WorldWideScience

Sample records for suppress vibrations due

  1. Vibration suppression during input tracking of a flexible manipulator ...

    Indian Academy of Sciences (India)

    The aim of this paper is to investigate the performance of the hybrid controller for end-point vibration suppression of a flexible manipulator, while it is tracking a desired input profile. Due to large structural vibrations, precise control of flexible manipulators is a challenging task. A hybrid controller is used to track large ...

  2. Simultaneous Vibration Suppression and Energy Harvesting

    Science.gov (United States)

    2013-08-15

    and clear sky condition (the condition of vibration induced during normal flight) are simulated using the Dryden PSD signal for both clear sky and...a cc ele ra tio n [ g ] Cumulus Cloud Wind Gust Clear Sky Normal Vibration Figure 4 Vibration response due to flow simulated using Dryden ... John Wiley & Sons, Ltd., Chichester, West Sussex, UK, 416 pp. (ISBN 978-0-470-68254-8) Inman, Daniel J., 2009. Engineering (ME 3504 Vibrations

  3. Fluid Surface Damping: A Technique for Vibration Suppression of Beams

    Directory of Open Access Journals (Sweden)

    Hany Ghoneim

    1997-01-01

    Full Text Available A fluid surface damping (FSD technique for vibration suppression of beamlikestructures is proposed. The technique is a modification of the surface layer damping method. Two viscoelastic surface layers containing fluid-filled cavities are attached symmetrically to the opposite surfaces of the beam. The cavities on one side are attached to the corresponding cavities on the other side via connection passages. As the beam vibrates, the fluid is pumped back and forth through the connecting passages. Therefore, in addition to the viscoelastic damping provided by the surface layers, the technique offers viscous damping due to the fluid flow through the passage. A mathematical model for the proposed technique is developed, normalized, and solved in the frequency domain to investigate the effect of various parameters on the vibration suppression of a cantilever beam. The steady-state frequency response for a base white-noise excitation is calculated at the beam's free tip and over a frequency range containing the first five resonant frequencies. The parameters investigated are the flow-through passage viscous resistance, the length and location of the layers, the hydraulic capacitance of the fluid-filled cavities, and inertia of the moving fluid (hydraulic inertance. Results indicate that the proposed technique has promising potential in the field of vibration suppression of beamlike structures. With two FSD elements, all peak vibration amplitudes can be well suppressed over the entire frequency spectrum studied.

  4. Wireless Inductive Power Device Suppresses Blade Vibrations

    Science.gov (United States)

    Morrison, Carlos R.; Provenza, Andrew J.; Choi, Benjamin B.; Bakhle, Milind A.; Min, James B.; Stefko, George L.; Duffy, Kirsten P.; Fougers, Alan J.

    2011-01-01

    Vibration in turbomachinery can cause blade failures and leads to the use of heavier, thicker blades that result in lower aerodynamic efficiency and increased noise. Metal and/or composite fatigue in the blades of jet engines has resulted in blade destruction and loss of lives. Techniques for suppressing low-frequency blade vibration, such as gtuned circuit resistive dissipation of vibratory energy, h or simply "passive damping," can require electronics incorporating coils of unwieldy dimensions and adding unwanted weight to the rotor. Other approaches, using vibration-dampening devices or damping material, could add undesirable weight to the blades or hub, making them less efficient. A wireless inductive power device (WIPD) was designed, fabricated, and developed for use in the NASA Glenn's "Dynamic Spin Rig" (DSR) facility. The DSR is used to simulate the functionality of turbomachinery. The relatively small and lightweight device [10 lb (approx.=4.5 kg)] replaces the existing venerable and bulky slip-ring. The goal is the eventual integration of this technology into actual turbomachinery such as jet engines or electric power generators, wherein the device will facilitate the suppression of potentially destructive vibrations in fan blades. This technology obviates slip rings, which require cooling and can prove unreliable or be problematic over time. The WIPD consists of two parts: a remote element, which is positioned on the rotor and provides up to 100 W of electrical power to thin, lightweight piezoelectric patches strategically placed on/in fan blades; and a stationary base unit that wirelessly communicates with the remote unit. The base unit supplies inductive power, and also acts as an input and output corridor for wireless measurement, and active control command to the remote unit. Efficient engine operation necessitates minimal disturbance to the gas flow across the turbine blades in any effort to moderate blade vibration. This innovation makes it

  5. Suppression of friction by mechanical vibrations.

    Science.gov (United States)

    Capozza, Rosario; Vanossi, Andrea; Vezzani, Alessandro; Zapperi, Stefano

    2009-08-21

    Mechanical vibrations are known to affect frictional sliding and the associated stick-slip patterns causing sometimes a drastic reduction of the friction force. This issue is relevant for applications in nanotribology and to understand earthquake triggering by small dynamic perturbations. We study the dynamics of repulsive particles confined between a horizontally driven top plate and a vertically oscillating bottom plate. Our numerical results show a suppression of the high dissipative stick-slip regime in a well-defined range of frequencies that depends on the vibrating amplitude, the normal applied load, the system inertia and the damping constant. We propose a theoretical explanation of the numerical results and derive a phase diagram indicating the region of parameter space where friction is suppressed. Our results allow to define better strategies for the mechanical control of friction.

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

    Science.gov (United States)

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

    2015-01-28

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

  7. Vibration suppression of composite laminated beams using distributed piezoelectric patches

    International Nuclear Information System (INIS)

    Foda, M A; Almajed, A A; ElMadany, M M

    2010-01-01

    The focus of this paper is to develop an analytical and straightforward approach to suppress the steady state transverse vibration of a symmetric cross-ply laminated composite beam that is excited by an external harmonic force. This is achieved by bonding patches of piezoelectric material at selected locations along the beam. The governing equations for the system are formulated and the dynamic Green's functions are used to obtain an exact solution for the problem. A scheme is proposed for determining the values of the driving voltages, the dimensions of the PZT patches and their locations along the beam, in order to confine the vibration in a certain chosen region where the vibration is not harmful and leave the other chosen region stationary or vibrating with very small amplitudes. Beams with different boundary conditions are considered. Numerical case studies are presented to verify the utility of the proposed scheme

  8. Cable Vibration due to Ice Accretions

    DEFF Research Database (Denmark)

    Gjelstrup, Henrik; Georgakis, Christos; Larsen, Allan

    investigation behind the causes of this relatively isolated hanger vibration event on the Great Belt East Bridge is presented. Furthermore a stability criterion for a 3DOF bluff body is proposed. One of the main assumptions of the investigation is that icy conditions may have contributed in some way to large...

  9. A smart dynamic vibration absorber for suppressing the vibration of a string supported by flexible beams

    Science.gov (United States)

    Nambu, Yohsuke; Yamamoto, Shota; Chiba, Masakatsu

    2014-02-01

    This study aims to effectively and robustly suppress the vibration of tension-stabilized structures (TSSs) using a smart dynamic vibration absorber (DVA). In recent years, a strong need has emerged for high-precision and high-functionality space structural systems for realizing advanced space missions. TSSs have attracted attention in this regard as large yet lightweight structural systems with high storage efficiency. A fundamental issue in the application of TSSs is vibration control of strings, of which TSSs are predominantly composed. In particular, the suppression of microvibrations is difficult because the deformation is almost perpendicular to the direction of vibration. A DVA is an effective device for suppressing microvibrations. However, the damping performance is sensitive to changes in dynamic properties. Furthermore, aging degradation and temperature dependence negatively affect DVA performance. This study aimed to develop a smart, active DVA with self-sensing actuation to improve robustness. A small cantilever with a piezoelectric transducer was utilized as a smart DVA. Numerical simulations and experiments showed that a passive DVA and the smart DVA suppressed vibrations but that the smart DVA showed improved effectiveness and robustness.

  10. Optimal Active Vibration Suppression of Smart Composite Wind Turbine Blades

    Science.gov (United States)

    Abd El-Maksoud Mohamed, Sherif Ibrahim

    The purpose of this study is to apply active vibration control technique numerically for suppressing the vibrational level of a horizontal axis wind turbine blade. Two systems are studied to apply active vibration control on the wind turbine blade model, the first is a uniform cantilever beam and the other system is a non-uniform (tapered) cantilever beam. A single piezoelectric actuator and sensor are bonded on the upper and lower surface of the systems, respectively. The vibration analysis and dynamic characteristics of smart systems are obtained using approximate analytical methods. The entire structure is modeled in the state space form using the state space method, generalized coordinates and piezoelectric theory. Two types of controllers are designed to study the performance of the piezoelectric active controller. The first is a Proportional-Derivative (PD) controller and the other type is a Linear Quadratic Regulator (LQR). The Linear Quadratic Regulator (LQR) demonstrates better results for vibration suppression. The MATLAB code Simulink is used to simulate the different cases.

  11. An adaptive vibration control method to suppress the vibration of the maglev train caused by track irregularities

    Science.gov (United States)

    Zhou, Danfeng; Yu, Peichang; Wang, Lianchun; Li, Jie

    2017-11-01

    The levitation gap of the urban maglev train is around 8 mm, which puts a rather high requirement on the smoothness of the track. In practice, it is found that the track irregularity may cause stability problems when the maglev train is traveling. In this paper, the dynamic response of the levitation module, which is the basic levitation structure of the urban maglev train, is investigated in the presence of track irregularities. Analyses show that due to the structural configuration of the levitation module, the vibration of the levitation gap may be amplified and "resonances" may be observed under some specified track wavelengths and train speeds; besides, it is found that the gap vibration of the rear levitation unit in a levitation module is more significant than that of the front levitation unit, which agrees well with practice. To suppress the vibration of the rear levitation gap, an adaptive vibration control method is proposed, which utilizes the information of the front levitation unit as a reference. A pair of mirror FIR (finite impulse response) filters are designed and tuned by an adaptive mechanism, and they produce a compensation signal for the rear levitation controller to cancel the disturbance brought by the track irregularity. Simulations under some typical track conditions, including the sinusoidal track profile, random track irregularity, as well as track steps, indicate that the adaptive vibration control scheme can significantly reduce the amplitude of the rear gap vibration, which provides a method to improve the stability and ride comfort of the maglev train.

  12. Vibration Suppression of Electronic Box by a Dual Function Piezoelectric Energy Harvester-Tuned Vibration Absorber

    Directory of Open Access Journals (Sweden)

    Sajid Rafique

    2014-04-01

    Full Text Available Over the past few years, remarkable developments in piezoelectric materials have motivated many researchers to work in the field of vibration energy harvesting by using piezoelectric beam like smart structures. This paper aimed to present the most recent application of a dual function piezoelectric device which can suppress vibration and harvest vibration energy simultaneously and a brief illustration of conventional mechanical and electrical TVAs (Tuned Vibration Absorber. It is shown that the proposed dual function device combines the benefits of conventional mechanical and electrical TVAs and reduces their relative disadvantages. Conversion of mechanical energy into electrical energy introduces damping and, hence, the optimal damping required by this TVA is generated by the energy harvesting effects. This paper presents the methodology of implementing the theory of 'electromechanical' TVAs to suppress the response of any real world structure. The work also illustrates the prospect of extensive applications of such novel "electromechanical" TVAs in defence and industry. The results show that the optimum degree of vibration suppression of an electronic box is achieved by this dual function TVA through suitable tuning of the attached electrical circuitry

  13. An electromagnetic inerter-based vibration suppression device

    International Nuclear Information System (INIS)

    Gonzalez-Buelga, A; Clare, L R; Neild, S A; Jiang, J Z; Inman, D J

    2015-01-01

    This paper describes how an inerter-based device for structural vibration suppression can be realized using an electromagnetic transducer such as a linear motor. When the motor shaft moves, a difference of voltage is generated across the transducer coil. The voltage difference is proportional to the relative velocity between its two terminals. The electromagnetic transducer will exert a force proportional to current following the Lorentz principle if the circuit is closed around the transducer coil. If an electronic circuit consisting of a capacitor, an inductance and a resistance with the appropriate configuration is connected, the resulting force reflected back into the mechanical domain is equivalent to that achieved by a mechanical inerter-based device. The proposed configuration is easy to implement and very versatile, provided a high quality conversion system with negligible losses. With the use of electromagnetic devices, a new generation of vibration absorbers can be realized, for example in the electrical domain it would be relatively uncomplicated to synthesize multi-frequency or real time tunable vibration absorbers by adding electrical components in parallel. In addition by using resistance emulators in the electrical circuits, part of the absorbed vibration energy can be converted into usable power. Here an electromagnetic tuned inerter damper (E-TID) is tested experimentally using real time dynamic substructuring. A voltage compensation unit was developed in order to compensate for coil losses. This voltage compensation unit requires power, which is acquired through harvesting from the vibration energy using a resistance emulator. A power balance analysis was developed in order to ensure the device can be self sufficient. Promising experimental results, using this approach, have been obtained and are presented in this paper. The ultimate goal of this research is the development of autonomous electromagnetic vibration absorbers, able to harvest energy

  14. Tuneable vibration absorber design to suppress vibrations: An application in boring manufacturing process

    Science.gov (United States)

    Moradi, H.; Bakhtiari-Nejad, F.; Movahhedy, M. R.

    2008-11-01

    Dynamic vibration absorbers are used to reduce the undesirable vibrations in many applications such as electrical transmission lines, helicopters, gas turbines, engines, bridges, etc. Tuneable vibration absorbers (TVA) are also used as semi-active controllers. In this paper, the application of a TVA for suppression of chatter vibrations in the boring manufacturing process is presented. The boring bar is modeled as a cantilever Euler-Bernoulli beam and the TVA is composed of mass, spring and dashpot elements. In addition, the effect of spring mass is considered in this analysis. After formulation of the problem, the optimum specifications of the absorber such as spring stiffness, absorber mass and its position are determined using an algorithm based on the mode summation method. The analog-simulated block diagram of the system is developed and the effects of various excitations such as step, ramp, etc. on the absorbed system are simulated. In addition, chatter stability is analyzed in dominant modes of boring bar. Results show that at higher modes, larger critical widths of cut and consequently more material removal rate (MRR) can be achieved. In the case of self-excited vibration, which is associated with a delay differential equation, the optimum absorber suppresses the chatter and increases the limit of stability.

  15. Abnormal vibration of turbine due to oil whip

    International Nuclear Information System (INIS)

    Koo, Jae Raeyang; Hwang, Jae Hyeon

    2001-01-01

    Almost all rotating machinery has bearings. Bearing is one of the most important part of rotating machinery. Vibration of rotating machinery depend on its bearing conditions. Bearing conditions are following; oil gap, bearing type, bearing temperature, bearing oil condition. Especially, bearing oil condition influences on rotating machinery vibration directly. In this paper we have discussed the abnormal vibration of turbine due to oil condition. Oil whip problem was occurred in the certain power plant and we had solved this problem through the control of operating values and alignment

  16. The Analysis and Suppression of the spike noise in vibrator record

    Science.gov (United States)

    Jia, H.; Jiang, T.; Xu, X.; Ge, L.; Lin, J.; Yang, Z.

    2013-12-01

    suppressed. After this process, it can reduce the effection of spike noise in the uncorrelated record to improve the SNR. At present, because the memory space of vibrator uncorrelated data is always very large, in order to reduce acquisition costs, we usually record correlated data directly. It's reasonable if there is no strong spike sneaking into uncorrelated record. However, due to the fact that the random spike in the background is not avoidable in the acquisition process, and the instantaneous input energy of the vibrator is probably smaller than spike noise, which makes the uncorrelated data contain a certain amount of spike noise, it severely reduces the acquisition quality of vibrator if there is no noise suppression module beforehand. Of course, the suppressing process of spike noise can be carried out in the field acquisition or data processing stage. In the field of vibrator acquisition system, we can use the spike noise suppression before the correlated module, so that it can directly record correlated data without the spike affection. If in the stage of data processing, it is necessary to record uncorrelated data.

  17. Controlled Suppression of Wear on the Nanoscale by Ultrasonic Vibrations.

    Science.gov (United States)

    Pedraz, Patricia; Wannemacher, Reinhold; Gnecco, Enrico

    2015-09-22

    Wear on the nanoscale, as evidenced by the formation of periodic ripples on a model polystyrene thin film while a sharp tip is sliding on it with a normal force in the μN range, is shown to be suppressed by the application of ultrasonic vibrations of amplitude Aexc. An accurate calibration of the transducer excitation amplitude is achieved by a home-built setup based on a laser Doppler vibrometer. The corrugation of the typical ripple pattern that is formed in the absence of vibrations is reduced when the excitation frequency matches the contact resonance of the system and Aexc progressively increases. Above a critical value of Aexc, the ripples completely disappear, while the friction levels off at a finite value determined by the normal force and the vibration amplitude. This value can be significantly smaller than the value of the macroscopic friction coefficient. In addition to the control of wear in general, this opens up the possibility of controlled nanolithography with improved accuracy.

  18. Vibration phenomena in large scale pressure suppression tests

    International Nuclear Information System (INIS)

    Aust, E.; Boettcher, G.; Kolb, M.; Sattler, P.; Vollbrandt, J.

    1982-01-01

    Structure und fluid vibration phenomena (acceleration, strain; pressure, level) were observed during blow-down experiments simulating a LOCA in the GKSS full scale multivent pressure suppression test facility. The paper describes first the source related excitations during the two regimes of condensation oscillation and of chugging, and deals then with the response vibrations of the facility's wetwell. Modal analyses of the wetwell were run using excitation by hammer and by shaker in order to separate phenomena that are particular to the GKSS facility from more general ones, i.e. phenomena specific to the fluid related parameters of blowdown and to the geometry of the vent pipes only. The lowest periodicities at about 12 and 16 Hz stem from the vent acoustics. A frequency of about 36 to 38 Hz prominent during chugging seems to result from the lowest local models of two of the wetwell's walls when coupled by the wetwell pool. Further peaks found during blowdown in the spectra of signals at higher frequencies correspond to global vibration modes of the wetwell. (orig.)

  19. Qualification of engine-mounted components due to operational vibration

    International Nuclear Information System (INIS)

    Lee, B.J.; Bayat, A.

    1994-01-01

    The Emergency Diesel Generator (EDG) in a Nuclear Power Plant is considered to be an essential component of the plant for its safe operation. Failures of auxiliary components directly mounted on the EDG creates costly repairs, and compromises the engine's availability and reliability. Although IEEE-323 and Section III of the ASME code require addressing of safety-related components due to mechanically induced vibration, very few guidelines exist in the nuclear industry to show how this may be accounted for. Most engine vendors rely on the empirical experience data as the basis of their evaluation for vibration. Upgrade of engine controls, addition of monitoring components and other engine modifications require design and installation of new mechanical and electrical components to be mounted directly on the engine. This necessitates the evaluation of such components for engine-induced vibration which is considered to be one of the most severe design parameters. This paper presents a methodology to evaluate three categories of components; structural, mechanical, and electrical under engine vibration. The discussion for the characteristics and manipulation of engine vibration profile to be used for each component evaluation is also given. In addition, the suitability of analytical verses testing approaches is discussed for each category. An example application of the methodology is presented for a typical EDG which is currently undergoing major controls upgrade and monitoring modification

  20. Active Suppression of Drilling System Vibrations For Deep Drilling

    Energy Technology Data Exchange (ETDEWEB)

    Raymond, David W.; Blankenship, Douglas A.; Buerger, Stephen; Mesh, Mikhail; Radigan, William Thomas; Su, Jiann-Cherng

    2015-10-01

    The dynamic stability of deep drillstrings is challenged by an inability to impart controllability with ever-changing conditions introduced by geology, depth, structural dynamic properties and operating conditions. A multi-organizational LDRD project team at Sandia National Laboratories successfully demonstrated advanced technologies for mitigating drillstring vibrations to improve the reliability of drilling systems used for construction of deep, high-value wells. Using computational modeling and dynamic substructuring techniques, the benefit of controllable actuators at discrete locations in the drillstring is determined. Prototype downhole tools were developed and evaluated in laboratory test fixtures simulating the structural dynamic response of a deep drillstring. A laboratory-based drilling applicability demonstration was conducted to demonstrate the benefit available from deployment of an autonomous, downhole tool with self-actuation capabilities in response to the dynamic response of the host drillstring. A concept is presented for a prototype drilling tool based upon the technical advances. The technology described herein is the subject of U.S. Patent Application No. 62219481, entitled "DRILLING SYSTEM VIBRATION SUPPRESSION SYSTEMS AND METHODS", filed September 16, 2015.

  1. Topological material layout in plates for vibration suppression and wave propagation control

    DEFF Research Database (Denmark)

    Larsen, Anders Astrup; Laksafoss, B.; Jensen, Jakob Søndergaard

    2009-01-01

    We propose a topological material layout method to design elastic plates with optimized properties for vibration suppression and guided transport of vibration energy. The gradient-based optimization algorithm is based on a finite element model of the plate vibrations obtained using the Mindlin...

  2. Vibration suppression of a rotating flexible cantilever pipe conveying fluid using piezoelectric layers

    Directory of Open Access Journals (Sweden)

    S. Khajehpour

    Full Text Available AbstractIn this study, the governing equations of a rotating cantilever pipe conveying fluid are derived and the longitudinal and lateral induced vibrations are controlled. The pipe considered as an Euler Bernoulli beam with tip mass which piezoelectric layers attached both side of it as sensors and actuators. The follower force due to the fluid discharge causes both conservative and non-conservative work. For mathematical modeling, the Lagrange-Rayleigh-Ritz technique is utilized. An adaptive-robust control scheme is applied to suppress the vibration of the pipe. The adaptive-robust control method is robust against parameter uncertainties and disturbances. Finally, the system is simulated and the effects of varying parameters are studied. The simulation results show the excellent performance of the controller.

  3. Adaptive multimodal vibration suppression using fuzzy-based control with limited structural data

    International Nuclear Information System (INIS)

    Makihara, Kanjuro; Kuroishi, Chikako; Fukunaga, Hisao

    2013-01-01

    We propose a novel fuzzy-based method of adaptive multimodal vibration suppression with limited structural data. The adaptive control consists of fuzzy inference and a semi-active switching approach. We demonstrate it to be applicable to multimodal vibration suppression for vibrating structures, where a single piezoelectric actuator suppresses two modal vibrations simultaneously. Our fuzzy-based semi-active control requires only the structural information of natural frequencies for real-time adaptive feedback, whereas common adaptive controls require highly precise structural models or complete equations of motion. We conduct experiments in semi-active vibration suppression using the proposed fuzzy-based control, and compare the suppression performance of our fuzzy-based approach with conventional controls. The experiments indicate that the proposed fuzzy-based control demonstrates good adaptability when experiencing sudden changes in disturbance excitation, and also demonstrates high suppression performance. The fuzzy-based control can adapt to a wide range of disturbance conditions, both within and outside the range of vibration excitations assumed when the controller is designed. (paper)

  4. Design of external vibration absorber for vibration suppression of milling cutter in processing

    Science.gov (United States)

    Zhang, Ya-hui; Zhang, Nian-song; Wang, Ai-min

    2018-01-01

    A new type of external dynamic vibration absorber is designed to control the vibration at a specific frequency of the milling cutter during the milling process. The structural design of the dynamic vibration absorber and the selection of the corresponding parameters are conducted. The finite element model of the cutter is established and connected with the vibration absorber. The results of the harmonic response analysis of milling cutter before and after the installation of the vibration absorber are compared and show that the vibration absorber can reduce the vibration of the cutter at the resonant frequency, which means it has a good vibration damping performance. The vibration absorber has the advantages of simple structure, convenient frequency modulation and easy installation. This context lay the foundation of further application for damping cutter.

  5. Active Vibration Suppression of a 3-DOF Flexible Parallel Manipulator Using Efficient Modal Control

    Directory of Open Access Journals (Sweden)

    Quan Zhang

    2014-01-01

    Full Text Available This paper addresses the dynamic modeling and efficient modal control of a planar parallel manipulator (PPM with three flexible linkages actuated by linear ultrasonic motors (LUSM. To achieve active vibration control, multiple lead zirconate titanate (PZT transducers are mounted on the flexible links as vibration sensors and actuators. Based on Lagrange’s equations, the dynamic model of the flexible links is derived with the dynamics of PZT actuators incorporated. Using the assumed mode method (AMM, the elastic motion of the flexible links are discretized under the assumptions of pinned-free boundary conditions, and the assumed mode shapes are validated through experimental modal test. Efficient modal control (EMC, in which the feedback forces in different modes are determined according to the vibration amplitude or energy of their own, is employed to control the PZT actuators to realize active vibration suppression. Modal filters are developed to extract the modal displacements and velocities from the vibration sensors. Numerical simulation and vibration control experiments are conducted to verify the proposed dynamic model and controller. The results show that the EMC method has the capability of suppressing multimode vibration simultaneously, and both the structural and residual vibrations of the flexible links are effectively suppressed using EMC approach.

  6. Vibration suppression of a flywheel system using a novel nonlinear vibration absorber with an Euler buckled beam

    Science.gov (United States)

    Haiping, Liu; Wenhua, Shi

    2016-09-01

    The micro-vibration from flywheel system, as one of the main disturbances, has restricted the effective use of high sensitive payloads in satellites. In order to suppress the low- frequency line spectrum from the flywheel, a novel nonlinear vibration absorber (NVA) using Euler buckled beam is developed. The proposed NVA is attached on the supporting structure of the flywheel assembly, aiming to attenuate the line spectrum introduced by the flywheel in operation. A discrete multi-degree-of-freedom dynamic model, which includes the NVA, the flywheel and the supporting structure by taking into account of the gyroscopic effect of the flywheel, is built. The NVA is represented by a linear positive stiffness spring and parallel Euler buckled beams. The systematic dynamic equations with and without the NVA under the micro-vibration from the flywheel, respectively, are solved by using fourth-order Runge-Kutta method in time-domain. In addition, the effects of initial imperfection, oblique angle and damping coefficient of the Euler buckled beam on the vibration suppression performance are studied. The calculating results reveal that a typical nonlinear dynamic absorber for controlling the micro-vibration from the flywheel is constructed successfully based on the provided designing parameters of the Euler buckled beam. Compared with the vibration responses of the combined system with and without the NVA, it can be concluded that the NVA has better attenuation performance. The initial imperfection and damping coefficient of the Euler buckled beam exist optimum values, and with the increase of the oblique angle, the vibration controlling characteristics of the NVA have been improved.

  7. Imposed Rubber Elements for Bladed Wheel Vibration Suppression

    Czech Academy of Sciences Publication Activity Database

    Pešek, Luděk; Půst, Ladislav; Bula, Vítězslav; Cibulka, Jan

    2015-01-01

    Roč. 3, č. 6 (2015), s. 733-741 ISSN 2321-3558 R&D Projects: GA ČR GA101/09/1166 Institutional support: RVO:61388998 Keywords : blade * vibration * damping Subject RIV: BI - Acoustics Impact factor: 0.098, year: 2015

  8. Noncolocated Structural Vibration Suppression Using Zero Annihilation Periodic Control

    Science.gov (United States)

    Bayard, David S.; Boussalis, Dhemetrios

    1993-01-01

    The Zero Annihilation Periodic (ZAP) controller is applied to the problem of vibration control of a noncolocated flexible structure. It is shown that even though the transfer function is nonminimum-phase, a plant inverse controller can be designed which elicits a deadbeat closed-loop response.

  9. Nonlinear gain suppression in semiconductor lasers due to carrier heating

    International Nuclear Information System (INIS)

    Willatzen, M.; Uskov, A.; Moerk, J.; Olesen, H.; Tromborg, B.; Jauho, A.P.

    1991-01-01

    We present a simple model for carrier heating in semiconductor lasers, from which the temperature dynamics of the electron and hole distributions can be calculated. Analytical expressions for two new contributions to the nonlinear gain coefficient ε are derived, which reflect carrier heating due to stimulated emission and free carrier absorption. In typical cases, carrier heating and spectral holeburning are found to give comparable contributions to nonlinear gain suppression. The results are in good agreement with recent measurements on InGaAsP laser diodes. (orig.)

  10. Transient vibration analytical modeling and suppressing for vibration absorber system under impulse excitation

    Science.gov (United States)

    Wang, Xi; Yang, Bintang; Yu, Hu; Gao, Yulong

    2017-04-01

    The impulse excitation of mechanism causes transient vibration. In order to achieve adaptive transient vibration control, a method which can exactly model the response need to be proposed. This paper presents an analytical model to obtain the response of the primary system attached with dynamic vibration absorber (DVA) under impulse excitation. The impulse excitation which can be divided into single-impulse excitation and multi-impulse excitation is simplified as sinusoidal wave to establish the analytical model. To decouple the differential governing equations, a transform matrix is applied to convert the response from the physical coordinate to model coordinate. Therefore, the analytical response in the physical coordinate can be obtained by inverse transformation. The numerical Runge-Kutta method and experimental tests have demonstrated the effectiveness of the analytical model proposed. The wavelet of the response indicates that the transient vibration consists of components with multiple frequencies, and it shows that the modeling results coincide with the experiments. The optimizing simulations based on genetic algorithm and experimental tests demonstrate that the transient vibration of the primary system can be decreased by changing the stiffness of the DVA. The results presented in this paper are the foundations for us to develop the adaptive transient vibration absorber in the future.

  11. The influence of flywheel micro vibration on space camera and vibration suppression

    Science.gov (United States)

    Li, Lin; Tan, Luyang; Kong, Lin; Wang, Dong; Yang, Hongbo

    2018-02-01

    Studied the impact of flywheel micro vibration on a high resolution optical satellite that space-borne integrated. By testing the flywheel micro vibration with six-component test bench, the flywheel disturbance data is acquired. The finite element model of the satellite was established and the unit force/torque were applied at the flywheel mounting position to obtain the micro vibration data of the camera. Integrated analysis of the data of the two parts showed that the influence of flywheel micro vibration on the camera is mainly concentrated around 60-80 Hz and 170-230 Hz, the largest angular displacement of the secondary mirror along the optical axis direction is 0.04″ and the maximum angular displacement vertical to optical axis is 0.032″. After the design and installation of vibration isolator, the maximum angular displacement of the secondary mirror is 0.011″, the decay rate of root mean square value of the angular displacement is more than 50% and the maximum is 96.78%. The whole satellite was suspended to simulate the boundary condition on orbit; the imaging experiment results show that the image motion caused by the flywheel micro vibrationis less than 0.1 pixel after installing the vibration isolator.

  12. Assessment of Electrical Influence of Multiple Piezoelectric Transducers' Connection on Actual Satellite Vibration Suppression

    Directory of Open Access Journals (Sweden)

    Shigeru Shimose

    2011-01-01

    Full Text Available We conduct comprehensive investigation of a semiactive vibration suppression method using piezoelectric transducers attached to structures. In our system, piezoelectric transducers are connected to an electric circuit composed of the diodes, an inductance, and a selective switch. Our method (SSDI makes better use of counterelectromotive force to suppress the vibration, instead of simple dissipation of vibration energy. We use an actual artificial satellite to verify their high performance compared to conventional semi-active methods. As a consequence, we demonstrate that our semi-active switching method can suppress the vibration of the real artificial satellite to as much as 50% amplitude reduction. In our experiment, we reveal that the suppression performance depends on how multiple piezoelectric transducers are connected, namely, their series or parallel connection. We draw two major conclusions from theoretical analysis and experiment, for constructing effective semi-active controller using piezoelectric transducers. This paper clearly proves that the performance of the method is the connection (series or parallel of multiple piezoelectric transducers and the their resistances dependent on frequency.

  13. Vibration isolation/suppression: research experience for undergraduates in mechatronics and smart structures

    Science.gov (United States)

    Fonda, James; Rao, Vittal S.; Sana, Sridhar

    2001-08-01

    This paper provides an account of a student research project conducted under the sponsoring of the National Science Foundation (NSF) program on Research Experience for Undergraduates (REU) in Mechatronics and Smart Strictures in the summer of 2000. The objective of the research is to design and test a stand-alone controller for a vibration isolation/suppression system. The design specification for the control system is to suppress the vibrations induced by the external disturbances by at least fiver times and hence to achieve vibration isolation. Piezo-electric sensors and actuators are utilized for suppression of unwanted vibrations. Various steps such as modeling of the system, controller design, simulation, closed-loop testing using d- Space rapid prototyping system, and analog control implementation are discussed in the paper. Procedures for data collection, the trade-offs carried out in the design, and analog controller implementation issues are also presented in the paper. The performances of various controllers are compared. The experiences of an undergraduate student are summarized in the conclusion of the paper.

  14. Neural adaptive control for vibration suppression in composite fin-tip of aircraft.

    Science.gov (United States)

    Suresh, S; Kannan, N; Sundararajan, N; Saratchandran, P

    2008-06-01

    In this paper, we present a neural adaptive control scheme for active vibration suppression of a composite aircraft fin tip. The mathematical model of a composite aircraft fin tip is derived using the finite element approach. The finite element model is updated experimentally to reflect the natural frequencies and mode shapes very accurately. Piezo-electric actuators and sensors are placed at optimal locations such that the vibration suppression is a maximum. Model-reference direct adaptive neural network control scheme is proposed to force the vibration level within the minimum acceptable limit. In this scheme, Gaussian neural network with linear filters is used to approximate the inverse dynamics of the system and the parameters of the neural controller are estimated using Lyapunov based update law. In order to reduce the computational burden, which is critical for real-time applications, the number of hidden neurons is also estimated in the proposed scheme. The global asymptotic stability of the overall system is ensured using the principles of Lyapunov approach. Simulation studies are carried-out using sinusoidal force functions of varying frequency. Experimental results show that the proposed neural adaptive control scheme is capable of providing significant vibration suppression in the multiple bending modes of interest. The performance of the proposed scheme is better than the H(infinity) control scheme.

  15. Dynamic modeling and adaptive vibration suppression of a high-speed macro-micro manipulator

    Science.gov (United States)

    Yang, Yi-ling; Wei, Yan-ding; Lou, Jun-qiang; Fu, Lei; Fang, Sheng; Chen, Te-huan

    2018-05-01

    This paper presents a dynamic modeling and microscopic vibration suppression for a flexible macro-micro manipulator dedicated to high-speed operation. The manipulator system mainly consists of a macro motion stage and a flexible micromanipulator bonded with one macro-fiber-composite actuator. Based on Hamilton's principle and the Bouc-Wen hysteresis equation, the nonlinear dynamic model is obtained. Then, a hybrid control scheme is proposed to simultaneously suppress the elastic vibration during and after the motor motion. In particular, the hybrid control strategy is composed of a trajectory planning approach and an adaptive variable structure control. Moreover, two optimization indices regarding the comprehensive torques and synthesized vibrations are designed, and the optimal trajectories are acquired using a genetic algorithm. Furthermore, a nonlinear fuzzy regulator is used to adjust the switching gain in the variable structure control. Thus, a fuzzy variable structure control with nonlinear adaptive control law is achieved. A series of experiments are performed to verify the effectiveness and feasibility of the established system model and hybrid control strategy. The excited vibration during the motor motion and the residual vibration after the motor motion are decreased. Meanwhile, the settling time is shortened. Both the manipulation stability and operation efficiency of the manipulator are improved by the proposed hybrid strategy.

  16. Vibration Suppression for Improving the Estimation of Kinematic Parameters on Industrial Robots

    Directory of Open Access Journals (Sweden)

    David Alejandro Elvira-Ortiz

    2016-01-01

    Full Text Available Vibration is a phenomenon that is present on every industrial system such as CNC machines and industrial robots. Moreover, sensors used to estimate angular position of a joint in an industrial robot are severely affected by vibrations and lead to wrong estimations. This paper proposes a methodology for improving the estimation of kinematic parameters on industrial robots through a proper suppression of the vibration components present on signals acquired from two primary sensors: accelerometer and gyroscope. A Kalman filter is responsible for the filtering of spurious vibration. Additionally, a sensor fusion technique is used to merge information from both sensors and improve the results obtained using each sensor separately. The methodology is implemented in a proprietary hardware signal processor and tested in an ABB IRB 140 industrial robot, first by analyzing the motion profile of only one joint and then by estimating the path tracking of two welding tasks: one rectangular and another one circular. Results from this work prove that the sensor fusion technique accompanied by proper suppression of vibrations delivers better estimation than other proposed techniques.

  17. Vibration Suppression of a Helicopter Fuselage by Pendulum Absorbers : Rigid-Body Blades with Aerodynamic Excitation Force

    Science.gov (United States)

    Nagasaka, Imao; Ishida, Yukio; Koyama, Takayuki; Fujimatsu, Naoki

    Currently, some kinds of helicopters use pendulum absorbers in order to reduce vibrations. Present pendulum absorbers are designed based on the antiresonance concept used in the linear theory. However, since the vibration amplitudes of the pendulum are not small, it is considered that the nonlinearity has influence on the vibration characteristics. Therefore, the best suppression cannot be attained by using the linear theory. In a helicopter, periodic forces act on the blades due to the influences of the air thrust. These periodic forces act on the blades with the frequency which is the integer multiple of the rotational speed of the rotor. Our previous study proposed a 2-degree-of-freedom (2DOF) model composed of a rotor blade and a pendulum absorber. The blade was considered as a rigid body and it was excited by giving a sinusoidal deflection at its end. The present paper proposes a 3DOF model that is more similar to the real helicopter, since the freedom of the fuselage is added and the periodic forces are applied to the blade by aerodynamic force. The vibration is analyzed considering the nonlinear characteristics. The resonance curves of rotor blades with pendulum absorbers are obtained analytically and experimentally. It is clarified that the most efficient condition is obtained when the natural frequency of the pendulum is a little bit different from the frequency of the external force. Various unique nonlinear characteristics, such as bifurcations, are also shown.

  18. Cause elucidation of sodium leakage incident at `Monju` reactor. Vibration of thermometer due to fluid force

    Energy Technology Data Exchange (ETDEWEB)

    Iwata, Koji; Wada, Yusaku; Morishita, Masaki; Yamaguchi, Akira; Ichimiya, Masakazu [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1997-01-01

    This is a report of summarized results of investigation and analysis on fracture of thermometer which is direct reason of sodium leakage incident at the second main cooling system of fast breeder reactor `Monju`. Various surveys such as on various damage factors, on flowing power vibrational features containing flowing power vibrational test of thermometer, on evaluation of high cycle fatigue due to flowing power vibration and details on propagation of and fracture due to fatigue crack, on why only said thermometer damaged, and so forth were executed. As results of these examinations, a decision was arrived that high cycle fatigue due to vibration formed by fluid force (fluid force vibration) was a direct cause of the thermometer damage. (G.K.)

  19. Lumped mass model of a 1D metastructure for vibration suppression with no additional mass

    Science.gov (United States)

    Reichl, Katherine K.; Inman, Daniel J.

    2017-09-01

    The article examines the effectiveness of metastructures for vibration suppression from a weight standpoint. Metastructures, a metamaterial inspired concept, are structures with distributed vibration absorbers. In automotive and aerospace industries, it is critical to have low levels of vibrations while also using lightweight materials. Previous work has shown that metastructures are effective at mitigating vibrations, but do not consider the effects of mass. This work takes mass into consideration by comparing a structure with vibration absorbers to a structure of equal mass with no absorbers. These structures are modeled as one-dimensional lumped mass models, chosen for simplicity. Results compare both the steady-state and the transient responses. As a quantitative performance measure, the H2 norm, which is related to the area under the frequency response function, is calculated and compared for both the metastructure and the baseline structure. These results show that it is possible to obtain a favorable vibration response without adding additional mass to the structure. Additionally, the performance measure is utilized to optimize the geometry of the structure, determine the optimal ratio of mass in the absorber to mass of the host structure, and determine the frequencies of the absorbers. The dynamic response of this model is verified using a finite element analysis.

  20. Consideration of Spillover Effect in Active Vibration Suppression of a Smart Composite Plate Using Piezoelectric Elements

    Directory of Open Access Journals (Sweden)

    Eman Eshraqi

    Full Text Available Abstract In this paper, the problem of vibration suppression of a smart composite plate with bonded piezoelectric patches is considered. A higher order plate model is used for finite element modeling of the plate and the PID controller is used to generate control voltage command to the piezo actuators from the piezo sensors data. Derived formulation and the control algorithm is implemented in a finite element (FE code and the FE modeling results are verified using available results of previous studies. The effect of control gain on the vibration suppression characteristics is studied. Furthermore, since FE modeling reduces the order of the real problem, the problem of un-modeled residual modes on the so-called spillover effect is investigated.

  1. Research on vibration suppression of a mistuned blisk by a piezoelectric network

    Directory of Open Access Journals (Sweden)

    Jiuzhou LIU

    2018-02-01

    Full Text Available The work aims to provide a further investigation of the dynamic characteristics of an integral bladed disk (also called ‘blisk’ with a Parallel Piezoelectric Network (PPN. The PPN is constructed by parallelly interconnecting the piezoelectric patches distributed in the blisk. Two kinds of PPN are considered, namely mono-periodic PPN and bi-periodic PPN. The former has a piezoelectric patch in each sector, and the later has one patch every few sectors. The vibration suppression performance of both kinds of PPN has been studied through modal analysis, forced response analysis, and statistical analysis. The research results turn out that the PPN will only affect mechanical frequencies near the electrical frequency clusters slightly, and the bi-periodic PPN will make the nodal diameter spectrum of the modes more complex, but the amplitude corresponding to the new nodal diameter component is much smaller than that of the nodal diameter component corresponding to the mono-periodic system. The mechanical coupling between the blades and the disk plays an important role in the damping effect of the PPN, and it should be paid attention to in applications. The mono-periodic PPN can effectively suppress the amplitude magnification of the forced response induced by the mistuning of the blisk; meanwhile, it can mitigate the vibration localization of the mistuned electromechanical system. If piezoelectric patches are set only in part of the sectors, the bi-periodic PPN still has a vibration suppression ability, but the effect is related to the number and spatial distribution of the piezoelectric patches. Keywords: Amplitude magnification, Bi-periodic, Blisk, Mistuning, Mono-periodic, Parallel piezoelectric network, Statistical analysis, Vibration suppression

  2. Suppression of vortex-induced vibration of a circular cylinder with fixed and rotating control cylinders.

    OpenAIRE

    Mariana Silva Ortega

    2015-01-01

    The offshore oil industry is engaged in the development of new floating platforms, such as Spar, semi-submersible, tension-leg, FPSO and monocolumn for the exploration of deep and ultra-deep waters. Some of these floating systems have circular cross sections (or cross sections of other bluff geometries) being susceptible to vortex-induced vibrations (VIV). Vortex shedding behind a bluff body can be altered, suppressed or controlled over a limited range of Reynolds numbers. Various flow-contro...

  3. Numerical study of self-adaptive vibration suppression for flexible structure using interior inlay viscous fluid unit method

    Science.gov (United States)

    Zhang, Xiongwen; Li, Jun; Xu, Hui; Li, Guojun

    2006-11-01

    This paper investigates the usage of an interior inlay viscous fluid unit as a new vibration suppression method for flexible structures via numerical simulations. The first and second modes of vibration for a beam have been calculated using the commercial computational fluid dynamic package Fluent6.1, together with the liquid surface distribution and the fluid force. The calculated results show that the inlay fluid unit has suppressive effects on flexible structures. The liquid converges self-adaptively to locations of larger vibrations. The fluid force varies with the beam vibration at a phase difference of more than 180°. Thus the fluid force suppresses the beam vibration at most of the time.

  4. Vibration suppression in cutting tools using collocated piezoelectric sensors/actuators with an adaptive control algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Radecki, Peter P [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory; Bement, Matthew T [Los Alamos National Laboratory

    2008-01-01

    The machining process is very important in many engineering applications. In high precision machining, surface finish is strongly correlated with vibrations and the dynamic interactions between the part and the cutting tool. Parameters affecting these vibrations and dynamic interactions, such as spindle speed, cut depth, feed rate, and the part's material properties can vary in real-time, resulting in unexpected or undesirable effects on the surface finish of the machining product. The focus of this research is the development of an improved machining process through the use of active vibration damping. The tool holder employs a high bandwidth piezoelectric actuator with an adaptive positive position feedback control algorithm for vibration and chatter suppression. In addition, instead of using external sensors, the proposed approach investigates the use of a collocated piezoelectric sensor for measuring the dynamic responses from machining processes. The performance of this method is evaluated by comparing the surface finishes obtained with active vibration control versus baseline uncontrolled cuts. Considerable improvement in surface finish (up to 50%) was observed for applications in modern day machining.

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

    Science.gov (United States)

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

    2015-01-01

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

  6. Modal interaction and vibration suppression in industrial turbines using adjustable journal bearings

    Science.gov (United States)

    Chasalevris, Athanasios; Dohnal, Fadi

    2016-09-01

    The vibration suppression by deliberately introducing a parametric excitation in the fluid-film bearings is investigated for an industrial turbine rotor system. A journal bearing with variable adjustable geometry is operated in such a way that the effective stiffness and damping properties vary periodically in time. The proposed bearing is designed for having the ability of changing the bearing fluid film thickness in a semi-active manner. Such an adjustment of the journal bearing properties introduces in the system a time-periodic variation of the effective stiffness and damping properties of the fluid-film. If the time-periodicity is tuned properly to match a parametric anti-resonance, vibration suppression is achieved in the overall system. The paper presents the principle of operation of the recently developed bearings. The simulation of an industrial turbine rotor-bearing shaft line at induced parametric excitation motivates the further development and application of such bearings since the vibration amplitudes are considerably decreased in critical speeds.

  7. Space robots with flexible appendages: Dynamic modeling, coupling measurement, and vibration suppression

    Science.gov (United States)

    Meng, Deshan; Wang, Xueqian; Xu, Wenfu; Liang, Bin

    2017-05-01

    For a space robot with flexible appendages, vibrations of flexible structure can be easily excited during both orbit and/or attitude maneuvers of the base and the operation of the manipulators. Hence, the pose (position and attitude) of the manipulator's end-effector will greatly deviate from the desired values, and furthermore, the motion of the manipulator will trigger and exacerbate vibrations of flexible appendages. Given lack of the atmospheric damping in orbit, the vibrations will last for quite a while and cause the on-orbital tasks to fail. We derived the rigid-flexible coupling dynamics of a space robot system with flexible appendages and established a coupling model between the flexible base and the space manipulator. A specific index was defined to measure the coupling degree between the flexible motion of the appendages and the rigid motion of the end-effector. Then, we analyzed the dynamic coupling for different conditions, such as modal displacements, joint angles (manipulator configuration), and mass properties. Moreover, the coupling map was adopted and drawn to represent the coupling motion. Based on this map, a trajectory planning method was addressed to suppress structure vibration. Finally, simulation studies of typical cases were performed, which verified the proposed models and method. This work provides a theoretic basis for the system design, performance evaluation, trajectory planning, and control of such space robots.

  8. Motion Control of Industrial Robot by Considering Vibration Suppression and Fast Path Tracking

    Science.gov (United States)

    Kumagai, Satoru; Miyazaki, Toshimasa; Ohishi, Kiyoshi

    This paper proposes a new motion control strategy for industrial robots. It is important to achieve rapid and accurate control of the motion of industrial robots. However, industrial robots often have vibration which is caused by the resonant frequency and nonlinear interference force from various joints of the robot. In this case, the notch filtering method for generating a reference is useful for suppressing the resonant phenomenon. However, the path tracking error of the robot motion increases because phase delay becomes large by using the notch filter. In order to overcome these problems, this paper proposes a zero-phase notch filter without phase delay for fast path tracking. Moreover, this paper proposes a fast position control method based on D-PD control with dynamic feed-forward compensation. Using these proposed strategies, this paper achieves fast and accurate robot motion control without vibration and overshoot.

  9. Fuzzy Model-based Pitch Stabilization and Wing Vibration Suppression of Flexible Wing Aircraft.

    Science.gov (United States)

    Ayoubi, Mohammad A.; Swei, Sean Shan-Min; Nguyen, Nhan T.

    2014-01-01

    This paper presents a fuzzy nonlinear controller to regulate the longitudinal dynamics of an aircraft and suppress the bending and torsional vibrations of its flexible wings. The fuzzy controller utilizes full-state feedback with input constraint. First, the Takagi-Sugeno fuzzy linear model is developed which approximates the coupled aeroelastic aircraft model. Then, based on the fuzzy linear model, a fuzzy controller is developed to utilize a full-state feedback and stabilize the system while it satisfies the control input constraint. Linear matrix inequality (LMI) techniques are employed to solve the fuzzy control problem. Finally, the performance of the proposed controller is demonstrated on the NASA Generic Transport Model (GTM).

  10. Dynamics and vibration suppression of space structures with control moment gyroscopes

    Science.gov (United States)

    Hu, Quan; Jia, Yinghong; Xu, Shijie

    2014-03-01

    This paper presents a new and effective approach for vibration suppression of large space structures. Collocated pairs of control moment gyroscope (CMG) and angular rate sensor are adopted as actuators/sensors. The equations of motion of a flexible structure with a set of arbitrarily distributed CMGs are developed. The detailed dynamics of the CMGs and their interactions between the flexibilities of the structure are incorporated in the formulation. Then, the equations of motion are linearized to describe the small-scale motion of the system. The optimal placement problem of the actuators/sensors on the flexible structures is solved from the perspective of system controllability and observability. The controller for the vibration suppression is synthesized using the angular rates of the locations where the CMGs are mounted and the gimbal angles of the CMGs. The stability of the controller is proved by the Lyapunov theorem. Numerical examples of a beam structure and a plate structure validate the efficacy of the proposed method.

  11. Generalized-Disturbance Rejection Control for Vibration Suppression of Piezoelectric Laminated Flexible Structures

    Directory of Open Access Journals (Sweden)

    Xiao-Yu Zhang

    2018-01-01

    Full Text Available In the framework of disturbance rejection (DR control, the paper proposes a generalized-disturbance rejection (GDR control with proportional-integral (PI observer for vibration suppression of smart structures under any unknown continuous disturbances. In the proposed GDR-PI control, a refined state space model is first constructed, and a generalized disturbance including the disturbance influence matrices, unknown physical disturbances, and state variables is defined. In the closed loop of GDR-PI control, physical disturbances can be counteracted indirectly by feeding back estimated generalized disturbances. By this means, the GDR-PI control remedies most of the defects in conventional DR control and has excellent performances especially in the following situations: (i the disturbances are completely unknown; (ii the number of sensor signals is less than the number of disturbances; (iii the unknown disturbances vary fast. Finally, the GDR-PI control is validated and compared with H∞ state feedback control and conventional DR control available in the literature for vibration suppression of smart beams.

  12. Optimal modal vibration suppression of a fluid-conveying pipe with a divergent mode

    Science.gov (United States)

    Lin, Yih-Hwang; Huang, Rui-Cheng; Chu, Chih-Liang

    2004-04-01

    This study deals with the divergence characteristics of pipes conveying fluid and explores the applicability of active modal vibration control for suppressing the associated excessive structural vibration. The Timoshenko beam theory is used to establish the system equation of motion. The analysis is based on the finite element method. Active modal control technique is developed in this work for pipes conveying fluid with a flow speed exceeding the critical one. Optimal independent modal space control (IMSC) is applied for the design. For pipes conveying super-critical flow speed, as considered in this work, the system's eigenvalues have both real and complex roots, which must be dealt with in a different way from what has been established in the literature. A weighting matrix with finite weights is applied for the control of complex modes, whereas a weighting matrix with an infinite weight is used for controlling the divergent mode, with roots being real. From this study, it is demonstrated that the control approach proposed in this work can ensure closed loop stability. The mode switching scheme of directing control to the mode which has higher modal response is found to be beneficial in reducing the overall structural vibration of the fluid-conveying pipe.

  13. Nonlinear Vibration Characteristics of a Flexible Blade with Friction Damping due to Tip-Rub

    Directory of Open Access Journals (Sweden)

    Dengqing Cao

    2011-01-01

    Full Text Available An approximate approach is proposed in this paper for analyzing the two-dimensional friction contact problem so as to compute the dynamic response of a structure constrained by friction interfaces due to tip-rub. The dynamical equation of motion for a rotational cantilever blade in a centrifugal force field is established. Flow-induced distributed periodic forces and the internal material damping in the blade are accounted for in the governing equation of motion. The Galerkin method is employed to obtain a three-degree-of-freedom oscillator with friction damping due to tip-rub. The combined motion of impact and friction due to tip-rub produced a piecewise linear vibration which is actually nonlinear. Thus, a complete vibration cycle is divided into successive intervals. The system possesses linear vibration characteristic during each of these intervals, which can be determined using analytical solution forms. Numerical simulation shows that the parameters such as gap of the tip and the rotational speed of the blades have significant effects on the dynamical responses of the system. Finally, the nonlinear vibration characteristics of the blade are investigated in terms of the Poincare graph, and the frequency spectrum of the responses and the amplitude-frequency curves.

  14. A New Framework For Helicopter Vibration Suppression; Time-Periodic System Identification and Controller Design

    Science.gov (United States)

    Ulker, Fatma Demet

    In forward flight, helicopter rotor blades function within a highly complex aerodynamic environment that includes both near-blade and far-blade aerodynamic phenomena. These aerodynamic phenomena cause fluctuating aerodynamic loads on the rotor blades. These loads when coupled with the dynamic characteristics and elastic motion of the blade create excessive amount of vibration. These vibrations degrade helicopter performance, passenger comfort and contributes to high cost maintenance problems. In an effort to suppress helicopter vibration, recent studies have developed active control strategies using active pitch links, flaps, twist actuation and higher harmonic control of the swash plate. In active helicopter vibration control, designing a controller in a computationally efficient way requires accurate reduced-order models of complex helicopter aeroelasticity. In previous studies, controllers were designed using aeroelastic models that were obtained by coupling independently reduced aerodynamic and structural dynamic models. Unfortunately, these controllers could not satisfy stability and performance criteria when implemented in high-fidelity computer simulations or real-time experiments. In this thesis, we present a novel approach that provides accurate time-periodic reduced-order models and time-periodic H2 and H infinity controllers that satisfy the stability and performance criteria. Computational efficiency and the necessity of using the approach were validated by implementing an actively controlled flap strategy. In this proposed approach, the reduced-order models were directly identified from high-fidelity coupled aeroelastic analysis by using the time-periodic subspace identification method. Time-periodic H2 and Hinfinity controllers that update the control actuation at every time step were designed. The control synthesis problem was solved using Linear Matrix Inequality and periodic Riccati Equation based formulations, for which an in-house periodic

  15. An experimental investigation of composite floor vibration due to human activities. A case study

    Directory of Open Access Journals (Sweden)

    Yasser G. Mohamed Fahmy

    2012-12-01

    Full Text Available Composite steel floor decks are used in a large variety of constructions with long spans, such as administration and commercial buildings, hotels and bridges. Due to decreased floor mass and longer span lengths, floor vibrations have become an area of concern. Floor decks with low frequencies may be in resonance with the vibrations due to human activities and the resulting acceleration may exceed human comfort levels. The design of slender floor structures, with steel or composite cross sections, is often limited by the serviceability criteria such as deflection limits and vibration behavior, rather than the strength criteria. Control of deflections under AISC specifications requirement is not enough to satisfy the serviceability requirements of the floor systems for vibration. In addition, vibration analysis procedures introduced by AISC design Guide No. 11 are based on regularly-shaped structures and simple boundary conditions. In this paper, a case study for full scale testing of a composite floor system proposed for a tower at Kuwait state that was tested prior to construction. The heel-drop and walking tests are performed on floor systems with and without raised floor respectively. Since heel-drop and walking test results would vary in light of person performance, both tests are carried out three or four times to reduce uncertainty. The fundamental frequencies and damping ratio of the floor system are measured. Comparison of the experimental results with results based on the AISC hand calculations shows that there is no significant difference; therefore the results based on AISC are generally acceptable.

  16. A piezoelectric brace for passive suppression of structural vibration and energy harvesting

    Science.gov (United States)

    Yang, Chuang-Sheng Walter; Lai, Yong-An; Kim, Jin-Yeon

    2017-08-01

    Power outage after an earthquake would cause an additional chaos to the existing aftermath, greatly aggravating the situation if the outage lasts for an extended period. This research aims at developing an innovative piezoelectric brace, which provides both passive energy-dissipating and energy-harvesting capabilities—a passive suppression of structural vibrations and conversion of vibration energy into reusable electricity. The piezoelectric brace has compression modules that exert compressive loads on the piezoelectric material regardless if the brace is in compression or in tension. The compression module consists of a piezoelectric stack and rubber pads. The rubber pads are used to limit the maximum strain in the piezoelectric material below the allowable operational strain. The electro-mechanical equations of motion are derived for a 1-story and a 3-story frame model with the piezoelectric braces. To evaluate the structural behavior and the energy harvesting performance, numerical simulations are executed for the two model buildings (in downtown Los Angeles) that are equipped with the piezoelectric braces. The effects of design parameters including the geometry of the piezoelectric stack and rubber pads and the electric resistance in the electro-mechanical conversion circuit on the performance are investigated. The numerical results indicate that the piezoelectric braces passively dissipate energy through inclined oval-shaped hysteretic loops. The harvested energy is up to approximately 40% of the input energy. The structural displacements are significantly reduced, as compared to the original frames without the piezoelectric braces. Finally, a design procedure for a frame with the proposed passive piezoelectric braces is also presented.

  17. Backstepping boundary control: an application to the suppression of flexible beam vibration

    Science.gov (United States)

    Boonkumkrong, Nipon; Asadamongkon, Pichai; Chinvorarat, Sinchai

    2018-01-01

    This paper presents a backstepping boundary control for vibration suppression of flexible beam. The applications are such as industrial robotic arms, space structures, etc. Most slender beams can be modelled using a shear beam. The shear beam is more complex than the conventional Euler-Bernoulli beam in that a shear deformation is additionally taken into account. At present, the application of this method in industry is rather limited, because the application of controllers to the beam is difficult. In this research, we use the shear beam with moving base as a model. The beam is cantilever type. This design method allows us to deal directly with the beam’s partial differential equations (PDEs) without resorting to approximations. An observer is used to estimate the deflections along the beam. Gain kernel of the system is calculated and then used in the control law design. The control setup is anti-collocation, i.e. a sensor is placed at the beam tip and an actuator is placed at the beam moving base. Finite difference equations are used to solve the PDEs and the partial integro-differential equations (PIDEs). Control parameters are varied to see their influences that affect the control performance. The results of the control are presented via computer simulation to verify that the control scheme is effective.

  18. Vibrational excitation in molecule--surface collisions due to temporary negative molecular ion formation

    International Nuclear Information System (INIS)

    Gadzuk, J.W.

    1983-01-01

    Inelastic electron scattering from gaseous and physisorbed diatomic molecules results in greatly enhanced vibrational overtone excitation if the incident electron has the appropriate energy to form a shape-resonance-induced temporary negative molecular ion. It is proposed here that due to the image potential lowering of the electron affinity level of a diatomic molecule in interaction with a metal surface, somewhere outside the surface an incident molecule would find its affinity level degenerate with or lower than the substrate Fermi level at which point a substrate electron could hop onto the molecule, in analogy with gas phase harpooning processes. A negative molecular ion is thus formed which remains until the molecular ion reflects from the surface and the affinity level rises above the Fermi level, thus permitting reverse electron hopping back into the metal. The lifetime of the molecular ion can be controlled by varying both the kinetic energy of the incident molecule and also the substrate work function. In analogy with the electron scattering events, greatly enhanced vibrational excitation of overtones is expected in the molecules of the scattered beam. Induced fluorescence probing of the vibrational state distribution should then yield fundamental information pertaining to the dynamics of charge transfer reactions and nonadiabatic effects in molecule--surface interactions. A theory of this phenomenon is here presented together with the numerical consequences for a model system designed to simulate N 2 or NO scattering from standard surface science metal surfaces

  19. Changes in EMG activity in the upper trapezius muscle due to local vibration exposure

    NARCIS (Netherlands)

    Astrom, Charlotte; Lindkvist, Markus; Burstrom, Lage; Sundelin, Gunnevi; Karlsson, J. Stefan

    Exposure to vibration is suggested as a risk factor for developing neck and shoulder disorders in working life. Mechanical vibration applied to a muscle belly or a tendon can elicit a reflex muscle contraction, also called tonic vibration reflex, but the mechanisms behind how vibration could cause

  20. Vortex-induced vibration (VIV) effects of a drilling riser due to vessel motion

    Science.gov (United States)

    Joseph, R. S.; Wang, J.; Ong, M. C.; Jakobsen, J. B.

    2017-12-01

    A marine riser undergoes oscillatory motion in water due to the vessel motions, known as global dynamic response. This to-and-fro motion of the riser will generate an equivalent flow that can cause Vortex-Induced Vibrations (VIVs), even in the absence of the ocean current. In the present work, full-scale measurement data of a drilling riser operating in the Gulf of Mexico are analysed. The VIV occurrences for the riser are identified from the data and the possible excitation sources are discussed. The oscillatory flow due to vessel motion is compared with the ocean current and its possibility to excite VIV is analysed. The full-scale data analysis provides an insight into the vessel motion-induced VIV of marine risers in the actual field environment.

  1. Suppression of the Rayleigh-Taylor instability due to self-radiation in a multiablation target

    International Nuclear Information System (INIS)

    Fujioka, Shinsuke; Sunahara, Atsushi; Nishihara, Katsunobu; Johzaki, Tomoyuki; Shiraga, Hiroyuki; Shigemori, Keisuke; Nakai, Mitsuo; Ikegawa, Tadashi; Murakami, Masakatsu; Nagai, Keiji; Norimatsu, Takayoshi; Azechi, Hiroshi; Yamanaka, Tatsuhiko; Ohnishi, Naofumi

    2004-01-01

    A scheme to suppress the Rayleigh-Taylor instability has been investigated for a direct-drive inertial fusion target. In a high-Z doped-plastic target, two ablation surfaces are formed separately--one driven by thermal radiation and the other driven by electron conduction. The growth of the Rayleigh-Taylor instability is significantly suppressed on the radiation-driven ablation surface inside the target due to the large ablation velocity and long density scale length. A significant reduction of the growth rate was observed in simulations and experiments using a brominated plastic target. A new direct-drive pellet was designed using this scheme

  2. Experimental study of heat transfer enhancement due to the surface vibrations in a flexible double pipe heat exchanger

    Science.gov (United States)

    Hosseinian, A.; Meghdadi Isfahani, A. H.

    2017-11-01

    In this study, the heat transfer enhancement due to the surface vibration for a double pipe heat exchanger, made of PVDF, is investigated. In order to create forced vibrations (3-9 m/s2, 100 Hz) on the outer surface of the heat exchanger electro-dynamic vibrators are used. Experiments were performed at inner Reynolds numbers ranging from 2533 to 9960. The effects of volume flow rate and temperature on heat transfer performance are evaluated. Results demonstrated that heat transfer coefficient increases by increasing vibration level and mass flow rate. The most increase in heat transfer coefficient is 97% which is obtained for the highest vibration level (9 m/s2) in the experiment range.

  3. Experimental study of heat transfer enhancement due to the surface vibrations in a flexible double pipe heat exchanger

    Science.gov (United States)

    Hosseinian, A.; Meghdadi Isfahani, A. H.

    2018-04-01

    In this study, the heat transfer enhancement due to the surface vibration for a double pipe heat exchanger, made of PVDF, is investigated. In order to create forced vibrations (3-9 m/s2, 100 Hz) on the outer surface of the heat exchanger electro-dynamic vibrators are used. Experiments were performed at inner Reynolds numbers ranging from 2533 to 9960. The effects of volume flow rate and temperature on heat transfer performance are evaluated. Results demonstrated that heat transfer coefficient increases by increasing vibration level and mass flow rate. The most increase in heat transfer coefficient is 97% which is obtained for the highest vibration level (9 m/s2) in the experiment range.

  4. Analysis of the Suppression Device as Vortex Induced Vibration (VIV Reducer on Free Span using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Dwi Priyanta

    2016-12-01

    Full Text Available Subsea pipeline is a transportation infrastructure of oil and gas as an alternative for ship tanker. The uneven topography surface of the sea floor resulting the pipe undergoes free span. The free span is a condition endured by the pipe where the pipe position has  distance or gap with the seabed supported by two pivot. The free span is at risk of experiencing a vibration caused by the presence of dynamic load that is current and the wave. The vibration that occurs is the impact of the presence of the phenomenon of Vortex Induced Vibration (VIV. The Phenomenon Of VIV occur on a cylindrical component caused by ocean currents, causing the occurrence of vibration by the movement of fluid on the pipe so that it raises the vortex at the rear of the direction of oncoming flow. One way to dampen or reduce the impact of VIV is by adding suppresion device. VIV suppression device is a tool that is installed on the pipeline on offshore piping installationcthat serves to dampen or reduce the impact of VIV. One of the simulations used to know the characteristics of a fluid is to use (CFD Computational Fluid Dynamic. With the addition of suppression device can add the rest of the operating time on a free span of affected VIV, on the condition of free span critical exposed VIV (Vortex Induced Vibration value has a life time on plain pipe 44.21 years, on pipe with 53.09 years and Fairing on the pipe with the Helical strike 52.95 year.

  5. Size-dependent buckling and vibration behaviors of piezoelectric nanostructures due to flexoelectricity

    International Nuclear Information System (INIS)

    Liang, Xu; Hu, Shuling; Shen, Shengping

    2015-01-01

    The symmetry breaking of inversion in solid crystals will induce electric polarization in all solid crystals, which is well known as flexoelectricity. At the nanometer scale, due to the large ratio of surface to volume, piezoelectric structures always exhibit distinct mechanical and electrical behaviors compared with their bulk counterparts. In the current work, the effects of surface and flexoelectricity on the buckling and vibration of piezoelectric nanowires is investigated based on a continuum framework and the Euler–Bernoulli beam hypothesis. Analytical solutions of the electric field in the piezoelectric nanobeam subjected to electrical and mechanical loads are obtained with the surface, flexoelectric and nonlocal electric effects. Numeric simulations demonstrate that the Young’s modulus and bending rigidity of PZT and BaTiO 3 (BT) nanowires are enhanced by flexoelectricity. In addition, the critical buckling voltage is calculated with consideration of the effects of surface and flexoelectricity, and it is found that the effects of surface piezoelectricity, flexoelectricity and residual surface stress play significant roles in determining the critical buckling voltage. Results obtained for the first resonance frequency also indicate that the effects of surface and flexoelectricity are more significant at a narrow range of beam thickness. The first resonance frequency of PZT and BT nanowires is also influenced by the residual surface stress and external applied voltage. The current work is expected to provide a fundamental study on the buckling and vibration behaviors of piezoelectric nanobeams, and it might also be helpful in devising piezoelectric nanowire-based nanoelectronics. (paper)

  6. Suppression of spurious vibration of cantilever in atomic force microscopy by enhancement of bending rigidity of cantilever chip substrate.

    Science.gov (United States)

    Tsuji, Toshihiro; Kobari, Kentaro; Ide, Seishiro; Yamanaka, Kazushi

    2007-10-01

    To improve the precision of dynamic atomic force microscopy (AFM) using cantilever vibration spectra, a simple but effective method for suppressing spurious response (SR) was developed. The dominant origin of SR was identified to be the bending vibration of the cantilever substrate, by the analysis of the frequency of SR. Although a rigid cover pressing the whole surface of the substrate suppressed SR, the utility was insufficient. Then, a method of enhancing the bending rigidity of the substrate by gluing a rigid plate (clamping plate, CP) to the substrate was developed. This chip can be used with an ordinary cantilever holder, so that the reproducibility of SR suppression when attaching and detaching the cantilever chip to the holder was improved. To verify its utility, the evaluation of a microdevice electrode was performed by ultrasonic atomic force microscopy. The delamination at a submicron depth was visualized and the detailed variation of the delamination was evaluated for the first time using clear resonance spectra. The CP method will particularly contribute to improving dynamic-mode AFM, in which resonance spectra with a low quality factor are used, such as noncontact mode AFM in liquid or contact resonance mode AFM. The effect of the CP can be achieved by fabricating a substrate with a thick plate beforehand.

  7. VIBRATIONS DUES AU PASSAGE D'UN TRAMWAY : MESURES EXPÉRIMENTALES ET SIMULATIONS NUMERIQUES

    OpenAIRE

    Maldonado, Marc

    2008-01-01

    Tram traffic can produce vibrations propagating in soil leading to annoyance for people living or working in neighbouring buildings. Thus vibration is an important parameter to be considered when planning new lines. Within this topic, the aim of this work is twofold. The first objective is to present experimental investigations for the analysis of tram induced vibrations, taking into account various parameters : tram speed, tram type (two manufacturers), track type (standard or floating slab ...

  8. Approach for a smart device for active vibration suppression as an add-on for robot-based systems

    Energy Technology Data Exchange (ETDEWEB)

    Perner, Marcus; Krombholz, Christian; Monner, Hans Peter [Institute of Composite Structures and Adaptive Systems, Braunschweig (Germany)

    2014-11-15

    Robot-based systems are defined by the capabilities of links and joints that form the robot arm, the control including drive engines and the end effector. In particular, articulated robots have a serial structure. They have to carry the drive engine of each ongoing axis, which results in higher susceptibility to vibration. To compensate weak precision the German Aerospace Center (DLR) integrates a quality improving sensor system on the robot platform. A vibration monitoring system detects vibrations that affect the precision during motion tasks. Currently, higher precision is achieved by slowing down the speed in production. Therefore, a compromise is given between speed and precision. To push the limits for these two conflicting process properties, we propose an approach for an additional smart device to decouple the process-sensitive unit from disturbances arising through motion of the kinematic structure. The smart device enables active vibration suppression by use of a piezo-based actuator with a lever mechanism connected to a motion platform. The lever mechanism provides the required force and displacement adaption. The platform provides mounting and steering of the process-sensitive components. First, an insight into the automation task is given within this paper. Secondly, the system design is illustrated. Based on simulation results the characteristic of the proposed mechanism is shown. Besides the mechanical properties like stiffness and lever amplification, dynamical issues like the smallest eigenfrequency are discussed. To verify simulation results initial measurements are presented and discussed. The paper sums up with the discussion of an implementation of a closed-loop control system to achieve vibration-free and fast motion.

  9. Torsional vibration analysis in turbo-generator shaft due to mal-synchronization fault

    Science.gov (United States)

    Bangunde, Abhishek; Kumar, Tarun; Kumar, Rajeev; Jain, S. C.

    2018-03-01

    A rotor of turbo-generator shafting is many times subjected to torsional vibrations during its lifespan. The reasons behind these vibrations are three-Phase fault, two-phase fault, line to ground fault, faulty-mal synchronization etc. Sometimes these vibrations can cause complete failure of turbo-generator shafting system. To calculate moment variation during these faults on the shafting system vibration analysis is done using Finite Elements Methods to calculate mass and stiffness matrix. The electrical disturbance caused during Mal-synchronization is put on generator section, and corresponding second order equations are solved by using “Duhamel Integral”. From the moment variation plots at four sections critically loaded sections are identified.

  10. Environmental problems associated with blasting in mines: public apprehensions of damage due to blast vibrations - case studies

    Energy Technology Data Exchange (ETDEWEB)

    Padhi, S.N. [DGMS, Bhubaneswar (India)

    1994-12-31

    Blast vibrations may be felt in intensities as small as 1/100 of that required to cause any damage to structures. Therefore, the public response and thus complaints regarding damages are often imaginary. The paper deals with three case studies, involving alleged damage from blasting in surface and underground coal mines where public litigations and agitations resulted due to such apprehensions. The paper is written in simple technical language as the situations warranted that the blast vibration studies should be understood by the general public. 7 tabs.

  11. Non-collocated fuzzy logic and input shaping control strategy for elastic joint manipulator: vibration suppression and time response analysis

    International Nuclear Information System (INIS)

    Rashidifar, Mohammed Amin; Rashidifar, Ali Amin

    2014-01-01

    Conventional model-based control strategies are very complex and difficult to synthesize due to high complexity of the dynamics of robots manipulator considering joint elasticity. This paper presents investigations into the development of hybrid control schemes for trajectory tracking and vibration control of a flexible joint manipulator. To study the effectiveness of the controllers, initially a collocated proportional-derivative (P D)-type Fuzzy Logic Controller (FLC) is developed for tip angular position control of a flexible joint manipulator. This is then extended to incorporate a non-collocated Fuzzy Logic Controller and input shaping scheme for vibration reduction of the flexible joint system. The positive zero-vibration-derivative-derivative (ZVDD) shaper is designed based on the properties of the system. Simulation results of the response of the flexible joint manipulator with the controllers are presented in time and frequency domains. The performances of the hybrid control schemes are examined in terms of input tracking capability, level of vibration reduction and time response specifications. Finally, a comparative assessment of the control techniques is presented and discussed. (Author)

  12. Optimal Placement of Piezoelectric Macro Fiber Composite Patches on Composite Plates for Vibration Suppression

    OpenAIRE

    Padoin, Eduardo; Fonseca, Jun Sergio Ono; Perondi, Eduardo André; Menuzzi, Odair

    2015-01-01

    AbstractThis work presents a new methodology for the parametric optimization of piezoelectric actuators installed in laminated composite structures, with the objective of controlling structural vibrations. Problem formulation is the optimum location of a Macro Fiber Composite (MFC) actuator patch by means the maximization of the controllability index. The control strategy is based on a Linear Quadratic Regulator (LQR) approach. For the structural analysis, the modeling of the interaction betw...

  13. A synergistic method for vibration suppression of an elevator mechatronic system

    Science.gov (United States)

    Knezevic, Bojan Z.; Blanusa, Branko; Marcetic, Darko P.

    2017-10-01

    Modern elevators are complex mechatronic systems which have to satisfy high performance in precision, safety and ride comfort. Each elevator mechatronic system (EMS) contains a mechanical subsystem which is characterized by its resonant frequency. In order to achieve high performance of the whole system, the control part of the EMS inevitably excites resonant circuits causing the occurrence of vibration. This paper proposes a synergistic solution based on the jerk control and the upgrade of the speed controller with a band-stop filter to restore lost ride comfort and speed control caused by vibration. The band-stop filter eliminates the resonant component from the speed controller spectra and jerk control provides operating of the speed controller in a linear mode as well as increased ride comfort. The original method for band-stop filter tuning based on Goertzel algorithm and Kiefer search algorithm is proposed in this paper. In order to generate the speed reference trajectory which can be defined by different shapes and amplitudes of jerk, a unique generalized model is proposed. The proposed algorithm is integrated in the power drive control algorithm and implemented on the digital signal processor. Through experimental verifications on a scale down prototype of the EMS it has been verified that only synergistic effect of controlling jerk and filtrating the reference torque can completely eliminate vibrations.

  14. Chronic corticosterone-induced impaired cognitive flexibility is not due to suppressed adult hippocampal neurogenesis.

    Science.gov (United States)

    Lui, E; Salim, M; Chahal, M; Puri, N; Marandi, E; Quadrilatero, J; Satvat, E

    2017-08-14

    Hippocampal neurogenesis has been implicated in the etiology of depression. Recent studies suggest new neurons add flexibility to hippocampal-dependent learning and memory. We hypothesized that suppressed hippocampal neurogenesis may contribute to impaired cognitive flexibility associated with depression. The chronic corticosterone (CORT)-induced animal model of depression was used. In Experiment 1, rats received either CORT (40mg/kg) or vehicle injections for 21days and were subjected to Water maze during the last six days of drug treatment. No group differences were found during the spatial learning phase; however, cognitive flexibility, measured by reversal training, was significantly impaired in the CORT-treated rats. The probe test revealed enhanced memory of the new platform location for the CORT-treated rats. Given the time newborn neurons require to mature, we presumed if impaired cognitive flexibility seen in Experiment 1 were due to suppressed neurogenesis, terminating CORT treatment 3days prior to behavioural testing should still induce the impairment. Therefore, Experiment 2 was similar to Experiment 1, except that CORT injections were terminated 3days prior to behavioural assessment. However, not only was spatial learning significantly enhanced in the CORT-treated rats, but there were also no group differences during reversal or probe tests. Bromodeoxyruidine, administered a day after the first drug treatments in both experiments, was quantified and revealed the number of new neurons were the same in both groups in both experiments. Results suggest cognitive flexibility is impaired in the CORT-induced animal model of depression; an effect that is reversible and independent of suppressed hippocampal neurogenesis. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Suppression of Quasiparticle Scattering Signals in Bilayer Graphene Due to Layer Polarization and Destructive Interference

    Science.gov (United States)

    Jolie, Wouter; Lux, Jonathan; Pörtner, Mathias; Dombrowski, Daniela; Herbig, Charlotte; Knispel, Timo; Simon, Sabina; Michely, Thomas; Rosch, Achim; Busse, Carsten

    2018-03-01

    We study chemically gated bilayer graphene using scanning tunneling microscopy and spectroscopy complemented by tight-binding calculations. Gating is achieved by intercalating Cs between bilayer graphene and Ir(111), thereby shifting the conduction band minima below the chemical potential. Scattering between electronic states (both intraband and interband) is detected via quasiparticle interference. However, not all expected processes are visible in our experiment. We uncover two general effects causing this suppression: first, intercalation leads to an asymmetrical distribution of the states within the two layers, which significantly reduces the scanning tunneling spectroscopy signal of standing waves mainly present in the lower layer; second, forward scattering processes, connecting points on the constant energy contours with parallel velocities, do not produce pronounced standing waves due to destructive interference. We present a theory to describe the interference signal for a general n -band material.

  16. Vibration suppression control of smart piezoelectric rotating truss structure by parallel neuro-fuzzy control with genetic algorithm tuning

    Science.gov (United States)

    Lin, J.; Zheng, Y. B.

    2012-07-01

    The main goal of this paper is to develop a novel approach for vibration control on a piezoelectric rotating truss structure. This study will analyze the dynamics and control of a flexible structure system with multiple degrees of freedom, represented in this research as a clamped-free-free-free truss type plate rotated by motors. The controller has two separate feedback loops for tracking and damping, and the vibration suppression controller is independent of position tracking control. In addition to stabilizing the actual system, the proposed proportional-derivative (PD) control, based on genetic algorithm (GA) to seek the primary optimal control gain, must supplement a fuzzy control law to ensure a stable nonlinear system. This is done by using an intelligent fuzzy controller based on adaptive neuro-fuzzy inference system (ANFIS) with GA tuning to increase the efficiency of fuzzy control. The PD controller, in its assisting role, easily stabilized the linear system. The fuzzy controller rule base was then constructed based on PD performance-related knowledge. Experimental validation for such a structure demonstrates the effectiveness of the proposed controller. The broad range of problems discussed in this research will be found useful in civil, mechanical, and aerospace engineering, for flexible structures with multiple degree-of-freedom motion.

  17. Hybrid PD and effective multi-mode positive position feedback control for slewing and vibration suppression of a smart flexible manipulator

    International Nuclear Information System (INIS)

    Lou, Jun-qiang; Wei, Yan-ding; Yang, Yi-ling; Xie, Feng-ran

    2015-01-01

    A hybrid control strategy for slewing and vibration suppression of a smart flexible manipulator is presented in this paper. It consists of a proportional derivative controller to realize motion control, and an effective multi-mode positive position feedback (EMPPF) controller to suppress the multi-mode vibration. Rather than treat each mode equally as the standard multi-mode PPF, the essence of the EMPPF is that control forces of different modes are applied according to the mode parameters of the respective modes, so the vibration modes with less vibration energy receive fewer control forces. Stability conditions for the close loop system are established through stability analysis. Optimal parameters of the EMPPF controller are obtained using the method of root locus analysis. The performance of the proposed strategy is demonstrated by simulation and experiments. Experimental results show that the first two vibration modes of the manipulator are effectively suppressed. The setting time of the setup descends approximately 55%, reaching 3.12 s from 5.67 s. (paper)

  18. Optimal Placement of Piezoelectric Macro Fiber Composite Patches on Composite Plates for Vibration Suppression

    Directory of Open Access Journals (Sweden)

    Eduardo Padoin

    Full Text Available AbstractThis work presents a new methodology for the parametric optimization of piezoelectric actuators installed in laminated composite structures, with the objective of controlling structural vibrations. Problem formulation is the optimum location of a Macro Fiber Composite (MFC actuator patch by means the maximization of the controllability index. The control strategy is based on a Linear Quadratic Regulator (LQR approach. For the structural analysis, the modeling of the interaction between the MFC and the structure is made taking into account the active material as one of the orthotropic laminate shell layers. The actuation itself is modeled as an initial strain arising from the application of an electric potential which deforms the rest of the structure. Thereby, modeling the electric field and the electromechanical coupling within the actuator is avoided because these effects are considered analytically. Numerical simulations show that the structural model presents good agreement with numerical and experimental results. Furthermore, the results show that optimizing the location of the actuator in the structure helps the control algorithm to reduce induced structural vibration.

  19. Time-domain prefilter design for enhanced tracking and vibration suppression in machine motion control

    Science.gov (United States)

    Cole, Matthew O. T.; Shinonawanik, Praween; Wongratanaphisan, Theeraphong

    2018-05-01

    Structural flexibility can impact negatively on machine motion control systems by causing unmeasured positioning errors and vibration at locations where accurate motion is important for task execution. To compensate for these effects, command signal prefiltering may be applied. In this paper, a new FIR prefilter design method is described that combines finite-time vibration cancellation with dynamic compensation properties. The time-domain formulation exploits the relation between tracking error and the moment values of the prefilter impulse response function. Optimal design solutions for filters having minimum H2 norm are derived and evaluated. The control approach does not require additional actuation or sensing and can be effective even without complete and accurate models of the machine dynamics. Results from implementation and testing on an experimental high-speed manipulator having a Delta robot architecture with directionally compliant end-effector are presented. The results show the importance of prefilter moment values for tracking performance and confirm that the proposed method can achieve significant reductions in both peak and RMS tracking error, as well as settling time, for complex motion patterns.

  20. CargoVibes: human response to vibration due to freight rail traffic

    NARCIS (Netherlands)

    Waddington, D.; Woodcock, J.; Smith, M.G.; Janssen, S.A.; Persson Waye, K.

    2015-01-01

    The aim of this paper is to present an overview of the research concerning human response to vibration conducted in the EU FP7 CargoVibes project. The European Union-funded project CargoVibes involved 10 partners from 8 nations and ran from April 2011 to April 2014. The project was concerned with

  1. Assessment on transient sound radiation of a vibrating steel bridge due to traffic loading

    Science.gov (United States)

    Zhang, He; Xie, Xu; Jiang, Jiqing; Yamashita, Mikio

    2015-02-01

    Structure-borne noise induced by vehicle-bridge coupling vibration is harmful to human health and living environment. Investigating the sound pressure level and the radiation mechanism of structure-borne noise is of great significance for the assessment of environmental noise pollution and noise control. In this paper, the transient noise induced by vehicle-bridge coupling vibration is investigated by employing the hybrid finite element method (FEM) and boundary element method (BEM). The effect of local vibration of the bridge deck is taken into account and the sound responses of the structure-borne noise in time domain is obtained. The precision of the proposed method is validated by comparing numerical results to the on-site measurements of a steel girder-plate bridge in service. It implies that the sound pressure level and its distribution in both time and frequency domains may be predicted by the hybrid approach of FEM-BEM with satisfactory accuracy. Numerical results indicate that the vibrating steel bridge radiates high-level noise because of its extreme flexibility and large surface area for sound radiation. The impact effects of the vehicle on the sound pressure when leaving the bridge are observed. The shape of the contour lines in the area around the bridge deck could be explained by the mode shapes of the bridge. The moving speed of the vehicle only affects the sound pressure components with frequencies lower than 10 Hz.

  2. Unusual motions due to nonlinear effects in a driven vibrating string

    Science.gov (United States)

    Hanson, Roger J.

    2005-09-01

    Usual nonlinear effects observed in a sinusoidally driven vibrating string include generation of motion perpendicular to the driving plane, sudden jumps of amplitude and associated hysteresis, and generation of higher harmonics. In addition, under some conditions, there can be a rich variety of unusual, very complex motions of a point on the string, the pattern of which, together with associated harmonic (and sometimes subharmonic) content, can change dramatically with a slight change in driving frequency or sometimes with constant driving frequency and force. Intrinsic string asymmetries can also have a profound effect on the behavior. In a brass harpsichord string (wire) such asymmetries can cause a small splitting of each natural frequency of free vibration into two closely spaced frequencies (relative separation ~0.2% to 2%, strongly dependent on tension.) The two frequency components are associated, respectively, with the transverse motion along two orthogonal characteristic wire axes. Emphasis will be on display of optically detected unusual motion patterns of a point on the string, including an example of a pattern period of 10 s when driving at 50 Hz. See R. J. Hanson et al., J. Acoust. Soc. Am. 117, 400-412 (2005) for a more complete treatment.

  3. Size-dependent bending and vibration behaviour of piezoelectric nanobeams due to flexoelectricity

    International Nuclear Information System (INIS)

    Yan Zhi; Jiang Liying

    2013-01-01

    Flexoelectricity, representing a spontaneous electric polarization induced by a non-uniform strain field (or strain gradient), is believed to become manifest and be responsible for the size-dependent properties of dielectric materials at the nanoscale. In this paper, the influence of the flexoelectric effect on the static bending and free vibration of a simply supported piezoelectric nanobeam is investigated based on the extended linear piezoelectricity theory and the Timoshenko beam model. The governing equations of the piezoelectric nanobeam with non-homogeneous boundary conditions are obtained from Hamilton's principle. Explicit expressions of the beam deflection and resonant frequency are derived to show the size-dependency of the flexoelectric effect. It is found that the flexoelectricity has a significant effect on the deflection of the bending beam and may reverse the deflection direction under certain loading conditions. Simulation results also indicate that the influence of the flexoelectricity on the vibration behaviour of the piezoelectric nanobeam is more prominent for beams with smaller thickness. Thus, it is suggested that possible frequency tuning of piezoelectric nanobeams by adjusting the applied electrical load should incorporate the flexoelectric effect. The current study can be claimed as helpful for qualitatively characterizing the trend of the flexoelectric effect on the mechanical responses of piezoelectric nanobeams. (paper)

  4. Size-dependent bending and vibration behaviour of piezoelectric nanobeams due to flexoelectricity

    Science.gov (United States)

    Yan, Zhi; Jiang, Liying

    2013-09-01

    Flexoelectricity, representing a spontaneous electric polarization induced by a non-uniform strain field (or strain gradient), is believed to become manifest and be responsible for the size-dependent properties of dielectric materials at the nanoscale. In this paper, the influence of the flexoelectric effect on the static bending and free vibration of a simply supported piezoelectric nanobeam is investigated based on the extended linear piezoelectricity theory and the Timoshenko beam model. The governing equations of the piezoelectric nanobeam with non-homogeneous boundary conditions are obtained from Hamilton's principle. Explicit expressions of the beam deflection and resonant frequency are derived to show the size-dependency of the flexoelectric effect. It is found that the flexoelectricity has a significant effect on the deflection of the bending beam and may reverse the deflection direction under certain loading conditions. Simulation results also indicate that the influence of the flexoelectricity on the vibration behaviour of the piezoelectric nanobeam is more prominent for beams with smaller thickness. Thus, it is suggested that possible frequency tuning of piezoelectric nanobeams by adjusting the applied electrical load should incorporate the flexoelectric effect. The current study can be claimed as helpful for qualitatively characterizing the trend of the flexoelectric effect on the mechanical responses of piezoelectric nanobeams.

  5. Structural equation modelling of lower back pain due to whole-body vibration exposure in the construction industry.

    Science.gov (United States)

    Vitharana, Vitharanage Hashini Paramitha; Chinda, Thanwadee

    2017-09-21

    Whole-body vibration (WBV) exposure is a health hazard among workers, causing lower back pain (LBP) in the construction industry. This study examines key factors affecting LBP due to WBV exposure using exploratory factor analysis and structural equation modelling. The results confirm five key factors (equipment, job related, organizational, personal, social context) with their 17 associated items. The organizational factor is found the most important, as it influences the other four factors. The results also show that appropriate seat type, specific training programme, job rotation, workers' satisfaction and workers' physical condition are crucial in reducing LBP due to WBV exposure. Moreover, provision of new machines without proper training and good working condition might not help reduce LBP due to WBV exposure. The results help the construction companies to better understand key factors affecting LBP due to WBV exposure, and to plan for a better health improvement programme.

  6. Pressure distribution due to steam bubble collapse in a BWR suppression chamber

    International Nuclear Information System (INIS)

    Giencke, E.

    1979-01-01

    For the pressure time history at the walls of a suppression chamber due to a steam bubble collaps at the condenser pipes interests, expecially the influence of the wall elasticity and the position of the condenser pipes. Two problems are to solve: the pressure time history in the steam bubble and at the walls during the collaps and the pressure distribution at the walls. Both problems are coupled with each other, but the influence of the wall elasticity on the pressure time history in the steam bubble is usually small. Thus the two problems may be solved one after each other. For simplifying the analysis the steam bubble surface may be idealized as a sphere during the whole collaps time. Then the resulting pressure time history is be put on the fluid-structure-system. To show the influence of the containment-elasticity it is favourable to investigate both the rigid and the elastic containment. Because the condenser pipes are arranged in a regular scheme, two limit loading cases are to distinguish. Collapses occur simultaneously with the same intensity at all condenser pipes and a strong collaps occurs only at one condenser pipe or a small group of pipes. When including wall elasticity first the modes of the fluid-structure-system are to analyse and then the dynamical responses of the modes. The coupling effects between the pressure time history in the bubble and at the walls are discussed and then how the membrane and bending stiffness of the walls and the buttomstructure influence the pressure distribution, both for steel and concrete structure. Finally simple models for the analysis are derived and the analytical results are compared with experiments. (orig.)

  7. Orthostatic hypotension due to suppression of vasomotor outflow after amphetamine intoxication

    NARCIS (Netherlands)

    Smit, A. A.; Wieling, W.; Voogel, A. J.; Koster, R. W.; van Zwieten, P. A.

    1996-01-01

    Ten hours after ingestion of amphetamines, a previously healthy 17-year-old female adolescent experienced dizziness on standing. Examination revealed pronounced drowsiness and severe orthostatic hypotension. Assessment of arterial baroreflex function suggested that suppressed sympathetic vasomotor

  8. Dilated and unreactive pupils and burst-suppression on electroencephalography due to buproprion overdose.

    Science.gov (United States)

    Mundi, Jyoti Pathria; Betancourt, Jaime; Ezziddin, Omar; Tremayne, Brandie; Majic, Tamara; Mosenifar, Zab

    2012-01-01

    Burst-suppression pattern on electroencephalography (EEG) occurs upon dissociation of the cortex from underlying brain structures. Unless the pattern is a physiologic consequence of administered sedatives, this electroencephalographic pattern is indicative of a poor neurologic outcome and high mortality. We report a case of a 29-year-old female thought to be brain dead based on initial physical examination and EEG findings of burst-suppression, who was later found to have supratherapeutic serum levels of bupropion. This is the second documented case of burst-suppression pattern on EEG in a patient who overdosed on bupropion. We propose that burst-suppression in the setting of bupropion toxicity may revert with drug clearance.

  9. Assessment of the Vibrations Effects Caused by Technical Seismicity Due to the Railway traffic on High-sensitivity Machinery

    Science.gov (United States)

    Papán, Daniel; Valašková, Veronika; Demeterová, Katarína

    2016-10-01

    The numerical and experimental approach in structural dynamics problems is more and more current nowadays. This approach is applied and solved in many research and developing institutions of the all the world. Vibrations effect caused by passing trains used in manufacturing facilities can affect the quality of the production activity. This effect is possible to be solved by a numerical or an experimental way. Numerical solution is not so financially and time demanding. The main aim of this article is to focus on just experimental measurement of this problem. In this paper, the case study with measurement due to cramped conditions realized in situ is presented. The case study is located close to railway. The vibration effect caused by passing trains on the high-sensitivity machinery contained in this object were observed. The structure was a high-sensitivity machine that was placed in a construction process. For the measurements, the high-sensitivity standard vibrations equipment was used. The assessments of measurements’ results were performed for the technological conditions and Slovak Standard Criteria. Both of these assessments were divided to amplitude and frequency domain. The amplitude criterion is also divided to peak particle velocity and RMS (Root Mean Square). Frequency domain assessment were realised using the frequency response curves obtained from high-sensitivity machinery manufacturer. The frequency limits are established for each axis of triaxle system. The measurement results can be predicted if the vibration have to be reduced. Measurement implemented in the production hall should obtain materials to determine the seismic loading and response of production machinery caused by technical seismicity.

  10. Suppression of transpiration due to cloud immersion in a seasonally dry Mexican Weeping Pine plantation

    NARCIS (Netherlands)

    Alvarado-Barrientos, M.S.; Holwerda, F.; Asbjornsen, H.; Dawson, T.E.; Bruijnzeel, L.A.

    2013-01-01

    Cloud immersion affects the water budget of fog-affected forests not only by introducing an additional source of water (via cloud water interception by the canopy), but also by suppressing plant transpiration. The latter effect is often overlooked and not routinely quantified, restricting a complete

  11. Suppressed reflectivity due to spin-controlled localization in a magnetic semiconductor

    NARCIS (Netherlands)

    Mena, FP; DiTusa, JF; van der Marel, D; Aeppli, G; Young, DP; Damascelli, A; Mydosh, JA

    The narrow gap semiconductor FeSi owes its strong paramagnetism to electron-correlation effects. Partial Co substitution for Fe produces a spin-polarized doped semiconductor. The spin polarization causes suppression of the metallic reflectivity and increased scattering of charge carriers, in

  12. Experimental investigation of the vibration response of a flexible tube due to simulated reactor core, cross and annular exit flows

    International Nuclear Information System (INIS)

    Haslinger, K.H.; Martin, M.L.; Higgins, W.H.; Rossano, F.V.

    1989-01-01

    Instrumentation tubes in pressurized nuclear reactors have experienced wear due to excessive flow-induced vibrations. Experiments to identify the predominant flow excitation mechanism at a particular plant, and to develop a sleeve design to remedy the wear problem are reported. An instrumented flow visualization model enabled simulation of a wide range of individual or combined reactor core flow, cross flow and thimble flow conditions. The instrumentation scheme adopted for these experiments used proximity displacement transducers and a force transducer to measure respectively tube motion and contact/impact forces at the wear region. Extensive testing of the original, in-plant configuration identified the normal core flow as the primary source of excitation. Shielding the In-Core-Instrumentation thimble tube from the normal core flow curtailed vibration amplitudes; however, thimble flow excitation then became more pronounced. Various outlet nozzle configurations were investigated. An internal cavity combined with radial outlet slots became the optimum solution for the problem. The paper presents typical test data in the form of orbital tube motion, spectrum analysis and time history collages. The effectiveness of shielding the instrumentation tube from the flow is demonstrated. (author)

  13. Prediction of pressure tube fretting-wear damage due to fuel vibration

    International Nuclear Information System (INIS)

    Yetisir, M.; Fisher, N.J.

    1997-01-01

    Fretting marks between fuel bundle bearing pads and pressure tubes have been observed at the inlet end of some Darlington Nuclear Generating Station (NGS) and Bruce NGS fuel channels. The excitation mechanisms that lead to fretting are not fully understood. In this paper, the possibility of bearing pad-to-pressure tube fretting due to turbulence-induced motion of the fuel element is investigated. Numerical simulations indicate that this mechanism by itself is not likely to cause the level of fretting experienced in Darlington and Bruce NGSs. (orig.)

  14. Control of transient vibrations due to stage movements in 6-dof active pneumatic table by inertial force compensation

    Science.gov (United States)

    Sun, Jong-Oh; Kim, Kwang-joon

    2013-10-01

    Passive pneumatic tables are popularly used in precision measurements or processes for isolation of ground vibrations over frequency ranges higher than resonance frequencies of a few Hz typically. Recently, active pneumatic tables are also used often because the passive systems are liable to table excitations in the low resonance frequency ranges, causing long settling times. In studies on the active tables, disturbances onto the tables were often regarded to be unknown and, hence, feedback control algorithms were implemented. However, the disturbances are mostly due to inertial forces due to movement of equipment on the table, e.g., x-y stages. Such a movement is given relative to the table as command inputs. Since absolute motion of the table is normally measured in an active isolation table, absolute motion of the equipment can be easily estimated for calculation of the inertial force exerted onto the table by the moving equipment. Consequently, by compensating dynamic pressure inside the pneumatic chamber to counteract with the inertia force due to the equipment motion, resultant forces acting onto the table can be made zero. In this paper, how to apply the proposed feed-forward control algorithm to a 6-degree of freedom active pneumatic table with time-delay pneumatic control is presented. Performance of the inertial force compensation control evaluated through experiments is also discussed.

  15. Experiments on Suppression of Thermocapillary Oscillations in Sodium Nitrate Floating Half-Zones by High-frequency End-wall Vibrations

    Science.gov (United States)

    Anilkumar, A.; Grugel, R. N.; Bhowmick, J.; Wang, T.

    2004-01-01

    Experiments to suppress thermocapillary oscillations using high-frequency vibrations were carried out in sodium nitrate floating half-zones. Such a half-zone is formed by melting one end of a vertically held sodium nitrate crystal rod in contact with a hot surface at the top. Thermocapillary convection occurs in the melt because of the temperature gradient at the free surface of the melt. In the experiments, when thermocapillary oscillations occurred, the bottom end of the crystal rod was vibrated at a high frequency to generate a streaming flow in a direction opposite to that of the thermocapillary convection. It is observed that, by generating a sufficiently strong streaming flow, the thermocapillary flow can be offset enough such that the associated thermocapillary oscillations can be quenched.

  16. Numerical investigation of natural convection heat transfer in a cylindrical enclosure due to ultrasonic vibrations.

    Science.gov (United States)

    Talebi, Maryam; Setareh, Milad; Saffar-Avval, Majid; Hosseini Abardeh, Reza

    2017-04-01

    Application of ultrasonic waves for heat transfer augmentation has been proposed in the last few decades. Due to limited researches on acoustic streaming induced by ultrasonic oscillation, the effect of ultrasonic waves on natural convection heat transfer is the main purpose of this paper. At first, natural convection on up-ward-facing heating surface in a cylindrical enclosure filled with air is investigated numerically by the finite difference method, then the effect of upper surface oscillation on convection heat transfer is considered. The conservation equations in Lagrangian approach and compressible fluid are assumed for the numerical simulation. Results show that acoustic pressure will become steady after some milliseconds also pressure oscillation amplitude and acoustic velocity components will be constant therefore steady state velocity is used for solving energy equation. Results show that Enhancement of heat transfer coefficient can be up to 175% by induced ultrasonic waves. In addition, the effect of different parameters on acoustic streaming and heat transfer has been studied. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Somatosensory Evoked Potentials suppression due to remifentanil during spinal operations; a prospective clinical study

    Directory of Open Access Journals (Sweden)

    Christodoulou Anastasios

    2010-05-01

    Full Text Available Abstract Background Somatosensory evoked potentials (SSEP are being used for the investigation and monitoring of the integrity of neural pathways during surgical procedures. Intraoperative neurophysiologic monitoring is affected by the type of anesthetic agents. Remifentanil is supposed to produce minimal or no changes in SSEP amplitude and latency. This study aims to investigate whether high doses of remifentanil influence the SSEP during spinal surgery under total intravenous anesthesia. Methods Ten patients underwent spinal surgery. Anesthesia was induced with propofol (2 mg/Kg, fentanyl (2 mcg/Kg and a single dose of cis-atracurium (0.15 mg/Kg, followed by infusion of 0.8 mcg/kg/min of remifentanil and propofol (30-50 mcg/kg/min. The depth of anesthesia was monitored by Bispectral Index (BIS and an adequate level (40-50 of anesthesia was maintained. Somatosensory evoked potentials (SSEPs were recorded intraoperatively from the tibial nerve (P37 15 min before initiation of remifentanil infusion. Data were analysed over that period. Results Remifentanil induced prolongation of the tibial SSEP latency which however was not significant (p > 0.05. The suppression of the amplitude was significant (p Conclusion Remifentanil in high doses induces significant changes in SSEP components that should be taken under consideration during intraoperative neuromonitoring.

  18. Study on hydraulic exciting vibration due to flexible valve in pump system with method of characteristics in the time domain

    Science.gov (United States)

    Yu, Y. H.; Liu, D.; Yang, X. F.; Si, J.

    2017-08-01

    To analyse the flow characteristics of leakage as well as the mechanism of selfexcited vibration in valves, the method of characteristics was used to assess the effect of flexible valve leakage on the self-excited vibration in water-supply pump system. Piezometric head in upstream of the valve as a function of time was obtained. Two comparative schemes were proposed to simulate the process of self-excited vibration by changing the length, the material of the pipeline and the leakage of valves in the above pump system. It is shown that the length and material of the pipe significantly affect the amplitude and cycle of self-excited vibration as well as the increasing rate of the vibration amplitude. In addition, the leakage of the valve has little influence on the amplitude and cycle of self-excited vibration, but has a significant effect on the increasing rate of vibration amplitude. A pipe explosion accident may occur without the inhibiting of self-excited vibration.

  19. On the Mass and Luminosity Functions of Tidal Disruption Flares: Rate Suppression due to Black Hole Event Horizons

    Science.gov (United States)

    van Velzen, S.

    2018-01-01

    The tidal disruption of a star by a massive black hole is expected to yield a luminous flare of thermal emission. About two dozen of these stellar tidal disruption flares (TDFs) may have been detected in optical transient surveys. However, explaining the observed properties of these events within the tidal disruption paradigm is not yet possible. This theoretical ambiguity has led some authors to suggest that optical TDFs are due to a different process, such as a nuclear supernova or accretion disk instabilities. Here we present a test of a fundamental prediction of the tidal disruption event scenario: a suppression of the flare rate due to the direct capture of stars by the black hole. Using a recently compiled sample of candidate TDFs with black hole mass measurements, plus a careful treatment of selection effects in this flux-limited sample, we confirm that the dearth of observed TDFs from high-mass black holes is statistically significant. All the TDF impostor models we consider fail to explain the observed mass function; the only scenario that fits the data is a suppression of the rate due to direct captures. We find that this suppression can explain the low volumetric rate of the luminous TDF candidate ASASSN-15lh, thus supporting the hypothesis that this flare belongs to the TDF family. Our work is the first to present the optical TDF luminosity function. A steep power law is required to explain the observed rest-frame g-band luminosity, {dN}/{{dL}}g\\propto {L}g-2.5. The mean event rate of the flares in our sample is ≈ 1× {10}-4 galaxy‑1 yr‑1, consistent with the theoretically expected tidal disruption rate.

  20. A semi-active H∞ control strategy with application to the vibration suppression of nonlinear high-rise building under earthquake excitations.

    Science.gov (United States)

    Yan, Guiyun; Chen, Fuquan; Wu, Yingxiong

    2016-01-01

    Different from previous researches which mostly focused on linear response control of seismically excited high-rise buildings, this study aims to control nonlinear seismic response of high-rise buildings. To this end, a semi-active control strategy, in which H∞ control algorithm is used and magneto-rheological dampers are employed for an actuator, is presented to suppress the nonlinear vibration. In this strategy, a modified Kalman-Bucy observer which is suitable for the proposed semi-active strategy is developed to obtain the state vector from the measured semi-active control force and acceleration feedback, taking into account of the effects of nonlinearity, disturbance and uncertainty of controlled system parameters by the observed nonlinear accelerations. Then, the proposed semi-active H∞ control strategy is applied to the ASCE 20-story benchmark building when subjected to earthquake excitation and compared with the other control approaches by some control criteria. It is indicated that the proposed semi-active H∞ control strategy provides much better control performances by comparison with the semi-active MPC and Clipped-LQG control approaches, and can reduce nonlinear seismic response and minimize the damage in the buildings. Besides, it enhances the reliability of the control performance when compared with the active control strategy. Thus, the proposed semi-active H∞ control strategy is suitable for suppressing the nonlinear vibration of high-rise buildings.

  1. Numerical Modelling of Building Vibrations due to Railway Traffic: Analysis of the Mitigation Capacity of a Wave Barrier

    Directory of Open Access Journals (Sweden)

    Fran Ribes-Llario

    2017-01-01

    Full Text Available Transmission of train-induced vibrations to buildings located in the vicinity of the track is one of the main negative externalities of railway transport, since both human comfort and the adequate functioning of sensitive equipment may be compromised. In this paper, a 3D FEM model is presented and validated with data from a real track stretch near Barcelona, Spain. Furthermore, a case study is analyzed as an application of the model, in order to evaluate the propagation and transmission of vibrations induced by the passage of a suburban train to a nearby 3-storey building. As a main outcome, vertical vibrations in the foundation slab are found to be maximum in the corners, while horizontal vibrations keep constant along the edges. The propagation within the building structure is also studied, concluding that vibrations invariably increase in their propagation upwards the building. Moreover, the mitigation capacity of a wave barrier acting as a source isolation is assessed by comparing vibration levels registered in several points of the building structure with and without the barrier. In this regard, the wave barrier is found to effectively reduce vibration in both the soil and the structure.

  2. Adaptive Vibration Suppression System: An Iterative Control Law for a Piezoelectric Actuator Shunted by a Negative Capacitor

    Czech Academy of Sciences Publication Activity Database

    Kodejska, M.; Mokrý, Pavel; Linhart, V.; Václavík, Jan; Sluka, T.

    2012-01-01

    Roč. 59, č. 12 (2012), s. 2785-2796 ISSN 0885-3010 R&D Projects: GA MŠk(CZ) ED2.1.00/03.0079 Institutional support: RVO:61389021 Keywords : ELASTICITY CONTROL * HARMONIC EXCITATIONS * STRUCTURAL VIBRATION * FEEDBACK-CONTROL * CIRCUITS * MEMBRANE Subject RIV: BI - Acoustics Impact factor: 1.822, year: 2012

  3. A fast converging adaptive control scheme for suppression of broadband disturbances on a multi-variable vibration isolation setup

    NARCIS (Netherlands)

    Nijsse, G.; van Dijk, J.; Jonker, J.B.; Sas, P.; De Munck, M.

    2006-01-01

    For research and development, a single reference input multiple actuator input multiple error sensor output vibration isolation setup is realized. The objective of the setup is to investigate if the flexible receiver structure can be isolated from the rigid source structure by six piezo-electric

  4. A journal bearing with variable geometry for the suppression of vibrations in rotating shafts: Simulation, design, construction and experiment

    Science.gov (United States)

    Chasalevris, Athanasios; Dohnal, Fadi

    2015-02-01

    The idea for a journal bearing with variable geometry was formerly developed and investigated on its principles of operation giving very optimistic theoretical results for the vibration quenching of simple and more complicated rotor bearing systems during the passage through the first critical speed. The journal bearing with variable geometry is presented in this paper in its final form with the detailed design procedure. The current journal bearing was constructed in order to be applied in a simple real rotor bearing system that already exists as an experimental facility. The current paper presents details on the manufactured prototype bearing as an experimental continuation of previous works that presented the simulation of the operating principle of this journal bearing. The design parameters are discussed thoroughly under the numerical simulation for the fluid film pressure in dependency of the variable fluid film thickness during the operation conditions. The implementation of the variable geometry bearing in an experimental rotor bearing system is outlined. Various measurements highlight the efficiency of the proposed bearing element in vibration quenching during the passage through resonance. The inspiration for the current idea is based on the fact that the alteration of the fluid film characteristics of stiffness and damping during the passage through resonance results in vibration quenching. This alteration of the bearing characteristics is achieved by the introduction of an additional fluid film thickness using the passive displacement of the lower half-bearing part. • The contribution of the current journal bearing in vibration quenching. • Experimental evidence for the VGJB contribution.

  5. Theory of vibration protection

    CERN Document Server

    Karnovsky, Igor A

    2016-01-01

    This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...

  6. Multi-Mode Vibration Suppression in MIMO Systems by Extending the Zero Placement Input Shaping Technique: Applications to a 3-DOF Piezoelectric Tube Actuator

    Directory of Open Access Journals (Sweden)

    Yasser Al Hamidi

    2016-04-01

    Full Text Available Piezoelectric tube actuators are extensively used in scanning probe microscopes to provide dynamic scanning motions in open-loop operations. Furthermore, they are employed as micropositioners due to their high bandwidth, high resolution and ease of excitation. However, these piezoelectric micropositioners exhibit badly damped vibrations that occur when the input excites the dynamic response, which tends to degrade positioning accuracy and performance. This paper deals with vibrations’ feedforward control of a multi-degrees of freedom (DOF piezoelectric micropositioner in order to damp the vibrations in the direct axes and to reduce the cross-couplings. The novelty in this paper relative to the existing vibrations feedforward controls is the simplicity in design approach, the minimal number of shaper impulses for each input required to damp all modes of vibration at each output, and the account for the strong cross-couplings which only occur in multi-DOF cases. A generalization to a multiple degrees of freedom actuator is first proposed. Then simulation runs on a 3-DOF piezoelectric tube micropositioner have been effectuated to demonstrate the efficiency of the proposed method. Finally, experimental tests were carried out to validate and to confirm the predicted simulation.

  7. Tunable Passive Vibration Suppressor

    Science.gov (United States)

    Boechler, Nicholas (Inventor); Dillon, Robert Peter (Inventor); Daraio, Chiara (Inventor); Davis, Gregory L. (Inventor); Shapiro, Andrew A. (Inventor); Borgonia, John Paul C. (Inventor); Kahn, Daniel Louis (Inventor)

    2016-01-01

    An apparatus and method for vibration suppression using a granular particle chain. The granular particle chain is statically compressed and the end particles of the chain are attached to a payload and vibration source. The properties of the granular particles along with the amount of static compression are chosen to provide desired filtering of vibrations.

  8. Aeroservoelastic suppression of LCO due to free-play using a combined analytical and experimental approach, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Aerodynamic control surfaces with excessive free-play can cause limit cycle oscillations (LCO), a sustained vibration of constant amplitude that is caused by a...

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

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel; Dahl, Jonas

    2010-01-01

    Resonant vibrations of a fluid-conveying pipe are investigated, with special consideration to axial shifts in vibration phase accompanying fluid flow and various imperfections. This is relevant for understanding elastic wave propagation in general, and for the design and trouble-shooting of phase......-shift measuring devices such as Coriolis mass flowmeters in particular. Small imperfections related to elastic and dissipative support conditions are specifically addressed, but the suggested approach is readily applicable to other kinds of imperfection, e.g. non-uniform stiffness or mass, non...... the symmetric part of damping as well as non-uniformity in mass or stiffness do not affect phase shift. The validity of such hypotheses can be tested using detailed fluid-structure interaction computer models or laboratory experiments....

  10. Multi-modal vibration amplitudes of taut inclined cables due to direct and/or parametric excitation

    Science.gov (United States)

    Macdonald, J. H. G.

    2016-02-01

    Cables are often prone to potentially damaging large amplitude vibrations. The dynamic excitation may be from external loading or motion of the cable ends, the latter including direct excitation, normally from components of end motion transverse to the cable, and parametric excitation induced by axial components of end motion causing dynamic tension variations. Geometric nonlinearity can be important, causing stiffening behaviour and nonlinear modal coupling. Previous analyses of the vibrations, often neglecting sag, have generally dealt with direct and parametric excitation separately or have reverted to numerical solutions of the responses. Here a nonlinear cable model is adopted, applicable to taut cables such as on cable-stayed bridges, that allows for cable inclination, small sag (such that the vibration modes are similar to those of a taut string), multiple modes in both planes and end motion and/or external forcing close to any natural frequency. Based on the method of scaling and averaging it is found that, for sinusoidal inputs and positive damping, non-zero steady state responses can only occur in the modes in each plane with natural frequencies close to the excitation frequency and those with natural frequencies close to half this frequency. Analytical solutions, in the form of non-dimensional polynomial equations, are derived for the steady state vibration amplitudes in up to three modes simultaneously: the directly excited mode, the corresponding nonlinearly coupled mode in the orthogonal plane and a parametrically excited mode with half the natural frequency. The stability of the solutions is also identified. The outputs of the equations are consistent with previous results, where available. Example results from the analytical solutions are presented for a typical inclined bridge cable subject to vertical excitation of the lower end, and they are validated by numerical integration of the equations of motion and against some previous experimental

  11. The Effects of Approach Angle and Rake Angle Due to Chatter Vibrations on Surface Roughness in Turning

    OpenAIRE

    NEŞELİ, Süleyman; YALDIZ, Süleyman

    2007-01-01

    In this study, the effect of the chatter vibrations depend on tool geometry on surface roughness in turning has been investigated. Machining process in universal lathe is carried out on AISI 1040 steel in dry cutting condition using various approaching/entering angles (60°, 75°, 90°) and rake angles (-3°,-6°,-9°) at depth of cut of 0.5 mm. During cutting processes, tool nose radius and tool overhang (tool noise of kept point distance) and cutting speed, feed rate and spindle speed as cutting ...

  12. Structural vibration and acoustic radiation of coupled propeller-shafting and submarine hull system due to propeller forces

    Science.gov (United States)

    Qu, Yegao; Su, Jinpeng; Hua, Hongxing; Meng, Guang

    2017-08-01

    This paper investigates the structural and acoustic responses of a coupled propeller-shafting and submarine pressure hull system under different propeller force excitations. The entire system, which consists of a rigid propeller, a main shaft, two bearings and an orthogonally stiffened pressure hull, is submerged in a heavy fluid. The shaft is elastically connected to the pressure hull by a radial bearing and a thrust bearing. The theoretical model of the structural system is formulated based on a modified variational method, in which the propeller, the main shaft and the bearings are treated as a lumped mass, an elastic beam and spatially distributed spring-damper systems, respectively. The rings and stringers in the pressure hull are modeled as discrete structural elements. The acoustic field generated by the hull is calculated using a spectral Kirchhoff-Helmholtz integral formulation. A strongly coupled structure-acoustic interaction analysis is employed to achieve reasonable solutions for the coupled system. The displacement of the pressure hull and the sound pressure of the fluid are expanded in the form of a double mixed series using Fourier series and Chebyshev orthogonal polynomials, providing a flexible way for the present method to account for the individual contributions of circumferential wave modes to the vibration and acoustic responses of the pressure hull in an analytical manner. The contributions of different circumferential wave modes of the pressure hull to the structural and acoustic responses of the coupled system under axial, transversal and vertical propeller forces are investigated. Computed results are compared with those solutions obtained from the coupled finite element/boundary element method. Effects of the ring and the bearing stiffness on the acoustic responses of the coupled system are discussed.

  13. Anti-M Antibody Induced Prolonged Anemia Following Hemolytic Disease of the Newborn Due to Erythropoietic Suppression in 2 Siblings.

    Science.gov (United States)

    Ishida, Atsushi; Ohto, Hitoshi; Yasuda, Hiroyasu; Negishi, Yutaka; Tsuiki, Hideki; Arakawa, Takeshi; Yagi, Yoshihito; Uchimura, Daisuke; Miyazaki, Toru; Ohashi, Wataru; Takamoto, Shigeru

    2015-08-01

    Hemolytic disease of the newborn (HDN) arising from MNSs incompatibility is rare, with few reports of prolonged anemia and reticulocytopenia following HDN. We report the younger of 2 male siblings, both of whom had anti-M-induced HDN and anemia persisting for over a month. Peripheral reticulocytes remained inappropriately low for the degree of anemia, and they needed multiple red cell transfusions. Viral infections were ruled out. Corticosteroids were given for suspected pure red cell aplasia. Anemia and reticulocytopenia subsequently improved. Colony-forming unit erythroid assay revealed erythropoietic suppression of M antigen-positive erythroid precursor cells cultured with maternal or infant sera containing anti-M. In conclusion, maternal anti-M caused HDN and prolonged anemia by erythropoietic suppression in 2 siblings.

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

    Science.gov (United States)

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

    2015-09-01

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

  15. Experimental study on active gear mesh vibration control

    Science.gov (United States)

    Guan, Yuan H.; Shepard, W. Steve, Jr.; Lim, Teik C.; Li, Mingfeng

    2004-07-01

    An internal active vibration control system is developed and verified experimentally to suppress gearbox housing vibrations due to gear transmission error excitation. The approach is based on an active shaft transverse vibration control concept. The system contains a piezoelectric stack actuator for applying control forces to the shaft via a rolling element bearing. A modified filtered-x LMS control algorithm with frequency estimation is developed to generate the appropriate control signals. The experimental results show 5-20 dB reduction in the housing vibration at the first two gear mesh harmonics over a wide gear rotation speed range. However, under certain narrow conditions, vibration amplifications at other locations are observed in the experiments, which might be attributed to the system un-modeled dynamics. In spite of this limitation, the approach developed is fairly promising. Studies are being performed to improve the overall performance of the prototype active control system.

  16. Suppressing Energy Loss due to Triplet Exciton Formation in Organic Solar Cells: The Role of Chemical Structures and Molecular Packing

    KAUST Repository

    Chen, Xiankai

    2017-04-21

    In the most efficient solar cells based on blends of a conjugated polymer (electron donor) and a fullerene derivative (electron acceptor),ultrafast formation of charge-transfer (CT) electronic states at the donor-acceptor interfaces and efficient separation of these CT states into free charges, lead to internal quantum efficiencies near 100%. However, there occur substantial energy losses due to the non-radiative recombinations of the charges, mediated by the loweset-energy (singlet and triplet) CT states; for example, such recombinations can lead to the formation of triplet excited electronic states on the polymer chains, which do not generate free charges. This issue remains a major factor limiting the power conversion efficiencies (PCE) of these devices. The recombination rates are, however, difficult to quantify experimentally. To shed light on these issues, here, an integrated multi-scale theoretical approach that combines molecular dynamics simulations with quantum chemistry calculations is employed in order to establish the relationships among chemical structures, molecular packing, and non-radiative recombination losses mediated by the lowest-energy charge-transfer states.

  17. Experimental Study on Vibration Control of a Submerged Pipeline Model by Eddy Current Tuned Mass Damper

    OpenAIRE

    Wenxi Wang; Dakota Dalton; Xugang Hua; Xiuyong Wang; Zhengqing Chen; Gangbing Song

    2017-01-01

    Undesirable vibrations occurring in undersea pipeline structures due to ocean currents may shorten the lifecycle of pipeline structures and even lead to their failure. Therefore, it is desirable to find a feasible and effective device to suppress the subsea vibration. Eddy current tuned mass damper (ECTMD), which employs the damping force generated by the relative movement of a non-magnetic conductive metal (such as copper or aluminum) through a magnetic field, is demonstrated to be an effici...

  18. Distributed Absorber for Noise and Vibration Control

    Directory of Open Access Journals (Sweden)

    Michel Azoulay

    2011-01-01

    Full Text Available An approach to a wide-band frequency passive vibration attenuation is introduced in this paper. This aims to suppress noise and vibration of extended multimode objects like plates, panels and shells. The absorber is arranged in the form of a single-layer assembly of small inertial bodies (balls being distributed and moulded within the light visco-elastic media (e.g. silicone resin. The absorber as a whole is embedded into object face covering the critical patches of the system surface. For the purpose of characterization, the authors introduced the complex frequency response function relating the volume velocity produced by the vibrating object surface (response stimulated by a point-wise force (stimulus applied to a particular point. The simulation and optimization of the main frequency characteristics has been performed using a full scale 3-dimensional Finite Element model. These revealed some new dynamic features of absorber's structures, which can contribute to vibration attenuation. A full-scale physical experimentation with synthesised absorber's structures confirmed the main results of simulation and has shown significant noise reduction over a staggering 0–20 kHz frequency band. This was achieved with a negligible weight and volume penalty due to the addition of the absorber. The results can find multiple applications in noise and vibration control of different structures. Some examples of such applications are presented.

  19. Edgewise vibration control of wind turbine blades using roller and liquid dampers

    DEFF Research Database (Denmark)

    Zhang, Zili; Nielsen, Søren R.K.

    2014-01-01

    suppressing edgewise vibrations. The roller dampers are more volumetrically efficient due to the higher mass density of the steel comparing with the liquid. On the other hand, TLCDs have their advantage that it is easier to specify the optimum damping of the damper by changing the opening ratio of the orifice......This paper deals with the passive vibration control of edgewise vibrations by means of roller dampers and tuned liquid column dampers (TLCDs). For a rotating blade, the large centrifugal acceleration makes it possible to use roller dampers or TLCDs with rather small masses for effectively...

  20. A novel technique for active vibration control, based on optimal

    Indian Academy of Sciences (India)

    In the last few decades, researchers have proposed many control techniques to suppress unwanted vibrations in a structure. In this work, a novel and simple technique is proposed for the active vibration control. In this technique, an optimal tracking control is employed to suppress vibrations in a structure by simultaneously ...

  1. Suppressed spin dephasing for two-dimensional and bulk electrons in GaAs wires due to engineered cancellation of spin-orbit interaction terms

    NARCIS (Netherlands)

    Denega, S.Z.; Last, Thorsten; Liu, J.; Slachter, A.; Rizo, P.J.; Loosdrecht, P.H.M. van; Wees, B.J. van; Reuter, D.; Wieck, A.D.; Wal, C.H. van der

    2010-01-01

    We report a study of suppressed spin dephasing for quasi-one-dimensional electron ensembles in wires etched into a GaAs/AlGaAs heterojunction system. Time-resolved Kerr-rotation measurements show a suppression that is most pronounced for wires along the [110] crystal direction. This is the

  2. Unilateral suppression of P/N13′ potential amplitude in young patients with persistent numbness due to cervical monoradiculopathy. A case-control study

    Directory of Open Access Journals (Sweden)

    Christos Moschovos

    Full Text Available Objective: The utility of Dermatomal Somatosensory Evoked Potentials (DSEPs in the diagnostic workup of suspected cervical monoradiculopathy has been limited by significant overlap between measurements obtained from affected versus unaffected roots. In a case-control study, we explored whether, under certain conditions, asymmetry in DSEP parameters may offer significant help in the diagnosis of monoradiculopathy. Methods: DSEPs were obtained bilaterally from patients with persistent (age range 33–55, n = 10 or intermittent (age range 31–55, n = 7 unilateral sensory symptoms of less than one month duration due to MRI-confirmed cervical monoradiculopathy. DSEPs were also obtained bilaterally from aged-matched asymptomatic volunteers (age range 31–54, n = 8 and older asymptomatic volunteers (age range 57–77, n = 8. Amplitude and latency of the P/N13′ potential (negative peak at 13 ms were measured. Results: In all ten patients with persistent symptoms, the P/N13′ amplitude ratio, defined as P/N13′ amplitude on the symptomatic side divided by P/N13′ amplitude on the contralateral asymptomatic side, ranged between 0.0 and 0.50 (unilateral suppression. In all seven patients with intermittent symptoms, P/N13′ amplitude ratios ranged between 0.60 and 1.00. In all age-matched asymptomatic controls, P/N13′ amplitude ratio (side with lower divided by side with higher amplitude was always at least 0.80. Among older asymptomatic subjects, DSEPs had inconsistent characteristics. Conclusions: Cervical monoradiculopathy with persistent numbness in young patients (aged up to 55 years is very strongly associated with unilateral suppression of P/N13′ DSEP amplitude. No significant asymmetry is observed in cases of monoradiculopathy with intermittent numbness. Significance: In young patients with unilateral upper extremity persistent sensory complaints, DSEP amplitude asymmetry, as quantified by the P/N13′ ratio, may offer

  3. Comparative analysis of actuator concepts for active gear pair vibration control

    Science.gov (United States)

    Guan, Yuan H.; Li, Mingfeng; Lim, Teik C.; Shepard, W. Steve

    2004-01-01

    Four actuation concepts for the active suppression of gearbox housing mesh frequency vibrations due to transmission error excitation from the gear pair system are modelled and compared by computing the required actuation forces and amplifier power spectra. The proposed designs studied consist of (1) active inertial actuators positioned tangentially on the gear body to produce a pair of reactive force and moment, (2) semi-active gear-shaft torsional coupling to provide tuned vibration isolation and suppression, (3) active bearing vibration control to reduce vibration transmissibility, and (4) active shaft transverse vibration control to suppress/tune gearbox casing or shaft response. Numerical simulations that incorporate a transmission error term as the primary excitation are performed using a finite element model of the geared rotor system (dynamic plant) constructed from beam and lumped mass/stiffness elements. Several key comparison criteria including the required actuation effort, control robustness and implementation cost are examined, and the advantages and disadvantages of each concept are discussed. Based on the simulated data, the active shaft transverse vibration control scheme is identified as the most suitable approach for this application.

  4. Vibration mixer

    Energy Technology Data Exchange (ETDEWEB)

    Alekhin, S.A.; Chernov, V.S.; Denisenko, V.V.; Gorodnyanskiy, I.F.; Prokopov, L.I.; Tikhonov, Yu.P.

    1983-01-01

    The vibration mixer is proposed which contains a housing, vibration drive with rod installed in the upper part of the mixing mechanism made in the form of a hollow shaft with blades. In order to improve intensity of mixing and dispersion of the mud, the shaft with the blades is arranged on the rod of the vibrator and is equipped with a cam coupling whose drive disc is attached to the vibration rod. The rod is made helical, while the drive disc of the cam coupling is attached to the helical surface of the rod. In addition, the vibration mixer is equipped with perforated discs installed on the ends of the rods.

  5. Zero-Annihilation Periodic Control For Damping Vibrations

    Science.gov (United States)

    Bayard, David S.; Boussalis, Dhemetrios

    1995-01-01

    Report presents study on use of recently developed zero-annihilation periodic (ZAP) controller for active suppression of vibrations in flexible structures characterized by non-minimum-phase transfer functions. Non-minimum-phase situation occurs if certain kinds of vibration-sensor/vibration-actuator pairs (e.g., piezoelectric) used, and/or if vibration sensor(s) not colocated with vibration actuator(s).

  6. Electric field dependent structural and vibrational properties of the Si(100)-H(2 x 1) surface and its implications for STM induced hydrogen desorption

    DEFF Research Database (Denmark)

    Stokbro, Kurt

    1999-01-01

    We report a first principles study of the structure and the vibrational properties of the Si(100)-H(2 x 1) surface in an electric field. The calculated vibrational parameters are used to model the vibrational modes in the presence of the electric field corresponding to a realistic scanning...... tunneling microscopy tip-surface geometry. We find that local one-phonon excitations have short lifetimes (10 ps at room temperature) due to incoherent lateral diffusion, while diffusion of local multi-phonon excitations are suppressed due to anharmonic frequency shifts and have much longer lifetimes (10 ns...... in the desorption process. (C) 1999 Elsevier Science B.V. All rights reserved....

  7. Vibration of a string against multiple spring-mass-damper stoppers

    Science.gov (United States)

    Shin, Ji-Hwan; Talib, Ezdiani; Kwak, Moon K.

    2018-02-01

    When a building sways due to strong wind or an earthquake, the elevator rope can undergo resonance, resulting in collision with the hoist-way wall. In this study, a hard stopper and a soft stopper comprised of a spring-mass-damper system installed along the hoist-way wall were considered to prevent the string from undergoing excessive vibrations. The collision of the string with multiple hard stoppers and multiple spring-mass-damper stoppers was investigated using an analytical method. The result revealed new formulas and computational algorithms that are suitable for simulating the vibration of the string against multiple stoppers. The numerical results show that the spring-mass-damper stopper is more effective in suppressing the vibrations of the string and reducing structural failure. The proposed algorithms were shown to be efficient to simulate the motion of the string against a vibration stopper.

  8. Vibration control of an elastic strip by a singular force

    Indian Academy of Sciences (India)

    J. Sound and Vibration 315: 1–21. Han J H, Tani J, Qui J 2006 Active flutter suppression of a lifting surface using piezoelectric actuation and modern control theory. J. Sound and Vibration 291: 706–722. Han J H, Lee I 1999 Optimal placement of piezoelectric sensors and actuators for vibration control of a composite plate ...

  9. Random vibrations theory and practice

    CERN Document Server

    Wirsching, Paul H; Ortiz, Keith

    1995-01-01

    Random Vibrations: Theory and Practice covers the theory and analysis of mechanical and structural systems undergoing random oscillations due to any number of phenomena— from engine noise, turbulent flow, and acoustic noise to wind, ocean waves, earthquakes, and rough pavement. For systems operating in such environments, a random vibration analysis is essential to the safety and reliability of the system. By far the most comprehensive text available on random vibrations, Random Vibrations: Theory and Practice is designed for readers who are new to the subject as well as those who are familiar with the fundamentals and wish to study a particular topic or use the text as an authoritative reference. It is divided into three major sections: fundamental background, random vibration development and applications to design, and random signal analysis. Introductory chapters cover topics in probability, statistics, and random processes that prepare the reader for the development of the theory of random vibrations a...

  10. Shifts in the Gut Microbiota Composition Due to Depleted Bone Marrow Beta Adrenergic Signaling Are Associated with Suppressed Inflammatory Transcriptional Networks in the Mouse Colon.

    Science.gov (United States)

    Yang, Tao; Ahmari, Niousha; Schmidt, Jordan T; Redler, Ty; Arocha, Rebeca; Pacholec, Kevin; Magee, Kacy L; Malphurs, Wendi; Owen, Jennifer L; Krane, Gregory A; Li, Eric; Wang, Gary P; Vickroy, Thomas W; Raizada, Mohan K; Martyniuk, Christopher J; Zubcevic, Jasenka

    2017-01-01

    The brain-gut axis plays a critical role in the regulation of different diseases, many of which are characterized by sympathetic dysregulation. However, a direct link between sympathetic dysregulation and gut dysbiosis remains to be illustrated. Bone marrow (BM)-derived immune cells continuously interact with the gut microbiota to maintain homeostasis in the host. Their function is largely dependent upon the sympathetic nervous system acting via adrenergic receptors present on the BM immune cells. In this study, we utilized a novel chimera mouse that lacks the expression of BM beta1/2 adrenergic receptors (b1/2-ARs) to investigate the role of the sympathetic drive to the BM in gut and microbiota homeostasis. Fecal analyses demonstrated a shift from a dominance of Firmicutes to Bacteroidetes phylum in the b1/2-ARs KO chimera, resulting in a reduction in Firmicutes/Bacteroidetes ratio. Meanwhile, a significant reduction in Proteobacteria phylum was determined. No changes in the abundance of acetate-, butyrate-, and lactate-producing bacteria, and colon pathology were observed in the b1/2-ARs KO chimera. Transcriptomic profiling in colon identified Killer Cell Lectin-Like Receptor Subfamily D, Member 1 (Klrd1), Membrane-Spanning 4-Domains Subfamily A Member 4A (Ms4a4b), and Casein Kinase 2 Alpha Prime Polypeptide (Csnk2a2) as main transcripts associated with the microbiota shifts in the b1/2-ARs KO chimera. Suppression of leukocyte-related transcriptome networks (i.e., function, differentiation, migration), classical compliment pathway, and networks associated with intestinal function, barrier integrity, and excretion was also observed in the colon of the KO chimera. Moreover, reduced expression of transcriptional networks related to intestinal diseases (i.e., ileitis, enteritis, inflammatory lesions, and stress) was noted. The observed suppressed transcriptome networks were associated with a reduction in NK cells, macrophages, and CD4 + T cells in the b1/2-ARs KO

  11. Pressure suppression device

    International Nuclear Information System (INIS)

    Mizumachi, Wataru; Fukuda, Akira; Kitaguchi, Hidemi; Shimizu, Toshiaki.

    1976-01-01

    Object: To relieve and absorb impact wave vibrations caused by steam and non-condensed gases releasing into the pressure suppression chamber at the time of an accident. Structure: The reactor container is filled with inert gases. A safety valve attached main steam pipe is provided to permit the excessive steam to escape, the valve being communicated with the pressure suppression chamber through an exhaust pipe. In the pressure suppression chamber, a doughnut-like cylindrical outer wall is filled at its bottom with pool water to condense the high temperature vapor released through the exhaust pipe. A head portion of a vent tube which leads the exhaust pipe is positioned at the top, and a down comer and an exhaust vent tube are locked by means of steady rests. At the bottom is mounted a pressure adsorber device which adsorbs a pressure from the pool water. (Kamimura, M.)

  12. Cushing's syndrome with adrenal suppression induced by inhaled budesonide due to a ritonavir drug interaction in a woman with HIV infection.

    Science.gov (United States)

    Yoganathan, K; David, L; Williams, C; Jones, K

    2012-07-01

    A 48-year-old woman with HIV infection developed Cushingoid features while she was taking ritonavir-boosted darunavir. Cushing's syndrome was confirmed due to the drug interaction between ritonavir and budesonide. Diagnosis of iatrogenic Cushing's syndrome in HIV-positive patients who are on ritonavir-boosted protease inhibitors (PIs) presents a clinical challenge due to similar clinical features of lipohypertrophy related to ritonavir-boosted PIs. Although this complication has been widely described with the use of inhaled fluticasone, the interaction with inhaled budesonide at therapeutic dose is not widely recognized.

  13. Vibrating minds

    CERN Multimedia

    2009-01-01

    Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.

  14. Vibrational spectroscopy

    Science.gov (United States)

    Umesh P. Agarwal; Rajai Atalla

    2010-01-01

    Vibrational spectroscopy is an important tool in modern chemistry. In the past two decades, thanks to significant improvements in instrumentation and the development of new interpretive tools, it has become increasingly important for studies of lignin. This chapter presents the three important instrumental methods-Raman spectroscopy, infrared (IR) spectroscopy, and...

  15. Active Vibration Control of a Flexible Structure Using Piezoceramic Actuators

    Directory of Open Access Journals (Sweden)

    J. Fei

    2008-03-01

    Full Text Available Considerable attention has been devoted recently to active vibration control using intelligent materials as actuators. This paper presents results on active control schemes for vibration suppression of flexible steel cantilever beam with bonded piezoelectric actuators. The PZT patches are surface bonded near the fixed end of flexible steel cantilever beam. The dynamic model of the flexible steel cantilever beam is derived. Active vibration control methods, strain rate feedback control (SRF, positive position feedback control (PPF are investigated and implemented using xPC Target real-time system. Experimental results demonstrate that the SRF control and PPF control achieve effective vibration suppression results of steel cantilever beam.

  16. Detection and suppression for mechanical resonance in hard disk drives with built-in piezoelectric sensors

    Science.gov (United States)

    Gao, Peng; Lou, Yaolong; Okada, Kanzo

    2002-07-01

    Many components in hard disk drives (HDDs), when in operation, are subjected to vibration due to out of balance of rotating components, inertial impacts under servo driving and dynamic interactions between components. These vibrations have been found to have significant effect upon the servo performance of drive systems. In order to improve the servo performance by reducing the effect of mechanical resonance in HDDs, this paper seeks to detect and suppress mechanical resonance of the head actuator using smart sensors and multi-sensing control techniques. In this regard, sensitive and miniature piezoelectric elements from the polymer-based piezoelectric materials PVDF (polyvinylindin fluoride) or the ceramic-based piezoelectric materials PZT 9lead zircornate titanate) are built in the head actuator for sensing the mechanical vibration. In the experiment, the multi-sensing signals by the piezoelectric sensors and the laser Doppler vibrometer (LDV) are transferred into a voice coil motor (VCM) through a feedback controller so as to actively suppress structural resonance. Numerical simulation and experimental results indicate that the piezoelectric sensors provide an effective way in monitoring the HDD actuator resonance, and the active vibration control strategy is capable of suppressing main mechanical resonance in the head actuator effectively.

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

    Science.gov (United States)

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

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

  18. Vibrational spectroscopy

    International Nuclear Information System (INIS)

    Fadini, A.

    1980-01-01

    We present 13 programs for the calculation of vibrational spectroscopic problems applied to small molecules with high symmetry. The programs are compiled for the well known programmable pocket calculator Texas Instruments SR-52. To the special problems, the mathematical formulas, input and output instructions, several numerical examples, literature and the programs with comments are given. Order n = 1: The force constants, isotopic vibrational frequencies and the vibrational amplitudes are calculated for the two mass system XY(Csub(infinitely v)). For the three mass system XY 2 (Dsub(infinitely h)) only the force constants and isotopic frequencies are calculated. Order n = 2: For the three mass systems XYZ(Csub(infinitely v)) and XY 2 (Csub(infinitely 2v)) the inverse matrices G of the kinetic energy are presented. For complete sets of data (with isotopic frequencies, Coriolis coupling constants etc.) the complete force constant matrices are calculated. For non complete sets of data one starts in most cases with diagonal force constant matrices. The complete force constant matrix F is calculated with a minimalisation approximation. The eigenvector matrices L result from the G - F - and N-matrices. The N-matrices are calculated from the G- and F-matrices or from the F- and L-matrices respectively. Order n = 3: The matrix G of the system XYZ(Csub(S)) is calculated. For higher orders n, the 'isotopic reduction method' for the calculation of single force constants of proper systems is described. (orig.) [de

  19. Pressure suppression device

    International Nuclear Information System (INIS)

    Ichiki, Tadaharu; Funahashi, Toshihiro.

    1976-01-01

    Purpose: To provide a structure which permits the absorption of shocks and vibratory load produced on the floor of a pressure suppression chamber due to nitrogen gas or the like discharged into pool water in the pressure suppression chamber at the time of a loss-of-coolant accident. Constitution: A pressure suppression chamber accommodating pool water is comprised of a bottom wall and side walls constructed of concrete on the inner side of a liner. By providing concrete on the bottom surface and side wall surfaces of a pressure suppression chamber, it is possible to prevent non-condensing gas and steam exhausted from the vent duct and exhaust duct of a main vapor escapement safety valve exhaust duct from exerting impact forces and vibratory forces upon the bottom and side surfaces of the pressure suppression chamber. (Horiuchi, T.)

  20. Study on Active Suppression Control of Drivetrain Oscillations in an Electric Vehicle

    Science.gov (United States)

    Huang, Lei; Cui, Ying

    2017-07-01

    Due to the low damping in a central driven electric vehicle and lack of passive damping mechanisms as compared with a conventional vehicle, the vehicle may endure torsional vibrations which may deteriorates the vehicle’s drivability. Thus active damping control strategy is required to reduce the undesirable oscillations in an EV. In this paper, the origin of the vibration and the design of a damping control method to suppress such oscillations to improve the drivability of an EV are studied. The traction motor torque that is given by the vehicle controller is adjusted according to the acceleration rate of the motor speed to attenuate the resonant frequency. Simulations and experiments are performed to validate the system. The results show that the proposed control system can effectively suppress oscillations and hence improve drivability.

  1. Urban vibrations

    DEFF Research Database (Denmark)

    Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen

    2012-01-01

      lab   studies   in   that   we   found   a   decreased   detection   rate   in   busy   environments.   Here   we   test   with   a   much   larger   sample   and   age   range,   and   contribute   with   the   first   vibration  sensitivity  testing  outside  the  lab  in  an  urban   public...

  2. Introduction of building vibration observation data of metropolitan area due to the 2011 off the Pacific coast of Tohoku Earthquake: an Approach of the IT Kyoshin Seismometer for Buildings

    Science.gov (United States)

    Takano, K.; Ito, T.

    2011-12-01

    In the 2011 off the Pacific coast of Tohoku Earthquake, many buildings were vibrated greatly also in the Tokyo metropolitan area where is far left from the hypocenter. We have developed the IT Kyoshin(strong motion) Seismometer for Building which is the observation system of the usual weak earthquake ground motion by installing a lot of acceleration sensors in building, and have been setting it up in some buildings of the University of Tokyo. By this February, we have set up IT Kyoshin Seismometers newly in four buildings of the two remote campus of the University of Tokyo. And we have opend to the public of these observed data. In this building vibration observation system, we can get a lot of building vibration observation data of the Pacific coast of Tohoku Earthquake. We have made the building shaking to visible from the observation data of each building and the appearance of the shake of each building is shown plainly. Moreover, we can see how the vibration property in the usual building is changed by the large shaking. This analysis of the observation data of the building vibration at the earthquake is useful for the detection of the damaged part in the building by the earthquake and for the reinforcement measures in the weak buildings.

  3. Role of vibrational dynamics in resonant positron annihilation on molecules.

    Science.gov (United States)

    Jones, A C L; Danielson, J R; Natisin, M R; Surko, C M

    2013-05-31

    Vibrational Feshbach resonances are dominant features of positron annihilation for incident positron energies in the range of the molecular vibrations. Studies in relatively small molecules are described that elucidate the role of intramolecular vibrational energy redistribution into near-resonant multimode states, and the subsequent coupling of these modes to the positron continuum, in suppressing or enhancing these resonances. The implications for annihilation in other molecular species, and the necessary ingredients of a more complete theory of resonant positron annihilation, are discussed.

  4. Wireless sensing and vibration control with increased redundancy and robustness design.

    Science.gov (United States)

    Li, Peng; Li, Luyu; Song, Gangbing; Yu, Yan

    2014-11-01

    Control systems with long distance sensor and actuator wiring have the problem of high system cost and increased sensor noise. Wireless sensor network (WSN)-based control systems are an alternative solution involving lower setup and maintenance costs and reduced sensor noise. However, WSN-based control systems also encounter problems such as possible data loss, irregular sampling periods (due to the uncertainty of the wireless channel), and the possibility of sensor breakdown (due to the increased complexity of the overall control system). In this paper, a wireless microcontroller-based control system is designed and implemented to wirelessly perform vibration control. The wireless microcontroller-based system is quite different from regular control systems due to its limited speed and computational power. Hardware, software, and control algorithm design are described in detail to demonstrate this prototype. Model and system state compensation is used in the wireless control system to solve the problems of data loss and sensor breakdown. A positive position feedback controller is used as the control law for the task of active vibration suppression. Both wired and wireless controllers are implemented. The results show that the WSN-based control system can be successfully used to suppress the vibration and produces resilient results in the presence of sensor failure.

  5. Suppressed Belief

    Directory of Open Access Journals (Sweden)

    Komarine Romdenh-Romluc

    2009-12-01

    Full Text Available Moran’s revised conception of conscious belief requires us to reconceptualise suppressed belief. The work of Merleau-Ponty offers a way to do this. His account of motor-skills allows us to understand suppressed beliefs as pre-reflective ways of dealing with the world.

  6. Effects of topology versus disorder on the vibrational properties of amorphous semiconductors

    International Nuclear Information System (INIS)

    Sen, P.N.; Yndurain, F.

    1977-01-01

    We propose a method to isolate the effects of topology, present in the form of rings, etc., from those of disorder due to bond-angle variation. For a representative cluster based on the Polk model, we find that the effects of disorder dominate over those due to rings. The so-called LA-LO peaks in the local vibrational density of states appear only if more than six sixfold rings pass through the atom. These are suppressed if the angular disorder exceeds a critical value

  7. Hot Ground Vibration Tests

    Data.gov (United States)

    National Aeronautics and Space Administration — Ground vibration tests or modal surveys are routinely conducted to support flutter analysis for subsonic and supersonic vehicles. However, vibration testing...

  8. Self-Excited Vibration Analysis for the Feed Support System in FAST

    Directory of Open Access Journals (Sweden)

    Xiaoqiang Tang

    2014-04-01

    Full Text Available China is currently building the largest single dish radio telescope in the world, which is called the Five-hundred meter Aperture Spherical radio Telescope (FAST. The feed support system in the FAST is composed of a cable-driven parallel manipulator, an A-B rotator, and a Stewart platform. Since the stiffness of the cable-driven parallel manipulator is low, the feed support system is prone to vibrate under the action of the Stewart platform. The main purpose of this paper is to study the self-excited vibration of the feed support system. Self-excited vibration involves the natural frequencies of the system and the resultant forces produced by the motion of the Stewart platform. This paper linearizes the dynamic equations of the system at an operating point and determines the configuration-dependent natural frequencies in the given workspace. This paper obtains the resultant forces from the legs due to the motion of the Stewart platform by using the numerical method. According to the natural frequencies and the resultant forces, the condition of self-excited vibration is given and verified by simulations. In order to verify the linearization method, an experimental platform of a cable-driven parallel manipulator is set up. The experimental results match well with the theoretical arithmetic. This paper provides a reference point for further studies on vibration suppression in the FAST.

  9. Control aid for xenon vibration in reactor

    International Nuclear Information System (INIS)

    Kanekawa, Takashi.

    1990-01-01

    In the present invention, the control operation for suppressing xenon vibrations in a reactor is aided for saving forecasting analysis and operator's skills. That is, parameters to be controlled for the suppression of xenon vibrations are power distribution, iodine distribution and xenon distribution. But what can be observed by operaters by the conventional fast overtone method is only the output distribution. In the present invention, the output level of the reactor core is always observed. Then, mathematical processings are conducted for the iodine distribution, the xenon distribution and the power distribution in the reactor core based on the histeresis of the parameters obtained by the measurement using physical constants and reactor design data. The xenon vibration control is aided by displaying the change with time of the distortion in axial direction. Accordingly, operators can always recognize the axial distortion of the power distribution, the iodine distribution and the xenon distribution. (I.S.)

  10. Human response to vibration in residential environments.

    Science.gov (United States)

    Waddington, David C; Woodcock, James; Peris, Eulalia; Condie, Jenna; Sica, Gennaro; Moorhouse, Andrew T; Steele, Andy

    2014-01-01

    This paper presents the main findings of a field survey conducted in the United Kingdom into the human response to vibration in residential environments. The main aim of this study was to derive exposure-response relationships for annoyance due to vibration from environmental sources. The sources of vibration considered in this paper are railway and construction activity. Annoyance data were collected using questionnaires conducted face-to-face with residents in their own homes. Questionnaires were completed with residents exposed to railway induced vibration (N = 931) and vibration from the construction of a light rail system (N = 350). Measurements of vibration were conducted at internal and external positions from which estimates of 24-h vibration exposure were derived for 1073 of the case studies. Sixty different vibration exposure descriptors along with 6 different frequency weightings were assessed as potential predictors of annoyance. Of the exposure descriptors considered, none were found to be a better predictor of annoyance than any other. However, use of relevant frequency weightings was found to improve correlation between vibration exposure and annoyance. A unified exposure-response relationship could not be derived due to differences in response to the two sources so separate relationships are presented for each source.

  11. The modelling of industrial robot manipulator vibration

    Energy Technology Data Exchange (ETDEWEB)

    Marcham, L.J.; Rao, B.K.N.; Noroozi, S.; Penson, R.P. [Southampton Inst. (United Kingdom). Systems Engineering Research Centre

    1996-11-01

    The work reported in this paper addresses the modelling of robot manipulator vibration, with the specific aim of producing a model suitable to be employed within an active compensation controller. An overview of existing work on the modelling of robot dynamics, both mathematically and empirically, is reported. A model of the dynamics of an industrial manipulator, inclusive of vibration, derived using Lagrangian mechanics is presented and further developed through the application of experimental modal analysis, by which the position dependent modal parameters of an industrial robot manipulator are determined. The model results are compared with experimental vibration data taken from the end-effector of a PUMA562C industrial manipulator using laser interferometry. Control of an end-effector located, active compensator for vibration suppression, based upon the derived model is discussed and recommendations which form the basis of further investigations, currently being undertaken, are presented.

  12. Numerical analysis using state space method for vibration control of ...

    African Journals Online (AJOL)

    In passenger cars the vibrations developed at the ground are transmitted to the passengers through seats. Due to vibrations discomfort is experienced by the passengers. Dampers are being successfully utilized to reduce the vibrations in civil engineering structures. Few dampers are used in passenger cars as well.

  13. High cycle fatigue analysis of vortex suppression plate and secondary core support structures

    International Nuclear Information System (INIS)

    Xue Guohong; Li Yuan; Zhao Feiyun; Feng Shaodong; Yu Hao

    2013-01-01

    Background: Reactor internals are important equipment s in the reactor coolant system, its structure design needs high reliability in the entire lifetime, Reactor internals have occurred breakdown and the damage event due to flow induced vibrations in the domestic and foreign nuclear power plants, which make immediate influence on reactor safe operation and economic efficiency. Purpose: In this work, the dynamic response of reactor internals-vortex suppression plate and secondary core support structure (SCSS) under the loading from pump induced vibrations and flow induced vibrations are studied. Methods: Based on the finite element model of SCSS, Spectrum analysis and the harmonious analysis are performed, in order to get the response of the structure under flow induced vibrations. Then, the high fatigue of the structure is assessed according to the ASME B and PV Code. Results: The results indicate that alternate stresses of all the components satisfy the limiting value in the correlative requirements. Conclusions: The structure of SCSS could bear the vibration induced from the flow and the pump, and the method used in this article provides the reference for other reactor internals structure analysis like this. (authors)

  14. Adaptive photodetectors for vibration monitoring

    International Nuclear Information System (INIS)

    Sokolov, I.A.

    2003-01-01

    We present characteristics of laser vibrometer using semiconductor GaAs and molecular SnS 2 adaptive photodetectors (AP) based on the effect of the non-steady-state photoelectromotive force. AP enable efficient direct conversion of high-frequency phase modulation of speckle-like optical wave reflected from the vibrating object into an output electrical signal with concomitant setting of optimal operation point of the interferometer and suppression of amplitude laser noise. The sensitivity of the setup is analyzed and further improvements in operation of AP are discussed

  15. Influence of stellar multiplicity on planet formation. I. Evidence of suppressed planet formation due to stellar companions within 20 au and validation of four planets from the Kepler multiple planet candidates

    International Nuclear Information System (INIS)

    Wang, Ji; Fischer, Debra A.; Xie, Ji-Wei; Barclay, Thomas

    2014-01-01

    The planet occurrence rate for multiple stars is important in two aspects. First, almost half of stellar systems in the solar neighborhood are multiple systems. Second, the comparison of the planet occurrence rate for multiple stars to that for single stars sheds light on the influence of stellar multiplicity on planet formation and evolution. We developed a method of distinguishing planet occurrence rates for single and multiple stars. From a sample of 138 bright (K P < 13.5) Kepler multi-planet candidate systems, we compared the stellar multiplicity rate of these planet host stars to that of field stars. Using dynamical stability analyses and archival Doppler measurements, we find that the stellar multiplicity rate of planet host stars is significantly lower than field stars for semimajor axes less than 20 AU, suggesting that planet formation and evolution are suppressed by the presence of a close-in companion star at these separations. The influence of stellar multiplicity at larger separations is uncertain because of search incompleteness due to a limited Doppler observation time baseline and a lack of high-resolution imaging observation. We calculated the planet confidence for the sample of multi-planet candidates and find that the planet confidences for KOI 82.01, KOI 115.01, KOI 282.01, and KOI 1781.02 are higher than 99.7% and thus validate the planetary nature of these four planet candidates. This sample of bright Kepler multi-planet candidates with refined stellar and orbital parameters, planet confidence estimation, and nearby stellar companion identification offers a well-characterized sample for future theoretical and observational study.

  16. Immune response gene control of collagen reactivity in man: collagen unresponsiveness in HLA-DR4 negative nonresponders is due to the presence of T-dependent suppressive influences

    International Nuclear Information System (INIS)

    Solinger, A.M.; Stobo, J.D.

    1982-01-01

    To determine whether the failure to detect collagen reactivity in nonresponders represents an absence of collagen-reactive T cells or a preponderance of suppressive influences, the peripheral blood mononuclear cells from HLA-DR4 - individuals were subjected to three procedures capable of separating suppressive influences from LIF-secreting cells; irradiation (1000 rad), discontinuous gradient fractionation, and cytolysis with the monoclonal antibody OKT 8. Each procedure resulted in the specific appearance of reactivity to collagen, which was identical to that seen in HLA-DR4 + individuals with regard to its cellular requirements and antigenic specificity. Addition of unresponsive (i.e., nonirradiated or low-density T cells) to responsive (i.e., irradiated or high-density T cells) autologous populations resulted in specific suppression of collagen reactivity. Radiation-sensitive suppressive influences could not be detected in HLA-DR4 + collagen responders.These studies indicate that the expression of T-dependent reactivity to collagen in man reflects the net influence of collage-reactive vs collagen-suppressive T cells. Moreover, it is the influence of HLA-D-linked genes on the development of suppressive influences rather than on the development of collagen-reactive, LIF-secreting T cells that serves to distinguish HLA-DR4 + collagen responders from HLA-DR4 - collagen nonresponders

  17. Vibration analysis and vibration damage assessment in nuclear and process equipment

    International Nuclear Information System (INIS)

    Pettigrew, M.J.; Taylor, C.E.; Fisher, N.J.; Yetisir, M.; Smith, B.A.W.

    1997-01-01

    Component failures due to excessive flow-induced vibration are still affecting the performance and reliability of process and nuclear components. The purpose of this paper is to discuss flow-induced vibration analysis and vibration damage prediction. Vibration excitation mechanisms are described with particular emphasis on fluid elastic instability. The dynamic characteristics of process and power equipment are explained. The statistical nature of some parameters, in particular support conditions, is discussed. The prediction of fretting-wear damage is approached from several points-of-view. An energy approach to formulate fretting-wear damage is proposed. (author)

  18. Suppression chamber

    International Nuclear Information System (INIS)

    Goto, Hiroshi; Tsuji, Akio.

    1976-01-01

    Purpose: To miniaturize the storage tank of condensated water in BWR reactor. Constitution: A diaphragm is provided in a suppression chamber thereby to partition the same into an inner compartment and an outer compartment. In one of said compartments there is stored clean water to be used for feeding at the time of separating the reactor and for the core spray system, and in another compartment there is stored water necessary for accomplishing the depressurization effect at the time of coolant loss accident. To the compartment in which clean water is stored there is connected a water cleaning device for constantly maintaining water in clean state. As this cleaning device an already used fuel pool cleaning device can be utilized. Further, downcomers for accomplishing the depressurization function are provided in both inner compartment and outer compartment. The capacity of the storage tank can be reduced by the capacity of clean water within the suppression chamber. (Ikeda, J.)

  19. Vibrational Cooling in A Cold Ion Trap: Vibrationally Resolved Photoelectron Spectroscopy of Cold C60- Anions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xue B.; Woo, Hin-koon; Wang, Lai S.

    2005-08-01

    We demonstrate vibrational cooling of anions via collisions with a background gas in an ion trap attached to a cryogenically controlled cold head (10 ? 400 K). Photoelectron spectra of vibrationally cold C60- anions, produced by electrospray ionization and cooled in the cold ion trap, have been obtained. Relative to spectra taken at room temperature, vibrational hot bands are completely eliminated, yielding well resolved vibrational structures and a more accurate electron affinity for neutral C60. The electron affinity of C60 is measured to be 2.683 ? 0.008 eV. The cold spectra reveal complicated vibrational structures for the transition to the C60 ground state due to the Jahn-Teller effect in the ground state of C60-. Vibrational excitations in the two Ag modes and eight Hg modes are observed, providing ideal data to assess the vibronic couplings in C60-.

  20. Vibrations and Stability

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    About this textbook An ideal text for students that ties together classical and modern topics of advanced vibration analysis in an interesting and lucid manner. It provides students with a background in elementary vibrations with the tools necessary for understanding and analyzing more complex...... dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... and physics. This edition includes a new chapter on the useful effects of fast vibrations and many new exercise problems. Written for: Students in mechanical or structural engineering. Keywords: Nonlinear Vibrations, Bifurcations, Chaotic Vibrations, Vibrations and Stability....

  1. Human response to vibration

    National Research Council Canada - National Science Library

    Mansfield, Neil J

    2005-01-01

    .... Vibration measurements and standards are also addressed. This book meets the needs of those requiring knowledge of human response to vibration in order to make practical improvements to physical working environments...

  2. Vibrations and Stability

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    dynamical phenomena that can be encountered in engineering and scientific practice. It progresses steadily from linear vibration theory over various levels of nonlinearity to bifurcation analysis, global dynamics and chaotic vibrations. It trains the student to analyze simple models, recognize nonlinear...... and physics. This edition includes a new chapter on the useful effects of fast vibrations and many new exercise problems. Written for: Students in mechanical or structural engineering. Keywords: Nonlinear Vibrations, Bifurcations, Chaotic Vibrations, Vibrations and Stability.......About this textbook An ideal text for students that ties together classical and modern topics of advanced vibration analysis in an interesting and lucid manner. It provides students with a background in elementary vibrations with the tools necessary for understanding and analyzing more complex...

  3. Simultaneous Structural Health Monitoring and Vibration Control of Adaptive Structures Using Smart Materials

    Directory of Open Access Journals (Sweden)

    Myung-Hyun Kim

    2002-01-01

    Full Text Available The integration of actuators and sensors using smart materials enabled various applications including health monitoring and structural vibration control. In this study, a robust control technique is designed and implemented in order to reduce vibration of an active structure. Special attention is given to eliminating the possibility of interaction between the health monitoring system and the control system. Exploiting the disturbance decoupling characteristic of the sliding mode observer, it is demonstrated that the proposed observer can eliminate the possible high frequency excitation from the health monitoring system. At the same time, a damage identification scheme, which tracks the changes of mechanical impedance due to the presence of damage, has been applied to assess the health condition of structures. The main objective of this paper is to examine the potential of combining the two emerging techniques together. Using the collocated piezoelectric sensors/actuators for vibration suppression as well as for health monitoring, this technique enabled to reduce the number of system components, while enhancing the performance of structures. As an initial study, both simulation and experimental investigations were performed for an active beam structure. The results show that this integrated technique can provide substantial vibration reductions, while detecting damage on the structure at the same time.

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

    Science.gov (United States)

    Azevedo, Anthony W; Wilson, Rachel I

    2017-10-11

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

  5. Vibration of plates

    CERN Document Server

    Chakraverty, Snehashish

    2008-01-01

    Plates are integral parts of most engineering structures and their vibration analysis is required for safe design. This work provides a comprehensive introduction to vibration theory and analysis of two-dimensional plates. It offers information on vibration problems along with a discussion of various plate geometries and boundary conditions.

  6. Vibrations and Eigenvalues

    Indian Academy of Sciences (India)

    We make music by causing strings, membranes, or air columns to vibrate. Engineers design safe structures by control- ling vibrations. I will describe to you a very simple vibrating system and the mathematics needed to analyse it. The ideas were born in the work of Joseph-Louis Lagrange (1736–1813), and I begin by quot-.

  7. Composite multi-modal vibration control for a stiffened plate using non-collocated acceleration sensor and piezoelectric actuator

    International Nuclear Information System (INIS)

    Li, Shengquan; Li, Juan; Mo, Yueping; Zhao, Rong

    2014-01-01

    A novel active method for multi-mode vibration control of an all-clamped stiffened plate (ACSP) is proposed in this paper, using the extended-state-observer (ESO) approach based on non-collocated acceleration sensors and piezoelectric actuators. Considering the estimated capacity of ESO for system state variables, output superposition and control coupling of other modes, external excitation, and model uncertainties simultaneously, a composite control method, i.e., the ESO based vibration control scheme, is employed to ensure the lumped disturbances and uncertainty rejection of the closed-loop system. The phenomenon of phase hysteresis and time delay, caused by non-collocated sensor/actuator pairs, degrades the performance of the control system, even inducing instability. To solve this problem, a simple proportional differential (PD) controller and acceleration feed-forward with an output predictor design produce the control law for each vibration mode. The modal frequencies, phase hysteresis loops and phase lag values due to non-collocated placement of the acceleration sensor and piezoelectric patch actuator are experimentally obtained, and the phase lag is compensated by using the Smith Predictor technology. In order to improve the vibration control performance, the chaos optimization method based on logistic mapping is employed to auto-tune the parameters of the feedback channel. The experimental control system for the ACSP is tested using the dSPACE real-time simulation platform. Experimental results demonstrate that the proposed composite active control algorithm is an effective approach for suppressing multi-modal vibrations. (paper)

  8. Anti-vibration gloves?

    Science.gov (United States)

    Hewitt, Sue; Dong, Ren G; Welcome, Daniel E; McDowell, Thomas W

    2015-03-01

    For exposure to hand-transmitted vibration (HTV), personal protective equipment is sold in the form of anti-vibration (AV) gloves, but it remains unclear how much these gloves actually reduce vibration exposure or prevent the development of hand-arm vibration syndrome in the workplace. This commentary describes some of the issues that surround the classification of AV gloves, the assessment of their effectiveness and their applicability in the workplace. The available information shows that AV gloves are unreliable as devices for controlling HTV exposures. Other means of vibration control, such as using alternative production techniques, low-vibration machinery, routine preventative maintenance regimes, and controlling exposure durations are far more likely to deliver effective vibration reductions and should be implemented. Furthermore, AV gloves may introduce some adverse effects such as increasing grip force and reducing manual dexterity. Therefore, one should balance the benefits of AV gloves and their potential adverse effects if their use is considered. © Crown copyright 2014.

  9. Vibration of hydraulic machinery

    CERN Document Server

    Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong

    2013-01-01

    Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...

  10. Robust non-fragile dynamic vibration absorbers with uncertain factors

    Science.gov (United States)

    Zhang, Hui; Shi, Yang; Saadat Mehr, Aryan

    2011-02-01

    In this paper, the design problem for non-fragile dynamic vibration absorbers (DVAs) is investigated. Due to the imprecision of the manufacturing process or the variation during the operation, uncertainty in the parameters of the DVA is unavoidable. The uncertainty may degrade the performance of the designed DVA or even deteriorate the system. Hence, it is practically demanding to propose a design method for a non-fragile DVA, i.e., when the parameters of the DVA vary in an admissible range, an expected vibration suppression level should be guaranteed. The uncertainty of the DVA is feasibly assumed to be norm-bounded. Then, the design problem for the DVA is converted into a static output feedback (SOF) control problem. Sufficient condition for the existence of the non-fragile DVA with a prescribed H∞ level is derived by using a bilinear matrix inequality (BMI). An iterative linear matrix inequality (ILMI) method is employed to solve the BMI condition. Finally, a design example is given to show the effectiveness of the proposed approach.

  11. Ultrasonic technique for imaging tissue vibrations: preliminary results.

    Science.gov (United States)

    Sikdar, Siddhartha; Beach, Kirk W; Vaezy, Shahram; Kim, Yongmin

    2005-02-01

    We propose an ultrasound (US)-based technique for imaging vibrations in the blood vessel walls and surrounding tissue caused by eddies produced during flow through narrowed or punctured arteries. Our approach is to utilize the clutter signal, normally suppressed in conventional color flow imaging, to detect and characterize local tissue vibrations. We demonstrate the feasibility of visualizing the origin and extent of vibrations relative to the underlying anatomy and blood flow in real-time and their quantitative assessment, including measurements of the amplitude, frequency and spatial distribution. We present two signal-processing algorithms, one based on phase decomposition and the other based on spectral estimation using eigen decomposition for isolating vibrations from clutter, blood flow and noise using an ensemble of US echoes. In simulation studies, the computationally efficient phase-decomposition method achieved 96% sensitivity and 98% specificity for vibration detection and was robust to broadband vibrations. Somewhat higher sensitivity (98%) and specificity (99%) could be achieved using the more computationally intensive eigen decomposition-based algorithm. Vibration amplitudes as low as 1 mum were measured accurately in phantom experiments. Real-time tissue vibration imaging at typical color-flow frame rates was implemented on a software-programmable US system. Vibrations were studied in vivo in a stenosed femoral bypass vein graft in a human subject and in a punctured femoral artery and incised spleen in an animal model.

  12. Rotor Mass Eccentricity Vibration Compensation Control in Bearingless Induction Motor

    Directory of Open Access Journals (Sweden)

    Zebin Yang

    2015-01-01

    Full Text Available In the process of motor rotation, the vibration caused by the rotor mass eccentricity seriously affects the dynamic characteristics and safety operation of system. So rotor mass eccentricity vibration compensation control on rotating machine has great significance, especially for the high speed bearing less induction motor (BIM. A rotor mass eccentricity compensation control strategy was presented to restrain the vibration of suspended rotor for BIM. Firstly, the suspension rotor dynamical model was deduced and unbalanced vibration mechanism was analyzed. Secondly, based on decoupling control between electromagnetic torque and radial force, the obtained vibration signal from the displacement sensor was put into the original radial force control system. Then, a feedforward compensator was set up to increase the same period component of the given radial force signal and enlarge the stiffness of the vibration signal. Finally, the compensation control of rotor vibration was realized by forcing the rotor shaft rotation around its geometric center. The simulation results show that the presented feedforward compensator can suppress the vibration of rotor under different speed and improve the precision of rotor suspension. The further experimental results also show that the control method can obviously reduce the peak-peak value of rotor radial displacement and effectively restrain rotor vibration.

  13. Feedback damping of a microcantilever at room temperature to the minimum vibration amplitude limited by the noise level.

    Science.gov (United States)

    Kawamura, Y; Kanegae, R

    2016-06-17

    Cooling the vibration amplitude of a microcantilever as low as possible is important to improve the sensitivity and resolutions of various types of scanning type microscopes and sensors making use of it. When the vibration amplitude is controlled to be smaller using a feed back control system, it is known that the obtainable minimum amplitude of the vibration is limited by the floor noise level of the detection system. In this study, we demonstrated that the amplitude of the thermal vibration of a microcantilever was suppressed to be about 0.15 pmHz(-1/2), which is the same value with the floor noise level, without the assistance of external cryogenic cooling. We think that one of the reason why we could reach the smaller amplitude at room temperature is due to stiffer spring constant of the lever, which leads to higher natural frequency and consequently lower floor noise level. The other reason is considered to be due to the increase in the laser power for the diagnostics, which lead to the decrease in the signal to noise ratio determined by the optical shot noise.

  14. Vibration reduction for commercial optical intersatellite communication links

    Science.gov (United States)

    Hyde, T. Tupper; Davis, L. Porter

    1998-07-01

    The increasing demand for global communications and limitations on RF communication bandwidth has driven several corporations to baseline optical intersatellite communication links in their constellations. The use of laser communications over a long distance dictates the need for accurate pointing and jitter suppression in order to maintain signal. Vibrations on a satellite cause excessive line-of-sight jitter for optical performance. The solution to these vibration sources is a systems problem involving optical control of coarse and fine steering, vibration isolation of the optical payload, or reduction of the spacecraft disturbances. This paper explains the basics of tracking control of a laser communication package and details the systems trades for vibration isolation. Simulation results based on a vibration isolation and precision pointing of a hypothetical commercial LEO to LEO 4 Gbit/sec laser cross-link system are presented.

  15. Nonlinear vibration with control for flexible and adaptive structures

    CERN Document Server

    Wagg, David

    2015-01-01

    This book provides a comprehensive discussion of nonlinear multi-modal structural vibration problems, and shows how vibration suppression can be applied to such systems by considering a sample set of relevant control techniques. It covers the basic principles of nonlinear vibrations that occur in flexible and/or adaptive structures, with an emphasis on engineering analysis and relevant control techniques. Understanding nonlinear vibrations is becoming increasingly important in a range of engineering applications, particularly in the design of flexible structures such as aircraft, satellites, bridges, and sports stadia. There is an increasing trend towards lighter structures, with increased slenderness, often made of new composite materials and requiring some form of deployment and/or active vibration control. There are also applications in the areas of robotics, mechatronics, micro electrical mechanical systems, non-destructive testing and related disciplines such as structural health monitoring. Two broader ...

  16. Vibration control for precision manufacturing at Sandia National Laboratories

    International Nuclear Information System (INIS)

    Hinnerichs, T.; Martinez, D.

    1995-01-01

    Sandia National Laboratories performs R and D in structural dynamics and vibration suppression for precision applications in weapon systems, space, underwater, transportation and civil structures. Over the last decade these efforts have expanded into the areas of active vibration control and ''smart'' structures and material systems. In addition, Sandia has focused major resources towards technology to support weapon product development and agile manufacturing capability for defense and industrial applications. This paper will briefly describe the structural dynamics modeling and verification process currently in place at Sandia that supports vibration control and some specific applications of these techniques to manufacturing in the areas of lithography, machine tools and flexible robotics

  17. Smart Sensor for Analyzing Train Vibration in WCR Zone

    Directory of Open Access Journals (Sweden)

    Alka DUBEY

    2009-09-01

    Full Text Available In the present paper a smart vibration sensor is developed for railway electric engine WAP-7. Which is a self-sensation device equipped with recording and wireless communication interface. One programmed microcontroller 89C52 is used, which record vibration of trains with real time into memory. There is certain limit of vibrations, which is acceptable by track. Beyond this limit track can be damaged and may result major casualty. Smart sensor indicate the level of current vibration with its ideal value for prevention of excessive vibration it starts buzz ring. The work is highly applicable to the high speed trains. The high level vibration cause serious accidents due to the vibration.

  18. Implausibility of the vibrational theory of olfaction.

    Science.gov (United States)

    Block, Eric; Jang, Seogjoo; Matsunami, Hiroaki; Sekharan, Sivakumar; Dethier, Bérénice; Ertem, Mehmed Z; Gundala, Sivaji; Pan, Yi; Li, Shengju; Li, Zhen; Lodge, Stephene N; Ozbil, Mehmet; Jiang, Huihong; Penalba, Sonia F; Batista, Victor S; Zhuang, Hanyi

    2015-05-26

    The vibrational theory of olfaction assumes that electron transfer occurs across odorants at the active sites of odorant receptors (ORs), serving as a sensitive measure of odorant vibrational frequencies, ultimately leading to olfactory perception. A previous study reported that human subjects differentiated hydrogen/deuterium isotopomers (isomers with isotopic atoms) of the musk compound cyclopentadecanone as evidence supporting the theory. Here, we find no evidence for such differentiation at the molecular level. In fact, we find that the human musk-recognizing receptor, OR5AN1, identified using a heterologous OR expression system and robustly responding to cyclopentadecanone and muscone, fails to distinguish isotopomers of these compounds in vitro. Furthermore, the mouse (methylthio)methanethiol-recognizing receptor, MOR244-3, as well as other selected human and mouse ORs, responded similarly to normal, deuterated, and (13)C isotopomers of their respective ligands, paralleling our results with the musk receptor OR5AN1. These findings suggest that the proposed vibration theory does not apply to the human musk receptor OR5AN1, mouse thiol receptor MOR244-3, or other ORs examined. Also, contrary to the vibration theory predictions, muscone-d30 lacks the 1,380- to 1,550-cm(-1) IR bands claimed to be essential for musk odor. Furthermore, our theoretical analysis shows that the proposed electron transfer mechanism of the vibrational frequencies of odorants could be easily suppressed by quantum effects of nonodorant molecular vibrational modes. These and other concerns about electron transfer at ORs, together with our extensive experimental data, argue against the plausibility of the vibration theory.

  19. Understanding of bridge cable vibrations and the associate flow-field through the full-scale monitoring of vibrations and Wind

    DEFF Research Database (Denmark)

    Acampora, Antonio

    This dissertation investigates the conditions that promote rain-wind-induced vibrations of inclined cable on cable-stayed bridges. Rain-wind-induced vibrations are known as the most common type of cable vibrations and capable of severe vibrations. The recent increase in the number of cable stayed...... bridges continuously becoming longer and lighter have resulted in a high number of observations of cable vibrations. A theoretical background for the tool used in this work is presented in terms of cables vibrations mechanisms, aerodynamic damping and system identification techniques. A detailed...... literature review of reported observations of rain-wind-induced cable vibrations of fullscale bridges is shown. The database of observed events on bridges collects information about the conditions that likely develop the phenomenon, together with the means used to suppress or reduce the occurrence of cable...

  20. Vibrating fuel grapple. [LMFBR

    Science.gov (United States)

    Chertock, A.J.; Fox, J.N.; Weissinger, R.B.

    A reactor refueling method is described which utilizes a vibrating fuel grapple for removing spent fuel assemblies from a reactor core. It incorporates a pneumatic vibrator in the grapple head which allows additional withdrawal capability without exceeding the allowable axial force limit. The only moving part in the vibrator is a steel ball, pneumatically driven by a gas, such as argon, around a track, with centrifugal force created by the ball being transmitted through the grapple to the assembly handling socket.

  1. Application of Piezofilms for Excitation and Active Damping of Blade Flexural Vibration

    Czech Academy of Sciences Publication Activity Database

    Pešek, Luděk; Půst, Ladislav; Bula, Vítězslav; Cibulka, Jan

    2015-01-01

    Roč. 40, č. 1 (2015), s. 59-69 ISSN 0137-5075 Institutional support: RVO:61388998 Keywords : vibration suppression * parametric antiresonance * active damping * PVDF films Subject RIV: BI - Acoustics Impact factor: 0.661, year: 2015

  2. Vibrational and electronic spectroscopic studies of melatonin

    Science.gov (United States)

    Singh, Gurpreet; Abbas, J. M.; Dogra, Sukh Dev; Sachdeva, Ritika; Rai, Bimal; Tripathi, S. K.; Prakash, Satya; Sathe, Vasant; Saini, G. S. S.

    2014-01-01

    We report the infrared absorption and Raman spectra of melatonin recorded with 488 and 632.8 nm excitations in 3600-2700 and 1700-70 cm-1 regions. Further, we optimized molecular structure of the three conformers of melatonin within density functional theory calculations. Vibrational frequencies of all three conformers have also been calculated. Observed vibrational bands have been assigned to different vibrational motions of the molecules on the basis of potential energy distribution calculations and calculated vibrational frequencies. Observed band positions match well with the calculated values after scaling except Nsbnd H stretching mode frequencies. It is found that the observed and calculated frequencies mismatch of Nsbnd H stretching is due to intermolecular interactions between melatonin molecules.

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

    NARCIS (Netherlands)

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

    2010-01-01

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

  4. Quarkonium suppression

    Indian Academy of Sciences (India)

    posed as a test of its confining nature, since a sufficiently hot deconfined medium will dissolve any binding between the quark–antiquark pair [1]. Another possibility of disso- ciation of certain quarkonium states (subthreshold states at T = 0) is the decay into open charm (beauty) mesons due to in-medium modification of both ...

  5. Low temperature vibrational spectroscopy. II. Evidence for order–disorder phase transitions due to weak C–H···Cl hydrogen bonding in tetramethylammonium hexachloroplatinate (IV), -tellurate (IV), and -stannate (IV) and the related perdeuterated compounds

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    1978-01-01

    The low frequency infrared and Raman spectra of normal and per-deuterated ((CH3)4N)2[MCl6] (M=Pt, Te, or Sn) have been measured at temperatures down to ~100 K and evidence for phase transitions was found. The spectra have been carefully assigned and it was shown that bands due to forbidden methyl...

  6. Mechanical vibration and shock analysis, sinusoidal vibration

    CERN Document Server

    Lalanne, Christian

    2014-01-01

    Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m

  7. Model Indepedent Vibration Control

    OpenAIRE

    Yuan, Jing

    2010-01-01

    A NMIFC system is proposed for broadband vibration control. It has two important features. Feature F1 is that the NMIFC is stable without introducing any invasive effects, such as probing signals or controller perturbations, into the vibration system; feature F2 is

  8. Vibration Theory, Vol. 3

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 4th edition of this textbook on linear stochastic vibration...

  9. Handbook Of Noise And Vibration

    International Nuclear Information System (INIS)

    1995-12-01

    This book is about noise and vibration. The first chapter has explanations of noise such as basic of sound, influence of noise, assessment of noise, measurement of prevention of noise and technology, case of noise measurement and soundproof. The second chapter describes vibration with outline, theory of vibration, interpretation of vibration, measurement for reduction of vibration, case of design of protection against vibration. It deals with related regulation and method of measurement.

  10. Flow-induced vibration of helical coil compression springs

    International Nuclear Information System (INIS)

    Stokes, F.E.; King, R.A.

    1983-01-01

    Helical coil compression springs are used in some nuclear fuel assembly designs to maintain holddown and to accommodate thermal expansion. In the reactor environment, the springs are exposed to flowing water, elevated temperatures and pressures, and irradiation. Flow parallel to the longitudinal axis of the spring may excite the spring coils and cause vibration. The purpose of this investigation was to determine the flow-induced vibration (FIV) response characteristics of the helical coil compression springs. Experimental tests indicate that a helical coil spring responds like a single circular cylinder in cross-flow. Two FIV excitation mechanisms control spring vibration. Namely: 1) Turbulent Buffeting causes small amplitude vibration which increases as a function of velocity squared. 2) Vortex Shedding causes large amplitude vibration when the spring natural frequency and Strouhal frequency coincide. Several methods can be used to reduce or to prevent vortex shedding large amplitude vibrations. One method is compressing the spring to a coil pitch-to-diameter ratio of 2 thereby suppressing the vibration amplitude. Another involves modifying the spring geometry to alter its stiffness and frequency characteristics. These changes result in separation of the natural and Strouhal frequencies. With an understanding of how springs respond in the flowing water environment, the spring physical parameters can be designed to avoid large amplitude vibration. (orig.)

  11. Vibrations of rotating machinery

    CERN Document Server

    Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick

    2017-01-01

    This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...

  12. Vibrations in deformed nuclei

    International Nuclear Information System (INIS)

    Aprahamian, A.

    1992-01-01

    Quadrupole oscillations around a deformed shape give rise to vibrations in deformed nuclei. Single phonon vibrations of K = 0 (β) and K = 2 (γ) are a systematic feature in deformed nuclei, but the existence of multi-phonon vibrations had remained an open question until the recently reported results in 168 Er. In this nucleus, a two-phonon K = 4(γγ) band was observed at approximately 2.5 times the energy of the single γ vibration. The authors have studied several deformed rare-earth nuclei using the ( 4 He,2n) reaction in order to map out the systematic behavior of these multi-phonon vibrations. Recently, they have identified a similar K = 4 band in 154 Gd

  13. A numerical and experimental study on optimal design of multi-DOF viscoelastic supports for passive vibration control in rotating machinery

    Science.gov (United States)

    Ribeiro, Eduardo Afonso; Lopes, Eduardo Márcio de Oliveira; Bavastri, Carlos Alberto

    2017-12-01

    Viscoelastic materials have played an important role in passive vibration control. Nevertheless, the use of such materials in supports of rotating machines, aiming at controlling vibration, is more recent, mainly when these supports present additional complexities like multiple degrees of freedom and require accurate models to predict the dynamic behavior of viscoelastic materials working in a broad band of frequencies and temperatures. Previously, the authors propose a methodology for an optimal design of viscoelastic supports (VES) for vibration suppression in rotordynamics, which improves the dynamic prediction accuracy, the speed calculation, and the modeling of VES as complex structures. However, a comprehensive numerical study of the dynamics of rotor-VES systems, regarding the types and combinations of translational and rotational degrees of freedom (DOFs), accompanied by the corresponding experimental validation, is still lacking. This paper presents such a study considering different types and combinations of DOFs in addition to the simulation of their number of additional masses/inertias, as well as the kind and association of the applied viscoelastic materials (VEMs). The results - regarding unbalance frequency response, transmissibility and displacement due to static loads - lead to: 1) considering VES as complex structures which allow improving the efficacy in passive vibration control; 2) acknowledging the best configuration concerning DOFs and VEM choice and association for a practical application concerning passive vibration control and load resistance. The specific outcomes of the conducted experimental validation attest the accuracy of the proposed methodology.

  14. No Telescoping Effect with Dual Tendon Vibration.

    Directory of Open Access Journals (Sweden)

    Valeria Bellan

    Full Text Available The tendon vibration illusion has been extensively used to manipulate the perceived position of one's own body part. However, findings from previous research do not seem conclusive sregarding the perceptual effect of the concurrent stimulation of both agonist and antagonist tendons over one joint. On the basis of recent data, it has been suggested that this paired stimulation generates an inconsistent signal about the limb position, which leads to a perceived shrinkage of the limb. However, this interesting effect has never been replicated. The aim of the present study was to clarify the effect of a simultaneous and equal vibration of the biceps and triceps tendons on the perceived location of the hand. Experiment 1 replicated and extended the previous findings. We compared a dual tendon stimulation condition with single tendon stimulation conditions and with a control condition (no vibration on both 'upward-downward' and 'towards-away from the elbow' planes. Our results show a mislocalisation towards the elbow of the position of the vibrated arm during dual vibration, in line with previous results; however, this did not clarify whether the effect was due to arm representation contraction (i.e., a 'telescoping' effect. Therefore, in Experiment 2 we investigated explicitly and implicitly the perceived arm length during the same conditions. Our results clearly suggest that in all the vibration conditions there was a mislocalisation of the entire arm (including the elbow, but no evidence of a contraction of the perceived arm length.

  15. Effect of low-frequency vibrations on speckle interferometry fringes

    International Nuclear Information System (INIS)

    Vikram, C.S.; Pechersky, M.J.

    1998-01-01

    The effects of low-frequency vibrations on speckle correlation fringes have been investigated. The relatively short capture time of the camera in the low-frequency case may yield usable fringe contrast in spite of vibration. It has been shown that the fringes also shift due to the vibration. The study is in agreement with experimental observations of good-contrast correlation fringes even if the object is not on a vibration-isolated table. Some such experimental observations are also presented. copyright 1998 Society of Photo-Optical Instrumentation Engineers

  16. Studies of interstellar vibrationally-excited molecules

    International Nuclear Information System (INIS)

    Ziurys, L.M.; Snell, R.L.; Erickson, N.R.

    1986-01-01

    Several molecules thus far have been detected in the ISM in vibrationally-excited states, including H 2 , SiO, HC 3 N, and CH 3 CN. In order for vibrational-excitation to occur, these species must be present in unusually hot and dense gas and/or where strong infrared radiation is present. In order to do a more thorough investigation of vibrational excitation in the interstellar medium (ISM), studies were done of several mm-wave transitions originating in excited vibrational modes of HCN, an abundant interstellar molecule. Vibrationally-excited HCN was recently detected toward Orion-KL and IRC+10216, using a 12 meter antenna. The J=3-2 rotational transitions were detected in the molecule's lowest vibrational state, the bending mode, which is split into two separate levels, due to l-type doubling. This bending mode lies 1025K above ground state, with an Einstein A coefficient of 3.6/s. The J=3-2 line mode of HCN, which lies 2050K above ground state, was also observed toward IRC+10216, and subsequently in Orion-KL. Further measurements of vibrationally-excited HCN were done using a 14 meter telescope, which include the observations of the (0,1,0) and (0,2,0) modes towards Orion-KL, via their J=3-2 transitions at 265-267 GHz. The spectrum of the J=3-2 line in Orion taken with the 14 meter telescope, is shown, along with a map, which indicates that emission from vibrationally-excited HCN arises from a region probably smaller than the 14 meter telescope's 20 arcsec beam

  17. On aspects of vibration of axially moving continua

    NARCIS (Netherlands)

    Hageraats-Ponomareva, S.

    2009-01-01

    In axially moving structures like conveyor belt systems, magnetic tapes, and so on, vibrations occur due to the presence of different kinds of imperfections in the systems. For these structures internal resonances can lead to severe vibrations. Resonance free conveyor belt systems can be constructed

  18. Subsurface melting of nylon by friction-induced vibrations

    NARCIS (Netherlands)

    Vroegop, P.H.; Bosma, R.

    1985-01-01

    Dry sliding of nylon on steel may lead to subsurface recrystallization of the polymer. This phenomenon is described and explained by subsurface melting due to internal heating as a result of the dissipation of frictioninduced vibrations at frequencies above 10 kHz. A vibration model relating the

  19. Effect of multi axis vibration and subject postures on sketching ...

    African Journals Online (AJOL)

    Sedentary activities such as reading, writing, sketching, etc. are affected due to the train vibrations. Therefore, the present study investigates the extent of perceived difficulty and distortion in a sketching task by seated subjects in two postures under low frequency, multi axial random vibrations. Thirty male voluntary subjects ...

  20. Structural Stability and Vibration

    DEFF Research Database (Denmark)

    Wiggers, Sine Leergaard; Pedersen, Pauli

    This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author at the Uni......This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....

  1. Coherent vibrational dynamics

    CERN Document Server

    Lanzani, Guglielmo; De Silvestri, Sandro

    2007-01-01

    Vibrational spectroscopy is a powerful investigation tool for a wide class of materials covering diverse areas in physics, chemistry and biology. The continuous development in the laser field regarding ultrashort pulse generation has led to the possibility of producing light pulses that can follow vibrational motion coupled to the electronic transitions in molecules and solids in real time. Aimed at researchers and graduate students using vibrational spectroscopy, this book provides both introductory chapters as well as more advanced contents reporting on recent progress. It also provides a good starting point for scientists seeking a sound introduction to ultrafast optics and spectroscopic techniques.

  2. THz-SAR Vibrating Target Imaging via the Bayesian Method

    Directory of Open Access Journals (Sweden)

    Bin Deng

    2017-01-01

    Full Text Available Target vibration bears important information for target recognition, and terahertz, due to significant micro-Doppler effects, has strong advantages for remotely sensing vibrations. In this paper, the imaging characteristics of vibrating targets with THz-SAR are at first analyzed. An improved algorithm based on an excellent Bayesian approach, that is, the expansion-compression variance-component (ExCoV method, has been proposed for reconstructing scattering coefficients of vibrating targets, which provides more robust and efficient initialization and overcomes the deficiencies of sidelobes as well as artifacts arising from the traditional correlation method. A real vibration measurement experiment of idle cars was performed to validate the range model. Simulated SAR data of vibrating targets and a tank model in a real background in 220 GHz show good performance at low SNR. Rapidly evolving high-power terahertz devices will offer viable THz-SAR application at a distance of several kilometers.

  3. Vibration Analysis and the Accelerometer

    Science.gov (United States)

    Hammer, Paul

    2011-01-01

    Have you ever put your hand on an electric motor or motor-driven electric appliance and felt it vibrate? Ever wonder why it vibrates? What is there about the operation of the motor, or the object to which it is attached, that causes the vibrations? Is there anything "regular" about the vibrations, or are they the result of random causes? In this…

  4. PREFACE: Vibrations at surfaces Vibrations at surfaces

    Science.gov (United States)

    Rahman, Talat S.

    2011-12-01

    This special issue is dedicated to the phenomenon of vibrations at surfaces—a topic that was indispensible a couple of decades ago, since it was one of the few phenomena capable of revealing the nature of binding at solid surfaces. For clean surfaces, the frequencies of modes with characteristic displacement patterns revealed how surface geometry, as well as the nature of binding between atoms in the surface layers, could be different from that in the bulk solid. Dispersion of the surface phonons provided further measures of interatomic interactions. For chemisorbed molecules on surfaces, frequencies and dispersion of the vibrational modes were also critical for determining adsorption sites. In other words, vibrations at surfaces served as a reliable means of extracting information about surface structure, chemisorption and overlayer formation. Experimental techniques, such as electron energy loss spectroscopy and helium-atom-surface scattering, coupled with infra-red spectroscopy, were continually refined and their resolutions enhanced to capture subtleties in the dynamics of atoms and molecules at surfaces. Theoretical methods, whether based on empirical and semi-empirical interatomic potential or on ab initio electronic structure calculations, helped decipher experimental observations and provide deeper insights into the nature of the bond between atoms and molecules in regions of reduced symmetry, as encountered on solid surfaces. Vibrations at surfaces were thus an integral part of the set of phenomena that characterized surface science. Dedicated workshops and conferences were held to explore the variety of interesting and puzzling features revealed in experimental and theoretical investigations of surface vibrational modes and their dispersion. One such conference, Vibrations at Surfaces, first organized by Harald Ibach in Juelich in 1980, continues to this day. The 13th International Conference on Vibrations at Surfaces was held at the University of

  5. A vibration sieve

    Energy Technology Data Exchange (ETDEWEB)

    Alekhin, S.A.; Denisenko, V.V.; Dzhalalov, M.G.; Kirichek, F.P.; Pitatel, Yu.A.; Prokopov, L.I.; Tikhonov, Yu.P.

    1982-01-01

    A vibration sieve is proposed which includes a vibration drive, a body and a screen installed on shock absorbers, a device for washing out the screen, and a subassembly for loading the material. To increase the operational reliability and effectiveness of the vibration sieve by improving the cleaning of the screen, the loading subassembly is equipped with a baffle with a lever which is hinged to it. The device for washing out the screen is made in the form of an electromagnet with a connecting rod, a switch and an eccentric, a friction ratchet mechanism and sprinkling systems. Here, the latter are interconnected, using a connecting rod, while the sprinkling system is installed on rollers under the screen. The electromagnetic switch is installed under the lever. The body is made with grooves for installing the sprinkling system. The vibration sieve is equipped with a switch which interacts with the connecting rod. The friction ratchet mechanism is equipped with a lug.

  6. Vibrational characteristics and wear of fuel rods

    International Nuclear Information System (INIS)

    Schmugar, K.L.

    1977-01-01

    Fuel rod wear, due to vibration, is a continuing concern in the design of liquid-cooled reactors. In my report, the methodology and models that are used to predict fuel rod vibrational response and vibratory wear, in a light water reactor environment, are discussed. This methodology is being followed at present in the design of Westinghouse Nuclear Fuel. Fuel rod vibrations are expressed as the normal bending modes, and sources of rod vibration are examined with special emphasis on flow-induced mechanisms in the stable flow region. In a typical Westinghouse PWR fuel assembly design, each fuel rod is supported at multiple locations along the rod axis by a square-shaped 'grid cell'. For a fuel rod /grid support system, the development of small oscillatory motions, due to fluid flow at the rod/grid interface, results in material wear. A theoretical wear mode is developed using the Archard Theory of Adhesive Wear as the basis. Without question certainty, fretting wear becomes a serious problem if it progresses to the stage where the fuel cladding is penetrated and fuel is exposed to the coolant. Westinghouse fuel is designed to minimize fretting wear by limiting the relative motion between the fuel rod and its supports. The wear producing motion between the fuel rod and its supports occurs when the vibration amplitude exceeds the slippage threshold amplitude

  7. 2008 Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Philip J. Reid

    2009-09-21

    The conference focuses on using vibrational spectroscopy to probe structure and dynamics of molecules in gases, liquids, and interfaces. The goal is to bring together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of systems.

  8. Optimal Damping of Stays in Cable-Stayed Bridges for In-Plane Vibrations

    DEFF Research Database (Denmark)

    Jensen, C.N.; Nielsen, S.R.K.; Sørensen, John Dalsgaard

    2002-01-01

    Significant vibrations have been reported in stays of recently constructed cable stayed bridges. The vibrations appear as in-plane vibrations that may be caused by rain–wind- induced aeroelastic interaction or by resonance excitation of the cables from the motion of the pylons. The stays of modern...... cable-stayed bridges are often designed as twin cables with a spacing of, say 1m. In such cases, it is suggested in the paper to suppress the mentioned in-plane types of vibrations by means of a tuned mass–damper (TMD) placed between the twin cables at their midpoints. The TMD divides the stay into four...

  9. Validity and inter-observer reliability of subjective hand-arm vibration assessments

    NARCIS (Netherlands)

    Coenen, P.; Formanoy, M.; Douwes, M.; Bosch, T.; Kraker, H. de

    2014-01-01

    Exposure to mechanical vibrations at work (e.g., due to handling powered tools) is a potential occupational risk as it may cause upper extremity complaints. However, reliable and valid assessment methods for vibration exposure at work are lacking. Measuring hand-arm vibration objectively is often

  10. Report of workshop on vibration related to fluid in atomic energy field. 4

    International Nuclear Information System (INIS)

    1993-01-01

    This is the fourth workshop on the vibration related to fluid in atomic energy field of Yayoi research group. This time, two topics were taken up. One is edgetone phenomena and the liquid surface vibration phenomena due to flow. Another is the introduction of the experience in light water reactors. The workshop was held on August 30 and 31, 1993 at Nuclear Engineering Research Laboratory, University of Tokyo. At the workshop, lectures were given on the mechanism of occurrence of edgetone, the theoretical analysis of edgetone and edgenoise, the self-excited vibration of free liquid surface due to vertical plane jet and vertical cylindrical jet, the research on flow instability phenomena in parallel loop system, the irregular vibration behavior of U-shaped tubes excited by flow, the research on the vibration of cyclindrical weir due to fluid discharge, the examples of the vibration related to fluid in LWRs, the estimation of fatigue phenomena in bearing rings, the vibration of rotary vanes and verifying test, the analysis of flow in isolated phase bus plate vane and the measurement of velocity distribution, flow in piping and the behavior of valve vibration, the condition for the occurrence of flow vibration in the main steam separation valve of BWR, the vibration of piping due to orifice, the analysis of flow in two-dimensional vibrating cascade, and the subjects of fluid vibration assessment in atomic energy. (K.I.)

  11. Laserlike Vibrational Instability in Rectifying Molecular Conductors

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Hedegård, Per; Brandbyge, Mads

    2011-01-01

    We study the damping of molecular vibrations due to electron-hole pair excitations in donor-acceptor (D-A) type molecular rectifiers. At finite voltage additional nonequilibrium electron-hole pair excitations involving both electrodes become possible, and contribute to the stimulated emission....... We investigate the effect in realistic molecular rectifier structures using first-principles calculations....

  12. Impact Vibration Attenuation for a Flexible Robotic Manipulator through Transfer and Dissipation of Energy

    OpenAIRE

    Bian, Yushu; Gao, Zhihui

    2013-01-01

    Due to the presence of system flexibility, impact can excite severe large amplitude vibration responses of the flexible robotic manipulator. This impact vibration exhibits characteristics of remarkable nonlinearity and strong energy. The main goal of this study is to put forward an energy-based control method to absorb and attenuate large amplitude impact vibration of the flexible robotic manipulator. The method takes advantage of internal resonance and is implemented through a vibration abso...

  13. Forced vibrations of rotating circular cylindrical shells

    International Nuclear Information System (INIS)

    Igawa, Hirotaka; Maruyama, Yoshiyuki; Endo, Mitsuru

    1995-01-01

    Forced vibrations of rotating circular cylindrical shells are investigated. Basic equations, including the effect of initial stress due to rotation, are formulated by the finite-element method. The characteristic relations for finite elements are derived from the energy principle by considering the finite strain. The equations of motion can be separated into quasi-static and dynamic ones, i.e., the equations in the steady rotating state and those in the vibration state. Radial concentrated impulses are considered as the external dynamic force. The transient responses of circular cylindrical shells are numerically calculated under various boundary conditions and rotating speeds. (author)

  14. Menstrual suppression for adolescents with developmental disabilities.

    Science.gov (United States)

    Savasi, I; Spitzer, R F; Allen, L M; Ornstein, M P

    2009-06-01

    The approach to menstrual suppression for adolescents with developmental disabilities has evolved considerably over the years due to changing philosophies and evolving treatment options. We review the medical management options available for menstrual suppression with a focus on the needs and treatment of adolescents with developmental disabilities.

  15. Due diligence

    International Nuclear Information System (INIS)

    Sanghera, G.S.

    1999-01-01

    The Occupational Health and Safety (OHS) Act requires that every employer shall ensure the health and safety of workers in the workplace. Issues regarding the practices at workplaces and how they should reflect the standards of due diligence were discussed. Due diligence was described as being the need for employers to identify hazards in the workplace and to take active steps to prevent workers from potentially dangerous incidents. The paper discussed various aspects of due diligence including policy, training, procedures, measurement and enforcement. The consequences of contravening the OHS Act were also described

  16. Influence of gravitational and vibrational convection on the heat- and mass transfer in the melt during crystal growing by Bridgman and floating zone methods

    Science.gov (United States)

    Fedorov, Oleg

    2016-07-01

    Space materials science is one of the priorities of different national and international space programs. The physical processes of heat and mass transfer in microgravity (including effect of g-jitter) is far from complete clarity, especially for important practical technology for producing crystals from the melt. The idea of the impact on crystallizing melt by low frequency vibration includes not only the possibility to suppress unwanted microaccelerations, but also to actively influence the structure of the crystallization front. This approach is one of the most effective ways to influence the quality of materials produced in flight conditions. The subject of this work is the effect of vibrations on the thermal and hydrodynamic processes during crystal growth using Bridgman and floating zone techniques, which have the greatest prospect of practical application in space. In the present approach we consider the gravitational convection, Marangoni convection, as well as the effect of vibration on the melt for some special cases. The results of simulation were compared with some experimental data obtained by the authors using a transparent model substance - succinonitrile (Bridgman method), and silicon (floating zone method). Substances used, process parameters and characteristics of the experimental units correspond the equipment developed for onboard research and serve as a basis for selecting optimum conditions vibration exposure as a factor affecting the solidification pattern. The direction of imposing vibrations coincides with the axis of the crystal, the frequency is presented by the harmonic law, and the force of gravity was varied by changing its absolute value. Mathematical model considered axisymmetric approximation of joint convective-conductive energy transfer in the system crystal - melt. Upon application of low-frequency oscillations of small amplitude along the axis of growing it was found the suppression of the secondary vortex flows near the

  17. Multivariate Analysis of Ladle Vibration

    Science.gov (United States)

    Yenus, Jaefer; Brooks, Geoffrey; Dunn, Michelle

    2016-08-01

    The homogeneity of composition and uniformity of temperature of the steel melt before it is transferred to the tundish are crucial in making high-quality steel product. The homogenization process is performed by stirring the melt using inert gas in ladles. Continuous monitoring of this process is important to make sure the action of stirring is constant throughout the ladle. Currently, the stirring process is monitored by process operators who largely rely on visual and acoustic phenomena from the ladle. However, due to lack of measurable signals, the accuracy and suitability of this manual monitoring are problematic. The actual flow of argon gas to the ladle may not be same as the flow gage reading due to leakage along the gas line components. As a result, the actual degree of stirring may not be correctly known. Various researchers have used one-dimensional vibration, and sound and image signals measured from the ladle to predict the degree of stirring inside. They developed online sensors which are indeed to monitor the online stirring phenomena. In this investigation, triaxial vibration signals have been measured from a cold water model which is a model of an industrial ladle. Three flow rate ranges and varying bath heights were used to collect vibration signals. The Fast Fourier Transform was applied to the dataset before it has been analyzed using principal component analysis (PCA) and partial least squares (PLS). PCA was used to unveil the structure in the experimental data. PLS was mainly applied to predict the stirring from the vibration response. It was found that for each flow rate range considered in this study, the informative signals reside in different frequency ranges. The first latent variables in these frequency ranges explain more than 95 pct of the variation in the stirring process for the entire single layer and the double layer data collected from the cold model. PLS analysis in these identified frequency ranges demonstrated that the latent

  18. Mechanical vibration to electrical energy converter

    Science.gov (United States)

    Kellogg, Rick Allen [Tijeras, NM; Brotz, Jay Kristoffer [Albuquerque, NM

    2009-03-03

    Electromechanical devices that generate an electrical signal in response to an external source of mechanical vibrations can operate as a sensor of vibrations and as an energy harvester for converting mechanical vibration to electrical energy. The devices incorporate a magnet that is movable through a gap in a ferromagnetic circuit, wherein a coil is wound around a portion of the ferromagnetic circuit. A flexible coupling is used to attach the magnet to a frame for providing alignment of the magnet as it moves or oscillates through the gap in the ferromagnetic circuit. The motion of the magnet can be constrained to occur within a substantially linear range of magnetostatic force that develops due to the motion of the magnet. The devices can have ferromagnetic circuits with multiple arms, an array of magnets having alternating polarity and, encompass micro-electromechanical (MEM) devices.

  19. Vibration transducer calibration techniques

    Science.gov (United States)

    Brinkley, D. J.

    1980-09-01

    Techniques for the calibration of vibration transducers used in the Aeronautical Quality Assurance Directorate of the British Ministry of Defence are presented. Following a review of the types of measurements necessary in the calibration of vibration transducers, the performance requirements of vibration transducers, which can be used to measure acceleration, velocity or vibration amplitude, are discussed, with particular attention given to the piezoelectric accelerometer. Techniques for the accurate measurement of sinusoidal vibration amplitude in reference-grade transducers are then considered, including the use of a position sensitive photocell and the use of a Michelson laser interferometer. Means of comparing the output of working-grade accelerometers with that of previously calibrated reference-grade devices are then outlined, with attention given to a method employing a capacitance bridge technique and a method to be used at temperatures between -50 and 200 C. Automatic calibration procedures developed to speed up the calibration process are outlined, and future possible extensions of system software are indicated.

  20. Vision-based online vibration estimation of the in-vessel inspection flexible robot with short-time Fourier transformation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hesheng [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China); Chen, Weidong, E-mail: wdchen@sjtu.edu.cn [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China); Xu, Lifei; He, Tao [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-10-15

    Highlights: • Vision-based online vibration estimation method for a flexible arm is proposed. • The vibration signal is obtained by image processing in unknown environments. • Vibration parameters are estimated by short-time Fourier transformation. - Abstract: The vibration should be suppressed if it happens during the motion of a flexible robot or under the influence of external disturbance caused by its structural features and material properties, because the vibration may affect the positioning accuracy and image quality. In Tokamak environment, we need to get the real-time vibration information on vibration suppression of robotic arm, however, some sensors are not allowed in the extreme Tokamak environment. This paper proposed a vision-based method for online vibration estimation of a flexible manipulator, which is achieved by utilizing the environment image information from the end-effector camera to estimate its vibration. Short-time Fourier Transformation with adaptive window length method is used to estimate vibration parameters of non-stationary vibration signals. Experiments with one-link flexible manipulator equipped with camera are carried out to validate the feasibility of this method in this paper.

  1. Analysis and simulation of centrifugal pendulum vibration absorbers

    OpenAIRE

    Smith, Emma

    2015-01-01

    When environmental laws are constricted and downsizing of engines has become the reality of the vehicle industry, there needs to be a solution for the rise in torsion vibrations in the drivetrain. These increased levels of torsion vibrations are mostly due to excitations from the firing pulses, which in turn have become increased due to higher cylinder pressures. One of the solutions for further dampening the system is to add a centrifugal pendulum absorber to the flywheel, and predicting the...

  2. Vibration behavior of the artificial barrier system

    Energy Technology Data Exchange (ETDEWEB)

    Mikoshiba, Tadashi; Ogawa, Nobuyuki; Nakamura, Izuru [National Research Inst. for Earth sceince and Disaster Prevention (Japan)

    2000-02-01

    This study aims at production of a mimic specimen of artificial barrier, experimental elucidation of influence of seismic motion due to a vibration experiment on the artificial barrier system, and establishment of an evaluating method on its long-term behavior. The study has been carried out under a cooperative study of the National Research Institute for Earth Science and Disaster Prevention and the Japan Nuclear Cycle Development Institute. In 1998 fiscal year, an artificial barrier specimen initiated by crosscut road was produced, and their random wave and actual seismic wave vibrations were carried out to acquire their fundamental data. As a result of the both vibrations, it was found that in a Case 2 specimen of which buffer material was swelled by poured water, the material was integrated with a mimic over-pack to vibrate under judgement of eigen-frequency, maximum acceleration ratio, and so forth on the test results. And, in a Case 1 specimen, it was thought that the mimic over-pack showed an extreme non-linear performance (soft spring) because of reducing eigen-frequency with increase of its vibration level. (G.K.)

  3. Multi-objective optimization of piezoelectric circuitry network for mode delocalization and suppression of bladed disk

    Science.gov (United States)

    Yoo, David; Tang, J.

    2017-04-01

    Since weakly-coupled bladed disks are highly sensitive to the presence of uncertainties, they can easily undergo vibration localization. When vibration localization occurs, vibration modes of bladed disk become dramatically different from those under the perfectly periodic condition, and the dynamic response under engine-order excitation is drastically amplified. In previous studies, it is investigated that amplified vibration response can be suppressed by connecting piezoelectric circuitry into individual blades to induce the damped absorber effect, and localized vibration modes can be alleviated by integrating piezoelectric circuitry network. Delocalization of vibration modes and vibration suppression of bladed disk, however, require different optimal set of circuit parameters. In this research, multi-objective optimization approach is developed to enable finding the best circuit parameters, simultaneously achieving both objectives. In this way, the robustness and reliability in bladed disk can be ensured. Gradient-based optimizations are individually developed for mode delocalization and vibration suppression, which are then integrated into multi-objective optimization framework.

  4. Vibration Problems of Rotating Machinery due to Coupling Misalignments

    Science.gov (United States)

    1988-05-01

    rotation planes would be parallel. Since pCP ) and qCe) are vectors corresponding 36 0 , l ~ I I N l lll .. . Notei The vectors X p and q ex-tendi...Plane of Initial Curvature", Timoshenko (1930) utilized Castigliano’s theorems and the principle of Least work to determine the deflection of a curved...4 132 4133 Sb 9 M. = -PRsinCQ - C6)X and M = PRC1 - cosCcx - ). C7) zp Applying Castigliano’s second theorem yields: (dV/dP) = d. (8) Combining

  5. Vibrations in orthopedics.

    Science.gov (United States)

    Nokes, L D; Thorne, G C

    1988-01-01

    Measurements of various mechanical properties of skeletal material using vibration techniques have been reported. The purposes of such investigations include the monitoring of pathogenic disorders such as osteoporosis, the rate and extent of fracture healing, and the status of internal fixations. Early investigations pioneered the application of conventional vibration measurement equipment to biological systems. The more recent advent of the microcomputer has made available to research groups more sophisticated techniques for data acquisition and analysis. The economical advantages of such equipment has led to the development of portable research instrumentation which lends itself to use in a clinical environment. This review article reports on the developments and progression of the various vibrational techniques and theories as applied to musculoskeletal systems.

  6. Vibration immission forecast by means of train equivalent synthetic vibration experiments

    Directory of Open Access Journals (Sweden)

    Steinhauser Peter

    2015-01-01

    Full Text Available Vibration abatement measures at a railway track require forecasts before the rails are put into place. Due to the multiple feedback system between train, track, geodynamics of the local underground and the dynamic behavior of the neighbourhood buildings these prognoses become very elaborate. All the parameters of the dynamic system scatter extremely as the results from numerous investigations prove. This concerns vibration emission spectra, tunnel mobility, geodynamic vibration loss along the transfer through the underground as well as the natural frequencies from buildings and ceilings. Therefore experimental in-situ investigations are indispensable for trustworthy forecasts. In this paper the VibroScan method is presented, whose basic idea is to implement the principle of equivalence between the synthetic vibrations used for the experiments and train vibration emissions at the highest possible degree. This is focused on emission spectra, force of excitation, unsprung wheelset mass and axle load. The necessary experimental provisions are discussed and some examples of results are given like the protection of the Musikverein building in Vienna or the Sagrada Familia basilica in Barcelona against vibrations from tunnels in the immediate neighbourhood.

  7. Low-dose oral tolerance due to antigen in the diet suppresses differentially the cholera toxin-adjuvantized IgE, IgA and IgG response

    DEFF Research Database (Denmark)

    Christensen, Hanne Risager; Kjær, Tanja; Frøkiær, Hanne

    2003-01-01

    Background: Cholera toxin (CT) is used as a mucosal adjuvant amongst other applications for studying food allergy because oral administration of antigen with CT induces an antigen-specific type 2 response, including IgE and IgA production. Priorly established oral tolerance due to antigen...... in the diet may radically impact on the CT-adjuvantized immune response. The present study served to evaluate the effect of priorly established low-dose oral tolerance on the CT-adjuvantized immune response towards a food antigen. Methods: Mice fed a diet containing microgram levels of the soy protein Kunitz...... soy-trypsin inhibitor (KSTI) (F0 mice) and mice fed a soy-free diet (F2 mice) were orally immunized with KSTI and CT. KSTI-specific serum IgG1, IgG2a, IgA and IgE and fecal IgA were monitored. KSTI-stimulated cell proliferation and interleukin (IL)-6 production were determined. Results: The anti...

  8. Growth hormone suppression test

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/003376.htm Growth hormone suppression test To use the sharing features on this page, please enable JavaScript. The growth hormone suppression test determines whether growth hormone production is ...

  9. Vibrations and waves

    CERN Document Server

    Kaliski, S

    2013-01-01

    This book gives a comprehensive overview of wave phenomena in different media with interacting mechanical, electromagnetic and other fields. Equations describing wave propagation in linear and non-linear elastic media are followed by equations of rheological models, models with internal rotational degrees of freedom and non-local interactions. Equations for coupled fields: thermal, elastic, electromagnetic, piezoelectric, and magneto-spin with adequate boundary conditions are also included. Together with its companion volume Vibrations and Waves. Part A: Vibrations this work provides a wealth

  10. Vibration Theory, Vol. 3

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration th...... theory is basically unchanged in comparison to the 1st edition. Only section 4.2 on single input - single output systems and chapter 6 on offshore structures have been modified in order to enhance the clearness....

  11. Tiltrotor Vibration Reduction Through Higher Harmonic Control

    Science.gov (United States)

    Nixon, Mark W.; Kvaternik, Raymond G.; Settle, T. Ben

    1997-01-01

    The results of a joint NASA/Army/Bell Helicopter Textron wind-tunnel test to assess the potential of higher harmonic control (HHC) for reducing vibrations in tiltrotor aircraft operating in the airplane mode of flight, and to evaluate the effectiveness of a Bell-developed HHC algorithm called MAVSS (Multipoint Adaptive Vibration Suppression System) are presented. The test was conducted in the Langley Transonic Dynamics Tunnel using an unpowered 1/5-scale semispan aeroelastic model of the V-22 which was modified to incorporate an HHC system employing both the rotor swashplate and the wing flaperon. The effectiveness of the swashplate and the flaperon acting either singly or in combination in reducing IP and 3P wing vibrations over a wide range of tunnel airspeeds and rotor rotational speeds was demonstrated. The MAVSS algorithm was found to be robust to variations in tunnel airspeed and rotor speed, requiring only occasional on-line recalculations of the system transfer matrix. HHC had only a small (usually beneficial) effect on blade loads but increased pitch link loads by 25%. No degradation in aeroelastic stability was noted for any of the conditions tested.

  12. Heterogeneous Dynamics of Coupled Vibrations

    NARCIS (Netherlands)

    Cringus, Dan; Jansen, Thomas I. C.; Pshenichnikov, Maxim S.; Schoenlein, RW; Corkum, P; DeSilvestri, S; Nelson, KA; Riedle, E

    2009-01-01

    Frequency-dependent dynamics of coupled stretch vibrations of a water molecule are revealed by 2D IR correlation spectroscopy. These are caused by non-Gaussian fluctuations of the environment around the individual OH stretch vibrations.

  13. Vibrationally Assisted Electron Transfer Mechanism of Olfaction: Myth or Reality?

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Chang, Po-Yao; Schulten, Klaus

    2012-01-01

    to this suggestion an olfactory receptor is activated by electron transfer assisted through odorant vibrational excitation. The hundreds to thousands of different olfactory receptors in an animal recognize odorants over a discriminant landscape with surface properties and vibrational frequencies as the two major...... dimensions. In the present paper we introduce the vibrationally assisted mechanism of olfaction and demonstrate for several odorants that, indeed, a strong enhancement of an electron tunneling rate due to odorant vibrations can arise. We discuss in this regard the influence of odorant deuteration and explain...... olfactory receptors and odorants must obey for the vibrationally assisted electron transfer mechanism to function. We argue that the stated characteristics are feasible for realistic olfactory receptors, noting, though, that the receptor structure presently is still unknown, but can be studied through...

  14. Efficiency of Nearly Periodic Structures for Mitigation of Ground Vibration

    DEFF Research Database (Denmark)

    Andersen, Lars Vabbersgaard; Peplow, Andrew; Bucinskas, Paulius

    2017-01-01

    Periodic structures are known to produce passbands and stopbands for propagation of vibration energy within the frequency domain. Sources vibrating harmonically at a frequency within a passband can lead to propagation of energy through propagating modes over long distances. However, sources...... vibrating at a frequency within a stopband excite only nearfields in the form of attenuating and evanescent modes, and the energy decays with distance. The decay phenomena are due to destructive interference of waves reflected and scattered by interfaces or obstacles placed periodically within or between...... the repeated cells of the structure. For a truly periodic structure, the vibration level within a stopband goes toward zero after infinitely many repetitions of the cell. For example, employing a two-dimensional model, Andersen [1] found that stopbands for ground vibration in the low-frequency range can...

  15. Fault diagnosis of planetary gearboxes via torsional vibration signal analysis

    Science.gov (United States)

    Feng, Zhipeng; Zuo, Ming J.

    2013-04-01

    Torsional vibration signals are theoretically free from the amplitude modulation effect caused by time variant vibration transfer paths due to the rotation of planet carrier and sun gear, and therefore their spectral structure are simpler than transverse vibration signals. Thus, it is potentially easy and effective to diagnose planetary gearbox faults via torsional vibration signal analysis. We give explicit equations to model torsional vibration signals, considering both distributed gear faults (like manufacturing or assembly errors) and local gear faults (like pitting, crack or breakage of one tooth), and derive the characteristics of both the traditional Fourier spectrum and the proposed demodulated spectra of amplitude envelope and instantaneous frequency. These derivations are not only effective to diagnose single gear fault of planetary gearboxes, but can also be generalized to detect and locate multiple gear faults. We validate experimentally the signal models, as well as the Fourier spectral analysis and demodulation analysis methods.

  16. Composite Struts Would Damp Vibrations

    Science.gov (United States)

    Dolgin, Benjamin P.

    1991-01-01

    New design of composite-material (fiber/matrix laminate) struts increases damping of longitudinal vibrations without decreasing longitudinal stiffness or increasing weight significantly. Plies with opposing chevron patterns of fibers convert longitudinal vibrational stresses into shear stresses in intermediate viscoelastic layer, which dissipate vibrational energy. Composite strut stronger than aluminum strut of same weight and stiffness.

  17. Development of vibrating insoles

    NARCIS (Netherlands)

    Hijmans, J.M.; Geertzen, J.H.B.; Schokker, B.; Postema, K.

    2007-01-01

    The objective of this study was to describe the development of vibrating insoles. Insoles, providing a subsensory mechanical noise signal to the plantar side of the feet, may improve balance in healthy young and older people and in patients with stroke or diabetic neuropathy. This study describes

  18. Vibrational Spectroscopy and Astrobiology

    Science.gov (United States)

    Chaban, Galina M.; Kwak, D. (Technical Monitor)

    2001-01-01

    Role of vibrational spectroscopy in solving problems related to astrobiology will be discussed. Vibrational (infrared) spectroscopy is a very sensitive tool for identifying molecules. Theoretical approach used in this work is based on direct computation of anharmonic vibrational frequencies and intensities from electronic structure codes. One of the applications of this computational technique is possible identification of biological building blocks (amino acids, small peptides, DNA bases) in the interstellar medium (ISM). Identifying small biological molecules in the ISM is very important from the point of view of origin of life. Hybrid (quantum mechanics/molecular mechanics) theoretical techniques will be discussed that may allow to obtain accurate vibrational spectra of biomolecular building blocks and to create a database of spectroscopic signatures that can assist observations of these molecules in space. Another application of the direct computational spectroscopy technique is to help to design and analyze experimental observations of ice surfaces of one of the Jupiter's moons, Europa, that possibly contains hydrated salts. The presence of hydrated salts on the surface can be an indication of a subsurface ocean and the possible existence of life forms inhabiting such an ocean.

  19. Structural Stability and Vibration

    DEFF Research Database (Denmark)

    Wiggers, Sine Leergaard; Pedersen, Pauli

    This book offers an integrated introduction to the topic of stability and vibration. Strikingly, it describes stability as a function of boundary conditions and eigenfrequency as a function of both boundary conditions and column force. Based on a post graduate course held by the author...

  20. Vibrations and Eigenvalues

    Indian Academy of Sciences (India)

    rical or mechanical reasonings, but solely algebraic [analytic] operations subjected to a uniform and regular procedure. Those. Keywords. Vibrations, eigenvalues .... Suggested Reading. [1] R Bhatia, Fourier Series, Hindustan Book Agency, Second Edition, 2003. [2] G Strang, Essays in Linear Algebra, SIAM, 2012. 872.

  1. Compact Vibration Damper

    Science.gov (United States)

    Ivanco, Thomas G. (Inventor)

    2014-01-01

    A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.

  2. Blade Vibration Measurement System

    Science.gov (United States)

    Platt, Michael J.

    2014-01-01

    The Phase I project successfully demonstrated that an advanced noncontacting stress measurement system (NSMS) could improve classification of blade vibration response in terms of mistuning and closely spaced modes. The Phase II work confirmed the microwave sensor design process, modified the sensor so it is compatible as an upgrade to existing NSMS, and improved and finalized the NSMS software. The result will be stand-alone radar/tip timing radar signal conditioning for current conventional NSMS users (as an upgrade) and new users. The hybrid system will use frequency data and relative mode vibration levels from the radar sensor to provide substantially superior capabilities over current blade-vibration measurement technology. This frequency data, coupled with a reduced number of tip timing probes, will result in a system capable of detecting complex blade vibrations that would confound traditional NSMS systems. The hardware and software package was validated on a compressor rig at Mechanical Solutions, Inc. (MSI). Finally, the hybrid radar/tip timing NSMS software package and associated sensor hardware will be installed for use in the NASA Glenn spin pit test facility.

  3. Man-Induced Vibrations

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Hansen, Lars Pilegaard

    1994-01-01

    work has been done on the measurement of the exact load functions and related reponse analysis. A recent work using a spectral description has been performed by Per-Erik Erikson and includes a good literature survey. Bachmann and Ammann give a good overview of vibrations caused by human activity. Other...

  4. Vibration characteristics of ultrasonic complex vibration for hole machining

    Science.gov (United States)

    Asami, Takuya; Miura, Hikaru

    2012-05-01

    Complex vibration sources that use diagonal slits as a longitudinal-torsional vibration converter have been applied to ultrasonic motors, ultrasonic rock drilling, and ultrasonic welding. However, there are few examples of the application of these sources to ultrasonic machining in combination with an abrasive. Accordingly, a new method has been developed for machining of holes in brittle materials by using the ultrasonic longitudinal and torsional vibration of a hollow-type stepped horn with a diagonal slit vibration converter. In this paper, we compared vibration of a uniform rod and a hollow-type stepped horn, both with diagonal slits, when the conditions of the diagonal slits are constant.

  5. Two-phase flow induced parametric vibrations in structural systems

    International Nuclear Information System (INIS)

    Hara, Fumio

    1980-01-01

    This paper is divided into two parts concerning piping systems and a nuclear fuel pin system. The significant experimental results concerning the random vibration induced in an L-shaped pipe by air-water two-phase flow and the theoretical analysis of the vibration are described in the first part. It was clarified for the first time that the parametric excitation due to the periodic changes of system mass, centrifugal force and Coriolis force was the mechanism of exciting the vibration. Moreover, the experimental and theoretical analyses of the mechanism of exciting vibration by air-water two-phase flow in a straight, horizontal pipe were carried out, and the first natural frequency of the piping system was strongly related to the dominant frequency of void signals. The experimental results on the vibration of a nuclear fuel pin model in parallel air-water two-phase flow are reported in the latter part. The relations between vibrational strain variance and two-phase flow velocity or pressure fluctuation, and the frequency characteristics of vibrational strain variance were obtained. The theoretical analysis of the dynamic interaction between air-water two-phase flow and a fuel pin structure, and the vibrational instability of fuel pins in alternate air and water slugs or in large bubble flow are also reported. (Kako, I.)

  6. Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

    OpenAIRE

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2016-01-01

    A method of suppressing sound radiation to the far field of a near-field acoustic communication system using an evanescent sound field is proposed. The amplitude of the evanescent sound field generated from an infinite vibrating plate attenuates exponentially with increasing a distance from the surface of the vibrating plate. However, a discontinuity of the sound field exists at the edge of the finite vibrating plate in practice, which broadens the wavenumber spectrum. A sound wave radiates o...

  7. The effects of vibration-reducing gloves on finger vibration

    Science.gov (United States)

    Welcome, Daniel E.; Dong, Ren G.; Xu, Xueyan S.; Warren, Christopher; McDowell, Thomas W.

    2015-01-01

    Vibration-reducing (VR) gloves have been used to reduce the hand-transmitted vibration exposures from machines and powered hand tools but their effectiveness remains unclear, especially for finger protection. The objectives of this study are to determine whether VR gloves can attenuate the vibration transmitted to the fingers and to enhance the understanding of the mechanisms of how these gloves work. Seven adult male subjects participated in the experiment. The fixed factors evaluated include hand force (four levels), glove condition (gel-filled, air bladder, no gloves), and location of the finger vibration measurement. A 3-D laser vibrometer was used to measure the vibrations on the fingers with and without wearing a glove on a 3-D hand-arm vibration test system. This study finds that the effect of VR gloves on the finger vibration depends on not only the gloves but also their influence on the distribution of the finger contact stiffness and the grip effort. As a result, the gloves increase the vibration in the fingertip area but marginally reduce the vibration in the proximal area at some frequencies below 100 Hz. On average, the gloves reduce the vibration of the entire fingers by less than 3% at frequencies below 80 Hz but increase at frequencies from 80 to 400 Hz. At higher frequencies, the gel-filled glove is more effective at reducing the finger vibration than the air bladder-filled glove. The implications of these findings are discussed. Relevance to industry Prolonged, intensive exposure to hand-transmitted vibration can cause hand-arm vibration syndrome. Vibration-reducing gloves have been used as an alternative approach to reduce the vibration exposure. However, their effectiveness for reducing finger-transmitted vibrations remains unclear. This study enhanced the understanding of the glove effects on finger vibration and provided useful information on the effectiveness of typical VR gloves at reducing the vibration transmitted to the fingers. The new

  8. The Comparative Study of Vibration Control of Flexible Structure Using Smart Materials

    Directory of Open Access Journals (Sweden)

    Juntao Fei

    2010-01-01

    Full Text Available Considerable attention has been devoted to active vibration control using intelligent materials as PZT actuators. This paper presents results on active control schemes for vibration suppression of flexible steel cantilever beam with bonded piezoelectric actuators. The PZT patches are surface bonded near the fixed end of flexible steel cantilever beam. The dynamic model of the flexible steel cantilever beam is derived. Active vibration control methods: optimal PID control, strain rate feedback control (SRF, and positive position feedback control (PPF are investigated and implemented using xPC Target real-time system. Experimental results demonstrate that the SRF and PPF controls have better performance in suppressing the vibration of cantilever steel beam than the optimal PID control.

  9. Nonlinear modeling of tuned liquid dampers (TLDs) in rotating wind turbine blades for damping edgewise vibrations

    DEFF Research Database (Denmark)

    Zhang, Zili; Nielsen, Søren R. K.; Basu, Biswajit

    2015-01-01

    Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g. This facilit......Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g...... free-surface elevation equally well, the one-mode model can still be utilized for the design of TLD. Parametric optimization of the TLD is carried out based on the one-mode model, and the optimized damper effectively improves the dynamic response of wind turbine blades....

  10. Active vibration isolation through a Stewart platform with piezoelectric actuators

    Science.gov (United States)

    Wang, Chaoxin; Xie, Xiling; Chen, Yanhao; Zhang, Zhiyi

    2016-09-01

    A Stewart platform with piezoelectric actuators is presented for micro-vibration isolation. The Jacobian matrix of the Stewart platform, which reveals the relationship between the position/pointing of the payload and the extensions of the struts, is derived by the kinematic analysis and modified according to measured FRFs(frequency response function). The dynamic model of the Stewart platform is established by the FRF synthesis method to accommodate flexible modes of the platform. In active isolation, the LMS-based adaptive method is adopted and combined with the Jacobian matrix to suppress pure vibrations of the payload. Numerical simulations and experiments were conducted to prove vibration isolation performance of the Stewart platform subjected to periodical disturbances, and the results have demonstrated that considerable attenuations can be achieved.

  11. Low Head, Vortex Induced Vibrations River Energy Converter

    Energy Technology Data Exchange (ETDEWEB)

    Bernitsas, Michael B.; Dritz, Tad

    2006-06-30

    Vortex Induced Vibrations Aquatic Clean Energy (VIVACE) is a novel, demonstrated approach to extracting energy from water currents. This invention is based on a phenomenon called Vortex Induced Vibrations (VIV), which was first observed by Leonardo da Vinci in 1504AD. He called it ‘Aeolian Tones.’ For decades, engineers have attempted to prevent this type of vibration from damaging structures, such as offshore platforms, nuclear fuel rods, cables, buildings, and bridges. The underlying concept of the VIVACE Converter is the following: Strengthen rather than spoil vortex shedding; enhance rather than suppress VIV; harness rather than mitigate VIV energy. By maximizing and utilizing this unique phenomenon, VIVACE takes this “problem” and successfully transforms it into a valuable resource for mankind.

  12. Study of vibration and its effect on health of the motorcycle rider

    Directory of Open Access Journals (Sweden)

    Shivakumara BS

    2010-07-01

    Full Text Available The motorcycle riders are subjected to extreme vibrations due to the vibrations of its engine, improper structural design of the motorcycle and the bad road conditions. The literature review reveals that the vibrations are most hazardous to the health if it exceeds the limit. The experiments were conducted to measure the magnitude of the vibrations acting on the rider during motorcycle riding under various road conditions. Experimental values of accelerations and frequencies which are beyond permissible limits according to the literature confirm that vibration certainly affects health of the motorcycle rider

  13. Vibration Attenuation of Plate Using Multiple Vibration Absorbers

    Directory of Open Access Journals (Sweden)

    Zaman Izzuddin

    2014-07-01

    Full Text Available Vibrations are undesired phenomenon and it can cause harm, distress and unsettling influence to the systems or structures, for example, aircraft, automobile, machinery and building. One of the approach to limit this vibration by introducing passive vibration absorber attached to the structure. In this paper, the adequacy of utilizing passive vibration absorbers are investigated. The vibration absorber system is designed to minimize the vibration of a thin plate fixed along edges. The plate’s vibration characteristics, such as, natural frequency and mode shape are determined using three techniques: theoretical equations, finite element (FE analysis and experiment. The results demonstrate that the first four natural frequencies of fixed-fixed ends plate are 48, 121, 193 and 242 Hz, and these results are corroborated well with theoretical, FE simulation and experiment. The experiment work is further carried out with attached single and multiple vibration absorbers onto plate by tuning the absorber’s frequency to match with the excitation frequency. The outcomes depict that multiple vibration absorbers are more viable in lessening the global structural vibration.

  14. Suppression in the occurrence of stuttering due to current stimulation

    OpenAIRE

    能登谷, 晶子

    1999-01-01

    われわれのこれまでの研究から、末梢における吃音症状発生の主体は、声帯レベルでの機能異常によるものの可能性が強いことが推測されている。本研究は、吃音発生時の声門レベルの異常に焦点をて、低周波干渉電流が吃音発生の抑制に関与するかを検討することを目的としている。低周波干渉電流刺激療法が、理学療法の分野では末梢神経の伝導抑制作用を示し、その作用を利用して消炎・鎮痛療法があることは広く認められている。また、低周波による神経刺激実験で50Hz以上の電流が鎮痙的作用があることも知られている。3例の成人吃音患者を対象としたが、発話時のBlockと、身体の随伴症状が最も著しかった1例を対象に、上肢に電極を装着して電流刺激をした場合と、咽頭に電極を装着して電流刺激をした場合と、電流を流さない状態とで、文章音読時の吃音症状出現頻度について検討した。電流刺激装置は日本メデックス社の低周波刺激装置を用いた。咽頭への電流刺激方法は、星状神経節ブロック施行時の要領で行い、50-60Hz、5-10mAの電流を流した。また、distraction効果についても検討した。その結果、咽頭への電流刺激が吃音症状軽減に有...

  15. Rotor-to-stator rub vibration in centrifugal compressor

    Science.gov (United States)

    Gao, J. J.; Qi, Q. M.

    1985-01-01

    One example of excessive vibration encountered during loading of a centrifugal compressor train (H type compressor with HP casing) is discussed. An investigation was made of the effects of the dynamic load on the bearing stiffness and the rotor-bearing system critical speed. The high vibration occurred at a "threshold load," but the machine didn't run smoothly due to rubs even when it had passed through the threshold load. The acquisition and discussion of the data taken in the field as well as a description of the case history which utilizes background information to identify the malfunction conditions is presented. The analysis shows that the failures, including full reverse precession rub and exact one half subharmonic vibration, were caused by the oversize bearings and displacement of the rotor center due to foundation deformation and misalignment between gear shafts, etc. The corrective actions taken to alleviate excessive vibration and the problems which remain to be solved are also presented.

  16. Vibration reduction in a tilting rotor using centrifugal pendulum vibration absorbers

    Science.gov (United States)

    Shi, Chengzhi; Shaw, Steven W.; Parker, Robert G.

    2016-12-01

    This paper investigates vibration reduction in a rigid rotor with tilting, rotational, and translational motions using centrifugal pendulum vibration absorbers (CPVAs). A linearized vibration model is derived for the system consisting of the rotor and multiple sets of absorbers tuned to different orders. Each group of absorbers lies in a given plane perpendicular to the rotor rotation axis. Gyroscopic system modal analysis is applied to derive the steady-state response of the absorbers and the rotor to external, rotor-order, periodic forces and torques with frequency mΩ, where Ω is the mean rotor speed and m is the engine order (rotor-order). It is found that an absorber group with tuning order m is effective at reducing the rotor translational, tilting, and rotational vibrations, provided certain conditions are met. When the periodic force and torque are caused by N substructures that are equally spaced around the rotor, the rotor translational and tilting vibrations at order j are addressed by two absorber groups with tuning orders jN±1. In this case, the rotor rotational vibration at order j can be attenuated by an absorber group with tuning order jN. The results show how the response depends on the load amplitudes and order, the rotor speed, and design parameters associated with the sets of absorbers, most importantly, their tuning, mass, and plane of placement. In the ideal case with zero damping and exact tuning of the absorber sets, the vibrations can be eliminated for a range of loads over which the linearized model holds. The response for systems with detuned absorbers is also determined, which is relevant to applications where small detuning is employed due to robustness issues, and to allow for a larger range of operating loads over which the absorbers are effective. The system also exhibits undesirable resonances very close to these tuning conditions, an issue that is difficult to resolve and deserves further investigation.

  17. Real-time vibration compensation for large telescopes

    Science.gov (United States)

    Böhm, M.; Pott, J.-U.; Sawodny, O.; Herbst, T.; Kürster, M.

    2014-08-01

    We compare different strategies for minimizing the effects of telescope vibrations to the differential piston (optical pathway difference) for the Near-InfraRed/Visible Adaptive Camera and INterferometer for Astronomy (LINC-NIRVANA) at the Large Binocular Telescope (LBT) using an accelerometer feedforward compensation approach. We summarize, why this technology is important for LINC-NIRVANA, and also for future telescopes and already existing instruments. The main objective is outlining a solution for the estimation problem in general and its specifics at the LBT. Emphasis is put on realistic evaluation of the used algorithms in the laboratory, such that predictions for the expected performance at the LBT can be made. Model-based estimation and broad-band filtering techniques can be used to solve the estimation task, and the differences are discussed. Simulation results and measurements are shown to motivate our choice of the estimation algorithm for LINC-NIRVANA. The laboratory setup is aimed at imitating the vibration behaviour at the LBT in general, and the M2 as main contributor in particular. For our measurements, we introduce a disturbance time series which has a frequency spectrum comparable to what can be measured at the LBT on a typical night. The controllers' ability to suppress vibrations in the critical frequency range of 8-60 Hz is demonstrated. The experimental results are promising, indicating the ability to suppress differential piston induced by telescope vibrations by a factor of about 5 (rms), which is significantly better than any currently commissioned system.

  18. Vibration Spectrum Analysis for Indicating Damage on Turbine and Steam Generator Amurang Unit 1

    Directory of Open Access Journals (Sweden)

    Beny Cahyono

    2017-12-01

    Full Text Available Maintenance on machines is a mandatory asset management activity to maintain asset reliability in order to reduce losses due to failure. 89% of defects have random failure mode, the proper maintenance method is predictive maintenance. Predictive maintenance object in this research is Steam Generator Amurang Unit 1, which is predictive maintenance is done through condition monitoring in the form of vibration analysis. The conducting vibration analysis on Amurang Unit 1 Steam Generator is because vibration analysis is very effective on rotating objects. Vibration analysis is predicting the damage based on the vibration spectrum, where the vibration spectrum is the result of separating time-based vibrations and simplifying them into vibrations based on their frequency domain. The transformation of time-domain-wave into frequency-domain-wave is using the application of FFT, namely AMS Machinery. The measurement of vibration value is done on turbine bearings and steam generator of Unit 1 Amurang using Turbine Supervisory Instrument and CSI 2600 instrument. The result of this research indicates that vibration spectrum from Unit 1 Amurang Power Plant indicating that there is rotating looseness, even though the vibration value does not require the Unit 1 Amurang Power Plant to stop operating (shut down. This rotating looseness, at some point, can produce some indications that similar with the unbalance. In order to avoid more severe vibrations, it is necessary to do inspection on the bearings in the Amurang Unit 1 Power Plant.

  19. Experimental study of acoustic vibration in BWRs

    International Nuclear Information System (INIS)

    Kumagai, Kosuke; Someya, Satoshi; Okamoto, Koji

    2009-01-01

    In recent years, the power uprate of Boiling Water Reactors have been conducted at several existing power plants as a way to improve plant economy. In one of the power uprated plants (117.8% uprates) in the United States, the steam dryer breakages due to fatigue fracture occurred. It is conceivable that the increased steam flow passing through the branches caused a self-induced vibration with the propagation of sound wave into the steam-dome. The resonance among the structure, flow and the pressure fluctuation resulted in the breakages. To understand the basic mechanism of the resonance, previous researches were done by a point measurement of the pressure and by a phase averaged measurement of the flow, while it was difficult to detect the interaction among them by the conventional method. In this study, Dynamic Particle Image Velocimetry (PIV) System was applied to investigate the effect of sound on natural convection and forced convection. Dynamic PIV system is the newest entrant to the field of fluid flow measurement. Its paramount advantage is the instantaneous global evaluation of conditions over plane extended across the whole velocity field. Also, to evaluate the coupling between the acoustic wave and structure (simulated as tuning fork vibrator in this experiment), in the resonance frequency of tuning fork vibrator, fluid behavior and the motion of tuning fork vibrator are measured simultaneously. (author)

  20. Identification and reduction of piping-vibrations in plants

    International Nuclear Information System (INIS)

    Kerkhof, K.

    2012-01-01

    Safe operation, availability and lifetime assessment of piping systems are of utmost concern for plant operators. The use of tuned mass dampers is a rather new approach for reducing vibrations to avoid high cycle fatigue in a large chemical piping system. The investigated piping system is supported by a tall structure fixed at the base. As a result, the steel building stiffness decreases with height. Furthermore large piping-elbow forces act at the top of the building, which lead to large vibration amplitudes. Since both piping system and supporting structure exhibited these large vibration amplitudes, dampers or shock absorbers placed between them would prove ineffective. Therefore, special vibration absorbers were developed for such piping systems. The paper presents the design process, starting with an extensive system investigation up to the passive multi-axial vibration absorber design parameters. This includes: Laboratory tests with a mock-up pipe system, where the first design ideas for new passive vibration absorbers were investigated. Vibration measurements were carried out to investigate the current state of the vibration behaviour. The piping system was inspected; strain gauges were used to identify stress concentrations at welds and other notches due to ovalization. Finite element calculations were performed, first as a combined beam and shell model for the pipe without the support structure. A detailed model for the combined steel construction and pipe system was created. Model-updating was done to fit the calculated model to the experimental modal analysis data. Loading assumptions describing excitation forces from the mass flow were checked. Harmonic frequency analysis was performed. On the basis of these calculations design parameters for the passive vibration absorber were determined. Finally, a solution for the design of two passive vibration absorbers will be presented.

  1. Vibrational stability of graphene

    Directory of Open Access Journals (Sweden)

    Yangfan Hu

    2013-05-01

    Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.

  2. Pickin’ up good vibrations

    CERN Multimedia

    Katarina Anthony

    2015-01-01

    In preparation for the civil engineering work on the HL-LHC, vibration measurements were carried out at the LHC’s Point 1 last month. These measurements will help evaluate how civil engineering work could impact the beam, and will provide crucial details about the site’s geological make-up before construction begins.   A seismic truck at Point 1 generated wave-like vibrations measured by EN/MME. From carrying out R&D to produce state-of-the-art magnets to developing innovative, robust materials capable of withstanding beam impact, the HL-LHC is a multi-faceted project involving many groups and teams across CERN’s departments. It was in this framework that the project management mandated CERN's Mechanical and Materials Engineering (EN/MME) group to measure the propagation of vibrations around Point 1. Their question: can civil engineering work for the HL-LHC – the bulk of which is scheduled for LS2 – begin while the LHC is running? Alth...

  3. Electronic and vibrational spectroscopy and vibrationally mediated photodissociation of V+(OCO).

    Science.gov (United States)

    Citir, Murat; Altinay, Gokhan; Metz, Ricardo B

    2006-04-20

    Electronic spectra of gas-phase V+(OCO) are measured in the near-infrared from 6050 to 7420 cm(-1) and in the visible from 15,500 to 16,560 cm(-1), using photofragment spectroscopy. The near-IR band is complex, with a 107 cm(-1) progression in the metal-ligand stretch. The visible band shows clearly resolved vibrational progressions in the metal-ligand stretch and rock, and in the OCO bend, as observed by Brucat and co-workers. A vibrational hot band gives the metal-ligand stretch frequency in the ground electronic state nu3'' = 210 cm(-1). The OCO antisymmetric stretch frequency in the ground electronic state (nu1'') is measured by using vibrationally mediated photodissociation. An IR laser vibrationally excites ions to nu1'' = 1. Vibrationally excited ions selectively dissociate following absorption of a second, visible photon at the nu1' = 1 CO2, due to interaction with the metal. Larger blue shifts observed for complexes with fewer ligands agree with trends seen for larger V+(OCO)n clusters.

  4. Comparison of actuator designs for active vibration control of a gear pair system

    Science.gov (United States)

    Guan, Yuanhong; Li, Mingfeng; Lim, Teik C.; Shepard, W. Steve

    2002-07-01

    Four actuation concepts for the active suppression of gearbox housing mesh frequency vibrations caused by transmission error excitation from the gear pair system are modeled and compared by computing the required actuation force and amplifier power spectra. The proposed designs studied consist of (i) active inertial actuators positioned tangentially on the gear body to produce a pair of reactive force and moment, (ii) semi-active gear-shaft torsional coupling to provide tuned vibration isolation and suppression, (iii) active bearing vibration control to reduce vibration transmissibility, and (iv) active shaft transverse vibration control to suppress/tune gearbox casing or shaft response. Numerical simulations that incorporate a transmission error term as the primary excitation are performed using a finite element model of the geared rotor system (dynamic plant) constructed from beam and lumped mass/stiffness elements. Several key comparison criteria, including the required actuation effort, control robustness and implementation cost, are examined, and the advantages and disadvantages of each concept are discussed. Based on the simulated data, the active shaft transverse vibration scheme is identified as the most suitable approach for this application.

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

    Science.gov (United States)

    He, Qingbo; Wang, Xiangxiang; Zhou, Qiang

    2013-12-27

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

  6. Chatter suppression methods of a robot machine for ITER vacuum vessel assembly and maintenance

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huapeng; Wang, Yongbo, E-mail: yongbo.wang@lut.fi; Li, Ming; Al-Saedi, Mazin; Handroos, Heikki

    2014-10-15

    Highlights: •A redundant 10-DOF serial-parallel hybrid robot for ITER assembly and maintains is presented. •A dynamic model of the robot is developed. •A feedback and feedforward controller is presented to suppress machining vibration of the robot. -- Abstract: In the process of assembly and maintenance of ITER vacuum vessel (ITER VV), various machining tasks including threading, milling, welding-defects cutting and flexible hose boring are required to be performed from inside of ITER VV by on-site machining tools. Robot machine is a promising option for these tasks, but great chatter (machine vibration) would happen in the machining process. The chatter vibration will deteriorate the robot accuracy and surface quality, and even cause some damages on the end-effector tools and the robot structure itself. This paper introduces two vibration control methods, one is passive and another is active vibration control. For the passive vibration control, a parallel mechanism is presented to increase the stiffness of robot machine; for the active vibration control, a hybrid control method combining feedforward controller and nonlinear feedback controller is introduced for chatter suppression. A dynamic model and its chatter vibration phenomena of a hybrid robot is demonstrated. Simulation results are given based on the proposed hybrid robot machine which is developed for the ITER VV assembly and maintenance.

  7. Chatter suppression methods of a robot machine for ITER vacuum vessel assembly and maintenance

    International Nuclear Information System (INIS)

    Wu, Huapeng; Wang, Yongbo; Li, Ming; Al-Saedi, Mazin; Handroos, Heikki

    2014-01-01

    Highlights: •A redundant 10-DOF serial-parallel hybrid robot for ITER assembly and maintains is presented. •A dynamic model of the robot is developed. •A feedback and feedforward controller is presented to suppress machining vibration of the robot. -- Abstract: In the process of assembly and maintenance of ITER vacuum vessel (ITER VV), various machining tasks including threading, milling, welding-defects cutting and flexible hose boring are required to be performed from inside of ITER VV by on-site machining tools. Robot machine is a promising option for these tasks, but great chatter (machine vibration) would happen in the machining process. The chatter vibration will deteriorate the robot accuracy and surface quality, and even cause some damages on the end-effector tools and the robot structure itself. This paper introduces two vibration control methods, one is passive and another is active vibration control. For the passive vibration control, a parallel mechanism is presented to increase the stiffness of robot machine; for the active vibration control, a hybrid control method combining feedforward controller and nonlinear feedback controller is introduced for chatter suppression. A dynamic model and its chatter vibration phenomena of a hybrid robot is demonstrated. Simulation results are given based on the proposed hybrid robot machine which is developed for the ITER VV assembly and maintenance

  8. Piezoelectric actuators in the active vibration control system of journal bearings

    Science.gov (United States)

    Tůma, J.; Šimek, J.; Mahdal, M.; Pawlenka, M.; Wagnerova, R.

    2017-07-01

    The advantage of journal hydrodynamic bearings is high radial load capacity and operation at high speeds. The disadvantage is the excitation of vibrations, called an oil whirl, after crossing a certain threshold of the rotational speed. The mentioned vibrations can be suppressed using the system of the active vibration control with piezoactuators which move the bearing bushing. The motion of the bearing bushing is controlled by a feedback controller, which responds to the change in position of the bearing journal which is sensed by a pair of capacitive sensors. Two stacked linear piezoactuators are used to actuate the position of the bearing journal. This new bearing enables not only to damp vibrations but also serves to maintain the desired bearing journal position with an accuracy of micrometers. The paper will focus on the effect of active vibration control on the performance characteristics of the journal bearing.

  9. Failure analysis of a vibration isolator used in launch vehicle applications

    Directory of Open Access Journals (Sweden)

    S.V.S. Narayana Murty

    2015-04-01

    Full Text Available Vibration isolators are used in launch vehicles to protect sensitive electronic equipments from the rigors of flight structural vibrations during the lift-off and ascent phase. Failure of one such vibration isolator made of AISI 304 is reported in the present study after ground level testing has been completed. The vibration isolator had a crack of length approximately 42 mm at the fore end corner. Detailed optical and scanning electron microscopy was conducted on the failed vibration isolator to understand the reasons for cracking. Finally, it was concluded that micro cracks formed during the deep drawing operation (due to large strains at the fore end corner propagated during vibration testing resulting in the failure of the body of the vibration isolator.

  10. Amplitude control of the track-induced self-excited vibration for a maglev system.

    Science.gov (United States)

    Zhou, Danfeng; Li, Jie; Zhang, Kun

    2014-09-01

    The Electromagnet Suspension (EMS) maglev train uses controlled electromagnetic forces to achieve suspension, and self-excited vibration may occur due to the flexibility of the track. In this article, the harmonic balance method is applied to investigate the amplitude of the self-excited vibration, and it is found that the amplitude of the vibration depends on the voltage of the power supplier. Based on this observation, a vibration amplitude control method, which controls the amplitude of the vibration by adjusting the voltage of the power supplier, is proposed to attenuate the vibration. A PI controller is designed to control the amplitude of the vibration at a given level. The effectiveness of this method shows a good prospect for its application to commercial maglev systems. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

  11. Study of the Transverse Vibration for The Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Hamza Madjid Berrabah

    2016-08-01

    Full Text Available This study concerns the dynamic behavior of composite beams gradually evaluated through the thickness materials. Our work is devoted to the analysis of natural frequencies of composite beams FGM used in building structures in civil engineering often subjected to vibration loads due to earthquakes. The vibration characteristics of specific beams such as free and orthotropic fixed beams are studied without including deformation due to shear and rotational inertia. We introduce the effects of transverse deformation due to shear and rotational inertia for the accurate prediction of normal frequencies. An application to carbon nanotubes was investigated.

  12. Adaptive-passive vibration control systems for industrial applications

    Science.gov (United States)

    Mayer, D.; Pfeiffer, T.; Vrbata, J.; Melz, T.

    2015-04-01

    Tuned vibration absorbers have become common for passive vibration reduction in many industrial applications. Lightly damped absorbers (also called neutralizers) can be used to suppress narrowband disturbances by tuning them to the excitation frequency. If the resonance is adapted in-operation, the performance of those devices can be significantly enhanced, or inertial mass can be decreased. However, the integration of actuators, sensors and control electronics into the system raises new design challenges. In this work, the development of adaptive-passive systems for vibration reduction at an industrial scale is presented. As an example, vibration reduction of a ship engine was studied in a full scale test. Simulations were used to study the feasibility and evaluate the system concept at an early stage. Several ways to adjust the resonance of the neutralizer were evaluated, including piezoelectric actuation and common mechatronic drives. Prototypes were implemented and tested. Since vibration absorbers suffer from high dynamic loads, reliability tests were used to assess the long-term behavior under operational conditions and to improve the components. It was proved that the adaptive systems are capable to withstand the mechanical loads in an industrial application. Also a control strategy had to be implemented in order to track the excitation frequency. The most mature concepts were integrated into the full scale test. An imbalance exciter was used to simulate the engine vibrations at a realistic level experimentally. The neutralizers were tested at varying excitation frequencies to evaluate the tracking capabilities of the control system. It was proved that a significant vibration reduction is possible.

  13. Study on a novel type of CFBG vibration sensor

    Science.gov (United States)

    Nan, Qiuming

    2009-07-01

    Vibration monitoring is one of important technology means for large electromechanical equipment's safety-alert and malfunction-diagnosis, and also a hot problem studied for a long time at home and abroad. Vibration sensor is key part for the technology means, but traditional electromagnetic vibration sensors are restricted for use in the field due to their weak competence to anti-electromagnetic interference. It is inevitable and imminent to develop novel type of vibration sensors instead of them. Aiming at the above-mentioned demand, the authors in the paper fabricate a push-pull type of chirped fiber Bragg grating (CFBG) vibration sensor based on matching demodulation. The authors, at first, set up mechanical model of the sensor, then analyze the principle of CFBG matching demodulation and get the relation between acceleration and output voltage at last. The sensor has such functions as anti-electromagnetic interference, temperature self-compensation and combining vibration sensing and dynamic wavelength demodulation. Moreover, some experiments are done to study its sensing properties and the results indicate that its sensitivity is 369mv/g, linearity degree is over 99.9%, repeatability is superior to 2%, measurement bandwidth is from 10Hz to 400Hz, acceleration measurement range is 8g, and the minimal cross-axis anti-interference is 30dB. To sum up, the sensor is competently used for monitoring the vibration of large electromechanical equipment.

  14. Attenuation of cryocooler induced vibration in spaceborne infrared payloads

    Science.gov (United States)

    Veprik, A.; Twitto, A.

    2014-01-01

    Recent advancement of operational responsive space programs calls for a development of compact, reliable, low power and vibration free cryogenic cooling for sophisticated infrared payloads. The refrigeration in a typical closed cycle split Stirling linear cryocooler is achieved by a cyclic compression and expansion of a gaseous working agent due to a synchronized reciprocation of electro-dynamically and pneumatically actuated compressor and expander pistons. Attenuation of the cryocooler induced vibration usually relies on the concept of actively assisted momentum cancellation. In a typical dual-piston compressor this objective is achieved by actively synchronizing the motion of oppositely moving piston assemblies; a typical single-piston expander may be counterbalanced by a motorized counter-balancer. The above approach produces complexity, weight, size, high incurred costs and affects reliability. The authors analyze the case of passive attenuation the vibration export induced by the split Stirling linear cryocooler comprised of inline mounted single-piston compressor and expander. Placement of all the moving components onto a common axis results in a single axis consolidation of vibration export and enables use of single tuned dynamic absorber and low frequency vibration mount. From theoretical analysis and full-scale testing, the performance of such vibration protection arrangement is similar to known systems of active vibration cancellation.

  15. Vibration Antiresonance Design for a Spacecraft Multifunctional Structure

    Directory of Open Access Journals (Sweden)

    Dong-Xu Li

    2017-01-01

    Full Text Available Spacecraft must withstand rigorous mechanical environment experiences such as acceleration, noise, vibration, and shock during the process of launching, satellite-vehicle separation, and so on. In this paper, a new spacecraft multifunctional structure concept designed by us is introduced. The multifunctional structure has the functions of not only load bearing, but also vibration reduction, energy source, thermal control, and so on, and we adopt a series of viscoelastic parts as connections between substructures. Especially in this paper, a vibration antiresonance design method is proposed to realize the vibration reduction. The complex zero-point equations of the vibration system are firstly established, and then the vibration antiresonance design for the system is achieved. For solving the difficulties due to viscoelastic characteristics of the connecting parts, we present the determining formulas to obtain the structural parameters, so that the complex zero-point equations can be satisfied. Numerical simulation and ground experiment demonstrate the correctness and effectiveness of the proposed method. This method can solve the structural vibration control problem under the function constraints of load bearing and energy supplying and will expand the performance of spacecraft functional modules.

  16. Suppression of stratified explosive interactions

    Energy Technology Data Exchange (ETDEWEB)

    Meeks, M.K.; Shamoun, B.I.; Bonazza, R.; Corradini, M.L. [Wisconsin Univ., Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics

    1998-01-01

    Stratified Fuel-Coolant Interaction (FCI) experiments with Refrigerant-134a and water were performed in a large-scale system. Air was uniformly injected into the coolant pool to establish a pre-existing void which could suppress the explosion. Two competing effects due to the variation of the air flow rate seem to influence the intensity of the explosion in this geometrical configuration. At low flow rates, although the injected air increases the void fraction, the concurrent agitation and mixing increases the intensity of the interaction. At higher flow rates, the increase in void fraction tends to attenuate the propagated pressure wave generated by the explosion. Experimental results show a complete suppression of the vapor explosion at high rates of air injection, corresponding to an average void fraction of larger than 30%. (author)

  17. Experiment studies of fuel rod vibration in coolant flow for substantiation of vibration stability of fuel rods with no fretting-wear

    International Nuclear Information System (INIS)

    Egorov, Yu. V.; Afanasiev, A. V.; Makarov, V. V.; Matvienko, I. V.

    2013-01-01

    For substantiation of vibration stability it is necessary to determine the ultimate permissible vibration levels which do not cause fretting, to compare them with the level of fuel rod vibration caused by coolant flow. Another approach is feasible if there is experience of successful operation of FA-prototypes. In this case in order to justify vibration stability it may be sufficient to demonstrate that the new element does not cause increased vibration of the fuel rod. It can be done by comparing the levels of hydro-dynamic fuel rod vibration and FA new designs. Program of vibration tests of TVS-2M model included studies of forced oscillations of 12 fuel rods in the coolant flow in the spans containing intensifiers, in the reference span without intensifiers, in the lower spans with assembled ADF and after its disassembly. The experimental results for TVS-2M show that in the spans with intensifier «Sector run» the level of movements is 6% higher on the average than in the span without intensifiers, in the spans with intensifier «Eddy» it is 2% higher. The level of fuel rod vibration movements in the spans with set ADF is 2 % higher on the average than without ADF. During the studies of TVS-KVADRAT fuel rod vibration, the following tasks were solved: determination of acceleration of the middle of fuel rod spans at vibration excited due to hydrodynamics; determination of influence of coolant thermal- hydraulic parameters (temperature, flowrate, dynamic pressure) on fuel rod vibration response; determination of influence of span lengths on the vibration level. Conclusions: 1) The vibration tests of the full-scale model of TVS-2M in the coolant flow showed that the new elements of TVS-2M design (intensifiers of heat exchange and ADF) are not the source of fuel rod increased vibration. Considering successful operation of similar fuel rod spans in the existing TVS-2M design, vibration stability of TVS-2M fuel rods with new elements is ensured on the mechanism of

  18. A study on the evaluation of vibration effect and the development of vibration reduction method for Wolsung unit 1 main steam piping

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyun; Kim, Yeon Whan [Korea Electric Power Corp. (KEPCO), Taejon (Korea, Republic of). Research Center; Kim, Tae Ryong; Park, Jin Ho [Korea Atomic Energy Research Inst., Daeduk (Korea, Republic of)

    1996-08-01

    The main steam piping of nuclear power plant which runs between steam generator and high pressure turbine has been experienced to have a severe effect on the safe operation of the plant due to the vibration induced by the steam flowing inside the piping. The imposed cyclic loads by the vibration could result in the degradation of the related structures such as connection parts between main instruments, valves, pipe supports and building. The objective of the study is to reduce the vibration level of Wolsung nuclear power plant unit 1 main steam pipeline by analyzing vibration characteristics of the piping, identifying sources of the vibration and developing a vibration reduction method .The location of the maximum vibration is piping between the main steam header and steam chest .The stress level was found to be within the allowable limit .The main vibration frequency was found to be 4{approx}6 Hz which is the same as the natural frequency from model test .A vibration reduction method using pipe supports of energy absorbing type(WEAR)is selected .The measured vibration level after WEAR installation was reduced about 36{approx}77% in displacement unit (author). 36 refs., 188 figs.

  19. Lattice Vibrations in Chlorobenzenes:

    DEFF Research Database (Denmark)

    Reynolds, P. A.; Kjems, Jørgen; White, J. W.

    1974-01-01

    Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K...... was applied in order to correct for anharmonic effects. Calculations based on the atom‐atom model for van der Waals' interaction and on general potential parameters for the aromatic compounds agree reasonably well with the experimental observations. There is no substantial improvement in fit obtained either...

  20. Digital analysis of vibrations

    International Nuclear Information System (INIS)

    Bohnstedt, H.J.; Walter, G.

    1982-01-01

    Vibrational measurements, e.g. on turbomachinery, can be evaluated rapidly and economically with the aid of a combination of the following instruments: a desk-top computer, a two-channel vector filter and a FFT spectral analyzer. This equipment combination is available within the Allianz Centre for Technology and has also been used for mobile, on-site investigations during the last year. It enables calculation and display of time functions, kinetic shaft orbits, displacement diagrams. Bode plots, polar-coordinate plots, cascade diagrams and histograms. (orig.) [de

  1. Quantum dynamics of vibrational excitations and vibrational charge ...

    Indian Academy of Sciences (India)

    Administrator

    Dedicated to the memory of the late Professor S K Rangarajan. *For correspondence. Quantum dynamics of vibrational excitations and vibrational charge transfer processes in H. +. + O2 collisions at collision energy 23 eV. †. SAIESWARI AMARAN# and SANJAY KUMAR*. Department of Chemistry, Indian Institute of ...

  2. Off-axis Modal Active Vibration Control Of Rotational Vibrations

    NARCIS (Netherlands)

    Babakhani, B.; de Vries, Theodorus J.A.; van Amerongen, J.

    Collocated active vibration control is an effective and robustly stable way of adding damping to the performance limiting vibrations of a plant. Besides the physical parameters of the Active Damping Unit (ADU) containing the collocated actuator and sensor, its location with respect to the

  3. [Farmacological effect of retabolil on aldosterone level and arterial pressure in rats under the action of vibrations].

    Science.gov (United States)

    Obut, T A; Ovsiukova, M V; Egorova, S A; Érdynieva, T A; Dement'eva, T Iu; Obut, E T

    2014-01-01

    The experiments were performed on male rats, which were subjected to single and multiply repeated vibrations (low-frequency, horizontal, high-amplitude) analogous to the action of motor transport vibrations. It is established that the administration of retabolil produces a hypotensive effect and blocks the vibration-induced increase in the level of hypertensive hormone aldosterone. Under conditions of the multiply repeated action of vibrations, both effects were realized via micro-opioid receptors. In the case of a single action, these receptors were only involved in a hypotensive effect but not mediated in aldosterone suppression. Both these effects were absent in the control group of animals (not subjected to vibrations). Therefore, retabolil can be used as a hypotensive and aldosterone-blocking drug for vibration-induced hypertension in animals and, probably, in humans.

  4. Vibration Response of Multi Storey Building Using Finite Element Modelling

    Science.gov (United States)

    Chik, T. N. T.; Zakaria, M. F.; Remali, M. A.; Yusoff, N. A.

    2016-07-01

    Interaction between building, type of foundation and the geotechnical parameter of ground may trigger a significant effect on the building. In general, stiffer foundations resulted in higher natural frequencies of the building-soil system and higher input frequencies are often associated with other ground. Usually, vibrations transmitted to the buildings by ground borne are often noticeable and can be felt. It might affect the building and become worse if the vibration level is not controlled. UTHM building is prone to the ground borne vibration due to closed distance from the main road, and the construction activities adjacent to the buildings. This paper investigates the natural frequency and vibration mode of multi storey office building with the presence of foundation system and comparison between both systems. Finite element modelling (FEM) package software of LUSAS is used to perform the vibration analysis of the building. The building is modelled based on the original plan with the foundation system on the structure model. The FEM results indicated that the structure which modelled with rigid base have high natural frequency compare to the structure with foundation system. These maybe due to soil structure interaction and also the damping of the system which related to the amount of energy dissipated through the foundation soil. Thus, this paper suggested that modelling with soil is necessary to demonstrate the soil influence towards vibration response to the structure.

  5. Damping of edgewise vibration in wind turbine blades by means of circular liquid dampers

    DEFF Research Database (Denmark)

    Basu, Biswajit; Zhang, Zili; Nielsen, Søren R.K.

    2016-01-01

    centrifugal acceleration. This centrifugal acceleration makes the use of this kind of oscillatory liquid damper feasible with a small mass ratio to effectively suppress edgewise vibrations. A reduced 2-DOF non-linear model is used for tuning the CLCD attached to a rotating wind turbine blade, ignoring......MW wind turbine machine indicate that the CLCD at an optimal tuning can effectively suppress the dynamic response of wind turbine blades. Copyright © 2015 John Wiley & Sons, Ltd....

  6. Calculation of Vibrational Spectra of p-Ethylbenzenesulfonic Acid Hydrates

    Science.gov (United States)

    Zelenkovskii, V. M.; Bezyazychnaya, T. V.; Soldatov, V. S.

    2013-09-01

    Quantum-chemical calculations of vibrational spectra of the sulfonated ion-exchanger model p-ethylbenzenesulfonic acid hydrated by 1-10 water molecules and its dimer were calculated by the non-empirical SCF MO LCAO method with the 6-31G(d) basis set. The calculated results were compared with experimental IR and Raman spectra of sulfonated ion exchangers. The infl uence of hydration on the vibrational frequencies of functional groups in the ion exchangers was analyzed. It was shown that the sulfonic acid was completely dissociated if three and more water molecules per functional group were present. Bands near 1130 cm-1 were due to S-O-H bending vibrations in the absence of water molecules and C-S-O-H3O combination vibrations with 3-6 water molecules per sulfonic acid.

  7. METHOD FOR DETERMINATION OF ROTATION CENTER IN VIBRATING OBJECT

    Directory of Open Access Journals (Sweden)

    I. P. Kauryha

    2016-01-01

    Full Text Available Linear piezoelectric gauges, eddy current transducers and other control and measuring devices have been widely applied for vibration diagnostics of objects in industry. Methods based on such gauges and used for measuring angular and linear vibrations do not provide the possibility to assess a rotation center or point angle of an object. Parasitic oscillations may occur during rotor rotation and in some cases the oscillations are caused by dis-balance. The known methods for measuring angular and linear vibrations make it possible to detect the phenomenon and they do not provide information for balancing of the given object. For this very reason the paper describes a method for obtaining instantaneous rotation center in the vibrating object. It allows to improve informational content of the measurements owing to obtaining additional data on position of object rotation center. The obtained data can be used for balancing of a control object. Essence of the given method is shown by an example of piezoelectric gauges of linear vibrations. Two three-axial gauges are fixed to the investigated object. Then gauge output signals are recalculated in angular vibrations of the object (for this purpose it is necessary to know a distance between gauges. Further projection positions of the object rotation center are determined on three orthogonal planes. Instantaneous rotation center is calculated according to the position of one of the gauges. The proposed method permits to obtain data on linear and angular vibrations and rotation center position of the vibrating object using one system of linear gauge. Possibilities of object diagnostics are expanded due to increase in number of determined parameters pertaining to object moving. The method also makes it possible to reduce material and time expenses for measurement of an angular vibration component. 

  8. Gas Bubble Dynamics under Mechanical Vibrations

    Science.gov (United States)

    Mohagheghian, Shahrouz; Elbing, Brian

    2017-11-01

    The scientific community has a limited understanding of the bubble dynamics under mechanical oscillations due to over simplification of Navier-Stockes equation by neglecting the shear stress tensor and not accounting for body forces when calculating the acoustic radiation force. The current work experimental investigates bubble dynamics under mechanical vibration and resulting acoustic field by measuring the bubble size and velocity using high-speed imaging. The experimental setup consists of a custom-designed shaker table, cast acrylic bubble column, compressed air injection manifold and an optical imaging system. The mechanical vibrations resulted in accelerations between 0.25 to 10 times gravitational acceleration corresponding to frequency and amplitude range of 8 - 22Hz and 1 - 10mm respectively. Throughout testing the void fraction was limited to definition of Bjerknes force in combination with Rayleigh-Plesset equation. Physical behavior of the system was capture and classified. Bubble size, velocity as well as size and spatial distribution will be presented.

  9. Reduction of personnel vibration hazards in underground coal mines

    Energy Technology Data Exchange (ETDEWEB)

    Oh, X.; Middlin, A. (Vipac Engineers and Scientists Ltd. (Australia))

    1991-03-01

    Whole-Body Vibration (WBV) due to the 'rough ride' in vehicles is a major source of back and neck injury in underground coal mines. Hand-Arm Vibration (HAV) from hand held equipment can also cause long term health damage. Surveys in three collieries in NSW have been conducted to measure the vibration levels to which miners are being exposed and to assess them according to the two relevant Australian Standards namely AS2670 and AS2763. WBV results indicated that shock loadings must be the source of back and neck injuries that are occurring due to 'rough ride'. Existing off-the-shelf seat suspensions were demonstrated to be inadequate for providing effective shock isolation, due to them being prone to bottoming out under rough conditions, and due their scissor action mechanism becoming rapidly jammed by dirt to the point where they become rigid. Commercially available seats were evaluated and tested on a hydraulic shaker, but none proved able to provide the required vibration isolation. A prototype seat suspension was developed by Vipac. This suspension was shaker tested and trialled in low loaders at two collieries. The seat proved capable of cushioning shock loads without bottoming out, as well as attenuating the dominant vibration at 2.5 Hz and higher. This suspension with encapsulated mechanism could be readily adapted to suit a wide range of underground vehicles. The HAV survey results identified the Wombat roof-bolter as the major item requiring vibration level reductions. Extensive investigations resulted in the design of a prototype vibration isolated handle. During field tests this prototype handle reduced the HAV level such that the Exposure Time (10th percentile) was increased from 7 to 11.5 years. Guidelines are presented for additional developments which would further improve this performance and result in a handle design suitable for retrofitting to existing roof bolters.

  10. 14 CFR 33.33 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Design and Construction; Reciprocating Aircraft Engines § 33.33 Vibration. The... vibration and without imparting excessive vibration forces to the aircraft structure. ...

  11. Melt Stirring by Horizontal Crucible Vibration

    Science.gov (United States)

    Wolf, M. F.; Elwell, D.; Feigelson, R. S.

    1985-01-01

    Horizontal vibration suggested as technique for more effective stirring of melts in crystal-growth apparatus. Vibrational technique may replace accelerated crucible rotation. Potential superiority of vibrational technique shown by preliminary experiments in which ink stirred into water.

  12. Psychopathology and Thought Suppression: A Quantitative Review

    Science.gov (United States)

    Magee, Joshua C.; Harden, K. Paige; Teachman, Bethany A.

    2012-01-01

    Recent theories of psychopathology have suggested that thought suppression intensifies the persistence of intrusive thoughts, and proposed that difficulty with thought suppression may differ between groups with and without psychopathology. The current meta-analytic review evaluates empirical evidence for difficulty with thought suppression as a function of the presence and specific type of psychopathology. Based on theoretical proposals from the psychopathology literature, diagnosed and analogue samples were expected to show greater recurrence of intrusive thoughts during thought suppression attempts than non-clinical samples. However, results showed no overall differences in the recurrence of thoughts due to thought suppression between groups with and without psychopathology. There was, nevertheless, variation in the recurrence of thoughts across different forms of psychopathology, including relatively less recurrence during thought suppression for samples with symptoms of Obsessive-Compulsive Disorder, compared to non-clinical samples. However, these differences were typically small and provided only mixed support for existing theories. Implications for cognitive theories of intrusive thoughts are discussed, including proposed mechanisms underlying thought suppression. PMID:22388007

  13. Prediction of vibration level in tunnel blasting; Tonneru kusshin happa ni yotte reiki sareru shindo no reberu yosoku ho

    Energy Technology Data Exchange (ETDEWEB)

    Hirata, A. [Kumamoto Industries Univ, Kumamoto (Japan); Yamamoto, M. [Asahi Chemical Industry Co. Ltd., Tokyo (Japan); Inaba, C. [Nishimatsu Construction Co. Ltd., Kanagawa (Japan); Kaneko, K. [Hokkaido Univ (Japan)

    1997-08-01

    For avoiding the generation of public hazard due to ground vibration causes by blasting in tunneling, it is important to devise a blasting method for ensuring the level of the ground vibration caused thereby under a limit, and an exact predication of ground vibration before blasting is desirable. In this study, the characteristics of the ground vibration caused by tunnel blasting are analyzed, and a summary of amplitude spectra calculating method is described. A theoretical analysis method for predicting the vibration level is proposed based on spectrum-multiplicative method. Vibration caused by multistage blasting in tunneling is most strong and deemed as important. When observing the process of elastic wave motion caused by multistage blasting being measured, the process can be divided into three element processes in frequency area as vibration source spectrum, transmission attenuation spectrum and frequency response function vibrating test, and, with the multiplication of them, the amplitude spectra at an observation portion can be estimated. 12 refs., 12 figs.

  14. Menstrual suppression for adolescents.

    Science.gov (United States)

    Altshuler, Anna Lea; Hillard, Paula J Adams

    2014-10-01

    The purpose of this review is to highlight the recent literature and emerging data describing clinical situations in which menstrual suppression may improve symptoms and quality of life for adolescents. A variety of conditions occurring frequently in adolescents and young adults, including heavy menstrual bleeding, and dysmenorrhea as well as gynecologic conditions such as endometriosis and pelvic pain, can safely be improved or alleviated with appropriate menstrual management. Recent publications have highlighted the efficacy and benefit of extended cycle or continuous combined oral contraceptives, the levonorgestrel intrauterine device, and progestin therapies for a variety of medical conditions. This review places menstrual suppression in an historical context, summarizes methods of hormonal therapy that can suppress menses, and reviews clinical conditions for which menstrual suppression may be helpful.

  15. Cryogenic Acoustic Suppression Testing

    Data.gov (United States)

    National Aeronautics and Space Administration — A proof-of-concept method utilizing a cryogenic fluid for acoustic suppression in rocket engine testing environments will be demonstrated. It is hypothesized that...

  16. Sodium fire suppression

    International Nuclear Information System (INIS)

    Malet, J.C.

    1979-01-01

    Ignition and combustion studies have provided valuable data and guidelines for sodium fire suppression research. The primary necessity is to isolate the oxidant from the fuel, rather than to attempt to cool the sodium below its ignition temperature. Work along these lines has led to the development of smothering tank systems and a dry extinguishing powder. Based on the results obtained, the implementation of these techniques is discussed with regard to sodium fire suppression in the Super-Phenix reactor. (author)

  17. Increased suppression of negative and positive emotions in major depression.

    Science.gov (United States)

    Beblo, Thomas; Fernando, Silvia; Klocke, Sabrina; Griepenstroh, Julia; Aschenbrenner, Steffen; Driessen, Martin

    2012-12-10

    Patients with major depression (MDD) show increased suppression of negative emotions. Emotion suppression is related to depressive symptoms such as depressive mood and anhedonia. It is not clear whether MDD patients also suppress positive emotions. In the present study we aim to investigate suppression of both negative and positive emotions in MDD patients as well as the relation between emotion suppression and depressive symptoms. In addition, we suggest that emotion suppression might be associated with fear of emotions. 39 MDD patients and 41 matched healthy control subjects were investigated for emotion suppression and fear of emotions with the Emotion Acceptance Questionnaire (EAQ). In addition, we applied additional questionnaires to validate emotion suppression findings and to assess depressive symptoms. MDD patients reported increased suppression of both negative and positive emotions. Suppression of negative and positive emotions was related to depressive symptoms. Patients also reported more fear of emotions than healthy subjects and this fear was related to emotion suppression in both study samples. Due to the cross-sectional and correlational study design, causal directions between the variables tested cannot be stated. Fear of emotion might be one reason why MDD patients suppress emotions. With regard to positive emotions, our results strongly suggest that therapeutic approaches should not only encourage patients to participate in potentially enjoyable situations but that patients may also benefit from practicing the allowance of pleasant emotions. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Robust and fast schemes in broadband active noise and vibration control

    NARCIS (Netherlands)

    Fraanje, P.R.

    2004-01-01

    This thesis presents robust and fast active control algorithms for the suppression of broadband noise and vibration disturbances. Noise disturbances, e.g., generated by engines in airplanes and cars or by air ow, can be reduced by means of passive or active methods.

  19. Intracellular recording from a spider vibration receptor.

    Science.gov (United States)

    Gingl, Ewald; Burger, Anna-M; Barth, Friedrich G

    2006-05-01

    The present study introduces a new preparation of a spider vibration receptor that allows intracellular recording of responses to natural mechanical or electrical stimulation of the associated mechanoreceptor cells. The spider vibration receptor is a lyriform slit sense organ made up of 21 cuticular slits located on the distal end of the metatarsus of each walking leg. The organ is stimulated when the tarsus receives substrate vibrations, which it transmits to the organ's cuticular structures, reducing the displacement to about one tenth due to geometrical reasons. Current clamp recording was used to record action potentials generated by electrical or mechanical stimuli. Square pulse stimulation identified two groups of sensory cells, the first being single-spike cells which generated only one or two action potentials and the second being multi-spike cells which produced bursts of action potentials. When the more natural mechanical sinusoidal stimulation was applied, differences in adaptation rate between the two cell types remained. In agreement with prior extracellular recordings, both cell types showed a decrease in the threshold tarsus deflection with increasing stimulus frequency. Off-responses to mechanical stimuli have also been seen in the metatarsal organ for the first time.

  20. Modelling chaotic vibrations using NASTRAN

    Science.gov (United States)

    Sheerer, T. J.

    1993-01-01

    Due to the unavailability and, later, prohibitive cost of the computational power required, many phenomena in nonlinear dynamic systems have in the past been addressed in terms of linear systems. Linear systems respond to periodic inputs with periodic outputs, and may be characterized in the time domain or in the frequency domain as convenient. Reduction to the frequency domain is frequently desireable to reduce the amount of computation required for solution. Nonlinear systems are only soluble in the time domain, and may exhibit a time history which is extremely sensitive to initial conditions. Such systems are termed chaotic. Dynamic buckling, aeroelasticity, fatigue analysis, control systems and electromechanical actuators are among the areas where chaotic vibrations have been observed. Direct transient analysis over a long time period presents a ready means of simulating the behavior of self-excited or externally excited nonlinear systems for a range of experimental parameters, either to characterize chaotic behavior for development of load spectra, or to define its envelope and preclude its occurrence.

  1. Vibration response of misaligned rotors

    Science.gov (United States)

    Patel, Tejas H.; Darpe, Ashish K.

    2009-08-01

    Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.

  2. The high level vibration test program

    International Nuclear Information System (INIS)

    Hofmayer, C.H.; Curreri, J.R.; Park, Y.J.; Kato, W.Y.; Kawakami, S.

    1989-01-01

    As part of cooperative agreements between the US and Japan, tests have been performed on the seismic vibration table at the Tadotsu Engineering Laboratory of Nuclear Power Engineering Test Center (NUPEC) in Japan. The objective of the test program was to use the NUPEC vibration table to drive large diameter nuclear power piping to substantial plastic strain with an earthquake excitation and to compare the results with state-of-the-art analysis of the problem. The test model was subjected to a maximum acceleration well beyond what nuclear power plants are designed to withstand. A modified earthquake excitation was applied and the excitation level was increased carefully to minimize the cumulative fatigue damage due to the intermediate level excitations. Since the piping was pressurized, and the high level earthquake excitation was repeated several times, it was possible to investigate the effects of ratchetting and fatigue as well. Elastic and inelastic seismic response behavior of the test model was measured in a number of test runs with an increasing excitation input level up to the limit of the vibration table. In the maximum input condition, large dynamic plastic strains were obtained in the piping. Crack initiation was detected following the second maximum excitation run. Crack growth was carefully monitored during the next two additional maximum excitation runs. The final test resulted in a maximum crack depth of approximately 94% of the wall thickness. The HLVT (high level vibration test) program has enhanced understanding of the behavior of piping systems under severe earthquake loading. As in other tests to failure of piping components, it has demonstrated significant seismic margin in nuclear power plant piping

  3. Customized shaping of vibration modes by acoustic metamaterial synthesis

    Science.gov (United States)

    Xu, Jiawen; Li, Shilong; Tang, J.

    2018-04-01

    Acoustic metamaterials have attractive potential in elastic wave guiding and attenuation over specific frequency ranges. The vast majority of related investigations are on transient waves. In this research we focus on stationary wave manipulation, i.e., shaping of vibration modes. Periodically arranged piezoelectric transducers shunted with inductive circuits are integrated to a beam structure to form a finite-length metamaterial beam. We demonstrate for the first time that, under a given operating frequency of interest, we can facilitate a metamaterial design such that this frequency becomes a natural frequency of the integrated system. Moreover, the vibration mode corresponding to this natural frequency can be customized and shaped to realize tailored/localized response distribution. This is fundamentally different from previous practices of utilizing geometry modification and/or feedback control to achieve mode tailoring. The metamaterial design is built upon the combinatorial effects of the bandgap feature and the effective resonant cavity feature, both attributed to the dynamic characteristics of the metamaterial beam. Analytical investigations based on unit-cell dynamics and modal analysis of the metamaterial beam are presented to reveal the underlying mechanism. Case illustrations are validated by finite element analyses. Owing to the online tunability of circuitry integrated, the proposed mode shaping technique can be online adjusted to fit specific requirements. The customized shaping of vibration modes by acoustic metamaterial synthesis has potential applications in vibration suppression, sensing enhancement and energy harvesting.

  4. A meta-analysis of surveys into vibration annoyance from railway

    NARCIS (Netherlands)

    Janssen, S.A.; Vos, H.; Koopman, A.

    2013-01-01

    The EU-project CargoVibes aims to describe the expected annoyance due to vibration among residents living near (freight) railway lines. Compared to the state of knowledge on the annoyance response to noise, relatively little is known about the relationship between vibration exposure and annoyance.

  5. Self-tuning MIMO disturbance feedforward control for active hard-mounted vibration isolators

    NARCIS (Netherlands)

    Beijen, M.A.; Heertjes, M.F.; Van Dijk, J.; Hakvoort, W. B.J.

    2018-01-01

    © 2017 Elsevier Ltd This paper proposes a multi-input multi-output (MIMO) disturbance feedforward controller to improve the rejection of floor vibrations in active vibration isolation systems for high-precision machinery. To minimize loss of performance due to model uncertainties, the feedforward

  6. Molecular vibrations the theory of infrared and Raman vibrational spectra

    CERN Document Server

    Wilson, E Bright; Cross, Paul C

    1980-01-01

    Pedagogical classic and essential reference focuses on mathematics of detailed vibrational analyses of polyatomic molecules, advancing from application of wave mechanics to potential functions and methods of solving secular determinant.

  7. Nuclear reactor scram suppression device

    International Nuclear Information System (INIS)

    Koshi, Hiroshi; Ozawa, Hisamitsu.

    1993-01-01

    The device of the present invention suppresses reactor scram due to increase of neutrons caused by pressure elevation in the reactor even when a portion of main steam pipes is closed by some or other causes such as closure of a main steam isolation valve in a BWR type power plant. That is, when a flow channel is closed, such as upon closure of a main steam isolation valve, a flow rate signal sent from each of main steam flow rate detection means is inputted to a selective circuit of a pressure control device, from which a normal value is obtained. A deviation value for each of the main steam flow rate values is determined from the value described above and a flow rate average value obtained in an averaging circuit. Abnormality in the main steam pipelines is judged if a level for each of the deviation values is greater than a predetermined value. Further, the insertion of selective control rods and trip and run back instructions for recycling pumps are controlled by output signals of the deviation value detection circuit, to decrease the reactor power and prevent elevation in the reactor. As a result, reactor scram due to increase of neutron fluxes is suppressed. (I.S.)

  8. Upper-limb tremor suppression with a 7DOF exoskeleton power-assist robot.

    Science.gov (United States)

    Kiguchi, Kazuo; Hayashi, Yoshiaki

    2013-01-01

    A tremor which is one of the involuntary motions is somewhat rhythmic motion that may occur in various body parts. Although there are several kinds of the tremor, an essential tremor is the most common tremor disorder of the arm. The essential tremor is a disorder of unknown cause, and it is common in the elderly. The essential tremor interferes with a patient's daily living activity, because it may occur during a voluntary motion. If a patient of an essential tremor uses an EMG-based controlled power-assist robot, the robot might misunderstand the user's motion intention because of the effect of the essential tremor. In that case, upper-limb power-assist robots must carry out tremor suppression as well as power-assist, since a person performs various precise tasks with certain tools by the upper-limb in daily living. Therefore, it is important to suppress the tremor at the hand and grasped tool. However, in the case of the tremor suppression control method which suppressed the vibrations of the hand and the tip of the tool, vibration of other part such as elbow might occur. In this paper, the tremor suppression control method for upper-limb power-assist robot is proposed. In the proposed method, the vibration of the elbow is suppressed in addition to the hand and the tip of the tool. The validity of the proposed method was verified by the experiments.

  9. Resonant vibration control of wind turbine blades

    DEFF Research Database (Denmark)

    Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker

    2010-01-01

    formulation accounts for arbitrary mass density distributions, general elastic crosssection properties and geometric stiffness effects due to internal stresses. A compact, linear formulation for aerodynamic forces with associated stiffness and damping terms is established and added to the structural model....... The efficiency of the resonant controller is demonstrated for a representative turbine blade exposed to turbulent wind loading. It is found that the present explicit tuning procedure yields close to optimal tuning, with very limited modal spill-over and effective reduction of the vibration amplitudes....

  10. Vibrational microspectroscopy analysis of human lenses

    Science.gov (United States)

    Paluszkiewicz, C.; Piergies, N.; Sozańska, A.; Chaniecki, P.; Rękas, M.; Miszczyk, J.; Gajda, M.; Kwiatek, W. M.

    2018-01-01

    In this study we present vibrational analysis of healthy (non-affected by cataract) and cataractous human lenses by means of Raman and FTIR spectroscopy methods. The performed analysis provides complex information about the secondary structure of the proteins and conformational changes of the amino acid residues due to the formation of opacification of human lens. Briefly, the changes in the conformation of the Tyr and Trp residues and the protein secondary structure between the healthy and cataractous samples, were recognized. Moreover, the observed spectral pattern suggests that the process of cataract development does not occur uniformly over the entire volume of the lens.

  11. Limerick Nuclear Generating Station vibration monitoring system

    International Nuclear Information System (INIS)

    Mikulski, R.

    1988-01-01

    Philadelphia Electric Company utilizes a vibration monitoring computer system at its Limerick Nuclear Generating Station to evaluate machine performance. Performance can be evaluated through instantaneous sampling, online static and transient data. The system functions as an alarm monitor, displaying timely alarm data to the control area. The passage of time since the system's inception has been a learning period. Evaluation through continuous use has led to many enhancements in alarm handling and in the acquisition and display of machine data. Due to the system's sophistication, a routine maintenance program is a necessity. This paper describes the system's diagnostic tools and current utilization. System development and maintenance techniques will also be discussed

  12. 49 CFR 178.819 - Vibration test.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration test. 178.819 Section 178.819... Testing of IBCs § 178.819 Vibration test. (a) General. The vibration test must be conducted for the... vibration test. (b) Test method. (1) A sample IBC, selected at random, must be filled and closed as for...

  13. Flexural vibrations of finite composite poroelastic cylinders

    Indian Academy of Sciences (India)

    If the wavelength is infinite, frequency equations are degenerated as product of two determinants pertaining to extensional vibrations and shear vibrations. In this case, it is seen that the nature of the surface does not have any influence over shear vibrations unlike in the case of extensional vibrations. For illustration purpose ...

  14. Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

    Directory of Open Access Journals (Sweden)

    Seung-Bok Choi

    2013-02-01

    Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

  15. MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations

    Directory of Open Access Journals (Sweden)

    Felix Weber

    2016-12-01

    Full Text Available This paper describes a semi-active vibration absorber (SVA concept based on a real-time controlled magnetorheological damper (MR-SVA for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD. Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.

  16. Vibration control of a cluster of buildings through the Vibrating Barrier

    Science.gov (United States)

    Tombari, A.; Garcia Espinosa, M.; Alexander, N. A.; Cacciola, P.

    2018-02-01

    A novel device, called Vibrating Barrier (ViBa), that aims to reduce the vibrations of adjacent structures subjected to ground motion waves has been recently proposed. The ViBa is a structure buried in the soil and detached from surrounding buildings that is able to absorb a significant portion of the dynamic energy arising from the ground motion. The working principle exploits the dynamic interaction among vibrating structures due to the propagation of waves through the soil, namely the structure-soil-structure interaction. In this paper the efficiency of the ViBa is investigated to control the vibrations of a cluster of buildings. To this aim, a discrete model of structures-site interaction involving multiple buildings and the ViBa is developed where the effects of the soil on the structures, i.e. the soil-structure interaction (SSI), the structure-soil-structure interaction (SSSI) as well as the ViBa-soil-structures interaction are taken into account by means of linear elastic springs. Closed-form solutions are derived to design the ViBa in the case of harmonic excitation from the analysis of the discrete model. Advanced finite element numerical simulations are performed in order to assess the efficiency of the ViBa for protecting more than a single building. Parametric studies are also conducted to identify beneficial/adverse effects in the use of the proposed vibration control strategy to protect cluster of buildings. Finally, experimental shake table tests are performed to a prototype of a cluster of two buildings protected by the ViBa device for validating the proposed numerical models.

  17. Primary pump vibration under accident conditions

    International Nuclear Information System (INIS)

    Guthrie, B.M.; Currie, T.C.

    1984-06-01

    This report presents the results of an international survey on the subject of vibration in nuclear primary coolant pumps due to two-phase flow, accident conditions. The literature search also revealed few Canadian references other than those of Ontario Hydro. Ontario Hydro's work has been extensive. Confidence in the mechanical integrity of the pumpsets is good, given the extent of the testing. However, conclusions with respect to piping integrity and thermal-hydraulic performance are difficult to determine due to the inexact geometry of the piping and the difficulties in estimating fluid conditions at the pump. The tests help to understand the phenomena and provide background information for analysis, but should be applied with caution to plant analyses. Much of the discussion in the report relates to pump head instability. This is perceived to be the most important flow regime causing vibration, as attested by the emphasis of the reviewed literature. A method for quantitative assessment of the forcing functions acting on the pump-piping system due to void generation and collapse is recommended. A relatively fundamental analytical approach is proposed, supplemented by reduced scale testing in the latter stages. 151 refs

  18. Thyroxin hormone suppression treatment

    International Nuclear Information System (INIS)

    Samuel, A.M.

    1999-01-01

    One of the important modalities of treatment of thyroid cancer (TC) after surgery is the administration of thyroxin as an adjuvant treatment. The analysis supports the theory that thyroid suppression plays an important role in patient management. 300 μg of thyroxin, as this is an adequate dose for suppression is given. Ideally the dose should be tailored by testing s-TSH levels. However, since a large number of the patients come from out station cities and villages this is impractical. We therefore depend on clinical criteria of hyperthyroid symptoms and adjust the dose. Very few patients need such adjustment

  19. Interocular suppression in children with deprivation amblyopia.

    Science.gov (United States)

    Hamm, Lisa; Chen, Zidong; Li, Jinrong; Black, Joanna; Dai, Shuan; Yuan, Junpeng; Yu, Minbin; Thompson, Benjamin

    2017-04-01

    In patients with anisometropic or strabismic amblyopia, interocular suppression can be minimized by presenting high contrast stimulus elements to the amblyopic eye and lower contrast elements to the fellow eye. This suggests a structurally intact binocular visual system that is functionally suppressed. We investigated whether suppression can also be overcome by contrast balancing in children with deprivation amblyopia due to childhood cataracts. To quantify interocular contrast balance, contrast interference thresholds were measured using an established dichoptic global motion technique for 21 children with deprivation amblyopia, 14 with anisometropic or mixed strabismic/anisometropic amblyopia and 10 visually normal children (mean age mean=9.9years, range 5-16years). We found that interocular suppression could be overcome by contrast balancing in most children with deprivation amblyopia, at least intermittently, and all children with anisometropic or mixed anisometropic/strabismic amblyopia. However, children with deprivation amblyopia due to early unilateral or bilateral cataracts could tolerate only very low contrast levels to the stronger eye indicating strong suppression. Our results suggest that treatment options reliant on contrast balanced dichoptic presentation could be attempted in a subset of children with deprivation amblyopia. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Vibration Theory, Vol. 1B

    DEFF Research Database (Denmark)

    Asmussen, J. C.; Nielsen, Søren R. K.

    The present collection of MATLAB exercises has been published as a supplement to the textbook, Svingningsteori, Bind 1 and the collection of exercises in Vibration theory, Vol. 1A, Solved Problems. Throughout the exercise references are made to these books. The purpose of the MATLAB exercises...... is to give a better understanding of the physical problems in linear vibration theory and to surpress the mathematical analysis used to solve the problems. For this purpose the MATLAB environment is excellent....

  1. Granular Media-Based Tunable Passive Vibration Suppressor

    Science.gov (United States)

    Dillon, Robert P.; Davis, Gregory L.; Shapiro, Andrew A.; Borgonia, John Paul C.; Kahn, Daniel L.; Boechler, Nicholas; Boechler,, Chiara

    2013-01-01

    and vibration suppression device is composed of statically compressed chains of spherical particles. The device superimposes a combination of dissipative damping and dispersive effects. The dissipative damping resulting from the elastic wave attenuation properties of the bulk material selected for the granular media is independent of particle geometry and periodicity, and can be accordingly designed based on the dissipative (or viscoelastic) properties of the material. For instance, a viscoelastic polymer might be selected where broadband damping is desired. In contrast, the dispersive effects result from the periodic arrangement and geometry of particles composing a linear granular chain. A uniform (monatomic) chain of statically compressed spherical particles will have a low-pass filter effect, with a cutoff frequency tunable as a function of particle mass, elastic modulus, Poisson fs ratio, radius, and static compression. Elastic waves with frequency content above this cutoff frequency will exhibit an exponential decay in amplitude as a function of propagation distance. System design targeting a specific application is conducted using a combination of theoretical, computational, and experimental techniques to appropriately select the particle radii, material (and thus elastic modulus and Poisson fs ratio), and static compression to satisfy estimated requirements derived for shock and/or vibration protection needs under particular operational conditions. The selection of a chain of polymer spheres with an elastic modulus .3 provided the appropriate dispersive filtering effect for that exercise; however, different operational scenarios may require the use of other polymers, metals, ceramics, or a combination thereof, configured as an array of spherical particles. The device is a linear array of spherical particles compressed in a container with a mechanism for attachment to the shock and/or vibration source, and a mechanism for attachment to the article requiring

  2. Added mass effect on flow-induced streamwise vibration of a circular cylinder in cross flow

    International Nuclear Information System (INIS)

    Nishihara, Takashi; Kaneko, Shigehiko; Watanabe, Tatsuo

    2004-01-01

    Nuclear power plants include a number of circular cylindrical structures subjected to flow, such as thermometer wells and nozzles. In order to retain their long-term integrity, it is essential to avoid or suppress vortex-induced vibrations. The added mass, one of the essential parameters when evaluating avoidance or suppression of vortex-induced vibrations, is usually considered as almost the same as the displaced fluid mass. However, recent studies have revealed that the added mass coefficient of a cylinder vibrating transversely in a cross flow largely varies and the variation in the added mass coefficient has significant effects on transverse vortex-induced vibrations under low mass-ratio conditions. As for streamwise vortex-induced vibrations, the added mass coefficient has not been determined, and its effects on the streamwise vibrations have been nuclear. In this study, the added mass coefficients of a circular cylinder oscillating in the streamwise direction were obtained by forced oscillation tests in a water tunnel. The results revealed the following properties of the added mass coefficient. The added mass coefficient for the streamwise vibrations varies greatly depending on the reduced velocity V r , and decreases as V r increases, declining to almost 0 at V r > 3.5 - 4.0. In contrast, the added mass coefficient depends less on cylinder amplitude, Reynolds number and the free-end effect of a cylinder. The added mass coefficients were also estimated based on the actual frequency in free-oscillation tests conducted by other researchers under low mass-ratio conditions. They agree well with those obtained by the forced oscillation tests. This result demonstrates that the gradual increase in the actual frequency in the free-oscillation tests can be reasonably explained by the properties of the added mass coefficient. Taking into account of the added mass effects, the validity of the stability criteria for avoiding streamwise vortex-induced vibrations in the

  3. Structural and acoustic response due to excitation from ship stern: overview and suggestions for future research

    Directory of Open Access Journals (Sweden)

    HUA Hongxing

    2017-08-01

    Full Text Available Several decades after the development of acoustic stealth technology for ships, there remains an urgent necessity to reduce low frequency structural and acoustic response due to excitation from the stern. This paper reviews research into the coupled vibration and acoustic problems of the sterns of vessels. Attention is especially paid to three key aspects: the characteristics of propeller forces, the vibration-acoustic signatures of coupled propeller-shaft-hull systems, and vibration/noise controls. Therefore, the mapping relationships of vibration noise from the stern excitation and propeller-shaft-hull system is obtained, and the control approaches for low frequency vibration noise is presented. Thereafter, several suggestions are made for further research work in the testing technology of the unsteady force of propellers, the structural vibration induced by the stern bearing friction and the vibration control of propeller-shaft systems in the future.

  4. Smooth adaptive sliding mode vibration control of a flexible parallel manipulator with multiple smart linkages in modal space

    Science.gov (United States)

    Zhang, Quan; Li, Chaodong; Zhang, Jiantao; Zhang, Jianhui

    2017-12-01

    This paper addresses the dynamic model and active vibration control of a rigid-flexible parallel manipulator with three smart links actuated by three linear ultrasonic motors. To suppress the vibration of three flexible intermediate links under high speed and acceleration, multiple Lead Zirconium Titanate (PZT) sensors and actuators are collocated mounted on each link, forming a smart structure which can achieve self-sensing and self-actuating. The dynamic characteristics and equations of the flexible link incorporated with the PZT sensors and actuator are analyzed and formulated. The smooth adaptive sliding mode based active vibration control is proposed to suppress the vibration of the smart links, and the first and second modes of the three links are targeted to be suppressed in modal space to avoid the spillover phenomenon. Simulations and experiments are implemented to validate the effectiveness of the smart structures and the proposed control laws. Experimental results show that the vibration of the first mode around 92 Hz and the second mode around 240 Hz of the three smart links are reduced respectively by 64.98%, 59.47%, 62.28%, and 45.80%, 36.79%, 33.33%, which further verify the multi-mode vibration control ability of the smooth adaptive sliding mode control law.

  5. Research into the problem of wheel tread spalling caused by wheelset longitudinal vibration

    Science.gov (United States)

    Liu, Wei; Ma, Weihua; Luo, Shihui; Zhu, Shengyang; Wei, Chongfeng

    2015-04-01

    This study mainly focuses on the mechanism of wheel tread spalling through wheelset longitudinal vibration that has been often neglected. Analysis of two actual cases of the wheel tread spalling problem leads to the conclusion that the wheel tread spalling is closely related to the wheelset longitudinal vibration in some locomotives, and many of these problems can be reasonably explained if the wheelset longitudinal vibration is considered. For better understanding of some abnormal wheel spalling problems, the formations of the wheelset longitudinal vibration and the wheel/rail contact parameters were analysed in the initial wheel tread spalling. With the preliminary analytical results, the wheelset longitudinal dynamic behaviour, the characteristics of wheel/rail contact and the mechanics in the condition of the wheelset longitudinal vibration were further studied quantitatively. The results showed that the wheelset longitudinal vibration changed not only the limit of these parameters and the position of principal stress, but also the direction of the principal stress on the surface of wheel/rail contact patch. It is likely that the significant stress changes provoke too much stress on the surface of wheel/rail contact patch, cause fatigue in wheel/rail contact patch and eventually lead to wheel tread spalling. The results of these studies suggest that the suppression of the wheelset longitudinal vibration extends wheel/rail life and the addition of a vertical damper with an ahead angle provides a possible solution to the wheel spalling problem.

  6. Simple Program to Investigate Hysteresis Damping Effect of Cross-Ties on Cables Vibration of Cable-Stayed Bridges

    Directory of Open Access Journals (Sweden)

    Panagis G. Papadopoulos

    2012-01-01

    Full Text Available A short computer program, fully documented, is presented, for the step-by-step dynamic analysis of isolated cables or couples of parallel cables of a cable-stayed bridge, connected to each other and possibly with the deck of the bridge, by very thin pretensioned wires (cross-ties and subjected to variation of their axial forces due to traffic or to successive pulses of a wind drag force. A simplified SDOF model, approximating the fundamental vibration mode, is adopted for every individual cable. The geometric nonlinearity of the cables is taken into account by their geometric stiffness, whereas the material nonlinearities of the cross-ties include compressive loosening, tensile yielding, and hysteresis stress-strain loops. Seven numerical experiments are performed. Based on them, it is observed that if two interconnected parallel cables have different dynamic characteristics, for example different lengths, thus different masses, weights, and geometric stiffnesses, too, or if one of them has a small additional mass, then a single pretensioned very thin wire, connecting them to each other and possibly with the deck of the bridge, proves effective in suppressing, by its hysteresis damping, the vibrations of the cables.

  7. Effect of Building Characteristics on Vibration-Induced Acceleration ...

    African Journals Online (AJOL)

    The effective accelerations for non-structural components located at different heights in a building are amplified due to the vibrations of the building and the components themselves. The amplifications along the height of buildings having different heights, structural systems and stiffness were studied. Four, eight and sixteen ...

  8. Structural, vibrational and bonding properties of hydro-nitrogen ...

    Indian Academy of Sciences (India)

    Hydro-nitrogen solids are potential high energy density materials (HEDMs) due to high mass ratio of nitrogen which find wide range of applications as propellants and explosives. In the present work, we report the structural and vibrational properties of Tetramethyl Ammonium Azide (TMAA) and HydroZonium Azide(HZA) ...

  9. Whole-body vibration exercise improves functional parameters in ...

    African Journals Online (AJOL)

    Background: Patients with osteogenesis imperfecta (OI) have abnormal bone modelling and resorption. The bone tissue adaptation and responsivity to dynamic and mechanical loading may be of therapeutic use under controlled circumstances. Improvements due to the wholebody vibration (WBV) exercises have been ...

  10. On the nature of highly vibrationally excited states of thiophosgene

    Indian Academy of Sciences (India)

    Abstract. In this work an analysis of the highly vibrationally excited states of thiophosgene (SCCl2) is made in order to gain insights into some of the experimental observations and spectral features. The states analysed here lie in a spectrally complex region where strong mode mixings are expected due to the overlap of ...

  11. The low frequency vibrations of hydrogen bonded adipic acid crystals

    Science.gov (United States)

    Yaremko, A. M.; Silvi, B.; Zelsmann, H. R.

    2000-03-01

    The low frequency vibrational spectrum of crystalline adipic acid has been investigated in the range 20-450 cm -1 at room and low temperatures. The experimental results are compared to ab initio results on a model asymmetric unit. It is shown that the doublet and quartet structures observed for several bands are due to Davydov splitting and Fermi resonance effects.

  12. Finite Element Modeling of Vibrations in Canvas Paintings

    NARCIS (Netherlands)

    Chiriboga Arroyo, P.G.

    2013-01-01

    Preventing vibration damage from occurring to valuable and sensitive canvas paintings is of main concern for museums and art conservation institutions. This concern has grown in recent years due to the increasing demand of paintings for exhibitions worldwide and the concomitant need for their

  13. Plasma suppression of beamstrahlung

    International Nuclear Information System (INIS)

    Whittum, D.H.; Sessler, A.M.; Stewart, J.J.; Yu, S.S.

    1988-06-01

    We investigate the use of a plasma at the interaction point of two colliding beams to suppress beamsstrahlung and related phenomena. We derive conditions for good current cancellation via plasma return currents and report on numerical simulations conducted to confirm our analytic results. 10 refs., 5 figs., 4 tabs

  14. Sub-nano tesla magnetic imaging based on room-temperature magnetic flux sensors with vibrating sample magnetometry

    Directory of Open Access Journals (Sweden)

    Yoshiaki Adachi

    2017-05-01

    Full Text Available We developed a two-dimensional imaging method for weak magnetic charge distribution using a commercially available magnetic impedance sensor whose magnetic field resolution is 10 pT/Hz1/2 at 10 Hz. When we applied the vibrating sample magnetometry, giving a minute mechanical vibration to the sample and detecting magnetic signals modulated by the vibration frequency, the effects of 1/f noise and the environmental low-frequency band noise were suppressed, and a weak magnetic charge distribution was obtained without magnetic shielding. Furthermore, improvement in the spatial resolution was also expected when the signals were demodulated at the second harmonic frequency of the vibration. In this paper, a preliminary magnetic charge imaging using the vibrating sample magnetometry and its results are demonstrated.

  15. 30 CFR 75.1107-6 - Capacity of fire suppression devices; location and direction of nozzles.

    Science.gov (United States)

    2010-07-01

    ... ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Fire Protection Fire Suppression Devices and Fire-Resistant Hydraulic Fluids on Underground Equipment... withstand rough usage and vibration when installed on mining equipment. (b) The extinguishant-discharge...

  16. Vibration and acoustic response of a composite plate with inherent material damping in a thermal environment

    Science.gov (United States)

    Jeyaraj, P.; Ganesan, N.; Padmanabhan, Chandramouli

    2009-02-01

    This paper presents numerical studies on the vibration and acoustic response characteristics of a fiber-reinforced composite plate in a thermal environment by considering the inherent material damping property of the composite material. Initially the critical buckling temperature is obtained, followed by free and forced vibration analyses considering the pre-stress due to the imposed thermal environment. The vibration response predicted is then used to compute the sound radiation. The critical buckling temperature and vibration response are obtained using the finite element method based on the Classical Laminate Plate Theory (CLPT) while sound radiation characteristics are obtained using a coupled FEM/BEM technique. It is found that the vibration response of the structure reduces with an increase in uniform temperature rise for both Glass Epoxy and PEEK/IM7 materials, but the overall sound radiation of the plate reduces only marginally due to interaction between reduced stiffness and enhanced damping.

  17. Knots and Random Walks in Vibrated Granular Chains

    International Nuclear Information System (INIS)

    Ben-Naim, E.; Daya, Z. A.; Vorobieff, P.; Ecke, R. E.

    2001-01-01

    We study experimentally statistical properties of the opening times of knots in vertically vibrated granular chains. Our measurements are in good qualitative and quantitative agreement with a theoretical model involving three random walks interacting via hard-core exclusion in one spatial dimension. In particular, the knot survival probability follows a universal scaling function which is independent of the chain length, with a corresponding diffusive characteristic time scale. Both the large-exit-time and the small-exit-time tails of the distribution are suppressed exponentially, and the corresponding decay coefficients are in excellent agreement with theoretical values

  18. Broadband noise and vibration reduction for lightweight chassis design using smart structure technologies

    Science.gov (United States)

    Messner, L.; Gusenbauer, M.; Rittenschober, T.

    2007-04-01

    Lightweight design is gaining more and more importance in the automotive industry. Engineers are trying hard to reduce the increased weight of chassis due to safety and comfort issues. This paper presents new achievements in the field of control design for smart structures, targeting at innovative lightweight, high-performance and low-noise engineering constructions with integrated embedded systems technology: The first part of the paper focuses on new developments in the field of low-cost, highly efficient smart structure power electronics for piezoelectric elements. These elements will be integrated into automotive chassis, which are able to measure any structure-borne disturbance such as vibrations. The second part of the paper presents frontier research in the design of a high-performance control concept for smart structure applications. This innovative control concept based on a nonlinear state observer design, targets at highly robust and broadband suppression of structure-borne noise in terms of fast changing frequencies. The controller performance is not only assessed with respect to stability and disturbance rejection but also with respect to technical feasibility and implementation issues (required sample rate, rounding errors due to inappropriate data formats, latency, etc.).

  19. Vibrational spectroscopy of proteins

    International Nuclear Information System (INIS)

    Schwaighofer, A.

    2013-01-01

    Two important steps for the development of a biosensor are the immobilization of the biological component (e.g. protein) on a surface and the enhancement of the signal to improve the sensitivity of detection. To address these subjects, the present work describes Fourier transform infrared (FTIR) investigations of several proteins bound to the surface of an attenuated total reflection (ATR) crystal. Furthermore, new nanostructured surfaces for signal enhancement were developed for use in FTIR microscopy. The mitochondrial redox-protein cytochrome c oxidase (CcO) was incorporated into a protein-tethered bilayer lipid membrane (ptBLM) on an ATR crystal featuring a roughened two-layer gold surface for signal enhancement. Electrochemical excitation by periodic potential pulses at different modulation frequencies was followed by time-resolved FTIR spectroscopy. Phase sensitive detection was used for deconvolution of the IR spectra into vibrational components. A model based on protonation-dependent chemical reaction kinetics could be fitted to the time evolution of IR bands attributed to several different redox centers of the CcO. Further investigations involved the odorant binding protein 14 (OBP14) of the honey bee (Apis mellifera), which was studied using ATR-FTIR spectroscopy and circular dichroism. OBP14 was found to be thermally stable up to 45 °C, thus permitting the potential application of this protein for the fabrication of biosensors. Thermal denaturation measurements showed that odorant binding increases the thermal stability of the OBP-odorant complex. In another project, plasmonic nanostructures were fabricated that enhance the absorbance in FTIR microscopy measurements. The nanostructures are composed of an array of round-shaped insulator and gold discs on top of a continuous gold layer. Enhancement factors of up to ⁓125 could be observed with self-assembled monolayers of dodecanethiol molecules immobilized on the gold surface (author) [de

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

    Directory of Open Access Journals (Sweden)

    Chia-Hung Wu

    2012-10-01

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

  1. Scaling Techniques for Combustion Device Random Vibration Predictions

    Science.gov (United States)

    Kenny, R. J.; Ferebee, R. C.; Duvall, L. D.

    2016-01-01

    This work presents compares scaling techniques that can be used for prediction of combustion device component random vibration levels with excitation due to the internal combustion dynamics. Acceleration and unsteady dynamic pressure data from multiple component test programs are compared and normalized per the two scaling approaches reviewed. Two scaling technique are reviewed and compared against the collected component test data. The first technique is an existing approach developed by Barrett, and the second technique is an updated approach new to this work. Results from utilizing both techniques are presented and recommendations about future component random vibration prediction approaches are given.

  2. Nonlinear vibration of an axially loaded beam carrying rigid bodies

    Directory of Open Access Journals (Sweden)

    O. Barry

    2016-12-01

    Full Text Available This paper investigates the nonlinear vibration due to mid-plane stretching of an axially loaded simply supported beam carrying multiple rigid masses. Explicit expressions and closed form solutions of both linear and nonlinear analysis of the present vibration problem are presented for the first time. The validity of the analytical model is demonstrated using finite element analysis and via comparison with the result in the literature. Parametric studies are conducted to examine how the nonlinear frequency and frequency response curve are affected by tension, rotational inertia, and number of intermediate rigid bodies.

  3. Evaluation of hand-arm vibration reducing effect of anti-vibration glove

    OpenAIRE

    樹野, 淳也; 前田, 節雄; 横田, 和樹; 平, 雄一郎

    2015-01-01

    Many kinds of the anti-vibration glove have been developed for reducing hand-arm vibration during the operation with vibration tools. International standard ISO 10819 evaluates the physical effect of gloves' vibration transmissibility but not evaluates the physiological effect of human hands. Thus, in this paper, we proposed the evaluation using the temporary threshold shift of vibrotactile perception threshold to evaluate the hand-arm vibration reducing effect of anti-vibration glove. We per...

  4. Unusual motions of a vibrating string

    Science.gov (United States)

    Hanson, Roger J.

    2003-10-01

    The actual motions of a sinusoidally driven vibrating string can be very complex due to nonlinear effects resulting from varying tension and longitudinal motion not included in simple linear theory. Commonly observed effects are: generation of motion perpendicular to the driving force, sudden jumps in amplitude, hysteresis, and generation of higher harmonics. In addition, these effects are profoundly influenced by wire asymmetries which in a brass harpsichord wire can cause a small splitting of each natural frequency of free vibration into two closely spaced frequencies (relative separation ~0.2% to 2%), each associated with transverse motion along two orthogonal characteristic wire axes. Some unusual resulting patterns of complex motions of a point on the wire are exhibited on videotape. Examples include: sudden changes of harmonic content, generation of subharmonics, and motion which appears nearly chaotic but which has a pattern period of over 10 s. Another unusual phenomenon due to entirely different causes can occur when a violin string is bowed with a higher than normal force resulting in sounds ranging from about a musical third to a twelfth lower than the sound produced when the string is plucked.

  5. Design guidelines for passive instability suppression - Task-11 report[Wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, M.H.; Buhl, T.

    2006-12-15

    In these guidelines for passive instability suppression, eight relevant topics within aeroelastic stability of turbines are considered for the parameter variations: 1. Effect of airfoil aerodynamics: The airfoil aerodynamics given by the profile coefficients for aerodynamic lift, drag, and moment are shown to have a direct effect on aerodynamic damping of blade vibrations. A redesign of the airfoils can improve the power performance of the rotor without loss of aerodynamic damping. 2. Effect of flap/edgewise frequency coincidence: The natural frequencies of the first flapwise and first edgewise blade bending modes become closer as the blades become more slender. This 1-1 resonance may lead to a coupling flap- and edgewise blade vibrations which increases the edgewise blade mode damping. 3. Effect of flap/edgewise whirling coupling: The aerodynamic damping of blade vibrations close to the rotor plane are generally lower than the aerodynamic damping of vibrations out of the rotor plane. A structural coupling between the flapwise and edgewise whirling modes can increase the overall aerodynamic damping by adding more out of plane blade motion to the edgewise whirling modes. 4. Effect of torsional blade stiffness: A low torsional blade stiffness may lead to flutter where the first torsional blade mode couples to a flapwise bending mode in a flutter instability through the aerodynamic forces. 5. Can whirl flutter happen on a wind turbine? Whirl flutter is an aeroelastic instability similar to blade flutter. Whirl flutter can occur on turbines with very low natural frequencies of the tilt and yaw modes (about 5 % of their original values). 6. Edgewise/torsion coupling for large flapwise deflections: The large flapwise deflection of modern slender blades lead to a geometric coupling of edgewise bending and torsion. The aeroelastic damping of the blade modes are affected by a flapwise prebend of the blade. 7. Effect of yaw error on damping from wake: The wake behind the

  6. Active Blade Vibration Control Being Developed and Tested

    Science.gov (United States)

    Johnson, Dexter

    2003-01-01

    Gas turbine engines are currently being designed to have increased performance, lower weight and manufacturing costs, and higher reliability. Consequently, turbomachinery components, such as turbine and compressor blades, have designs that are susceptible to new vibration problems and eventual in-service failure due to high-cycle fatigue. To address this problem, researchers at the NASA Glenn Research Center are developing and testing innovative active blade vibration control concepts. Preliminary results of using an active blade vibration control system, involving a rotor supported by an active magnetic bearing in Glenn's Dynamic Spin Rig, indicate promising results (see the photograph). Active blade vibration control was achieved using feedback of blade strain gauge signals within the magnetic bearing control loop. The vibration amplitude was reduced substantially (see the graphs). Also, vibration amplitude amplification was demonstrated; this could be used to enhance structural mode identification, if desired. These results were for a nonrotating two-bladed disk. Tests for rotating blades are planned. Current and future active blade vibration control research is planned to use a fully magnetically suspended rotor and smart materials. For the fully magnetically suspended rotor work, three magnetic bearings (two radial and one axial) will be used as actuators instead of one magnetic bearing. This will allow additional degrees of freedom to be used for control. For the smart materials work, control effectors located on and off the blade will be considered. Piezoelectric materials will be considered for on-the-blade actuation, and actuator placement on a stator vane, or other nearby structure, will be investigated for off-the-blade actuation. Initial work will focus on determining the feasibility of these methods by performing basic analysis and simple experiments involving feedback control.

  7. Vibration analysis of the synchronous motor of a propane compressor

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, D.; Rangel Junior, J. de S. [Petroleo Brasileiro S.A. - PETROBRAS, Rio de Janeiro, RJ (Brazil)], Emails: diananogueira@petrobras.com.br, joilson_jr@petrobras.com.br; Moreira, R.G. [Petroleo Brasileiro S.A. - PETROBRAS, Cabiunas, RJ (Brazil)], E-mail: ricgmoreira@petrobras.com.br

    2010-07-01

    This paper aims at describing the Analysis of a synchronous electric motor which presented high vibration levels (shaft displacement and bearing housing vibration) during the commissioning process, as well as propose the best practices for the solution of vibration problems in similar situations. This motor belongs to the propane centrifugal compressor installed at a Gas Compression Station. The methodology used in this study conducted an investigation of the problems presented in the motor through the execution of many types of tests and the analysis of the results. The main evaluations were performed, such as the vibration analysis and the rotor dynamic analysis. The electric motor was shipped back to the manufacturer's shop, where the manufacturer made certain modifications to the motor structure so as to improve the structure stiffness, such as the improvement of the support and the increase of the thickness of the structural plates. In addition to that, the dynamic balancing of the rotating set was checked. Finally, the excitation at a critical speed close to the rated speed was found after Rotor Dynamics Analysis was performed again, because of the increase in bearing clearances. The bearing shells were replaced so as to increase the separation margin between these frequencies. In order to verify the final condition of the motor, the manufacturer repeated the standard tests - FAT (Factory Acceptance Tests) - according to internal procedure and international standards. As a result of this work, it was possible to conclude that there was a significant increase in the vibration levels due to unbalance conditions. It was also possible to conclude that there are close relationships between high vibration levels and unbalance conditions, as well as between high vibration levels and the stiffness of the system and its support. Certain points of attention related to the manufacturing process of the motor compressor are described at the end of this paper, based

  8. Vibration Therapy in Management of Delayed Onset Muscle Soreness (DOMS).

    Science.gov (United States)

    Veqar, Zubia; Imtiyaz, Shagufta

    2014-06-01

    Both athletic and nonathletic population when subjected to any unaccustomed or unfamiliar exercise will experience pain 24-72 hours postexercise. This exercise especially eccentric in nature caused primarily by muscle damage is known as delayed-onset muscle soreness (DOMS). This damage is characterized by muscular pain, decreased muscle force production, reduce range of motion and discomfort experienced. DOMS is due to microscopic muscle fiber tears. The presence of DOMS increases risk of injury. A reduced range of motion may lead to the incapability to efficiently absorb the shock that affect physical activity. Alterations to mechanical motion may increase strain placed on soft tissue structures. Reduced force output may signal compensatory recruitment of muscles, thus leading to unaccustomed stress on musculature. Differences in strength ratios may also cause excessive strain on unaccustomed musculature. A range of interventions aimed at decreasing symptoms of DOMS have been proposed. Although voluminous research has been done in this regard, there is little consensus among the practitioners regarding the most effective way of treating DOMS. Mechanical oscillatory motion provided by vibration therapy. Vibration could represent an effective exercise intervention for enhancing neuromuscular performance in athletes. Vibration has shown effectiveness in flexibility and explosive power. Vibration can apply either local area or whole body vibration. Vibration therapy improves muscular strength, power development, kinesthetic awareness, decreased muscle sore, increased range of motion, and increased blood flow under the skin. VT was effective for reduction of DOMS and regaining full ROM. Application of whole body vibration therapy in postexercise demonstrates less pressure pain threshold, muscle soreness along with less reduction maximal isometric and isokinetic voluntary strength and lower creatine kinase levels in the blood.

  9. Nodeless vibrational amplitudes and quantum nonadiabatic dynamics in the nested funnel for a pseudo Jahn-Teller molecule or homodimer

    Science.gov (United States)

    Peters, William K.; Tiwari, Vivek; Jonas, David M.

    2017-11-01

    The nonadiabatic states and dynamics are investigated for a linear vibronic coupling Hamiltonian with a static electronic splitting and weak off-diagonal Jahn-Teller coupling through a single vibration with a vibrational-electronic resonance. With a transformation of the electronic basis, this Hamiltonian is also applicable to the anti-correlated vibration in a symmetric homodimer with marginally strong constant off-diagonal coupling, where the non-adiabatic states and dynamics model electronic excitation energy transfer or self-exchange electron transfer. For parameters modeling a free-base naphthalocyanine, the nonadiabatic couplings are deeply quantum mechanical and depend on wavepacket width; scalar couplings are as important as the derivative couplings that are usually interpreted to depend on vibrational velocity in semiclassical curve crossing or surface hopping theories. A colored visualization scheme that fully characterizes the non-adiabatic states using the exact factorization is developed. The nonadiabatic states in this nested funnel have nodeless vibrational factors with strongly avoided zeroes in their vibrational probability densities. Vibronic dynamics are visualized through the vibrational coordinate dependent density of the time-dependent dipole moment in free induction decay. Vibrational motion is amplified by the nonadiabatic couplings, with asymmetric and anisotropic motions that depend upon the excitation polarization in the molecular frame and can be reversed by a change in polarization. This generates a vibrational quantum beat anisotropy in excess of 2/5. The amplitude of vibrational motion can be larger than that on the uncoupled potentials, and the electronic population transfer is maximized within one vibrational period. Most of these dynamics are missed by the adiabatic approximation, and some electronic and vibrational motions are completely suppressed by the Condon approximation of a coordinate-independent transition dipole between

  10. Construction vibration attenuation with distance and its effect on the quality of early-age concrete.

    Science.gov (United States)

    2011-06-01

    Damage to structures due to vibrations from pile driving operations is of great concern to engineers. This : research has stemmed from the need to address potential damage to concrete-filled pipe piles and recently : placed concrete structures that c...

  11. Development and evaluation of vibrating Kelly Ball Test (VKelly test) for the workability of concrete.

    Science.gov (United States)

    2015-03-01

    Due to the low workability of slipform concrete mixtures, the science of rheology is not strictly applicable for such concrete. However, : the concept of rheological behavior may still be considered useful. A novel workability test method (Vibrating ...

  12. Modeling and Mechanism of Rain-Wind Induced Vibration of Bundled Conductors

    Directory of Open Access Journals (Sweden)

    Chao Zhou

    2016-01-01

    Full Text Available Under the certain rain-wind conditions, bundled conductors exhibit a rain-wind induced large-amplitude vibration. This type of vibration can cause the fatigue fractures of conductors and fatigue failures of spacers, which threaten the safety operation and serviceability of high-voltage transmission line. To reveal the mechanism of rain-wind induced vibration of bundled conductors, a series of 2-dimensional CFD models about the twin bundled conductors with rivulets are developed to obtain the curves of aerodynamic coefficients with the upper rivulet angle. The influences of the forward conductor’s aerodynamic shielding and the upper rivulet’s aerodynamic characteristics on the leeward conductor are discussed. Furthermore, a 2-dimensional 3DOF model for the rain-wind induced vibration of the leeward conductor is established. The model is solved by finite element method and Newmark method, and the effects of the wind velocity and the upper rivulet’s motion on vibration amplitude of the leeward conductor are analyzed. By contrast with the wake-induced vibration, it can easily find that the characteristics of rain-wind vibration are obviously different from those of the wake-induced vibration, and the main reason of the rain-induced vibration may be due to the upper rivulet’s motion.

  13. A zero phase adaptive fuzzy Kalman filter for physiological tremor suppression in robotically assisted minimally invasive surgery.

    Science.gov (United States)

    Sang, Hongqiang; Yang, Chenghao; Liu, Fen; Yun, Jintian; Jin, Guoguang; Chen, Fa

    2016-12-01

    Hand physiological tremor of surgeons can cause vibration at the surgical instrument tip, which may make it difficult for the surgeon to perform fine manipulations of tissue, needles, and sutures. A zero phase adaptive fuzzy Kalman filter (ZPAFKF) is proposed to suppress hand tremor and vibration of a robotic surgical system. The involuntary motion can be reduced by adding a compensating signal that has the same magnitude and frequency but opposite phase with the tremor signal. Simulations and experiments using different filters were performed. Results show that the proposed filter can avoid the loss of useful motion information and time delay, and better suppress minor and varying tremor. The ZPAFKF can provide less error, preferred accuracy, better tremor estimation, and more desirable compensation performance, to suppress hand tremor and decrease vibration at the surgical instrument tip. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  14. Optimal placement and decentralized robust vibration control for spacecraft smart solar panel structures

    International Nuclear Information System (INIS)

    Jiang, Jian-ping; Li, Dong-xu

    2010-01-01

    The decentralized robust vibration control with collocated piezoelectric actuator and strain sensor pairs is considered in this paper for spacecraft solar panel structures. Each actuator is driven individually by the output of the corresponding sensor so that only local feedback control is implemented, with each actuator, sensor and controller operating independently. Firstly, an optimal placement method for the location of the collocated piezoelectric actuator and strain gauge sensor pairs is developed based on the degree of observability and controllability indices for solar panel structures. Secondly, a decentralized robust H ∞ controller is designed to suppress the vibration induced by external disturbance. Finally, a numerical comparison between centralized and decentralized control systems is performed in order to investigate their effectiveness to suppress vibration of the smart solar panel. The simulation results show that the vibration can be significantly suppressed with permitted actuator voltages by the controllers. The decentralized control system almost has the same disturbance attenuation level as the centralized control system with a bit higher control voltages. More importantly, the decentralized controller composed of four three-order systems is a better practical implementation than a high-order centralized controller is

  15. Suppression of Nonlinear Interactions in Resonant Macroscopic Quantum Devices : the Example of the Solid-State Ring Laser Gyroscope

    OpenAIRE

    Schwartz, Sylvain; Gutty, François; Feugnet, Gilles; Bouyer, Philippe; Pocholle, Jean-Paul

    2008-01-01

    International audience; We study the suppression of nonlinear interactions in resonant macroscopic quantum devices in the case of the solid-state ring laser gyroscope. These nonlinear interactions are tuned by vibrating the gain medium along the cavity axis. Beat note occurrence under rotation provides a precise measurement of the strength of nonlinear interactions, which turn out to vanish for some discrete values of the amplitude of vibration. Our theoretical description, in very good agree...

  16. Investigation on active vibration isolation of a Stewart platform with piezoelectric actuators

    Science.gov (United States)

    Wang, Chaoxin; Xie, Xiling; Chen, Yanhao; Zhang, Zhiyi

    2016-11-01

    A Stewart platform with piezoelectric actuators is presented for micro-vibration isolation. The Jacobi matrix of the Stewart platform, which reveals the relationship between the position/pointing of the payload and the extensions of the six struts, is derived by kinematic analysis. The dynamic model of the Stewart platform is established by the FRF (frequency response function) synthesis method. In the active control loop, the direct feedback of integrated forces is combined with the FxLMS based adaptive feedback to dampen vibration of inherent modes and suppress transmission of periodic vibrations. Numerical simulations were conducted to prove vibration isolation performance of the Stewart platform under random and periodical disturbances, respectively. In the experiment, the output consistencies of the six piezoelectric actuators were measured at first and the theoretical Jacobi matrix as well as the feedback gain of each piezoelectric actuator was subsequently modified according to the measured consistencies. The direct feedback loop was adjusted to achieve sufficient active damping and the FxLMS based adaptive feedback control was adopted to suppress vibration transmission in the six struts. Experimental results have demonstrated that the Stewart platform can achieve 30 dB attenuation of periodical disturbances and 10-20 dB attenuation of random disturbances in the frequency range of 5-200 Hz.

  17. The effects of an inserted linear carbon chain on the vibration of a carbon nanotube

    International Nuclear Information System (INIS)

    Hu, Z L; Guo, X M; Ru, C Q

    2007-01-01

    An elastic string-elastic shell model is developed to study the coupled vibration of a carbon nanowire made of a linear carbon chain (C-chain) inserted inside a carbon nanotube (CNT). It is shown that the vibration of the inserted C-chain is coupled with vibration of the CNT only for vibration modes with circumferential wavenumber n = 1. In other cases, such as axisymmetric modes (n = 0) or higher-order vibration modes with n≥2, total resultant van der Waals (vdW) force acting on the C-chain due to the innermost tube always vanishes, and therefore vibration of the CNT does not cause vibration of the inserted C-chain, although the existence of the C-chain does have an effect on the vibration of the CNT through the chain-CNT vdW forces acting on the innermost tube. The present model predicts that non-coaxial vibration between the C-chain and the innermost tube does not occur due to negligible bending rigidity of the C-chain. In addition, it is found that the C-chain has most significant effect on the lowest frequency associated with the radial vibration mode for circumferential wavenumber 2 (n = 2). In particular, the effect of the C-chain on the axisymmetric radial breathing frequencies (n = 0) predicted by the present model is found to be in reasonable agreement with known experimental and modeling results available in the literature. The present work offers systematic modeling results on the effects of an inserted C-chain on the vibration of CNTs

  18. Special considerations for vibration analysis on longwall equipment

    Energy Technology Data Exchange (ETDEWEB)

    Towles, B.

    1996-12-31

    West Elk Mine has included vibration analysis as a part of the longwall maintenance program since 1993. Longwall equipment presents several special problems which are not common to most vibration analysis applications: (1) Heavy construction of equipment damps some signals making machine condition determinations difficult, and (2) Complexity of longwall equipment; (3) Difficulty in isolating spectrum frequencies to individual machinery components; (4) Flexing of equipment frames and housings due to longwall face advance affects vibration spectrums; (5) Difficulty of obtaining necessary information on internal machinery components from longwall equipment suppliers; (6) Permissibility of data collection instruments. In spite of these difficulties, West Elk has had positive results in preventing catastrophic failures, predicting life expectancy of failing components, making general machinery improvements in cooperation with manufacturers and determining rebuild quality.

  19. Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

    Science.gov (United States)

    Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

    2016-01-01

    Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

  20. PC based vibration monitoring system

    International Nuclear Information System (INIS)

    Jain, Sanjay K.; Roy, D.A.; Pithawa, C.K.; Patil, R.K.

    2004-01-01

    Health of large rotating machinery gets reflected in the vibration signature of the rotor and supporting structures and proper recording of these signals and their analysis can give a clear picture of the health of the machine. Using these data and their trending, it is possible to predict an impending trouble in the machine so that preventive action can be taken in time and catastrophic failure can be avoided. Continuous monitoring and analysis can give quick warning and enable operator to take preventive measures. Reactor Control Division, BARC is developing a PC based Vibration monitoring system for turbo generator machinery. The System can acquire 20 vibration signals at a rate of 5000 samples per second and also 15 process signals at a rate of 100 samples/ sec. The software for vibration monitoring system includes acquisition modules, analysis modules and Graphical User Interface module. The acquisition module involves initialization, setting of required parameters and acquiring the data from PC-based data acquisition cards. The acquired raw vibration data is then stored for analysis using various software packages. The display and analysis of acquired data is done in LabVIEW 7.0 where the data is displayed in time as well as frequency domain along with the RMS value of the signal. (author)

  1. Hand-arm vibration syndrome

    Science.gov (United States)

    Shen, Shixin (Cindy); House, Ronald A.

    2017-01-01

    Abstract Objective To provide family physicians with an understanding of the epidemiology, pathogenesis, symptoms, diagnosis, and management of hand-arm vibration syndrome (HAVS), an important and common occupational disease in Canada. Sources of information A MEDLINE search was conducted for research and review articles on HAVS. A Google search was conducted to obtain gray literature relevant to the Canadian context. Additional references were obtained from the articles identified. Main message Hand-arm vibration syndrome is a prevalent occupational disease affecting workers in multiple industries in which vibrating tools are used. However, it is underdiagnosed in Canada. It has 3 components—vascular, in the form of secondary Raynaud phenomenon; sensorineural; and musculoskeletal. Hand-arm vibration syndrome in its more advanced stages contributes to substantial disability and poor quality of life. Its diagnosis requires careful history taking, in particular occupational history, physical examination, laboratory tests to rule out alternative diagnoses, and referral to an occupational medicine specialist for additional investigations. Management involves reduction of vibration exposure, avoidance of cold conditions, smoking cessation, and medication. Conclusion To ensure timely diagnosis of HAVS and improve prognosis and quality of life, family physicians should be aware of this common occupational disease and be able to elicit the relevant occupational history, refer patients to occupational medicine clinics, and appropriately initiate compensation claims. PMID:28292796

  2. J/Ψ suppression

    International Nuclear Information System (INIS)

    Giubellino, P.; Abreu, M.C.; Alessandro, B.; Alexa, C.; Arnaldi, R.; Astruc, J.; Atayan, M.; Baglin, C.; Baldit, A.; Bedjidian, M.; Bellaiche, F.; Beole, S.; Boldea, V.; Bordalo, P.; Bussiere, A.; Capony, V.; Casagrande, L.; Castor, J.; Chambon, T.; Chaurand, B.; Chevrot, I.; Cheynis, B.; Chiavassa, E.; Cicalo, C.; Comets, M.P.; Constantinescu, S.; Cruz, J.; De Falco, A.; De Marco, N.; Dellacasa, G.; Devaux, A.; Dita, S.; Drapier, O.; Espagnon, B.; Fargeix, J.; Filippov, S.N.; Fleuret, F.; Force, P.; Gallio, M.; Gavrilov, Y.K.; Gerschel, C.; Giubellino, P.; Golubeva, M.B.; Gonin, M.; Grigorian, A.A.; Grossiord, J.Y.; Guber, F.F.; Guichard, A.; Gulkaninan, H.; Hakobyan, R.; Haroutunian, R.; Idzik, M.; Jouan, D.; Karavitcheva, T.L.; Kluberg, L.; Kurepin, A.B.; Le Bornec, Y.; Lourenco, C.; Mac Cormick, M.; Macciotta, P.; Marzari-Chiesa, A.; Masera, M.; Masoni, A.; Mehrabyan, S.; Mourgues, S.; Musso, A.; Ohlsson-Malek, F.; Petiau, P.; Piccotti, A.; Pizzi, J.R.; Prado da Silva, W.L.; Puddu, G.; Quintans, C.; Racca, C.; Ramello, L.; Ramos, S.; Rato-Mendes, P.; Riccati, L.; Romana, A.; Sartori, S.; Saturnini, P.; Scomparin, E.; Serci, S.; Shahoyan, R.; Silva, S.; Soave, C.; Sonderegger, P.; Tarrago, X.; Temnikov, P.; Topilskaya, N.S.; Usai, G.; Vale, C.; Vercellin, E.; Willis, N.

    1999-01-01

    The cross section for J/Ψ production in Pb-Pb interactions at 158 GeV per nucleon is measured at the CERN SPS by the NA50 experiment. The final results from the 1995 run are presented here together with preliminary ones from the high-statistics 1996 run. An anomalous J/Ψ suppression is observed in Pb-Pb collisions as compared to extrapolations of the previous results obtained by the NA38 experiment with proton and lighter ion beams. The results of the two runs are in good agreement. The results from the 1996 run allow the study of the onset of the anomalous suppression within the same set of data, showing evidence of a sharp change of behaviour around a value of neutral transverse energy, as measured by our electromagnetic calorimeter, of about 50 GeV

  3. [Neurological signs due to isolated vitamin B12 deficiency].

    Science.gov (United States)

    Martinez Estrada, K M; Cadabal Rodriguez, T; Miguens Blanco, I; García Méndez, L

    2013-01-01

    Isolated vitamin B12 deficiency is a common condition in elderly patients but uncommon in patients younger than 30 years, with an average age of onset between 60 and 70 years. This is because the dietary cobalamin, which is normally split by enzymes in meat in the presence of hydrochloric acid and pepsin in the stomach, is not released in the stomachs of elderly patients, usually due to achlorhydria. Although the body may be unable to release cobalamin it does retain the ability to absorb vitamin B12 in its crystalline form, which is present in multivitamin preparations. Other causes are due to drugs that suppress gastric acid production. Neurological signs of vitamin B12 deficiency can occur in patients with a normal haematocrit and red cell indices. They include paresthesia, loss of sensation and strength in the limbs, and ataxia. Reflexes may be slowed down or increased. Romberg and Babinsky signs may be positive, and vibration and position sensitivity often decreases. Behavoural disorders range from irritability and memory loss to severe dementia. The symptoms often do not fully respond to treatment. A case is presented of an isolated vitamin B12 deficiency in 27 year-old female patient who was seen in primary health care. During anamnesis she mentioned low back pain, to which she attributed the loss of strength and tenderness in the right side of the body, as well as the slow and progressive onset of accompanied headache for the previous 4 days. Copyright © 2012 Sociedad Española de Médicos de Atención Primaria (SEMERGEN). Publicado por Elsevier España. All rights reserved.

  4. Ultrasonic metal welding with a vibration source using longitudinal and torsional vibration transducers

    Science.gov (United States)

    Asami, Takuya; Tamada, Yosuke; Higuchi, Yusuke; Miura, Hikaru

    2017-07-01

    Conventional ultrasonic metal welding for joining dissimilar metals uses a linear vibration locus, although this method suffers from problems such as low overall weld strength. Our previous studies have shown that ultrasonic welding with a planar vibration locus improves the weld strength. However, the vibration source in our previous studies had problems in longitudinal-torsional vibration controllability and small welding tip. Therefore, the study of the optimal shape of the vibration locus was difficult. Furthermore, improvement of weld strength cannot be expected. We have developed a new ultrasonic vibration source that can control the longitudinal-torsional vibration and can connect to a large welding tip. In this study, we clarified the longitudinal-torsional vibration controllability of the developed ultrasonic vibration source. Moreover, we clarified that using the planar locus of the developed vibration source produced a higher weld strength than our previous studies, and clarified the optimal shape of the vibration locus.

  5. Mathematical Modelling and Parameter Identification of an Electro-Magneto-Mechanical Actuator for Vibration Control

    DEFF Research Database (Denmark)

    Darula, Radoslav; Stein, George Juraj; Kallesøe, Carsten Skovmose

    2012-01-01

    Electromechanical systems for vibration control exhibit complex non-linear behaviour. Therefore advanced mathematical tools and appropriate simplifications are required for their modelling. To properly understand the dynamics of such a non-linear system, it is necessary to identify the parameters....... The electric circuit is closed with a shunt resistance connected to the electromagnet. The current induced in the circuit generates additional alternating magnetic force. This force counteracts the original vibration and damps it. In this way the coupled electro-magneto-mechanical system suppresses the forced...

  6. Single-molecule electronics: Cooling individual vibrational modes by the tunneling current.

    Science.gov (United States)

    Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C

    2016-03-21

    Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.

  7. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Martin E. Cobern

    2004-08-31

    The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed.

  8. Innovative Techniques Simplify Vibration Analysis

    Science.gov (United States)

    2010-01-01

    In the early years of development, Marshall Space Flight Center engineers encountered challenges related to components in the space shuttle main engine. To assess the problems, they evaluated the effects of vibration and oscillation. To enhance the method of vibration signal analysis, Marshall awarded Small Business Innovation Research (SBIR) contracts to AI Signal Research, Inc. (ASRI), in Huntsville, Alabama. ASRI developed a software package called PC-SIGNAL that NASA now employs on a daily basis, and in 2009, the PKP-Module won Marshall s Software of the Year award. The technology is also used in many industries: aircraft and helicopter, rocket engine manufacturing, transportation, and nuclear power."

  9. Quantum dynamics of vibrational excitations and vibrational charge ...

    Indian Academy of Sciences (India)

    Quantum mechanical study of vibrational state-resolved differential cross sections and transition probabilities for both the elastic/inelastic and the charge transfer processes have been carried out in the H+ + O2 collisions at the experimental collision energy of 23 eV. The quantum dynamics has been performed within the ...

  10. Quantum dynamics of vibrational excitations and vibrational charge ...

    Indian Academy of Sciences (India)

    Administrator

    + O2 collisions at the experimental collision energy of 23 eV. The quantum dynamics has been performed within the vibrational close-coupling rotational infinite-order sudden approximation frame- work employing our newly obtained quasi-diabatic potential energy surfaces corresponding to the ground and the first excited ...

  11. Flow induced vibrations in arrays of irregularly spaced cylinders

    Science.gov (United States)

    Taub, Gordon; Michelin, Sébastien

    2014-11-01

    Historically the main industrial applications of cylinder arrays in cross flows favored regular arrangements of cylinders. For this reason, most past studies of Flow Induced Vibrations (FIV) in large cylinder arrays have focused on such arrangements. Recently there has been some interest in generating renewable energy using FIV of bluff bodies. In such applications it will likely be beneficial to enhance, rather than suppress FIV. It is not known a priori if regular or irregularly spaced arrays are most adequate for this type of application. In this study, wind tunnel experiments were conducted on one regularly spaced array and four different irregularly spaced arrays of cylinders in a cross flow. Each arrangement of cylinders was examined under eight different orientations to a cross flow ranging between 10 m/s and 17 m/s. The average amplitude of vibration of the cylinders was found to highly depend on arrangement and orientation. The typical amplitude of vibration of the rods in the irregular arrangements were found to be an order of magnitude larger than that of the regular array. A simple model was proposed in order to predict if a given arrangement was likely to produce large oscillations, and the validity of the model was examined. This research was supported by a Marie Curie International Reintegration Grant within the 7th European Community Framework Program (Grant PIRG08-GA-2010-276762).

  12. Measurement of rabbit eardrum vibration through stroboscopic digital holography

    Energy Technology Data Exchange (ETDEWEB)

    De Greef, Daniël; Dirckx, Joris J. J. [University of Antwerp, Laboratory of BioMedical Physics, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)

    2014-05-27

    In this work, we present a setup for high-power single shot stroboscopic digital holography and demonstrate it in an application on rabbit eardrum vibration measurement. The setup is able to make full-field time-resolved measurements of vibrating surfaces with a precision in the nanometer range in a broad frequency range. The height displacement of the measured object is visualized over the entire surface as a function of time. Vibration magnitude and phase maps can be extracted from these data, the latter proving to be very useful to reveal phase delays across the surface. Such deviations from modal motion indicate energy losses due to internal damping, in contrast to purely elastic mechanics. This is of great interest in middle ear mechanics and finite element modelling. In our setup, short laser pulses are fired at selected instants within the surface vibration period and are recorded by a CCD camera. The timing of the pulses and the exposure of the camera are synchronized to the vibration phase by a microprocessor. The high-power frequency-doubled Nd:YAG laser produces pulses containing up to 5 mJ of energy, which is amply sufficient to record single-shot holograms. As the laser pulse length is 8 ns and the smallest time step of the trigger electronics is 1 μs, vibration measurements of frequencies up to 250 kHz are achievable through this method, provided that the maximum vibration amplitude exceeds a few nanometers. In our application, middle ear mechanics, measuring frequencies extend from 5 Hz to 20 kHz. The experimental setup will be presented, as well as results of measurements on a stretched circular rubber membrane and a rabbit's eardrum. Two of the challenges when measuring biological tissues, such as the eardrum, are low reflectivity and fast dehydration. To increase reflectivity, a coating is applied and to counteract the undesirable effects of tissue dehydration, the measurement setup and software have been optimized for speed without

  13. Predicting Statistical Distributions of Footbridge Vibrations

    DEFF Research Database (Denmark)

    Pedersen, Lars; Frier, Christian

    2009-01-01

    The paper considers vibration response of footbridges to pedestrian loading. Employing Newmark and Monte Carlo simulation methods, a statistical distribution of bridge vibration levels is calculated modelling walking parameters such as step frequency and stride length as random variables...

  14. Isotope separation using vibrationally excited molecules

    International Nuclear Information System (INIS)

    1979-01-01

    This invention relates to isotope separation employing isotopically selective vibrational excitation and vibration-translation reactions of the excited particles. Uranium enrichment, using uranium hexafluoride, is a particular embodiment. (U.K.)

  15. Application of eigenfunction orthogonalities to vibration problems

    CSIR Research Space (South Africa)

    Fedotov, I

    2009-07-01

    Full Text Available The modelling of vibration problems is of great importance in engineering. A popular method of analysing such problems is the variational method. The simplest vibration model is represented using the example of a long rod. Two kinds...

  16. Shock and Vibration. Volume 1, Issue 1

    National Research Council Canada - National Science Library

    Pilkey, Walter D

    1994-01-01

    ..., and earthquake engineering. Among the specific areas to be covered are vibration testing and control, vibration condition monitoring and diagnostics, shock hardenings, modal technology, shock testing, data acquisition, fluid...

  17. Ultrasonic vibration for structural health monitoring

    Science.gov (United States)

    Liang, Y.; Yan, F.; Borigo, C.; Rose, J. L.

    2013-01-01

    Guided waves and vibration analysis are two useful techniques in Nondestructive Evaluation and Structural Health Monitoring. Bridging the gap between guided waves and vibration, a novel testing method ultrasonic vibration is demonstrated here. Ultrasonic vibration is capable to achieve defect detection sensitivity as ultrasonic guided waves, while maintaining the efficiency of traditional vibration in the way of adopting several sensors to cover the whole structure. In this new method, continuous guided wave energy will impinge into the structure to make the structure vibrate steadily. The steady state vibration is achieved after multiple boundary reflections of the continuous guided wave. In ultrasonic vibration experiments, annual array transducer is used as the actuator. The loading functions are tuned by the frequencies and phase delays among each transducer element. Experiments demonstrate good defect detection ability of by optimally selecting guided wave loadings.

  18. Vibrations on board and health effects

    DEFF Research Database (Denmark)

    Jensen, Anker; Jepsen, Jørgen Riis

    2014-01-01

    There is only limited knowledge of the exposure to vibrations of ships’ crews and their risk of vibration-induced health effects. Exposure to hand-arm vibrations from the use of vibrating tools at sea does not differ from that in the land-based trades. However, in contrast to most other work places......, seafarers are also exposed to vibrations to the feet when standing on vibrating surfaces onboard. Anecdotal reports have related the development of “white feet” to local exposure to vibration, e.g. in mining, but this connection has not been investigated in the maritime setting. As known from studies...... for such relation among seafarers except for fishermen, who, however, are also exposed to additional recognised physical risk factors at work. The assessment and reduction of vibrations by naval architects relates to technical implications of this impact for the ships’ construction, but has limited value...

  19. Active and passive vibration isolation in piezoelectric phononic rods with external voltage excitation

    Directory of Open Access Journals (Sweden)

    Qicheng Zhang

    2017-05-01

    Full Text Available Active piezoelectric materials are applied to one-dimensional phononic crystals, for the control of longitudinal vibration propagation both in active and passive modes. Based on the electromechanical coupling between the acoustical vibration and electric field, the electromechanical equivalent method is taken to theoretically predict the transmission spectrum of the longitudinal vibration. It is shown that the phononic rod can suppress the vibration efficiently at the frequencies of interest, by actively optimizing the motions of piezoelectric elements. In an illustrated phononic rod of 11.2cm long, active tunable isolations of more than 20dB at low frequencies (500Hz-14kHz are generated by controlling the excitation voltages of piezoelectric elements. Meanwhile, passive fixed isolation at high frequencies (14k-63kHz are presented by its periodicity characteristics. Finite element simulations and vibration experiments on the rod demonstrate the effectiveness of the approach in terms of its vibration isolation capabilities and tunable characteristics. This phononic rod can be manufactured easily and provides numerous potential applications in designing isolation mounts and platforms.

  20. Active vibration control of thin-plate structures with partial SCLD treatment

    Science.gov (United States)

    Lu, Jun; Wang, Pan; Zhan, Zhenfei

    2017-02-01

    To effectively suppress the low-frequency vibration of a thin-plate, the strategy adopted is to develop a model-based approach to the investigation on the active vibration control of a clamped-clamped plate with partial SCLD treatment. Firstly, a finite element model is developed based on the constitutive equations of elastic, piezoelectric and viscoelastic materials. The characteristics of viscoelastic materials varying with temperature and frequency are described by GHM damping model. A low-dimensional real modal control model which can be used as the basis for active vibration control is then obtained from the combined reduction. The emphasis is placed on the feedback control system to attenuate the vibration of plates with SCLD treatments. A modal controller in conjunction with modal state estimator is designed to solve the problem of full state feedback, making it much more feasible to real-time control. Finally, the theoretical model is verified by modal test, and an active vibration control is validated by hardware-in-the-loop experiment under different external excitations. The numerical and experimental study demonstrate how the piezoelectric actuators actively control the lower modes (first bending and torsional modes) using modal controller, while the higher frequency vibration attenuated by viscoelastic passive damping layer.

  1. Vibration analysis of primary inlet pipe line during steady state and transient conditions of Pakistan research reactor-1

    International Nuclear Information System (INIS)

    Ayazuddin, S.K.; Qureshi, A.A.; Hayat, T.

    1997-11-01

    The Primary Water Inlet Pipeline (PW-IPL) is of stainless steel conveying demineralized water from hold-up tank to the reactor pool of Pakistan Research Reactor-1 (PARR-1). The section of the pipeline from heat exchangers to the valve pit is hanger supported in the pump room and the rest of the section from valve pit to the reactor pool is embedded. The PW-IPL is subjected to steady state and transient vibrations. The reactor pumps, which drive the coolant through various circuits mainly contribute the steady state vibrations, while transient vibrations arise due to instant closure of the check valve (water hammer). The ASME Boiler and Pressure Vessel code provides data about the acceptable limits of stresses related to the primary static stress due to steady state vibrations. However, due to complexity in the pipe structure, stresses related to the transient vibrations are neglected in the code. In this report attempt has been made to analyzed both steady state and transient vibrations of PW-IPL of PARR-1. Since, both the steady state and transient vibrations affect the hanger-supported section of the PW-IPL, therefore, it was selected for vibration test measurements. In the analysis vibration data was compared with the allowable limits and estimations of maximum pressure build-up, eflection, natural frequency, tensile and shear load on hanger support, and the ratio of maximum combine stress to the allowable load were made. (author)

  2. Flow-induced vibration and fretting-wear damage in a moisture separator reheater

    International Nuclear Information System (INIS)

    Pettigrew, M.J.; Taylor, C.E.; Fisher, N.J.

    1996-01-01

    Tube failures due to excessive flow-induced vibration were experienced in the tube bundles of moisture separator reheaters in a BWR nuclear station. This paper presents the results of a root cause analysis and covers recommendations for continued operation and for replacement tube bundles. The following tasks are discussed: tube failure analysis; flow velocity distribution calculations; flow-induced vibration analysis with particular emphasis on finned-tubes; fretting-wear testing of a tube and tube-support material combination under simulated operating conditions; field measurements of flow-induced vibration; and development of vibration specifications for replacement tube bundles. The effect of transient operating conditions and of other operational changes such as tube fouling were considered in the analysis. This paper outlines a typical field problem and illustrates the application of flow-induced vibration technology for the solution of a practical problem

  3. Dynamic Analysis and Vibration Attenuation of Cable-Driven Parallel Manipulators for Large Workspace Applications

    Directory of Open Access Journals (Sweden)

    Jingli Du

    2013-01-01

    Full Text Available Cable-driven parallel manipulators are one of the best solutions to achieving large workspace since flexible cables can be easily stored on reels. However, due to the negligible flexural stiffness of cables, long cables will unavoidably vibrate during operation for large workspace applications. In this paper a finite element model for cable-driven parallel manipulators is proposed to mimic small amplitude vibration of cables around their desired position. Output feedback of the cable tension variation at the end of the end-effector is utilized to design the vibration attenuation controller which aims at attenuating the vibration of cables by slightly varying the cable length, thus decreasing its effect on the end-effector. When cable vibration is attenuated, motion controller could be designed for implementing precise large motion to track given trajectories. A numerical example is presented to demonstrate the dynamic model and the control algorithm.

  4. Flow induced vibrations of the CLIC X-Band accelerating structures

    CERN Document Server

    Charles, Tessa; Boland, Mark; Riddone, Germana; Samoshkin, Alexandre

    2011-01-01

    Turbulent cooling water in the Compact Linear Collider (CLIC) accelerating structures will inevitably induce some vibrations. The maximum acceptable amplitude of vibrations is small, as vibrations in the accelerating structure could lead to beam jitter and alignment difficulties. A Finite Element Analysis model is needed to identify the conditions under which turbulent instabilities and significant vibrations are induced. Due to the orders of magnitude difference between the fluid motion and the structure’s motion, small vibrations of the structure will not contribute to the turbulence of the cooling fluid. Therefore the resonant conditions of the cooling channels presented in this paper, directly identify the natural frequencies of the accelerating structures to be avoided under normal operating conditions. In this paper a 2D model of the cooling channel is presented finding spots of turbulence being formed from a shear layer instability. This effect is observed through direct visualization and wavelet ana...

  5. Optimal Search Strategy of Robotic Assembly Based on Neural Vibration Learning

    Directory of Open Access Journals (Sweden)

    Lejla Banjanovic-Mehmedovic

    2011-01-01

    Full Text Available This paper presents implementation of optimal search strategy (OSS in verification of assembly process based on neural vibration learning. The application problem is the complex robot assembly of miniature parts in the example of mating the gears of one multistage planetary speed reducer. Assembly of tube over the planetary gears was noticed as the most difficult problem of overall assembly. The favourable influence of vibration and rotation movement on compensation of tolerance was also observed. With the proposed neural-network-based learning algorithm, it is possible to find extended scope of vibration state parameter. Using optimal search strategy based on minimal distance path between vibration parameter stage sets (amplitude and frequencies of robots gripe vibration and recovery parameter algorithm, we can improve the robot assembly behaviour, that is, allow the fastest possible way of mating. We have verified by using simulation programs that search strategy is suitable for the situation of unexpected events due to uncertainties.

  6. Analysis of whole-body vibration on rheological models for tissues

    Science.gov (United States)

    Neamţu, A.; Simoiu, D.; Nyaguly, E.; Crastiu, I.; Bereteu, L.

    2018-01-01

    Whole body vibrations have become a very popular method in recent years, both in physical therapy and in sports. This popularity is due to the fact that, as a result of analyzing the groups of subjects, the effects of small amplitude vibration and low frequency vibration, it was found an increase in the force developed by the feet, a hardening of bone strength or an increase in bone density. In this paper we propose to give a possible explanation of the stress relieving in muscle and/or bone after whole body vibration treatment. To do this we consider some rheological models which after whole body vibrations and after the analysis of their response lead to various experiments.

  7. Modeling and Design of Anti-Impact Vibration System for Clamp-On Optical Current Transformers

    Science.gov (United States)

    Ye, Yuan-bo; Zheng, Hao; Wang, Wei; Wang, Gui-zhong; Li, Hong-bo; Zhang, Guo-qing

    2018-02-01

    Optical current transformers, which possess excellent transient characteristics, are able to accurately reflect the full waveform of primary current, and have a wide range of potential applications. The clamp is the sensing unit of the optical current transformer that is mounted directly to the gas-insulated switchgear (GIS) casing and has advantages such as simple structure and ease of maintenance. However, vibration of the casing due to the operation of the GIS circuit breaker has a significant effect on the output of the optical current transformer, and may cause the malfunction of protective relays. This paper proposes the use of damping rubber as the main means of reducing vibration in transformers. A vibration damping system for the clamp-on optical current transformer was designed using the optimal parameters obtained from the modeling and analysis of an anti-impact vibration system. A test system was set up to perform experiments on the designed vibration damping system.

  8. Coupled Vibration of Unshrouded Centrifugal Compressor Impellers. Part II: Computation of Vibration Behavior

    Directory of Open Access Journals (Sweden)

    Dirk Hagelstein

    2000-01-01

    Full Text Available The increased use of small gas turbines and turbochargers in different technical fields has led to the development of highly-loaded centrifugal compressors with extremely thin blades. Due to high rotational speed and the correspondingly high centrifugal loads, the shape of the impeller hub must also be optimized. This has led to a reduction of the thickness of the impeller disc in the outlet region. The thin parts of the impeller are very sensitive and may be damaged by the excitation of dangerous blade vibrations.

  9. Suppression of exchange bias effect in maghemite nanoparticles functionalized with H{sub 2}Y

    Energy Technology Data Exchange (ETDEWEB)

    Guivar, Juan A. Ramos, E-mail: juan.ramos5@unmsm.edu.pe [Faculty of Physical Sciences, National University of San Marcos, P. O. Box 14-0149, Lima, 14 Peru (Peru); Morales, M.A. [Departamento de Física Teórica e Experimental, UFRN, Natal, RN, 59078-970 Brazil (Brazil); Litterst, F. Jochen [Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, Braunschweig, 38110 Germany (Germany)

    2016-12-15

    The structural, vibrational, morphological and magnetic properties of maghemite (γ-Fe{sub 2}O{sub 3}) nanoparticles functionalized with polar molecules EDTA(or H{sub 4}Y) and H{sub 2}Y are reported. The samples were functionalized before and after total synthesis of γ-Fe{sub 2}O{sub 3} nanoparticles. The molecules are anchored on the monodentate mode on the nanoparticles surface. Transmission electron microscopy (TEM) revealed the formation of maghemite nanoparticles with small diameter of 4 nm for the sample functionalized upon synthesis and 7.6 and 6.9 nm for the samples functionalized with EDTA and H{sub 2}Y after the formation of nanoparticles. Exchange bias phenomena were observed in some of the samples functionalized with EDTA at temperatures below 70 K. The presence of the bias effect was discussed in terms of the formation of a thin layer of a secondary phase like lepidocrocite, and the absence of this effect was explained in terms of the chemisorption of carboxylic groups from EDTA which suppressed the canting. Studies of Mössbauer spectroscopy as a function of temperature showed slow relaxation effects and allowed discussion of the secondary phase. In the M–T curves a maximum around 116 K was associated with this secondary phase also in agreement with the Mössbauer studies. The dynamic properties were studied by AC susceptibility, the out of phase signal revealed a spin glass like regime below 36.5 K. - Highlights: • Coprecipitation in alkaline medium was used for the synthesis of EDTA functionalized small maghemite nanoparticles. • Exchange bias effect was observed due to a thin layer of lepidocrocite like second phase. • The sample coprecipitated in a weak base did not show exchange bias effect. • The bias effect is discussed in terms of suppression of canting due to chemisorption of carboxylic groups from EDTA.

  10. Resonant vibration control of rotating beams

    DEFF Research Database (Denmark)

    Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker

    2011-01-01

    Rotatingstructures,like e.g.wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor–actuator system, governed by a resonant controller. The theory is here demonstrated...... modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency....

  11. Moving contact lines on vibrating surfaces

    Science.gov (United States)

    Solomenko, Zlatko; Spelt, Peter; Scott, Julian

    2017-11-01

    Large-scale simulations of flows with moving contact lines for realistic conditions generally requires a subgrid scale model (analyses based on matched asymptotics) to account for the unresolved part of the flow, given the large range of length scales involved near contact lines. Existing models for the interface shape in the contact-line region are primarily for steady flows on homogeneous substrates, with encouraging results in 3D simulations. Introduction of complexities would require further investigation of the contact-line region, however. Here we study flows with moving contact lines on planar substrates subject to vibrations, with applications in controlling wetting/dewetting. The challenge here is to determine the change in interface shape near contact lines due to vibrations. To develop further insight, 2D direct numerical simulations (wherein the flow is resolved down to an imposed slip length) have been performed to enable comparison with asymptotic theory, which is also developed further. Perspectives will also be presented on the final objective of the work, which is to develop a subgrid scale model that can be utilized in large-scale simulations. The authors gratefully acknowledge the ANR for financial support (ANR-15-CE08-0031) and the meso-centre FLMSN for use of computational resources. This work was Granted access to the HPC resources of CINES under the allocation A0012B06893 made by GENCI.

  12. Vibrational spectroscopic study of sulphated silk proteins

    Science.gov (United States)

    Monti, P.; Freddi, G.; Arosio, C.; Tsukada, M.; Arai, T.; Taddei, P.

    2007-05-01

    Degummed Bombyx mori ( B. m.) silk fibroin fabric and mutant naked pupa cocoons (Nd-s) consisting of almost pure silk sericin were treated with chlorosulphonic acid in pyridine and investigated by FT-IR and FT-Raman spectroscopies. Untreated silk fibroin and sericin displayed typical spectral features due to characteristic amino acid composition and molecular conformation (prevailing β-sheet with a less ordered structure in sericin). Upon sulphation, the degree of molecular disorder increased in both proteins and new bands appeared. The IR bands at 1049 and 1014 cm -1 were attributed to vibrations of sulphate salts and that at 1385 cm -1 to the νasSO 2 mode of organic covalent sulphates. In the 1300-1180 cm -1 range various contributions of alkyl and aryl sulphate salts, sulphonamides, sulphoamines and organic covalent sulphates, fell. Fibroin covalently bound sulphate groups through the hydroxyl groups of tyrosine and serine, while sericin through the hydroxyl groups of serine, since the δOH vibrations at 1399 cm -1 in IR and at 1408 cm -1 in Raman disappeared almost completely. Finally, the increase of the I850/ I830 intensity ratio of Raman tyrosine doublet in fibroin suggested a change towards a more exposed state of tyrosine residues, in good agreement with the more disordered conformation taken upon sulphation.

  13. OPTIMAL AUTOMOBILE MUFFLER VIBRATION AND NOISE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Sujit Kumar Jha

    2013-06-01

    Full Text Available The muffler is the main part of the Automobile Exhaust System, consisting of fibrous and porous materials to absorb noise and vibrations. The exhaust gas mass coming from the engine can produce resonance, which may be the source of fatigue failure in the exhaust pipe due to the presence of continuous resonance. The modes on the muffler should be located away from the engine’s operating frequencies in order to minimise the resonance. The objective of this paper is to determine the frequencies that appear at the modes, which have the more adverse effect during the operation of the automobile. An impact test has been conducted by applying the force using a hard head hammer, and data generated have been used for plotting a graph of the transfer functions using MATLAB. Six points have been selected, namely 1, 2, 3, 4, 7, and 11 on the muffler for the impact test. The collected data from theses six points have been analysed for the addition of damping. Results suggests that increasing the mass increases the damping and lowers the modes of the transfer function. Further research will identify higher strength materials that can withstand the higher gas temperatures as well as the corrosion and erosion by the gas emitted from the engine. muffler, noise, vibration,modal analysis,

  14. Vibration measurement with nonlinear converter in the presence of noise

    Science.gov (United States)

    Mozuras, Almantas

    2017-10-01

    Conventional vibration measurement methods use the linear properties of physical converters. These methods are strongly influenced by nonlinear distortions, because ideal linear converters are not available. Practically, any converter can be considered as a linear one, when an output signal is very small. However, the influence of noise increases significantly and signal-to-noise ratio decreases at lower signals. When the output signal is increasing, the nonlinear distortions are also augmenting. If the wide spectrum vibration is measured, conventional methods face a harmonic distortion as well as intermodulation effects. Purpose of this research is to develop a measurement method of wide spectrum vibration by using a converter described by a nonlinear function of type f(x), where x =x(t) denotes the dependence of coordinate x on time t due to the vibration. Parameter x(t) describing the vibration is expressed as Fourier series. The spectral components of the converter output f(x(t)) are determined by using Fourier transform. The obtained system of nonlinear equations is solved using the least squares technique that permits to find x(t) in the presence of noise. This method allows one to carry out the absolute or relative vibration measurements. High resistance to noise is typical for the absolute vibration measurement, but it is necessary to know the Taylor expansion coefficients of the function f(x). If the Taylor expansion is not known, the relative measurement of vibration parameters is also possible, but with lower resistance to noise. This method allows one to eliminate the influence of nonlinear distortions to the measurement results, and consequently to eliminate harmonic distortion and intermodulation effects. The use of nonlinear properties of the converter for measurement gives some advantages related to an increased frequency range of the output signal (consequently increasing the number of equations) that allows one to decrease the noise influence on

  15. Nozzle Flow with Vibrational Nonequilibrium. Ph.D. Thesis

    Science.gov (United States)

    Landry, John Gary

    1995-01-01

    Flow of nitrogen gas through a converging-diverging nozzle is simulated. The flow is modeled using the Navier-Stokes equations that have been modified for vibrational nonequilibrium. The energy equation is replaced by two equations. One equation accounts for energy effects due to the translational and rotational degrees of freedom, and the other accounts for the affects due to the vibrational degree of freedom. The energy equations are coupled by a relaxation time which measures the time required for the vibrational energy component to equilibrate with the translational and rotational energy components. An improved relaxation time is used in this thesis. The equations are solved numerically using the Steger-Warming flux vector splitting method and the Implicit MacCormack method. The results show that uniform flow is produced outside of the boundary layer. Nonequilibrium exists in both the converging and diverging nozzle sections. The boundary layer region is characterized by a marked increase in translational-rotational temperature. The vibrational temperature remains frozen downstream of the nozzle, except in the boundary layer.

  16. How to suppress obsessive thoughts.

    Science.gov (United States)

    Rassin, Eric; Diepstraten, Philip

    2003-01-01

    Thought suppression (i.e. consciously trying to avoid certain thoughts from entering consciousness) has been argued to be an inadequate strategy in case of unwanted intrusions. That is, thought suppression seems to result in more rather than less intrusions. Although this experimental finding has been explained in terms of failing attempts to distract oneself from the target thought, the White Bear Suppression Inventory (WBSI; a scale that measures chronic thought suppression tendencies) does not address the means by which respondents try to suppress unwanted thoughts. To examine which strategies of mental control people use to suppress unwanted thoughts, obsessive-compulsive disorder patients (N=47) completed the WBSI, the Thought Control Questionnaire, and two measures of psychopathology. Results suggest that the crucial mechanism in thought suppression may not be distraction, but self-punishment.

  17. Integration Design and Optimization Control of a Dynamic Vibration Absorber for Electric Wheels with In-Wheel Motor

    Directory of Open Access Journals (Sweden)

    Mingchun Liu

    2017-12-01

    Full Text Available This paper presents an integration design scheme and an optimization control strategy for electric wheels to suppress the in-wheel vibration and improve vehicle ride comfort. The in-wheel motor is considered as a dynamic vibration absorber (DVA, which is isolated from the unsprung mass by using a spring and a damper. The proposed DVA system is applicable for both the inner-rotor motor and outer-rotor motor. Parameters of the DVA system are optimized for the typical conditions, by using the particle swarm optimization (PSO algorithm, to achieve an acceptable vibration performance. Further, the DVA actuator force is controlled by using the alterable-domain-based fuzzy control method, to adaptively suppress the wheel vibration and reduce the wallop acting on the in-wheel motor (IWM as well. In addition, a suspension actuator force is also controlled, by using the linear quadratic regulator (LQR method, to enhance the suspension performance and meanwhile improve vehicle ride comfort. Simulation results demonstrate that the proposed DVA system effectively suppresses the wheel vibration and simultaneously reduces the wallop acting on the IWM. Also, the alterable-domain-based fuzzy control method performs better than the conventional ones, and the LQR-based suspension exhibits excellent performance in vehicle ride comfort.

  18. 33 CFR 159.103 - Vibration test.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Vibration test. 159.103 Section...) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.103 Vibration test. The device... subjected to a sinusoidal vibration for a period of 12 hours, 4 hours in each of the x, y, and z planes, at...

  19. 14 CFR 27.907 - Engine vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Engine vibration. 27.907 Section 27.907... STANDARDS: NORMAL CATEGORY ROTORCRAFT Powerplant General § 27.907 Engine vibration. (a) Each engine must be installed to prevent the harmful vibration of any part of the engine or rotorcraft. (b) The addition of the...

  20. 14 CFR 29.251 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 29.251 Section 29.251... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Miscellaneous Flight Requirements § 29.251 Vibration. Each part of the rotorcraft must be free from excessive vibration under each appropriate speed and power...

  1. 14 CFR 29.907 - Engine vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Engine vibration. 29.907 Section 29.907... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.907 Engine vibration. (a) Each engine must be installed to prevent the harmful vibration of any part of the engine or rotorcraft. (b) The...

  2. 14 CFR 27.251 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 27.251 Section 27.251... STANDARDS: NORMAL CATEGORY ROTORCRAFT Flight Miscellaneous Flight Requirements § 27.251 Vibration. Each part of the rotorcraft must be free from excessive vibration under each appropriate speed and power...

  3. 49 CFR 178.608 - Vibration standard.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration standard. 178.608 Section 178.608... Testing of Non-bulk Packagings and Packages § 178.608 Vibration standard. (a) Each packaging must be capable of withstanding, without rupture or leakage, the vibration test procedure outlined in this section...

  4. 14 CFR 33.63 - Vibration.

    Science.gov (United States)

    2010-01-01

    ... and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES Design and Construction; Turbine Aircraft Engines § 33.63 Vibration. Each engine... because of vibration and without imparting excessive vibration forces to the aircraft structure. [Doc. No...

  5. Fourier Analysis Of Vibrations Of Round Structures

    Science.gov (United States)

    Davis, Gary A.

    1990-01-01

    Fourier-series representation developed for analysis of vibrations in complicated, round structures like turbopump impellers. Method eliminates guesswork involved in characterization of shapes of vibrational modes. Easy way to characterize complicated modes, leading to determination of responsiveness of given mode to various forcing functions. Used in conjunction with finite-element numerical simulation of vibrational modes of structure.

  6. Vibration and Sound Damping in Polymers

    Indian Academy of Sciences (India)

    IAS Admin

    Excessive vibrations or loud sounds cause deafness or reduced efficiency of people, wastage of energy and fatigue failure of machines/structures. Hence, unwanted vibrations need to be dampened. This article describes the transmis- sion of vibrations/sound through different materials such as metals and polymers.

  7. Flow induced vibration studies on PFBR control plug components

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, V., E-mail: prakash@igcar.gov.in [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India); Kumar, P. Anup; Anandaraj, M.; Thirumalai, M.; Anandbabu, C.; Rajan, K.K. [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India)

    2012-09-15

    susceptible to flow induced vibrations. Since control plug is partially immersed in hot sodium, the reactor transients are felt by the components, hence it is very much essential to understand the vibration response of the control plug components. The main vibration excitation mechanisms are vortex shedding, turbulence buffeting, fluid-elastic instability, etc. In order to assess the susceptibility of CP internals against flow induced vibrations (FIVs), to measure structural response and to validate the analytical codes developed for FIV analysis of CP along with the assumptions of supports for various CP internals therein, a flow induced vibration testing program was formulated in 1:4 scale model of PFBR CP. As the first phase of this program, experimental modal analysis of CP internals was carried out in air to estimate the modal parameters. Subsequently, flow induced vibration studies were conducted in the 1:4 scale model of CP in water. In this model, size of the tubes, shell and plates are reduced to Vulgar-Fraction-One-Quarter size of the PFBR CP. The stiffness of CP parts is reduced by 4 times and mass decreased by 64 times which results in scaling up of modal frequencies by 4 times. The CP internals in the model were instrumented with accelerometers and strain gages. The studies were conducted in water with flows derived on the basis of velocity similitude. The output signals from the sensors were acquired and analyzed to obtain frequency spectra, overall vibration amplitude and strain values at various locations inside CP. The study carried out confirms the absence of resonance due to flow induced vibration mechanisms for the entire operating range. This paper elucidates the modeling details, similitude criteria, instrumentation employed and experimental results obtained with discussion on results.

  8. Vibration Theory, Vol. 1A

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.

    The present collection of solved problems has been published as a supplement to the textbook Svingningsteori. Bind 1. Lineær svingningsteori,Aalborg tekniske Universitetsforlag, 1991, whicj is used in the introductory course on linear vibration theory that is being given on th e8th semester...

  9. Vibration Damping Circuit Card Assembly

    Science.gov (United States)

    Hunt, Ronald Allen (Inventor)

    2016-01-01

    A vibration damping circuit card assembly includes a populated circuit card having a mass M. A closed metal container is coupled to a surface of the populated circuit card at approximately a geometric center of the populated circuit card. Tungsten balls fill approximately 90% of the metal container with a collective mass of the tungsten balls being approximately (0.07) M.

  10. Vibrational properties of amorphous semiconductors

    International Nuclear Information System (INIS)

    Schulz, P.A.B.

    1985-01-01

    A model for the lattice dynamics of a-Si 1-X N X is introduced. This model is based on a Born hamiltonian, solved in the Bethe lattice approximation. Starting from the local density of vibrational states, we analize the infrared absoption spectra of this material. (author) [pt

  11. Low-Vibration Oscillating Compressor

    Science.gov (United States)

    Studer, P. A.

    1984-01-01

    Oscillating compressor momentum compensated: produces little vibration in its supporting structure. Compressure requires no lubrication and virtually free of wear. Compresses working fluids such as helium, nitrogen or chlorfluorocarbons for Stirling-cycle refrigeration or other purposes. Compressor includes two mutually opposed ferromagnetic pistons of same shape and mass. Electromagnetic flux links both pistons, causing magnetic attraction between them.

  12. Ultrafast vibrations of gold nanorings

    DEFF Research Database (Denmark)

    Kelf, T; Tanaka, Y; Matsuda, O

    2011-01-01

    We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We...

  13. Harmonic vibrations of multispan beams

    DEFF Research Database (Denmark)

    Dyrbye, Claes

    1996-01-01

    Free and forced harmonic vibrations of multispan beams are determined by a method which implies 1 equation regardless of the configuration. The necessary formulas are given in the paper. For beams with simple supports and the same length of all (n) spans, there is a rather big difference between...

  14. Vibrational entropies in metallic alloys

    Science.gov (United States)

    Ozolins, Vidvuds; Asta, Mark; Wolverton, Christopher

    2000-03-01

    Recently, it has been recognized that vibrational entropy can have significant effects on the phase stability of metallic alloys. Using density functional linear response calculations and molecular dynamics simulations we study three representative cases: (i) phase diagram of Al-rich Al-Sc alloys, (ii) stability of precipitate phases in CuAl_2, and (iii) phonon dynamics in bcc Zr. We find large vibrational entropy effects in all cases. In the Al-Sc system, vibrations increase the solid solubility of Sc in Al by decreasing the stability of the L12 (Al_3Sc) phase. This leads to a nearly ten-fold increase in the solid solubility of Sc in Al at T=800 K. In the Cu-Al system, our calculations predict that the tetragonal Laves phase of CuAl2 has 0.35 kB/atom higher vibrational entropy than the cubic CaF_2-type phase (the latter is predicted to be the T=0 K ground state of CuAl_2). This entropy difference causes a structural transformation in CuAl2 precipitates from the fluorite to the tetragonal Laves phase around T=500 K. Finally, we analyze the highly unusual dynamics of anharmonically stabilized bcc Zr, finding large diffuse-scattering intensity streaks between the bcc Bragg peaks.

  15. PREFACE: International Conference on Vibration Problems (ICOVP-2015)

    Science.gov (United States)

    2015-12-01

    150 participants from India and abroad. The infrastructure facilities, administrative help, and financial support provided by Kakatiya University are gratefully acknowledged. The financial support received from Telangana State Council of Higher Education, University Grant Commission (UGC), National Board for Higher Mathematics (NBHM), Department of Atomic Energy (DAE), Ministry of Earth Sciences, and State Bank of Hyderabad are thankfully acknowledged. The thanks are due to all the speakers and participants who have come to this place by performing long journies and facing many inconveniences. Thanks are also due to International Scientific Committee members, reviewers, local organizing committee members, the members of organizing sub committees, supporting staff, research scholars, and the students for their help. This Conference Series is the outcome of the contributions from the conference and is broadly classified into five sections containing the papers from Solid Mechanics (SM), Fluid Mechanics (FM), Mechanical Engineering (ME), Applied Mathematics(AM), and Physics(PH). All efforts have been made to maintain the consiouness and standards that are the Hallmarks of Institute of Physics (IOP). We appreciate the efforts of Dr.B.Sandhya Rani, Dr.G.Rajitha, and Ms. Hari Priya, research scholors in the Department of Mathematics, Kakatiya University for checking the typos and pointing out the numerous errors. We also appreciate Dr.D.Rajaiah and Mr.D.Ranadheer, research scholors, in the Department for their efforts in the preparation of some LaTeX files. International Conference on Vibration Problems (ICOVP-2015).

  16. Effect of shelf aging on vibration transmissibility of anti-vibration gloves

    Science.gov (United States)

    SHIBATA, Nobuyuki

    2017-01-01

    Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 yr of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves. PMID:28978817

  17. Unihemispheric burst suppression

    Directory of Open Access Journals (Sweden)

    Edward C. Mader Jr.

    2014-08-01

    Full Text Available Burst suppression (BS consists of bursts of high-voltage slow and sharp wave activity alternating with periods of background suppression in the electroencephalogram (EEG. When induced by deep anesthesia or encephalopathy, BS is bihemispheric and is often viewed as a non-epileptic phenomenon. In contrast, unihemispheric BS is rare and its clinical significance is poorly understood. We describe here two cases of unihemispheric BS. The first patient is a 56-year-old woman with a left temporoparietal tumor who presented in convulsive status epilepticus. EEG showed left hemispheric BS after clinical seizure termination with lorazepam and propofol. The second patient is a 39-year-old woman with multiple medical problems and a vague history of seizures. After abdominal surgery, she experienced a convulsive seizure prompting treatment with propofol. Her EEG also showed left hemispheric BS. In both cases, increasing the propofol infusion rate resulted in disappearance of unihemispheric BS and clinical improvement. The prevailing view that typical bihemispheric BS is non-epileptic should not be extrapolated automatically to unihemispheric BS. The fact that unihemispheric BS was associated with clinical seizure and resolved with propofol suggests that, in both cases, an epileptic mechanism was responsible for unihemispheric BS.

  18. Dissipation enhanced vibrational sensing in an olfactory molecular switch

    International Nuclear Information System (INIS)

    Chęcińska, Agata; Heaney, Libby; Pollock, Felix A.; Nazir, Ahsan

    2015-01-01

    Motivated by a proposed olfactory mechanism based on a vibrationally activated molecular switch, we study electron transport within a donor-acceptor pair that is coupled to a vibrational mode and embedded in a surrounding environment. We derive a polaron master equation with which we study the dynamics of both the electronic and vibrational degrees of freedom beyond previously employed semiclassical (Marcus-Jortner) rate analyses. We show (i) that in the absence of explicit dissipation of the vibrational mode, the semiclassical approach is generally unable to capture the dynamics predicted by our master equation due to both its assumption of one-way (exponential) electron transfer from donor to acceptor and its neglect of the spectral details of the environment; (ii) that by additionally allowing strong dissipation to act on the odorant vibrational mode, we can recover exponential electron transfer, though typically at a rate that differs from that given by the Marcus-Jortner expression; (iii) that the ability of the molecular switch to discriminate between the presence and absence of the odorant, and its sensitivity to the odorant vibrational frequency, is enhanced significantly in this strong dissipation regime, when compared to the case without mode dissipation; and (iv) that details of the environment absent from previous Marcus-Jortner analyses can also dramatically alter the sensitivity of the molecular switch, in particular, allowing its frequency resolution to be improved. Our results thus demonstrate the constructive role dissipation can play in facilitating sensitive and selective operation in molecular switch devices, as well as the inadequacy of semiclassical rate equations in analysing such behaviour over a wide range of parameters

  19. Impact Vibration Attenuation for a Flexible Robotic Manipulator through Transfer and Dissipation of Energy

    Directory of Open Access Journals (Sweden)

    Yushu Bian

    2013-01-01

    Full Text Available Due to the presence of system flexibility, impact can excite severe large amplitude vibration responses of the flexible robotic manipulator. This impact vibration exhibits characteristics of remarkable nonlinearity and strong energy. The main goal of this study is to put forward an energy-based control method to absorb and attenuate large amplitude impact vibration of the flexible robotic manipulator. The method takes advantage of internal resonance and is implemented through a vibration absorber based on the transfer and dissipation of energy. The addition of the vibration absorber to the flexible arm generates a coupling effect between vibration modes of the system. By means of analysis on 2:1 internal resonance, the exchange of energy is proven to be existent. The impact vibrational energy can be transferred from the arm to the absorber and dissipated through the damping of the absorber. The results of numerical simulations are promising and preliminarily verify that the method is feasible and can be used to combat large amplitude impact vibration of the flexible manipulator undergoing rigid motion.

  20. FLOW-INDUCED VIBRATION IN PIPES: CHALLENGESS AND SOLUTIONS - A REVIEW

    Directory of Open Access Journals (Sweden)

    M. SIBA

    2016-03-01

    Full Text Available The Flow-induced vibration has recently been the topic of experimental, numerical, and theoretical studies. It was intended to implement better applications for controlling the flow using orifice technique. Having the flow under control, the orifice becomes an instrument for measuring the flow. The flow of all fluid such as water, oil, gas and vapours through an orifice was tested and mathematical models were developed adequately. The basic theme for these enormous studies was the need for the very accurate flow measurements through orifices. All experimental, theoretical, numerical, and analytical studies have agreed that there is more than one avenue to develop, modify, and enhance such measurements. However, one factor that affects the flow measurements is the vibration which was not treated as required until the mid-20th century due to enormous discoveries that damages could be rooted to vibration. Researchers have studied vibration and then proposed mathematical models in conjunction with the pressure and velocity measurements of the flowing fluids and then the effect of the vibration, induced or not induced, has been under continuous investigation. This paper is an attempt to review the previous studies regarding understanding the nature of the vibration and the possible effects of vibration on the flow and on the piping structure in order to limit the damage caused by the vibration. This study shows that the need for more experimental studies and more comprehensive analytical approaches are, in particular, very essential to develop better results.

  1. ROBUST MIXED H2/H8 ACTIVE VIBRATION CONTROLLER IN ATTENUATION OF SMART BEAM

    Directory of Open Access Journals (Sweden)

    Atta Oveisi

    2014-12-01

    Full Text Available The lack of robustness of the mechanical systems due to the unmodeled dynamics and the external disturbances withholds the performance and optimality of the structures. In this paper, this deficiency is obviated in order to reach the desired robust stability and performance on smart structures. For this purpose a multi-objective robust control strategy is proposed for vibration suppression of a clamped-free smart beam with piezoelectric actuator and vibrometer sensor in an LMI framework which is capable of handling weighted exogenous input signals and provides desired pole placement and robust performance at the same time. An accurate model of a homogeneous beam is derived by means of the finite element modal analysis. Then a low order modal system is considered as the nominal model and remaining modes are left as the multiplicative unstructured uncertainty. Next, a robust controller with a regional pole placement constraint is designed based on the augmented plant composed of the nominal model and its accompanied uncertainty by solving a convex optimization problem. Finally, the robustness of the uncertain closed-loop model and the effect of performance index weights on the system output are investigated both in simulation and practice.

  2. Kalman filtering to suppress spurious signals in Adaptive Optics control

    Energy Technology Data Exchange (ETDEWEB)

    Poyneer, L; Veran, J P

    2010-03-29

    In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.

  3. Noise and Vibrations Measurements. External noise and vibrations measurements for offshore SODAR application

    International Nuclear Information System (INIS)

    Ormel, F.T.; Eecen, P.J.; Herman, S.A.

    2003-10-01

    The partners in the WISE project investigate whether application of the SODAR (sonic detection and ranging) measurement technique in wind energy experimental work is feasible as a replacement for cup anemometers, wind direction sensors and tall meteorological masts. In Work Package 2 of the WISE project extensive controlled experiments with the SODAR are performed. For example SODAR measurements are compared with measurements from nearby masts and different brands of SODARs are compared. Part of the work package is the measurement of vibration and noise on an offshore SODAR system. The results of these measurements are presented in this report. ECN performed measurements at an offshore location to investigate the influence of noise and vibrations on the performance of a MiniSODAR measurement system. The aim of the measurements is to quantify the effect of these external noise and vibrations disturbances on the MiniSODAR's performance. Measurements on an identical SODAR system onshore are carried out to compare the disturbances of offshore and onshore external conditions. The effect of background noise on SODAR operation has clearly been established in literature. Therefore, measurements have been performed only to establish the absolute sound pressure levels. This is done at the Measuring Platform Noordwijk (MPN) located in the North Sea, nine kilometres out of the coast at Noordwijk, The Netherlands, and at two locations onshore. At the MPN-platform, the SODAR has been moved from the middle deck to the upper deck to diminish the influence of the diesel generator needed for the electric powering of the island. Although the absolute sound pressure level became higher at the new location, this level became lower at the most important frequencies inside the SODAR, due to the use of absorbing foam. With regards to the sound pressure level the move improved the situation. The sound pressure levels measured offshore were 6 to 15 dB higher than for the two locations

  4. Experience in WWER fuel assemblies vibration analysis

    International Nuclear Information System (INIS)

    Ovtcharov, O.; Pavelko, V.; Usanov, A.; Arkadov, G.; Dolgov, A.; Molchanov, V.

    2003-01-01

    It is stated that the vibration studies of internals and the fuel assemblies should be conducted during the reactor designing, commissioning and commercial operation stages and the analysis methods being used should complement each other. The present paper describes the methods and main results of the vibration noise studies of internals and the fuel assemblies of the operating NPPs with WWER reactors, as an example of the implementation of the comprehensive approach to the analysis on equipment flow-induced vibration. At that, the characteristics of internals and fuel assemblies vibration loading were dealt jointly as they are elements of the same compound oscillating system and their vibrations have the interrelated nature

  5. Vibrational Spectroscopy of the CCl[subscript 4] v[subscript 1] Mode: Theoretical Prediction of Isotopic Effects

    Science.gov (United States)

    Gaynor, James D.; Wetterer, Anna M.; Cochran, Rea M.; Valente, Edward J.; Mayer, Steven G.

    2015-01-01

    Raman spectroscopy is a powerful experimental technique, yet it is often missing from the undergraduate physical chemistry laboratory curriculum. Tetrachloromethane (CCl[subscript 4]) is the ideal molecule for an introductory vibrational spectroscopy experiment and the symmetric stretch vibration contains fine structure due to isotopic variations…

  6. Design of a candidate vibrational signal for mating disruption against the glassy-winged sharpshooter, Homalodisca Vitripennis

    Science.gov (United States)

    The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is an important pest of grapevines due to its ability to transmit Xylella fastidiosa, the causal agent of Pierce’s disease. GWSS mating communication is based on vibrational signals; therefore, vibrational mating disruption could be an ...

  7. Nuclear surface vibrations in bag models

    International Nuclear Information System (INIS)

    Tomio, L.

    1984-01-01

    The main difficulties found in the hadron bag models are reviewed from the original version of the MIT bag model. Following, with the aim to answer two of the main difficulties in bag models, viz., the parity and the divergence illness, a dynamical model is presented. In the model, the confinement surface of the quarks (bag) is treated like a real physical object which interacts with the quarks and is exposed to vibrations. The model is applied to the nucleon, being observed that his spectrum, in the first excited levels, can be reproduced with resonable precision and obeying to the correct parity order. In the same way that in a similar work of Brown et al., it is observed to be instrumental the inclusion of the effect due to pions. (L.C.) [pt

  8. Structural Vibration Monitoring Using Cumulative Spectral Analysis

    Directory of Open Access Journals (Sweden)

    Satoru Goto

    2013-01-01

    Full Text Available This paper describes a resonance decay estimation for structural health monitoring in the presence of nonstationary vibrations. In structural health monitoring, the structure's frequency response and resonant decay characteristics are very important for understanding how the structure changes. Cumulative spectral analysis (CSA estimates the frequency decay by using the impulse response. However, measuring the impulse response of buildings is impractical due to the need to shake the building itself. In a previous study, we reported on system damping monitoring using cumulative harmonic analysis (CHA, which is based on CSA. The current study describes scale model experiments on estimating the hidden resonance decay under non-stationary noise conditions by using CSA for structural condition monitoring.

  9. Damping of wind turbine tower vibrations

    DEFF Research Database (Denmark)

    Brodersen, Mark Laier; Pedersen, Mikkel Melters

    Damping of wind turbine vibrations by supplemental dampers is a key ingredient for the continuous use of monopiles as support for offshore wind turbines. The present thesis consists of an extended summary with four parts and appended papers [P1-P4] concerning novel strategies for damping of tower...... in a stroke amplifying brace, which amplifies the displacement across the damper and thus reduces the desired level of damper force. For optimal damping of the two lowest tower modes, a novel toggle-brace concept for amplifying the bending deformation of the tower is presented. Numerical examples illustrate...... damper with IFFis validated by a series of real time hybrid simulations (RTHS). The experimental results illustrate the ability of the hybrid damper concept to increase damper stroke or attainable damping. The results also show that the actuator signal is quitesensitive to drift due an offset...

  10. Dissipation in vibrating superleak second sound transducers

    International Nuclear Information System (INIS)

    Giordano, N.

    1985-01-01

    We have performed an experimental study of the generation and detection of second sound in 4 He using vibrating superleak second sound transducers. At temperatures well below T/sub lambda/ and for low driving amplitudes, the magnitude of the generated second sound wave is proportional to the drive amplitude. However, near T/sub lambda/ and for high drive amplitudes this is no longer the case--instead, the second sound amplitude saturates. In this regime we also find that overtones of the drive frequency are generated. Our results suggest that this behavior is due to critical velocity effects in the pores of the superleak in the generator transducer. This type of measurement may prove to be a useful way in which to study critical velocity effects in confined geometries

  11. Nonlinear parametrically excited vibration and active control of gear pair system with time-varying characteristic

    Science.gov (United States)

    Liu, Shuang; Wang, Jin-Jin; Liu, Jin-Jie; Li, Ya-Qian

    2015-10-01

    In the present work, we investigate the nonlinear parametrically excited vibration and active control of a gear pair system involving backlash, time-varying meshing stiffness and static transmission error. Firstly, a gear pair model is established in a strongly nonlinear form, and its nonlinear vibration characteristics are systematically investigated through different approaches. Several complicated phenomena such as period doubling bifurcation, anti period doubling bifurcation and chaos can be observed under the internal parametric excitation. Then, an active compensation controller is designed to suppress the vibration, including the chaos. Finally, the effectiveness of the proposed controller is verified numerically. Project supported by the National Natural Science Foundation of China (Grant No. 61104040), the Natural Science Foundation of Hebei Province, China (Grant No. E2012203090), and the University Innovation Team of Hebei Province Leading Talent Cultivation Project, China (Grant No. LJRC013).

  12. Application of nonlinear magnetic vibro-impact vibration suppressor and energy harvester

    Science.gov (United States)

    Afsharfard, Aref

    2018-01-01

    In the present study, application of a single unit vibro-impact system is improved. For this reason, in the so-called "magnetic impact damper" the impact mass is replaced by a permanent magnet, which moves in coil of gap enclosure. In the magnetic impact damper, wasting energy during inelastic contacts of masses and converting energy into electrical energy during the mass movement inside the coil, leads to suppress undesired vibrations. In this study it is shown that the magnetic impact dampers are not only good vibration suppressors but also they can harvest electrical energy. Effect of changing the main parameters of this system including gap size, load resistance and electromagnetic coupling coefficient is studied on the vibratory and energy behavior of the magnetic impact dampers. Finally using several user oriented charts, it is shown that energy-based and vibration-based design considerations can effectively improve application of the discussed vibro-impact system.

  13. Heat load tests of superconducting magnets vibrated electromagnetically for the Maglev train

    Science.gov (United States)

    Ohmori, J.; Nakao, H.; Yamashita, T.; Sanada, Y.; Shudou, M.; Kawai, M.; Fujita, M.; Terai, M.; Miura, A.

    Superconducting magnets on Maglev trains vibrate due to harmonic ripples of electromagnetic flux generated by ground coils. Heat load caused by vibration in the magnet amounted to several tens of watts in the electromagnetic vibration test. This was mainly because a.c. loss was induced in the helium vessel housing the superconducting coil, due to relative vibration between the aluminium thermal shield and the coil. The heat load caused by vibration should be strictly restricted to less than 4W due to limited cryogenic refrigeration capacity. The heat load was tested using electromagnetic flux ripples for a superconducting magnet model of one coil which corresponds to 1/4 of an actual magnet. The flux ripples simulated the 6th harmonic of the actual ground levitation coil. Some ideas to reduce the heat load were tried for the magnet model, such as applying high resistance thermal radiation shielding, increasing rigidity of the vacuum vessel, and using high purity copper plating on the helium vessel. These ideas proved effective, and the maximum heat load due to vibration was held to less than 4 W per magnet for the one coil magnet model.

  14. Multiple Rabi Splittings under Ultrastrong Vibrational Coupling.

    Science.gov (United States)

    George, Jino; Chervy, Thibault; Shalabney, Atef; Devaux, Eloïse; Hiura, Hidefumi; Genet, Cyriaque; Ebbesen, Thomas W

    2016-10-07

    From the high vibrational dipolar strength offered by molecular liquids, we demonstrate that a molecular vibration can be ultrastrongly coupled to multiple IR cavity modes, with Rabi splittings reaching 24% of the vibration frequencies. As a proof of the ultrastrong coupling regime, our experimental data unambiguously reveal the contributions to the polaritonic dynamics coming from the antiresonant terms in the interaction energy and from the dipolar self-energy of the molecular vibrations themselves. In particular, we measure the opening of a genuine vibrational polaritonic band gap of ca. 60 meV. We also demonstrate that the multimode splitting effect defines a whole vibrational ladder of heavy polaritonic states perfectly resolved. These findings reveal the broad possibilities in the vibrational ultrastrong coupling regime which impact both the optical and the molecular properties of such coupled systems, in particular, in the context of mode-selective chemistry.

  15. Suppression of sympathetic detonation

    Science.gov (United States)

    Foster, J. C., Jr.; Gunger, M. E.; Craig, B. G.; Parsons, G. H.

    1984-08-01

    There are two basic approaches to suppression of sympathetic detonation. Minimizing the shock sensitivity of the explosive to long duration pressure will obviously reduce interround separation distances. However, given that the explosive sensitivity is fixed, then much can be gained through the use of simple barriers placed between the rounds. Researchers devised calculational methods for predicting shock transmission; experimental methods have been developed to characterize explosive shock sensitivity and observe the response of acceptors to barriers. It was shown that both EAK and tritonal can be initiated to detonation with relatively low pressure shocks of long durations. It was also shown that to be an effective barrier between the donor and acceptor, the material must attenuate shock and defect fragments. Future actions will concentrate on refining the design of barriers to minimize weight, volume, and cost.

  16. JUSTIFICATION OF RATIONAL KINEMATIC CHARACTERISTICS OF MOLDING VIBRATING TABLE

    Directory of Open Access Journals (Sweden)

    P. G. Anofriev

    2016-12-01

    oscillators of table, which make it possible to obtain qualitative compaction of dry molding sand in the mold. Practical value. In the process of molding using the lost foam casting models the mold mass is increasing due to the layer-by-layer filling of the mold with molding sand. The change of mass characteristics of the mold requires operational change of the kinematic characteristics of the vibrating table – vibration acceleration. The proposed mathematical model allows determining the ranges of setting the frequency parameters of inertial oscillators of molding table at all stages of molding.

  17. Modal Vibration Control in Periodic Time-Varying Structures with Focus on Rotor Blade Systems

    DEFF Research Database (Denmark)

    Christensen, Rene Hardam; Santos, Ilmar

    2004-01-01

    of active modal controllers. The main aim is to reduce vibrations in periodic time-varying structures. Special emphasis is given to vibration control of coupled bladed rotor systems. A state feedback modal control law is developed based on modal analysis in periodic time-varying structures. The first step...... in the procedure is a transformation of the model into a time-invariant modal form by applying the modal matrices, which are also periodic time-variant. Due to coupled rotor and blade motions complex vibration modes occur in the modal transformed state space model. This implies that the modal transformed model...

  18. Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

    International Nuclear Information System (INIS)

    Uvan Catton; Dhir, Vijay K.; Deepanjan Mitra; Omar Alquaddoomi; Pierangelo Adinolfi

    2004-01-01

    Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers

  19. Changes in the vibrational properties of graphene and other related nanostructures under strain

    International Nuclear Information System (INIS)

    Codorniu Pujals, D.

    2015-01-01

    It is well known that the presence of strain in solids modifies their vibrational properties due to the variation of the atomic position and the changes of the interatomic distances. Monolayer graphene is especially sensible to the effects of strain, for example, to that produced by the curvature of some region of the graphene plane. These changes in the vibrational properties of graphene modifies in different way its Raman spectrum. In the case of other graphene-related materials as fullerenes, nano-onions and nano tubes, the curvature is always present, consequently, there is a modification of the vibrational properties in relation with those in graphene, due to the strain provoked by curvature. In this paper, the overall picture of the effect of strain on the vibrational properties of graphene and other carbon nanostructures is presented from a theoretical point of view and the main considerations are correlated with experimental results from Raman spectroscopy (Author)

  20. Vibration of fusion reactor components with magnetic damping

    Energy Technology Data Exchange (ETDEWEB)

    D’Amico, Gabriele; Portone, Alfredo [Fusion for Energy – Torres Diagonal Litoral B3 – c/Josep Plá n.2, Barcelona (Spain); Rubinacci, Guglielmo [Department of Electrical Eng. and Information Technologies, Università di Napoli Federico II, Via Claudio, 21, 80125 Napoli (Italy); Testoni, Pietro, E-mail: pietro.testoni@f4e.europa.eu [Fusion for Energy – Torres Diagonal Litoral B3 – c/Josep Plá n.2, Barcelona (Spain)

    2016-11-01

    The aim of this paper is to assess the importance of the magnetic damping in the dynamic response of the main plasma facing components of fusion machines, under the strong Lorentz forces due to Vertical Displacement Events. The additional eddy currents due to the vibration of the conducting structures give rise to volume loads acting as damping forces, a kind of viscous damping, being these additional loads proportional to the vibration speed. This effect could play an important role when assessing, for instance, the inertial loads associated to VV movements in case of VDEs. In this paper, we present the results of a novel numerical formulation, in which the field equations are solved by adopting a very effective fully 3D integral formulation, not limited to the analysis of thin shell structures, as already successfully done in several approaches previously published.

  1. Ultrasonic vibration machining of Inconel

    International Nuclear Information System (INIS)

    Park, Myung Ho

    2003-01-01

    Recently, the demand for advanced technology of high precision and high efficiency processing of hard materials such as Inconel is increasing with progress of industrial goods. However, the machinability of Inconel is very inferior to the other conventional industrial materials and the machining technology for Inconel involves many problems to be solved in machining accuracy, machining efficiency, etc. Therefore it is needs to establish the machining technology. The purpose of this study is to develop an advanced ultrasonic vibration machining technology for Inconel, using the 60kHz and 75kHz high frequency, amplitude about 8μm and 4μm, respectively. As the result, this new ultrasonic vibration machining is reasonable and suitable for the high efficient, accuracy machining method of Inconel

  2. A night with good vibrations

    CERN Multimedia

    2002-01-01

    Next week-end, the Geneva Science History Museum invites you to a Science Night under the banner of waves and vibrations. Scientists, artists and storytellers from more than forty institutes and local or regional associations will show that waves and vibrations form an integral part of our environment. You will be able to get in contact with the nature of waves through interactive exhibitions on sound and light and through hands-on demonstrations arranged in the Park of the Perle du Lac. On the CERN stand, you will be able to measure the speed of light with a bar of chocolate, and understand the scattering of waves with plastic ducks. Amazing, no? In addition to the stands, the Night will offer many other activities: reconstructions of experiments, a play, a concert of crystal glasses, an illuminated fountain, a house of spirits. More information Science Night, 6 and 7 July, Park of the Perle du Lac, Geneva

  3. Vibration Analysis via Wireless Network

    Science.gov (United States)

    2007-09-01

    C. RELATED WORK The thesis builds upon the research foundation established by several students at the Naval Postgraduate School. Chimi Zacot [4...reading of a MEMS device in only one coordinate axis, one degree of freedom. To fully understand the vibration of the machinery would require an...the signals between the coordinate axis. Figure 15. Spectral Distance Results for 115V DC Motor with Load Applied. 30 Measured

  4. Optical vibrating-sample magnetometer

    CERN Document Server

    Diaz-Michelena, M; López, E; Sanchez, M C; Aroca, C

    2000-01-01

    A highly sensitive method of detecting vibrations of a cantilever in atomic-force microscopy has been introduced as a detector in an alternating-gradient field magnetometer. Use of light is the success of this system as it is compatible with vacuum systems and closed-flux cryostats. The optical signal is electronically conditioned easily. Experimental results show that highly sensitive measurements can be achieved.

  5. Tool-specific performance of vibration-reducing gloves for attenuating fingers-transmitted vibration

    Science.gov (United States)

    Welcome, Daniel E.; Dong, Ren G.; Xu, Xueyan S.; Warren, Christopher; McDowell, Thomas W.

    2016-01-01

    BACKGROUND Fingers-transmitted vibration can cause vibration-induced white finger. The effectiveness of vibration-reducing (VR) gloves for reducing hand transmitted vibration to the fingers has not been sufficiently examined. OBJECTIVE The objective of this study is to examine tool-specific performance of VR gloves for reducing finger-transmitted vibrations in three orthogonal directions (3D) from powered hand tools. METHODS A transfer function method was used to estimate the tool-specific effectiveness of four typical VR gloves. The transfer functions of the VR glove fingers in three directions were either measured in this study or during a previous study using a 3D laser vibrometer. More than seventy vibration spectra of various tools or machines were used in the estimations. RESULTS When assessed based on frequency-weighted acceleration, the gloves provided little vibration reduction. In some cases, the gloves amplified the vibration by more than 10%, especially the neoprene glove. However, the neoprene glove did the best when the assessment was based on unweighted acceleration. The neoprene glove was able to reduce the vibration by 10% or more of the unweighted vibration for 27 out of the 79 tools. If the dominant vibration of a tool handle or workpiece was in the shear direction relative to the fingers, as observed in the operation of needle scalers, hammer chisels, and bucking bars, the gloves did not reduce the vibration but increased it. CONCLUSIONS This study confirmed that the effectiveness for reducing vibration varied with the gloves and the vibration reduction of each glove depended on tool, vibration direction to the fingers, and finger location. VR gloves, including certified anti-vibration gloves do not provide much vibration reduction when judged based on frequency-weighted acceleration. However, some of the VR gloves can provide more than 10% reduction of the unweighted vibration for some tools or workpieces. Tools and gloves can be matched for

  6. Uncertainty Quantification for Monitoring of Civil Structures from Vibration Measurements

    Science.gov (United States)

    Döhler, Michael; Mevel, Laurent

    2014-05-01

    Health Monitoring of civil structures can be performed by detecting changes in the modal parameters of a structure, or more directly in the measured vibration signals. For a continuous monitoring the excitation of a structure is usually ambient, thus unknown and assumed to be noise. Hence, all estimates from the vibration measurements are realizations of random variables with inherent uncertainty due to (unknown) process and measurement noise and finite data length. In this talk, a strategy for quantifying the uncertainties of modal parameter estimates from a subspace-based system identification approach is presented and the importance of uncertainty quantification in monitoring approaches is shown. Furthermore, a damage detection method is presented, which is based on the direct comparison of the measured vibration signals without estimating modal parameters, while taking the statistical uncertainty in the signals correctly into account. The usefulness of both strategies is illustrated on data from a progressive damage action on a prestressed concrete bridge. References E. Carden and P. Fanning. Vibration based condition monitoring: a review. Structural Health Monitoring, 3(4):355-377, 2004. M. Döhler and L. Mevel. Efficient multi-order uncertainty computation for stochastic subspace identification. Mechanical Systems and Signal Processing, 38(2):346-366, 2013. M. Döhler, L. Mevel, and F. Hille. Subspace-based damage detection under changes in the ambient excitation statistics. Mechanical Systems and Signal Processing, 45(1):207-224, 2014.

  7. Statistical techniques for the identification of reactor component structural vibrations

    International Nuclear Information System (INIS)

    Kemeny, L.G.

    1975-01-01

    The identification, on-line and in near real-time, of the vibration frequencies, modes and amplitudes of selected key reactor structural components and the visual monitoring of these phenomena by nuclear power plant operating staff will serve to further the safety and control philosophy of nuclear systems and lead to design optimisation. The School of Nuclear Engineering has developed a data acquisition system for vibration detection and identification. The system is interfaced with the HIFAR research reactor of the Australian Atomic Energy Commission. The reactor serves to simulate noise and vibrational phenomena which might be pertinent in power reactor situations. The data acquisition system consists of a small computer interfaced with a digital correlator and a Fourier transform unit. An incremental tape recorder is utilised as a backing store and as a means of communication with other computers. A small analogue computer and an analogue statistical analyzer can be used in the pre and post computational analysis of signals which are received from neutron and gamma detectors, thermocouples, accelerometers, hydrophones and strain gauges. Investigations carried out to date include a study of the role of local and global pressure fields due to turbulence in coolant flow and pump impeller induced perturbations on (a) control absorbers, (B) fuel element and (c) coolant external circuit and core tank structure component vibrations. (Auth.)

  8. An equipment test for grading lumber by transverse vibration technique

    Directory of Open Access Journals (Sweden)

    Marcelo Rodrigo Carreira

    2008-08-01

    Full Text Available Due to the great variability of its mechanical properties, the rational use of lumber for structural purposes is directly conditioned to its grading. There are several techniques available for grading structural lumber. The most relevant one is the transverse vibration technique which obtained reliable results in non-destructive evaluation of lumber. The purpose of this work is to present the bases for the mechanical grading of lumber and the results of the calibration test of the frst transverse vibration equipment developed in Brazil. In this research 30 beams of cupiúba (Goupia glabra with nominal dimensions of 5 cm X 10 cm X 300 cm, were used. The tests were accomplished at the Wood and Timber Structures Laboratory (LaMEM of the University of São Paulo (USP. The results showed a strong correlation between the elasticity modulus measured by the static bending test and the one obtained with the transverse vibration equipment, showing the high reliability of the vibration method for the grading of structural lumber. A determination coeffcient (R² of 0.896 was obtained with the Brazilian equipment, showing that it can be used in the grading of lumber.

  9. Vibration Analysis of Composite Beams with Sinusoidal Periodically Varying Interfaces

    Science.gov (United States)

    Li, Botong; Liu, Chein-Shan; Zhu, Liangliang

    2017-12-01

    As an increasing variety of composite materials with complex interfaces are emerging, we develop a theory to investigate composite beams and shed some light on new physical insights into composite beams with sinusoidal periodically varying interfaces. For the natural vibration of composite beams with continuous or periodically varying interfaces, the governing equation has been derived according to the generalised Hamiltonian principle. For composite beams having different boundary conditions, we transform the governing equations into integral equations and solve them by using the sinusoidal functions as test functions as well as the basis of the vibration modes. Due to the orthogonality of the sinusoidal functions, expansion coefficients in closed form can be found. Therefore, the proposed iterative schemes, with the help of the Rayleigh quotient and boundary functions, can quickly find the eigenvalues and free vibration modes. The obtained natural frequencies agree well with those obtained using the finite element method. In addition, the proposed method can be extended easily to laminated composite beams in more general cases or complex components and geometries in vibration engineering. The effects of different material properties of the upper and lower components and varying interface geometry function on the frequency of the composite beams are examined. According to our investigation, the natural frequency of a laminated beam with a continuous or periodically varying interface can be changed by altering the density or elastic modulus. We also show the responses of the frequencies of the components to the varying periodic interface.

  10. Flow induced vibrations in liquid metal fast breeder reactors

    International Nuclear Information System (INIS)

    1989-01-01

    Flow induced vibrations are well known phenomena in industry. Engineers have to estimate their destructive effects on structures. In the nuclear industry, flow induced vibrations are assessed early in the design process, and the results are incorporated in the design procedures. In many cases, model testing is used to supplement the design process to ensure that detrimental behaviour due to flow induced vibrations will not occur in the component in question. While these procedures attempt to minimize the probability of adverse performance of the various components, there is a problem in the extrapolation of analytical design techniques and/or model testing to actual plant operation. Therefore, sodium tests or vibrational measurements of components in the reactor system are used to provide additional assurance. This report is a general survey of experimental and calculational methods in this area of structural mechanics. The report is addressed to specialists and institutions in industrialized and developing countries who are responsible for the design and operation of liquid metal fast breeder reactors. 92 refs, 90 figs, 8 tabs

  11. An Enhanced Piezoelectric Vibration Energy Harvesting System with Macro Fiber Composite

    OpenAIRE

    Zhang, Shuwen; Yan, Bo; Luo, Yajun; Miao, Weikai; Xu, Minglong

    2015-01-01

    Self-power supply is a promising project in various applied conditions. Among this research area, piezoelectric material-based energy harvesting (EH) method has been researched in recent years due to its advantages. With the limitation of energy form acceptance range of EH circuit system, a sum of energy is not accessible to be obtained. To enlarge the EH quantity from the vibration, an enhanced piezoelectric vibration EH structure with piezoelectric film is developed in this work. Piezoelect...

  12. Piezoelectric-based vibration control optimization in nonlinear wood and composite structures

    Science.gov (United States)

    Cao, Jia Long; John, Sabu; Molyneaux, Tom

    2005-05-01

    Vibration control has been a subject of engineering research for the past few decades. Recently, the use of smart material-related components for vibration control has become an alternative to traditional vibration control techniques. Vibration control using such components has many advantages such as lighter overall weight and lower cost. They are especially suitable where traditional techniques cannot be applied due to weight and size restrictions. Passive vibration shunt control using piezoelectric ceramics (PZT) and an electrical network has been studied by many researchers both analytically and experimentally. In this paper, the modeling of a passive vibration shunt control on a cantilever beam using a finite element analysis software package -- ANSYS is presented. It is a useful alternative to an experimental approach that is costly as the PZT is useable only once in most instances. The simulation shows that the electrical shunt circuit can remove considerable vibration-based energy when properly tuned. The simulation reveals that the material property of the structure has a significant impact on the effectiveness of the vibration shunt circuit. This is postulated to be because of the mechanical impedance match between the structure and PZT transducer. The method provides a useful mechanism for selecting the material properties of a structure so that its vibration can be effectively absorbed by a piezoelectric vibration shunt network. Also shown in this paper is experimental verification of the computational results. This procedure has the potential for greatly increasing the flexibility in the design of such Mechatronic control devices especially when the mechanical and physical properties of synthetic materials such as polymeric composite materials can be varied to suit the application.

  13. The sports performance application of vibration exercise for warm-up, flexibility and sprint speed.

    Science.gov (United States)

    Cochrane, Darryl

    2013-01-01

    Since the turn of the 21st century, there has been a resurgence of vibration technology to enhance sport science especially for power and force development. However, vibration exercise has been trialled in other areas that are central to athlete performance such as warm-up, flexibility and sprint speed. Therefore, the aim of this review was to attempt to gain a better understanding of how acute and short-term vibration exercise may impact on warm-up, flexibility and sprint speed. The importance of warming up for sporting performance has been well documented and vibration exercise has the capability to be included or used as a standalone warm-up modality to increase intramuscular temperature at a faster rate compared to other conventional warm-up modalities. However, vibration exercise does not provide any additional neurogenic benefits compared to conventional dynamic and passive warm-up interventions. Vibration exercise appears to be a safe modality that does not produce any adverse affects causing injury or harm and could be used during interval and substitution breaks, as it would incur a low metabolic cost and be time-efficient compared to conventional warm-up modalities. Acute or short-term vibration exercise can enhance flexibility and range of motion without having a detrimental effect on muscle power, however it is less clear which mechanisms may be responsible for this enhancement. It appears that vibration exercise is not capable of improving sprint speed performance; this could be due to the complex and dynamic nature of sprinting where the purported increase in muscle power from vibration exercise is probably lost on repeated actions of high force generation. Vibration exercise is a safe modality that produces no adverse side effects for injury or harm. It has the time-efficient capability of providing coaches, trainers, and exercise specialists with an alternative modality that can be implemented for warm-up and flexibility either in isolation or in

  14. Surveillance of vibrations in PWR

    International Nuclear Information System (INIS)

    Espefaelt, R.; Lorenzen, J.; Aakerhielm, F.

    1980-07-01

    The core of a PWR - including fuel elements, internal structure, control rods and core support structure inside the pressure vessel - is subjected to forces which can cause vibrations. One sensitive means to detect and analyse such vibrations is by means of the noise from incore and excore neutron detector signals. In this project noise recordings have been made on two occasions in the Ringhals 2 plant and the obtained data been analysed using the Studsvik Noise Analysis Program System (SNAPS). The results have been intepreted and a detailed description of the vibrational status of the core and pressure vessel internals has been produced. On the basis of the obtained results it is proposed that neutron signal noise analysis should be performed at each PWR plant in the beginning, middle and end of each fuel cycle and an analysis be made using the methods developed in the project. It would also provide a contribution to a higher degree of preparedness for diagnostic tasks in case of unexpected and abnormal events. (author)

  15. Emotion suppression reduces hippocampal activity during successful memory encoding.

    Science.gov (United States)

    Binder, Julia; de Quervain, Dominique J-F; Friese, Malte; Luechinger, Roger; Boesiger, Peter; Rasch, Björn

    2012-10-15

    People suppressing their emotions while facing an emotional event typically remember it less well. However, the neural mechanisms underlying the impairing effect of emotion suppression on successful memory encoding are not well understood. Because successful memory encoding relies on the hippocampus and the amygdala, we hypothesized that memory impairments due to emotion suppression are associated with down-regulated activity in these brain areas. 59 healthy females were instructed either to simply watch the pictures or to down-regulate their emotions by using a response-focused emotion suppression strategy. Brain activity was recorded using functional magnetic resonance imaging (fMRI), and free recall of pictures was tested afterwards. As expected, suppressing one's emotions resulted in impaired recall of the pictures. On the neural level, the memory impairments were associated with reduced activity in the right hippocampus during successful encoding. No significant effects were observed in the amygdala. In addition, functional connectivity between the hippocampus and the right dorsolateral prefrontal cortex was strongly reduced during emotion suppression, and these reductions predicted free-recall performance. Our results indicate that emotion suppression interferes with memory encoding on the hippocampal level, possibly by decoupling hippocampal and prefrontal encoding processes, suggesting that response-focused emotion suppression might be an adaptive strategy for impairing hippocampal memory formation in highly arousing situations. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Test rig with active damping control for the simultaneous evaluation of vibration control and energy harvesting via piezoelectric transducers

    International Nuclear Information System (INIS)

    Perfetto, S; Rohlfing, J; Infante, F; Mayer, D; Herold, S

    2016-01-01

    Piezoelectric transducers can be used to harvest electrical energy from structural vibrations in order to power continuously operating condition monitoring systems local to where they operate. However, excessive vibrations can compromise the safe operation of mechanical systems. Therefore, absorbers are commonly used to control vibrations. With an integrated device, the mechanical energy that otherwise would be dissipated can be converted via piezoelectric transducers. Vibration absorbers are designed to have high damping factors. Hence, the integration of transducers would lead to a low energy conversion. Efficient energy harvesters usually have low damping capabilities; therefore, they are not effective for vibration suppression. Thus, the design of an integrated device needs to consider the two conflicting requirements on the damping. This study focuses on the development of a laboratory test rig with a host structure and a vibration absorber with tunable damping via an active relative velocity feedback. A voice coil actuator is used for this purpose. To overcome the passive damping effects of the back electromagnetic force a novel voltage feedback control is proposed, which has been validated both in simulation and experimentally. The aim of this study is to have a test rig ready for the introduction of piezo-transducers and available for future experimental evaluations of the damping effect on the effectiveness of vibration reduction and energy harvesting efficiency. (paper)

  17. Test rig with active damping control for the simultaneous evaluation of vibration control and energy harvesting via piezoelectric transducers

    Science.gov (United States)

    Perfetto, S.; Rohlfing, J.; Infante, F.; Mayer, D.; Herold, S.

    2016-09-01

    Piezoelectric transducers can be used to harvest electrical energy from structural vibrations in order to power continuously operating condition monitoring systems local to where they operate. However, excessive vibrations can compromise the safe operation of mechanical systems. Therefore, absorbers are commonly used to control vibrations. With an integrated device, the mechanical energy that otherwise would be dissipated can be converted via piezoelectric transducers. Vibration absorbers are designed to have high damping factors. Hence, the integration of transducers would lead to a low energy conversion. Efficient energy harvesters usually have low damping capabilities; therefore, they are not effective for vibration suppression. Thus, the design of an integrated device needs to consider the two conflicting requirements on the damping. This study focuses on the development of a laboratory test rig with a host structure and a vibration absorber with tunable damping via an active relative velocity feedback. A voice coil actuator is used for this purpose. To overcome the passive damping effects of the back electromagnetic force a novel voltage feedback control is proposed, which has been validated both in simulation and experimentally. The aim of this study is to have a test rig ready for the introduction of piezo-transducers and available for future experimental evaluations of the damping effect on the effectiveness of vibration reduction and energy harvesting efficiency.

  18. Detection of the Vibration Signal from Human Vocal Folds Using a 94-GHz Millimeter-Wave Radar

    Directory of Open Access Journals (Sweden)

    Fuming Chen

    2017-03-01

    Full Text Available The detection of the vibration signal from human vocal folds provides essential information for studying human phonation and diagnosing voice disorders. Doppler radar technology has enabled the noncontact measurement of the human-vocal-fold vibration. However, existing systems must be placed in close proximity to the human throat and detailed information may be lost because of the low operating frequency. In this paper, a long-distance detection method, involving the use of a 94-GHz millimeter-wave radar sensor, is proposed for detecting the vibration signals from human vocal folds. An algorithm that combines empirical mode decomposition (EMD and the auto-correlation function (ACF method is proposed for detecting the signal. First, the EMD method is employed to suppress the noise of the radar-detected signal. Further, the ratio of the energy and entropy is used to detect voice activity in the radar-detected signal, following which, a short-time ACF is employed to extract the vibration signal of the human vocal folds from the processed signal. For validating the method and assessing the performance of the radar system, a vibration measurement sensor and microphone system are additionally employed for comparison. The experimental results obtained from the spectrograms, the vibration frequency of the vocal folds, and coherence analysis demonstrate that the proposed method can effectively detect the vibration of human vocal folds from a long detection distance.

  19. Detection of the Vibration Signal from Human Vocal Folds Using a 94-GHz Millimeter-Wave Radar.

    Science.gov (United States)

    Chen, Fuming; Li, Sheng; Zhang, Yang; Wang, Jianqi

    2017-03-08

    The detection of the vibration signal from human vocal folds provides essential information for studying human phonation and diagnosing voice disorders. Doppler radar technology has enabled the noncontact measurement of the human-vocal-fold vibration. However, existing systems must be placed in close proximity to the human throat and detailed information may be lost because of the low operating frequency. In this paper, a long-distance detection method, involving the use of a 94-GHz millimeter-wave radar sensor, is proposed for detecting the vibration signals from human vocal folds. An algorithm that combines empirical mode decomposition (EMD) and the auto-correlation function (ACF) method is proposed for detecting the signal. First, the EMD method is employed to suppress the noise of the radar-detected signal. Further, the ratio of the energy and entropy is used to detect voice activity in the radar-detected signal, following which, a short-time ACF is employed to extract the vibration signal of the human vocal folds from the processed signal. For validating the method and assessing the performance of the radar system, a vibration measurement sensor and microphone system are additionally employed for comparison. The experimental results obtained from the spectrograms, the vibration frequency of the vocal folds, and coherence analysis demonstrate that the proposed method can effectively detect the vibration of human vocal folds from a long detection distance.

  20. Vibration-Induced Motor Responses of Infants With and Without Myelomeningocele

    Science.gov (United States)

    Teulier, Caroline; Smith, Beth A.; Kim, Byungji; Beutler, Benjamin D.; Martin, Bernard J.; Ulrich, Beverly D.

    2012-01-01

    Background The severity of myelomeningocele (MMC) stems both from a loss of neurons due to neural tube defect and a loss of function in viable neurons due to reduced movement experience during the first year after birth. In young infants with MMC, the challenge is to reinforce excitability and voluntary control of all available neurons. Muscle vibration paired with voluntary movement may increase motoneuron excitability and contribute to improvements in neural organization, responsiveness, and control. Objectives This study examined whether infants with or without MMC respond to vibration by altering their step or stance behavior when supported upright on a treadmill. Design This was a cross-sectional study. Methods Twenty-four 2- to 10-month-old infants, 12 with typical development (TD) and 12 with MMC (lumbar and sacral lesions), were tested. Infants were supported upright with their feet in contact with a stationary or moving treadmill during 30-second trials. Rhythmic alternating vibrations were applied to the right and left rectus femoris muscles, the lateral gastrocnemius muscle, or the sole of the foot. Two cameras and behavior coding were used to determine step count, step type, and motor response to vibration onset. Results Step count decreased and swing duration increased in infants with TD during vibration of the sole of the foot on a moving treadmill (FT-M trials). Across all groups the percentage of single steps increased during vibration of the lateral gastrocnemius muscle on a moving treadmill. Infants with MMC and younger infants with TD responded to onset of vibration with leg straightening during rectus femoris muscle stimulation and by stepping during FT-M trials more often than older infants with TD. Conclusions Vibration seems a viable option for increasing motor responsiveness in infants with MMC. Follow-up studies are needed to identify optimal methods of administering vibration to maximize step and stance behavior in infants. PMID:22228610

  1. Dynamics modelling and Hybrid Suppression Control of space robots performing cooperative object manipulation

    Science.gov (United States)

    Zarafshan, P.; Moosavian, S. Ali A.

    2013-10-01

    Dynamics modelling and control of multi-body space robotic systems composed of rigid and flexible elements is elaborated here. Control of such systems is highly complicated due to severe under-actuated condition caused by flexible elements, and an inherent uneven nonlinear dynamics. Therefore, developing a compact dynamics model with the requirement of limited computations is extremely useful for controller design, also to develop simulation studies in support of design improvement, and finally for practical implementations. In this paper, the Rigid-Flexible Interactive dynamics Modelling (RFIM) approach is introduced as a combination of Lagrange and Newton-Euler methods, in which the motion equations of rigid and flexible members are separately developed in an explicit closed form. These equations are then assembled and solved simultaneously at each time step by considering the mutual interaction and constraint forces. The proposed approach yields a compact model rather than common accumulation approach that leads to a massive set of equations in which the dynamics of flexible elements is united with the dynamics equations of rigid members. To reveal such merits of this new approach, a Hybrid Suppression Control (HSC) for a cooperative object manipulation task will be proposed, and applied to usual space systems. A Wheeled Mobile Robotic (WMR) system with flexible appendages as a typical space rover is considered which contains a rigid main body equipped with two manipulating arms and two flexible solar panels, and next a Space Free Flying Robotic system (SFFR) with flexible members is studied. Modelling verification of these complicated systems is vigorously performed using ANSYS and ADAMS programs, while the limited computations of RFIM approach provides an efficient tool for the proposed controller design. Furthermore, it will be shown that the vibrations of the flexible solar panels results in disturbing forces on the base which may produce undesirable errors

  2. An Alternative to Thought Suppression?

    Science.gov (United States)

    Boice, Robert

    2012-01-01

    Comments on the original article, "Setting free the bears: Escape from thought suppression," by D. M. Wegner (see record 2011-25622-008). While Wegner supposed that we might have to learn to live with bad thoughts, the present author discusses the use of imagination and guided imagery as an alternative to forced thought suppression.

  3. Managing for soil health can suppress pests

    Directory of Open Access Journals (Sweden)

    Amanda Hodson

    2016-08-01

    Full Text Available A “healthy” soil can be thought of as one that functions well, both agronomically and ecologically, and one in which soil biodiversity and crop management work in synergy to suppress pests and diseases. UC researchers have pioneered many ways of managing soil biology for pest management, including strategies such as soil solarization, steam treatment and anaerobic soil disinfestation, as well as improvements on traditional methods, such as reducing tillage, amending soil with organic materials, and cover cropping. As managing for soil health becomes more of an explicit focus due to restrictions on the use of soil fumigants, integrated soil health tests will be needed that are validated for use in California. Other research needs include breeding crops for disease resistance and pest suppressive microbial communities as well as knowledge of how beneficial organisms influence plant health.

  4. Suppression of intrinsic roughness in encapsulated graphene

    Science.gov (United States)

    Thomsen, Joachim Dahl; Gunst, Tue; Gregersen, Søren Schou; Gammelgaard, Lene; Jessen, Bjarke Sørensen; Mackenzie, David M. A.; Watanabe, Kenji; Taniguchi, Takashi; Bøggild, Peter; Booth, Timothy J.

    2017-07-01

    Roughness in graphene is known to contribute to scattering effects which lower carrier mobility. Encapsulating graphene in hexagonal boron nitride (hBN) leads to a significant reduction in roughness and has become the de facto standard method for producing high-quality graphene devices. We have fabricated graphene samples encapsulated by hBN that are suspended over apertures in a substrate and used noncontact electron diffraction measurements in a transmission electron microscope to measure the roughness of encapsulated graphene inside such structures. We furthermore compare the roughness of these samples to suspended bare graphene and suspended graphene on hBN. The suspended heterostructures display a root mean square (rms) roughness down to 12 pm, considerably less than that previously reported for both suspended graphene and graphene on any substrate and identical within experimental error to the rms vibrational amplitudes of carbon atoms in bulk graphite. Our first-principles calculations of the phonon bands in graphene/hBN heterostructures show that the flexural acoustic phonon mode is localized predominantly in the hBN layer. Consequently, the flexural displacement of the atoms in the graphene layer is strongly suppressed when it is supported by hBN, and this effect increases when graphene is fully encapsulated.

  5. VIBRATION CONTROL OF RECTANGULAR CROSS-PLY FRP PLATES USING PZT MATERIALS

    Directory of Open Access Journals (Sweden)

    DILEEP KUMAR K

    2017-12-01

    Full Text Available Piezoelectric materials are extensively employed in the field of structures for condition monitoring, smart control and testing applications. The piezoelectric patches are surface bonded to a composite laminate plate and used as vibration actuators. The coupling effects between the mechanical and electric properties of piezoelectric materials have drawn significant attention for their potential applications. In the present work, an analytical solution of the vibration response of a simply supported laminate rectangular plate under time harmonic electrical loading is obtained and a concept is developed for an approximate dynamic model to the vibration response of the simply supported orthotropic rectangular plates excited by a piezoelectric patch of variable rectangular geometry and location. A time harmonic electric voltages with the same magnitude and opposite sign are applied to the two symmetric piezoelectric actuators, which results in the bending moment on the plate. The main objective of the work is to obtain an analytical solution for the vibration amplitude of composite plate predicted from plate theory. The results demonstrate that the vibration modes can be selectively excited and the geometry of the PZTactuator shape remarkably affects the distribution of the response among modes. Thus according to the desired degree shape control it is possible to tailor the shape, size and properly designed control algorithm of the actuator to either excite or suppress particular modes.

  6. Vibration-type particle separation device with piezoceramic vibrator

    Science.gov (United States)

    Ooe, Katsutoshi; Doi, Akihiro

    2008-12-01

    During hemanalysis, it is necessary to separate blood cells from whole blood. Many blood separation methods, for example, centrifugation and filtering, are in practical use. However, the use of these methods involves problems from the perspectives of processing speed and processing volume. We develop new types of blood separation devices that use piezo-ceramic vibrators. The first device uses a capillary. One end of the capillary is fixed to the device frame, and the other is fixed to a piezo-ceramic vibrator. The vibrator transmits bending waves to the capillary. This device can process only a small amount of solution; therefore, it is not suitable for hemanalysis. In order to solve this problem, we developed a second device; this device has a pair of thin glass plates with a small gap as a substitute for the capillary used in the first device. These devices are based on the fact that particles heavier than water move toward transverse velocity antinodes while those lighter than water move toward velocity nodes. In this report, we demonstrate the highspeed separation of silica microbeads and 50-vol% glycerol water by using these devices. The first device can separate the abovementioned solution within 3 min while the second can separate it within 1 min. Both devices are driven by a rectangular wave of 15 to 20 Vpp. Furthermore, it has been confirmed that red blood cells are separated from diluted whole blood using the first device within approximately 1 min. These devices have transparency, so they can compose as the analysis system with the chemical analyzer easily.

  7. Photoperiodic suppression of drug reinstatement.

    Science.gov (United States)

    Sorg, B A; Stark, G; Sergeeva, A; Jansen, H T

    2011-03-10

    The rewarding influence of drugs of abuse varies with time of day and appears to involve interactions between the circadian and the mesocorticolimbic dopamine systems. The circadian system is also intimately involved in measuring daylength. Thus, the present study examined the impact of changing daylength (photoperiod) on cocaine-seeking behaviors. Male Sprague-Dawley rats were trained and tested on a 12L:12D light:dark schedule for cocaine-induced reinstatement of conditioned place preference (CPP) at three times of day (Zeitgeber time (ZT): 4, 12, and 20) to determine a preference score. Rats were then shifted to either shorter (6L:18D) or longer (18L:6D) photoperiods and then to constant conditions, re-tested for cocaine-induced reinstatement under each different condition, and then returned to their original photoperiod (12L:12D) and tested once more. Rats exhibited a circadian profile of preference score in constant darkness with a peak at 12 h after lights-off. At both ZT4 and ZT20, but not at ZT12, shorter photoperiods profoundly suppressed cocaine reinstatement, which did not recover even after switching back to 12L:12D. In contrast, longer photoperiods did not alter reinstatement. Separate studies showed that the suppression of cocaine reinstatement was not due to repeated testing. In an additional experiment, we examined the photoperiodic regulation of tyrosine hydroxylase (TH) and dopamine transporter (DAT) proteins in drug-naive rats. These results revealed photoperiodic modulation of proteins in the prefrontal cortex and dorsal striatum, but not in the nucleus accumbens or ventral tegmental area. Together, these findings add further support to the circadian genesis of cocaine-seeking behaviors and demonstrate that drug-induced reinstatement is modulated by photoperiod. Furthermore, the results suggest that photoperiod partly contributes to the seasonal expression of certain drug-related behaviors in humans living at different latitudes and thus our

  8. Actively controlled vibration welding system and method

    Science.gov (United States)

    Cai, Wayne W.; Kang, Bongsu; Tan, Chin-An

    2013-04-02

    A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

  9. Vibration Mitigation without Dissipative Devices: First Large-Scale Testing of a State Switched Inducer

    Directory of Open Access Journals (Sweden)

    Daniel Tirelli

    2014-01-01

    Full Text Available A new passive device for mitigating cable vibrations is proposed and its efficiency is assessed on 45-meter long taut cables through a series of free and forced vibration tests. It consists of a unilateral spring attached perpendicularly to the cable near the anchorage. Because of its ability to change the cable dynamic behaviour through intermittent activation, the device has been called state switched inducer (SSI. The cable behaviour is shown to be deeply modified by the SSI: the forced vibration response is anharmonicc and substantially reduced in amplitude whereas the free vibration decay is largely sped up through a beating phenomenon. The vibration mitigation effect is mainly due to the activation and coupling of various vibration modes, as evidenced in the response spectra of the equipped cable. This first large-scale experimental campaign shows that the SSI outperforms classical passive devices, thus paving the way to a new kind of low-cost vibration mitigation systems which do not rely on dissipation.

  10. Impact of the vibrations on the environment caused by passages of trains at variable speed

    Directory of Open Access Journals (Sweden)

    Kożuch Barbara

    2016-01-01

    Full Text Available The paper deals with negative environmental impact caused by the passages of different kinds of trains at variable speed. The study is based on the measurement results which took place in Poland in 2013 on the railway line no. 4. The effect of the traction unit – Pendolino (EMU 250 on the vibration climate was analysed. The impact of passages of new trains was compared to currently operated rolling stock. The speed of trains was varying between 40 and 250 km/h. Vibration measurements were conducted by stuff of an accredited Laboratory of Structural Mechanics at Cracow University of Technology (Accreditation No. AB 826. The influence of the indicated vibrations due to passages of the trains on the building in the neighbourhood of the line was investigated. The vibration assessment was done for horizontal components of vibrations according to Polish standard code. Assessment of environmental impact was presented by indicator of perceptibility of vibration through construction (WODB, which refers to the Scales of Dynamic Influences (SDI scales. The limits specified by standards in any of the passages have not been exceeded. The change of speed or rolling stock resulted in a change in the characteristic of the vibration spectrum.

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

    Directory of Open Access Journals (Sweden)

    Wang Chunju

    2015-01-01

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

  12. Ring Laser Gyro G-Sensitive Misalignment Calibration in Linear Vibration Environments.

    Science.gov (United States)

    Wang, Lin; Wu, Wenqi; Li, Geng; Pan, Xianfei; Yu, Ruihang

    2018-02-16

    The ring laser gyro (RLG) dither axis will bend and exhibit errors due to the specific forces acting on the instrument, which are known as g-sensitive misalignments of the gyros. The g-sensitive misalignments of the RLG triad will cause severe attitude error in vibration or maneuver environments where large-amplitude specific forces and angular rates coexist. However, g-sensitive misalignments are usually ignored when calibrating the strapdown inertial navigation system (SINS). This paper proposes a novel method to calibrate the g-sensitive misalignments of an RLG triad in linear vibration environments. With the SINS is attached to a linear vibration bench through outer rubber dampers, rocking of the SINS can occur when the linear vibration is performed on the SINS. Therefore, linear vibration environments can be created to simulate the harsh environment during aircraft flight. By analyzing the mathematical model of g-sensitive misalignments, the relationship between attitude errors and specific forces as well as angular rates is established, whereby a calibration scheme with approximately optimal observations is designed. Vibration experiments are conducted to calibrate g-sensitive misalignments of the RLG triad. Vibration tests also show that SINS velocity error decreases significantly after g-sensitive misalignments compensation.

  13. [Low back pain among farmers exposed to whole body vibration: a literature review].

    Science.gov (United States)

    Solecki, Leszek

    2011-01-01

    A literature review was performed for the years 1990-2007. It covered reports addressing the problems associated with the prevalence of low back pain and musculoskeletal disorders among farmers. In addition, the anticipated relationship between low back pain and whole body vibration in farmers was evaluated based on 12 reports for the years 1987-2009. The review confirmed that the prevalence of back pain is significantly higher in farmers exposed to whole body vibration than in the control group (not exposed to vibration). The frequency of back pain is related with whole body vibration, as well as with prolonged sitting position, wrong body posture and physical work load (especially lifting and carrying loads). The prevalence of these symptoms increases with the increased vibration dose and duration of exposure. Disorders in the lower section of the spine were associated with age, accidents (concerning the back), cumulative dose of whole body vibration, and overload due to wrong body posture. Long-term exposure affecting the whole body is harmful to the skeletal system (degeneration of the spine). The results of the study suggest that the repeated or constant exposure to mechanical shocks may increase the risk of low back pain. The investigations confirmed that there is a dose-response type of relationship between exposure to whole body vibration and pain in the lumbar section of the spine.

  14. Vibrational and orientational dynamics of water in aqueous hydroxide solutions.

    Science.gov (United States)

    Hunger, Johannes; Liu, Liyuan; Tielrooij, Klaas-Jan; Bonn, Mischa; Bakker, Huib

    2011-09-28

    We report the vibrational and orientational dynamics of water molecules in isotopically diluted NaOH and NaOD solutions using polarization-resolved femtosecond vibrational spectroscopy and terahertz time-domain dielectric relaxation measurements. We observe a speed-up of the vibrational relaxation of the O-D stretching vibration of HDO molecules outside the first hydration shell of OH(-) from 1.7 ± 0.2 ps for neat water to 1.0 ± 0.2 ps for a solution of 5 M NaOH in HDO:H(2)O. For the O-H vibration of HDO molecules outside the first hydration shell of OD(-), we observe a similar speed-up from 750 ± 50 fs to 600 ± 50 fs for a solution of 6 M NaOD in HDO:D(2)O. The acceleration of the decay is assigned to fluctuations in the energy levels of the HDO molecules due to charge transfer events and charge fluctuations. The reorientation dynamics of water molecules outside the first hydration shell are observed to show the same time constant of 2.5 ± 0.2 ps as in bulk liquid water, indicating that there is no long range effect of the hydroxide ion on the hydrogen-bond structure of liquid water. The terahertz dielectric relaxation experiments show that the transfer of the hydroxide ion through liquid water involves the simultaneous motion of ~7 surrounding water molecules, considerably less than previously reported for the proton. © 2011 American Institute of Physics

  15. Theory And Working Of Noise And Vibration

    International Nuclear Information System (INIS)

    Jeong, Il Rok

    1988-09-01

    This book deals with theory of noise including physical property of noise like term and characteristic of sound, occurrence of sound, characteristic of noise pollution and main cause of occurrence of noise, technique of prevention of noise with noise reduction, construction guide for prevention of noise, and measure of interior noise. It also has the theory of vibration such as an introduction of vibration, and technology of prevention of vibration, official test method of environmental pollution, and summary of protection of the environment.

  16. Quantification of mouse in vivo whole-body vibration amplitude from motion-blur using x-ray imaging

    International Nuclear Information System (INIS)

    Hu, Zhengyi; Yuan, Xunhua; Pollmann, Steven I; Nikolov, Hristo N; Holdsworth, David W; Welch, Ian

    2015-01-01

    Musculoskeletal effects of whole-body vibration on animals and humans have become an intensely studied topic recently, due to the potential of applying this method as a non-pharmacological therapy for strengthening bones. It is relatively easy to quantify the transmission of whole-body mechanical vibration through the human skeletal system using accelerometers. However, this is not the case for small-animal pre-clinical studies because currently available accelerometers have a large mass, relative to the mass of the animals, which causes the accelerometers themselves to affect the way vibration is transmitted. Additionally, live animals do not typically remain motionless for long periods, unless they are anesthetized, and they are required to maintain a static standing posture during these studies. These challenges provide the motivation for the development of a method to quantify vibrational transmission in small animals. We present a novel imaging technique to quantify whole-body vibration transmission in small animals using 280 μm diameter tungsten carbide beads implanted into the hind limbs of mice. Employing time-exposure digital x-ray imaging, vibrational amplitude is quantified based on the blurring of the implanted beads caused by the vibrational motion. Our in vivo results have shown this technique is capable of measuring vibration amplitudes as small as 0.1 mm, with precision as small as  ±10 μm, allowing us to distinguish differences in the transmitted vibration at different locations on the hindlimbs of mice. (paper)

  17. Quantification of mouse in vivo whole-body vibration amplitude from motion-blur using x-ray imaging

    Science.gov (United States)

    Hu, Zhengyi; Welch, Ian; Yuan, Xunhua; Pollmann, Steven I.; Nikolov, Hristo N.; Holdsworth, David W.

    2015-08-01

    Musculoskeletal effects of whole-body vibration on animals and humans have become an intensely studied topic recently, due to the potential of applying this method as a non-pharmacological therapy for strengthening bones. It is relatively easy to quantify the transmission of whole-body mechanical vibration through the human skeletal system using accelerometers. However, this is not the case for small-animal pre-clinical studies because currently available accelerometers have a large mass, relative to the mass of the animals, which causes the accelerometers themselves to affect the way vibration is transmitted. Additionally, live animals do not typically remain motionless for long periods, unless they are anesthetized, and they are required to maintain a static standing posture during these studies. These challenges provide the motivation for the development of a method to quantify vibrational transmission in small animals. We present a novel imaging technique to quantify whole-body vibration transmission in small animals using 280 μm diameter tungsten carbide beads implanted into the hind limbs of mice. Employing time-exposure digital x-ray imaging, vibrational amplitude is quantified based on the blurring of the implanted beads caused by the vibrational motion. Our in vivo results have shown this technique is capable of measuring vibration amplitudes as small as 0.1 mm, with precision as small as  ±10 μm, allowing us to distinguish differences in the transmitted vibration at different locations on the hindlimbs of mice.

  18. High force vibration testing with wide frequency range

    Science.gov (United States)

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

    2013-04-02

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

  19. Axisymmetric vibrations of thick shells of revolution

    International Nuclear Information System (INIS)

    Suzuki, Katsuyoshi; Kosawada, Tadashi; Takahashi, Shin

    1983-01-01

    Axisymmetric shells of revolution are used for chemical plants, nuclear power plants, aircrafts, structures and so on, and the elucidation of their free vibration is important for the design. In this study, the axisymmetric vibration of a barrel-shaped shell was analyzed by the modified thick shell theory. The Lagrangian during one period of the vibration of a shell of revolution was determined, and from its stopping condition, the vibration equations and the boundary conditions were derived. The vibration equations were analyzed strictly by using the series solution. Moreover, the basic equations for the strain of a shell and others were based on those of Love. As the examples of numerical calculation, the natural frequency and vibration mode of the symmetrical shells of revolution fixed at both ends and supported at both ends were determined, and their characteristics were clarified. By comparing the results of this study with the results by thin shell theory, the effects of shearing deformation and rotary inertia on the natural frequency and vibration mode were clarified. The theoretical analysis and the numerical calculation are described. The effects of shearing deformation and rotary inertia on the natural frequency became larger in the higher order vibration. The vibration mode did not much change in both theories. (Kako, I.)

  20. Developed vibration waveform monitoring unit for CBM

    International Nuclear Information System (INIS)

    Hamada, T.; Hotsuta, K.; Hirose, I.; Morita, E.

    2007-01-01

    In nuclear power plants, many rotating machines such as pumps and fans are in use. Shikoku Research Institute Inc. has recently developed easy-to-use tools to facilitate the maintenance of such equipment. They include a battery-operated vibration waveform monitoring unit which allows unmanned vibration monitoring on a regular basis and data collection even from intermittently operating equipment, a waveform data collector which can be used for easy collection, storage, control, and analysis of raw vibration waveform data during normal operation, and vibration analysis and evaluation tools. A combination of these tools has a high potential for optimization of rotating equipment maintenance. (author)

  1. Vibrational dynamics of crystalline L-alanine

    Energy Technology Data Exchange (ETDEWEB)

    Bordallo, H.N.; Eckert, J. [Los Alamos National Lab., NM (United States); Barthes, M. [Univ. Montpellier II (France)

    1997-11-01

    The authors report a new, complete vibrational analysis of L-alanine and L-alanine-d{sub 4} which utilizes IINS intensities in addition to frequency information. The use of both isotopomers resulted in a self-consistent force field for and assignment of the molecular vibrations in L-alanine. Some details of the calculation as well as a comparison of calculated and observed IINS spectra are presented. The study clarifies a number of important issues on the vibrational dynamics of this molecule and presents a self-consistent force field for the molecular vibrations in crystalline L-alanine.

  2. Surface Acoustic Wave (SAW Vibration Sensors

    Directory of Open Access Journals (Sweden)

    Jerzy Filipiak

    2011-12-01

    Full Text Available In the paper a feasibility study on the use of surface acoustic wave (SAW vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit.

  3. Electromagnetic Vibration Energy Harvesting for Railway Applications

    Directory of Open Access Journals (Sweden)

    Bradai S.

    2018-01-01

    Full Text Available Safe localization of trains via GPS and wireless sensors is essential for railway traffic supervision. Especially for freight trains and because normally no power source is available on the wagons, special solutions for energy supply have to be developed based on energy harvesting techniques. Since vibration is available in this case, it provides an interesting source of energy. Nevertheless, in order to have an efficient design of the harvesting system, the existing vibration needs to be investigated. In this paper, we focus on the characterization of vibration parameters in railway application. We propose an electromagnetic vibration converter especially developed to this application. Vibration profiles from a train traveling between two German cities were measured using a data acquisition system installed on the train’s wagon. Results show that the measured profiles present multiple frequency signals in the range of 10 to 50 Hz and an acceleration of up to 2 g. A prototype for a vibration converter is designed taking into account the real vibration parameters, robustness and integrability requirements. It is based on a moving coil attached to a mechanical spring. For the experimental emulation of the train vibrations, a shaker is used as an external artificial vibration source controlled by a laser sensor in feedback. A maximum voltage of 1.7 V peak to peak which corresponds to a maximum of 10 mW output power where the applied excitation frequency is close to the resonant frequency of the converter which corresponds to 27 Hz.

  4. A multi-reference filtered-x-Newton narrowband algorithm for active isolation of vibration and experimental investigations

    Science.gov (United States)

    Wang, Chun-yu; He, Lin; Li, Yan; Shuai, Chang-geng

    2018-01-01

    In engineering applications, ship machinery vibration may be induced by multiple rotational machines sharing a common vibration isolation platform and operating at the same time, and multiple sinusoidal components may be excited. These components may be located at frequencies with large differences or at very close frequencies. A multi-reference filtered-x Newton narrowband (MRFx-Newton) algorithm is proposed to control these multiple sinusoidal components in an MIMO (multiple input and multiple output) system, especially for those located at very close frequencies. The proposed MRFx-Newton algorithm can decouple and suppress multiple sinusoidal components located in the same narrow frequency band even though such components cannot be separated from each other by a narrowband-pass filter. Like the Fx-Newton algorithm, good real-time performance is also achieved by the faster convergence speed brought by the 2nd-order inverse secondary-path filter in the time domain. Experiments are also conducted to verify the feasibility and test the performance of the proposed algorithm installed in an active-passive vibration isolation system in suppressing the vibration excited by an artificial source and air compressor/s. The results show that the proposed algorithm not only has comparable convergence rate as the Fx-Newton algorithm but also has better real-time performance and robustness than the Fx-Newton algorithm in active control of the vibration induced by multiple sound sources/rotational machines working on a shared platform.

  5. Control of vortex-induced non-resonance vibration using piezo-ceramic actuators embedded in a structure

    Science.gov (United States)

    Zhang, M. M.; Cheng, L.; Zhou, Y.

    2005-12-01

    Closed-loop control of vortex-induced non-resonant vibration of a flexible square cylinder is experimentally investigated in this paper. Piezo-ceramic actuators were embedded inside the cylinder to cause an oscillation of the cylinder surface, which subsequently altered the fluid-structure interaction. Experiments were conducted in a wind tunnel at Reynolds numbers, Re, of 2800 and 8000. Two typical control schemes, i.e. Y_control and u+Y_control, were deployed using feedback signals from structural vibration Y and combined Y and fluctuating flow velocity u, respectively. The control effects on the structural vibration and flow were assessed using a laser vibrometer, an optical fiber Bragg grating sensor, hot wires and particle image velocimetry. Experimental results show that both vortex shedding from the cylinder and the vortex-induced non-resonant vibration were effectively suppressed. The best control effects were observed with u+Y_control in use; the root mean square values of Y, the structural strain rate ɛy along the lift direction and u, i.e. Yrms, ɛy,rms and urms, and the circulation Γ dropped at Re = 8000 by 58%, 52%, 53% and 88%, respectively, compared with the unperturbed case. It was found that the control effectively modified the nature of the fluid-structure interaction by changing the in-phase fluid-structure synchronization at all dominant frequencies into anti-phase interaction, accounting for the suppression in both vortex shedding and structural vibration.

  6. Vibration fatigue using modal decomposition

    Science.gov (United States)

    Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha

    2018-01-01

    Vibration-fatigue analysis deals with the material fatigue of flexible structures operating close to natural frequencies. Based on the uniaxial stress response, calculated in the frequency domain, the high-cycle fatigue model using the S-N curve material data and the Palmgren-Miner hypothesis of damage accumulation is applied. The multiaxial criterion is used to obtain the equivalent uniaxial stress response followed by the spectral moment approach to the cycle-amplitude probability density estimation. The vibration-fatigue analysis relates the fatigue analysis in the frequency domain to the structural dynamics. However, once the stress response within a node is obtained, the physical model of the structure dictating that response is discarded and does not propagate through the fatigue-analysis procedure. The structural model can be used to evaluate how specific dynamic properties (e.g., damping, modal shapes) affect the damage intensity. A new approach based on modal decomposition is presented in this research that directly links the fatigue-damage intensity with the dynamic properties of the system. It thus offers a valuable insight into how different modes of vibration contribute to the total damage to the material. A numerical study was performed showing good agreement between results obtained using the newly presented approach with those obtained using the classical method, especially with regards to the distribution of damage intensity and critical point location. The presented approach also offers orders of magnitude faster calculation in comparison with the conventional procedure. Furthermore, it can be applied in a straightforward way to strain experimental modal analysis results, taking advantage of experimentally measured strains.

  7. Modelling and experimental validation of two-dimensional transverse vibrations in a flexible robot link

    DEFF Research Database (Denmark)

    Sørensen, Paul Haase; Baungaard, Jens Rane

    1996-01-01

    A general model for a rotating homogenous flexible robot link is developed. The model describes two-dimensional transverse vibrations induced by the actuator due to misalignment of the actuator axis of rotation relative to the link symmetry axis and due to translational acceleration of the link...

  8. Vibrational spectroscopy of Cm–C/Cb–Cb stretching vibrations of ...

    Indian Academy of Sciences (India)

    operator which conveniently describes stretching vibrations of biomolecules. For a copper tetramesityl porphyrin molecule, the higher excited vibrational levels are calculated by applying the U(2) algebraic approach. Keywords. Lie algebraic techniques; vibrational spectra; copper tetramesityl porphyrin. PACS Nos 31.65.

  9. EMBEDDED SYSTEMS FOR VIBRATION MONITORING

    Directory of Open Access Journals (Sweden)

    Miloš Milovančević

    2014-08-01

    Full Text Available The purpose of the research presented in this paper is the development of the optimal micro configuration for vibration monitoring of pumping aggregate, based on Microchip’s microcontroller (MC. Hardware used is 10-bit MC, upgraded with 12/bit A/D converter. Software for acquisition and data analysis is optimized for testing turbo pumps with rotation speed up to 2000 rpm. This software limitation is set for automatic diagnostics and for individual and manual vibro-diagnostic; the only limitation is set by accelerometer performance. The authors have performed numerous measurements on a wide range of turbo aggregates for establishing the operational condition of pumping aggregates.

  10. Vibration diagnostics instrumentation for ILC

    Energy Technology Data Exchange (ETDEWEB)

    Bertolini, A.

    2007-06-15

    The future e{sup -}e{sup +} 500 GeV International Linear Collider will rely on unprecedented nanometer scale particle beam size at the interaction point, in order to achieve the design luminosity. Tight tolerances on static and dynamic alignment of the accelerator cavities and optical components are demanded to transport and focus the high energy electron and positron beams with reasonable position jitter and low emittance. A brief review of techniques and devices evaluated and developed so far for the vibration diagnostics of the machine is presented in this paper. (orig.)

  11. Vibration diagnostics instrumentation for ILC

    International Nuclear Information System (INIS)

    Bertolini, A.

    2007-06-01

    The future e - e + 500 GeV International Linear Collider will rely on unprecedented nanometer scale particle beam size at the interaction point, in order to achieve the design luminosity. Tight tolerances on static and dynamic alignment of the accelerator cavities and optical components are demanded to transport and focus the high energy electron and positron beams with reasonable position jitter and low emittance. A brief review of techniques and devices evaluated and developed so far for the vibration diagnostics of the machine is presented in this paper. (orig.)

  12. Vibrational Spectroscopy of Chromatographic Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Jeanne E. Pemberton

    2011-03-10

    Chromatographic separations play a central role in DOE-supported fundamental research related to energy, biological systems, the environment, and nuclear science. The overall portfolio of research activities in the Separations and Analysis Program within the DOE Office of Basic Energy Sciences includes support for activities designed to develop a molecular-level understanding of the chemical processes that underlie separations for both large-scale and analytical-scale purposes. The research effort funded by this grant award was a continuation of DOE-supported research to develop vibrational spectroscopic methods to characterize the interfacial details of separations processes at a molecular level.

  13. Monothiodibenzoylmethane: Structural and vibrational assignments

    DEFF Research Database (Denmark)

    Hansen, Bjarke Knud Vilster; Gorski, Alexander; Posokhov, Yevgen

    2007-01-01

    The vibrational structure of the title compound (1,3-diphenyl-3-thioxopropane-1-one, TDBM) was studied by a variety of experimental and theoretical methods. The stable ground state configuration of TDBM was investigated by IR absorption measurements in different media, by LD polarization spectros...... to an “open”, non-chelated enethiol form (t-TCC), thereby supporting the previous conclusions by Posokhov et al. No obvious indications of the contribution of other forms to the observed spectra could be found....

  14. Introduction to vibrations and waves

    CERN Document Server

    Pain, H John

    2015-01-01

    Based on the successful multi-edition book "The Physics ofVibrations and Waves" by John Pain, the authors carry overthe simplicity and logic of the approach taken in the originalfirst edition with its focus on the patterns underlying andconnecting so many aspects of physical behavior, whilst bringingthe subject up-to-date so it is relevant to teaching in the21st century.The transmission of energy by wave propagation is a key conceptthat has applications in almost every branch of physics withtransmitting mediums essentially acting as a continuum of coupledoscillators. The characterization of t

  15. Vibration and Dynamic Response Control of Nonuniform Composite Rotating Blades

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available This paper addresses the free vibration, dynamic response, and the active control of composite rotating pretwisted blades modeled as nonuniform thin-walled beams, fixed at the hub at a setting angle, and incorporating piezoelectrically induced damping capabilities. In this sense, a distributed piezoelectric actuator system activated through the application of an out-of-phase electrical current is used to suppress the dynamic response of the rotating beam subjected to a Heaviside pulse. The blade model incorporates nonclassical effects such as transverse shear, secondary warping, and rotary inertias, and includes the centrifugal and Coriolis force fields. A velocity feedback control law relating the piezoelectrically induced bending moment at the beam tip with appropriately selected kinematical response quantities is used, and the beneficial effects of its implementation upon the closed loop eigenvibration and dynamic characteristics of the blade are highlighted.

  16. Simulation of Vibrations in Real Time Plane Milling with Spindle Speed Correction

    Directory of Open Access Journals (Sweden)

    I. I. Ivanov

    2017-01-01

    Full Text Available In milling the hard-to-machine materials vibrations (chatter often arise from the high cutting forces if a technological system is insufficiently rigid.The main way to suppress these vibrations is to increase a stiffness of the mounting system of the tool and the work-piece to be machined. However, sometimes this method doesn’t lead to desirable result because of high values of intrinsic pliability of the tool and the work-piece. Currently, there are more complicated methods to ensure milling process quality. Among them there are three main groups:mathematical simulation of milling process dynamics and computation of processing parameters which provide high quality of machined surface, low level of vibrations and static deflections of a tool and a work-piece;introduction of the active vibration suppression devices into machine tool design; such devices include a vibration sensor, a feedback circuit, and an actuator which induces kinematic or force action on the oscillatory system;control of processing parameters, mainly of rotation frequency for minimizing the amplitudes of vibrations.The paper studies one of the 3rd group methods. There is a suggestion to process a signal of vibrational accelerations in real time and detect a chatter onset. If the chatter has been detected its frequency is to be identified, and the new value of rotation speed is set:where Ω – rotation frequency, rot/s; p – the tool eigenfrequency value identified during processing, Hz; z – mill tooth number; i – positive integer number; ε<1 – small positive parameter. In the current research it is assumed that ε = 0,2.The formula has been chosen because at the rotation frequency axis where tooth pass frequency is slightly less than the eigenfrequency divided by the integer value there are stable zones of dynamics in the milling process.The study shows a developed model of the plane milling dynamics. It includes a dynamic model of the tool, a model of cutting

  17. Trajectory generation to suppress oscillations in under-constrained cable-driven parallel robots

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Sung Wook; Bak, Jeong Hyeon; Yoon, Jong Hyun; Park, Jong Hyeon [Dept. of Mechanical Engineering, Hanyang University, Seoul (Korea, Republic of); Park, Jong Oh [School of Mechanical Engineering, Chonnam National University, Gwangju (Korea, Republic of)

    2016-12-15

    Cable-driven parallel robots (CDPRs) have many advantages over conventional link-based robot manipulators in terms of acceleration due to their low inertia. This paper concerns about under-constrained CDPRs, which have a less number of cables than six, often used favorably due to their simpler structures. Since a smaller number of cables than 6 are employed, however, their payloads have extra degrees of motion freedom and exhibit swaying motions or oscillation. In this paper, a scheme to suppress unwanted oscillatory motions of the payload of a 4-cable-driven CDPR based on a Zero-vibration (ZV) input-shaping scheme is proposed. In this method, a motion in the 3-dimensional space is projected onto the independent motions on two vertical planes perpendicular to each other. On each of the vertical plane, the natural frequency of the CDPR is computed based on a 2-cable-driven planar CDPR model. The precise dynamic model of a planar CDPR is obtained in order to find the natural frequency, which depends on the payload position. The advantage of the proposed scheme is that it is possible to generate an oscillation-free trajectory based on a ZV input-shaping scheme despite the complexity in the dynamics of the CDPR and the difficulty in computing the natural frequencies of the CDPR, which is required in any ZV input-shaping scheme. To verify the effectiveness of the proposed method, a series of computer simulations and experiments were conducted for 3- dimensional motions with a 4-cable-driven CDPR. Their results showed that the motions of the CDPR with the proposed method exhibited a significant reduction in oscillations of the payload. However, when the payload moves near the edges of its workspace, the improvement in oscillation reduction diminished as expected due to the errors in model projection.

  18. Menstrual suppression in the adolescent.

    Science.gov (United States)

    Kantartzis, Kelly L; Sucato, Gina S

    2013-06-01

    Menstrual suppression, the use of contraceptive methods to eliminate or decrease the frequency of menses, is often prescribed for adolescents to treat menstrual disorders or to accommodate patient preference. For young women using hormonal contraceptives, there is no medical indication for menstruation to occur monthly, and various hormonal contraceptives can be used to decrease the frequency of menstruation with different side effect profiles and rates of amenorrhea. This article reviews the different modalities for menstrual suppression, common conditions in adolescents which may improve with menstrual suppression, and strategies for managing common side effects. Copyright © 2013 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

  19. Melt expulsion during ultrasonic vibration-assisted laser surface processing of austenitic stainless steel.

    Science.gov (United States)

    Alavi, S Habib; Harimkar, Sandip P

    2015-05-01

    Simultaneous application of ultrasonic vibrations during conventional materials processing (casting, welding) and material removal processes (machining) has recently been gaining widespread attention due to improvement in metallurgical quality and efficient material removal, respectively. In this paper, ultrasonic vibration-assisted laser surface melting of austenitic stainless steel (AISI 316) is reported. While the application of ultrasonic vibrations during laser processing delays the laser interaction with material due to enhancement of surface convection, it resulted in expulsion of melt from the irradiated region (forming craters) and transition from columnar to equiaxed dendritic grain structure in the resolidified melt films. Systematic investigations on the effect of ultrasonic vibrations (with vibrations frequency of 20 kHz and power output in the range of 20-40%) on the development of microstructure during laser surface melting (with laser power of 900 W and irradiation time in the range of 0.30-0.45 s) are reported. The results indicate that the proposed ultrasonic vibration-assisted laser processing can be designed for efficient material removal (laser machining) and improved equiaxed microstructure (laser surface modifications) during materials processing. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. A design of a two-phase permanent magnet vibration motor used for mobile phones

    Science.gov (United States)

    Chung, Shi-Uk; Hwang, Sang-Moon; Kim, Tae-Jong; Hwang, Gun-Yong; Kang, Beom-Soo

    2002-05-01

    With the advent of the telecommunications era, a mobile phone becomes a necessary communication device in modern society. However, a paging signal by a sound transducer often acts as an unpleasant noise, thus necessitating a paging signal by a vibration motor. The conventional flat type vibration motor uses three-phase windings with three phase coils. In this article, a new design of a vibration motor using a V connection with two phase coils is presented, increasing mass productivity. For electromagnetic field analysis, due to the motor symmetry, two-dimensional modeling can be implemented for fast computation, and performance is predicted by the finite element method. The winding distribution angle turns out to be the most important design parameter for the elimination of dead points, and a new coil configuration is suggested which has no adverse effect on motor size and weight. Experimental tests of vibration confirm the validity of the proposed design.