possible sources for the discrepancies are discussed. We determine the energy difference between the cyclic and linear forms of C H +, 33 obtaining 27.9 kcal/mol at 0 K, which should be the most reliable available. It is expected that the fundamental vibrational frequencies and spectroscopic constants presented here for c-C H + 33 and I-C H + are the most reliable available for the free gas-phase species and it is hoped that 33 these will be useful in the assignment of future high-resolution laboratory experiments or astronomical observations.
Liu, Tao; Yan, Shaoze; Zhang, Wei
2016-06-01
Deployable structures have been widely used in on-orbit servicing spacecrafts, and the vibration properties of such structures have become increasingly important in the aerospace industry. The constant-Q nonstationary Gabor transform (CQ-NSGT) is introduced in this paper to accurately evaluate the variation in the frequency and amplitude of vibration signals along with time. First, an example signal is constructed on the basis of the vibration properties of deployable structures and is processed by the short-time Fourier transform, Wigner-Ville distribution, Hilbert-Huang transform, and CQ-NSGT. Results show that time and frequency resolutions are simultaneously fine only by employing CQ-NSGT. Subsequently, a zero padding operation is conducted to correct the calculation error at the end of the transform results. Finally, a set of experimental devices is constructed. The vibration signal of the experimental mode is processed by CQ-NSGT. On this basis, the experimental signal properties are discussed. This time-frequency method may be useful for formulating the dynamics for complex deployable structures.
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.
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
We report the development of a self-resonant flow sensor based on a resonant frequency shift due to flow-induced vibrations. The vibration of a microcantilever beam, induced by a turbulent flow, is modulated with its own natural frequency, and the resonant frequency is shifted by a surface stress on the beam due to fluid drag force. The vibration induced by air flow is measured by using a piezoelectric PZT material on a silicon cantilever beam. The theoretical resonant frequencies of two cantilever beams (lengths: 610 µm and 2000 µm) are 12416 Hz and 1155 Hz, respectively. For the air flow velocities of 2.8 m s−1 and 9.7 m s−1, the shifted resonant frequencies of the cantilever beam whose length is 610 µm are 12 810 Hz and 15 602 Hz, respectively. Sensitivities of the two self-resonant flow sensors with the 610 and 2000 µm long beams are approximately 384 ± 15 Hz/(m/s) and 20.4 ± 0.6 Hz/(m/s), respectively.
Armine Amyan; Sinerik Ayrapetyan
2004-01-01
The changes of wet and dry weights and germination of barley seed in different periods of its swelling in nontreated (control), extremely low frequency electromagnetic fields (ELF EMF) )treated, and extremely low frequency vibrations (ELFV)treated cold (4°C) and warm (20°C) distilled water (DW) were studied. The metabolic-dependent seed hydration, dry weight dissolving, germination, and water binding in seed were modulated by preliminary EMF- and ELFV-treated DW. Frequency “windows” for the...
Verotti, M.; Servadio, P.; Belfiore, N. P.; Bergonzoli, S.
2012-04-01
-soil-man interaction. In particular, a model based on elasto-visco-plastic concentrated parameters, with multiple degrees of freedom, will be used in order to build a method for detecting a soil damage index, especially expressed in terms of increasing of soil compaction. Besides the axle load, the model will take into account the frequency of the vibrations that the vehicle is transmitting to the soil. Such model expresses a numerical value for the transmissibility coefficient and also allows evaluating the damage at the surface and on the bulk medium where the agricultural crops initially develop. Key words: vehicle-soil interaction, vibration, compaction, models. Acknowledgements This work was carried out under the auspices of the special project "Sceneries of adaptation of the Italian agriculture to the climatic changes" (AGROSCENARI) of the Agricultural Research Council, and Italian Ministry of the Agricultural and Forestry Politics.
In this work the geometry,force constants and vibrational frequencies are calculated for some hydrocarbones (ethane,propane,isobutane,neopentane,cyclopropane,cyclo-butanol) using the MINDO/3 methode(Modifie Iintermediate Neglect of Differential Overlap).The force constants are calculated using MINDO/3.Force programe when we modified this program by fixed the wave function which is used in the calculation of the force of the molecules with respect of cartisan coordinate.The research includes many steps as following:-1 1-Calculated the coordinates of the equilibruim geometry of the molecules by use (COAT) program. 2-Calculated the force constant by used MINDO/3 force program. 3-Calculate the elements of the atomic mass matrix. 4-Calculates the vibrational frequencies by solvent the secular equation.(6 tabs., 6 figs., 43 refs.)
Lixia, Li; Anjiang, Cai
2016-06-01
We propose a new kind of elastic metamaterial (EM) shaft with discretized arc-shaped rubber layers, which shows excellent low-frequency vibration properties. The band gaps of the shaft structure were analyzed by employing the finite element method. The proposed EM shaft exhibits much lower band gaps than the corresponding structures with the whole rubber ring. Furthermore, the band gaps can be modulated by tuning the arc angle and the number of the arc-shaped rubbers. Additionally, we observed that the first complete band gap tends to disappear when the arc angle of each arc-shaped rubber section is decreased but the arc number remains fixed because the arc angle more strongly affects the rotational stiffness than the transverse stiffness of the rubber layers. This new type of EM shafts could find potential application as a means to control the low-frequency vibrations of rotor shafts in mechanical engineering.
Chen, Xiaoyun; Wang, Jie; Kristalyn, Cornelius B.; Chen, Zhan
2007-01-01
Interactions between membrane bilayers and peptides/proteins are ubiquitous throughout a cell. To determine the structure of membrane bilayers and the associated peptides/proteins, model systems such as supported lipid bilayers are often used. It has been difficult to directly investigate the interactions between a single membrane bilayer and peptides/proteins without exogenous labeling. In this work we demonstrate that sum frequency generation vibrational spectroscopy can be employed to stud...
Long Zhang; Guoliang Xiong; Hesheng Liu; Huijun Zou; Weizhong Guo
2010-04-01
A parametric time-frequency representation is presented based on timevarying autoregressive model (TVAR), followed by applications to non-stationary vibration signal processing. The identiﬁcation of time-varying model coefﬁcients and the determination of model order, are addressed by means of neural networks and genetic algorithms, respectively. Firstly, a simulated signal which mimic the rotor vibration during run-up stages was processed for a comparative study on TVAR and other non-parametric time-frequency representations such as Short Time Fourier Transform, Continuous Wavelet Transform, Empirical Mode Decomposition, Wigner–Ville Distribution and Choi–Williams Distribution, in terms of their resolutions, accuracy, cross term suppression as well as noise resistance. Secondly, TVAR was applied to analyse non-stationary vibration signals collected from a rotor test rig during run-up stages, with an aim to extract fault symptoms under non-stationary operating conditions. Simulation and experimental results demonstrate that TVAR is an effective solution to non-stationary signal analysis and has strong capability in signal time-frequency feature extraction.
Solvent effect on the anharmonic vibrational frequencies in guanine-cytosine base pair
Bende, A.; Muntean, C. M.
2012-02-01
We present an ab initio study of the vibrational properties of cytosine and guanine in the Watson-Crick and Hoogsteen base pair configurations. The results are obtained by considering the DFT method together with the Polarizable Continuum Model (PCM) using PBE and B3PW91 exchange-correlation functionals and triple-ζ valence basis set. We investigate the importance of anharmonic corrections for the vibrational modes taking into account the solvent effect of the water environment. In particular, the unusual anharmonic effect of the H+ vibration in the case of the Hoogsteen base pair configuration is discussed.
Kim, Eui-ryong; Oh, Jae-Seop; Yoo, Won-Gyu
2014-01-01
[Purpose] We investigated the effect of vibration at various frequencies on serratus anterior (SA) muscle activity. [Subjects] Ten male subjects were recruited. [Methods] The subjects performed the push-up plus exercise supported by straps above the surface and vertical ropes in the Redcord sling. During the push-up plus, vibrations of 0, 30, 50, or 90 Hz were applied to the Redcord sling using a mechanical vibration apparatus attached to the rope. SA muscle activity was recorded using electr...
Neugebauer, R.; Linke, M.; Kunze, H.; Ullrich, M. [Fraunhofer Institut fuer Werkzeugmaschinen und Umformtechnik (IWU), Chemnitz / Dresden (Germany)
2010-07-01
Structural vibrations of a wind turbine's drive train are one of the main reasons for noise emissions. Mechanical vibrations are transferred through the structure and emitted as noise by large surfaces, e.g. tower and nacelle. Dominant vibration excitation is caused for example by the gear mesh. If the gear mesh frequency is coinciding with the frequency of a structural resonance, the emitted noise contains noticeable single tones. German immission control law requires a ''tonal penalty'' up to 6 dB, if the emitted noise contains annoying tones. To ensure compliance with immission limits those tones must be reduced or eliminated. For wind turbines running with variable speed an active vibration absorber has been developed, whose absorber frequency and damping is adapted corresponding to the alternating vibration excitation. (orig.)
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.
Park, Yong Bum; Lee, Christopher M; Kafle, Kabindra; Park, Sunkyu; Cosgrove, Daniel; Kim, Seong H
2014-07-14
The crystallinity, allomorph content, and mesoscale ordering of cellulose produced by Gluconacetobacter xylinus cultured with different plant cell wall matrix polysaccharides were studied with vibrational sum frequency generation (SFG) spectroscopy and X-ray diffraction (XRD).
Sørensen, Herman
1997-01-01
Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board......Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board...
Sung, J.; Zhang, L.; Tian, C.; Waychunas, G. A.; Shen, Y. R.
2011-04-01
Sum frequency vibrational spectroscopy was used to study the protonated R-plane (1{bar 1}02 ) sapphire surface. The OH stretch vibrational spectra show that the surface is terminated with three hydroxyl moieties, two from AlOH{sub 2} and one from Al{sub 2}OH functional groups. The observed polarization dependence allows determination of the orientations of the three OH species. The results suggest that the protonated sapphire (1{bar 1}02 ) surface differs from an ideal stoichimetric termination in a manner consistent with previous X-ray surface diffraction (crystal truncation rod) studies. However, in order to best explain the observed hydrogenbonding arrangement, surface oxygen spacing determined from the X-ray diffraction study requires modification.
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...
Choi, Yunhee; Ju, Suna; Chae, Song Hee; Jun, Sangbeom; Ji, Chang-Hyeon
2015-06-01
This paper presents a vibration energy harvester using a springless spherical permanent magnet with a non-uniform mass distribution as a proof mass. The magnet has been designed to have the center of mass below the geometrical center, which generates a roly-poly-like motion in response to external vibrations and maintains the upright position. Utilizing this roly-poly-like magnet, proof-of-concept electromagnetic energy harvesters have been fabricated, tested and analyzed. An analytical model which explains the motion of the magnet assembly and resulting output voltage has been developed by finite element analysis of the magnetic field distribution and motion analysis of the magnet assembly. With the fabricated device, a maximum open-circuit voltage of 48.85 mVrms and an output power of 9.03 μW have been obtained in response to a 20 Hz sinusoidal vibration at 3 g acceleration.
Frequencies in the Vibration Induced by the Rotor Stator Interaction in a Centrifugal Pump Turbine
Rodriguez, Cristian; Egusquiza, Eduard; Santos, Ilmar
2007-01-01
among their amplitudes. It is valuable for the design and condition monitoring to count on these characteristics. A CFD model is an appropriate tool to determine the force and its characteristics. However it is time consuming and needs highly qualified human resources while usually these results are...... result of the analysis and after it is carried out in one of the units, the vibration levels are reduced The vibration induced by the RSI is predicted considering the sequence of interaction and different amplitudes in the interactions between the same moving blade and different stationary blades, giving...
无
2006-01-01
This paper presents the effects of surface finish and treatment on the high cycle fatigue behaviour of vibrating cylinder block of a new two-stroke free piston engine at complex variable amplitude loading conditions using frequency response approach,Finite element modelling and frequency response analysis was conducted using finite element analysis software Package MSC.PATRAN/MSC.NASTRAN and fatigue life prediction was carried out using MSC.FATIGUE software. Based on the finite element results, different frequency response approach was applied to predict the cylinder block fatigue life. Results for different load histories and material combinations are also discussed. Results indicated great effects for all surface finish and treatment. It is concluded that polished and cast surface finish conditions give the highest and lowest cylinder block lives, respectively; and that Nitrided treatment leads to longest cylinder block life. The results were used to draw contour plots of fatigue life and damage in the worst or most damaging case.
Bao, Bin; Guyomar, Daniel; Lallart, Mickaël
2016-09-01
This article proposes a nonlinear tri-interleaved piezoelectric topology based on the synchronized switch damping on inductor (SSDI) technique, which can be applied to phononic metamaterials for elastic wave control and effective low-frequency vibration reduction. A comparison of the attenuation performance is made between piezoelectric phononic metamaterial with distributed SSDI topology (each SSDI shunt being independently connected to a single piezoelectric element) and piezoelectric phononic metamaterial with the proposed electronic topology. Theoretical results show excellent band gap hybridization (near-coupling between Bragg scattering mechanism and wideband resonance mechanism induced by synchronized switch damping networks in piezoelectric phononic metamaterials) with the proposed electronic topology over the investigated frequency domain. Furthermore, piezoelectric phononic metamaterials with proposed electronic topology generated a better low-frequency broadband gap, which is experimentally validated by measuring the harmonic response of a piezoelectric phononic metamaterial beam under clamped–clamped boundary conditions.
Huerta-Lopez, C. I.; Upegui Botero, F. M.; Pulliam, J.; Willemann, R. J.; Pasyanos, M.; Schmitz, M.; Rojas Mercedes, N.; Louie, J. N.; Moschetti, M. P.; Martinez-Cruzado, J. A.; Suárez, L.; Huerfano Moreno, V.; Polanco, E.
2013-12-01
Site characterization in civil engineering demands to know at least two of the dynamic properties of soil systems, which are: (i) dominant vibration frequency, and (ii) damping. As part of an effort to develop understanding of the principles of earthquake hazard analysis, particularly site characterization techniques using non invasive/non destructive seismic methods, a workshop (Pan-American Advanced Studies Institute: New Frontiers in Geophysical Research: Bringing New Tools and Techniques to Bear on Earthquake Hazard Analysis and Mitigation) was conducted during july 15-25, 2013 in Santo Domingo, Dominican Republic by the alliance of Pan-American Advanced Studies Institute (PASI) and Incorporated Research Institutions for Seismology (IRIS), jointly supported by Department of Energy (DOE) and National Science Foundation (NSF). Preliminary results of the site characterization in terms of fundamental vibration frequency and damping are here presented from data collected during the workshop. Three different methods were used in such estimations and later compared in order to identify the stability of estimations as well as the advantage or disadvantage among these methodologies. The used methods were the: (i) Random Decrement Method (RDM), to estimate fundamental vibration frequency and damping simultaneously; (ii) Empirical Mode Decomposition (EMD), to estimate the vibration modes, and (iii) Horizontal to Vertical Spectra ratio (HVSR), to estimate the fundamental vibration frequency. In all cases ambient vibration and induced vibration were used.
Miroslav M. Jovanović
2010-10-01
Full Text Available U radu je prikazan postupak i metodologija ispitivanja vibracija na helikopteru 'gazela' radi definisanja efikasnosti prigušenja vibracija na vezi struktura - sedište pilota. Posebna pažnja posvećena je teorijskim osnovama vibracija na helikopteru, određivanju radnih frekvencija, definisanju režima rada i profila leta helikoptera u toku ispitivanja. Na kraju rada prikazani su rezultati merenja vibracija u frekventnom domenu. / In this paper the procedure and methodology of vibration testing on a Gazelle helicopter are presented with the aim to define efficiency of vibration damping at the structure-pilot seat connection. A particular attention is paid to the theoretical basis of helicopter vibrations, definition of working frequency, regime and profile of flight during the test. The results of the vibration measurement are shown in the frequency domain. Introduction Nowadays, possibility of defining loads and vibrations is one of the most important requests in the design and modification of processes on helicopters. The loads occuring on the main rotor during flight are the basic source of vibrations on the helicopter. Possibilities to satisfy international standards in the area of structural and human vibrations are based on continuous and adequate measurement and analysis of the vibration levels on all elements of helicopters. This paper shows the procedures of vibration measuring and analyzing in order to define efficiency of vibration damping using a modern acquisition system NetdB 12 and its software dBFA Suite. Theoretical analysis of vibration sources on the helicopter main rotor The helicopter rotor operates in a complex aerodynamic flow field. The aerodynamic loads on the rotor blade vary considerably as it moves around the rotor disc, and in steady flight these loads are periodic. A particular attention is paid to a theoretical basis of vibration sources on a helicopter. A complex aerodynamic field in the plane of the helicopter
This study investigated the effect of pipe slide on vibration behavior of piping systems to consider modeling of pipe support structures beyond the yield point for seismic response analysis. A piping system with frame-type support structures and a lumped mass was vibrated on a shaking table with random waves which had maximum accelerations from 30gal to 400gal. The acceleration dependencies of resonance frequency, response reduction and damping factor were measured. As a result, the acceleration dependencies of the piping vibration behavior were demonstrated. Moreover, it was clarified that the acceleration dependencies differed between resonance modes in the horizontal directions and the resonance mode in the vertical direction. First, the resonance frequencies decreased when the input acceleration increased. The resonance frequencies for the horizontal vibration modes were decreased when the input acceleration increased. On the other hand, the resonance frequency for the vertical vibration mode was decreased more at the large input acceleration than for the horizontal vibration modes. Within the acceleration of this study, however, the resonance frequencies for the vertical vibration mode were almost the same values. In a comparison with the natural frequency of modal analysis performed in a conventional manner, the analysis results for the horizontal vibration modes were estimated to be lower than the experimental result. On the other hands, the analysis result for the vertical vibration mode was estimated to be higher than the experimental result. Next, the damping factor increased when the input acceleration increased. The damping factors for the horizontal vibration modes were increased to 3% at the 200gal input acceleration. On the other hand, the damping factors for the vertical vibration mode were also increased but did not show a constant value as occurred for the horizontal vibration modes. Moreover, all of the damping factors measured in this study were
Vibration-induced displacement using high-frequency resonators and friction layers
Thomsen, Jon Juel
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...
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
Vibration-induced displacement using high-frequency resonators and friction layers
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...
Frequency Analysis of Torsion Vibration of Hard Rubbers under Finite Deformations
Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Cibulka, Jan; Košina, Jan
Praha : Institute of Theoretical and Applied Mechanics ASCR, v. v. i, 2015 - (Náprstek, J.; Fischer, C.). s. 302-303 ISBN 978-80-86246-42-0. ISSN 1805-8248. [ Engineering mechanics 2015 /21./. 11.05.2015-14.05.2015, Svratka] Institutional support: RVO:61388998 Keywords : hard rubber * torsion vibration * large deformation * rheology * parameter identification Subject RIV: BI - Acoustics
The influence of crystal defects on the phonon spectra was studied for fcc lead using superconducting tunneling spectroscopy. The theory predicts low frequency modes for the vibrational states of interstitials in (100) dumbbell configuration. Low temperature irradiation of superconducting point contacts with fast ions (point contact thickness small compared to the average ion range) showed radiation-induced structures in the low-energy part of the Eliashberg function for lead. These resonant modes are reduced by annealing at 18.5 K; they are attributed to small interstitial clusters. The radiation-induced structures are completely removed by room temperature annealing. (orig.)
Remick, Kevin; Dane Quinn, D.; Michael McFarland, D.; Bergman, Lawrence; Vakakis, Alexander
2016-05-01
The authors investigate a vibration-based energy harvesting system utilizing essential (nonlinearizable) nonlinearities and electromagnetic coupling elements. The system consists of a grounded, weakly damped linear oscillator (primary system) subjected to a single impulsive load. This primary system is coupled to a lightweight, damped oscillating attachment (denoted as nonlinear energy sink, NES) via a neodymium magnet and an inductance coil, and a piano wire, which generates an essential geometric cubic stiffness nonlinearity. Under impulsive input, the transient damped dynamics of this system exhibit transient resonance captures (TRCs) causing intentional large-amplitude and high-frequency instabilities in the response of the NES. These TRCs result in strong energy transfer from the directly excited primary system to the light-weight attachment. The energy is harvested by the electromagnetic elements in the coupling and, in the present case, dissipated in a resistive element in the electrical circuit. The primary goal of this work is to numerically, analytically, and experimentally demonstrate the efficacy of employing this type of intentional high-frequency dynamic instability to achieve enhanced vibration energy harvesting under impulsive excitation.
The recent syntheses of several new elements (including the recent reports of elements 116 and 118), coupled with the controversy surrounding the naming of elements 104--109, have stimulated a great interest in the chemistry of the transactinide elements. This contribution addresses hypothetical hexacarbonyl complex of seaborgium (Sg, element 106), which is predicted to be a 6d-block transition element with six valence electrons, analogous to Cr, Mo, and W. The authors have previously predicted that, if it were to exist, Sg(CO)6 would exhibit metal-carbonyl bonding that is very similar to that in Cr(CO)6, Mo(CO)6, and W(CO)6, and quite unlike that of the unknown valence isoelectronic actinide complex U(CO)6. This finding is in accord with the scant experimental data available for Sg. The relativistic DV-Xα method used in the earlier paper facilitated the analysis of the molecular orbitals of Sg(CO)6, but did not allow for the calculation of total-energy properties, such as bond lengths and vibrational frequencies. Here the authors will use the superior methodology they have applied to other transactinide molecules to compare the bond lengths, vibrational frequencies, and CO dissociation energy of hypothetical Sg(CO)6 to those of Mo(CO)6 and W(CO)6
Preferred Frequencies for Coupling of Seismic Waves and Vibrating Tall Buildings
Volkov, Darko; Zheltukhin, Sergey
2014-01-01
We study a model for the so called "city effect" in which an earthquake can be locally enhanced by the collective response of tall buildings in a large city. We use a set of equations coupling vibrations in buildings to motion under the ground. These equations were previously studied exclusively in the case of a finite set of identical, equally spaced, buildings. These two restrictions are lifted in this paper. We may now simulate geometries involving infinitely many buildings as long as an i...
Yukio Takahashi
2011-01-01
Full Text Available To investigate the contribution of body vibrations to the vibratory sensation induced by high-level, complex low-frequency noise, we conducted two experiments. In Experiment 1, eight male subjects were exposed to seven types of low-frequency noise stimuli: two pure tones [a 31.5-Hz, 100-dB(SPL tone and a 50-Hz, 100-dB(SPL tone] and five complex noises composed of the pure tones. For the complex noise stimuli, the sound pressure level of one tonal component was 100 dB(SPL and that of another one was either 90, 95, or 100 dB(SPL. Vibration induced on the body surface was measured at five locations, and the correlation with the subjective rating of the vibratory sensation at each site of measurement was examined. In Experiment 2, the correlation between the body surface vibration and the vibratory sensation was similarly examined using seven types of noise stimuli composed of a 25-Hz tone and a 50-Hz tone. In both the experiments, we found that at the chest and the abdomen, the rating of the vibratory sensation was in close correlation with the vibration acceleration level (VAL of the body surface vibration measured at each corresponding location. This was consistent with our previous results and suggested that at the trunk of the body (the chest and the abdomen, the mechanoreception of body vibrations plays an important role in the experience of the vibratory sensation in persons exposed to high-level low-frequency noise. At the head, however, no close correlation was found between the rating of the vibratory sensation and the VAL of body surface vibration. This suggested that at the head, the perceptual mechanisms of vibration induced by high-level low-frequency noise were different from those in the trunk of the body.
Kemaneci, Efe; Booth, Jean-Paul; Chabert, Pascal; van Dijk, Jan; Mussenbrock, Thomas; Brinkmann, Ralf Peter
2016-04-01
Vibrational levels of molecular oxygen, O2(v radio-frequency oxygen plasma with a global modelling approach. The model is benchmarked against a variety of pressure-, power- and time-resolved measurements of several inductive and asymmetric capacitive discharges available in the literature, and a good agreement is obtained. The sensitivity of the model with respect to the vibrational kinetics, the wall reactions and the spatial inhomogeneity of the charged particles are presented. The simulations without the vibrational levels are also shown for the sake of comparison.
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.
张贞; 郭源
2012-01-01
Langmuir monolayer and Gibbs layer exhibit surface-active properties and it can be used as simple model systems to investigate the physicochemical properties of biological membranes. In this report, we presented the OH stretching vibration of H2O in the 4＂-n-pentyl-4-cyano-p-terphenyl （5CT）, nonadecanenitrile （C18CN） Langmuir monolayer and compared them with CH3CN Gibbs layer at the air/water interface with polarization SFG-VS. This study demonstrated that the hydrogen bond network is different in the Langmuir monolayer of 5CT, C18CN from CH3CN Gibbs layer at the air/water interface which showed two different water structures on the different surface layer. The results provided a deeper insight into understanding the hydrogen bond on the interfaces.
Koroleva, L. A.; Tyulin, V. I.; Matveev, V. K.; Pentin, Yu. A.
2013-05-01
B3LYP, MP2, CCSD(T), and MP4/MP2 in the 6-311G( d, p), 6-311++G( d, p), cc-pVTZ, aug-cc-pVTZ bases used to calculate the transition frequencies of torsional vibration of trans- and cis-isomers of acrolein in the ground electronic state ( S 0) are analyzed. It is found that for trans-isomers, all methods of calculation except for B3LYP in the cc-pVTZ basis yield good agreement between the calculated and experimental values. It is noted that for the cis-isomer of acrolein, no method of calculation confirms the experimental value of the frequency of torsional vibration (138 cm-1). It is shown that the calculated and experimental values for obertones at 273.0 cm-1 and other transitions of torsional vibration are different for this isomer in particular. However, it is established that in some calculation methods (B3LYP, MP2), the frequency of the torsional vibration of the cis-isomer coincides with another experimental value of this frequency (166.5 cm-1). It is concluded that in analyzing the vibrational structure of the UV spectrum, the calculated and experimental values of its obertone (331.3 cm-1) coincide, along with its frequency. It is also noted that the frequency of torsional vibration for the cis-isomer (166.5 cm-1) can also be found in other experimental works if we change the allocation of torsional transition 18{1/1}.
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.
Sunda, Anurag Prakash; Mondal, Anirban; Balasubramanian, Sundaram
2015-02-14
Protic ionic liquids (PILs) are of great interest as electrolytes in various energy applications. Molecular dynamics simulations of trialkylammonium (with varying alkyl group such as methyl, ethyl, and n-propyl) triflate PILs are performed to characterize the influence of the alkyl group on the acidic site (N-H) of the ammonium cation. Spatial distribution function of anions over this site on the cation reveals significant influence of the length of alkyl tail on intermolecular structure. Vibrational density of states and normal modes are calculated for bulk liquids to probe atomic displacements in the far infrared region. The observed N-H···O hydrogen bond stretching vibration in 155-165 cm(-1) frequency region agrees well with experiments. Trends in electrical conductivity calculated using Nernst-Einstein and Green-Kubo relation are in qualitative agreement with experiments. The self-diffusion coefficient and the electrical conductivity is highest for N,N-dimethyl-N-ethylammonium triflate ([N112][TfO]) and is lowest for N,N-di-n-propyl-N-methylammonium triflate ([N133][TfO]) IL. PMID:25585541
Meng Zhan
Full Text Available The structure-dynamics-function has become one of central problems in modern sciences, and it is a great challenge to unveil the organization rules for different dynamical processes on networks. In this work, we study the vibration spectra of the classical mass spring model with different masses on complex networks, and pay our attention to how the mass spatial configuration influences the second-smallest vibrational frequency (ω2 and the largest one (ωN. For random networks, we find that ω2 becomes maximal and ωN becomes minimal if the node degrees are point-to-point-positively correlated with the masses. In these cases, we call it point-to-point matching. Moreover, ω2 becomes minimal under the condition that the heaviest mass is placed on the lowest-degree vertex, and ωN is maximal as long as the lightest mass is placed on the highest-degree vertex, and in both cases all other masses can be arbitrarily settled. Correspondingly, we call it single-point matching. These findings indicate that the matchings between the node dynamics (parameter and the node position rule the global systems dynamics, and sometimes only one node is enough to control the collective behaviors of the whole system. Therefore, the matching rules might be the common organization rules for collective behaviors on networks.
Time-frequency data fusion technique with application to vibration signal analysis
Peng, Z. K.; Zhang, W. M.; Lang, Z. Q.; Meng, G.; Chu, F. L.
2012-05-01
To overcome the inherent deficiencies of conventional time-frequency analysis (TFA) methods, i.e., different TFA methods or the same TFA method with different control parameters will present different results for the same target signal, a novel scheme named as the time-frequency data fusion (TFDF) is developed in this study by extending the idea of data fusion technique. By combining the results produced by two or more different TFA methods, the TFDF technique can present a more accurate time-frequency presentation for the target signal than what can be achieved by any individual TFA method. Therefore, the TFDF has potential to render a significantly improved time-frequency representation and greatly facilitates extracting time-frequency features of target signals. This will promote the applications of TFA in engineering practices and make TFA methods more acceptable to field engineers. The effectiveness of the TFDF technique is validated by three numerical case studies and the analysis of a rubbing-impact signal collected from a rotor test rig.
XIAO Hai; LI Jun
2008-01-01
Benchmark calculations on the molar atomization enthalpy, geometry, and vibrational frequencies of uranium hexafluoride (UF6) have been performed by using relativistic density functional theory (DFT) with various levels of relativistic effects, different types of basis sets, and exchange-correlation functionals. Scalar relativistic effects are shown to be critical for the structural properties. The spin-orbit coupling effects are important for the calculated energies, but are much less important for other calculated ground-state properties of closed-shell UF6. We conclude through systematic investigations that ZORA- and RECP-based relativistic DFT methods are both appropriate for incorporating relativistic effects. Comparisons of different types of basis sets (Slater, Gaussian, and plane-wave types) and various levels of theoretical approximation of the exchange-correlation functionals were also made.
Ge, Aimin; Matsusaki, Michiya; Qiao, Lin; Akashi, Mitsuru; Ye, Shen
2016-04-26
Sum frequency generation (SFG) vibrational spectroscopy was employed to investigate the surface structures of polyelectrolyte multilayers (PEMs) constructed by sequentially alternating adsorption of poly(diallyldimethylammonium chloride) (PDDA) and poly(styrenesulfonate) (PSS). It was found that the surface structures and surface charge density of the as-deposited PEMs of PDDA/PSS significantly depend on the concentration of sodium chloride (NaCl) present in the polyelectrolyte solutions. Furthermore, it was found that the surface structure of the as-deposited PEMs is in a metastable state and will reach the equilibrium state by diffusion of the polyelectrolyte chain after an aging process, resulting in a polyelectrolyte mixture on the PEM surfaces. PMID:27045932
Spin Relaxation Caused by Thermal Excitations of High Frequency Modes of Cantilever Vibrations
Berman, G P; Rugar, D; Tsifrinovich, V I
2003-01-01
We consider the process of spin relaxation in the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. We simulated the spin relaxation caused by thermal excitations of the high frequency cantilever modes in the region of the Rabi frequency of the spin sub-system. The minimum relaxation time obtained in our simulations is greater but of the same order of magnitude as one measured in recent experiments. We demonstrated that using a cantilever with nonuniform cross-sectional area may significantly increase spin relaxation time.
Using strong nonlinearity and high-frequency vibrations to control effective mechanical stiffness
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......: Combining 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....
Vibrational power flow and structural intensity: Measurements and limitations at low frequencies
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 are...
Romcevic, N., E-mail: romcevi@ipb.ac.r [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Kostic, R.; Hadzic, B.; Romcevic, M. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Kuryliszyn-Kudelska, I.; Dobrowolski, W.D. [Institute of Physics PAS, Al. Lotnikow 32/46, 02/668 Warsaw (Poland); Narkiewicz, U.; Sibera, D. [Szcecin University of Tehnology, Institute of Chemical and Environmental Engineering, Puleskiego 10, 70-322 Szczecin, Warsaw (Poland)
2010-10-08
Research highlights: Nanocrystaline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe{sub 2}O{sub 3}, ZnFe{sub 2}O{sub 4}) and the mean crystalline size (8-52 nm). Small amount (5 wt.%) of Fe{sub 2}O{sub 3} at the beginning of the synthesis results in forming of ZnFe{sub 2}O{sub 4} nanoparticles. Large amount (90 wt.%) of Fe{sub 2}O{sub 3} at the beginning of the synthesis results in forming Fe{sub 2}O{sub 3} nanoparticles. Both samples contain ZnO phase which is not registered by XRD, but is clearly seen in the Raman spectra. Main characteristics of experimental Raman spectrum in 200-1600 cm{sup -1} spectral region are: sharp peak at 436 cm{sup -1} and broad two-phonon structure at {approx}1150 cm{sup -1}, typical for ZnO; broad structure below 700 cm{sup -1} that has different position and shape in case of ZnFe{sub 2}O{sub 4} or Fe{sub 2}O{sub 3} nanoparticles. In low-frequency Raman spectra of ZnFe{sub 2}O{sub 4} nanoparticles registered peaks agree well with the calculated frequencies of acoustic phonons. As a result we identified (0,2), (0,0), (2,2) and (1,0) modes. - Abstract: Nanocrystaline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe{sub 2}O{sub 3}, ZnFe{sub 2}O{sub 4}) and the mean crystalline size (8-52 nm). In this paper we report the experimental spectra of Raman scattering. Main characteristics of experimental Raman spectrum in 200-1600 cm{sup -1} spectral region are: sharp peak at 436 cm{sup -1} and broad two-phonon structure at {approx}1150 cm{sup -1}, typical for ZnO; broad structure below 700 cm{sup -1} that has different position and shape in case of ZnFe{sub 2}O{sub 4} or Fe{sub 2}O{sub 3} nanoparticles. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles
Viana, Rommel B.; Ribeiro, Gabriela L. O.; Santos, Sinara F. F.; Quintero, David E.; Viana, Anderson B.; da Silva, Albérico B. F.; Moreno-Fuquen, Rodolfo
2016-06-01
The aim of this investigation was to determine the molecular properties and provide an interpretation of the vibrational mode couplings of these two paracetamol analogues: 2-bromo-2-methyl-N-(4-nitrophenyl)-propanamide and 2-bromo-2-methyl-N-p-tolyl-propanamide. E/Z isomers, keto/enol unimolecular rearrangement and prediction of the transition state structures in each mechanism were also assessed using the Density Functional Theory (DFT). The DFT estimates a high energy gap between E and Z isomers (9-11 kcal·mol- 1), with barrier heights ranging from 16 to 19 kcal·mol- 1. In contrast, the barrier energies on the keto/enol isomerization are almost 10 kcal·mol- 1 higher than those estimated for the E/Z rearrangement. The kinetic rate constant was also determined for each reaction mechanism. Natural bond orbital analysis and the quantum theory of atoms in molecules were used to interpret the intramolecular hydrogen bonds and to understand the most important interactions that govern the stabilization of each isomer. Furthermore, an analysis of the atomic charge distribution using different population methodologies was also performed.
Viana, Rommel B; Ribeiro, Gabriela L O; Santos, Sinara F F; Quintero, David E; Viana, Anderson B; da Silva, Albérico B F; Moreno-Fuquen, Rodolfo
2016-06-01
The aim of this investigation was to determine the molecular properties and provide an interpretation of the vibrational mode couplings of these two paracetamol analogues: 2-bromo-2-methyl-N-(4-nitrophenyl)-propanamide and 2-bromo-2-methyl-N-p-tolyl-propanamide. E/Z isomers, keto/enol unimolecular rearrangement and prediction of the transition state structures in each mechanism were also assessed using the Density Functional Theory (DFT). The DFT estimates a high energy gap between E and Z isomers (9-11kcal·mol(-1)), with barrier heights ranging from 16 to 19kcal·mol(-1). In contrast, the barrier energies on the keto/enol isomerization are almost 10kcal·mol(-1) higher than those estimated for the E/Z rearrangement. The kinetic rate constant was also determined for each reaction mechanism. Natural bond orbital analysis and the quantum theory of atoms in molecules were used to interpret the intramolecular hydrogen bonds and to understand the most important interactions that govern the stabilization of each isomer. Furthermore, an analysis of the atomic charge distribution using different population methodologies was also performed. PMID:26974474
Micro-lateral extrusion of Zr55Cu30Al10Ni5 bulk metallic glass under low-frequency vibration loading
Li Jinyang
2015-01-01
Full Text Available The effect of vibration on the micro-forming ability of Zr55Cu30Al10Ni5 bulk metallic glass in its supercooled liquid region was studied. The experiment of micro-extrusion was carried out under different amplitude (38 ∼ 760 N and different frequency (0.1 ∼ 2.0 Hz at a fixed temperature of 723 K. The extrusion length was taken as a measure to characterize the micro-forming ability. Results reveal that the extrusion length of bulk metallic glass is effectively improved under vibration loading, and increases with increasing loading frequency and amplitude, whereas the frequency dependence is stronger. The viscosity of bulk metallic glass declines under vibration loading because of a larger free volume concentration and surface effect caused by vibration. This research indicates that the vibration forming is an effective method to enhance the micro-forming ability of bulk metallic glasses.
Sen, Osman Taha; Dreyer, Jason T.; Singh, Rajendra
2014-12-01
In this article, a feasibility study of controlling the low frequency torque response of a disc brake system with modulated actuation pressure (in the open loop mode) is conducted. First, a quasi-linear model of the torsional system is introduced, and analytical solutions are proposed to incorporate the modulation effect. Tractable expressions for three different modulation schemes are obtained, and conditions that would lead to a reduction in the oscillatory amplitudes are identified. Second, these conditions are evaluated with a numerical model of the torsional system with clearance nonlinearity, and analytical solutions are verified in terms of the trends observed. Finally, a laboratory experiment with a solenoid valve is built to modulate actuation pressure with a constant duty cycle, and time-frequency domain data are acquired. Measurements are utilized to assess analytical observations, and all methods show that the speed-dependent brake torque amplitudes can be altered with an appropriate modulation of actuation pressure.
Covert, Paul A; FitzGerald, William R; Hore, Dennis K
2012-07-01
We present a visible-infrared sum-frequency spectroscopic technique that is capable of simultaneously determining the magnitude and phase of the sample response from a single set of experimental conditions. This is especially valuable in cases where the phase stability is high, as in collinear beam geometries, as it enables multiple experiments to be performed without re-measuring the local oscillator phase or the reference phase. After illustrating the phase stability achievable with such a geometry, we provide a technique for quantitatively determining the magnitude and phase from a single set of two-dimensional spectral-temporal interference fringes. A complete demonstration is provided for the C-H stretching frequency region at the surface of an octadecyltricholosilane film. PMID:22779640
Howell, Caitlin
2011-01-01
The molecular-level understanding of biological molecules on solid surfaces is critical in areas including medicine, biologically-based industry, and the development of biotechnologies. In order to gain further knowledge of the orientation and organization of biological molecules adsorbed on surfaces, we used the label-free, interface-specific technique of sum-frequency generation (SFG) spectroscopy. This technique has the distinct advantage of being able to be operated in situ as well as ex ...
A Torcasio; GH van Lenthe; Van Oosterwyck, H
2008-01-01
Mechanical loading is one of the key factors that influence bone mass and the osseointegration of bone-anchored implants. From a clinical point of view, mechanical stimulation may be used to enhance bone strength and implant osseointegration. Among the many loading parameters that influence the response to mechanical loading, the effects of loading frequency and rate have been investigated in many studies. In this paper the most relevant animal studies that have addressed the effect of loadin...
Double diffusion convection under sinusoidal modulations of low-frequency vibrations
Yan, Yu; Viviani, Antonio; Saghir, M. Ziad
2008-09-01
Double diffusion convection features the coupling of diffusion fluxes driven by the temperature and concentration gradients and the simultaneous existence of the natural convection driven by the buoyancy force. This paper studies the double diffusion convection under different modulations of low-frequency g-jitters in order to evaluate the g-jitter effect on diffusion-dominated experiments in space laboratories. The numerical simulation for a binary mixture of water-isopropanol (90:10 wt%) has shown a dependence of the Soret separation on g-jitter frequency and amplitude. Under the same amplitude, the fluctuation of local properties, i.e., velocity, temperature and concentration, is found to intensify as the g-jitter frequency decreases. When both static residual gravity and oscillatory g-jitter exist, the diffusion process is affected by the nonlinear interaction between individual g-jitters. As the amplitude decreases to 1μg, this nonlinearity becomes less significant than it appears in the high-amplitude scenario.
Vibration-based machine condition monitoring with attention to the use of time-frequency methods
Rehorn, Adam G. J.; Orban, Peter E.; Jiang, Jin
2004-03-01
To enable lightly staffed or fully autonomous machining operations, it is essential that both the condition of the cutter and the health of the machine tool system be known. In this paper, the health of the spindle positioning drive (Z axis) on a Proteo D/94 precision machining center is investigated using time, frequency and time-frequency techniques. Investigated is a cogging phenomenon produced as a result of the DC servomotor brushes sticking due to poor design. This incipient fault reduces the accuracy and controllability of the machine tool, and always leads to total drive failure. Thus, it is important to determine the fault signature of the drive so that corrective action may be taken before failure can occur, permanently damaging both the motor and the workpiece. The vibratory signatures of both a healthy and a faulty spindle during translation are analyzed. It is shown that a spindle under fault conditions behaves differently from a healthy one, and that time and time-frequency domain methods provide useful information on the status of the system. This paper lays the groundwork for the development of a future machine condition monitoring system, which can be easily retrofitted to any machine tool system.