Sample records for vibration attenuation performance

  1. An experimental study of vibration attenuation performance of several on-grade slab configurations (United States)

    Amick, H.; Wongprasert, N.; Montgomery, J.; Haswell, P.; Lynch, D.


    There are several instances in the literature in which particular positions are taken regarding the nature of the floor supporting sensitive equipment such as advanced electron microscopes. Assertions are made that one methodology is better than another at reducing vibrations. However, very little experimental evidence has been provided to support those positions. This paper presents the results of an experimental in situ study of several slab configurations at a single location-the site of a nanotechnology facility that was about to be constructed at the University of Alberta. Three configurations were constructed: (a) a large solid slab of moderate thickness; (b) a smaller slab "island" of greater thickness (900 mm) surrounded by a thinner slab, both resting directly on soil and separated by a gap; and (c) another island of the same dimensions, but resting on four concrete piles. The three locations were instrumented and measurements taken allowing comparison of the performance of these configurations at attenuating ambient vibrations and vibrations due to a nearby heel-drop impulse. The ranking of the three must be based upon excitation type and frequency range of concern.

  2. Broadband Vibration Attenuation Using Hybrid Periodic Rods

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    S. Asiri


    Full Text Available This paper presents both theoretically and experimentally a new kind of a broadband vibration isolator. It is a table-like system formed by four parallel hybrid periodic rods connected between two plates. The rods consist of an assembly of periodic cells, each cell being composed of a short rod and piezoelectric inserts. By actively controlling the piezoelectric elements, it is shown that the periodic rods can efficiently attenuate the propagation of vibration from the upper plate to the lower one within critical frequency bands and consequently minimize the effects of transmission of undesirable vibration and sound radiation. In such a system, longitudinal waves can propagate from the vibration source in the upper plate to the lower one along the rods only within specific frequency bands called the "Pass Bands" and wave propagation is efficiently attenuated within other frequency bands called the "Stop Bands". The spectral width of these bands can be tuned according to the nature of the external excitation. The theory governing the operation of this class of vibration isolator is presented and their tunable filtering characteristics are demonstrated experimentally as functions of their design parameters. This concept can be employed in many applications to control the wave propagation and the force transmission of longitudinal vibrations both in the spectral and spatial domains in an attempt to stop/attenuate the propagation of undesirable disturbances.

  3. Attenuation of cryocooler induced vibration in spaceborne infrared payloads (United States)

    Veprik, A.; Twitto, A.


    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.

  4. Vibration Attenuation of Plate Using Multiple Vibration Absorbers

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    Zaman Izzuddin


    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.

  5. Attenuation of cryocooler induced vibration using multimodal tuned dynamic absorber (United States)

    Veprik, A.; Babitsky, V.; Tuito, A.


    Modern infrared imagers often rely on low Size, Weight and Power split Stirling linear cryocoolers comprised of side-by-side packed compressor and expander units fixedly mounted upon a common frame and interconnected by the configurable transfer line. Imbalanced reciprocation of moving assemblies generates vibration export in the form of tonal force couple producing angular and translational dynamic responses. Resulting line of sight jitter and dynamic defocusing may affect the image quality. The authors explore the concept of multimodal tuned dynamic absorber, the translational and tilting modal frequencies of which are essentially matched to the driving frequency. Dynamic analysis and full-scale testing show that the dynamic reactions (forces and moments) produced by such a device may effectively attenuate both translational and angular components of cryocooler-induced vibration.

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

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


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

  7. Performance evaluation on vibration control of MR landing gear

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    Lee, D Y; Nam, Y J; Park, M K [Graduate School, Pusan National University, Busan 609-735 (Korea, Republic of); Yamane, R [Kokushikan University, 4-28-1 Setagaya, Setagaya-ku, Tokyo 154-8515 (Japan)], E-mail:, E-mail:


    This paper is concerned with the applicability of the developed MR damper to the landing gear system for the attenuating undesired shock and vibration in the landing and taxing phases. First of all, the experimental model of the MR damper is derived based on the results of performance evaluations. Next, a simplified skyhook controller, which is one of the most straightforward, but effective approaches for improving ride comport in vehicles with active suspensions, is formulated. Then, the vibration control performances of the landing gear system using the MR damper are theoretically evaluated in the landing phase of the aircraft. A series of simulation analyses show that the proposed MR damper with the skyhook controller is effective for suppressing undesired vibration of the aircraft body. Finally, the effectiveness of the simulation results are additionally verified via HILS (Hardware-in-the-loop-simulation) method.

  8. A Novel E-DVA Module Synthesis Featuring of Synergy between Driving and Vibration Attenuation

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    Cheng Gu


    Full Text Available To attenuate the negative effects brought by heavy unsprung mass of the decentralized driving electric vehicle, a novel e-DVA module featuring of synergy between driving and vibration attenuation is proposed in this paper. It presents the advantages of compact structure and low cost. Structure design proves the feasibility of the e-DVA module. Kinematic analysis of the slider-crank mechanism is carried out to conclude the transmission ratio ripple under road excitation. After parameter matching and optimization of the e-DVA module based on the H2/H∞ norm criterions, vertical dynamics analyses in both frequency and time domains are conducted theoretically to prove the performance improvements on the ride comfort and handling stability under the constraint of DVA deflection bound.

  9. Tendon vibration attenuates superficial venous vessel response of the resting limb during static arm exercise. (United States)

    Ooue, Anna; Sato, Kohei; Hirasawa, Ai; Sadamoto, Tomoko


    The superficial vein of the resting limb constricts sympathetically during exercise. Central command is the one of the neural mechanisms that controls the cardiovascular response to exercise. However, it is not clear whether central command contributes to venous vessel response during exercise. Tendon vibration during static elbow flexion causes primary muscle spindle afferents, such that a lower central command is required to achieve a given force without altering muscle force. The purpose of this study was therefore to investigate whether a reduction in central command during static exercise with tendon vibration influences the superficial venous vessel response in the resting limb. Eleven subjects performed static elbow flexion at 35% of maximal voluntary contraction with (EX + VIB) and without (EX) vibration of the biceps brachii tendon. The heart rate, mean arterial pressure, and rating of perceived exertion (RPE) in overall and exercising muscle were measured. The cross-sectional area (CSAvein) and blood velocity of the basilic vein in the resting upper arm were assessed by ultrasound, and blood flow (BFvein) was calculated using both variables. Muscle tension during exercise was similar between EX and EX + VIB. However, RPEs at EX + VIB were lower than those at EX (P tension, showed that activation of central command was less during EX + VIB than during EX. Abolishment of the decrease in CSAvein during exercise at EX + VIB may thus have been caused by a lower level of central command at EX + VIB rather than EX. Diminished central command induced by tendon vibration may attenuate the superficial venous vessel response of the resting limb during sustained static arm exercise.

  10. Tendon vibration attenuates superficial venous vessel response of the resting limb during static arm exercise

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    Ooue Anna


    Full Text Available Abstract Background The superficial vein of the resting limb constricts sympathetically during exercise. Central command is the one of the neural mechanisms that controls the cardiovascular response to exercise. However, it is not clear whether central command contributes to venous vessel response during exercise. Tendon vibration during static elbow flexion causes primary muscle spindle afferents, such that a lower central command is required to achieve a given force without altering muscle force. The purpose of this study was therefore to investigate whether a reduction in central command during static exercise with tendon vibration influences the superficial venous vessel response in the resting limb. Methods Eleven subjects performed static elbow flexion at 35% of maximal voluntary contraction with (EX + VIB and without (EX vibration of the biceps brachii tendon. The heart rate, mean arterial pressure, and rating of perceived exertion (RPE in overall and exercising muscle were measured. The cross-sectional area (CSAvein and blood velocity of the basilic vein in the resting upper arm were assessed by ultrasound, and blood flow (BFvein was calculated using both variables. Results Muscle tension during exercise was similar between EX and EX + VIB. However, RPEs at EX + VIB were lower than those at EX (P P vein in the resting limb at EX decreased during exercise from baseline (P vein at EX + VIB did not change during exercise. CSAvein during exercise at EX was smaller than that at EX + VIB (P vein did not change during the protocol under either condition. The decreases in circulatory response and RPEs during EX + VIB, despite identical muscle tension, showed that activation of central command was less during EX + VIB than during EX. Abolishment of the decrease in CSAvein during exercise at EX + VIB may thus have been caused by a lower level of central command at EX + VIB rather than EX. Conclusion Diminished central command induced by tendon

  11. Vibration attenuation of a continuous rotor-blisk-journal bearing system employing smooth nonlinear energy sinks (United States)

    Bab, Saeed; Khadem, S. E.; Shahgholi, Majid; Abbasi, Amirhassan


    The current paper investigates the effects of a number of smooth nonlinear energy sinks (NESs) located on the disk and bearings on the vibration attenuation of a rotor-blisk-journal bearing system under excitation of a mass eccentricity force. The blade and rotor are modeled using the Euler-Bernoulli beam theory. The nonlinear energy sinks on the bearing have a linear damping and an essentially nonlinear stiffness. The nonlinear energy sinks on the disk have a linear damping, linear stiffness, and an essentially nonlinear stiffness. It can be seen that the linear stiffness of the NESs on the disk is eliminated by the negative stiffness induced by the centrifugal force, and the collection of the NESs can be tuned to a required rotational speed of the rotor by varying the linear stiffness of the NESs. Furthermore, the remained stiffness of the NESs on the disk after elimination of their linear stiffness, would be essentially a nonlinear (nonlinearizable) one. Two nonlinear energy sinks in the vertical axes are positioned on the bearing housing and nnd NESs are located on the perimeter of the disk. The equations of motion are extracted using the extended Hamilton principle. The modal coordinates and complex transformations are employed to decrease the number of equations of motion. A genetic algorithm is used to optimize the parameters of the nonlinear energy sinks and its objective function is considered as minimizing the vibration of the rotating system within an operating speed range. In order to examine the periodic and non-periodic solutions of the system, time history, bifurcation diagram, Poincaré map, phase portrait, Lyapunov exponent, and power spectra analyses are performed. System shows periodic and quasi-periodic motions for different values of the system parameters. It is shown that the NESs on the disk and bearings have almost local effects on vibration reduction of rotating system. In addition, the optimum NESs remove the instability region from the

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

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    Yushu Bian


    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.

  13. Vibration Attenuation by a Combination of a Piezoelectric Stack and a Permanent Magnet

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    A. Nandi


    Full Text Available The present work proposes a non-contact vibration attenuator made up of a permanent magnet mounted on a piezoelectric stack. Two such actuators are made to work simultaneously in a 'twin-actuator' configuration. It is conceived that a controlled change in the gap between the actuator and the structure is capable of attenuation of vibration of the structure. This appropriate change in gap is achieved by controlled motion of the piezoelectric stacks. It is shown that the actuator works as an active damper when the extension and contraction of the actuators are made proportional to the velocity of the beam. The resolution of extension of a piezoelectric stack is in the order of nanometers. Thus in the proposed actuator the force of actuation can be applied with great precision. This actuator is also attractive for its simple constructional feature.

  14. Methods of performing downhole operations using orbital vibrator energy sources (United States)

    Cole, Jack H.; Weinberg, David M.; Wilson, Dennis R.


    Methods of performing down hole operations in a wellbore. A vibrational source is positioned within a tubular member such that an annulus is formed between the vibrational source and an interior surface of the tubular member. A fluid medium, such as high bulk modulus drilling mud, is disposed within the annulus. The vibrational source forms a fluid coupling with the tubular member through the fluid medium to transfer vibrational energy to the tubular member. The vibrational energy may be used, for example, to free a stuck tubular, consolidate a cement slurry and/or detect voids within a cement slurry prior to the curing thereof.

  15. Vibration transfers to measure the performance of vibration isolated platforms on site using background noise excitation

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    Segerink, Franciscus B.; Korterik, Jeroen P.; Offerhaus, Herman L.


    This article demonstrates a quick and easy way of quantifying the performance of a vibration-isolated platform. We measure the vibration transfer from floor to table using background noise excitation from the floor. As no excitation device is needed, our setup only requires two identical sensors (in

  16. Impact energy attenuation performance of football headgear (United States)

    McIntosh, A.; McCrory, P.


    Objectives—Commercially available football head protectors were tested to determine their impact energy attenuation performance and ability to reduce the likelihood of concussion. Methods—Prospective study using standardised impact test methods with both rigid (magnesium) and Hybrid III headforms. Results—Eight commercially available head protectors from six manufacturers were tested. The magnitude of the headform accelerations increased as the drop height was increased, ranging from a minimum of 64 g from a height of 0.2 m to a maximum of 1132 g from a height of 0.6 m. The head injury criterion and maximum headform acceleration values followed a similar trend. A steep increase was noted in the magnitude of maximum headform acceleration and head injury criterion when the drop height was increased from 0.4 to 0.5 m. This indicates that the foam material was completely compressed at an impact energy above about 20 J and therefore offers little protection against impacts of greater severity. Repeated tests using a drop height of 0.3 m showed that some helmets exhibit a "memory" effect, whereby impact performance is reduced by up to 50% with repeated impacts. Conclusions—Laboratory tests indicate that current commercially available football headgear performance will not reduce the likelihood of concussion. The absence of internationally recognised standards for soft headgear designed to ameliorate concussion is a major deficiency in sports injury prevention. Key Words: football; headgear; helmet; head; concussion PMID:11049142

  17. VLTI-UT vibrations effort and performances (United States)

    Poupar, Sébastien; Haguenauer, Pierre; Alonso, Jaime; Schuhler, Nicolas; Henriquez, Juan-Pablo; Berger, Jean-Philippe; Bourget, Pierre; Brillant, Stephane; Castillo, Roberto; Gitton, Philippe; Gonte, Frederic; Di Lieto, Nicola; Lizon, Jean-Louis; Merand, Antoine; Woillez, Julien


    The ESO Very Large Telescope Interferometer (VLTI) using the Unit Telescope (UT) was strongly affected by vibrations since the first observations. Investigation by ESO on that subject had started in 2007, with a considerable effort since mid 2008. An important number of investigations on various sub-systems (On telescope: Guiding, Passive supports, Train Coude, insulation of electronics cabinets; On Instruments: dedicated campaign on each instruments with a special attention on the ones equipped with Close Cycle Cooler) were realized. Vibrations were not only recorded and analyzed using the usual accelerometers but also using on use sub-systems as InfRared Image Sensor (IRIS) and Multiple Applications Curvature Adaptive Optics (MACAO) and using a specific tool developed for vibrations measurements Mirror vibrAtion Metrology systeM for the Unit Telescope (MAMMUT). Those tools and systems have been used in order to improve the knowledge on telescope by finding sources. The sources whenever it was possible were damped. As known for years, instruments are still the principal sources of vibrations, for the majority of the UT. A special test in which 2 UTs instruments were completely shut down was realized to determine the minimum Optical Path Length (OPL) achievable. Vibrations is now a part of the instruments interface document and during the installation of any new instrument (KMOS) or system (AOF) a test campaign is realized. As a result some modifications (damping of CCC) can be asked in case of non-compliance. To ensure good operational conditions, levels of vibrations are regularly recorded to control any environmental change.

  18. Real-Time Performance of Mechatronic PZT Module Using Active Vibration Feedback Control. (United States)

    Aggogeri, Francesco; Borboni, Alberto; Merlo, Angelo; Pellegrini, Nicola; Ricatto, Raffaele


    This paper proposes an innovative mechatronic piezo-actuated module to control vibrations in modern machine tools. Vibrations represent one of the main issues that seriously compromise the quality of the workpiece. The active vibration control (AVC) device is composed of a host part integrated with sensors and actuators synchronized by a regulator; it is able to make a self-assessment and adjust to alterations in the environment. In particular, an innovative smart actuator has been designed and developed to satisfy machining requirements during active vibration control. This study presents the mechatronic model based on the kinematic and dynamic analysis of the AVC device. To ensure a real time performance, a H2-LQG controller has been developed and validated by simulations involving a machine tool, PZT actuator and controller models. The Hardware in the Loop (HIL) architecture is adopted to control and attenuate the vibrations. A set of experimental tests has been performed to validate the AVC module on a commercial machine tool. The feasibility of the real time vibration damping is demonstrated and the simulation accuracy is evaluated.

  19. Chatter vibrations of high-performance motorcycles (United States)

    Sharp, R. S.; Watanabe, Y.


    Motorcycle racing teams occasionally experience speed-limiting vibrations of around 25 Hz frequency in mid-corner. The nature of the vibrations has not been closely defined yet and the mechanics are currently not properly understood. Conventional motorcycle-dynamics models are shown here to reveal the existence of a vibration mode that aligns with the experience being referred to, suggesting some explanations. Root loci for variations in speed or cornering vigour, demonstrating modal characteristics for small perturbations from trim states, are employed to indicate how the mode responds to changes in operation and design. Modal participation is examined for a lightly damped case. Influences on the natural frequency and damping of the mode are found and a way of stabilising the mode is suggested.

  20. Effect of shelf aging on vibration transmissibility of anti-vibration gloves. (United States)

    Shibata, Nobuyuki


    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 years 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.

  1. Vibration transfers to measure the performance of vibration isolated platforms on site using background noise excitation (United States)

    Segerink, F. B.; Korterik, J. P.; Offerhaus, H. L.


    This article demonstrates a quick and easy way of quantifying the performance of a vibration-isolated platform. We measure the vibration transfer from floor to table using background noise excitation from the floor. As no excitation device is needed, our setup only requires two identical sensors (in our case, low noise accelerometers), a data acquisition system, and processing software. Background noise excitation from the floor has the additional advantage that any non-linearity in the suspension system relevant to the actual vibration amplitudes will be taken into account. Measurement time is typically a few minutes, depending on the amount of background noise. The (coherent) transfer of the vibrations in the floor to the platform, as well as the (non-coherent) acoustical noise pick-up by the platform are measured. Since we use calibrated sensors, the absolute value of the vibration levels is established and can be expressed in vibration criterion curves. Transfer measurements are shown and discussed for two pneumatic isolated optical tables, a spring suspension system, and a simple foam suspension system.

  2. Time-varying output performances of piezoelectric vibration energy harvesting under nonstationary random vibrations (United States)

    Yoon, Heonjun; Kim, Miso; Park, Choon-Su; Youn, Byeng D.


    Piezoelectric vibration energy harvesting (PVEH) has received much attention as a potential solution that could ultimately realize self-powered wireless sensor networks. Since most ambient vibrations in nature are inherently random and nonstationary, the output performances of PVEH devices also randomly change with time. However, little attention has been paid to investigating the randomly time-varying electroelastic behaviors of PVEH systems both analytically and experimentally. The objective of this study is thus to make a step forward towards a deep understanding of the time-varying performances of PVEH devices under nonstationary random vibrations. Two typical cases of nonstationary random vibration signals are considered: (1) randomly-varying amplitude (amplitude modulation; AM) and (2) randomly-varying amplitude with randomly-varying instantaneous frequency (amplitude and frequency modulation; AM-FM). In both cases, this study pursues well-balanced correlations of analytical predictions and experimental observations to deduce the relationships between the time-varying output performances of the PVEH device and two primary input parameters, such as a central frequency and an external electrical resistance. We introduce three correlation metrics to quantitatively compare analytical prediction and experimental observation, including the normalized root mean square error, the correlation coefficient, and the weighted integrated factor. Analytical predictions are in an excellent agreement with experimental observations both mechanically and electrically. This study provides insightful guidelines for designing PVEH devices to reliably generate electric power under nonstationary random vibrations.

  3. Effect of vibration on visual display terminal work performance. (United States)

    Hsieh, Yao-Hung; Lin, Chiuhsiang Joe; Chen, Hsiao-Ching


    Today electronic visual displays have dramatic use in daily life. Reading these visual displays is subject to their vibration. Using a software-simulation of a vibrated environment, the study investigated the effect of vibration on visual performance and fatigue for several numerical display design characteristics including the font size and the number of digits displayed. Both the frequency and magnitude of vibration had significant effects on the reaction time, accuracy, and visual fatigue. 10 graduate students (23-30 years old; M = 25.6), randomly tested in this experiment, were offered about 25 U.S. dollars for their participation. Numbers in vertical presentation were affected more in vertical vibration than those in horizontal presentation. Analysis showed whenever the display is used in vibration environment, an increased font size may be an effective way to compensate the adverse effect of vibration. The software design of displayed materials must be designed to take the motion effect into consideration to increase the quality of the screen display.

  4. Local vibrations and lift performance of low Reynolds number airfoil

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    TariqAmin Khan


    Full Text Available The 2D incompressible Navier-Stokes equations are solved based on the finite volume method and dynamic mesh technique is used to carry out partial fluid structure interaction. The local flexible structure (hereinafter termed as flexible structure vibrates in a single mode located on the upper surface of the airfoil. The Influence of vibration frequency and amplitude are examined and the corresponding fluid flow characteristics are investigated which add complexity to the inherent problem in unsteady flow. The study is conducted for flow over NACA0012 airfoil at 600≤Re≤3000 at a low angle of attack. Vibration of flexible structure induces a secondary vortex which modifies the pressure distribution and lift performance of the airfoil. At some moderate vibration amplitude, frequency synchronization or lock-in phenomenon occurs when the vibration frequency is close to the characteristic frequency of rigid airfoil. Evolution and shedding of vortices corresponding to the deformation of flexible structure depends on the Reynolds number. In the case of Re≤1000, the deformation of flexible structure is considered in-phase with the vortex shedding i.e., increasing maximum lift is linked with the positive deformation of flexible structure. At Re=1500 a phase shift of about 1/π exists while they are out-of-phase at Re>1500. Moreover, the oscillation amplitude of lift coefficient increases with increasing vibration amplitude for Re≤1500 while it decreases with increasing vibration amplitude for Re>1500. As a result of frequency lock-in, the average lift coefficient is increased with increasing vibration amplitude for all investigated Reynolds numbers (Re. The maximum increase in the average lift coefficient is 19.72% within the range of investigated parameters.

  5. Vibration Performance Comparison Study on Current Fiber Optic Connector Technologies (United States)

    Ott, Melanie N.; Thomes Jr., William J.; LaRocca, Frank V.; Switzer, Robert C.; Chuska, Rick F.; Macmurphy, Shawn L.


    Fiber optic cables are increasingly being used in harsh environments where they are subjected to vibration. Understanding the degradation in performance under these conditions is essential for integration of the fibers into the given application. System constraints oftentimes require fiber optic connectors so subsystems can be removed or assembled as needed. In the present work, various types of fiber optic connectors were monitored in-situ during vibration testing to examine the transient change in optical transmission and the steady-state variation following the event. Inspection of the fiber endfaces and connectors was performed at chosen intervals throughout the testing.


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    Atta Oveisi


    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.

  7. Performance and Vibration Analyses of Lift-Offset Helicopters

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    Jeong-In Go


    Full Text Available A validation study on the performance and vibration analyses of the XH-59A compound helicopter is conducted to establish techniques for the comprehensive analysis of lift-offset compound helicopters. This study considers the XH-59A lift-offset compound helicopter using a rigid coaxial rotor system as a verification model. CAMRAD II (Comprehensive Analytical Method of Rotorcraft Aerodynamics and Dynamics II, a comprehensive analysis code, is used as a tool for the performance, vibration, and loads analyses. A general free wake model, which is a more sophisticated wake model than other wake models, is used to obtain good results for the comprehensive analysis. Performance analyses of the XH-59A helicopter with and without auxiliary propulsion are conducted in various flight conditions. In addition, vibration analyses of the XH-59A compound helicopter configuration are conducted in the forward flight condition. The present comprehensive analysis results are in good agreement with the flight test and previous analyses. Therefore, techniques for the comprehensive analysis of lift-offset compound helicopters are appropriately established. Furthermore, the rotor lifts are calculated for the XH-59A lift-offset compound helicopter in the forward flight condition to investigate the airloads characteristics of the ABC™ (Advancing Blade Concept rotor.

  8. Construction vibration attenuation with distance and its effect on the quality of early-age concrete. (United States)


    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...

  9. Outdoor FSO Communications Under Fog: Attenuation Modeling and Performance Evaluation

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    Esmail, Maged Abdullah


    Fog is considered to be a primary challenge for free space optics (FSO) systems. It may cause attenuation that is up to hundreds of decibels per kilometer. Hence, accurate modeling of fog attenuation will help telecommunication operators to engineer and appropriately manage their networks. In this paper, we examine fog measurement data coming from several locations in Europe and the United States and derive a unified channel attenuation model. Compared with existing attenuation models, our proposed model achieves a minimum of 9 dB, which is lower than the average root-mean-square error (RMSE). Moreover, we have investigated the statistical behavior of the channel and developed a probabilistic model under stochastic fog conditions. Furthermore, we studied the performance of the FSO system addressing various performance metrics, including signal-to-noise ratio (SNR), bit-error rate (BER), and channel capacity. Our results show that in communication environments with frequent fog, FSO is typically a short-range data transmission technology. Therefore, FSO will have its preferred market segment in future wireless fifth-generation/sixth-generation (5G/6G) networks having cell sizes that are lower than a 1-km diameter. Moreover, the results of our modeling and analysis can be applied in determining the switching/thresholding conditions in highly reliable hybrid FSO/radio-frequency (RF) networks.

  10. Virtual Shaker Testing: Simulation Technology Improves Vibration Test Performance (United States)

    Ricci, Stefano; Peeters, Bart; Fetter, Rebecca; Boland, Doug; Debille, Jan


    In the field of vibration testing, the interaction between the structure being tested and the instrumentation hardware used to perform the test is a critical issue. This is particularly true when testing massive structures (e.g. satellites), because due to physical design and manufacturing limits, the dynamics of the testing facility often couples with the test specimen one in the frequency range of interest. A further issue in this field is the standard use of a closed loop real-time vibration control scheme, which could potentially shift poles and change damping of the aforementioned coupled system. Virtual shaker testing is a novel approach to deal with these issues. It means performing a simulation which closely represents the real vibration test on the specific facility by taking into account all parameters which might impact the dynamic behavior of the specimen. In this paper, such a virtual shaker testing approach is developed. It consists of the following components: (1) Either a physical-based or an equation-based coupled electro-mechanical lumped parameter shaker model is created. The model parameters are obtained from manufacturer's specifications or by carrying out some dedicated experiments; (2) Existing real-time vibration control algorithm are ported to the virtual simulation environment; and (3) A structural model of the test object is created and after defining proper interface conditions structural modes are computed by means of the well-established Craig-Bampton CMS technique. At this stage, a virtual shaker test has been run, by coupling the three described models (shaker, control loop, structure) in a co-simulation routine. Numerical results have eventually been correlated with experimental ones in order to assess the robustness of the proposed methodology.

  11. Vibration or balance training on neuromuscular performance in osteopenic women. (United States)

    Stolzenberg, N; Belavý, D L; Rawer, R; Felsenberg, D


    Maintaining neuromuscular function in older age is an important topic for aging societies, especially for older women with low bone density who may be at risk of falls and bone fracture. This randomized controlled trial investigated the effect of resistive exercise with either whole-body vibration training (VIB) or coordination/balance training (BAL) on neuromuscular function (countermovement jump, multiple 1-leg hopping, sit-to-stand test). 68 postmenopausal women with osteopenia or osteoporosis were recruited for the study. 57 subjects completed the 9-month, twice weekly, intervention period. All subjects conducted 30 min of resistance exercise each training day. The VIB-group performed additional training on the Galileo vibration exercise device. The BAL-group performed balance training. An "intent-to-treat" analysis showed greater improvement in the VIB-group for peak countermovement power (p=0.004). The mean [95% confidence interval] effect size for this parameter was a  + 0.9[0.3 to 1.5] W/kg greater change in VIB than BAL after 9 months. In multiple 1-leg hopping, a significantly better performance in the VIB-group after the intervention period was seen on a "per-protocol" analysis only. Both groups improved in the sit-to-stand test. The current study provides evidence that short-duration whole-body vibration exercise can have a greater impact on some aspects of neuromuscular function in post-menopausal women with low bone density than proprioceptive training. © Georg Thieme Verlag KG Stuttgart · New York.

  12. Human Factors Assessment of Vibration Effects on Visual Performance During Launch (United States)

    Holden, Kritina


    The Human Factors Assessment of Vibration Effects on Visual Performance During Launch (Visual Performance) investigation will determine visual performance limits during operational vibration and g-loads on the Space Shuttle, specifically through the determination of minimum readable font size during ascent using planned Orion display formats. Research Summary: The aim of the Human Factors Assessment of Vibration Effects on Visual Performance during Launch (Visual Performance) investigation is to provide supplementary data to that collected by the Thrust Oscillation Seat Detailed Technical Objective (DTO) 695 (Crew Seat DTO) which will measure seat acceleration and vibration from one flight deck and two middeck seats during ascent. While the Crew Seat DTO data alone are important in terms of providing a measure of vibration and g-loading, human performance data are required to fully interpret the operational consequences of the vibration values collected during Space Shuttle ascent. During launch, crewmembers will be requested to view placards with varying font sizes and indicate the minimum readable size. In combination with the Crew Seat DTO, the Visual Performance investigation will: Provide flight-validated evidence that will be used to establish vibration limits for visual performance during combined vibration and linear g-loading. o Provide flight data as inputs to ongoing ground-based simulations, which will further validate crew visual performance under vibration loading in a controlled environment. o Provide vibration and performance metrics to help validate procedures for ground tests and analyses of seats, suits, displays and controls, and human-in-the-loop performance.

  13. Whole body vibration improves attention and motor performance in ...

    African Journals Online (AJOL)

    Background: Whole body vibration (WBV) is a form of physical stimulation via mechanical vibrations transmitted to a subject. It is assumed that WBV induces sensory stimulation in cortical brain regions through the activation of skin and muscle receptors responding to the vibration. The effects of WBV on muscle strength are ...

  14. The influence of longitudinal vibrations on the heat transfer performance of inclined heat pipes

    National Research Council Canada - National Science Library

    Chen, Rong-Horng; Kuo, LW; Lai, Chi-Ming


    This study focused on investigating the influence of longitudinal vibrations, the condensation section temperature, and the inclination angles on the heat transfer performance of grooved cylindrical...

  15. Performance Monitoring of Vibration in Belt Conveyor System

    Directory of Open Access Journals (Sweden)



    Full Text Available We are always using some kind of machines in our daily life starting from fan, refrigerator and washing machines at home. In case of industries of industrial machinery items condition monitoring is important to know onset impending defects. There are so many types of indicating phenomenon such as vibration, heat, debris in oil, noise and sounds which emanate from these in efficiently running machines. This paper presents the vibration related fault identification and maintenance of belt conveyor systems (BCS. After analyzing the spectrum and vibration readings, it was observed that a combination of parallel and angular misalignment between motor & gear box was present causing high axial and radial vibration. The defect was rectified by mechanical maintenance activities and latter the vibration was found reduced within limit. Also the vibration readings were taken after rectification. The above results are presented in this paper.

  16. The influence of seat backrest angle on human performance during whole-body vibration. (United States)

    Paddan, G S; Holmes, S R; Mansfield, N J; Hutchinson, H; Arrowsmith, C I; King, S K; Jones, R J M; Rimell, A N


    This study investigated the effects of reclined backrest angles on cognitive and psycho-motor tasks during exposure to vertical whole-body vibration. Twenty participants were each exposed to three test stimuli of vertical vibration: 2-8 Hz; 8-14 Hz and 14-20 Hz, plus a stationary control condition whilst seated on a vibration platform at five backrest angles: 0° (recumbent, supine) to 90° (upright). The vibration magnitude was 2.0 ms(-2) root-mean-square. The participants were seated at one of the backrest angles and exposed to each of the three vibration stimuli while performing a tracking and choice reaction time tasks; then they completed the NASA-TLX workload scales. Apart from 22.5° seat backrest angle for the tracking task, backrest angle did not adversely affect the performance during vibration. However, participants required increased effort to maintain performance during vibration relative to the stationary condition. These results suggest that undertaking tasks in an environment with vibration could increase workload and risk earlier onset of fatigue. Current vibration standards provide guidance for assessing exposures for seated, standing and recumbent positions, but not for semi-recumbent postures. This paper reports new experimental data systematically investigating the effect of backrest angle on human performance. It demonstrates how workload is elevated with whole-body vibration, without getting affected by backrest angle.

  17. Performance of active vibration control technology: the ACTEX flight experiments (United States)

    Nye, T. W.; Manning, R. A.; Qassim, K.


    This paper discusses the development and results of two intelligent structures space-flight experiments, each of which could affect architecture designs of future spacecraft. The first, the advanced controls technology experiment I (ACTEX I), is a variable stiffness tripod structure riding as a secondary payload on a classified spacecraft. It has been operating well past its expected life since becoming operational in 1996. Over 60 on-orbit experiments have been run on the ACTEX I flight experiment. These experiments form the basis for in-space controller design problems and for concluding lifetime/reliability data on the active control components. Transfer functions taken during the life of ACTEX I have shown consistent predictability and stability in structural behavior, including consistency with those measurements taken on the ground prior to a three year storage period and the launch event. ACTEX I can change its modal characteristics by employing its dynamic change mechanism that varies preloads in portions of its structure. Active control experiments have demonstrated maximum vibration reductions of 29 dB and 16 dB in the first two variable modes of the system, while operating over a remarkable on-orbit temperature range of -80 °C to 129 °C. The second experiment, ACTEX II, was successfully designed, ground-tested, and integrated on an experimental Department of Defense satellite prior to its loss during a launch vehicle failure in 1995. ACTEX II also had variable modal behavior by virtue of a two-axis gimbal and added challenges of structural flexibility by being a large deployable appendage. Although the loss of ACTEX II did not provide space environment experience, ground testing resulted in space qualifying the hardware and demonstrated 21 dB, 14 dB, and 8 dB reductions in amplitude of the first three primary structural modes. ACTEX II could use either active and/or passive techniques to affect vibration suppression. Both experiments trailblazed

  18. Effect Of Vibration On Occupant Driving Performances Measured By Simulated Driving

    Directory of Open Access Journals (Sweden)

    Amzar Azizan


    Full Text Available Although the performance of vehicle driver has been well investigated in many types of environments however drowsy driving caused by vibration has received far less attention. Experiment procedures comprised of two 10-minutes simulated driving sessions in no-vibration condition and with-vibration condition. In with-vibration condition volunteers were exposed to a Gaussian random vibration with 1-15 Hz frequency bandwidth at 0.2 ms-2 r.m.s. for 30-minutes. A deviation in lane position and vehicle speed were recorded and analyzed. Volunteers have also rated their subjective drowsiness by giving score using Karolinska Sleepiness Scale KSS every 5-minutes interval. Strong evidence of driving impairment following 30-minutes exposure to vibration were found significant in all volunteers p 0.05.

  19. Evaluation of Breaking Performance in Vibration-Assisted Electrostatic Surface Induction Actuator

    DEFF Research Database (Denmark)

    Nemoto, Takeru; Zsurzsan, Tiberiu-Gabriel; Yamamoto, Akio


    force can be changed by turning on and off the vibrator. The friction change can be utilized for high-performance slider motion control; for example, friction can be increased by switching off the vibrator when the slider needs to stop. In this paper, we evaluated how fast the slider can stop in several...

  20. SDBI 1904: Human Factors Assessment of Vibration Effects on Visual Performance during Launch (United States)

    Thompson, Shelby G.; Holden, Kritina; Root, Phillip; Ebert, Douglas; Jones, Jeffery; Adelstein, Bernard


    The primary objective of the of Human Factors Short Duration Bioastronautics Investigation (SDBI) 1904 is to determine visual performance limits during operational vibration and g-loads, specifically through the determination of minimal usable font sized using Orion-type display formats. Currently there is little to no data available to quantify human visual performance under these extreme conditions. Existing data on shuttle vibration magnitude and frequency is incomplete, does not address sear and crew vibration in the current configuration, and does not address human visual performance. There have been anecdotal reports of performance decrements from shuttle crews, but no structured data has been collected. The SDBI is a companion effort to the Detailed Test Objective (DTO) 695, which will measure shuttle seat accelerations (vibration) during ascent. Data fro the SDBI will serve an important role in interpreting the DTO vibration data. This data will be collected during the ascent phase of three shuttle missions (STS-119, 127, and 128). Both SDBI1904 and DTO 695 are low impact with respect to flight resources, and combined they represent an efficient and focused problem solving approach. The SDBI and DTO data will be correlated to determine the nature of perceived visual performance under varying vibrations and g-loads. This project will provide: 1) Immediate data for developing preliminary human performance vibration requirements; 2) Flight validated inputs for ongoing and future ground-based research; and 3) Information of functional needs that will drive Orion display format design decisions.

  1. Design of an Ultrasonic Elliptic-Vibration Shoe and Its Performance in Ultrasonic Elliptic-Vibration-Shoe Centerless Grinding (United States)

    Fan, Yufeng; Wu, Yongbo; Kato, Masana; Tachibana, Toru; Syoji, Katsuo; Kuriyagawa, Tsunemoto

    We describe the design of an ultrasonic elliptic-vibration shoe and its performance in ultrasonic elliptic-vibration-shoe centerless grinding. First, the vibration modes of the shoe for the bending and longitudinal directions are discussed and determined from the point of view of fixing the support of the shoe. Then the structure and dimensions of the shoe are determined by FEM (Finite Element Method) analysis. In order to clarify the performance of the produced shoe, an evaluation apparatus is built. The elliptic motions under different applied voltages are investigated using laser vibrometers. Finally, workpiece rotational motion control tests and actual grinding operations are carried out. As a result, it is clarified that the workpiece rotational speed changes linearly with variation of the applied voltage. This indicates that the workpiece rotational motion can be precisely controlled by the elliptic motion of the shoe. In addition, the workpiece roundness was clearly improved from an initial value of 25µm to a final value of 0.64µm after grinding, indicating that the produced shoe performed well in actual grinding operations.

  2. Vibration Attenuation of Magnetorheological Landing Gear System with Human Simulated Intelligent Control

    Directory of Open Access Journals (Sweden)

    X. M. Dong


    Full Text Available Due to the short duration of impulsive impact of an aircraft during touchdown, a traditional landing gear can only achieve limited performance. In this study, a magnetorheological (MR absorber is incorporated into a landing gear system; an intelligent control algorithm, a human simulated intelligent control (HSIC, is proposed to adaptively tune the MR absorber. First, a two degree-of-freedom (DOF dynamic model of a landing gear system featuring an MR absorber is constructed. The control model of an MR damper is also developed. After analyzing the impact characteristic during touchdown, an HSIC is then formulated. A genetic algorithm is adopted to optimize the control parameters of HSIC. Finally, a numerical simulation is performed to validate the proposed damper and the controller considering the varieties of sink velocities and sprung masses. The simulations under different scenarios show that the landing gear system based on the MR absorber can greatly reduce the peak impact load of sprung mass within the stroke. The biggest improvement of the proposed controller is over 40% compared to that of skyhook controller. Furthermore, HSIC exhibits better adaptive ability and strong robustness than skyhook controller under various payloads and sink velocities.

  3. Short Duration Bioastronautics Investigation 1904: Human Factors Assessment of Vibration Effects on Visual Performance during Launch (United States)

    Thompson, Shelby; Holden, Kritina; Ebert, Douglas; Root, Phillip; Adelstein, Bernard; Jones, Jeffery


    The primary objective of the Short Duration Bioastronautics Investigation (SDBI) 1904 was to determine visual performance limits during Shuttle operational vibration and g-loads, specifically through the determination of minimal usable font sizes using Orion-type display formats. Currently there is little to no data available to quantify human visual performance under the extreme g- and vibration conditions of launch. Existing data on shuttle vibration magnitude and frequency is incomplete and does not address human visual performance. There have been anecdotal reports of performance decrements from shuttle crews, but no structured data have been collected. Previous work by NASA on the effects of vibration and linear g-loads on human performance was conducted during the Gemini era, but these experiments were performed using displays and controls that are dramatically different than current concepts being considered by the Constellation Program. Recently, three investigations of visual performance under vibration have been completed at NASA Ames Research Center: the first examining whole-body vibration, the second employing whole-body vibration coupled with a sustained g-load, and a third examining the effects of peak versus extended duration vibration. However, all of these studies were conducted using only a single x-axis direction (eyeballs in/out). Estimates of thrust oscillations from the Constellation Ares-I first stage are driving the need for realistic human performance requirements. SDBI 1904 was an opportunity to address the need for requirements by conducting a highly focused and applied evaluation in a relevant spaceflight environment. The SDBI was a companion effort to Detailed Test Objective (DTO) 695, which measured shuttle seat accelerations (vibration) during ascent. Data from the SDBI will serve an important role in interpreting the DTO vibration data. Both SDBI 1904 and DTO 695 were low impact with respect to flight resources, and combined, they

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

    Directory of Open Access Journals (Sweden)

    H Ghorbanpour


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

  5. Performance of a table vibration type coffee grading machine

    Directory of Open Access Journals (Sweden)

    Sukrisno Widyotomo


    Full Text Available One of important coffee beans quality is the size uniformity. To confirm with the standart requirement, coffee beans have to be graded before being traded. Until now, grading process is still carried out fully manual, so that the grading cost is very expensive about 40% of total processing cost. Meanwhile, shortage of skill workers is as a limiting factor of the process. Therefore, machine for grading coffee beans is good alternative for grading cost. Indonesian Coffee and Cocoa Research Institute has designed a table vibration type coffee grading machine for grouping of coffee beans in order to consistent quality and reduce grading cost. The machine has dimension of 272 cm length, 126 cm height, and 144 cm width. The machine has three primary components, i.e. grader table, combustion engine, and beam. The machine has three kinds of grader table that each grader table has different holes size, i.e. 7 mm x 7 mm for top grader table, 5 mm x 5 mm for axle grader table, and 4 mm x 4 mm for bottom grader table. Each grader table has dimension of 206 cm length, 105.5 cm height, and 14 cm width. The grading mechanism is by vibration grader table with the power source 5.5 HP combustion engine. The results shown that the outlet are in farms of three grades of coffee beans with connected to each compartement. Assessment of the grading machine reveals that the optimum capacity of 1,406 kg/hour reached when the speed 2,600 rpm and the angle 10O. Economic analysis showed that operational cost for grading one kilogram Robusta coffee beans with moisture content 13—14% wet basis is Rp 7.17.Key words : grading, coffee, quality, vibration table.

  6. Enhancement of rowing performance in athletes after focal muscle vibration therapy

    Directory of Open Access Journals (Sweden)

    Francesca Grasso


    Full Text Available Muscle vibration has been reported to induce long lasting effects on proprioception when applied on specific body segment. The aim of this study was to evaluate the effect of focal muscle vibration applied on quadriceps and latissimus dorsi muscles in athletes evaluate during rowing test. Sixteen volunteered national level sculling stroke rowers has been randomized in a study group and in a control group (treated with sham vibration. The overall kinematic consistency, joints angular acceleration patterns and performance test has been used as evaluation. Results showed statistical significant values for angular accelerations at the knee and shoulder joints and significant effect of the time course of the trial. Vibration treatment seems to be an useful proprioceptive stimulation in sport activities to improve muscle control and performance.

  7. Vibration attenuation of rotating machines by application of magnetorheological dampers to minimize energy losses in the rotor support (United States)

    Zapoměl, J.; Ferfecki, P.


    A frequently used technological solution for minimization of undesirable effects caused by vibration of rotating machines consists in placing damping devices in the rotor supports. The application of magnetorheological squeeze film dampers enables their optimum performance to be achieved in a wide range of rotating speeds by adapting their damping effect to the current operating conditions. The damping force, which is produced by squeezing the layer of magnetorheological oil, can be controlled by changing magnetic flux passing through the lubricant. The force acting between the rotor and its frame is transmitted through the rolling element bearing, the lubricating layer and the squirrel spring. The loading of the bearing produces a time variable friction moment, energy losses, uneven rotor running, and has an influence on the rotor service life and the current fluctuation in electric circuits. The carried out research consisted in the development of a mathematical model of a magnetorheological squeeze film damper, its implementation into the computational models of rotor systems, and in performing the study on the dependence of the energy losses and variation of the friction moment on the damping force and its control. The new and computationally stable mathematical model of a magnetorheological squeeze film damper, its implementation in the computational models of rigid rotors and learning more on the energy losses generated in the rotor supports in dependence on the damping effect are the principal contributions of this paper. The results of the computational simulations prove that a suitable control of the damping force enables the energy losses to be reduced in a wide velocity range.

  8. Investigation of Gearbox Vibration Transmission Paths on Gear Condition Indicator Performance (United States)

    Dempsey, Paula J.; Islam, AKM Anwarul; Feldman, Jason; Larsen, Chris


    Helicopter health monitoring systems use vibration signatures generated from damaged components to identify transmission faults. For damaged gears, these signatures relate to changes in dynamics due to the meshing of the damaged tooth. These signatures, referred to as condition indicators (CI), can perform differently when measured on different systems, such as a component test rig, or a full-scale transmission test stand, or an aircraft. These differences can result from dissimilarities in systems design and environment under dynamic operating conditions. The static structure can also filter the response between the vibration source and the accelerometer, when the accelerometer is installed on the housing. To assess the utility of static vibration transfer paths for predicting gear CI performance, measurements were taken on the NASA Glenn Spiral Bevel Gear Fatigue Test Rig. The vibration measurements were taken to determine the effect of torque, accelerometer location and gearbox design on accelerometer response. Measurements were taken at the housing and compared while impacting the gear set near mesh. These impacts were made at gear mesh to simulate gear meshing dynamics. Data measured on a helicopter gearbox installed in a static fixture were also compared to the test rig. The behavior of the structure under static conditions was also compared to CI values calculated under dynamic conditions. Results indicate that static vibration transfer path measurements can provide some insight into spiral bevel gear CI performance by identifying structural characteristics unique to each system that can affect specific CI response.

  9. Vibration-induced coherence enhancement of the performance of a biological quantum heat engine. (United States)

    Chen, Hong-Bin; Chiu, Pin-Yi; Chen, Yueh-Nan


    Photosynthesis has been a long-standing research interest due to its fundamental importance. Recently, studies on photosynthesis processes also have inspired attention from a thermodynamical aspect when considering photosynthetic apparatuses as biological quantum heat engines. Quantum coherence is shown to play a crucial role in enhancing the performance of these quantum heat engines. Based on the experimentally reported structure, we propose a quantum heat engine model with a non-Markovian vibrational mode. We show that one can obtain a performance enhancement easily for a wide range of parameters in the presence of the vibrational mode. Our results provide insights into the photosynthetic processes and a design principle mimicking natural organisms.

  10. Vibration-induced coherence enhances the performance of a biological quantum heat engine

    CERN Document Server

    Chen, Hong-Bin; Chen, Yueh-Nan


    Photosynthesis has been the long-standing research interest due to its fundamental importance. Recently, studies on photosynthesis processes also inspire attention from thermodynamical aspect when considering photosynthetic apparatuses as biological quantum heat engines. Quantum coherence is shown to play a crucial role in enhancing the performance of these quantum heat engines. Based on the experimentally reported structure, we propose a quantum heat engine model with a non-Markovian vibrational mode. We show that one can obtain a performance enhancement easily for a wide range of parameters in the presence of the vibrational mode. Our results suggest new insights into the photosynthetic processes and a design principle mimicking natural organisms.

  11. Design and Performance Testing of a Novel Three-Dimensional Elliptical Vibration Turning Device

    Directory of Open Access Journals (Sweden)

    Jieqiong Lin


    Full Text Available A novel three-dimensional (3D elliptical vibration turning device which is on the basis of the leaf-spring-flexure-hinges-based (LSFH-based double parallel four-bar linkages (DPFLMs has been proposed. In order to evaluate the performance of the developed 3D elliptical vibration cutting generator (EVCG, the off-line tests were carried out to investigate the stroke, dynamic performance, resolution, tracking accuracy and hysteresis along the three vibration axes. Experimental results indicate that the maximum stroke of three vibration axes can reach up to 26 μm. The working bandwidth can reach up to 1889 Hz. The resolution and hysteresis tests show that the developed 3D EVCG has a good tracking accuracy, relative high resolution and low hysteresis, which is appropriate for micro/nano machining. Kinematical modeling is carried out to investigate the tool vibration trajectory. Experimental results shown that the simulation results agree well with the experimental one, which indicate that the developed 3D EVCG can be used as an option for micro/nano machining.

  12. Induced vibrations increase performance of a winged self-righting robot (United States)

    Othayoth, Ratan; Xuan, Qihan; Li, Chen

    When upside down, cockroaches can open their wings to dynamically self-right. In this process, an animal often has to perform multiple unsuccessful maneuvers to eventually right, and often flails its legs. Here, we developed a cockroach-inspired winged self-righting robot capable of controlled body vibrations to test the hypothesis that vibrations assist self-righting transitions. Robot body vibrations were induced by an oscillating mass (10% of body mass) and varied by changing oscillation frequency. We discovered that, as the robot's body vibrations increased, righting probability increased, and righting time decreased (P <0.0001, ANOVA), confirming our hypothesis. To begin to understand the underlying physics, we developed a locomotion energy landscape model. Our model revealed that the kinetic energy fluctuations due to vibrations were comparable to the potential energy barriers required to transition from a metastable overturned orientation to an upright orientation. Our study supports the plausibility of locomotion energy landscapes for understanding locomotor transitions, but highlights the need for further stochastic modeling to capture the uncertain nature of when righting maneuvers result in successful righting.

  13. Performance of nonlinear mechanical, resonant-shunted piezoelectric, and electronic vibration absorbers for multi-degree-of-freedom structures (United States)

    Agnes, Gregory Stephen

    Linear vibration absorbers are a valuable tool used to suppress vibrations due to harmonic excitation in structural systems. Limited evaluation of the performance of nonlinear vibration absorbers for nonlinear structures exists in the current literature. The state of the art is extended in this work to vibration absorbers in their three major physical implementations: the mechanical vibration absorber, the inductive-resistive shunted piezoelectric vibration absorber, and the electronic vibration absorber (also denoted a positive position feedback controller). A single, consistent, physically similar model capable of examining the response of all three devices is developed. The performance of vibration absorbers attached to single-degree-of-freedom structures is next examined for performance, robustness, and stability. Perturbation techniques and numerical analysis combine to yield insight into the tuning of nonlinear vibration absorbers for both linear and nonlinear structures. The results both clarify and validate the existing literature on mechanical vibration absorbers. Several new results, including an analytical expression for the suppression region's location and bandwidth and requirements for its robust performance, are derived. Nonlinear multiple-degree-of-freedom structures are next evaluated. The theory of Non-linear Normal Modes is extended to include consideration of modal damping, excitation, and small linear coupling, allowing estimation of vibration absorber performance. The dynamics of the N+1-degree-of-freedom system reduce to those of a two-degree-of-freedom system on a four-dimensional nonlinear modal manifold, thereby simplifying the analysis. Quantitative agreement is shown to require a higher order model which is recommended for future investigation. Finally, experimental investigation on both single and multi-degree-of-freedom systems is performed since few experiments on this topic are reported in the literature. The experimental results


    Directory of Open Access Journals (Sweden)

    David M. Bazett-Jones


    Full Text Available While it seems that whole body vibration (WBV might be an effective modality to enhance physical performance, the proper prescription of WBV for performance enhancement remains unknown. The purpose of this study was to compare the immediate effect of various WBV accelerations on counter movement jump (CMJ height, the duration of any effect, and differences between men and women. Forty-four participants (33 men, 11 women participated in no less than four CMJ familiarization sessions and completed all vibration sessions. Participants performed a pre-test (three maximal CMJs, followed randomly by one of five WBV accelerations; 1g (no-WBV control, 2.16g, 2.80g, 4.87g, and 5.83g. Participants performed three maximal CMJs immediately, five, and 10 minutes following each 45 sec WBV session. The mean of the three performances was used and calculated as a percentage of the pre-vibration mean value. A Repeated Measures Analysis of Variance (ANOVA; acceleration x time x gender model was used to analyze the data. The two-way interactions of acceleration-gender (p = 0.033 and time-gender (p = 0.050 were significant. Women performed significantly better following the 2.80g (p = 0.0064 and 5.83g (p = 0. 0125 WBV sessions compared to the 1g (control session. Men, however, did not experience performance enhancing effects following any of the vibration sessions. While significant differences did not occur between time in either gender, the effects of the 45 sec WBV session in women were transient, lasting approximately five minutes. During the prescription of WBV, gender should be considered given that the results of this study seem to indicate that men and women respond differently to WBV. The results of this study suggest that WBV might be a useful modality as applied during the pre-competition warm-up

  15. Parameter definition using vibration prediction software leads to significant drilling performance improvements

    Energy Technology Data Exchange (ETDEWEB)

    Amorim, Dalmo; Hanley, Chris Hanley; Fonseca, Isaac; Santos, Juliana [National Oilwell Varco, Houston TX (United States); Leite, Daltro J.; Borella, Augusto; Gozzi, Danilo [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)


    The understanding and mitigation of downhole vibration has been a heavily researched subject in the oil industry as it results in more expensive drilling operations, as vibrations significantly diminish the amount of effective drilling energy available to the bit and generate forces that can push the bit or the Bottom Hole Assembly (BHA) off its concentric axis of rotation, producing high magnitude impacts with the borehole wall. In order to drill ahead, a sufficient amount of energy must be supplied by the rig to overcome the resistance of the drilling system, including the reactive torque of the system, drag forces, fluid pressure losses and energy dissipated by downhole vibrations, then providing the bit with the energy required to fail the rock. If the drill string enters resonant modes of vibration, not only does it decreases the amount of available energy to drill, but increases the potential for catastrophic downhole equipment and drilling bit failures. In this sense, the mitigation of downhole vibrations will result in faster, smoother, and cheaper drilling operations. A software tool using Finite Element Analysis (FEA) has been developed to provide better understanding of downhole vibration phenomena in drilling environments. The software tool calculates the response of the drilling system at various input conditions, based on the design of the wellbore along with the geometry of the Bottom Hole Assembly (BHA) and the drill string. It identifies where undesired levels of resonant vibration will be driven by certain combinations of specific drilling parameters, and also which combinations of drilling parameters will result in lower levels of vibration, so the least shocks, the highest penetration rate and the lowest cost per foot can be achieved. With the growing performance of personal computers, complex software systems modeling the drilling vibrations using FEA has been accessible to a wider audience of field users, further complimenting with real time

  16. Study of the Mechanical Properties and Vibration Isolation Performance of a Molecular Spring Isolator

    Directory of Open Access Journals (Sweden)

    Muchun Yu


    Full Text Available Molecular Spring Isolator (MSI is a novel passive vibration isolation technique, providing High-Static-Low-Dynamic (HSLD stiffness based on the use of molecular spring material. The molecular spring material is a solid-liquid mixture consisting of water and hydrophobic nanoporous materials. Under a certain level of external pressure, water molecules can intrude into the hydrophobic pores of nanoporous materials, developing an additional solid-liquid interface. Such interfaces are able to store, release, and transform mechanical energy, providing properties like mechanical spring. Having been only recently developed, the basic mechanic properties of a MSI have not been studied in depth. This paper focuses on the stiffness influence factors, the dynamic frequency response, and the vibration isolation performance of a MSI; these properties help engineers to design MSIs for different engineering applications. First, the working mechanism of a MSI is introduced from a three-dimensional general view of the water infiltration massive hydrophobic nanoporous pores. Next, a wide range of influence factors on the stiffness properties of MSI are studied. In addition, the frequency response functions (FRFs of the MSI vibration isolation system are studied utilizing the matching method based on equivalent piecewise linear (EPL system. Finally, the vibration isolation properties of MSI are evaluated by force transmissibility.

  17. Small and inconsistent effects of whole body vibration on athletic performance : a systematic review and meta-analysis

    NARCIS (Netherlands)

    Hortobagyi, Tibor; Lesinski, Melanie; Fernandez-del-Olmo, Miguel; Granacher, Urs

    We quantified the acute and chronic effects of whole body vibration on athletic performance or its proxy measures in competitive and/or elite athletes. Systematic literature review and meta-analysis. Whole body vibration combined with exercise had an overall 0.3 % acute effect on maximal voluntary

  18. High-damping-performance magnetorheological material for passive or active vibration control (United States)

    Liu, Taixiang; Yang, Ke; Yan, Hongwei; Yuan, Xiaodong; Xu, Yangguang


    Optical assembly and alignment system plays a crucial role for the construction of high-power or high-energy laser facility, which attempts to ignite fusion reaction and go further to make fusion energy usable. In the optical assembly and alignment system, the vibration control is a key problem needs to be well handled and a material with higher damping performance is much desirable. Recently, a new kind of smart magneto-sensitive polymeric composite material, named magnetorheological plastomer (MRP), was synthesized and reported as a high-performance magnetorheological material and this material has a magneto-enhanced high-damping performance. The MRP behaves usually in an intermediate state between fluid-like magnetorheological fluid and solid-like magnetorheological elastomer. The state of MRP, as well as the damping performance of MRP, can be tuned by adjusting the ratio of hard segments and soft segments, which are ingredients to synthesize the polymeric matrix. In this work, a series of MRP are prepared by dispersing micron-sized, magneto-sensitive carbonyl iron powders with related additives into polyurethane-based, magnetically insensitive matrix. It is found that the damping performance of MRP depends much on magnetic strength, shear rate, carbonyl iron content and shear strain amplitude. Especially, the damping capacity of MRP can be tuned in a large range by adjusting external magnetic field. It is promising that the MRP will have much application in passive and active vibration control, such as vibration reduction in optical assembly and alignment system, vibration isolation or absorption in vehicle suspension system, etc.


    Directory of Open Access Journals (Sweden)

    Giorgos Paradisis


    Full Text Available The aim of this study was to investigate the effect of 6 wk of whole body vibration (WBV training on sprint running kinematics and explosive strength performance. Twenty-four volunteers (12 women and 12 men participated in the study and were randomised (n = 12 into the experimental and control groups. The WBV group performed a 6-wk program (16-30 min·d-1, 3 times a week on a vibration platform. The amplitude of the vibration platform was 2.5 mm and the acceleration was 2.28 g. The control group did not participate in any training. Tests were performed Pre and post the training period. Sprint running performance was measured during a 60 m sprint where running time, running speed, step length and step rate were calculated. Explosive strength performance was measured during a counter movement jump (CMJ test, where jump height and total number of jumps performed in a period of 30 s (30CVJT. Performance in 10 m, 20 m, 40 m, 50 m and 60 m improved significantly after 6 wk of WBV training with an overall improvement of 2.7%. The step length and running speed improved by 5.1% and 3.6%, and the step rate decreased by 3.4%. The countermovement jump height increased by 3.3%, and the explosive strength endurance improved overall by 7.8%. The WBV training period of 6 wk produced significant changes in sprint running kinematics and explosive strength performance

  20. Determination of the transient vibrations of a rigid rotor attenuated by a semiactive magnetorheological damping device by means of computational modelling

    Directory of Open Access Journals (Sweden)

    Zapoměl J.


    Full Text Available Unbalance is the principal source of increase of time varying forces transmitted between the rotor and its stationary part. Their magnitudes can be considerably reduced if the rotor is flexibly suspended and if the damping devices are added to the support elements. Their damping effect must be high for low rotor velocities and small for velocities approximately higher than the critical one to minimize the transmitted forces and the vibrations amplitude. This implies to achieve maximum efficiency of the damping elements, their damping effect has to be adaptable to the current operating conditions. Such technological solution is offered by application of a squeeze film magnetorheological damper. Its hybrid variant consisting of two damping units (one controllable in a serial arrangement is investigated in this paper. The damping takes place in two concentric lubricating films formed by normal and magnetorheological oils. The damper is equipped with an electric coil generating magnetic flux passing through the layer of the magnetorheological fluid. As resistance against its flow depends on magnetic induction, changing magnitude of the applied current enables to control the damping force. In the computational model, the rotor is considered to be absolutely rigid, unbalanced and the damping elements are represented by force couplings. The goal of the analysis is to study influence of the investigated magnetorheological damper on behaviour of a rigid rotor during different transient regimes. A special attention is focused on passing the rotor through the critical speed and on planning the dependence of the applied current on speed of the rotor rotation to achieve the optimum compromise between minimizing the transmitted forces and maximum attenuation of the rotor vibrations.

  1. Sound vibration signal processing for detection and identification detonation (knock) to optimize performance Otto engine (United States)

    Sujono, A.; Santoso, B.; Juwana, W. E.


    Problems of detonation (knock) on Otto engine (petrol engine) is completely unresolved problem until now, especially if want to improve the performance. This research did sound vibration signal processing engine with a microphone sensor, for the detection and identification of detonation. A microphone that can be mounted is not attached to the cylinder block, that's high temperature, so that its performance will be more stable, durable and inexpensive. However, the method of analysis is not very easy, because a lot of noise (interference). Therefore the use of new methods of pattern recognition, through filtration, and the regression function normalized envelope. The result is quite good, can achieve a success rate of about 95%.

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

    Directory of Open Access Journals (Sweden)

    Wen-qi Zou


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

  3. The influence of longitudinal vibrations on the heat transfer performance of inclined heat pipes

    Directory of Open Access Journals (Sweden)

    Rong-Horng Chen


    Full Text Available This study focused on investigating the influence of longitudinal vibrations, the condensation section temperature, and the inclination angles on the heat transfer performance of grooved cylindrical copper heat pipes with lengths of 600 and 150 mm and an outer diameter of 8 mm. The inclination angles of the tested heat pipes were 0°, ±45°, and ±90°. Longitudinal vibrations with frequencies of 3, 4, 5, 6, and 9 Hz and amplitudes of 2.8, 5, 10, 15, 20, and 25 mm, which resulted in accelerations between 0.1 and 1.01 g, were experimentally tested. The condensation section temperatures were set at 20°C, 30°C, and 40°C. A heating jacket and a cooling sleeve were installed at the evaporation and condensation sections of the test cell to simulate a constant heat flux and a constant temperature boundary, respectively. The results showed that with the heat pipe placed with the condensation section on top and the evaporation section on bottom, a fairly low and constant thermal resistance (approximately 0.25 K/W for the 600-mm heat pipe and 0.75–1.2 K/W for the 150-mm heat pipe was obtained, both with and without heat pipe vibration and regardless of the condensation section temperature.

  4. Effects of whole body vibration training on muscle strength and sprint performance in sprint-trained athletes. (United States)

    Delecluse, C; Roelants, M; Diels, R; Koninckx, E; Verschueren, S


    Despite the expanding use of Whole Body Vibration training among athletes, it is not known whether adding Whole Body Vibration training to the conventional training of sprint-trained athletes will improve speed-strength performance. Twenty experienced sprint-trained athletes (13 male symbol, 7 female symbol, 17-30 years old) were randomly assigned to a Whole Body Vibration group (n=10: 6 male symbol and 4 female symbol) or a Control group (n=10: 7 male symbol, 3 female symbol). During a 5-week experimental period all subjects continued their conventional training program, but the subjects of the Whole Body Vibration group additionally performed three times weekly a Whole Body Vibration training prior to their conventional training program. The Whole Body Vibration program consisted of unloaded static and dynamic leg exercises on a vibration platform (35-40 Hz, 1.7-2.5 mm, Power Plate). Pre and post isometric and dynamic (100 degrees/s) knee-extensor and -flexor strength and knee-extension velocity at fixed resistances were measured by means of a motor-driven dynamometer (Rev 9000, Technogym). Vertical jump performance was measured by means of a contact mat. Force-time characteristics of the start action were assessed using a load cell mounted on each starting block. Sprint running velocity was recorded by means of a laser system. Isometric and dynamic knee-extensor and knee-flexor strength were unaffected (p>0.05) in the Whole Body Vibration group and the Control group. As well, knee-extension velocity remained unchanged (p>0.05). The duration of the start action, the resulting start velocity, start acceleration, and sprint running velocity did not change (>0.05) in either group. In conclusion, this specific Whole Body Vibration protocol of 5 weeks had no surplus value upon the conventional training program to improve speed-strength performance in sprint-trained athletes.

  5. Joint Service Aircrew Mask (JSAM) Rotary Wing (RW): MPU-5 Noise Attenuation Performance (United States)


    specifications and exceeded the attenuation performance of the helmets alone. 1.0 INTRODUCTION The noise environment in the cockpit of... cockpit and to provide satisfactory voice communications. The HGU-56/P and HGU-84/P were rotary wing aircrew helmet systems manufactured by Gentex...hood/hoodring subassembly, (2) face plate subassembly and (3) supply subassembly. The hood assembly and face plate assembly are shown in Figure 2

  6. A proposal on evaluation method of neutron absorption performance to substitute conventional neutron attenuation test

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Je Hyun; Shim, Chang Ho [Dept. of Nuclear Engineering, Hanyang University, Seoul (Korea, Republic of); Kim, Sung Hyun [Nuclear Fuel Cycle Waste Treatment Research Division, Research Reactor Institute, Kyoto University, Osaka (Japan); Choe, Jung Hun; Cho, In Hak; Park, Hwan Seo [Ionizing Radiation Center, Nuclear Fuel Cycle Waste Treatment Research Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Hyun Seo; Kim, Jung Ho; Kim, Yoon Ho [Ionizing Radiation Center, Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)


    For a verification of newly-developed neutron absorbers, one of guidelines on the qualification and acceptance of neutron absorbers is the neutron attenuation test. However, this approach can cause a problem for the qualifications that it cannot distinguish how the neutron attenuates from materials. In this study, an estimation method of neutron absorption performances for materials is proposed to detect both direct penetration and back-scattering neutrons. For the verification of the proposed method, MCNP simulations with the experimental system designed in this study were pursued using the polyethylene, iron, normal glass and the vitrified form. The results show that it can easily test neutron absorption ability using single absorber model. Also, from simulation results of single absorber and double absorbers model, it is verified that the proposed method can evaluate not only the direct thermal neutrons passing through materials, but also the scattered neutrons reflected to the materials. Therefore, the neutron absorption performances can be accurately estimated using the proposed method comparing with the conventional neutron attenuation test. It is expected that the proposed method can contribute to increase the reliability of the performance of neutron absorbers.

  7. Significant Attenuation of Lightly Damped Resonances Using Particle Dampers (United States)

    Smith, Andrew; LaVerde, Bruce; Hunt, Ron; Knight, Joseph Brent


    When equipment designs must perform in a broad band vibration environment it can be difficult to avoid resonances that affect life and performance. This is especially true when an organization seeks to employ an asset from a heritage design in a new, more demanding vibration environment. Particle dampers may be used to provide significant attenuation of lightly damped resonances to assist with such a deployment of assets by including only a very minor set of modifications. This solution may be easier to implement than more traditional attenuation schemes. Furthermore, the cost in additional weight to the equipment can be very small. Complexity may also be kept to a minimum, because the particle dampers do not require tuning. Attenuating the vibratory response with particle dampers may therefore be simpler (in a set it and forget it kind of way) than tuned mass dampers. The paper will illustrate the use of an "equivalent resonance test jig" that can assist designers in verifying the potential resonance attenuation that may be available to them during the early trade stages of the design. An approach is suggested for transforming observed attenuation in the jig to estimated performance in the actual service design. KEY WORDS: Particle Damper, Performance in Vibration Environment, Damping, Resonance, Attenuation, Mitigation of Vibration Response, Response Estimate, Response Verification.

  8. Whole-Body Vibration Training Effect on Physical Performance and Obesity in Mice


    Huang, Chi-Chang; Tseng, Tzu-Ling; Huang, Wen-Ching; Chung, Yi-Hsiu; Chuang, Hsiao-Li; Wu, Jyh-Horng


    The purpose of this study was to verify the beneficial effects of whole-body vibration (WBV) training on exercise performance, physical fatigue and obesity in mice with obesity induced by a high-fat diet (HFD). Male C57BL/6 mice were randomly divided into two groups: normal group (n=6), fed standard diet (control), and experimental group (n=18), fed a HFD. After 4-week induction, followed by 6-week WBV of 5 days per week, the 18 obese mice were divided into 3 groups (n=6 per group): HFD with ...

  9. Performance analysis of rain attenuation on earth-to-satellite microwave links design in Libya (United States)

    Rafiqul Islam, Md; Hussein Budalal, Asma Ali; Habaebi, Mohamed H.; Badron, Khairayu; Fadzil Ismail, Ahmad


    Performances of earth-to-satellite microwave links operating in Ku, Ka, and V-bands are degraded by the environment and strongly attenuated by rain. Rain attenuation is the most significant consideration and challenge to design a reliable earth-to-satellite microwave links for these frequency bands. Hence, it is essential for satellite link designer to take into account rain fade margin accurately before system implementation. Rain rate is the main measured parameter to predict of rain attenuation. Rainfall statistical data measured and recorded in Libya for the period of 30 years are collected from 5 locations. The prediction methods require one minute integration time rain intensity. Therefore, collected data were analyzed and processed to convert into one–minute rain rate cumulative distribution in Libya. The model proposed by ITU-R is used to predict and investigate rain fade based on converted 1-minute rain rate data. Rain fade predicted at two locations are used for performance analysis in terms of link spectral efficiency and throughput. V-band downlink shows that 99.99% availability is possible in all the Southern part stations in Libya at 0.29 bps/Hz spectral efficiency and 20.74 Mbps throughput when 72 MHz transponder band width is used which is not feasible in Northern part. Results of this paper will be a very useful resource to design highly reliable earth-to-satellite communication links in Libya.

  10. Performance Characteristics of Vibration-Controlled Transient Elastography for Evaluation of Non-Alcoholic Fatty Liver Disease. (United States)

    Vuppalanchi, Raj; Siddiqui, Mohammad S; Van Natta, Mark L; Hallinan, Erin; Brandman, Danielle; Kowdley, Kris; Neuschwander-Tetri, Brent A; Loomba, Rohit; Dasarathy, Srinivas; Abdelmalek, Manal; Doo, Edward; Tonascia, James A; Kleiner, David E; Sanyal, Arun J; Chalasani, Naga


    Vibration-controlled transient elastography (VCTE) estimates liver stiffness measurement (LSM) and controlled attenuation parameter (CAP) which are noninvasive assessments of hepatic fibrosis and steatosis respectively. However, prior VCTE studies reported high failure rate in patients with non-alcoholic fatty liver disease (NAFLD). To examine the performance characteristics of Fibroscan 502 Touch with two probes, medium (M+) and extra-large (XL+), in patients with NAFLD in a multicenter setting. A total of 1696 exams were attempted in 992 patients (BMI: 33.6 ± 6.5 kg/m(2) ) with histologically confirmed NAFLD. Simultaneous assessment of LSM and CAP was performed using Fibroscan 502 Touch with an automatic probe selection tool. Testing was conducted twice in patients by either a single operator (88%) or two operators (12%). Failure was defined as the inability to obtain a valid examination. An examination was considered unreliable if LSM IQR/median was >30%. Significant disagreement between two readings was defined as greater than >95% limits of agreement between two readings. A total of 1641 examinations yielded valid results with a failure rate of 3.2% (55/1696). The proportion of unreliable scans for LSM was 2.4%. The proportion of unreliable scans with operator experience in the top quartile (≥ 59 procedures) was significantly lower than lower three quarters combined (1.6% vs.4.7%, p=0.01 by Fisher's Exact test). The significant disagreement between first and second readings for LSM and CAP when obtained back to back was 18% and 11% respectively. VCTE for estimation of LSM and CAP can be successfully deployed in a multicenter setting with low failure (3.2%) and high reliability (>95%) rates and high reproducibility. This article is protected by copyright. All rights reserved. © 2017 by the American Association for the Study of Liver Diseases.

  11. The Impact of Traffic-Induced Bridge Vibration on Rapid Repairing High-Performance Concrete for Bridge Deck Pavement Repairs

    Directory of Open Access Journals (Sweden)

    Wei Wang


    Full Text Available Based on forced vibration tests for high-performance concrete (HPC, the influence of bridge vibration induced by traveling vehicle on compressive strength and durability of HPC has been studied. It is concluded that 1 d and 2 d compressive strength of HPC decreased significantly, and the maximum reduction rate is 9.1%, while 28 d compressive strength of HPC had a slight lower with a 3% maximal drop under the action of two simple harmonic vibrations with 2 Hz, 3 mm amplitude, and 4 Hz, 3 mm amplitude. Moreover, the vibration had a slight effect on the compressive strength of HPC when the simple harmonic vibration had 4 Hz and 1 mm amplitude; it is indicated that the amplitude exerts a more prominent influence on the earlier compressive strength with the comparison of the frequency. In addition, the impact of simple harmonic vibration on durability of HPC can be ignored; this shows the self-healing function of concrete resulting from later hydration reaction. Thus, the research achievements mentioned above can contribute to learning the laws by which bridge vibration affects the properties of concrete and provide technical support for the design and construction of the bridge deck pavement maintenance.

  12. A computational investigation of vibration attenuation of a rigid rotor turning at a variable speed by means of short magnetorheological dampers

    Directory of Open Access Journals (Sweden)

    Zapoměl J.


    Full Text Available Rotors of all rotating machines are always slightly imbalanced. When they rotate, the imbalance induces their lateral vibration and forces that are transmitted via the bearings into the foundations. These phenomena are significant if the rotor accelerates or decelerates and especially if it passes over the critical speeds. The vibration can be reduced if the rotor supports are equipped with damping elements. To achieve optimum performance of the damper, the damping effect must be controllable. At present time, semiactive magnetorheological squeeze film dampers are a subject of intensive research. They work on a principle of squeezing a thin film of magnetorheological liquid. If magnetic field is applied, the magnetorheological liquid starts to flow only if the shear stress between two neighbourhood layers exceeds a limit value which depends on intensity of the magnetic field. Its change enables to control the damping force. In the mathematical models, the magnetorheological liquid is usually considered as Bingham one. Application of the computer modelling method for analysis of rotors supported by rolling element bearings and magnetorheological squeeze film dampers and turning at variable angular speed requires to set up the equations of motion of the rotor and to develop a procedure for calculation of the damping force. Derivation of the equations of motion starts from the first and second impulse theorems. The pressure distribution in the thin lubricating film can be described by a Reynolds equation modified for the case of Bingham liquid. In cavitated areas, it is assumed that pressure of the medium remains constant. The hydraulic force acting on the rotor journal is then obtained by integration of the pressure distribution around the circumference and along the length of the damper. Applicability of the developed procedures was tested by means of computer simulations and influence of the control of the damping force on vibration of the rotor

  13. Estimate of the effect of micro-vibration on the performance of the Algerian satellite (Alsat-1B) imager (United States)

    Serief, Chahira


    Alsat-1B, launched into a 670 km sun-synchronous orbit on board the PSLV launch vehicle from the Sriharikota launch site in India on 26 September 2016, is a medium resolution Earth Observation satellite with a mass of 100 kg. Alsat-1B will be used for agricultural and resource monitoring, disaster management, land use mapping and urban planning. It is based on the SSTL-100 platform, and flies a 24 m multispectral imager and a 12 m panchromatic imager delivering images with a swath width of 140 km. One of the main factors affecting the performance of satellite-borne optical imaging systems is micro-vibration. Micro-vibration is a low level mechanical disturbance inevitably generated from moving parts on a satellite and exceptionally difficult to be controlled by the attitude and orbital control system (AOCS) of a spacecraft. Micro-vibration usually causes problems for optical imaging systems onboard Earth Observation satellites. The major effect of micro-vibration is the excitation of the support structures for the optical elements during imaging operations which can result in severe degradation of image quality by smearing and distortion. Quantitative characterization of image degradation caused by micro-vibration is thus quite useful and important as part of system level analysis which can help preventing micro-vibration influence by proper design and restoring the degraded image. The aim of this work is to provide quantitative estimates of the effect of micro-vibration on the performance of Alsat-1B imager, which may be experienced operationally, in terms of the modulation transfer function (MTF) and based on ground micro-vibration tests results.

  14. Dynamical Performances of a Vibration Absorber for Continuous Structure considering Time-Delay Coupling

    Directory of Open Access Journals (Sweden)

    Xiuting Sun


    Full Text Available The nonlinear effect incurred by time delay in vibration control is investigated in this study via a vibration absorber coupled with a continuous beam structure. The stability of the vibration absorber coupled structure system with time-delay coupling is firstly studied, which provides a general guideline for the potential time delay to be introduced to the system. Then it is shown that there is a specific region for the time delay which can bring bifurcation modes to the dynamic response of the coupling system, and the vibration energy at low frequencies can be transferred or absorbed due to the bifurcation mode and the vibration in the corresponding frequency range is thus suppressed. The nonlinear mechanism of this vibration suppression incurred by the coupling time delay is discussed in detail, which provides a novel and alternative approach to the analysis, design, and control of vibration absorbers in engineering practice.

  15. Determining the optimal whole-body vibration dose-response relationship for muscle performance. (United States)

    Da Silva-Grigoletto, Marzo E; De Hoyo, Moisés; Sañudo, Borja; Carrasco, Luis; García-Manso, Juan M


    Da Silva-Grigoletto, ME, de Hoyo, M, Sañudo, B, Corrales, L, and García-Manso, JM. Determining the optimal whole-body vibration dose-response relationship for muscle performance. J Strength Cond Res 25(12): 3326-3333, 2011-The aim of this investigation was twofold: first, to determine the optimal duration of a single whole-body vibration (WBV) exposure (phase 1) and second to find out the ideal number of sets per intervention to maximize muscle performance (phase 2). All participants were young (age: 19.4 ± 1.6 years), healthy, physically active men. In both studies, a 30-Hz frequency and a 4-mm peak-to-peak displacement were used. In phase 1, subjects (n = 30) underwent 3 sets of different durations (30, 60, and 90 seconds), whereas in phase 2, subjects (n = 27) underwent 3 interventions where the duration remained fixed at 60 seconds, and the number of sets performed (3, 6, or 9) was modified. The recovery time between sets was set at 2 minutes. In all interventions, each set consisted of 1 isometric repetition in a squat position with knees flexed at 100°. Before and after each session, jump height (countermovement jump [CMJ] and squat jump [SJ]) and power output in half squat (90° knee flexion) were assessed. In phase 1, an improvement in jump ability and power output was observed after the 30- and 60-second intervention (p effect for the program of 6 sets (p < 0.05). In conclusion, a WBV intervention consisting of six 60-second sets produces improved muscle performance measured by SJ, CMJ, and power output.

  16. Active vibration control for a smart panel with enhanced acoustic performances (United States)

    Ripamonti, Francesco; Baro, Simone; Molgora, Manuel


    The spread of smart structures has recorded a significant increase during the last decades. Nowadays these solutions are applied in various fields such as aerospace, automotive and civil constructions. This kind of structures was born in the past in order to cope with the high vibrations that every lightweight structure has to face. In order to reduce weight designers usually decide to use very thin and lightweight structures. In the automotive field, for example, a reduced fuel consumption is obtained employing lightweight materials. However, in general a worsening of the vibroacoustic comfort is obtained with undesired vibrations that can be really annoying for passengers and dangerous for the structure itself. This work presents an innovative smart plate that is able to actively vary its dynamic properties, by means of an IMSC control logic, in order to improve the acoustic performances. An investigation about the system response in the high frequency range allowed to assess the behavior in terms of absorption, reflection coefficient and transmission loss.

  17. Passive-performance, analysis, and upgrades of a 1-ton seismic attenuation system (United States)

    Bergmann, G.; Mow-Lowry, C. M.; Adya, V. B.; Bertolini, A.; Hanke, M. M.; Kirchhoff, R.; Köhlenbeck, S. M.; Kühn, G.; Oppermann, P.; Wanner, A.; Westphal, T.; Wöhler, J.; Wu, D. S.; Lück, H.; Strain, K. A.; Danzmann, K.


    The 10 m prototype facility at the Albert-Einstein-institute (AEI) in Hanover, Germany, employs three large seismic attenuation systems to reduce mechanical motion. The AEI seismic-attenuation-system (AEI-SAS) uses mechanical anti-springs in order to achieve resonance frequencies below 0.5 Hz. This system provides passive isolation from ground motion by a factor of about 400 in the horizontal direction at 4 Hz and in the vertical direction at 9 Hz. The presented isolation performance is measured under vacuum conditions using a combination of commercial and custom-made inertial sensors. Detailed analysis of this performance led to the design and implementation of tuned dampers to mitigate the effect of the unavoidable higher order modes of the system. These dampers reduce RMS motion substantially in the frequency range between 10 and 100 Hz in 6 degrees of freedom. The results presented here demonstrate that the AEI-SAS provides substantial passive isolation at all the fundamental mirror-suspension resonances.

  18. Effects Of Whole Body Vibration On Vertical Jump Performance Following Exercise Induced Muscle Damage

    Directory of Open Access Journals (Sweden)

    Nicole C. Dabbs


    Full Text Available Enhancing vertical jump performance is critical for many sports. Following high intensity training, individuals often experience exercise induced muscle damage (EIMD. Many recovery modalities have been tested with conflicting results. The purpose of this investigation was to determine the effect of whole-body vibration (WBV on vertical jump performance following EIMD. 27 females volunteered for 7 sessions and were randomly assigned to a treatment or control group and administered each testing day. Vertical jump performance was assessed via vertical jump height (VJH, peak power output (PPO, rate of force development (RFD, relative ground reaction force (GRFz, and peak activation ratio of the vastus medialis (VM via electromyography (EMG before and after 3 days of EIMD via split squats. Two testing sets were collected each day, consisting of pre measures followed by WBV or control, and then post second measures. A 2x8 (group x time mixed factor analysis of variance (ANOVA was conducted for each variable. No significant interactions or group differences were found in any variable. Significant main effects for time were found in any variable, indicating performance declined following muscle damage. These results indicate that WBV does not aid in muscle recovery or vertical jump performance following EIMD.



    BROEKMANS, Tom; Roelants, Machteld; ALDERS, Geert; FEYS, Peter; THIJS, Herbert; OP 'T EIJNDE, Bert


    Objective To investigate the acute effects of long term whole body vibration on leg muscle performance and functional capacity in persons with multiple sclerosis Design A randomized controlled trial Subjects Twenty five patients with multiple sclerosis (mean age 47 9 +/- 1 9 years Expanded Disability Status Scale 4 3 +/- 0 2) were assigned randomly to whole body vibration training (n = 11) or to a control group (n = 14) Methods The whole body vibration group performed static and dynamic leg s...

  20. Effects of vibration on occupant driving performance under simulated driving conditions. (United States)

    Azizan, Amzar; Fard, M; Azari, Michael F; Jazar, Reza


    Although much research has been devoted to the characterization of the effects of whole-body vibration on seated occupants' comfort, drowsiness induced by vibration has received less attention to date. There are also little validated measurement methods available to quantify whole body vibration-induced drowsiness. Here, the effects of vibration on drowsiness were investigated. Twenty male volunteers were recruited for this experiment. Drowsiness was measured in a driving simulator, before and after 30-min exposure to vibration. Gaussian random vibration, with 1-15 Hz frequency bandwidth was used for excitation. During the driving session, volunteers were required to obey the speed limit of 100 kph and maintain a steady position on the left-hand lane. A deviation in lane position, steering angle variability, and speed deviation were recorded and analysed. Alternatively, volunteers rated their subjective drowsiness by Karolinska Sleepiness Scale (KSS) scores every 5-min. Following 30-min of exposure to vibration, a significant increase of lane deviation, steering angle variability, and KSS scores were observed in all volunteers suggesting the adverse effects of vibration on human alertness level. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Optimal deployment schedule of an active twist rotor for performance enhancement and vibration reduction in high-speed flights

    Directory of Open Access Journals (Sweden)

    Young H. YOU


    Full Text Available The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions. The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic waveform input. An advanced Particle Swarm assisted Genetic Algorithm (PSGA is employed for the optimizer. A rotorcraft Computational Structural Dynamics (CSD code CAMRAD II is used to perform the rotor aeromechanics analysis. A Computation Fluid Dynamics (CFD code is coupled with CSD for verification and some physical insights. The PSGA optimization results are verified against the parameter sweep study performed using the harmonic actuation. The optimum twist schedules according to the performance and/or vibration reduction strategy are obtained and their optimization gains are compared between the actuation cases. A two-phase non-harmonic actuation schedule demonstrates the best outcome in decreasing the power required while a four-phase non-harmonic schedule results in the best vibration reduction as well as the simultaneous reductions in the power required and vibration. The mechanism of reduction to the performance gains is identified illustrating the section airloads, angle-of-attack distribution, and elastic twist deformation predicted by the present approaches.

  2. Enhancement of Energy Harvesting Performance by a Coupled Bluff Splitter Body and PVEH Plate through Vortex Induced Vibration near Resonance

    Directory of Open Access Journals (Sweden)

    Wei Ken Chin


    Full Text Available Inspired by vortex induced vibration energy harvesting development as a new source of renewable energy, a T-shaped design vibration energy harvester is introduced with the aim of enhancing its performance through vortex induced vibration at near resonance conditions. The T-shaped structural model designed consists of a fixed boundary aluminum bluff splitter body coupled with a cantilever piezoelectric vibration energy harvesters (PVEH plate model which is a piezoelectric bimorph plate made of a brass plate sandwiched between 2 lead zirconate titanate (PZT plates. A 3-dimensional Fluid-Structure Interaction simulation analysis is carried out with Reynolds Stress Turbulence Model under wind speed of 7, 10, 12, 14, 16, 18, 19, 20, 22.5, and 25 m/s. The results showed that with 19 m/s wind speed, the model generates 75.758 Hz of vortex frequency near to the structural model’s natural frequency of 76.9 Hz. Resonance lock-in therefore occurred, generating a maximum displacement amplitude of 2.09 mm or a 49.76% increment relatively in vibrational amplitude. Under the effect of resonance at the PVEH plate’s fundamental natural frequency, it is able to generate the largest normalized power of 13.44 mW/cm3g2.

  3. Small and inconsistent effects of whole body vibration on athletic performance: a systematic review and meta-analysis. (United States)

    Hortobágyi, Tibor; Lesinski, Melanie; Fernandez-Del-Olmo, Miguel; Granacher, Urs


    We quantified the acute and chronic effects of whole body vibration on athletic performance or its proxy measures in competitive and/or elite athletes. Systematic literature review and meta-analysis. Whole body vibration combined with exercise had an overall 0.3 % acute effect on maximal voluntary leg force (-6.4 %, effect size = -0.43, 1 study), leg power (4.7 %, weighted mean effect size = 0.30, 6 studies), flexibility (4.6 %, effect size = -0.12 to 0.22, 2 studies), and athletic performance (-1.9 %, weighted mean effect size = 0.26, 6 studies) in 191 (103 male, 88 female) athletes representing eight sports (overall effect size = 0.28). Whole body vibration combined with exercise had an overall 10.2 % chronic effect on maximal voluntary leg force (14.6 %, weighted mean effect size = 0.44, 5 studies), leg power (10.7 %, weighted mean effect size = 0.42, 9 studies), flexibility (16.5 %, effect size = 0.57 to 0.61, 2 studies), and athletic performance (-1.2 %, weighted mean effect size = 0.45, 5 studies) in 437 (169 male, 268 female) athletes (overall effect size = 0.44). Whole body vibration has small and inconsistent acute and chronic effects on athletic performance in competitive and/or elite athletes. These findings lead to the hypothesis that neuromuscular adaptive processes following whole body vibration are not specific enough to enhance athletic performance. Thus, other types of exercise programs (e.g., resistance training) are recommended if the goal is to improve athletic performance.

  4. Diagnostic performance of controlled attenuation parameter for predicting steatosis grade in chronic hepatitis B. (United States)

    Cardoso, Ana C; Beaugrand, Michel; de Ledinghen, Victor; Douvin, Catherine; Poupon, Raoul; Trinchet, Jean-Claude; Ziol, Marianne; Bedossa, Pierre; Marcellin, Patrick


    A novel controlled attenuation parameter (CAP) using the signals acquired by the FibroScan® has been developed as a method for evaluating steatosis. The aim of this study is to assess the performance of the CAP for the detection and quantification of steatosis in patients with chronic hepatitis B (CHB). 136 subjects with CHB underwent liver biopsy and FibroScan® within 60 days. CAP was evaluated retrospectively using raw FibroScan® data. Steatosis was graded as follows: S0 (steatosis CAP correlated with steatosis (τ = 0.38, P CAP were: 0.82 (0.73-0.92), 0.82 (0.69-0.95), and 0.97 (0.84-1.00) for ≥ S1, ≥ S2 and S3 steatosis, respectively. In conclusión CAP is a novel, accurate non-invasive tool and may be suitable for detecting and quantifying steatosis in CHB patients.

  5. Innovation in Active Vibration Control Strategy of Intelligent Structures

    Directory of Open Access Journals (Sweden)

    A. Moutsopoulou


    Full Text Available Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper presents sufficiently a recognizable advance in knowledge of active vibration control in intelligent structures.

  6. Whole-body vibration applied during upper body exercise improves performance. (United States)

    Marín, Pedro J; Herrero, Azael J; Milton, John G; Hazell, Tom J; García-López, David


    Whole-body vibration (WBV) training has exercisers perform static and dynamic resistance training exercises on a ground-based platform. Exposure to WBV exposure has demonstrated benefits and no effect on lower body strength, power, and performance. The aim of this study was to determine if WBV exposure (50 Hz, 2.51 mm) has any potentiating effects postexercise by measuring the kinematic variables of a set of upper body elbow-extensor exercise (70% one-repetition maximum [1RM]) to volitional exhaustion. Sixteen recreationally active students (12 male and 4 female) performed 3 different experimental conditions on separate days. Each condition had the subjects perform 1 set of elbow-extension exercise to fatigue with 1 of 3 WBV treatments: WBV simultaneously during the set (AE); 60 seconds after application of WBV for 30 seconds (RE); and no WBV (CTRL). Kinematic parameters of each repetition were monitored by linking a rotary encoder to the highest load plate. The mean velocity and acceleration throughout the set and perceived exertion were analyzed. A significant increase (p < 0.05) was observed in the mean velocity for the whole set in the AE condition vs. the CTRL condition. The mean acceleration was significantly higher (p < 0.05) in the AE condition in comparison with RE (increased by 45.3%) and CTRL (increased by 50.4%) conditions. The positive effect induced by WBV on upper-limb performance is only achieved when the stimulus is applied during the exercise. However, WBV applied 60 seconds before upper body exercise results in no benefit.


    Zmijewski, P.; Jimenez-Olmedo, J.M.; Jové-Tossi, M.A.; Martínez-Carbonell, A.; Suárez-Llorca, C.; Andreu-Cabrera, E.


    The primary aim of this study was to examine the effects of 6-week strength training with whole body vibration (WBV) on leg strength and jumping performance in volleyball and beach volleyball players. Twenty-three sub-elite male volleyball (VB; n=12) and beach volleyball players (BVB; n=11) aged 21.2±3.0 years were divided into two groups and subjected to 6 weeks of strength training (three one-hour sessions per week): (I) 12 players (6 VB and 6 BVB players) underwent training with WBV (30-40 Hz, 1.7-2.5 mm, 3.0-5.7 g), and (II) 11 players (6 VB and 5 BVB players) underwent traditional strength training. Squat jump (SJ) and countermovement squat jump (CMJ) measurements by the Ergo Tester contact platform and maximum leg press test (1RM) were conducted. Three-factor (2 time x 2 WBV use x 2 discipline) analysis of variance for SJ, CMJ and 1RM revealed a significant time main effect (pvolleyball and beach volleyball players increases leg strength more and leads to greater improvement in jump performance than traditional strength training, but greater improvements can be expected in beach volleyball players than in volleyball players. PMID:25187676

  8. Whole-body vibration training effect on physical performance and obesity in mice. (United States)

    Huang, Chi-Chang; Tseng, Tzu-Ling; Huang, Wen-Ching; Chung, Yi-Hsiu; Chuang, Hsiao-Li; Wu, Jyh-Horng


    The purpose of this study was to verify the beneficial effects of whole-body vibration (WBV) training on exercise performance, physical fatigue and obesity in mice with obesity induced by a high-fat diet (HFD). Male C57BL/6 mice were randomly divided into two groups: normal group (n=6), fed standard diet (control), and experimental group (n=18), fed a HFD. After 4-week induction, followed by 6-week WBV of 5 days per week, the 18 obese mice were divided into 3 groups (n=6 per group): HFD with sedentary control (HFD), HFD with WBV at relatively low-intensity (5.6 Hz, 0.13 g) (HFD+VL) or high-intensity (13 Hz, 0.68 g) (HFD+VH). A trend analysis revealed that WBV increased the grip strength in mice. WBV also dose-dependently decreased serum lactate, ammonia and CK levels and increased glucose level after the swimming test. WBV slightly decreased final body weight and dose-dependently decreased weights of epididymal, retroperitoneal and perirenal fat pads and fasting serum levels of alanine aminotransferase, CK, glucose, total cholesterol and triacylglycerol. Therefore, WBV could improve exercise performance and fatigue and prevent fat accumulation and obesity-associated biochemical alterations in obese mice. It may be an effective intervention for health promotion and prevention of HFD-induced obesity.

  9. Harvesting microalgal biomass using a magnetically induced membrane vibration (MMV) system: filtration performance and energy consumption. (United States)

    Bilad, M R; Discart, V; Vandamme, D; Foubert, I; Muylaert, K; Vankelecom, Ivo F J


    This study was performed to investigate the effectiveness of submerged microfiltration to harvest both a marine diatom Phaeodactylum tricornutum and a Chlorella vulgaris in a recently developed magnetically induced membrane vibrating (MMV) system. We assess the filtration performance by conducting the improved flux step method (IFM), fed-batch concentration filtrations and membrane fouling autopsy using two lab-made membranes with different porosity. The full-scale energy consumption was also estimated. Overall results suggest that the MMV offers a good fouling control and the process was proven to be economically attractive. By combining the membrane filtration (15× concentration) with centrifugation to reach a final concentration of 25% w/v, the energy consumption to harvest P. tricornutum and C. vulgaris was, respectively, as low as 0.84 and 0.77kWh/m(3), corresponding to 1.46 and 1.39 kWh/kg of the harvested biomass. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Actuator design for vibration assisted machining of high performance materials with ultrasonically modulated cutting speed (United States)

    Rinck, Philipp M.; Sitzberger, Sebastian; Zaeh, Michael F.


    In vibration assisted machining, an additional high-frequency oscillation is superimposed on the kinematics of the conventional machining process. This generates oscillations on the cutting edge in the range of a few micrometers, thereby causing a high-frequency change in the cutting speed or the feed. Consequently, a reduction of cutting forces, an increase of the tool life as well as an improvement of the workpiece quality can be achieved. In milling and grinding it has been shown that these effects are already partially present in the case of a vibration excitation in axial direction relative to the workpiece, which is perpendicular to the cutting direction. Further improvements of the process results can be achieved by superimposing a vibration in cutting direction and thus modifying the cutting speed at high frequency. The presented work shows the design of an ultrasonic actuator that enables vibration-assisted milling and grinding with ultrasonically modulated cutting speed. The actuator system superimposes a longitudinal torsional ultrasonic oscillation to the milling or grinding tool. It uses a bolt clamped Langevin transducer and a helically slotted horn, which degenerates the longitudinal vibration into a combined longitudinal torsional (L-T) vibration at the output surface. A finite element analysis is used to determine the vibration resonance frequency and mode shapes to maximize the torsional output. Afterwards, the simulation has been experimentally validated.

  11. Smoked marijuana attenuates performance and mood disruptions during simulated night shift work. (United States)

    Keith, Diana R; Gunderson, Erik W; Haney, Margaret; Foltin, Richard W; Hart, Carl L


    Individuals who work nonstandard schedules, such as rotating or night shifts, are more susceptible to workplace injuries, performance decrements, and reduced productivity. This population is also almost twice as likely to use illicit drugs as individuals working a standard day shift. The purpose of this study was to examine the effects of smoked marijuana on performance, mood, and sleep during simulated shift work. Ten experienced marijuana smokers completed this 23-day, within-participant residential study. They smoked a single marijuana cigarette (0, 1.9, 3.56% Δ 9 -THC) one hour after waking for three consecutive days under two shift conditions: day shift and night shift. Shifts alternated three times during the study, and shift conditions were separated by an 'off' day. When participants smoked placebo cigarettes, psychomotor performance and subjective-effect ratings were altered during the night shift compared to the day shift: performance (e.g., vigilance) and a few subjective ratings were decreased (e.g., "Self-Confident"), whereas other ratings were increased (e.g., "Tired"). Objective and subjective measures of sleep were also disrupted, but to a lesser extent. Marijuana attenuated some performance, mood, and sleep disruptions: participants performed better on vigilance tasks, reported being less miserable and tired and sleep a greater number of minutes. Limited negative effects of marijuana were noted. These data demonstrate that abrupt shift changes produce performance, mood, and sleep decrements during night shift work and that smoked marijuana containing low to moderate Δ 9 -THC concentrations can offset some of these effects in frequent marijuana smokers. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Coronary stent occlusion: reverse attenuation gradient sign observed at computed tomography angiography improves diagnostic performance

    Energy Technology Data Exchange (ETDEWEB)

    Li, Minghua; Zhang, Jiayin [Shanghai Jiao Tong University Affiliated Sixth People' s Hospital, Department of Radiology, Shanghai (China); Zhang, Qingyong; Pan, Jingwei; Lu, Zhigang; Wei, Meng [Shanghai Jiao Tong University Affiliated Sixth People' s Hospital, Department of Cardiology, Shanghai (China)


    To evaluate the incidence and diagnostic performance of reverse attenuation gradient (RAG) sign in patients with coronary stent occlusion. We retrospectively included patients with suspected restenosis who underwent both coronary computed tomography angiography (CCTA) and invasive coronary angiography (ICA) within 2 weeks. Stent occlusion at CCTA was defined as (1) complete contrast filling defect of large calibre stents (at least 3 mm), or (2) presence of RAG sign in patients with small calibre stents (less than 3 mm) or (3) presence of RAG sign in patients with non-diagnostic image quality of stents. The diagnostic performance of RAG sign was further assessed by comparison to ICA results. A total of 162 patients with 231 implanted stents were included. ICA confirmed stent occlusion in 59 patients (99 stents). RAG sign was present in 59.3 % (35/59) of all stent occlusions. As shown by patient-based analysis, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of our diagnostic criteria for detection of stent occlusion were 79.7 % (47/59), 100 % (103/103), 100 % (47/47) and 89.6 % (103/115) respectively. Superior diagnostic performance was confirmed by receiver operating characteristic (ROC) analysis with an area under the curve of 0.898. RAG sign observed at CCTA in patients with coronary stenting represents reverse collateral flow distal to stents and is highly specific to indicate stent occlusion. (orig.)

  13. Various performance-enhancing effects from the same intensity of whole-body vibration training

    Directory of Open Access Journals (Sweden)

    Paohung Chung


    Conclusion: All frequency and amplitude settings in the 8-week whole-body vibration training increased muscle strength, but different settings resulted in various neuromuscular adaptations despite the same intensity.

  14. Whole-Body Vibration Training and Its Application to Age-Related Performance Decrements: An Exploratory Analysis. (United States)

    Hawkey, Adam; Griffiths, Katie; Babraj, John; Cobley, James N


    Middle age is associated with a pronounced decline in power and flexibility. Whilst whole-body vibration training (WBVT) improves performance in a range of populations, whether WBVT can improve muscle power and flexibility in a middle-aged population is not known. The present study aimed to determine the influence of 5 weeks progressive WBVT in middle-aged (45-55 years) and younger (20-30 years) recreationally active females. Participants in each age group were randomly allocated to an intervention (WBVT) or control group. The WBVT groups trained for 5 weeks on a vibration platform, while the control groups performed identical exercises, with no vibration. Prior to, and after, the 5-week study vertical countermovement jump (VCMJ) and range of motion (ROM) performance were measured. WBVT significantly (p = 0.001) improved VCMJ performance when compared to the control groups. This improvement was significantly (p = 0.001) greater in the middle-aged compared with the younger WBVT group. WBVT significantly (p = 0.001) improved ROM irrespective of age. Taken together, these results suggest that WBVT can off-set age related performance decrements, which has therapeutic implications for musculoskeletal aging. Therefore, WBVT could be undertaken to minimise age-related performance deterioration in middle-aged female populations.


    Directory of Open Access Journals (Sweden)

    J.A. Pérez-Turpin


    Full Text Available The primary aim of this study was to examine the effects of 6-week strength training with whole body vibration (WBV on leg strength and jumping performance in volleyball and beach volleyball players. Twenty-three sub-elite male volleyball (VB; n=12 and beach volleyball players (BVB; n=11 aged 21.2±3.0 years were divided into two groups and subjected to 6 weeks of strength training (three one-hour sessions per week: (I 12 players (6 VB and 6 BVB players underwent training with WBV (30-40 Hz, 1.7-2.5 mm, 3.0-5.7 g, and (II 11 players (6 VB and 5 BVB players underwent traditional strength training. Squat jump (SJ and countermovement squat jump (CMJ measurements by the Ergo Tester contact platform and maximum leg press test (1RM were conducted. Three-factor (2 time x 2 WBV use x 2 discipline analysis of variance for SJ, CMJ and 1RM revealed a significant time main effect (p<0.001, a WBV use effect (p<0.001 and a discipline effect (p<0.001. Significantly greater improvements in the SJ (p<0.001 and CMJ (p<0.001 and in 1RM (p<0.001 were found in the WBV training groups than in traditional training groups. Significant 3-way interaction effects (training, WBV use, discipline kind were also found for SJ, CMJ and 1RM (p=0.001, p<0.001, p=0.001, respectively. It can be concluded that implementation of 6-week WBV training in routine practice in volleyball and beach volleyball players increases leg strength more and leads to greater improvement in jump performance than traditional strength training, but greater improvements can be expected in beach volleyball players than in volleyball players.

  16. Effect of whole-body vibration training on body composition, exercise performance and biochemical responses in middle-aged mice. (United States)

    Lin, Ching-I; Huang, Wen-Ching; Chen, Wen-Chyuan; Kan, Nai-Wen; Wei, Li; Chiu, Yen-Shuo; Huang, Chi-Chang


    Whole-body vibration (WBV) is a well-known light-resistance exercise by automatic adaptations to rapid and repeated oscillations from a vibrating platform, which is also a simple and convenient exercise for older adults. However, the potential benefits of WBV on aging-associated changes in body composition, exercise performance, and fatigue are currently unclear. The objective of the study is to investigate the beneficial effects of WBV training on body composition, exercise performance, and physical fatigue-related and biochemical responses in middle-aged mice. In total, 24 male C57BL/6 mice aged 15 months old were randomly divided into 3 groups (n=8 per group): sedentary control (SC), relatively low-frequency WBV (5.6 Hz, 2 mm, 0.13 g) (LV), and relatively high-frequency WBV (13 Hz, 2 mm, 0.68 g) (HV). Mice in the LV and HV groups were placed inside a vibration platform and vibrated at different frequencies and fixed amplitude (2 mm) for 15 min, 5 days/week for 4 weeks. Exercise performance, core temperature and anti-fatigue function were evaluated by forelimb grip strength and levels of serum lactate, ammonia, glucose, and creatine kinase (CK) after a 15-min swimming exercise, as were changes in body composition and biochemical variables at the end of the experiment. Relative muscle and brown adipose tissue weight (%) was significantly higher for the HV than SC mice, but relative liver weight (%) was lower. On trend analysis, WBV increased grip strength, aerobic endurance and core temperature in mice. As well, serum lactate, ammonia and CK levels were dose-dependently decreased with vibration frequency after the swimming test. Fasting serum levels of albumin and total protein were increased and serum levels of alkaline phosphatase and creatinine decreased dose-dependently with vibration frequency. Moreover, WBV training improved the age-related abnormal morphology of skeletal muscle, liver and kidney tissues. Therefore, it could improve exercise performance and

  17. Performance of improved magnetostrictive vibrational power generator, simple and high power output for practical applications (United States)

    Ueno, Toshiyuki


    Vibration based power generation technology is utilized effectively in various fields. Author has invented novel vibrational power generation device using magnetostrictive material. The device is based on parallel beam structure consisting of a rod of iron-gallium alloy wound with coil and yoke accompanied with permanent magnet. When bending force is applied on the tip of the device, the magnetization inside the rod varies with induced stress due to the inverse magnetostrictive effect. In vibration, the time variation of the magnetization generates voltage on the wound coil. The magnetostrictive type is advantageous over conventional such using piezoelectric or moving magnet types in high efficiency and high robustness, and low electrical impedance. Here, author has established device configuration, simple, rigid, and high power output endurable for practical applications. In addition, the improved device is lower cost using less volume of Fe-Ga and permanent magnet compared to our conventional, and its assembly by soldering is easy and fast suitable for mass production. Average power of 3 mW/cm3 under resonant vibration of 212 Hz and 1.2 G was obtained in miniature prototype using Fe-Ga rod of 2 × 0.5× 7 mm3. Furthermore, the damping effect was observed, which demonstrates high energy conversion of the generator.

  18. An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine

    Directory of Open Access Journals (Sweden)

    Xuanlin Peng


    Full Text Available In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration based on field experiments and a finite element method (FEM is presented. It is found that the resonance between the Kármán vortex and the stay vane is the main cause for the undesired vibration. Then, we focus on establishing an intelligent optimization model of the stay vane’s trailing edge profile. To this end, an approach combining factorial experiments, extreme learning machine (ELM and particle swarm optimization (PSO is implemented. Three kinds of improved profiles of the stay vane are proposed and compared. Finally, the profile with a Donaldson trailing edge is adopted as the best solution for the stay vane, and verifications such as computational fluid dynamics (CFD simulations, structural analysis and fatigue analysis are performed to validate the optimized geometry.

  19. Investigation of the performances of PZT vs rare earth (BaLaTiO3 vibration based energy harvester

    Directory of Open Access Journals (Sweden)

    Pak Nehemiah


    Full Text Available This study proposes the investigation of two piezoelectric material namely PZT and Lanthanum Doped Barium Titanate (BaLaTiO3 performance as a vibration based energy harvester. The piezoelectric material when applied mechanical stress or strain produces electricity through the piezoelectric effect. The vibration energy would exude mechanical energy and thus apply mechanical force on the energy harvester. The energy harvester would be designed and simulated using the piezoelectric material individually. The studied outputs are divided to frequency response, the load dependence, and the acceleration dependence whereby measurement are observed and taken at maximum power output. The simulation is done using the cantilevers design which employs d31 type of constants. Three different simulations to study the dependence of output power on the resonant frequency response, load and acceleration have found that material that exhibit highest power generation was the BaLaTiO3.

  20. GOES-R Active Vibration Damping Controller Design, Implementation, and On-Orbit Performance (United States)

    Clapp, Brian R.; Weigl, Harald J.; Goodzeit, Neil E.; Carter, Delano R.; Rood, Timothy J.


    GOES-R series spacecraft feature a number of flexible appendages with modal frequencies below 3.0 Hz which, if excited by spacecraft disturbances, can be sources of undesirable jitter perturbing spacecraft pointing. In order to meet GOES-R pointing stability requirements, the spacecraft flight software implements an Active Vibration Damping (AVD) rate control law which acts in parallel with the nadir point attitude control law. The AVD controller commands spacecraft reaction wheel actuators based upon Inertial Measurement Unit (IMU) inputs to provide additional damping for spacecraft structural modes below 3.0 Hz which vary with solar wing angle. A GOES-R spacecraft dynamics and attitude control system identified model is constructed from pseudo-random reaction wheel torque commands and IMU angular rate response measurements occurring over a single orbit during spacecraft post-deployment activities. The identified Fourier model is computed on the ground, uplinked to the spacecraft flight computer, and the AVD controller filter coefficients are periodically computed on-board from the Fourier model. Consequently, the AVD controller formulation is based not upon pre-launch simulation model estimates but upon on-orbit nadir point attitude control and time-varying spacecraft dynamics. GOES-R high-fidelity time domain simulation results herein demonstrate the accuracy of the AVD identified Fourier model relative to the pre-launch spacecraft dynamics and control truth model. The AVD controller on-board the GOES-16 spacecraft achieves more than a ten-fold increase in structural mode damping of the fundamental solar wing mode while maintaining controller stability margins and ensuring that the nadir point attitude control bandwidth does not fall below 0.02 Hz. On-orbit GOES-16 spacecraft appendage modal frequencies and damping ratios are quantified based upon the AVD system identification, and the increase in modal damping provided by the AVD controller for each structural


    National Research Council Canada - National Science Library

    Ahlborg, Lotta; Andersson, Christina; Julin, Per


    Objective: The aim of this study was to evaluate the effect on spasticity, muscle strength and motor performance after 8 weeks of whole-body vibration training compared with resistance training in adults with cerebral palsy. Methods...

  2. Analysis of Single-Mode Fiber Link Performance for Attenuation in Long-Haul Optical Networks (United States)

    Kaur, Karamjit; Singh, Hardeep


    In the past decades, optical fiber has been widely used in communication system owing to low transmission losses, large information carrying capacity, small size, immunity to electrical interference and increased signal security. Focusing on increasing the network transmission capacity, control on the quality of transmission was the field that withdraws attention of research community. For this reason, fiber losses and their compensation remain the important design issue. In the present work, an effort is put in to design a system capable of doing error analysis of system for power losses taking place in the presence of attenuation effect. Attenuation is one of the important phenomena that determine the maximum possible distance between a transmitter and receiver or quantity and position of amplifiers and repeaters in optical networks. The mathematical model equations are obtained representing variation trends of bit error rate BER and Q-value with varying attenuation, which has been verified by different wavelength sources and network conditions.

  3. Experimental study on the performance of a variable optical attenuator using polymer dispersed liquid crystal. (United States)

    Nabil, Ghada; Ho, Wing Fat; Chan, Hau Ping


    We applied polymer dispersed liquid crystal (PDLC) as the cladding material in a polymer-based variable optical attenuator. Three polymer inverted channel waveguides were fabricated, two with PDLC upper cladding (aligned PDLC and nonaligned PDLC) and one with aligned liquid crystal upper cladding. Upon operation, the waveguides with aligned upper claddings show relatively lower threshold and cutoff voltages compared to those with nonaligned PDLC cladding. But the waveguide with nonaligned PDLC upper cladding shows lower polarization dependence and a higher attenuation range of 39 and 41.37 dB for TM and TE modes, respectively, over a tuning field strength of 0.9 V/μm.

  4. Ultrasonic vibration imposed on nanoparticle-based ZnO film improves the performance of the ensuing perovskite solar cell (United States)

    Miao, Yihe; Du, Peng; Wang, Zhiyu; Chen, Qianli; Eslamian, Morteza


    This work focuses on the development of nearly annealing-free ZnO-based perovskite solar cells (PSCs), suitable for low-cost manufacturing of PSCs on flexible substrates. To this end, thin film of ZnO nanoparticles is employed as the electron transporting layer (ETL), because of its low-temperature solution-processability and high electron mobility. In order to remove the structural and surface defects, ultrasonic vibration is imposed on the substrate of the as-spun wet ZnO films for a short duration of 3 min. It is shown that the ultrasonic excitation bridges the ZnO nanoparticles (cold sintering), and brings about significant improvement in the ZnO film nanostructure and functionality. In addition, ethyl acetate (EA), as an emerging volatile anti-solvent, is employed to deposit the methylammonium (MA) lead halide perovskite thin film atop the ZnO ETL, in order to prepare perovskite layers that only need an annealing time of 30 s. The ZnO-based PSCs, with a simple structure and free of additional treatments, except for the ultrasonic vibration, exhibit a promising performance with a power conversion efficiency (PCE) of over 11%, 40% higher than that of the control device. The ultrasonic vibration treatment is facile, low-cost, environmentally friendly, and compatible with the scalable coating and printing techniques, such as spray and blade coating.

  5. Performance testing of diesel engines using vibrational-acoustical diagnostic methods

    Energy Technology Data Exchange (ETDEWEB)

    Maack, H.H.; Neumann, G.


    Vibroacoustic condition monitoring is based on the measurement, processing and analysis of the solid-borne and airborne vibration signals emanating from a machine. Several assemblies belonging to diesel engines have a characteristic signal structure induced by impact excitation. The author proceeds from a generalised condition monitoring process to discuss the problem of the origin, transmission, measurement and analysis of vibroacoustic signals from diesel engines and presents a procedure based on a combination of frequency analysis in the temporary elimination of signal components.

  6. Effectiveness of Different Rest Intervals Following Whole-Body Vibration on Vertical Jump Performance between College Athletes and Recreationally Trained Females

    Directory of Open Access Journals (Sweden)

    Nicole C. Dabbs


    Full Text Available The purpose of this study was to evaluate the effect of different rest intervals following whole-body vibration on counter-movement vertical jump performance. Sixteen females, eight recreationally trained and eight varsity athletes volunteered to participate in four testing visits separated by 24 h. Visit one acted as a familiarization visit where subjects were introduced to the counter-movement vertical jump and whole-body vibration protocols. Visits 2–4 contained 2 randomized conditions. Whole-body vibration was administered in four bouts of 30 s with 30 s rest between bouts. During whole-body vibration subjects performed a quarter squat every 5 s, simulating a counter-movement vertical jump. Whole-body vibration was followed by three counter-movement vertical jumps with five different rest intervals between the vibration exposure and jumping. For a control condition, subjects performed squats with no whole-body vibration. There was a significant (p < 0.05 main effect for time for vertical jump height, peak power output, and relative ground reaction forces, where a majority of individuals max jump from all whole-body vibration conditions was greater than the control condition. There were significant (p < 0.05 group differences, showing that varsity athletes had a greater vertical jump height and peak power output compared to recreationally trained females. There were no significant (p > 0.05 group differences for relative ground reaction forces. Practitioners and/or strength and conditioning coaches may utilize whole-body vibration to enhance acute counter-movement vertical jump performance after identifying individuals optimal rest time in order to maximize the potentiating effects.

  7. Controlled attenuation parameter for non-invasive assessment of hepatic steatosis: does etiology affect performance? (United States)

    Kumar, Manoj; Rastogi, Archana; Singh, Tarandeep; Behari, Chhagan; Gupta, Ekta; Garg, Hitendra; Kumar, Ramesh; Bhatia, Vikram; Sarin, Shiv K


    Hepatic steatosis is an important parameter to assess in chronic liver disease patients. The controlled attenuation parameter (CAP) assesses liver steatosis using transient elastography. To determine the accuracy of CAP for evaluation of hepatic steatosis in chronic hepatitis B virus (CHBV)-infected, chronic hepatitis C virus (CHCV)-infected, and non-alcoholic fatty liver disease (NAFLD) patients and to determine the influence of etiology on the diagnostic accuracy of CAP. One hundred forty-six CHBV patients, 108 CHCV-infected patients and 63 patients with NAFLD, who underwent both liver biopsy and successful CAP measurements within the study period, were assessed. Area under the receiver operating characteristics was used to evaluate performance of CAP for diagnosing steatosis compared with biopsy. Multivariate analysis found that CAP correlated with body mass index (odds ratio, 95% confidence interval = 4.09 [1.2-6.8] for CHBV; 4.7 [1.1-8.4] for CHCV, and 16.2 [9.1-24.5] for NAFLD patients respectively) and hepatic steatosis score on biopsy (odds ratio, 95% confidence interval = 30.7 [19.2-42.2] for CHBV; 24.2 [11.5-37.3] for CHCV, and 21.8 [10.1-45.0] for NAFLD patients respectively). Area under the receiver operating characteristics for CAP was 0.683 (0.601-0.757) for steatosis (S) ≥ 6%, 0.793 (0.718-0.856) for S > 33%, and 0.841 (0.771-0.896) for S > 66% respectively for CHBV-infected patients. There was no difference in accuracy of CAP for assessing liver fat among CHBV, CHCV, and NAFLD patients. CAP is a novel, non-invasive tool that can detect and quantify steatosis accurately among CHBV, CHCV, and NAFLD patients, the accuracy being similar for all the three groups of patients. © 2013 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.

  8. A Novel Dual–Parallelogram Passive Rocking Vibration Isolator: A Theoretical Investigation and Experiment

    Directory of Open Access Journals (Sweden)

    Shuai Wang


    Full Text Available Vibration isolators with quasi-zero stiffness (QZS perform well for low- or ultra-low-frequency vibration isolation. This paper proposes a novel dual-parallelogram passive rocking vibration isolator with QZS that could effectively attenuate in-plane disturbances with low-frequency vibration. First, a kinematic model of the proposed vibration isolator was established and four linear spring configuration schemes were developed to implement the QZS. Next, an optimal scheme with good high-static-low-dynamic stiffness (HSLDS performance was obtained through comparison and analysis, and used as a focus for the QZS model. Subsequently, a dynamic model-based Lagrangian equation that considered the spring stiffness and damping and the influence of the payload gravity center on the vibration isolation system was developed, and an average approach was used to analyze the vibration transmissibility. Finally, the prototype and test system were constructed. A comparison of the simulation and experimental results showed that this novel passive rocking vibration isolator could bolster a heavy payload. Experimentally, the vibration amplitude decreased by 53% and 86% under harmonic disturbances of 0.08 Hz and 0.35 Hz, respectively, suggesting the great practical applicability of this presented vibration isolator.

  9. Vibration analysis of cryocoolers (United States)

    Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira; Koyama, Tomohiro; Li, Rui


    The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas.

  10. Vibration analysis of cryocoolers

    Energy Technology Data Exchange (ETDEWEB)

    Tomaru, Takayuki; Suzuki, Toshikazu; Haruyama, Tomiyoshi; Shintomi, Takakazu; Yamamoto, Akira [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki (Japan); Koyama, Tomohiro; Rui Li [Sumitomo Heavy Industries Ltd., Tokyo (Japan)


    The vibrations of Gifford-McMahon (GM) and pulse-tube (PT) cryocoolers were measured and analyzed. The vibrations of the cold-stage and cold-head were measured separately to investigate their vibration mechanisms. The measurements were performed while maintaining the thermal conditions of the cryocoolers at a steady state. We found that the vibration of the cold-head for the 4 K PT cryocooler was two orders of magnitude smaller than that of the 4 K GM cryocooler. On the other hand, the vibration of the cold-stages for both cryocoolers was of the same order of magnitude. From a spectral analysis of the vibrations and a simulation, we concluded that the vibration of the cold-stage is caused by an elastic deformation of the pulse tubes (or cylinders) due to the pressure oscillation of the working gas. (Author)

  11. The Effects of Vibration Frequencies on Physical, Perceptual and Cognitive Performance (United States)


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

  12. Prediction Performance of Blackout and Plasma Attenuation in Atmospheric Reentry Demonstrator Mission


    Takahashi, Yusuke; Yamada, Kazuhiko; Abe, Takashi


    A numerical simulation model that combines the plasma ows and electromagnetic waves around a reentry vehicle during atmospheric reentry was developed to evaluate the radio frequency blackout and plasma attenuation. The physical properties of the plasma ow in the shock layer and wake region were obtained using a computational uid dynamics technique. The electromagnetic waves were expressed using a frequency- dependent nite-difference time-domain method with the plasma ...

  13. Joint Service Aircrew Mask (JSAM) - Strategic Aircraft (SA): Noise Attenuation Performance (United States)


    at the entrance of both ear canals. Subjects were required to wear foam earplugs during all measurements to reduce the noise exposure. The...miniature microphones rested on top of the foam earplug at the entrance to the ear canal. 115 dB overall SPL was generated and three objective measurements...noise attenuation requirement would be to add communication earplugs under the headset and JSAM-SA. Another recommended solution would be to

  14. Attenuation of social interaction-associated ultrasonic vocalizations and spatial working memory performance in rats exposed to chronic unpredictable stress. (United States)

    Riaz, Muhammad S; Bohlen, Martin O; Gunter, Barak W; Quentin, Henry; Stockmeier, Craig A; Paul, Ian A


    Exposure to unpredictable chronic mild stress (CUS) is a commonly used protocol in rats that is reported to evoke antidepressant-reversible behaviors such as loss of preference for a sweetened water solution which is taken as an analog of the anhedonia seen in major depression. However, the induction of anhedonic-like behavior by chronic mild stress, gauged by an animal's preference for sucrose solution, is not fully reproducible and consistent across laboratories. In this study, we compared a widely used behavioral marker of anhedonia - the sucrose preference test, with another phenotypic marker of emotional valence, social interaction-associated ultrasonic vocalizations as well as a marker of an anxiety-like phenotype, novelty-suppressed feeding, and cognitive performance in the eight arm radial maze task in adult male Sprague-Dawley rats. Chronic four-week exposure to unpredictable mild stressors resulted in 1) attenuation of social interaction-associated ultrasonic vocalizations 2) attenuation of spatial memory performance on the radial arm maze 3) attenuation of body weight gain and 4) increased latency to feed in a novelty-suppressed feeding task. However, chronic exposure to CUS did not result in any significant change in sucrose preference at one-week and three-week intervals. Our results argue for the utility of ultrasonic vocalizations in a social interaction context as a comparable alternative or adjunct to the sucrose preference test in determining the efficacy of CUS to generate an anhedonic-like phenotypic state. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. A method based on reflection theory to test the attenuation performance of an absorption coat to 8mm waves (United States)

    Wang, Xuanyu


    A testing method has been set up to evaluate the attenuation performance of an absorption coat to 8mm waves, which is based on a set of detecting system included by an 8mm wave emitter, a millimeter power meter, a point to point collimator and a reflecting plate. The power meter was aimed at the 8 mm wave emitter along the reflection optical path instead of the direction observation between incident and reflected millimeter wave. Some Al, Fe and aluminum alloy sample plates were made and painted by the dope which was complexed with chopped carbon fibers. A naked metal plate was first used to adjust the transmission path of the millimeter wave. Then the power meter was adjusted to phase locking after preheating, and the millimeter wave power was sampled as the background value. Then the other painted plates were tested under the same conditions. When the concentration of chopped carbon fibers is 0.5mg/ml and the thickness of the absorption coat is 0.5mm, the attenuation percentages of Al, Fe and aluminum alloy painted plates respectively is 54.29%, 58.31% and 41.12%. By the result, the reflection testing method may be widely used to measure the reflection capacity or attenuation performance of various surfaces to millimeter waves.

  16. The effects of suspension particle size on the performance of air-jet, ultrasonic and vibrating-mesh nebulisers. (United States)

    Najlah, Mohammad; Parveen, Ishrat; Alhnan, Mohamed Albed; Ahmed, Waqar; Faheem, Ahmed; Phoenix, David A; Taylor, Kevin M G; Elhissi, Abdelbary


    Using latex microspheres as model suspensions, the influence of suspension particle size (1, 4.5 and 10 μm) on the properties of aerosols produced using Pari LC Sprint (air-jet), Polygreen (ultrasonic), Aeroneb Pro (actively vibrating-mesh) and Omron MicroAir NE-U22 (passively vibrating-mesh) nebulisers was investigated. The performance of the Pari nebuliser was independent of latex spheres particle size. For both Polygreen and Aeroneb Pro nebulizers, total aerosol output increased when the size of latex spheres increased, with highest fine particle fraction (FPF) values being recorded. However, following nebulisation of 1 or 4.5 μm suspensions with the Polygreen device, no particles were detected in the aerosols deposited in a two-stage impinger, suggesting that the aerosols generated from this device consisted mainly of the continuous phase while the dispersed microspheres were excluded and remained in the nebuliser. The Omron nebuliser efficiently nebulised the 1 μm latex spheres, with high output rate and no particle aggregation. However, this device functioned inefficiently when delivering 4.5 or 10 μm suspensions, which was attributed to the mild vibrations of its mesh and/or the blockage of the mesh apertures by the microspheres. The Aeroneb Pro fragmented latex spheres into smaller particles, but uncontrolled aggregation occurred upon nebulisation. This study has shown that the design of the nebuliser influenced the aerosol properties using latex spheres as model suspensions. Moreover, for the recently marketed mesh nebulisers, the performance of the Aeroneb Pro device was less dependent on particle size of the suspension compared with the Omron MicroAir nebuliser. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. ZnO thin film piezoelectric MEMS vibration energy harvesters with two piezoelectric elements for higher output performance. (United States)

    Wang, Peihong; Du, Hejun


    Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s(2). By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration.

  18. Tuning the performance of a natural treatment process using metagenomics for improved trace organic chemical attenuation

    KAUST Repository

    Drewes, Jorg


    By utilizing high-throughput sequencing and metagenomics, this study revealed how the microbial community characteristics including composition, diversity, as well as functional genes in managed aquifer recharge (MAR) systems can be tuned to enhance removal of trace organic chemicals of emerging concern (CECs). Increasing the humic content of the primary substrate resulted in higher microbial diversity. Lower concentrations and a higher humic content of the primary substrate promoted the attenuation of biodegradable CECs in laboratory and field MAR systems. Metagenomic results indicated that the metabolic capabilities of xenobiotic biodegradation were significantly promoted for the microbiome under carbon-starving conditions. © IWA Publishing 2014.

  19. Comparison of whole-body vibration exercise and plyometric exercise to improve isokinetic muscular strength, jumping performance and balance of female volleyball players (United States)

    Kim, Yong-Youn; Park, Si-Eun


    [Purpose] The purpose of this study was to assess the effect of whole-body vibration exercise and plyometric exercise on female volleyball players. [Subjects and Methods] Subjects were randomly allocated to two exercise groups (whole-body vibration exercise group and plyometric exercise group). The exercise was conducted three times each week for 8 weeks. Isokinetic muscular strength, jumping performance, and balance were measured before starting the exercise and after finishing the 8 weeks of exercise. [Results] Measurements of isokinetic muscular strength revealed that the whole-body vibration exercise group showed significant increase after the exercise. However, the plyometric exercise group had no significant increase in lumbar flexion, extension, and knee flexion. Measurements of vertical jumping revealed that, the whole-body vibration exercise group had no significant increase after the exercise. However, the plyometric exercise group showed significant increase. Measurements of balance revealed that, the whole-body vibration exercise group showed significant increase. However, the plyometric exercise group showed no significant increase. [Conclusion] Although both whole-body vibration and plyometric exercises are effective intervention methods, the two methods have different effects on the improvement of isokinetic muscular strength, jumping performance, and balance of female volleyball players. PMID:27942136

  20. The Effects of Whole Body Vibration Training and Creatine Supplementation on Lower Extremity Performance and Balance in Elderly Males

    Directory of Open Access Journals (Sweden)

    Mostafa Rahimi


    Full Text Available Objectives: The purpose of this study was to investigate the effects of whole body vibration training (WBVT and creatine (Cr supplementation on lower extremity performance and balance in elderly males. Methods & Materials: In this semi-experimental study, twenty two eligible males from the members of an elderly daycare center with more than 60 years of age were enrolled and were divided into three groups randomly, WBVT+Cr(n=7, WBVT+Pgroup (n=7, and control group (n=8. In WBVT+Cr and WBVT+P groups exercises were performed on the whole body vibration device for 10 days with 30-35 Hz intensity and 5 mm amplitude. The WBVT+Cr group consumed 20g/day Crsupplement for the first 5 days followed by 5g/days for the next 5 days of protocol. The WBVT+P group consumed dexterous. The control group neither did any exercise nor consumed any supplement during the protocol. Static balance by standing time on one leg, dynamic balance by TUG test and lower extremity performance by 30-meter walking test, sit and stand test and tandem gait test weremeasured. Paired sample t-test and one way ANOVAwere used for data analysis (α=0.05. Results: Our results showed that dynamic balance, lower body performance in 30- meter walking and tandem gait improved in experimental groups. However, ANOVA did not show any significant increase in static balance (P=0.514, dynamic balance (P=0.153, lower body performance in 30-meter walking test (P=0.339, sit and stand test (P=0.578 and tandem gait (P=0.151. Conclusion: In conclusion, it seems that WBVT plus Cr supplementation improves some of the motor fitness factors in elderly males during a short time.

  1. Effect of whole-body vibration on neuromuscular performance and body composition for females 65 years and older: a randomized-controlled trial. (United States)

    von Stengel, S; Kemmler, W; Engelke, K; Kalender, W A


    We examined whether the effect of multipurpose exercise can be enhanced by whole-body vibration (WBV). One hundred and fifty-one post-menopausal women (68.5 ± 3.1 years) were randomly assigned to three groups: (1) a training group (TG); (2) training including vibration (VTG); and (3) a wellness control group (CG). TG and VTG performed the same training program twice weekly (60 min), consisting of aerobic and strength exercises, with the only difference that leg strength exercises (15 min) were performed with (VTG) or without (TG) vibration. CG performed a low-intensity "wellness" program. At baseline and after 18 months, body composition was determined using dual-X-ray-absorptiometry. Maximum isometric strength was determined for the legs and the trunk region. Leg power was measured by countermovement jumps using a force-measuring plate. In the TG lean body mass, total body fat, and abdominal fat were favorably affected, but no additive effects were generated by the vibration stimulus. However, concerning muscle strength and power, there was a tendency in favor of the VTG. Only vibration training resulted in a significant increase of leg and trunk flexion strength compared with CG. In summary, WBV embedded in a multipurpose exercise program showed minor additive effects on body composition and neuromuscular performance. © 2010 John Wiley & Sons A/S.

  2. Understanding how the placement of an asymmetric vibration damping tool within drilling while underreaming can influence performance and reliability

    Energy Technology Data Exchange (ETDEWEB)

    Kabbara, Alan; McCarthy, John; Burnett, Timm; Forster, Ian [National Oilwell Varco Downhole Ltd. (NOV), Houston, TX (United States)


    This paper describes the work, on test rigs and full-scale drilling rigs, carried out with respect to placement of an Asymmetric Vibration Damping Tool (AVDT) within drilling while under reaming operations. An AVDT, by virtue of the forward synchronous motion imposed on the drill string, offers benefits in minimizing down hole vibration-related tool failures and therefore maximizing rate of penetration (ROP). Of interest in using the AVDT is the tendency to minimize stick slip by means of the parasitic torque it generates. This is of particular importance during under reaming operations. While under reaming, stick slip can result in low (ROP) and potentially an increased incidence of down hole tool failures. The use of an AVDT in these operations has been shown to significantly reduce stick slip. However, due to the forward synchronous motion caused by the AVDT, there is the potential to cause eccentric wear to the Bottom Hole Assembly (BHA) components in the vicinity of the AVDT. If allowed to progress, this eccentric wear can cause a reduction in down hole tool life and drilling performance. Eliminating eccentric wear would be beneficial in reducing repair costs, extending component life and further improving drilling performance. To minimize eccentric wear and maximize drilling performance, the placement of the AVDT within the BHA is critical. This paper describes how the placement of intermediate stabilizers between the AVDT and the under reamer can minimize eccentric wear to the under reamer and the adjacent drill string due to the forward synchronous whirl induced by the AVDT. This approach allows the full benefits of the AVDT to be recognized while reducing the potentially damaging effects of eccentric wear to other BHA components. The work has drawn upon small-scale rig testing, full-scale testing at the Ullrigg test facility in Norway and from real-world drilling and under reaming operations in the USA. (author)

  3. An Investigation of Acoustic Attenuation Performance of Silencers with Mean Flow Based on Three-Dimensional Numerical Simulation

    Directory of Open Access Journals (Sweden)

    Wei Fan


    Full Text Available Transmission loss (TL is often used to evaluate the acoustic attenuation performance of a silencer. In this work, a three-dimensional (3D finite element method (FEM is employed to calculate the TL of some representative silencers, namely, circular expansion chamber silencer and straight-through perforated pipe silencer. In order to account for the effect of mean flow that exists inside the silencer, the 3D FEM is used in conjunction with the Computational Fluid Dynamics (CFD simulation of the flow field. More concretely, the 3D mean flow field is computed by firstly using CFD, and then the obtained mean flow data are imported to an acoustic solution undertaken using FEM. The data transfer between the two steps is accomplished by mesh mapping. The results presented demonstrate good agreement between present TL predictions and previously published experimental and numerical works. Also, the details of the flow inside the silencers may be studied. Furthermore, the effect of mean flow velocity on acoustic attenuation performance of the silencers is investigated. It is concluded that for the studied silencers, in general, increasing flow velocity increases the TL and decreases the resonance peaks.

  4. Performance enhancement of a rotational energy harvester utilizing wind-induced vibration of an inclined stay cable (United States)

    Kim, In-Ho; Jang, Seon-Jun; Jung, Hyung-Jo


    In this paper, an innovative strategy for improving the performance of a recently developed rotational energy harvester is proposed. Its performance can be considerably enhanced by replacing the electromagnetic induction part, consisting of moving permanent magnets and a fixed solenoid coil, with a moving mass and a rotational generator (i.e., an electric motor). The proposed system is easily tuned to the natural frequency of a target structure using the position change of a proof mass. Owing to the high efficiency of the rotational generator, the device can more effectively harness electrical energy from the wind-induced vibration of a stay cable. Also, this new configuration makes the device more compact and geometrically tunable. In order to validate the effectiveness of the new configuration, a series of laboratory and field tests are carried out with the prototype of the proposed device, which is designed and fabricated based on the dynamic characteristics of the vibration of a stay cable installed in an in-service cable-stayed bridge. From the field test, it is observed that the normalized output power of the proposed system is 35.67 mW (m s-2)-2, while that of the original device is just 5.47 mW (m s-2)-2. These results show that the proposed device generates much more electrical energy than the original device. Moreover, it is verified that the proposed device can generate sufficient electricity to power a wireless sensor node placed on a cable under gentle-moderate wind conditions.

  5. Changes in muscle cross-sectional area, muscle force, and jump performance during 6 weeks of progressive whole-body vibration combined with progressive, high intensity resistance training (United States)

    Rosenberger, A.; Beijer, Å.; Johannes, B.; Schoenau, E.; Mester, J.; Rittweger, J.; Zange, J.


    Objectives: We hypothesized that progressive whole-body vibration (WBV) superimposed to progressive high intensity resistance training has greater effects on muscle cross-sectional area (CSA), muscle force of leg muscles, and jump performance than progressive high intensity resistance training alone. Methods: Two groups of healthy male subjects performed either 6 weeks of Resistive Vibration Exercise (RVE, squats and heel raises with WBV, n=13) or Resistive Exercise (RE, squats and heel raises without WBV, n=13). Squats under RVE required indispensable weight loading on the forefoot to damp harmful vibrations to the head. Time, intervention, and interaction effects were analyzed. Results: After 6 weeks of training, knee extensor CSA, isometric knee extension force, and counter movement jump height increased equally in both groups (time effect, Ptraining effects than RE only in plantar flexor muscles. RVE seems to be suitable in professional sports with a special focus on calf muscles. PMID:28574410

  6. Gel performance in rheology and profile control under low-frequency vibration: coupling application of physical and chemical EOR techniques. (United States)

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


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

  7. Adding whole body vibration to preconditioning exercise increases subsequent on-ice sprint performance in ice-hockey players. (United States)

    Rønnestad, Bent R; Slettaløkken, Gunnar; Ellefsen, Stian


    The phenomenon postactivation potentiation can possibly be used to acutely improve sprint performance. The purpose of this study was to investigate the effect of body-loaded half-squats with added whole body vibration (WBV) on subsequent 20 m on-ice sprint performance. Fifteen male ice-hockey players performed 4 test sessions on separate days and in a randomized order. Two of this test sessions were with WBV and 2 were with noWBV and the best sprint time was used to determine effectiveness. Each test session included preconditioning 30 seconds half-squat exercise, 2 of which were supplemented with 50 Hz WBV at a amplitude of 3 mm. One minute after the cessation of the preconditioning exercise, the 20 m sprint test was performed. Intermediate time was sampled after 10 m. Preconditioning exercise performed with 50 Hz WBV resulted in superior 10 m and 20 m sprint performance compared to preconditioning exercise performed without WBV (1.84 6 0.10 seconds vs. 1.89 6 0.10 seconds and 3.14 6 0.13 vs. 3.17 6 0.13 seconds, respectively, p # 0.01). There was no difference between the protocols in perceived well-being of the legs before the warm-up or after the warm up (p = 0.3). However, there was an improved well-being in the legs immediately after the preconditioning exercise with WBV (p , 0.05). In conclusion, preconditioning exercise performed with WBV at 50 Hz seems to enhance on-ice sprint performance in ice-hockey players. This suggests that coaches can incorporate such exercise into the preparation to specific sprint training to improve the quality of the training.

  8. The Effect of Whole Body Vibration Training and Detraining Periods on Neuromuscular Performance in Male Older People

    Directory of Open Access Journals (Sweden)

    Ali Abbasi


    Full Text Available Objectives: This study aimed to evaluatethe the effect of eight weeks whole body vibration training (WBVT and detraining periods on neuromuscular performance male healthy older people. Methods & Materials: Thirty male subjects (70±9.6 years old were randomly allocated into two groups of WBVT and control (n=15 per group. Timed Up & Go and 5-Chair stand tests, as indicators of neuromuscular performance in older subjects, were taken as pretest and posttest and also after four, six, and eight weeks of detraining. Results: Results of Repeated-measure ANOVA and one-way ANOVA showed that neuromuscular performance improved significantly in WBVT group (P<0.05. There were also significant differences between posttest and six and eight weeks of detraining periods in WBVTgroup (P<0.05. Conclusion: WBVT could affect neuromuscular performance in healthy subjects and reduce the probability of falling among them. However, the effects of this training are not persistent, goes back to the early levels after six weeks of detraining. Hence, it is possible that WBVT can be recommended as a safe balance training to older people.

  9. Evaluating vibration performance of a subsea pump module by full-scale testing and numerical modelling

    NARCIS (Netherlands)

    Beek, P.J.G. van; Pereboom, H.P.; Slot, H.J.


    Prior to subsea installation, a subsea system has to be tested to verify whether it performs in accordance with specifications and component specific performance evaluation criteria. It is important to verify that the assembled components work in accordance with the assumptions and design criteria

  10. Effect of stochastic resonance whole body vibration on functional performance in the frail elderly: A pilot study. (United States)

    Kessler, Jessica; Radlinger, Lorenz; Baur, Heiner; Rogan, Slavko


    The aim of this pilot study was to evaluate the feasibility and the effect size of a four-week stochastic resonance whole body vibration (SR-WBV) intervention on functional performance and strength in frail elderly individuals. Twenty-seven participants have been recruited and randomly distributed in an intervention group (IG) and a sham group (SG). Primary outcomes were feasibility objectives like recruitment, compliance and safety. Secondary outcomes were short physical performance battery (SPPB), isometric maximum voluntary contraction (IMVC) and isometric rate of force development (IRFD). The intervention was feasible and safe. Furthermore it showed significant effects (p=0.035) and medium effect size (0.43) within the IG in SPPB. SR-WBV training over four weeks with frail elderly individuals is a safe intervention method. The compliance was good and SR-WBV intervention seems to improve functional performance. Further research over a longer time frame for the strength measurements (IMVC and IRFD) is needed to detect potential intervention effects in the force measurements as well. Clinical Trial register: NTC01704976. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  11. The Vigilance Decrement in Executive Function Is Attenuated When Individual Chronotypes Perform at Their Optimal Time of Day (United States)

    Lara, Tania; Madrid, Juan Antonio; Correa, Ángel


    Time of day modulates our cognitive functions, especially those related to executive control, such as the ability to inhibit inappropriate responses. However, the impact of individual differences in time of day preferences (i.e. morning vs. evening chronotype) had not been considered by most studies. It was also unclear whether the vigilance decrement (impaired performance with time on task) depends on both time of day and chronotype. In this study, morning-type and evening-type participants performed a task measuring vigilance and response inhibition (the Sustained Attention to Response Task, SART) in morning and evening sessions. The results showed that the vigilance decrement in inhibitory performance was accentuated at non-optimal as compared to optimal times of day. In the morning-type group, inhibition performance decreased linearly with time on task only in the evening session, whereas in the morning session it remained more accurate and stable over time. In contrast, inhibition performance in the evening-type group showed a linear vigilance decrement in the morning session, whereas in the evening session the vigilance decrement was attenuated, following a quadratic trend. Our findings imply that the negative effects of time on task in executive control can be prevented by scheduling cognitive tasks at the optimal time of day according to specific circadian profiles of individuals. Therefore, time of day and chronotype influences should be considered in research and clinical studies as well as real-word situations demanding executive control for response inhibition. PMID:24586404

  12. Vibration isolation performance of an ultra-low frequency folded pendulum resonator (United States)

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


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

  13. Performance Analysis of Wind-Induced Piezoelectric Vibration Bimorph Cantilever for Rotating Machinery


    Gongbo Zhou; Houlian Wang; Zhencai Zhu; Linghua Huang; Wei Li


    Harvesting the energy contained in the running environment of rotating machinery would be a good way to supplement energy to the wireless sensor. In this paper, we take piezoelectric bimorph cantilever beam with parallel connection mode as energy collector and analyze the factors which can influence the generation performance. First, a modal response theory model is built. Second, the static analysis, modal analysis, and piezoelectric harmonic response analysis of the wind-induced piezoelectr...

  14. Selective loads periodization attenuates biochemical disturbances and enhances performance in female futsal players during competitive season

    Directory of Open Access Journals (Sweden)

    Ricelli Endrigo Ruppel da Rocha


    Full Text Available This study evaluated the effect of selective loads periodization on physical performance and biochemical parameters in professional female futsal players during competitive season. Twelve elite female futsal players from Kindermann team (Brazil participated in the study. Variables of physical performance and erythrogram, leukogram, plasma cortisol, plasma immunoglobulin A (IgA in the beginning of the preparatory period (PP, in the competitive period (CP and in the final competitive period (FCP were evaluated. Using selective loads periodization, all variables of physical performance increased (p < .01 during CP and were maintained during FCP (p < .05. White blood cells did not modify during CP and the increase of FCP in 28% remained within normal ranges. Plasma cortisol also increased during CP (p < .01 and was within the normal ranges during FCP. Plasma IgA also was within the normal ranges during CP and FCP. Selective loads periodization is adequate and attends the requirements of the sport during competitive season in female futsal players.

  15. Fluid Replacement Attenuates Physiological Strain Resulting From Mild Hypohydration Without Impacting Cognitive Performance. (United States)

    Wittbrodt, Matthew T; Millard-Stafford, Mindy; Sherman, Ross A; Cheatham, Christopher C


    The impact of mild hypohydration on physiological responses and cognitive performance following exercise-heat stress (EHS) were examined compared with conditions when fluids were ingested ad libitum (AL) or replaced to match sweat losses (FR). Twelve unacclimatized, recreationally-active men (22.2 ± 2.4 y) completed 50 min cycling (60%VO2peak) in the heat (32°C; 65% RH) under three conditions: no fluid (NF), AL, and FR. Before and after EHS, a cognitive battery was completed: Trail making, perceptual vigilance, pattern comparison, match-to-sample, and letter-digit recognition tests. Hypohydration during NF was greater compared with AL and FR (NF: -1.5 ± 0.6; AL: -0.3 ± 0.8; FR: -0.1 ± 0.3% body mass loss) resulting in higher core temperature (by 0.4, 0.5 °C), heart rate (by 13 and 15 b·min-1), and physiological strain (by 1.3, 1.5) at the end of EHS compared with AL and FR, respectively. Cognitive performance (response time and accuracy) was not altered by fluid condition; however, mean response time improved (p < .05) for letter-digit recognition (by 56.7 ± 85.8 ms or 3.8%; p < .05) and pattern comparison (by 80.6 ± 57.4 ms or 7.1%; p < .001), but mean accuracy decreased in trail making (by 1.2 ± 1.4%; p = .01) after EHS (across all conditions). For recreational athletes, fluid intake effectively mitigated physiological strain induced by mild hypohydration; however, mild hypohydration resulting from EHS elicited no adverse changes in cognitive performance.

  16. Seismic attenuation performance of the first prototype of a geometric anti-spring filter

    CERN Document Server

    Cella, G; Sannibale, V; Tariq, H; Viboud, N; Takamori, A


    Next generation gravitational wave detectors, such as an advanced LIGO, will generally require improved sensitivity at low frequency. One of the principal challenges for low-frequency sensitivity is isolation from seismic motion. A mechanical seismic isolation filter specifically studied for the next generation of the LIGO detectors, based on a geometric anti-spring concept, has been developed with the aim to provide thermal noise limited sensitivity to frequencies of 10 Hz. The design and the performance of the isolation filter, mainly for the vertical degree of freedom are discussed.

  17. Seismic attenuation performance of the first prototype of a geometric anti-spring filter

    Energy Technology Data Exchange (ETDEWEB)

    Cella, G.; DeSalvo, R.; Sannibale, V. E-mail:; Tariq, H.; Viboud, N.; Takamori, A


    Next generation gravitational wave detectors, such as an advanced LIGO, will generally require improved sensitivity at low frequency. One of the principal challenges for low-frequency sensitivity is isolation from seismic motion. A mechanical seismic isolation filter specifically studied for the next generation of the LIGO detectors, based on a geometric anti-spring concept, has been developed with the aim to provide thermal noise limited sensitivity to frequencies of 10 Hz. The design and the performance of the isolation filter, mainly for the vertical degree of freedom are discussed.

  18. Effect of whole-body vibration on muscle strength, spasticity, and motor performance in spastic diplegic cerebral palsy children

    Directory of Open Access Journals (Sweden)

    Marwa M. Ibrahim


    Conclusion: The obtained results suggest that 12-weeks’ intervention of whole-body vibration training can increase knee extensors strength and decrease spasticity with beneficial effects on walking speed and motor development in spastic diplegic CP children.

  19. Linear static structural and vibration analysis on high-performance computers (United States)

    Baddourah, M. A.; Storaasli, O. O.; Bostic, S. W.


    Parallel computers offer the oppurtunity to significantly reduce the computation time necessary to analyze large-scale aerospace structures. This paper presents algorithms developed for and implemented on massively-parallel computers hereafter referred to as Scalable High-Performance Computers (SHPC), for the most computationally intensive tasks involved in structural analysis, namely, generation and assembly of system matrices, solution of systems of equations and calculation of the eigenvalues and eigenvectors. Results on SHPC are presented for large-scale structural problems (i.e. models for High-Speed Civil Transport). The goal of this research is to develop a new, efficient technique which extends structural analysis to SHPC and makes large-scale structural analyses tractable.

  20. Nonlinear vibration absorption for a flexible arm via a virtual vibration absorber (United States)

    Bian, Yushu; Gao, Zhihui


    A semi-active vibration absorption method is put forward to attenuate nonlinear vibration of a flexible arm based on the internal resonance. To maintain the 2:1 internal resonance condition and the desirable damping characteristic, a virtual vibration absorber is suggested. It is mathematically equivalent to a vibration absorber but its frequency and damping coefficients can be readily adjusted by simple control algorithms, thereby replacing those hard-to-implement mechanical designs. Through theoretical analyses and numerical simulations, it is proven that the internal resonance can be successfully established for the flexible arm, and the vibrational energy of flexible arm can be transferred to and dissipated by the virtual vibration absorber. Finally, experimental results are presented to validate the theoretical predictions. Since the proposed method absorbs rather than suppresses vibrational energy of the primary system, it is more convenient to reduce strong vibration than conventional active vibration suppression methods based on smart material actuators with limited energy output. Furthermore, since it aims to establish an internal vibrational energy transfer channel from the primary system to the vibration absorber rather than directly respond to external excitations, it is especially applicable for attenuating nonlinear vibration excited by unpredictable excitations.

  1. Performance Analysis of Wind-Induced Piezoelectric Vibration Bimorph Cantilever for Rotating Machinery

    Directory of Open Access Journals (Sweden)

    Gongbo Zhou


    Full Text Available Harvesting the energy contained in the running environment of rotating machinery would be a good way to supplement energy to the wireless sensor. In this paper, we take piezoelectric bimorph cantilever beam with parallel connection mode as energy collector and analyze the factors which can influence the generation performance. First, a modal response theory model is built. Second, the static analysis, modal analysis, and piezoelectric harmonic response analysis of the wind-induced piezoelectric bimorph cantilever beam are given in detail. Finally, an experiment is also conducted. The results show that wind-induced piezoelectric bimorph cantilever beam has low resonant frequency and stable output under the first modal mode and can achieve the maximum output voltage under the resonant condition. The output voltage increases with the increase of the length and width of wind-induced piezoelectric bimorph cantilever beam, but the latter increasing amplitude is relatively smaller. In addition, the output voltage decreases with the increase of the thickness and the ratio of metal substrate to piezoelectric patches thickness. The experiment showed that the voltage amplitude generated by the piezoelectric bimorph cantilever beam can reach the value simulated in ANSYS, which is suitable for actual working conditions.

  2. Testing and performance of a new friction damper for seismic vibration control (United States)

    Martínez, Carlos A.; Curadelli, Oscar


    In the last two decades, great efforts were carried out to reduce the seismic demand on structures through the concept of energy dissipation instead of increasing the stiffness and strength. Several devices based on different energy dissipation principles have been developed and implemented worldwide, however, most of the dissipation devices are usually installed using diagonal braces, which entail certain drawbacks on apertures for circulation, lighting or ventilation and architectural or functional requirements often preclude this type of installations. In this work, a conceptual development of a novel energy dissipation device, called Multiple Friction Damper (MFD), is proposed and examined. To verify its characteristics and performance, the MFD was implemented on a single storey steel frame experimental model and tested under different conditions of normal force and real time acceleration records. Experimental results demonstrated that the new MFD constitutes an effective and reliable alternative to control the structural response in terms of displacement and acceleration. A mathematical formulation based on the Wen's model reflecting the nonlinear behaviour of the device is also presented.

  3. Development of an active isolation mat based on dielectric elastomer stack actuators for mechanical vibration cancellation (United States)

    Karsten, Roman; Flittner, Klaus; Haus, Henry; Schlaak, Helmut F.


    This paper describes the development of an active isolation mat for cancelation of vibrations on sensitive devices with a mass of up to 500 gram. Vertical disturbing vibrations are attenuated actively while horizontal vibrations are damped passively. The dimensions of the investigated mat are 140 × 140 × 20 mm. The mat contains 5 dielectric elastomer stack actuators (DESA). The design and the optimization of active isolation mat are realized by ANSYS FEM software. The best performance shows a DESA with air cushion mounted on its circumference. Within the mounting encased air increases static and reduces dynamic stiffness. Experimental results show that vibrations with amplitudes up to 200 μm can be actively eliminated.

  4. Bio-inspired heterogeneous composites for broadband vibration mitigation (United States)

    Chen, Yanyu; Wang, Lifeng


    Structural biological materials have developed heterogeneous and hierarchical architectures that are responsible for the outstanding performance to provide protection against environmental threats including static and dynamic loading. Inspired by this observation, this research aims to develop new material and structural concepts for broadband vibration mitigation. The proposed composite materials possess a two-layered heterogeneous architecture where both layers consist of high-volume platelet-shape reinforcements and low-volume matrix, similar to the well-known “brick and mortar” microstructure of biological composites. Using finite element method, we numerically demonstrated that broadband wave attenuation zones can be achieved by tailoring the geometric features of the heterogeneous architecture. We reveal that the resulting broadband attenuation zones are gained by directly superimposing the attenuation zones in each constituent layer. This mechanism is further confirmed by the investigation into the phonon dispersion relation of each layer. Importantly, the broadband wave attenuation capability will be maintained when the mineral platelet orientation is locally manipulated, yet a contrast between the mineral platelet concentrations of the two constituent layers is essential. The findings of this work will provide new opportunities to design heterogeneous composites for broadband vibration mitigation and impact resistance under mechanically challenging environmental conditions.

  5. Seismic Performance and Ice-Induced Vibration Control of Offshore Platform Structures Based on the ISO-PFD-SMA Brace System

    Directory of Open Access Journals (Sweden)

    Jigang Zhang


    Full Text Available Pall-typed frictional damper (PFD has higher capacity of energy dissipation, whereas shape memory alloy (SMA has excellent superelastic performance. Therefore, combining PFD and SMA together as a brace system has a great prospect in vibration control of structures. This paper investigates the performance of offshore platform with three structural configurations including the SMA brace system, the ISO-SMA (where ISO stands for isolation brace system, and the ISO-PFD-SMA brace system, which are subjected to seismic and ice-induced excitations. In this study, PFD-SMA brace system is installed on the isolation layer of jacket platform, which is under earthquake excitations and ice loading. Then, the reduction of vibration is evaluated by using ANSYS program. The results show that the PFD-SMA brace system is useful in reducing the seismic response and ice-induced response of offshore platform structures; meanwhile, it also demonstrates excellent energy dissipation and hysteretic behavior.

  6. Comparison of the performance of different DFT methods in the calculations of the molecular structure and vibration spectra of serotonin (5-hydroxytryptamine, 5-HT) (United States)

    Yang, Yue; Gao, Hongwei


    Serotonin (5-hydroxytryptamine, 5-HT) is a monoamine neurotransmitter which plays an important role in treating acute or clinical stress. The comparative performance of different density functional theory (DFT) methods at various basis sets in predicting the molecular structure and vibration spectra of serotonin was reported. The calculation results of different methods including mPW1PW91, HCTH, SVWN, PBEPBE, B3PW91 and B3LYP with various basis sets including LANL2DZ, SDD, LANL2MB, 6-31G, 6-311++G and 6-311+G* were compared with the experimental data. It is remarkable that the SVWN/6-311++G and SVWN/6-311+G* levels afford the best quality to predict the structure of serotonin. The results also indicate that PBEPBE/LANL2DZ level show better performance in the vibration spectra prediction of serotonin than other DFT methods.

  7. Incorporating a disturbance observer with direct velocity feedback for control of human-induced vibrations (United States)

    Nyawako, Donald; Reynolds, Paul; Hudson, Emma


    Feedback control strategies are desirable for disturbance rejection of human-induced vibrations in civil engineering structures as human walking forces cannot easily be measured. In relation to human-induced vibration control studies, most past researches have focused on floors and footbridges and the widely used linear controller implemented in the trials has been the direct velocity feedback (DVF) scheme. With appropriate compensation to enhance its robustness, it has been shown to be effective at damping out the problematic modes of vibration of the structures in which the active vibration control systems have been implemented. The work presented here introduces a disturbance observer (DOB) that is used with an outer-loop DVF controller. Results of analytical studies presented in this work based on the dynamic properties of a walkway bridge structure demonstrate the potential of this approach for enhancing the vibration mitigation performance offered by a purely DVF controller. For example, estimates of controlled frequency response functions indicate improved attenuation of vibration around the dominant frequency of the walkway bridge structure as well as at higher resonant frequencies. Controlled responses from three synthesized walking excitation forces on a walkway bridge structure model show that the inclusion of the disturbance observer with an outer loop DVF has potential to improve on the vibration mitigation performance by about 3.5% at resonance and 6-10% off-resonance. These are realised with hard constraints being imposed on the low frequency actuator displacements.

  8. Hybrid Vibration Control under Broadband Excitation and Variable Temperature Using Viscoelastic Neutralizer and Adaptive Feedforward Approach

    Directory of Open Access Journals (Sweden)

    João C. O. Marra


    Full Text Available Vibratory phenomena have always surrounded human life. The need for more knowledge and domain of such phenomena increases more and more, especially in the modern society where the human-machine integration becomes closer day after day. In that context, this work deals with the development and practical implementation of a hybrid (passive-active/adaptive vibration control system over a metallic beam excited by a broadband signal and under variable temperature, between 5 and 35°C. Since temperature variations affect directly and considerably the performance of the passive control system, composed of a viscoelastic dynamic vibration neutralizer (also called a viscoelastic dynamic vibration absorber, the associative strategy of using an active-adaptive vibration control system (based on a feedforward approach with the use of the FXLMS algorithm working together with the passive one has shown to be a good option to compensate the neutralizer loss of performance and generally maintain the extended overall level of vibration control. As an additional gain, the association of both vibration control systems (passive and active-adaptive has improved the attenuation of vibration levels. Some key steps matured over years of research on this experimental setup are presented in this paper.

  9. Pretreatment with curcumin attenuates anxiety while strengthens memory performance after one short stress experience in male rats. (United States)

    Haider, Saida; Naqvi, Fizza; Batool, Zehra; Tabassum, Saiqa; Sadir, Sadia; Liaquat, Laraib; Naqvi, Faizan; Zuberi, Nudrat Anwer; Shakeel, Hina; Perveen, Tahira


    It is observed that memories are more strengthened in a stressful condition. Studies have also demonstrated an association between stressful events and the onset of depression and anxiety. Considering the nootropic, anxiolytic and antidepressant-like properties of curcumin in various experimental approaches, we appraised the beneficial effects of this herb on acute immobilization stress-induced behavioral and neurochemical alterations. Rats in test group were administrated with curcumin (200mg/kg/day), dissolved in neutral oil, for 1 week. Both control and curcumin-treated rats were divided into unstressed and stressed groups. Rats in the stressed group were subjected to immobilization stress for 2h. After stress, the animals were subjected to behavioral tests. Immobilization stress induced an anxiogenic behavior in rats subjected to elevated plus maze test (EPM). Locomotor activity was also significantly increased following the acute immobilization stress. Pre-administration of curcumin prevented the stress-induced behavioral deficits. Highest memory performance was observed in stressed rats that were pre-treated with curcumin in Morris water maze (MWM). Brain malondialdehyde (MDA) levels, catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), and acetylcholinesterase (AChE) activities were also estimated. Present study suggests a role of antioxidant enzymes in the attenuation of acute stress induced anxiety by curcumin. The findings therefore suggest that supplementation of curcumin may be beneficial in the treatment of acute stress induced anxiety and enhancement of memory function. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Impact of skin capsular distance on the performance of controlled attenuation parameter in patients with chronic liver disease. (United States)

    Shen, Feng; Zheng, Rui-Dan; Shi, Jun-Ping; Mi, Yu-Qiang; Chen, Guo-Feng; Hu, Xiqi; Liu, Yong-Gang; Wang, Xiao-Ying; Pan, Qin; Chen, Guang-Yu; Chen, Jian-Neng; Xu, Liang; Zhang, Rui-Nan; Xu, Lei-Ming; Fan, Jian-Gao


    Controlled attenuation parameter (CAP) is a non-invasive method for evaluating hepatic steatosis. However, larger skin capsular distance (SCD) can affect the accuracy. The aim of this study was to investigate the impact of SCD on the diagnostic performance of CAP and liver stiffness measurement (LSM). Of 101 patients with non-alcoholic fatty liver disease (NAFLD) and 280 patients with chronic hepatitis B (CHB) who underwent liver biopsy were prospectively recruited. CAP, LSM and SCD were performed using FibroScan with M probe. The areas under receiver operating characteristics curves (AUROCs) were calculated to determine the diagnostic efficacy. The optimal thresholds were defined by the maximum Youden index. SCD (B 30.34, P CAP by multivariate analysis. The AUROCs were slightly higher for SCD 33% (0.90 vs. 0.85) and >66% (0.84 vs. 0.72). For SCD CAP cut-offs for differentiating steatosis ≥5%, >33% and >66% were 255.0 dB/m, 283.5 dB/m and 293.5 dB/m. However, cut-offs were elevated by approximately 60-70 dB/m for SCD ≥25 mm. When stratified by fibrosis grade, LSM was significantly affected by SCD ≥25 mm for advanced fibrosis (≥F3) in NAFLD, but not in CHB. CAP is a promising tool for detecting and quantifying hepatic steatosis. SCD ≥25 mm may cause overestimation of steatosis. Similarly, SCD ≥25 mm affects the detection of advanced fibrosis by LSM in NAFLD patients. © 2015 The Authors. Liver International Published by John Wiley & Sons Ltd.

  11. Monitoring vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Tiryaki, B. [Hacettepe University (Turkey). Dept. of Mining Engineering


    The paper examines the prediction and optimisation of machine vibrations in longwall shearers. Underground studies were carried out at the Middle Anatolian Lignite Mine, between 1993 and 1997. Several shearer drums with different pick lacing arrangements were designed and tested on double-ended ranging longwall shearers employed at the mine. A computer program called the Vibration Analysis Program (VAP) was developed for analysing machine vibrations in longwall shearers. Shearer drums that were tested underground, as well as some provided by leading manufacturers, were analyzed using these programs. The results of the experiments and computer analyses are given in the article. 4 refs., 9 figs.

  12. Shock and vibration effects on performance reliability and mechanical integrity of proton exchange membrane fuel cells: A critical review and discussion (United States)

    Haji Hosseinloo, Ashkan; Ehteshami, Mohsen Mousavi


    Performance reliability and mechanical integrity are the main bottlenecks in mass commercialization of PEMFCs for applications with inherent harsh environment such as automotive and aerospace applications. Imparted shock and vibration to the fuel cell in such applications could bring about numerous issues including clamping torque loosening, gas leakage, increased electrical resistance, and structural damage and breakage. Here, we provide a comprehensive review and critique of the literature focusing on the effects of mechanically harsh environment on PEMFCs, and at the end, we suggest two main future directions in FC technology research that need immediate attention: (i) developing a generic and adequately accurate dynamic model of PEMFCs to assess the dynamic response of FC devices, and (ii) designing effective and robust shock and vibration protection systems based on the developed models in (i).

  13. Reduction of personnel vibration hazards in underground coal mines

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  14. The effect of whole body vibration on balance, gait performance and mobility in people with stroke: a systematic review and meta-analysis. (United States)

    Yang, Xiaotian; Wang, Pu; Liu, Chuan; He, Chengqi; Reinhardt, Jan D


    To examine the effect of whole body vibration on balance, gait performance and mobility among people with stroke. A systematic review was conducted by two independent reviewers who completed the article search and selection. We included randomized controlled trials published in English examining effects of whole body vibration on balance, gait, mobility, muscle strength and muscle tone in adults with a clinical diagnosis of stroke. Articles were excluded if they were research studies on people with other primary diagnosis, abstracts published in the conferences or books. The Cochrane risk of bias tool was used to assess the methodological quality of the selected studies. Sources included Cochrane Central Register of Controlled Trials, Pubmed, MEDLINE, CINAHL, EMBASE, PEDro, PsycINFO, Science Citation Index,, Current Controlled Trials, Stroke Trials Registry, and reference lists of all relevant articles. Eight randomized controlled trials (nine articles) involving 271 participants were included in this meta-analysis. No significant improvement was found regarding Berg balance scale (SMD=-0.08, 95%CI=-1.35 to 1.19, P=0.91), mobility (SMD=0.45, 95%CI=-0.46 to 1.37, P=0.33), maximal isometric contracion of knee extension strength (SMD=0.23, 95%CI=-0.27 to 0.74, P=0.36), and maximal isometric contracion of knee extension strength (SMD=0.09, 95%CI=-0.38 to 0.56, P=0.71). There was no evidence for effects of whole body vibration on balance in people with stroke. Effects of whole body vibration on mobility and gait performance remain inconclusive. More large and high-quality trials are required. © The Author(s) 2014.

  15. Vibration control in semi-active suspension of the experimental off-road vehicle using information about suspension deflection

    Directory of Open Access Journals (Sweden)

    Kasprzyk Jerzy


    Full Text Available The efficiency of vibration control in an automotive semi-active suspension system depends on the quality of information from sensors installed in the vehicle, including information about deflection of the suspension system. The control algorithm for vibration attenuation of the body takes into account its velocity as well as the relative velocity of the suspension. In this paper it is proposed to use the Linear Variable Differential Transformer (LVDT unit to measure the suspension deflection and then to estimate its relative velocity. This approach is compared with a typical solution implemented in such applications, where the relative velocity is calculated by processing signals acquired from accelerometers placed on the body and on the chassis. The experiments performed for an experimental All-Terrain Vehicle (ATV confirm that using LVDT units allows for improving ride comfort by better vibration attenuation of the body.

  16. [Radiometers performance attenuation and data correction in long-term observation of total radiation and photosynthetically active radiation in typical forest ecosystems in China]. (United States)

    Zhu, Zhi-Lin; Sun, Xiao-Min; Yu, Gui-Rui; Wen, Xue-Fa; Zhang, Yi-Ping; Han, Shi-Jie; Yan, Jun-Hua; Wang, Hui-Min


    Based on the total radiation and photosynthetically active radiation (PAR) observations with net radiometer (CNR1) and quantum sensor (Li-190SB) in 4 ChinaFLUX forest sites (Changbaishan, Qianyanzhou, Dinghushan, and Xishuangbanna) in 2003-2008, this paper analyzed the uncertainties and the radiometers performance changes in long-term and continuous field observation. The results showed that the 98% accuracy of the total radiation measured with CNR1 (Q(cNR1)) could satisfy the technical criterion for the sites except Xishuangbanna where the Q(CNR1) was averagely about 7% lower than Q(CM11), the radiation measured with high accuracy pyranometer CM11. For most sites, though the temperature had definite effects on the performance of CNR1, the effects were still within the allowable range of the accuracy of the instrument. Besides temperature, the seasonal fog often occurred in tropical rain forests in Xishuangbanna also had effects on the performance of CNR1. Based on the long-term variations of PAR, especially its ratio to total radiation in the 4 sites, it was found that quantum sensor (Li-190SB) had obvious performance attenuation, with the mean annual attenuation rate being about 4%. To correct the observation error caused by Li-190SB, an attempt was made to give a post-correction of the PAR observations, which could basically eliminate the quantum sensor's performance attenuation due to long-term field measurement.

  17. Field measurements and analyses of environmental vibrations induced by high-speed Maglev. (United States)

    Li, Guo-Qiang; Wang, Zhi-Lu; Chen, Suwen; Xu, You-Lin


    Maglev, offers competitive journey-times compared to the railway and subway systems in markets for which distance between the stations is 100-1600km owing to its high acceleration and speed; however, such systems may have excessive vibration. Field measurements of Maglev train-induced vibrations were therefore performed on the world's first commercial Maglev line in Shanghai, China. Seven test sections along the line were selected according to the operating conditions, covering speeds from 150 to 430km/h. Acceleration responses of bridge pier and nearby ground were measured in three directions and analyzed in both the time and frequency domain. The effects of Maglev train speed on vibrations of the bridge pier and ground were studied in terms of their peak accelerations. Attenuation of ground vibration was investigated up to 30m from the track centerline. Effects of guideway configuration were also analyzed based on the measurements through two different test sections with same train speed of 300km/h. The results showed that peak accelerations exhibited a strong correlation with both train speed and distance off the track. Guideway configuration had a significant effect on transverse vibration, but a weak impact on vertical and longitudinal vibrations of both bridge pier and ground. Statistics indicated that, contrary to the commonly accepted theory and experience, vertical vibration is not always dominant: transverse and longitudinal vibrations should also be considered, particularly near turns in the track. Moreover, measurements of ground vibration induced by traditional high-speed railway train were carried out with the same testing devices in Bengbu in the Anhui Province. Results showed that the Maglev train generates significantly different vibration signatures as compared to the traditional high-speed train. The results obtained from this paper can provide good insights on the impact of Maglev system on the urban environment and the quality of human life

  18. Oscillatory whole-body vibration improves exercise capacity and physical performance in pulmonary arterial hypertension: a randomised clinical study. (United States)

    Gerhardt, Felix; Dumitrescu, Daniel; Gärtner, Carina; Beccard, Ralf; Viethen, Thomas; Kramer, Tilmann; Baldus, Stephan; Hellmich, Martin; Schönau, Eckhard; Rosenkranz, Stephan


    In patients with pulmonary arterial hypertension (PAH), supportive therapies may be beneficial in addition to targeted medical treatment. Here, we evaluated the effectiveness and safety of oscillatory whole-body vibration (WBV) in patients on stable PAH therapy. Twenty-two patients with PAH (mean PAP≥25 mm Hg and pulmonary arterial wedge pressure (PAWP)≤15 mm Hg) who were in world health organization (WHO)-Functional Class II or III and on stable PAH therapy for≥3 months, were randomised to receive WBV (16 sessions of 1-hour duration within 4 weeks) or to a control group, that subsequently received WBV. Follow-up measures included the 6-min walking distance (6MWD), cardiopulmonary exercise testing (CPET), echocardiography, muscle-power, and health-related quality of life (HRQoL; SF-36 and LPH questionnaires). When compared to the control group, patients receiving WBV exhibited a significant improvement in the primary endpoint, the 6MWD (+35.4±10.9 vs -4.4±7.6 m), resulting in a net benefit of 39.7±7.8 m (p=0.004). WBV was also associated with substantial improvements in CPET variables, muscle power, and HRQoL. The combined analysis of all patients (n=22) indicated significant net improvements versus baseline in the 6MWD (+38.6 m), peakVO2 (+65.7 mL/min), anaerobic threshold (+40.9 mL VO2/min), muscle power (+4.4%), and HRQoL (SF-36 +9.7, LPH -11.5 points) (all p<0.05). WBV was well tolerated in all patients, and no procedure-related severe adverse events (SAEs) occurred. WBV substantially improves exercise capacity, physical performance, and HRQoL in patients with PAH who are on stable targeted therapy. This methodology may be utilised in structured training programmes, and may be feasible for continuous long-term physical exercise in these patients. NCT01763112; Results. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to

  19. Vibrational Diver (United States)

    Kozlov, Victor; Ivanova, Alevtina; Schipitsyn, Vitalii; Stambouli, Moncef


    The paper is concerned with dynamics of light solid in cavity with liquid subjected to rotational vibration in the external force field. New vibrational phenomenon - diving of a light cylinder to the cavity bottom is found. The experimental investigation of a horizontal annulus with a partition has shown that under vibration a light body situated in the upper part of the layer is displaced in a threshold manner some distance away from the boundary. In this case the body executes symmetric tangential oscillations. An increase of the vibration intensity leads to a tangential displacement of the body near the external boundary. This displacement is caused by the tangential component of the vibrational lift force, which appears as soon as the oscillations lose symmetry. In this case the trajectory of the body oscillatory motion has the form of a loop. The tangential lift force makes stable the position of the body on the inclined section of the layer and even in its lower part. A theoretical interpretation has been proposed, which explains stabilization of a quasi-equilibrium state of a light body near the cavity bottom in the framework of vibrational hydromechanics.

  20. Performance investigation of a novel pseudoelastic SMA mesh washer gear wheel with micro-jitter attenuation capability (United States)

    Kwon, Seong-Cheol; Jeon, Su-Hyeon; Oh, Hyun-Ung


    A stepper-actuated mechanism, such as a gimbal type antenna, is a major source of micro-jitters that affect the image quality of a high-resolution observation satellite. Attenuating micro-jitter disturbances induced by a stepper motor activation is one method of enhancing image quality of an observation satellite. In this study, we propose a novel gear with micro-jitter attenuation capability for stepper-actuated mechanism. This can be achieved by implementing a pseudoelastic shape memory alloy mesh washer on the gear wheel. This application makes it possible to achieve the gear with lower torsional stiffness and higher damping in the torsional direction of the gear, whose characteristics will assist in resolving the micro-jitter attenuation issues of a gear. The effectiveness of the gear proposed in this study was demonstrated by numerical simulation and jitter measurement tests using the gimbal type antenna mechanism actuated by the stepper motor.

  1. Improvement of the seismic noise attenuation performance of the Monolithic Geometric Anti-Spring filters for gravitational wave interferometric detectors

    Energy Technology Data Exchange (ETDEWEB)

    Stochino, Alberto [Dipartimento di Fisica, Universita di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa (Italy); California Institute of Technology, MS 18-34, 91125 Pasadena, CA (United States)], E-mail:; DeSalvo, Riccardo [California Institute of Technology, MS 18-34, 91125 Pasadena, CA (United States); Huang Yumei [Department of Astronomy, Beijing Normal University, 100875 Beijing (China); California Institute of Technology, MS 18-34, 91125 Pasadena, CA (United States); Sannibale, Virginio [California Institute of Technology, MS 18-34, 91125 Pasadena, CA (United States)


    The Monolithic Geometric Anti-Spring (GAS) filter is one of the most efficient vertical seismic isolation devices for Gravitational Wave (GW) interferometers. However, the attenuation of this filter was previously limited to around 60 dB due to the high frequency saturation associated with the filter's distributed mass-a problem typical of passive mechanical filters. We show that it is possible to circumvent this limit using a compensation wand based on the Center Of Percussion (COP) effect. When this device is mounted in parallel with the blade springs of a GAS filter, attenuation improves to 80 dB in the region above 10 Hz. Using this device it is therefore possible to design simpler attenuation chains consisting of fewer stages.

  2. Analysis of vibration characteristics of a prestressed concrete cable-stayed bridge using strong motion observation data. Jishin kansoku ni motozuku PC shachokyo no shindo tokusei no kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Inatomi, T. (Port and Harbour Research Institute, Kanagawa (Japan)); Takeda, T.; Obi, N.; Yamanobe, S. (Kajima Corp., Tokyo (Japan))


    Records of seismic observation were analyzed for the purpose of proving the validity of antiseismic design for a prestressed concrete (PC) cable-stayed bridge. This bridge is a three span continuous PC cable-stayed bridge of 498 m in bridge length, and is constructed on alluvial soft ground. The seismometer used is a servo type accelerometer. The observed frequency and mode of seismic vibration are in good agreement with those in the analysis and hence the validity of modelling of the structure in designing was confirmed. It was also confirmed that the bending vibration and torsional vibration of the main girder are separated as designed. However, some points such as a large difference in the observed vibration and analysed vibration in the mode accompanying rotation of the base are listed as problems to be solved in antiseismic design. In order to investigate the attenuation constant of the upper structure, a seismic wave response analysis was performed and its results were compared with observed ones. When the attenuation constant is assumed to be 2%, agreement of data between analysis and observation is good, and it is considered that the attenuation constant of the upper structure only without the effects of attenuation of energy escape from the base and crack generation in concrete was about 2% in the observed earthquake (maximum acceleration on the ground: 51 Gal). 8 refs., 9 figs., 2 tabs.

  3. Imaging performance comparison between CMOS and sCMOS detectors in a vibration test on large areas using digital holographic interferometry (United States)

    Flores-Morenoa, J. M.; Torre I., Manuel H. De la; Aguayo, Daniel D.; Fernando Mendoza, S.


    A comparison of the interferometric imaging performance of two different cameras during a vibration study is presented. One of the cameras has a high speed CMOS sensor and the second one uses a high resolution (scientific) sCMOS sensor. This comparison is based on the interferometric response as a merit parameter of these sensors which is not a conventional procedure. Even when the current standard for image quality is on the signal to noise ratio calculations, an interferometric test to evaluate the fringe pattern visibility is equivalent to the contrast to noise ratio value. An out of plane digital holographic interferometer is used to test each camera once at the time with the same experimental conditions. The object under study is a metallically framed table with a Formica cover with an observable area of 1.1 m2. The sample is deformed by means of a controlled vibration induced by a tip ended linear step motor. Results from each camera are presented as the retrieved optical phase during the vibration. Finally, some conclusions based on the post processed images are presented suggesting a smoother optical phase obtained with the sCMOS camera.

  4. Vibrating vaginal balls to improve pelvic floor muscle performance in women after childbirth: a protocol for a randomised controlled feasibility trial. (United States)

    Oblasser, Claudia; McCourt, Christine; Hanzal, Engelbert; Christie, Janice


    This paper presents a feasibility trial protocol the purpose of which is to prepare for a future randomised controlled trial to determine the effectiveness of vibrating vaginal pelvic floor training balls for postpartum pelvic floor muscle rehabilitation. Vibrating vaginal pelvic floor training balls are available in Austria to enhance women's pelvic floor muscles and thus prevent or treat urinary incontinence and other pelvic floor problems following childbirth. Nonetheless, there is currently little empirical knowledge to substantiate their use or assess their relative effectiveness in comparison to current standard care, which involves pelvic floor muscle exercises. Single blind, randomised controlled feasibility trial with two parallel groups. It is planned to recruit 56 postpartum women in Vienna, who will be randomised into one of two intervention groups to use either vibrating vaginal balls or a comparator pelvic floor muscle exercises for 12 weeks. As this is a feasibility study, study design features (recruitment, selection, randomisation, intervention concordance, data collection methods and tools) will be assessed and participants' views and experiences will be surveyed. Tested outcome measures, collected before and after the intervention, will be pelvic floor muscle performance as reported by participants and measured by perineometry. Descriptive and inferential statistics and content analysis will serve the preparation of the future trial. The results of this feasibility trial will inform the design and conduct of a full randomised controlled trial and provide insight into the experiences of women regarding the interventions and study participation. © 2015 John Wiley & Sons Ltd.

  5. Research on Electromagnetic Force Distribution and Vibration Performance of A Novel 10/4 Switched Reluctance Motor (United States)

    Fu, Ziyu; Wang, Xinyu; Cao, Cheng; Liu, Meng; Wang, Kangxi


    Radial electromagnetic force is one of the main reasons causing the vibration and noise of the switched reluctance motor. Based on this, the novel structure of 10/4 pole switched reluctance motor is proposed, which increases the air gap flux and electromagnetic torque by increasing the number of stator poles. In addition, the excitation current of the stator winding is reduced by early turn-off angle. Through the finite element modelling analysis, the results show the superiority of the new type of switched reluctance motor. In the end, the vibration characteristics of the conventional motor and the new motor are compared and analysed, and the effect of the structure of this new type of switched reluctance motor is verified.

  6. High accuracy position adjustment and vibration isolation actuator with the controlled ferrofluid (United States)

    Wu, Shuai; Li, Chunfang; Zhao, Xiangyu; Jiao, Zongxia


    An actuator for microposition adjustment and vibration isolation using the controlled ferrofluid is reported in this letter. The proposed actuator levitates on the ferrofluid which is affected by the combined dynamic magnetic field which is formed by coupling a permanent magnetic field with a controlled electromagnetic field. A controlled electromagnetic field is superposed on the permanent magnetic field in order to change the shape of the ferrofluid to ultimately move the actuator. The experimental results indicate that the proposed actuator can adjust the position with high accuracy and has a good dynamic performance. The proposed actuator can bear over 2 N loads, and the positioning accuracy is within 0.1 μ m. The stroke of the actuator is about of ±30 μ m with no load, and the stroke increases to ±75 μ m at 2 N load. Its dynamic band with -3 dB amplitude attenuation and -90° phase is over 40 Hz. In addition, the displacement has a very good linear relationship with the input current. The results also demonstrate that the actuator can isolate vibration in a wide frequency range, as the low frequency vibration can be compensated by the active motion control, while the high frequency vibration can be attenuated by the elasticity and damping effects of the ferrofluid. Consequently, the proposed actuator has a significant potential for applications where the high accuracy micro-position adjustment and vibration isolation are needed.

  7. Design Optimization of a Mecanum Wheel to Reduce Vertical Vibrations by the Consideration of Equivalent Stiffness

    Directory of Open Access Journals (Sweden)

    Jong-Jin Bae


    Full Text Available Mecanum wheels are capable of moving a vehicle to any direction instantaneously by the combination of independent wheel rotations. Because the mecanum wheel is composed of a hub and rollers, however, it has unavoidable drawbacks such as vertical and horizontal vibrations due to the sequential contacts between rollers and ground. In order to investigate the dynamic characteristics of a mecanum wheel, we made a prototype and performed experiments to measure the vertical vibrations. Interestingly, it was observed that the vertical accelerations were asymmetric with respect to the average value of signals; the vibration signals of upward and downward directions show quite different shape. This asymmetric phenomenon was confirmed through the dynamic simulations performed by RecurDyn. In addition, the peak-to-peak and RMS values of the displacements and accelerations were calculated to investigate the effects of the curvature of rollers on the vertical vibrations of the vehicle. Furthermore, we proposed a mecanum wheel having a spring to attenuate the vibrations. It was also noted that the significant reduction of the vertical accelerations was observed due to the absence of the spring. Finally, considering the equivalent stiffness of the mecanum wheel for several different fillet radii, we found the optimal geometric design which minimizes the vertical vibration of a mecanum wheel.

  8. A 5-week whole body vibration training improves peak torque performance but has no effect on stretch reflex in healthy adults: a randomized controlled trial. (United States)

    Yeung, S S; Yeung, E W


    This study aimed to investigate the neuromuscular adaptation following a 5-week high frequency and low amplitude whole body vibration (WBV) exercise training. The study is a prospective, double blind, randomized controlled intervention design with a total of 19 subjects volunteered to participate in the study. They were randomly assigned either to WBV exercise training or control group. Both groups participated in a 5-week training program. The intervention group received WBV in semi-squat position on a device with an amplitude of 0.76 mm, frequency of 40Hz, and peak acceleration of 23.9 m/s2. Each vibration training session consisted of 6 series of 60s on with 30s rest period in between. The control group underwent the same statically mini-squatting position without exposure to WBV. The effectiveness of the vibration program was evaluated by vertical jump test and the isokinetic knee extensor peak torque. The possible neural factors that contributed to the improved muscular performance were evaluated by the stretch induced knee jerk reflex. WBV training significantly enhanced the isokinetic knee extensor peak torque performance. Two-way mixed repeated measures analysis of variance revealed significant time effect of the changes in the peak torque (P=0.043) and the effect was significantly different between the intervention and control group (P=0.042). WBV did not affect vertical jump height, reflex latency of VL, EMGVL, and knee jerk angle. The results of this study do not support the hypothesis that the improvement in the muscular performance when subjects exposed to WBV training is attributed by neuromuscular efficiency via modulation of the muscle spindle sensitivity.

  9. Detailed analysis of petroleum hydrocarbon attenuation in biopiles by high-performance liquid chromatography followed by comprehensive two-dimensional gas chromatography. (United States)

    Mao, Debin; Lookman, Richard; Van De Weghe, Hendrik; Van Look, Dirk; Vanermen, Guido; De Brucker, Nicole; Diels, Ludo


    Enhanced bioremediation of petroleum hydrocarbons in two biopiles was quantified by high-performance liquid chromatography (HPLC) followed by comprehensive two-dimensional gas chromatography (GCXGC). The attenuation of 34 defined hydrocarbon classes was calculated by HPLC-GCXGC analysis of representative biopile samples at start-up and after 18 weeks of biopile operation. In general, a-cyclic alkanes were most efficiently removed from the biopiles, followed by monoaromatic hydrocarbons. Cycloalkanes and polycyclic aromatic hydrocarbons (PAHs) were more resistant to degradation. A-cyclic biomarkers farnesane, trimethyl-C13, norpristane, pristane and phytane dropped to only about 10% of their initial concentrations. On the other hand, C29-C31 hopane concentrations remained almost unaltered after 18 weeks of biopile operation, confirming their resistance to biodegradation. They are thus reliable indicators to estimate attenuation potential of petroleum hydrocarbons in biopile processed soils.

  10. Man-Induced Vibrations

    DEFF Research Database (Denmark)

    Jönsson, Jeppe; Hansen, Lars Pilegaard


    concerned with spectator-induced vertical vibrations on grandstands. The idea is to use impulse response analysis and base the load description on the load impulse. If the method is feasable, it could be used in connection with the formulation of requirements in building codes. During the last two decades...... 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...

  11. Vibration Sensitive Keystroke Analysis

    NARCIS (Netherlands)

    Lopatka, M.; Peetz, M.-H.; van Erp, M.; Stehouwer, H.; van Zaanen, M.


    We present a novel method for performing non-invasive biometric analysis on habitual keystroke patterns using a vibration-based feature space. With the increasing availability of 3-D accelerometer chips in laptop computers, conventional methods using time vectors may be augmented using a distinct

  12. Vibrating minds

    CERN Document Server


    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.

  13. Sensing Performance Analysis on Quartz Tuning Fork-Probe at the High Order Vibration Mode for Multi-Frequency Scanning Probe Microscopy

    Directory of Open Access Journals (Sweden)

    Xiaofei Zhang


    Full Text Available Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the low mode and detect near-field optically induced forces (based on the 2nd in-plane mode called the high mode. Particularly, the high mode sensing performance of the QTF-p is an important issue for characterizing the tip-sample interactions and achieving higher resolution microscopic imaging but the related researches are insufficient. Here, we investigate the vibration performance of QTF-p at high mode based on the experiment and finite element method. The frequency spectrum characteristics are obtained by our homemade laser Doppler vibrometer system. The effects of the properties of the connecting glue layer and the probe features on the dynamic response of the QTF-p sensor at the high mode are investigated for optimization design. Finally, compared with the low mode, an obvious improvement of quality factor, of almost 50%, is obtained at the high mode. Meanwhile, the QTF-p sensor has a high force sensing sensitivity and a large sensing range at the high mode, indicating a broad application prospect for force sensing.

  14. Sensing Performance Analysis on Quartz Tuning Fork-Probe at the High Order Vibration Mode for Multi-Frequency Scanning Probe Microscopy. (United States)

    Zhang, Xiaofei; Gao, Fengli; Li, Xide


    Multi-frequency scanning near-field optical microscopy, based on a quartz tuning fork-probe (QTF-p) sensor using the first two orders of in-plane bending symmetrical vibration modes, has recently been developed. This method can simultaneously achieve positional feedback (based on the 1st in-plane mode called the low mode) and detect near-field optically induced forces (based on the 2nd in-plane mode called the high mode). Particularly, the high mode sensing performance of the QTF-p is an important issue for characterizing the tip-sample interactions and achieving higher resolution microscopic imaging but the related researches are insufficient. Here, we investigate the vibration performance of QTF-p at high mode based on the experiment and finite element method. The frequency spectrum characteristics are obtained by our homemade laser Doppler vibrometer system. The effects of the properties of the connecting glue layer and the probe features on the dynamic response of the QTF-p sensor at the high mode are investigated for optimization design. Finally, compared with the low mode, an obvious improvement of quality factor, of almost 50%, is obtained at the high mode. Meanwhile, the QTF-p sensor has a high force sensing sensitivity and a large sensing range at the high mode, indicating a broad application prospect for force sensing.

  15. Passively damped vibration welding system and method (United States)

    Tan, Chin-An; Kang, Bongsu; Cai, Wayne W.; Wu, Tao


    A vibration welding system includes a controller, welding horn, an anvil, and a passive damping mechanism (PDM). The controller generates an input signal having a calibrated frequency. The horn vibrates in a desirable first direction at the calibrated frequency in response to the input signal to form a weld in a work piece. The PDM is positioned with respect to the system, and substantially damps or attenuates vibration in an undesirable second direction. A method includes connecting the PDM having calibrated properties and a natural frequency to an anvil of an ultrasonic welding system. Then, an input signal is generated using a weld controller. The method includes vibrating a welding horn in a desirable direction in response to the input signal, and passively damping vibration in an undesirable direction using the PDM.

  16. A tubular dielectric elastomer actuator: Fabrication, characterization and active vibration isolation

    DEFF Research Database (Denmark)

    Sarban, R.; Jones, R. W.; Mace, B. R.


    This contribution reviews the fabrication, characterization and active vibration isolation performance of a core-free rolled tubular dielectric elastomer (DE) actuator, which has been designed and developed by Danfoss PolyPower A/S. PolyPower DE material, PolyPower (TM), is produced in thin sheets...... the dominant dynamic characteristics of the core-free tubular actuator. It has been observed that all actuators have similar dynamic characteristics in a frequency range up to 1 kHz. A tubular actuator is then used to provide active vibration isolation (AVI) of a 250 g mass subject to shaker generated 'ground...... vibration'. An adaptive feedforward control approach is used to achieve this. The tubular actuator is shown to provide excellent isolation against harmonic vibratory disturbances with attenuation of the resulting 5 and 10 Hz harmonics being 66 and 23 dB, respectively. AVI against a narrow band vibratory...

  17. Vibrational and theoretical study of selected diacetylenes. (United States)

    Roman, Maciej; Baranska, Malgorzata


    Six commonly used disubstituted diacetylenes with short side-chains (RCCCCR, where R=CH2OH, CH2OPh, C(CH3)2OH, C(CH3)3, Si(CH3)3, and Ph) were analyzed using vibrational spectroscopy and quantum-chemical calculations to shed new light on structural and spectroscopic properties of these compounds. Prior to that the conformational analysis of diacetylenes was performed to search the Potential Energy Surface for low-energy minima. Theoretical investigations were followed by the potential energy distribution (PED) analysis to gain deeper insight into FT-Raman and FT-IR spectra that, in some cases, were recorded for the first time for the studied compounds. The analysis was focused mainly on spectral features of the diacetylene system sensitive to the substitution. Shifts of the characteristic bands and changes in bond lengths were observed when changing the substituent. Furthermore, Fermi resonance was observed in the vibrational spectra of some diacetylenes. FT-IR spectra were measured by using two methods, i.e. transmission (with KBr substrate) and Attenuated Total Reflection (ATR), showing the latter adequate and fast tool for IR measurements of diacetylenes. Additionally, Surface Enhanced Raman Spectroscopy (SERS) was applied for phenyl derivative for the first time to study its interaction with metallic nanoparticles that seems to be perpendicular. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Granular dampers for the reduction of vibrations of an oscillatory saw (United States)

    Heckel, Michael; Sack, Achim; Kollmer, Jonathan E.; Pöschel, Thorsten


    Instruments for surgical and dental application based on oscillatory mechanics submit unwanted vibrations to the operator's hand. Frequently the weight of the instrument's body is increased to dampen its vibration. Based on recent research regarding the optimization of granular damping we developed a prototype granular damper that attenuates the vibrations of an oscillatory saw twice as efficiently as a comparable solid mass.

  19. Ultrasonic attenuation in rare-earth monoarsenides

    Indian Academy of Sciences (India)

    The toughness/fracture (G/BT) ratio is greater than 0.60, which implies that XAs compounds are brittle at room temperature. Further, the Debye temperature is computed using Debye average velocity as the input parameter. It helps in the characterization of lattice vibrations of a solid. In this work, ultrasonic attenuation due to ...

  20. Laser geodynamic satellite thermal/optical/vibrational analyses and testing, volume 2, book 1 technical report. [retroreflector performance (United States)


    The results are presented of a retroreflector performance improvement program. The following areas of the program are discussed: retroreflector dimensional verification, initial optical performance analysis, LAGEOS test retroreflector rework, final optical performance analysis, optical performance tests, evaluations and conclusions, and laser wavelength evaluation and dihedral angle selection. Data tables, diagrams, graphs, and photographs are included.

  1. Urban vibrations

    DEFF Research Database (Denmark)

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


      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. The nicotine metabolite, cotinine, attenuates glutamate (NMDA) antagonist-related effects on the performance of the five choice serial reaction time task (5C-SRTT) in rats. (United States)

    Terry, Alvin V; Buccafusco, Jerry J; Schade, R Foster; Vandenhuerk, Leah; Callahan, Patrick M; Beck, Wayne D; Hutchings, Elizabeth J; Chapman, James M; Li, Pei; Bartlett, Michael G


    Cotinine, the most predominant metabolite of nicotine in mammalian species, has a pharmacological half-life that greatly exceeds its precursor. However, until recently, relatively few studies had been conducted to systematically characterize the behavioral pharmacology of cotinine. Our previous work indicated that cotinine improves prepulse inhibition of the auditory startle response in rats in pharmacological impairment models and that it improves working memory in non-human primates. Here we tested the hypothesis that cotinine improves sustained attention in rats and attenuates behavioral alterations induced by the glutamate (NMDA) antagonist MK-801. The effects of acute subcutaneous (dose range 0.03-10.0 mg/kg) and chronic oral administration (2.0 mg/kg/day in drinking water) of cotinine were evaluated in fixed and variable stimulus duration (VSD) as well as variable intertrial interval (VITI) versions of a five choice serial reaction time task (5C-SRTT). The results indicated only subtle effects of acute cotinine (administered alone) on performance of the 5C-SRTT (e.g., decreases in timeout responses). However, depending on dose, acute treatment with cotinine attenuated MK-801-related impairments in accuracy and elevations in timeout responses, and it increased the number of completed trials. Moreover, chronic cotinine attenuated MK-801-related impairments in accuracy and it reduced premature and timeout responses when the demands of the task were increased (i.e., by presenting VSDs or VITIs in addition to administering MK-801). These data suggest that cotinine may represent a prototype for compounds that have therapeutic potential for neuropsychiatric disorders (i.e., by improving sustained attention and decreasing impulsive and compulsive behaviors), especially those characterized by glutamate receptor alterations. Copyright © 2012 Elsevier Inc. All rights reserved.



    KOÇ, Gözde; K. Alparslan ERMAN


    Whole body vibration training, the person’s entire body on a platform, creates a vibration that may affect the muscles and bones. Despite the vibration used of massage and treatment since ancient times, it was used as a training method in recent years and became very popular and has attracted the attention of researchers. Whole body vibration training used both sport science with the aim to improve performance and in the fields of medicine for sports therapy. Whole body vibration training bri...

  4. 14th International Conference on Acoustics and Vibration of Mechanical Structures

    CERN Document Server

    Marinca, Vasile


    This book is a collection of papers presented at Acoustics and Vibration of Mechanical Structures 2017 – AVMS 2017 – highlighting the current trends and state-of-the-art developments in the field. It covers a broad range of topics, such as noise and vibration control, noise and vibration generation and propagation, the effects of noise and vibration, condition monitoring and vibration testing, modeling, prediction and simulation of noise and vibration, environmental and occupational noise and vibration, noise and vibration attenuators, as well as biomechanics and bioacoustics. The book also presents analytical, numerical and experimental techniques for evaluating linear and non-linear noise and vibration problems (including strong nonlinearity). It is primarily intended for academics, researchers and professionals, as well as PhD students in various fields of the acoustics and vibration of mechanical structures.

  5. Health risks of vibration exposure to wheelchair users in the community (United States)

    Garcia-Mendez, Yasmin; Pearlman, Jonathan L.; Boninger, Michael L.; Cooper, Rory A.


    Objective The purpose of this study was to evaluate whole-body vibration (WBV) exposure to wheelchair (WC) users in their communities and to determine the effect of WC frame type (folding, rigid, and suspension) in reducing WBV transmitted to the person. Design An observational case-control study of the WBV exposure levels among WC users. Participants Thirty-seven WC users, with no pressure sores, 18 years old or older and able to perform independent transfers. Main outcome measures WC users were monitored for 2 weeks to collect WBV exposure, as well as activity levels, by using custom vibration and activity data-loggers. Vibration levels were evaluated using ISO 2631-1 methods. Results All WC users who participated in this study were continuously exposed to WBV levels at the seat that were within and above the health caution zone specified by ISO 2631-1 during their day-to-day activities (0.83 ± 0.17 m/second2, weighted root-mean-squared acceleration, for 13.07 ± 3.85 hours duration of exposure). WCs with suspension did not attenuate vibration transmitted to WC users (V = 0.180, F(8, 56) = 0.692, P = 0.697). Conclusions WBV exposure to WC users exceeds international standards. Suspension systems need to be improved to reduce vibrations transmitted to the users. PMID:23820152

  6. Theory of vibration protection

    CERN Document Server

    Karnovsky, Igor A


    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...

  7. Attenuation in silica-based optical fibers

    DEFF Research Database (Denmark)

    Wandel, Marie Emilie


    In this thesis on attenuation in silica based optical fibers results within three main topics are reported. Spectral attenuation measurements on transmission fibers are performed in the wide wavelength range 290 nm – 1700 nm. The measured spectral attenuation is analyzed with special emphasis...... on absorption peaks in order to investigate the cause of an unusual high attenuation in a series of transmission fibers. Strong indications point to Ni2+ in octahedral coordination as being the cause of the high attenuation. The attenuation of fibers having a high core refractive index is analyzed and the cause...... of the high attenuation measured in such fibers is described as being due to scattering of light on fluctuations of the core diameter. A novel semi-empirical model for predicting the attenuation of high index fibers is presented. The model is shown to be able to predict the attenuation of high index fibers...

  8. Comparison of whole-body vibration exposures in buses: effects and interactions of bus and seat design. (United States)

    Jonsson, Per M G; Rynell, Patrik W; Hagberg, Mats; Johnson, Peter W


    Bus and seat design may be important for the drivers' whole-body vibration (WBV). WBV exposures in buses during actual operation were assessed. WBV attenuation performance between an air-suspension seat and a static pedestal seat in low-floor buses was compared; there were no differences in WBV attenuation between the seats. Air-suspension seat performance in a high-floor and low-floor bus was compared. Relative to the pedestal seat with its relatively static, limited travel seat suspension, the air-suspension seat with its dynamic, longer travel suspension provided little additional benefit. Relative to the measurement collected at the bus floor, the air-suspension seat amplified the WBV exposures in the high-floor bus. All WBV exposures were below European Union (EU) daily exposure action values. The EU Vibration Directive only allows the predominant axis of vibration exposure to be evaluated but a tri-axial vector sum exposure may be more representative of the actual health risks. Low back pain is common in bus drivers and studies have shown a relationship with whole body vibration. Relative to a pedestal seat with its limited travel seat suspension, the air-suspension seat with its longer travel suspension provided little additional benefit. Exposures were below European Union daily exposure action values.

  9. Four weeks of optimal load ballistic resistance training at the end of season attenuates declining jump performance of women volleyball players. (United States)

    Newton, Robert U; Rogers, Ryan A; Volek, Jeff S; Häkkinen, Keijo; Kraemer, William J


    Anecdotal and research evidence is that vertical jump performance declines over the competitive volleyball season. The purpose of this study was to evaluate whether a short period of ballistic resistance training would attenuate this loss. Fourteen collegiate women volleyball players were trained for 11 weeks with periodized traditional and ballistic resistance training. There was a 5.4% decrease (p jump and reach height during the traditional training period (start of season to midseason), and a 5.3% increase (p jump performance were reflective of changes in underlying neuromuscular performance variables: in particular, power output and peak velocity during loaded jump squats, countermovement jumps, and drop jumps. During the first 7 weeks of traditional heavy resistance training, it appears that the neuromuscular system is depressed, perhaps by the combination of training, game play, and skills practice precluding adequate recovery. Introduction of a novel training stimulus in the form of ballistic jump squats and reduction of heavy resistance training of the leg extensors stimulated a rebound in performance, in some cases to exceed the athlete's ability at the start of the season. Periodization of in-season training programs similar to that used in this study may provide volleyball players with good vertical jump performance for the crucial end-of-season games.

  10. Experimental and theoretical study of the vibrational spectra of oligoureas: helical versus β-sheet-type secondary structures. (United States)

    Cavagnat, Dominique; Claudon, Paul; Fischer, Lucile; Guichard, Gilles; Desbat, Bernard


    Ab initio calculations of two oligoureas stabilized in helix and sheet organization have been performed. The hydrogen bond distances were found to be almost the same for both structures. The vibrational assignment of the two oligourea structures and the direction of the transition moment of each vibration have been determined. From these results, and using the experimental isotropic optical index determined for one oligourea, we have established the anisotropic infrared optical files for the two structures. Interestingly, most urea absorptions vibrate in only one principal direction. Also, the shift of the carbonyl band is weaker and inverse to what was reported for corresponding protein secondary structures. Finally, simulations of the Polarization Modulation Infrared Reflection Absorption Spectroscopy (PMIRRAS) and Attenuated Reflection Spectroscopy (ATR) infrared spectra demonstrate the possibility to determine the orientation of the oligoureas in thin or ultrathin films, even if in some cases it may be difficult to unambiguously assign their secondary structure.

  11. Monitoring Vibration of A Model of Rotating Machine

    Directory of Open Access Journals (Sweden)

    Arko Djajadi


    Full Text Available Mechanical movement or motion of a rotating machine normally causes additional vibration. A vibration sensing device must be added to constantly monitor vibration level of the system having a rotating machine, since the vibration frequency and amplitude cannot be measured quantitatively by only sight or touch. If the vibration signals from the machine have a lot of noise, there are possibilities that the rotating machine has defects that can lead to failure. In this experimental research project, a vibration structure is constructed in a scaled model to simulate vibration and to monitor system performance in term of vibration level in case of rotation with balanced and unbalanced condition. In this scaled model, the output signal of the vibration sensor is processed in a microcontroller and then transferred to a computer via a serial communication medium, and plotted on the screen with data plotter software developed using C language. The signal waveform of the vibration is displayed to allow further analysis of the vibration. Vibration level monitor can be set in the microcontroller to allow shutdown of the rotating machine in case of excessive vibration to protect the rotating machine from further damage. Experiment results show the agreement with theory that unbalance condition on a rotating machine can lead to larger vibration amplitude compared to balance condition. Adding and reducing the mass for balancing can be performed to obtain lower vibration level. 

  12. Modelling of in-vitro and in-vivo performance of aerosol emitted from different vibrating mesh nebulisers in non-invasive ventilation circuit. (United States)

    Rabea, Hoda; Ali, Ahmed M A; Salah Eldin, Randa; Abdelrahman, Maha M; Said, Amira S A; Abdelrahim, Mohamed E


    Substituting nebulisers by another in non-invasive ventilation circuit (NIV) involves many process variables which must be adjusted to ensure patient optimum therapy. However, there is a doubt when nebulisers use the same technology. Data mining technology based on artificial neural networks and genetic algorithms were used here to model in-vitro inhalation process and predict bioavailability from inhaled doses delivered by three different vibrating mesh nebulisers (VMNs) in NIV. Modelling of data indicated that in-vitro performance of VMNs was dependent mainly on fine particle fraction, mass median aerodynamic diameter (MMAD), total emitted dose (TED) and to lesser extent on nebuliser type. Ex-vivo model indicated that amount of salbutamol collected on facemask filter was directly affected by TED. In-vivo model showed that amount of salbutamol deposited into the lung (0.5hQ) and amount absorbed systemically (24hQ) were dependent directly on MMAD and TED. Female patients showed higher 24hQ values than males. Nebuliser type affected TED, 0.5hQ but not 24hQ values. Results indicate suitability of VMNs in achieving appropriate in-vitro inhalation performance model. The results also, indicate that the three VMNs are comparable and can be interchanged with no fear of any additional toxicity. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Side-Alternating Vibration Training Improves Muscle Performance in a Patient with Late-Onset Pompe Disease

    Directory of Open Access Journals (Sweden)

    Aneal Khan


    joint kinematics and kinetics. Her functional ability measured through the Rotterdam 9-item score was unchanged at 19/36. There were no elevations in serum creatine kinase or lactate. This is the first report, to our knowledge, of a performance improvement in a patient with Pompe disease using SAVT.

  14. Using FLUKA to Study Concrete Square Shield Performance in Attenuation of Neutron Radiation Produced by APF Plasma Focus Neutron Source (United States)

    Nemati, M. J.; Habibi, M.; Amrollahi, R.


    In 2010, representatives from the Nuclear Engineering and physics Department of Amirkabir University of Technology (AUT) requested development of a project with the objective of determining the performance of a concrete shield for their Plasma Focus as neutron source. The project team in Laboratory of Nuclear Engineering and physics department of Amirkabir University of Technology choose some shape of shield to study on their performance with Monte Carlo code. In the present work, the capability of Monte Carlo code FLUKA will be explored to model the APF Plasma Focus, and investigating the neutron fluence on the square concrete shield in each region of problem. The physical models embedded in FLUKA are mentioned, as well as examples of benchmarking against future experimental data. As a result of this study suitable thickness of concrete for shielding APF will be considered.

  15. Assessment of Four Passive Hearing Protection Devices for Continuous Noise Attenuation, Impulsive Noise Insertion Loss, and Auditory Localization Performance (United States)


    devices. Localization testing – free field localization test The localization testing was completed in the anechoic chamber located in the...participant from determining the location of the loudspeaker visually, the test was performed with no lights turned on in the anechoic chamber ...VI Acoustics Trident software. For each threshold measurement, the participant was seated in the sound chamber , and given a thumb switch. One

  16. Effect of combining passive muscle stretching and whole body vibration on spasticity and physical performance of children and adolescents with cerebral palsy. (United States)

    Tupimai, Teeraporn; Peungsuwan, Punnee; Prasertnoo, Jitlada; Yamauchi, Juinichiro


    [Purpose] This study evaluated the immediate and short-term effects of a combination of prolonged passive muscle stretching (PMS) and whole body vibration (WBV) on the spasticity, strength and balance of children and adolescents with cerebral palsy. [Subjects and Methods] A randomized two-period crossover trial was designed. Twelve subjects with cerebral palsy aged 10.6 ± 2.4 years received both PMS alone as a control group (CG) and a combination of PMS and WBV as an experimental group (EG). After random allocation to the trial schedules of either EG-CG or CG-EG, CG received prolonged PMS while standing on a tilt-table for 40 minutes/day, and EG received prolonged PMS for 30 minutes, followed by 10 minutes WBV. Both CG and EG received the treatment 5 days/week for 6 weeks. [Results] Immediately after one treatment, EG resulted in better improvement in scores on the Modified Ashworth Scale than CG. After the 6-week intervention, EG also showed significantly decreased scores on the Modified Ashworth Scale compared to CG. Both CG and EG showed significantly reduced the performance times in the five times sit to stand test, and EG also showed significantly increased scores on the pediatric balance scale. [Conclusion] This study showed that 6 weeks of combined prolonged PMS and WBV had beneficial effects on the spasticity, muscle strength and balance of children and adolescents with CP.

  17. Investigating the optimal passive and active vibration controls of adjacent buildings based on performance indices using genetic algorithms (United States)

    Hadi, Muhammad N. S.; Uz, Mehmet E.


    This study proposes the optimal passive and active damper parameters for achieving the best results in seismic response mitigation of coupled buildings connected to each other by dampers. The optimization to minimize the H2 and H∞ norms in the performance indices is carried out by genetic algorithms (GAs). The final passive and active damper parameters are checked for adjacent buildings connected to each other under El Centro NS 1940 and Kobe NS 1995 excitations. Using real coded GA in H∞ norm, the optimal controller gain is obtained by different combinations of the measurement as the feedback for designing the control force between the buildings. The proposed method is more effective than other metaheuristic methods and more feasible, although the control force increased. The results in the active control system show that the response of adjacent buildings is reduced in an efficient manner.

  18. Time-domain filtered-x-Newton narrowband algorithms for active isolation of frequency-fluctuating vibration (United States)

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


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

  19. Controllable Fabricating Dielectric-Dielectric SiC@C Core-Shell Nanowires for High-Performance Electromagnetic Wave Attenuation. (United States)

    Liang, Caiyun; Wang, Zhijiang


    Heterostructured dielectric-dielectric nanowires of SiC core and carbon shell (SiC@C) with high-performance electromagnetic wave absorption were synthesized by combining an interfacial in situ polymer encapsulation and carbonization process. This approach overcomes the shortcomings of previous reported methods to prepare carbon shell that both carbon shell and free carbon particles are formed simultaneously. In our developed approach, the core of SiC nanowires are first positively charged. Then the negative resorcinol-formaldehyde polymers as the carbon source are anchored on SiC nanowires under the attraction of electrostatic force, which well suppresses the nucleation of free carbon particles. The thickness of the carbon shell could be modulated from 4 to 20 nm by simply adjusting the moral ratio of resorcinol to SiC nanowires. The resulting SiC@C core-shell nanostructures without free carbon particles offer synergism among the SiC nanowires and the carbon shells, generating multiple dipolar polarization, surfaced polarization, and associated relaxations, which endow SiC@C hybrid nanowires with a minimum reflection loss (RL) value of -50 dB at the frequency of 12 GHz and an effective absorption bandwidth of 8 GHz with RL value under -10 dB at the optimized state. Our results demonstrate that SiC@C hybrid nanowires are promising candidates for electromagnetic wave absorption applications.

  20. The feasibility of whole body vibration in institutionalised elderly persons and its influence on muscle performance, balance and mobility: a randomised controlled trial [ISRCTN62535013

    Directory of Open Access Journals (Sweden)

    Van Hees Ellen


    Full Text Available Abstract Background Fatigue or lack of interest can reduce the feasibility of intensive physical exercise in nursing home residents. Low-volume exercise interventions with similar training effects might be an alternative. The aim of this randomised controlled trial was to investigate the feasibility of Whole Body Vibration (WBV in institutionalised elderly, and its impact on functional capacity and muscle performance. Methods Twenty-four nursing home residents (15 female, 9 male; mean age 77.5 ± 11.0 years were randomised (stratification for age, gender and ADL-category to 6 weeks static WBV exercise (WBV+, N = 13 or control (only static exercise; N = 11. Outcome measures were exercise compliance, timed up-and-go, Tinetti-test, back scratch, chair sit-and-reach, handgrip strength and linear isokinetic leg extension. Results At baseline, WBV+ and control groups were similar for all outcome variables. Twenty-one participants completed the program and attended respectively 96% and 86% of the exercise sessions for the WBV+ and control groups. Training-induced changes in timed up-and-go and Tinetti-test were better for WBV+ compared to control (p = 0.029 for timed up-and-go, p = 0.001 and p = 0.002 for Tinetti body balance and total score respectively. In an alternative analysis (Worst Rank Score & Last Observation Carried Forward the differences in change remained significant on the Tinetti body balance and total score. No other significant differences in change between both groups were observed. Conclusion In nursing home residents with limited functional dependency, six weeks static WBV exercise is feasible, and is beneficial for balance and mobility. The supplementary benefit of WBV on muscle performance compared to classic exercise remains to be explored further.

  1. Prediction of Near-Field Wave Attenuation Due to a Spherical Blast Source (United States)

    Ahn, Jae-Kwang; Park, Duhee


    Empirical and theoretical far-field attenuation relationships, which do not capture the near-field response, are most often used to predict the peak amplitude of blast wave. Jiang et al. (Vibration due to a buried explosive source. PhD Thesis, Curtin University, Western Australian School of Mines, 1993) present rigorous wave equations that simulates the near-field attenuation to a spherical blast source in damped and undamped media. However, the effect of loading frequency and velocity of the media have not yet been investigated. We perform a suite of axisymmetric, dynamic finite difference analyses to simulate the propagation of stress waves induced by spherical blast source and to quantify the near-field attenuation. A broad range of loading frequencies, wave velocities, and damping ratios are used in the simulations. The near-field effect is revealed to be proportional to the rise time of the impulse load and wave velocity. We propose an empirical additive function to the theoretical far-field attenuation curve to predict the near-field range and attenuation. The proposed curve is validated against measurements recorded in a test blast.

  2. A disorder-based strategy for tunable, broadband wave attenuation (United States)

    Zhang, Weiting; Celli, Paolo; Cardella, Davide; Gonella, Stefano


    One of the most daunting limitations of phononic crystals and acoustic/elastic metamaterials is their passivity: a given configuration is bound to display its phononic properties only around its design point, i.e., working at some pre-determined operating conditions. In the past decade, this shortcoming has inspired the design of phononic media with tunable wave characteristics; noteworthy results have been obtained through a family of methodologies involving shunted piezoelectric elements. Shunting a piezoelectric element means connecting it to a passive electric circuit; tunability stems from the ability to modify the effective mechanical properties of the piezoelectric medium by modifying the circuit characteristics. One of the most popular shunting circuits is the resistor-inductor, which allows the patch-and-shunt system to behave as an electromechanical resonator. A common motif among the works employing shunted piezos for phononic control is periodicity: the patches are typically periodically placed in the domain and the circuits are identically tuned. The objective of this work is to demonstrate that the wave attenuation performance of structures with shunted piezoelectric patches can be improved by leveraging notions of organized disorder. Based on the idea of rainbow trapping broadband wave attenuation obtained by tuning an array of resonators at distinct neighboring frequencies we design and test an electromechanical waveguide structure capable of attenuating waves over broad frequency ranges. In order to emphasize the fact that periodicity is not a binding requirement when working with RL shunts (which induce locally resonant bandgaps), we report on the performance of random arrangements of patches. In an attempt to demonstrate the tunability attribute of our strategy, we take advantage of the reconfigurability of the circuits to show how a single waveguide can attenuate both waves and vibrations over different frequency ranges.

  3. Fluid dynamic bowtie attenuators (United States)

    Szczykutowicz, Timothy P.; Hermus, James


    Fluence field modulated CT allows for improvements in image quality and dose reduction. To date, only 1-D modulators have been proposed, the extension to 2-D modulation is difficult with solid-metal attenuation-based modulators. This work proposes to use liquids and gas to attenuate the x-ray beam which can be arrayed allowing for 2-D fluence modulation. The thickness of liquid and the pressure for a given path length of gas were determined that provided the same attenuation as 30 cm of soft tissue at 80, 100, 120, and 140 kV. Gaseous Xenon and liquid Iodine, Zinc Chloride, and Cerium Chloride were studied. Additionally, we performed some proof-of-concept experiments in which (1) a single cell of liquid was connected to a reservoir which allowed the liquid thickness to be modulated and (2) a 96 cell array was constructed in which the liquid thickness in each cell was adjusted manually. Liquid thickness varied as a function of kV and chemical composition, with Zinc Chloride allowing for the smallest thickness; 1.8, 2.25, 3, and 3.6 cm compensated for 30 cm of soft tissue at 80, 100, 120, and 140 kV respectively. The 96 cell Iodine attenuator allowed for a reduction in both dynamic range to the detector and scatter to primary ratio. Successful modulation of a single cell was performed at 0, 90, and 130 degrees using a simple piston/actuator. The thickness of liquids and the Xenon gas pressure seem logistically implementable within the constraints of CBCT and diagnostic CT systems.


    Directory of Open Access Journals (Sweden)

    Darryl J. Cochrane


    Full Text Available There is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception suggesting neural enhancement. Nevertheless, the neural mechanism(s of vibration and its potentiating effect have received little attention. One proposal suggests that spinal reflexes enhance muscle contraction through a reflex activity known as tonic vibration stretch reflex (TVR, which increases muscle activation. However, TVR is based on direct, brief, and high frequency vibration (>100 Hz which differs to indirect vibration, which is applied to the whole body or body parts at lower vibration frequency (5-45 Hz. Likewise, muscle tuning and neuromuscular aspects are other candidate mechanisms used to explain the vibration phenomenon. But there is much debate in terms of identifying which neural mechanism(s are responsible for acute vibration; due to a number of studies using various vibration testing protocols. These protocols include: different methods of application, vibration variables, training duration, exercise types and a range of population groups. Therefore, the neural mechanism of acute vibration remain equivocal, but spinal reflexes, muscle tuning and neuromuscular aspects are all viable factors that may contribute in different ways to increasing muscular performance. Additional research is encouraged to determine which neural mechanism(s and their contributions are responsible for acute vibration. Testing variables and vibration applications need to be standardised before reaching a consensus on which neural mechanism(s occur during and post-vibration

  5. Investigation and analysis the vibration of handles of chainsaw without cutting


    M Feyzi; A Jafari; H Ahmadi


    Introduction: Nowadays most of the agricultural and industrial tasks are performed using different machines and almost any people are exposed to the vibration of these machines. Just as sound can be either music to the ear or irritating noise, human vibrations can either be pleasant or unpleasant. Whole-body vibration and hand-arm vibration are two main types of unpleasant vibration. The hand-arm transmitted vibration can cause complex vascular, neurological and musculoskeletal disorder, coll...

  6. Vibration-reducing gloves: transmissibility at the palm of the hand in three orthogonal directions (United States)

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


    Vibration-reducing (VR) gloves are commonly used as a means to help control exposures to hand-transmitted vibrations generated by powered hand tools. The objective of this study was to characterise the vibration transmissibility spectra and frequency-weighted vibration transmissibility of VR gloves at the palm of the hand in three orthogonal directions. Seven adult males participated in the evaluation of seven glove models using a three-dimensional hand–arm vibration test system. Three levels of hand coupling force were applied in the experiment. This study found that, in general, VR gloves are most effective at reducing vibrations transmitted to the palm along the forearm direction. Gloves that are found to be superior at reducing vibrations in the forearm direction may not be more effective in the other directions when compared with other VR gloves. This casts doubts on the validity of the standardised glove screening test. Practitioner Summary This study used human subjects to measure three-dimensional vibration transmissibility of vibration-reducing gloves at the palm and identified their vibration attenuation characteristics. This study found the gloves to be most effective at reducing vibrations along the forearm direction. These gloves did not effectively attenuate vibration along the handle axial direction. PMID:24160755

  7. Caprylic triglyceride as a novel therapeutic approach to effectively improve the performance and attenuate the symptoms due to the motor neuron loss in ALS disease.

    Directory of Open Access Journals (Sweden)

    Wei Zhao

    Full Text Available Amyotrophic lateral sclerosis (ALS is a neurodegenerative disorder of motor neurons causing progressive muscle weakness, paralysis, and finally death. ALS patients suffer from asthenia and their progressive weakness negatively impacts quality of life, limiting their daily activities. They have impaired energy balance linked to lower activity of mitochondrial electron transport chain enzymes in ALS spinal cord, suggesting that improving mitochondrial function may present a therapeutic approach for ALS. When fed a ketogenic diet, the G93A ALS mouse shows a significant increase in serum ketones as well as a significantly slower progression of weakness and lower mortality rate. In this study, we treated SOD1-G93A mice with caprylic triglyceride, a medium chain triglyceride that is metabolized into ketone bodies and can serve as an alternate energy substrate for neuronal metabolism. Treatment with caprylic triglyceride attenuated progression of weakness and protected spinal cord motor neuron loss in SOD1-G93A transgenic animals, significantly improving their performance even though there was no significant benefit regarding the survival of the ALS transgenic animals. We found that caprylic triglyceride significantly promoted the mitochondrial oxygen consumption rate in vivo. Our results demonstrated that caprylic triglyceride alleviates ALS-type motor impairment through restoration of energy metabolism in SOD1-G93A ALS mice, especially during the overt stage of the disease. These data indicate the feasibility of using caprylic acid as an easily administered treatment with a high impact on the quality of life of ALS patients.

  8. Immediate effects after stochastic resonance whole-body vibration on physical performance on frail elderly for skilling-up training: a blind cross-over randomised pilot study. (United States)

    Rogan, Slavko; Schmidtbleicher, Dietmar; Radlinger, Lorenz


    This pilot study examined the feasibility outcome recruitment, safety and compliance of the investigation for stochastic resonance whole-body vibration (SR-WBV) training. Another aim was to evaluate the effect size of one SR-WBV intervention session on Short Physical Performance Battery (SPPB), Expanded Timed Get Up-and-Go (ETGUG), isometric maximal voluntary contraction (IMVC) and rate of force development (IRFD) and chair rising (CR). Randomised double-blinded controlled cross-over pilot study. Feasibility outcomes included recruitment, safety and compliance. For secondary outcomes, SPPB, ETGUG, IMVC, IRFD and CR were measured before and 2-min after intervention. Nonparametric Rank-Order Tests of Puri and Sen L Statistics to Ranked Data were proposed. Wilcoxon signed-ranked tests were used to analyse the differences after SR-WBV intervention and sham intervention. Treatment effects between the interventions were compared by a Mann-Whitney U test. Among 24 eligible frail elderly, 12 agreed to participate and 3 drop out. The adherence was 15 of 24 intervention sessions. For secondary outcome, effect sizes (ES) for SR-WBV intervention on SPPB, ETGUG and CR were determined. This pilot study indicate that the training protocol used in this form for frail elderly individuals is feasible but with modification due to the fact that not all defined feasibility outcomes target was met. SR-WBV with 6 Hz, noise level 4 shows benefit improvements on SPPB (ES 0.52), ETGUG (part sit-to-stand movement: ES 0.81; total time: ES 0.85) and CR (ES 0.66). Further research is desired to determine whether a new adapted training protocol is necessary for SR-WBV in the "skilling up" phase in frail elderly individuals.

  9. Identification for Active Vibration Control of Flexible Structure Based on Prony Algorithm

    National Research Council Canada - National Science Library

    Sheng, Xianjun; Kong, Yuanli; Zhang, Fengyun; Yang, Rui


    .... The modal parameters and transfer function of the system are identified from the step response signal based on Prony algorithm, while the vibration is attenuated by using the input shaping technique...

  10. Effect of pile-driving induced vibrations on nearby structures and other assets. (United States)


    The work described here represents an attempt to understand the mechanisms of energy : transfer from steel H-piles driven with diesel hammers to the surrounding soil and the energy : attenuation through the soil by measuring ground motion vibrations ...

  11. Tunable Passive Vibration Suppressor (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)


    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.

  12. 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-.

  13. Analysis of the effect of ultrasonic vibrations on the performance of micro-electrical discharge machining of A2 tool steel

    DEFF Research Database (Denmark)

    Puthumana, Govindan


    a systematic analysis of the influence of kinetic effects of the ultrasonic vibrations on the material removal rate (MRR) and tool electrode wear rate (TWR). The tool wear ratio was estimated for the process at all processing conditions. The maximum variation in tool wear ratio is observed to be 82%. Therefore......The application of ultrasonic vibrations to a workpiece or tool is a novel hybrid approach in micro-electrical discharge machining. The advantages of this method include effective flushing out of debris, higher machining efficiency and lesser short-circuits during machining. This paper presents...

  14. Sound insulation and vibration tests for lightweight steel framing floors


    Shi, Wanqing; Edfast, Fredrik; Ågren, Anders


    An experimental study of sound insulation and vibrations of lightweight steel framing floors due to different floor construction set up were performed. Floors with 3m, 5m and 7.2m span were tested. The impact and airborne sound insulation for 3m span floor were measured based on ISO 140 in lab condition. Vibration tests were carried out on all three different spans. The vibration transmission loss of the structure was determined from the surface vibration measurements. The fundamental natural...

  15. Analysis of Piezoelectric Actuator for Vibration Control of Composite plate (United States)

    Gomaa, Ahmed R.; Hai, Huang


    Vibration analysis is studied numerically in this paper for a simply supported composite plate subjected to external loadings. Vibrations are controlled by using piezoelectric patches. Finite element method (ANSYS) is used for obtaining finite element model of the smart plate structure, a layered composite plate is manufactured experimentally and tested to obtain the structure mechanical properties. Different piezoelectric patch areas and different applied gain voltage effects on vibration attenuation is studied. The numerical solution is compared with the experimental work, a good agreement achieved.

  16. Diagnostic Performance of MR Elastography and Vibration-controlled Transient Elastography in the Detection of Hepatic Fibrosis in Patients with Severe to Morbid Obesity. (United States)

    Chen, Jun; Yin, Meng; Talwalkar, Jayant A; Oudry, Jennifer; Glaser, Kevin J; Smyrk, Thomas C; Miette, Véronique; Sandrin, Laurent; Ehman, Richard L


    Purpose To evaluate the diagnostic performance and examination success rate of magnetic resonance (MR) elastography and vibration-controlled transient elastography (VCTE) in the detection of hepatic fibrosis in patients with severe to morbid obesity. Materials and Methods This prospective and HIPAA-compliant study was approved by the institutional review board. A total of 111 patients (71 women, 40 men) participated. Written informed consent was obtained from all patients. Patients underwent MR elastography with two readers and VCTE with three observers to acquire liver stiffness measurements for liver fibrosis assessment. The results were compared with those from liver biopsy. Each pathology specimen was evaluated by two hepatopathologists according to the METAVIR scoring system or Brunt classification when appropriate. All imaging observers were blinded to the biopsy results, and all hepatopathologists were blinded to the imaging results. Examination success rate, interobserver agreement, and diagnostic accuracy for fibrosis detection were assessed. Results In this obese patient population (mean body mass index = 40.3 kg/m2; 95% confidence interval [CI]: 38.7 kg/m2, 41.8 kg/m2]), the examination success rate was 95.8% (92 of 96 patients) for MR elastography and 81.3% (78 of 96 patients) or 88.5% (85 of 96 patients) for VCTE. Interobserver agreement was higher with MR elastography than with biopsy (intraclass correlation coefficient, 0.95 vs 0.89). In patients with successful MR elastography and VCTE examinations (excluding unreliable VCTE examinations), both MR elastography and VCTE had excellent diagnostic accuracy in the detection of clinically significant hepatic fibrosis (stage F2-F4) (mean area under the curve: 0.93 [95% CI: 0.85, 0.97] vs 0.91 [95% CI: 0.83, 0.96]; P = .551). Conclusion In this obese patient population, both MR elastography and VCTE had excellent diagnostic performance for assessing hepatic fibrosis; MR elastography was more technically

  17. Vibration of hydraulic machinery

    CERN Document Server

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


    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...

  18. Characterization of pollen by vibrational spectroscopy. (United States)

    Zimmermann, Boris


    Classification, discrimination, and biochemical assignment of vibrational spectra of pollen samples belonging to 43 different species of the order Pinales has been made using three different vibrational techniques. The comparative study of transmission (KBr pellet) and attenuated total reflection (ATR) Fourier transform infrared (FT-IR) and FT-Raman spectroscopies was based on substantial variability of pollen grain size, shape, and relative biochemical composition. Depending on the penetration depth of the probe light, vibrational techniques acquire predominant information either on pollen grain walls (FT-Raman and ATR-FT-IR) or intracellular material (transmission FT-IR). Compared with the other two methods, transmission FT-IR obtains more comprehensive information and as a result achieves superior spectral identification and discrimination of pollen. The results strongly indicate that biochemical similarities of pollen grains belonging to the same plant genus or family lead to similar features in corresponding vibrational spectra. The exploitation of that property in aerobiological monitoring was demonstrated by simple and rapid pollen identification based on relatively small spectral libraries, with the same (or better) taxonomic resolution as that provided by optical microscopy. Therefore, the clear correlation between vibrational spectra and pollen grain morphology, biochemistry, and taxonomy is obtained, while successful pollen identification illustrates the practicability of such an approach in environmental studies.

  19. Review of magnetostrictive vibration energy harvesters (United States)

    Deng, Zhangxian; Dapino, Marcelo J.


    The field of energy harvesting has grown concurrently with the rapid development of portable and wireless electronics in which reliable and long-lasting power sources are required. Electrochemical batteries have a limited lifespan and require periodic recharging. In contrast, vibration energy harvesters can supply uninterrupted power by scavenging useful electrical energy from ambient structural vibrations. This article reviews the current state of vibration energy harvesters based on magnetostrictive materials, especially Terfenol-D and Galfenol. Existing magnetostrictive harvester designs are compared in terms of various performance metrics. Advanced techniques that can reduce device size and improve performance are presented. Models for magnetostrictive devices are summarized to guide future harvester designs.

  20. Field Balancing and Harmonic Vibration Suppression in Rigid AMB-Rotor Systems with Rotor Imbalances and Sensor Runout. (United States)

    Xu, Xiangbo; Chen, Shao


    Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously.

  1. Probiotic Streptococcus thermophilus FP4 and Bifidobacterium breve BR03 Supplementation Attenuates Performance and Range-of-Motion Decrements Following Muscle Damaging Exercise

    Directory of Open Access Journals (Sweden)

    Ralf Jäger


    Full Text Available Probiotics have immunomodulatory effects. However, little is known about the potential benefit of probiotics on the inflammation subsequent to strenuous exercise. In a double-blind, randomized, placebo controlled, crossover design separated by a 21-day washout, 15 healthy resistance-trained men ingested an encapsulated probiotic Streptococcus (S. thermophilus FP4 and Bifidobacterium (B. breve BR03 at 5 bn live cells (AFU concentration each, or a placebo, daily for 3 weeks prior to muscle-damaging exercise ( NCT02520583. Isometric strength, muscle soreness, range of motion and girth, and blood interleukin-6 (IL-6 and creatine kinase (CK concentrations were measured from pre- to 72 h post-exercise. Statistical analysis was via mixed models and magnitude-based inference to the standardized difference. Probiotic supplementation resulted in an overall decrease in circulating IL-6, which was sustained to 48 h post-exercise. In addition, probiotic supplementation likely enhanced isometric average peak torque production at 24 to 72 h into the recovery period following exercise (probiotic–placebo point effect ±90% CI: 24 h, 11% ± 7%; 48 h, 12% ± 18%; 72 h, 8% ± 8%. Probiotics also likely moderately increased resting arm angle at 24 h (2.4% ± 2.0% and 48 h (1.9% ± 1.9% following exercise, but effects on soreness and flexed arm angle and CK were unclear. These data suggest that dietary supplementation with probiotic strains S. thermophilus FP4 and B. breve BR03 attenuates performance decrements and muscle tension in the days following muscle-damaging exercise.

  2. Development of a multi-degree-of-freedom micropositioning, vibration isolation and vibration suppression system (United States)

    Jaensch, M.; Lampérth, M. U.


    This paper describes the design and performance testing of a micropositioning, vibration isolation and suppression system, which can be used to position a piece of equipment with sub-micrometre accuracy and stabilize it against various types of external disturbance. The presented demonstrator was designed as part of a novel extremely open pre-polarization magnetic resonance imaging (MRI) scanner. The active control system utilizes six piezoelectric actuators, wide-bandwidth optical fibre displacement sensors and a very fast digital field programmable gate array (FPGA) controller. A PID feedback control algorithm with emphasis on a very high level of integral gain is employed. Due to the high external forces expected, the whole structure is designed to be as stiff as possible, including a novel hard mount approach with parallel passive damping for the suspension of the payload. The performance of the system is studied theoretically and experimentally. The sensitive equipment can be positioned in six degrees of freedom with an accuracy of ± 0.2 µm. External disturbances acting on the support structure or the equipment itself are attenuated in three degrees of freedom by more than -20 dB within a bandwidth of 0-200 Hz. Excellent impulse rejection and input tracking are demonstrated as well.

  3. Attenuation measuring ultrasound shearwave elastography and in vivo application in post-transplant liver patients (United States)

    Nenadic, Ivan Z.; Qiang, Bo; Urban, Matthew W.; Zhao, Heng; Sanchez, William; Greenleaf, James F.; Chen, Shigao


    Ultrasound and magnetic resonance elastography techniques are used to assess mechanical properties of soft tissues. Tissue stiffness is related to various pathologies such as fibrosis, loss of compliance, and cancer. One way to perform elastography is measuring shear wave velocity of propagating waves in tissue induced by intrinsic motion or an external source of vibration, and relating the shear wave velocity to tissue elasticity. All tissues are inherently viscoelastic and ignoring viscosity biases the velocity-based estimates of elasticity and ignores a potentially important parameter of tissue health. We present attenuation measuring ultrasound shearwave elastography (AMUSE), a technique that independently measures both shear wave velocity and attenuation in tissue and therefore allows characterization of viscoelasticity without using a rheological model. The theoretical basis for AMUSE is first derived and validated in finite element simulations. AMUSE is validated against the traditional methods for assessing shear wave velocity (phase gradient) and attenuation (amplitude decay) in tissue mimicking phantoms and excised tissue. The results agreed within one standard deviation. AMUSE was used to measure shear wave velocity and attenuation in 15 transplanted livers in patients with potential acute rejection, and the results were compared with the biopsy findings in a preliminary study. The comparison showed excellent agreement and suggests that AMUSE can be used to separate transplanted livers with acute rejection from livers with no rejection.

  4. Attenuation measuring ultrasound shearwave elastography and in vivo application in post-transplant liver patients. (United States)

    Nenadic, Ivan Z; Qiang, Bo; Urban, Matthew W; Zhao, Heng; Sanchez, William; Greenleaf, James F; Chen, Shigao


    Ultrasound and magnetic resonance elastography techniques are used to assess mechanical properties of soft tissues. Tissue stiffness is related to various pathologies such as fibrosis, loss of compliance, and cancer. One way to perform elastography is measuring shear wave velocity of propagating waves in tissue induced by intrinsic motion or an external source of vibration, and relating the shear wave velocity to tissue elasticity. All tissues are inherently viscoelastic and ignoring viscosity biases the velocity-based estimates of elasticity and ignores a potentially important parameter of tissue health. We present attenuation measuring ultrasound shearwave elastography (AMUSE), a technique that independently measures both shear wave velocity and attenuation in tissue and therefore allows characterization of viscoelasticity without using a rheological model. The theoretical basis for AMUSE is first derived and validated in finite element simulations. AMUSE is validated against the traditional methods for assessing shear wave velocity (phase gradient) and attenuation (amplitude decay) in tissue mimicking phantoms and excised tissue. The results agreed within one standard deviation. AMUSE was used to measure shear wave velocity and attenuation in 15 transplanted livers in patients with potential acute rejection, and the results were compared with the biopsy findings in a preliminary study. The comparison showed excellent agreement and suggests that AMUSE can be used to separate transplanted livers with acute rejection from livers with no rejection.

  5. Bevel Gearbox Fault Diagnosis using Vibration Measurements

    Directory of Open Access Journals (Sweden)

    Hartono Dennis


    Full Text Available The use of vibration measurementanalysis has been proven to be effective for gearbox fault diagnosis. However, the complexity of vibration signals observed from a gearbox makes it difficult to accurately detectfaults in the gearbox. This work is based on a comparative studyof several time-frequency signal processing methods that can be used to extract information from transient vibration signals containing useful diagnostic information. Experiments were performed on a bevel gearbox test rig using vibration measurements obtained from accelerometers. Initially, thediscrete wavelet transform was implementedfor vibration signal analysis to extract the frequency content of signal from the relevant frequency region. Several time-frequency signal processing methods werethen incorporated to extract the fault features of vibration signals and their diagnostic performances were compared. It was shown thatthe Short Time Fourier Transform (STFT could not offer a good time resolution to detect the periodicity of the faulty gear tooth due the difficulty in choosing an appropriate window length to capture the impulse signal. The Continuous Wavelet Transform (CWT, on the other hand, was suitable to detection of vibration transients generated by localized fault from a gearbox due to its multi-scale property. However, both methods still require a thorough visual inspection. In contrast, it was shown from the experiments that the diagnostic method using the Cepstrumanalysis could provide a direct indication of the faulty tooth without the need of a thorough visual inspection as required by CWT and STFT.

  6. Pressure surge attenuator (United States)

    Christie, Alan M.; Snyder, Kurt I.


    A pressure surge attenuation system for pipes having a fluted region opposite crushable metal foam. As adapted for nuclear reactor vessels and heads, crushable metal foam is disposed to attenuate pressure surges.

  7. Vibration for Pain Reduction in a Plastic Surgery Clinic. (United States)

    Eichhorn, Mitchell George; Karadsheh, Murad Jehad; Krebiehl, Johanna Ruth; Ford, Dawn Marie; Ford, Ronald D


    Patients can experience significant pain during routine procedures in the plastic surgery clinic. Methods for clinical pain reduction are often impractical, time-consuming, or ineffective. Vibration is a safe, inexpensive, and highly applicable modality for pain reduction that can be readily utilized for a wide variety of procedures. This study evaluated the use of vibration as a viable pain-reduction strategy in the clinical plastic surgery setting. Patients requiring at least 2 consecutive procedures that are considered painful were enrolled in the study. These included injections, staple removal, and suture removal. In the same patient, one half of the procedures were performed without vibration and the other half with vibration. After completing the procedures, the patients rated their pain with vibration and without vibration. The patient and the researcher also described the experience with a short questionnaire. Twenty-eight patients were enrolled in the study. Patients reported significantly less pain on the Numeric Rating Scale pain scale when vibration was used compared with the control group (p vibration and 1.93 with vibration, and vibration with injections resulted in the greatest improvement. Eighty-six percent of the patients claimed that vibration significantly reduced their pain. Vibration is an effective method of pain reduction. It significantly reduces the pain experienced by patients during minor office procedures. Given its practicality and ease of use, it is a welcome tool in the plastic surgery clinic.

  8. Research on Effects of Blast Casting Vibration and Vibration Absorption of Presplitting Blasting in Open Cast Mine

    Directory of Open Access Journals (Sweden)

    Li Ma


    Full Text Available The impact energy produced by blast casting is able to break and cast rocks, yet the strong vibration effects caused at the same time would threaten the safety of mines. Based on the theory of Janbu’s Limit Equilibrium Method (LEM, pseudo-static method has been incorporated to analyze the influence of dynamic loads of blasting on slope stability. The horizontal loads produced by blast vibrations cause an increase in sliding forces, and this leads to a lower slope stability coefficient. When the tensile stresses of the two adjacent blast holes are greater than the tensile strength of rock mass, the radical oriented cracks are formed, which is the precondition for the formation of presplit face. Thus, the formula for calculating the blast hole spacing of presplit blasting can be obtained. Based on the analysis of the principles of vibration tester and vibration pick-up in detecting blast vibrations, a detection scheme of blast vibration is worked out by taking the blast area with precrack rear and non-precrack side of the detection object. The detection and research results of blast vibration show that presplit blasting can reduce the attenuation coefficient of stress wave by half, and the vibration absorption ratio could reach 50.2%; the impact of dynamic loads on the end-wall slope stability coefficient is 1.98%, which proves that presplit blasting plays an important role in shock absorption of blast casting.

  9. Damage monitoring and impact detection using optical fiber vibration sensors (United States)

    Yang, Y. C.; Han, K. S.


    Intensity-based optical fiber vibrations sensors (OFVSs) are used in damage monitoring of fiber-reinforced plastics, in vibration sensing, and location of impacts. OFVSs were constructed by placing two cleaved fiber ends in a capillary tube. This sensor is able to monitor structural vibrations. For vibration sensing, the optical fiber sensor was mounted on the carbon fiber reinforced composite beam, and its response was investigated for free and forced vibration. For locating impact points, four OFVSs were placed at chosen positions and the different arrival times of impact-generated vibration signals were recorded. The impact location can be determined from these time delays. Indentation and tensile tests were performed with the measurement of the optical signal and acoustic emission (AE). The OFVSs accurately detected both free and forced vibration signals. Accurate locations of impact were determined on an acrylate plate. It was found that damage information, comparable in quality to AE data, could be obtained from the OFVS signals.

  10. Vibration Transmission in a Multi-Storey Lightweight Building

    DEFF Research Database (Denmark)

    Niu, Bin; Andersen, Lars Vabbersgaard; Kiel, Nikolaj


    This paper develops a parametric modelling and analysis approach to investigate the vibration transmission in lightweight buildings. The main focus of the research is to investigate the influence of geometry and configuration of the building on the vibration transmission. A building with a single...... the modelling of different connections between panels in the building [2]. Using this parametric building model, free vibration analysis is first performed to obtain the distribution of Eigen frequencies of the building. Then the forced vibration of the building subjected to a mechanical excitation is analysed...... to investigate the transmission of vibration. The influence of different excitation frequencies on the vibration transmission is studied and discussed. The vibration response in two different receiving rooms, one near the source and one far from the source, is illustrated and discussed for the various geometric...

  11. Model Indepedent Vibration Control


    Yuan, Jing


    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

  12. 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...

  13. 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...

  14. Hydroelastic Vibrations of Ships

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher; Folsø, Rasmus


    A formula for the necessary hull girder bending stiffness required to avoid serious springing vibrations is derived. The expression takes into account the zero crossing period of the waves, the ship speed and main dimensions. For whipping vibrations the probability of exceedance for the combined...

  15. Gearbox vibration diagnostic analyzer (United States)


    This report describes the Gearbox Vibration Diagnostic Analyzer installed in the NASA Lewis Research Center's 500 HP Helicopter Transmission Test Stand to monitor gearbox testing. The vibration of the gearbox is analyzed using diagnostic algorithms to calculate a parameter indicating damaged components.

  16. Mechanical vibration and shock analysis, sinusoidal vibration

    CERN Document Server

    Lalanne, Christian


    Everything engineers need to know about mechanical vibration and 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

  17. Effect of iTonic whole-body vibration on delayed-onset muscle soreness among untrained individuals. (United States)

    Rhea, Matthew R; Bunker, Derek; Marín, Pedro J; Lunt, Kregg


    Attempts to reduce or eliminate delayed-onset of muscle soreness are important as this condition is painful and debilitating. The purpose of this study was to examine the effectiveness of whole-body vibration (WBV) massage and stretching exercises at reducing perceived pain among untrained men. Sixteen adult men (age, 36.6 +/- 2.1 yr) volunteered to perform a strenuous exercise session consisting of resistance training and repeated sprints. Subjects were randomly assigned to 1 of 2 recovery groups: a group performing WBV stretching sessions or a stretching group performing static stretching without vibration. Both groups performed similar stretches, twice per day for 3 days after the workout. The vibration group performed their stretches on the iTonic platform (frequency, 35 Hz; amplitude, 2 mm). Perceived pain was measured at 12, 24, 48, and 72 hours postworkout. Statistical analyses identified a significantly lower level of reported perceived pain at all postworkout measurement times among the WBV group (p time. The degree of attenuation of pain ranged from 22-61%. These data suggest that incorporating WBV as a recovery/regeneration tool may be effective for reducing the pain of muscle soreness and tightness after strenuous training.

  18. Vibrations of rotating machinery

    CERN Document Server

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


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

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

    DEFF Research Database (Denmark)

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


    be introduced by periodic inclusions or changes to the ground surface geometry. However, for vibration mitigation in the context of real civil-engineering problems related to ground-borne noise from railways, for example, the excitation is not strictly harmonic and a steady state of the response is usually......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...

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

    CERN Document Server

    Cremer, L; Petersson, Björn AT


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

  1. Simulation study of MEMS piezoelectric vibration energy harvester based on c-axis tilted AlN thin film for performance improvement

    Directory of Open Access Journals (Sweden)

    Lingfeng Kong


    Full Text Available In this paper, a MEMS piezoelectric cantilevered vibration energy harvester based on c-axis tilted AlN thin film is investigated. Based on basic piezoelectric equations and static analysis of cantilever beam, the equations for generated energy (E and open circuit voltage (Vo were derived, and simulations were carried out to study the effects of geometry parameters and c-axis tilted angle. Results show that E and Vo of energy harvesters are greatly dependent on c-axis tilted angle and geometry parameters, while the coupling between c-axis tilted angle and geometry parameters is not strong. For a given structure size, E and Vo can be almost simultaneously improved by controlling c-axis tilted angle; compared with the case of normal c-axis angle, E with optimal c-axis tilted angle can be amplified by more than 3 times, and the Vo is amplified by about 2 times. E or Vo could be further improved by geometry parameters, while there is trade-off between them. These results can be used for the design and application of piezoelectric cantilevered vibration energy harvester.

  2. Simulation study of MEMS piezoelectric vibration energy harvester based on c-axis tilted AlN thin film for performance improvement (United States)

    Kong, Lingfeng; Zhang, Jinhui; Wang, Huiyuan; Ma, Shenglin; Li, Fang; Wang, Qing-Ming; Qin, Lifeng


    In this paper, a MEMS piezoelectric cantilevered vibration energy harvester based on c-axis tilted AlN thin film is investigated. Based on basic piezoelectric equations and static analysis of cantilever beam, the equations for generated energy (E) and open circuit voltage (Vo) were derived, and simulations were carried out to study the effects of geometry parameters and c-axis tilted angle. Results show that E and Vo of energy harvesters are greatly dependent on c-axis tilted angle and geometry parameters, while the coupling between c-axis tilted angle and geometry parameters is not strong. For a given structure size, E and Vo can be almost simultaneously improved by controlling c-axis tilted angle; compared with the case of normal c-axis angle, E with optimal c-axis tilted angle can be amplified by more than 3 times, and the Vo is amplified by about 2 times. E or Vo could be further improved by geometry parameters, while there is trade-off between them. These results can be used for the design and application of piezoelectric cantilevered vibration energy harvester.

  3. Biobjective Optimization of Vibration Performance of Steel-Spring Floating Slab Tracks by Four-Pole Parameter Method Coupled with Ant Colony Optimization

    Directory of Open Access Journals (Sweden)

    Hao Jin


    Full Text Available Steel-spring floating slab tracks are one of the most effective methods to reduce vibrations from underground railways, which has drawn more and more attention in scientific communities. In this paper, the steel-spring floating slab track located in Track Vibration Abatement and Control Laboratory was modeled with four-pole parameter method. The influences of the fastener damping ratio, the fastener stiffness, the steel-spring damping ratio, and the steel-spring stiffness were researched for the rail displacement and the foundation acceleration. Results show that the rail displacement and the foundation acceleration will decrease with the increase of the fastener stiffness or the steel-spring damping ratio. However, the rail displacement and the foundation acceleration have the opposite variation tendency for the fastener damping ratio and the steel-spring stiffness. In order to optimize the rail displacement and the foundation acceleration affected by the fastener damping ratio and the steel-spring stiffness at the same time, a multiobjective ant colony optimization (ACO was employed. Eventually, Pareto optimal frontier of the rail displacement and the foundation acceleration was derived. Furthermore, the desirable values of the fastener damping ratio and the steel-spring stiffness can be obtained according to the corresponding Pareto optimal solution set.

  4. Vibrations and alternated stresses in turbomachineries; Vibrations et contraintes alternees dans les turbomachines

    Energy Technology Data Exchange (ETDEWEB)

    Naudin, M. [Conservatoire National des Arts et Metiers (CNAM), 75 - Paris (France)]|[FRAMATOME, 92 - Paris-La-Defense (France); Pugnet, J.M. [Conservatoire National des Arts et Metiers (CNAM), Grenoble-1 Univ., 38 (France)]|[FRAMATOME, 92 - Paris-La-Defense (France)


    Vibration phenomena are sources of mechanical incidents in turbomachineries. A calculation of the Eigenmodes of machine parts and a knowledge of their possible excitation during the machine operation can greatly improve the reliability and availability of the equipments. The development of computer tools and in particular the use of finite-element codes has allowed a more and more precise calculation of Eigenmodes and Eigenfrequencies. However, the analysis of excitation sources remains sometimes insufficient to explain and anticipate some complex vibrational phenomena encountered in rotative machines. The aim of this paper is to present, using two different examples, the methodology to be used in order to perform a complete vibrational analysis of mechanical components. The following aspects are reviewed successively: 1 - the damped vibrational system: study of the free motion, study of the response to an harmonic forced excitation; 2 - vibrational analysis of turbine blades: steam turbine blades, Eigenmodes of mobile blades, excitation sources, Campbell diagram, calculation of static and dynamical stresses, Haigh diagram, acceptance criteria and safety coefficient, influence of corrosion; 3 - dynamical analysis of the bending of a lineshaft: different flexion Eigenmodes, stiffness and damping of bearings, calculation of flexion Eigenmodes, excitation sources, vibrational stability of the lineshaft and vibration level; 3 - generalization: vibration of blades, shaft dynamics, alternative machines. (J.S.) 10 refs.

  5. Controlled attenuation parameter (CAP): a novel VCTE™ guided ultrasonic attenuation measurement for the evaluation of hepatic steatosis: preliminary study and validation in a cohort of patients with chronic liver disease from various causes. (United States)

    Sasso, Magali; Beaugrand, Michel; de Ledinghen, Victor; Douvin, Catherine; Marcellin, Patrick; Poupon, Raoul; Sandrin, Laurent; Miette, Véronique


    There is a need for noninvasive methods to detect liver steatosis, which can be a factor of liver fibrosis progression. This work aims to evaluate a novel ultrasonic controlled attenuation parameter (CAP) devised to target, specifically, liver steatosis using a sophisticated process based on vibration control transient elastography (VCTE™). CAP was first validated as an estimate of ultrasonic attenuation at 3.5 MHz using Field II simulations and tissue-mimicking phantoms. Performance of the CAP was then appraised on 115 patients, taking the histological grade of steatosis as reference. CAP was significantly correlated to steatosis (Spearman ρ = 0.81, p CAP can efficiently separate several steatosis grades. These promising results suggest that CAP is a noninvasive, immediate, objective and efficient method to detect and quantify steatosis. Copyright © 2010 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  6. 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)


    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.

  7. A fuzzy robust control scheme for vibration suppression of a nonlinear electromagnetic-actuated flexible system (United States)

    Tavakolpour-Saleh, A. R.; Haddad, M. A.


    In this paper, a novel robust vibration control scheme, namely, one degree-of-freedom fuzzy active force control (1DOF-FAFC) is applied to a nonlinear electromagnetic-actuated flexible plate system. First, the flexible plate with clamped-free-clamped-free (CFCF) boundary conditions is modeled and simulated. Then, the validity of the simulation platform is evaluated through experiment. A nonlinear electromagnetic actuator is developed and experimentally modeled through a parametric system identification scheme. Next, the obtained nonlinear model of the actuator is applied to the simulation platform and performance of the proposed control technique in suppressing unwanted vibrations is investigated via simulation. A fuzzy controller is applied to the robust 1DOF control scheme to tune the controller gain using acceleration feedback. Consequently, an intelligent self-tuning vibration control strategy based on an inexpensive acceleration sensor is proposed in the paper. Furthermore, it is demonstrated that the proposed acceleration-based control technique owns the benefits of the conventional velocity feedback controllers. Finally, an experimental rig is developed to investigate the effectiveness of the 1DOF-FAFC scheme. It is found that the first, second, and third resonant modes of the flexible system are attenuated up to 74%, 81%, and 90% respectively through which the effectiveness of the proposed control scheme is affirmed.

  8. Reducing cross-flow vibrations of underflow gates: experiments and numerical studies

    CERN Document Server

    Erdbrink, C D; Sloot, P M A


    An experimental study is combined with numerical modelling to investigate new ways to reduce cross-flow vibrations of hydraulic gates with underflow. A rectangular gate section placed in a flume was given freedom to vibrate in the vertical direction. Holes in the gate bottom enabled leakage flow through the gate to enter the area directly under the gate which is known to play a key role in most excitation mechanisms. For submerged discharge conditions with small gate openings the vertical dynamic support force was measured in the reduced velocity range 1.5 < Vr < 10.5 for a gate with and without holes. The leakage flow through the holes significantly reduced vibrations. This attenuation was most profound in the high stiffness region at 2 < Vr < 3.5. Two-dimensional numerical simulations were performed with the Finite Element Method to assess local velocities and pressures for both gate types. A moving mesh covering both solid and fluid domain allowed free gate movement and two-way fluid-structure ...

  9. Development of linear and nonlinear hand-arm vibration models using optimization and linearization techniques. (United States)

    Rakheja, S; Gurram, R; Gouw, G J


    Hand-arm vibration (HAV) models serve as an effective tool to assess the vibration characteristics of the hand-tool system and to evaluate the attenuation performance of vibration isolation mechanisms. This paper describes a methodology to identify the parameters of HAV models, whether linear or nonlinear, using mechanical impedance data and a nonlinear programming based optimization technique. Three- and four-degrees-of-freedom (DOF) linear, piecewise linear and nonlinear HAV models are formulated and analyzed to yield impedance characteristics in the 5-1000 Hz frequency range. A local equivalent linearization algorithm, based upon the principle of energy similarity, is implemented to simulate the nonlinear HAV models. Optimization methods are employed to identify the model parameters, such that the magnitude and phase errors between the computed and measured impedance characteristics are minimum in the entire frequency range. The effectiveness of the proposed method is demonstrated through derivations of models that correlate with the measured X-axis impedance characteristics of the hand-arm system, proposed by ISO. The results of the study show that a linear model cannot predict the impedance characteristics in the entire frequency range, while a piecewise linear model yields an accurate estimation.

  10. Long-range vibration sensor based on correlation analysis of optical frequency-domain reflectometry signals. (United States)

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


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

  11. Kappa Delta Award. Low back pain and whole body vibration. (United States)

    Pope, M H; Magnusson, M; Wilder, D G


    The investigators describe their multifaceted approach to the study of the relationship between whole body vibration and low back pain. The epidemiologic study was a two center study of drivers and sedentary workers in the United States and Sweden. The vibration exposure was measured in the vehicles. It was found that the career vibration exposure was related to low back, neck, and shoulder pain. However, disability was related to job satisfaction. In vivo experiments, using percutaneous pin mounted accelerometers have shown that the natural frequency is at 4.5 Hz. The frequency response is affected by posture, seating, and seat back inclination. The response appears to be determined largely by the rocking of the pelvis. Electromyographic studies have shown that muscle fatigue occurs under whole body vibration. After whole body vibration exposure the muscle response to a sudden load has greater latency. Vehicle driving may be a reason for low back pain or herniated nucleus pulposus. Prolonged seating exposure, coupled with the whole body vibration, should be reduced for those recovering from these problems. Vibration attenuating seats and correct ergonomic layout of the cabs may reduce the risks of recurrence.

  12. Ground motion attenuation during M 7.1 Darfield and M 6.2 Christchurch, New Zealand, earthquakes and performance of global Ppedictive models (United States)

    Segou, Margaret; Kalkan, Erol


    fault with M 6.2, followed by a second event (M 6.9), releasing the largest portion of the energy on the right-lateral Greendale fault. The third sub-event (M 5.7) is due to a reverse fault with a right-lateral component (Holden et al. 2011). The Christchurch earthquake occurred on an oblique thrust fault. The comparison of spectral acceleration values at stations near Christchurch reveals that the second event produced much larger amplitudes of shaking than the Darfield event due to its proximity to the epicenter. Both events resulted in noticeably large amplitudes of the vertical motion, often exceeding horizontal motion in the near-fault area. The vertical motions, showing asymmetric acceleration traces and pulses, reached 1.26 g during the Darfield earthquake and 2.2 g during the Christchurch event. These events were recorded by more than 100 strong motion stations operated by the Institute of Geological and Nuclear Sciences ( Using the processed data from these stations, peak ground acceleration (PGA) and 5%-damped spectral acceleration values at 0.3, 1, and 3 s are used for performance evaluation of the global ground motion predictive equations (GMPEs). The selected GMPEs are the Next Generation Attenuation (NGA) models of Abrahamson and Silva (2008), Boore and Atkinson (2008), Campbell and Bozorgnia (2008), and Chiou and Youngs (2008). The Graizer and Kalkan (2007, 2009) model, which is based on the NGA project database, is also included. These GMPEs are abbreviated respectively as AS08, BA08, CB08, CY08, and GK07. Because they have been used widely for seismic hazard analysis for crustal earthquakes, their performance assessment becomes a critical issue especially for immediate response and recovery planning after major events. The occurrence of aftershocks similar to the Christchurch event will most probably control seismic hazard in the broader area, as confirmed by the recent M 6.0 event on June 13, 2011.

  13. 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....

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

    Directory of Open Access Journals (Sweden)

    Bin Deng


    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.

  15. Vibrational circular dichroism spectroscopy of a spin-triplet bis-(biuretato) cobaltate(III) coordination compound with low-lying electronic transitions

    DEFF Research Database (Denmark)

    Johannessen, Christian; Thulstrup, Peter W.


    Vibrational absorption (VA) and vibrational circular dichroism (VCD) spectroscopy was applied in the analysis of vibrational and low lying electronic transitions of a triplet ground state cobalt(III) coordination compound. The spectroscopic measurements were performed on the tetrabutylammonium salt...

  16. Vibration Analysis and the Accelerometer (United States)

    Hammer, Paul


    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…

  17. [Evaluation of forklift trucks operated in dockyards for reducing exposure to whole-body vibration]. (United States)

    Tsujimura, Hiroji; Taoda, Kazushi; Nishiyama, Katsuo


    Our preceding study revealed that many fork-lift truck drivers in Japanese dockyards suffer from fatigue symptoms such as low back pain (LBP). It has been suggested that exposure to whole-body vibration (WBV) is a cause of their LBP. Using forklift models manufactured from 1982 to 2000, we measured and evaluated the vibration of forklift trucks operated in dockyards, adopting experimental procedures based on the European Standard. We investigated various factors related to WBV, with the main focus on attenuating seat vibration. This study showed that (1) the seats did not attenuate vibration in the vertical direction, (2) forklift trucks and their seats had not improved in terms of WBV attenuation for a decade, (3) some forklift trucks in which the seat suspension could no longer be adjusted to the driver's weight continued to be used without being repaired, and impractical seat adjustment methods were adopted, and (4) the seats did not attenuate vertical vibration well in the most undesirable frequency range. We conclude that forklift trucks and especially their seats should urgently be improved with regard to WBV attenuation in order to prevent LBP in forklift truck drivers.

  18. 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...... phenomena and work with advanced tools such as perturbation analysis and bifurcation analysis. Explaining theory in terms of relevant examples from real systems, this book is user-friendly and meets the increasing interest in non-linear dynamics in mechanical/structural engineering and applied mathematics...

  19. Vibrational spectroscopy in the electron microscope. (United States)

    Krivanek, Ondrej L; Lovejoy, Tracy C; Dellby, Niklas; Aoki, Toshihiro; Carpenter, R W; Rez, Peter; Soignard, Emmanuel; Zhu, Jiangtao; Batson, Philip E; Lagos, Maureen J; Egerton, Ray F; Crozier, Peter A


    Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample--that is, for 'aloof' spectroscopy that largely avoids radiation damage.

  20. Effects of vibration on flexibility: a meta-analysis. (United States)

    Osawa, Y; Oguma, Y


    Exogenous stimulation of skeletal muscle or tendon is often used to improve range of motion. Despite substantial research efforts, however, the effects of vibration on flexibility have not been clarified. In this review, we investigated the effects of acute and chronic intervention programs which used vibration to improve flexibility in young healthy individuals. Effect size was calculated using data from a total of 600 participants in 19 studies before and after the introduction of vibration-based intervention, and a total of 324 participants in 13 studies on the additive effects of vibration compared with the identical conditions without vibration. Sub-group analyses were performed based on intervention period, type of exercise, and type of vibration. Meta-analysis showed that vibration interventions had significant effects on flexibility (standardized mean difference [SMD]=-0.79, 95% confidence interval [CI]=-1.14- -0.43; panalysis revealed a significant additive effect of vibration on flexibility compared with the identical condition without vibration (SMD=0.25, 95%CI=0.03-0.48; P=0.03), with small heterogeneity (I(2)=0%). The risk of publication bias was low judged from Kendall's τ statistic. We concluded that the use of vibration might lead to additive improvements in flexibility.

  1. A multi-ingredient containing carbohydrate, proteins L-glutamine and L-carnitine attenuates fatigue perception with no effect on performance, muscle damage or immunity in soccer players. (United States)

    Naclerio, Fernando; Larumbe-Zabala, Eneko; Cooper, Robert; Allgrove, Judith; Earnest, Conrad P


    We investigated the effects of ingesting a multi-ingredient (53 g carbohydrate, 14.5 g whey protein, 5 g glutamine, 1.5 g L-carnitine-L-tartrate) supplement, carbohydrate only, or placebo on intermittent performance, perception of fatigue, immunity, and functional and metabolic markers of recovery. Sixteen amateur soccer players ingested their respective treatments before, during and after performing a 90-min intermittent repeated sprint test. Primary outcomes included time for a 90-min intermittent repeated sprint test (IRS) followed by eleven 15 m sprints. Measurements included creatine kinase, myoglobin, interleukine-6, Neutrophil; Lymphocytes and Monocyte before (pre), immediately after (post), 1 h and 24 h after exercise testing period. Overall, time for the IRS and 15 m sprints was not different between treatments. However, the perception of fatigue was attenuated (Pcarbohydrate (17.0±1.9) condition. Several changes in immune/inflammatory indices were noted as creatine kinase peaked at 24 h while Interleukin-6 and myoglobin increased both immediately after and at 1 h compared with baseline (PCarbohydrate also elicited lower neutrophil concentrations vs. multi-ingredient (3.9±1.5 10(9)/L vs. 4.9±1.8 10(9)/L, P = 0.016) and a reduced (Pcarbohydrate supplements did not improve intermittent performance, inflammatory or immune function. However, both treatments did attenuate serum myoglobin, while only carbohydrate blunted post-exercise leukocytosis.

  2. Design and Performance Assessment of a Semi-Active Suspension Model of Tractor Cabin

    Directory of Open Access Journals (Sweden)

    I Ahmadi


    Full Text Available Cumulative effect of transmitted vibrations to the tractor driver not only leads to driver health problems, but also reduces the driver working efficiency. Tractor suspension system is one of the methods which is employed to lower the level of transmitted vibrations to the driver. In this study the design and performance assessment of a semi-active suspension model of tractor cabin was considered. Tractor full vibration model was developed first, and subsequently a semi-active ON-OFF damper model was designed. The examination of the model indicated that doubling the piston area and the volume of hydraulic accumulator air chamber, led to 39% increase and 31% reduction of the resonance frequency of transmitted vibrations to the driver, respectively. On the other hand doubling the piston area and the primary air pressure of the accumulator, affected the RMS of transmitted vibration to the driver by 77 cm s-2 reduction and 66 cm s-2 increase, respectively. Moreover, the numerical comparison of the model outputs with and without activation of semi-active cabin suspension, while the model was stimulated with the same input function, led to 43% improvement in RMS acceleration of the transmitted vibrations to the tractor seat. Therefore, the designed semi-active suspension model of cabin was able to attenuate the level of transmitted vibrations to the tractor driver.

  3. Spectroscopy of Vibrational States in Diatomic Iodine Molecules (United States)

    Mulholland, Mary; Harrill, Charles H.; Smith, R. Seth


    This project is focused on understanding the vibrational structure of iodine, which is a homonuclear diatomic molecule. A 20 mW, 532 nm cw diode laser was used to selectively excite neutral iodine molecules to a higher energy electronic state. By performing spectroscopy on the transitions from this state to a lower energy electronic state, the data only showed those vibrational bands which connect the two electronic states. Since a number of vibrational levels are populated in the higher energy electronic state, the transitions to all of the allowed vibrational levels in the lower energy electronic state provided sufficient data to determine the vibrational structures of both states. Emission spectra were collected with an Ocean Optics USB4000 Compact CCD Spectrometer. The spectrometer had a range of 500 - 770 nm with a resolution of approximately 0.5 nm and was sensitive enough to resolve the vibrational states in diatomic iodine molecules. The results were compared to a simple harmonic oscillator model.

  4. Noise and Vibration Modeling for Anti-Lock Brake Systems (United States)

    Zhan, Wei

    A new methodology is proposed for noise and vibration analysis for Anti-Lock Brake Systems (ABS). First, a correlation between noise and vibration measurement data and simulation results need to be established. This relationship allows the engineers to focus on modeling and simulation instead of noise and vibration testing. A comprehensive ABS model is derived for noise and vibration study. The model can be set up to do different types of simulations for noise and vibration analysis. If some data is available from actual testing, then the test data can be easily imported into the model as an input to replace the corresponding part in the model. It is especially useful when the design needs to be modified, or trade-off between ABS performance and noise and vibration is necessary. The model can greatly reduce the time to market for ABS products. It also makes system level optimization possible.

  5. Damping Estimation Using Free Decays and Ambient Vibration Tests

    DEFF Research Database (Denmark)

    Magalhães, Filipe; Brincker, Rune; Cunha, Álvaro


    The accurate identification of modal damping ratios of Civil Engineering structures is a subject of major importance, as the amplitude of structural vibrations in resonance is inversely proportional to these coefficients. Their experimental identification can be performed either from ambient...... vibration or from free vibration tests. In the last case, the structural response after application of an impulse or after the application of harmonic loads can be used. Ambient vibration tests have the strong advantage of being more practical and economical. However, recent applications of both approaches...

  6. An experimental and statistical study of the behavior of the vibration field in two coupled lightweight wooden joist floors

    DEFF Research Database (Denmark)

    Sjökvist, Lars-Göran; Brunskog, Jonas


    The aim of this study was to evaluate the vibration level attenuation of a common wooden floor structure and to present the results together with the statistical precision of the evaluation. Linear regression was used to determine the attenuation rate in the two main directions of the floor...

  7. Vibrational anomalies and marginal stability of glasses

    KAUST Repository

    Marruzzo, Alessia


    The experimentally measured vibrational spectrum of glasses strongly deviates from that expected in Debye\\'s elasticity theory: The density of states deviates from Debye\\'s ω2 law ("boson peak"), the sound velocity shows a negative dispersion in the boson-peak frequency regime, and there is a strong increase in the sound attenuation near the boson-peak frequency. A generalized elasticity theory is presented, based on the model assumption that the shear modulus of the disordered medium fluctuates randomly in space. The fluctuations are assumed to be uncorrelated and have a certain distribution (Gaussian or otherwise). Using field-theoretical techniques one is able to derive mean-field theories for the vibrational spectrum of a disordered system. The theory based on a Gaussian distribution uses a self-consistent Born approximation (SCBA),while the theory for non-Gaussian distributions is based on a coherent-potential approximation (CPA). Both approximate theories appear to be saddle-point approximations of effective replica field theories. The theory gives a satisfactory explanation of the vibrational anomalies in glasses. Excellent agreement of the SCBA theory with simulation data on a soft-sphere glass is reached. Since the SCBA is based on a Gaussian distribution of local shear moduli, including negative values, this theory describes a shear instability as a function of the variance of shear fluctuations. In the vicinity of this instability, a fractal frequency dependence of the density of states and the sound attenuation ∝ ω1+a is predicted with a ≲ 1/2. Such a frequency dependence is indeed observed both in simulations and in experimental data. We argue that the observed frequency dependence stems from marginally stable regions in a glass and discuss these findings in terms of rigidity percolation. © 2013 EDP Sciences and Springer.

  8. Transverse vibration of nematic elastomer Timoshenko beams. (United States)

    Zhao, Dong; Liu, Ying; Liu, Chuang


    Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.

  9. Sensor fusion for active vibration isolation in precision equipment

    NARCIS (Netherlands)

    Tjepkema, D.; van Dijk, Johannes; Soemers, Herman


    Sensor fusion is a promising control strategy to improve the performance of active vibration isolation systems that are used in precision equipment. Normally, those vibration isolation systems are only capable of realizing a low transmissibility. Additional objectives are to increase the damping

  10. Active hard mount vibration isolation for precision equipment

    NARCIS (Netherlands)

    Tjepkema, D.


    Floor vibrations and acoustic excitation may limit the performance of precision equipment, that is used for example to produce computer chips or to make images of very tiny structures. Therefore, it is common to mount a vibration isolator in the suspension of such equipment to isolate it from these

  11. 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 ...

  12. A hybrid nonlinear vibration energy harvester (United States)

    Yang, Wei; Towfighian, Shahrzad


    Vibration energy harvesting converts mechanical energy from ambient sources to electricity to power remote sensors. Compared to linear resonators that have poor performance away from their natural frequency, nonlinear vibration energy harvesters perform better because they use vibration energy over a broader spectrum. We present a hybrid nonlinear energy harvester that combines bi-stability with internal resonance to increase the frequency bandwidth. A two-fold increase in the frequency bandwidth can be obtained compared to a bi-stable system with fixed magnets. The harvester consists of a piezoelectric cantilever beam carrying a movable magnet facing a fixed magnet. A spring allows the magnet to move along the beam and it provides an extra stored energy to further increase the amplitude of vibration acting as a mechanical amplifier. An electromechanically coupled mathematical model of the system is presented to obtain the dynamic response of the cantilever beam, the movable magnet and the output voltage. The perturbation method of multiple scales is applied to solve these equations and obtain approximate analytical solutions. The effects of various system parameters on the frequency responses are investigated. The numerical approaches of the long time integration (Runge-Kutta method) and the shooting technique are used to verify the analytical results. The results of this study can be used to improve efficiency in converting wasted mechanical vibration to useful electrical energy by broadening the frequency bandwidth.

  13. Vibrational spectroscopy and DFT calculations of flavonoid derriobtusone A (United States)

    Marques, A. N. L.; Mendes Filho, J.; Freire, P. T. C.; Santos, H. S.; Albuquerque, M. R. J. R.; Bandeira, P. N.; Leite, R. V.; Braz-Filho, R.; Gusmão, G. O. M.; Nogueira, C. E. S.; Teixeira, A. M. R.


    Flavonoids are secondary metabolites of plants which perform various functions. One subclass of flavonoid is auronol that can present immunostimulating activity. In this work Fourier-Transform Infrared with Attenuated Total Reflectance (FTIR-ATR) and Fourier-Transform Raman (FT-Raman) spectra of an auronol, derriobtusone A (C18H12O4), were obtained at room temperature. Theoretical calculations using Density Functional Theory (DFT) were performed in order to assign the normal modes and to interpret the spectra of the derriobtusone A molecule. The FTIR-ATR and FT-Raman spectra of the crystal, were recorded at room temperature in the regions 600 cm-1 to 4000 cm-1 and 40 cm-1 to 4000 cm-1, respectively. The normal modes of vibrations were obtained using Density Functional Theory with B3LYP functional and 6-31G+ (d,p) basis set. The calculated frequencies are in good agreement with those obtained experimentally. Detailed assignments of the normal modes present in both the Fourier-Transform infrared and the Fourier-Transform Raman spectra of the crystal are given.

  14. Landing gear noise attenuation (United States)

    Moe, Jeffrey W. (Inventor); Whitmire, Julia (Inventor); Kwan, Hwa-Wan (Inventor); Abeysinghe, Amal (Inventor)


    A landing gear noise attenuator mitigates noise generated by airframe deployable landing gear. The noise attenuator can have a first position when the landing gear is in its deployed or down position, and a second position when the landing gear is in its up or stowed position. The noise attenuator may be an inflatable fairing that does not compromise limited space constraints associated with landing gear retraction and stowage. A truck fairing mounted under a truck beam can have a compliant edge to allow for non-destructive impingement of a deflected fire during certain conditions.

  15. Analyzing the Effect of Capillary Force on Vibrational Performance of the Cantilever of an Atomic Force Microscope in Tapping Mode with Double Piezoelectric Layers in an Air Environment. (United States)

    Nahavandi, Amir; Korayem, Moharam Habibnejad


    The aim of this paper is to determine the effects of forces exerted on the cantilever probe tip of an atomic force microscope (AFM). These forces vary according to the separation distance between the probe tip and the surface of the sample being examined. Hence, at a distance away from the surface (farther than d(on)), these forces have an attractive nature and are of Van der Waals type, and when the probe tip is situated in the range of a₀≤ d(ts) ≤ d(on), the capillary force is added to the Van der Waals force. At a distance of d(ts) ≤ a₀, the Van der Waals and capillary forces remain constant at intermolecular distances, and the contact repulsive force repels the probe tip from the surface of sample. The capillary force emerges due to the contact of thin water films with a thickness of h(c) which have accumulated on the sample and probe. Under environmental conditions a layer of water or hydrocarbon often forms between the probe tip and sample. The capillary meniscus can grow until the rate of evaporation equals the rate of condensation. For each of the above forces, different models are presented. The smoothness or roughness of the surfaces and the geometry of the cantilever tip have a significant effect on the modeling of forces applied on the probe tip. Van der Waals and the repulsive forces are considered to be the same in all the simulations, and only the capillary force is altered in order to evaluate the role of this force in the AFM-based modeling. Therefore, in view of the remarkable advantages of the piezoelectric microcantilever and also the extensive applications of the tapping mode, we investigate vibrational motion of the piezoelectric microcantilever in the tapping mode. The cantilever mentioned is entirely covered by two piezoelectric layers that carry out both the actuation of the probe tip and the measuringof its position.

  16. Design of a nonlinear torsional vibration absorber (United States)

    Tahir, Ammaar Bin

    Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is usually tuned for a specific resonant frequency or an operating frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies, or for a system with varying excitation frequency. Vibration dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system. In this study, an experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber with geometrically induced cubic stiffness nonlinearity. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, the design optimization of the nonlinear torsional vibration absorber was carried out using an equivalent 2-DOF modal model. The optimality criterion was chosen to be maximization of energy dissipation in the nonlinear absorber attached to the equivalent 2-DOF system. The optimized design parameters of the nonlinear absorber were tested on the original 5-DOF system numerically. A comparison was made between the performance of linear and nonlinear absorbers using the numerical models. The comparison showed the superiority of the nonlinear absorber over its linear counterpart for the given set of primary system parameters as the vibration energy dissipation in the former is

  17. Anti-vibration method for wind-induced vibration in cable arrays of cable-stayed bridges. Part 2. Experimental study on the efficiency of spacers as vibration dampers; Shachokyo heiretsu cable no taifu seishin taisaku. 2. Shushu no jokenka ni okeru masatsugata gensui kinotsuki spacer no yukosei

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, T.; Fujiwara, A.; Ito, M. [Obayashi Corp., Tokyo (Japan)


    The present study has performed a two-dimensional sprint supporting experiment on effects imposed on vibration damping efficiency of spacers by variation in cable interval, vibration frequency, weight and diameter of parallel cables used in cable-stayed bridges. The experiment indicated phenomena varying in such a way that a characteristic having an unstable limit cycle is shown at cable intervals smaller than SH = 3.05 D, while a soft type characteristic is shown at cable intervals greater than 4.0 D. The onset velocity for wake galloping (WG) to appear increases in proportion to mass and attenuation parameters. Its increasing rate agrees nearly well with the manual type gradient. The appearance of WG can be suppressed easily when the cable intervals are greater than 4 D. The lower the cable vibration frequency, the higher the damping capability can be raised by using friction force. Because the damping performance of spacers decreases relatively when cable weight increases, the suppression effect decreases contrarily to a case of using no spacers. The wind velocity for the WG to appear when spacers are used can be evaluated by using the damping gradient. 5 refs., 20 figs., 1 tab.

  18. Vibration Properties of a Steel-PMMA Composite Beam

    Directory of Open Access Journals (Sweden)

    Yuyang He


    Full Text Available A steel-polymethyl methacrylate (steel-PMMA beam was fabricated to investigate the vibration properties of a one-dimensional phononic crystal structure. The experimental system included an excitation system, a signal acquisition system, and a data analysis and processing system. When an excitation signal was exerted on one end of the beam, the signals of six response points were collected with acceleration sensors. Subsequent signal analysis showed that the beam was attenuated in certain frequency ranges. The lumped mass method was then used to calculate the bandgap of the phononic crystal beam to analyze the vibration properties of a beam made of two different materials. The finite element method was also employed to simulate the vibration of the phononic crystal beam, and the simulation results were consistent with theoretical calculations. The existence of the bandgap was confirmed experimentally and theoretically, which allows for the potential applications of phononic crystals, including wave guiding and filtering, in integrated structures.

  19. Vibrational spectroscopy of resveratrol (United States)

    Billes, Ferenc; Mohammed-Ziegler, Ildikó; Mikosch, Hans; Tyihák, Ernő


    In this article the authors deal with the experimental and theoretical interpretation of the vibrational spectra of trans-resveratrol (3,5,4'-trihydroxy- trans-stilbene) of diverse beneficial biological activity. Infrared and Raman spectra of the compound were recorded; density functional calculations were carried out resulting in the optimized geometry and several properties of the molecule. Based on the calculated force constants, a normal coordinate analysis yielded the character of the vibrational modes and the assignment of the measured spectral bands.

  20. Bumblebee vibration activated foraging


    Su, Dan Kuan-Nien


    The ability use vibrational signals to activate nestmate foraging is found in the highly social bees, stingless bees and honey bees, and has been hypothesized to exist in the closely related, primitively eusocial bumble bees. We provide the first strong and direct evidence that this is correct. Inside the nest, bumble bee foragers produce brief bursts of vibration (foraging activation pulses) at 594.5 Hz for 63±26 ms (velocityRMS=0.46±0.02mm/s, forceRMS=0.8±0.2 mN. Production of these vibrati...

  1. Vibrations and waves

    CERN Document Server

    Kaliski, S


    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

  2. Tactile stimulation with kinesiology tape alleviates muscle weakness attributable to attenuation of Ia afferents. (United States)

    Konishi, Yu


    Prolonged vibration stimulation to normal individuals could lead to muscle weakness attributable to attenuation of afferent feedback. This weakness is neurophysiologically similar to that seen in patients with knee injury. Theoretically, increasing input to gamma motor neurons could reverse this weakness. Sensory input to these neurons from skin could indirectly increase Ia afferent feedback. The present study examined the effect of this tactile stimulation in the form of Kinesiology tape on muscle weakness attributable to attenuation of afferent feedback. Randomized, crossover design. All participants were measured their eccentric maximal voluntary contractions under the 2 conditions (taping and non-taping). First, maximal voluntary contraction during eccentric contraction was measured as baseline. For the taping condition, Kinesiology tape was applied around each subject's knee joint during maximal voluntary contraction measurement after vibration. For the non-taping condition, tape was not applied during maximal voluntary contraction measurement after vibration. Mean percentage changes between pre- and post-vibration stimulation were compared between two conditions. Maximal voluntary contraction and average electromyography of taping condition was significantly larger than that of non-taping condition. Our results suggest that tactile stimulation in the form of Kinesiology tape inhibits the decline of both strength and electromyography. Alpha motor neuron activity attenuated by prolonged vibration would thus be partially rescued by tactile stimulation. These results indirectly suggest that stimulation of skin around the knee could counter quadriceps femoris weakness due to attenuated Ia afferent activity. Copyright © 2012 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  3. 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


    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.

  4. Correction of vibration for classical free-fall gravimeters with correlation-analysis (United States)

    Wang, G.; Hu, H.; Wu, K.; Wang, L. J.


    In a free-fall absolute gravimeter, a laser interferometer is used to track the falling retro-reflector. To buffer the reference retro-reflector from seismic noise, a low-frequency vertical vibration isolator is traditionally used. However, an isolation device is usually complicated and expensive. A strap-down system using a seismometer to record the vibration and correct the measurement resolves the issue, but the actual recorded vibration cannot be directly used because of signal transfer delay and amplitude attenuation. Nevertheless, by quadratically fitting the trajectory of the falling retro-reflector and the motion of the reference retro-reflector, we find that their residuals are significantly correlated. Moreover, the transfer delay and the amplitude attenuation can be calculated using correlation analysis. With this capability, a vibration correction method for absolute gravimeters is proposed and demonstrated. The transfer delay and the gain attenuation are determined from data of only 25 drops, and can be used to correct subsequent measurements. The method is also applied in the T-1 absolute gravimeter. The standard deviation of the measurement results is improved by a factor of 20 after correction in a noisy environment, and improved by a factor of 5 in a quiet environment. Compared with vibration isolators, the strap-down system using this correction method is much more compact, enabling its use in field conditions or even dynamic environments not suitable for vibration isolators.

  5. Whole body vibration in sport: a critical review. (United States)

    Costantino, C; Gimigliano, R; Olvirri, S; Gimigliano, F


    Whole body vibration training is a recent area of study in athletic conditioning, health and rehabilitation. This paper provides a review of the effectiveness of this type of training in sport. A search was conducted across several electronic databases and studies on effects of whole body vibration training on sport performance were reviewed. Thirteen articles were included in the final analysis. The following variables were considered: participants investigated (sex and age), characteristics of the vibration (frequency and amplitude), training (type of sport, exposure time and intensity, tests used, type of study, effects examined and results obtained). This review considers proposed neural mechanisms and identifies studies that have demonstrated the effectiveness of WBV in sports. It considers where WBV might act and suggests that vibration can be an effective training stimulus. Future studies should focus on evaluating the long-term effects of vibration training and identify optimum frequency and amplitude, improve strength and muscular performance.

  6. Design and experiments of an active isolator for satellite micro-vibration

    Directory of Open Access Journals (Sweden)

    Li Weipeng


    Full Text Available In this paper, a soft active isolator (SAI derived from a voice coil motor is studied to determine its abilities as a micro-vibration isolation device for sensitive satellite payloads. Firstly, the two most important parts of the SAI, the mechanical unit and the low-noise driver, are designed and manufactured. Then, a rigid-flexible coupling dynamic model of the SAI is built, and a dynamic analysis is conducted. Furthermore, a controller with a sky-hook damper is designed. Finally, results from the performance tests of the mechanical/electronic parts and the isolation experiments are presented. The SAI attenuations are found to be more than −20 dB above 5 Hz, and the control effect is stable.

  7. Measurement of Dynamic Viscoelasticity of Full-Size Wood Composite Panels Using a Vibration Testing Method (United States)

    Cheng Guan; Houjiang Zhang; John F. Hunt; Lujing Zhou; Dan Feng


    The dynamic viscoelasticity of full-size wood composite panels (WCPs) under the free-free vibrational state were determined by a vibration testing method. Vibration detection tests were performed on 194 pieces of three types of full-size WCPs (particleboard, medium density fiberboard, and plywood (PW)). The dynamic viscoelasticity from smaller specimens cut from the...

  8. Optical Measurement of Cable and String Vibration

    Directory of Open Access Journals (Sweden)

    Y. Achkire


    Full Text Available This paper describes a non contacting measurement technique for the transverse vibration of small cables and strings using an analog position sensing detector. On the one hand, the sensor is used to monitor the cable vibrations of a small scale mock-up of a cable structure in order to validate the nonlinear cable dynamics model. On the other hand, the optical sensor is used to evaluate the performance of an active tendon control algorithm with guaranteed stability properties. It is demonstrated experimentally, that a force feedback control law based on a collocated force sensor measuring the tension in the cable is feasible and provides active damping in the cable.

  9. Vibration control of a cylindrical shell with concurrent active piezoelectric patches and passive cardboard liner (United States)

    Plattenburg, Joseph; Dreyer, Jason T.; Singh, Rajendra


    This article extends a recent publication [MSSP (2016), 176-196] by developing a Rayleigh-Ritz model of a thin cylindrical shell to predict its response subject to concurrent active and passive damping treatments. These take the form of piezoelectric patches and a distributed cardboard liner, since the effects of such combined treatments are yet to be investigated. Furthermore, prior literature typically considers only the ;bimorph; active patch configuration (with patches on the inner and outer shell surfaces), which is not feasible with an interior passive liner treatment. Therefore, a novel configuration-termed as ;unimorph;-is proposed and included in the model. Experiments are performed on a shell with active patches (under harmonic excitation from 200 to 2000 Hz) in both the bimorph and unimorph configurations to provide evidence for the analytical model predictions. The proposed model is then employed to assess competing control system designs by examining local vs. global control schemes as well as considering several alternate active patch locations, both with and without the passive damping. Non-dimensional performance metrics are devised to facilitate comparisons of vibration attenuation among different designs. Finally, insertion loss values are measured under single-frequency excitation to evaluate several vibration control designs, and to compare the effects of alternate damping treatments.

  10. Composite Struts Would Damp Vibrations (United States)

    Dolgin, Benjamin P.


    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.

  11. Ship Vibration Design Guide (United States)


    Frachtschiffen," Werft Reederie Hafen, 1925. 4-21 Noonan, E. F. "Vibration Considerations for 120,000 CM LNG Ships," NKF: Preliminary Report No. 7107, 25...Ship Response to Ice - A Second Season by C. Daley, J. W. St. John, R. Brown, J. Meyer , and I. Glen 1990 SSC-340 Ice Forces and Ship Response to Ice

  12. Compact Vibration Damper (United States)

    Ivanco, Thomas G. (Inventor)


    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.

  13. Vibrations and Eigenvalues

    Indian Academy of Sciences (India)

    The vibrating string problem is the source of much mathematicsand physics. This article describes Lagrange's formulationof a discretised version of the problem and its solution.This is also the first instance of an eigenvalue problem. Author Affiliations. Rajendra Bhatia1. Ashoka University, Rai, Haryana 131 029, India.

  14. Blade Vibration Measurement System (United States)

    Platt, Michael J.


    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.

  15. Systematically Controlling for the Influence of Age, Sex, Hertz and Time Post-Whole-Body Vibration Exposure on Four Measures of Physical Performance in Community-Dwelling Older Adults: A Randomized Cross-Over Study

    Directory of Open Access Journals (Sweden)

    Harold L. Merriman


    Full Text Available Though popular, there is little agreement on what whole-body vibration (WBV parameters will optimize performance. This study aimed to clarify the effects of age, sex, hertz and time on four physical function indicators in community-dwelling older adults (=32. Participants were exposed to 2 min WBV per session at either 2 Hz or 26 Hz and outcome measures were recorded at 2, 20 and 40 min post-WBV. Timed get up-and-go and chair sit-and-reach performances improved post-WBV for both sexes, were significantly different between 2 Hz and 26 Hz treatments (≤0.05 and showed statistically significant interactions between age and gender (≤0.01. Counter movement jump and timed one-legged stance performances showed a similar but non-significant response to 2 Hz and 26 Hz treatments, though male subjects showed a distinct trended response. Age and gender should be statistically controlled and both 2 Hz and 26 Hz exert a treatment effect.

  16. Vibration fatigue using modal decomposition (United States)

    Mršnik, Matjaž; Slavič, Janko; Boltežar, Miha


    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.

  17. Possible Mechanisms of Low Back Pain due to Whole-Body Vibration (United States)

    Pope, M. H.; Wilder, D. G.; Magnusson, M.


    The investigators describe their multifaceted approach to the study of the relationship between whole-body vibration and low back pain.In vitroexperiments, using percutaneous pin-mounted accelerometers have shown that the natural frequency is at 4·5 Hz. The frequency response was affected by posture, seating, and seat-back inclination. The response appears to be largely determined by the rocking of the pelvis. Electromyographic studies have shown that muscle fatigue occurs under whole body vibration. After whole body vibration exposure the muscle response to a sudden load has greater latency. Vehicle driving may be a reason for low back pain or herniated nucleus pulposus. Prolonged seating exposure, coupled with the whole body vibration should be reduced for those recovering from these problems. Vibration attenuating seats, and correct ergonomic layout of the cabs may reduce the risks of recurrence.

  18. The influence of vibrational state-resolved transport coefficients on the wave propagation in diatomic gases (United States)

    Kremer, Gilberto M.; Kunova, Olga V.; Kustova, Elena V.; Oblapenko, George P.


    A detailed kinetic-theory model for the vibrationally state-resolved transport coefficients is developed taking into account the dependence of the collision cross section on the size of vibrationally excited molecule. Algorithms for the calculation of shear and bulk viscosity, thermal conductivity, thermal diffusion and diffusion coefficients for vibrational states are proposed. The transport coefficients are evaluated for single-component diatomic gases N2, O2, NO, H2, Cl2 in the wide range of temperature, and the effects of molecular diameters and the number of accounted states are discussed. The developed model is applied to study wave propagation in diatomic gases. For the case of initial Boltzmann distribution, the influence of vibrational excitation on the phase velocity and attenuation coefficient is found to be weak. We expect more significant effect in the case of initial thermal non-equilibrium, for instance in gases with optically pumped selected vibrational states.

  19. Active Vibration Control of a Railway Vehicle Carbody Using Piezoelectric Elements (United States)

    Molatefi, Habibollah; Ayoubi, Pejman; Mozafari, Hozhabr


    In recent years and according to modern transportation development, rail vehicles are manufactured lighter to achieve higher speed and lower transportation costs. On the other hand, weight reduction of rail vehicles leads to increase the structural vibration. In this study, Active Vibration Control of a rail vehicle using piezoelectric elements is investigated. The optimal control employed as the control approach regard to the first two modes of vibration. A simplified Car body structure is modeled in Matlab using the finite element theory by considering six DOF beam element and then the Eigen functions and mode shapes are derived. The surface roughness of different classes of rail tracks have been obtained using random vibration theory and applied to the secondary suspension as the excitation of the structure; Then piezoelectric mounted where the greatest moments were captured. The effectiveness of Piezoelectric in structural vibrations attenuation of car body is demonstrated through the state space equations and its effect on modal coefficient.

  20. Determination of the attenuation map in emission tomography

    CERN Document Server

    Zaidi, H


    Reliable attenuation correction methods for quantitative emission computed tomography (ECT) require accurate delineation of the body contour and often necessitate knowledge of internal anatomical structure. Two broad classes of methods have been used to calculate the attenuation map referred to as "transmissionless" and transmission-based attenuation correction techniques. While calculated attenuation correction belonging to the first class of methods is appropriate for brain studies, more adequate methods must be performed in clinical applications where the attenuation coefficient distribution is not known a priori, and for areas of inhomogeneous attenuation such as the chest. Measured attenuation correction overcomes this problem and utilizes different approaches to determine this map including transmission scanning, segmented magnetic resonance images or appropriately scaled X-ray CT scans acquired either independently on separate or simultaneously on multimodality imaging systems. Combination of data acqu...

  1. Smart paint sensor for monitoring structural vibrations (United States)

    Al-Saffar, Y.; Aldraihem, O.; Baz, A.


    A class of smart paint sensors is proposed for monitoring the structural vibration of beams. The sensor is manufactured from an epoxy resin which is mixed with carbon black nano-particles to make it electrically conducting and sensitive to mechanical vibrations. A comprehensive theoretical and experimental investigation is presented to understand the underlying phenomena governing the operation of this class of paint sensors and evaluate its performance characteristics. A theoretical model is presented to model the electromechanical behavior of the sensor system using molecular theory. The model is integrated with an amplifier circuit in order to predict the current and voltage developed by the paint sensor when subjected to loading. Furthermore, the sensor/amplifier circuit models are coupled with a finite element model of a base beam to which the sensor is bonded. The resulting multi-field model is utilized to predict the behavior of both the sensor and the beam when subjected to a wide variety of vibration excitations. The predictions of the multi-field finite element model are validated experimentally and the behavior of the sensor is evaluated both in the time and the frequency domains. The performance of the sensor is compared with the performance of conventional strain gages to emphasize its potential and merits. The presented techniques are currently being extended to sensors that can monitor the vibration and structural power flow of two-dimensional structures.

  2. Vibration-free stirling cryocooler for high definition microscopy (United States)

    Riabzev, S. V.; Veprik, A. M.; Vilenchik, H. S.; Pundak, N.; Castiel, E.


    The normal operation of high definition Scanning Electronic and Helium Ion microscope tools often relies on maintaining particular components at cryogenic temperatures. This has traditionally been accomplished by using liquid coolants such as liquid Nitrogen. This inherently limits the useful temperature range to above 77 K, produces various operational hazards and typically involves elevated ownership costs, inconvenient logistics and maintenance. Mechanical coolers, over-performing the above traditional method and capable of delivering required (even below 77 K) cooling to the above cooled components, have been well-known elsewhere for many years, but their typical drawbacks, such as high purchasing cost, cooler size, low reliability and high power consumption have so far prevented their wide-spreading. Additional critical drawback is inevitable degradation of imagery performance originated from the wideband vibration export as typical for the operation of the mechanical cooler incorporating numerous movable components. Recent advances in the development of reliable, compact, reasonably priced and dynamically quiet linear cryogenic coolers gave rise to so-called "dry cooling" technologies aimed at eventually replacing the traditional use of outdated liquid Nitrogen cooling facilities. Although much improved these newer cryogenic coolers still produce relatively high vibration export which makes them incompatible with modern high definition microscopy tools. This has motivated further research activity towards developing a vibration free closed-cycle mechanical cryocooler. The authors have successfully adapted the standard low vibration Stirling cryogenic refrigerator (Ricor model K535-LV) delivering 5 W@40 K heat lift for use in vibration-sensitive high definition microscopy. This has been achieved by using passive mechanical counterbalancing of the main portion of the low frequency vibration export in combination with an active feed-forward multi

  3. The Use of Body Worn Sensors for Detecting the Vibrations Acting on the Lower Back in Alpine Ski Racing (United States)

    Spörri, Jörg; Kröll, Josef; Fasel, Benedikt; Aminian, Kamiar; Müller, Erich


    This study explored the use of body worn sensors to evaluate the vibrations that act on the human body in alpine ski racing from a general and a back overuse injury prevention perspective. In the course of a biomechanical field experiment, six male European Cup-level athletes each performed two runs on a typical giant slalom (GS) and slalom (SL) course, resulting in a total of 192 analyzed turns. Three-dimensional accelerations were measured by six inertial measurement units placed on the right and left shanks, right and left thighs, sacrum, and sternum. Based on these data, power spectral density (PSD; i.e., the signal's power distribution over frequency) was determined for all segments analyzed. Additionally, as a measure expressing the severity of vibration exposure, root-mean-square (RMS) acceleration acting on the lower back was calculated based on the inertial acceleration along the sacrum's longitudinal axis. In both GS and SL skiing, the PSD values of the vibrations acting at the shank were found to be largest for frequencies below 30 Hz. While being transmitted through the body, these vibrations were successively attenuated by the knee and hip joint. At the lower back (i.e., sacrum sensor), PSD values were especially pronounced for frequencies between 4 and 10 Hz, whereas a corresponding comparison between GS and SL revealed higher PSD values and larger RMS values for GS. Because vibrations in this particular range (i.e., 4 to 10 Hz) include the spine's resonant frequency and are known to increase the risk of structural deteriorations/abnormalities of the spine, they may be considered potential components of mechanisms leading to overuse injuries of the back in alpine ski racing. Accordingly, any measure to control and/or reduce such skiing-related vibrations to a minimum should be recognized and applied. In this connection, wearable sensor technologies might help to better monitor and manage the overall back overuse-relevant vibration exposure of athletes

  4. The Use of Body Worn Sensors for Detecting the Vibrations Acting on the Lower Back in Alpine Ski Racing. (United States)

    Spörri, Jörg; Kröll, Josef; Fasel, Benedikt; Aminian, Kamiar; Müller, Erich


    This study explored the use of body worn sensors to evaluate the vibrations that act on the human body in alpine ski racing from a general and a back overuse injury prevention perspective. In the course of a biomechanical field experiment, six male European Cup-level athletes each performed two runs on a typical giant slalom (GS) and slalom (SL) course, resulting in a total of 192 analyzed turns. Three-dimensional accelerations were measured by six inertial measurement units placed on the right and left shanks, right and left thighs, sacrum, and sternum. Based on these data, power spectral density (PSD; i.e., the signal's power distribution over frequency) was determined for all segments analyzed. Additionally, as a measure expressing the severity of vibration exposure, root-mean-square (RMS) acceleration acting on the lower back was calculated based on the inertial acceleration along the sacrum's longitudinal axis. In both GS and SL skiing, the PSD values of the vibrations acting at the shank were found to be largest for frequencies below 30 Hz. While being transmitted through the body, these vibrations were successively attenuated by the knee and hip joint. At the lower back (i.e., sacrum sensor), PSD values were especially pronounced for frequencies between 4 and 10 Hz, whereas a corresponding comparison between GS and SL revealed higher PSD values and larger RMS values for GS. Because vibrations in this particular range (i.e., 4 to 10 Hz) include the spine's resonant frequency and are known to increase the risk of structural deteriorations/abnormalities of the spine, they may be considered potential components of mechanisms leading to overuse injuries of the back in alpine ski racing. Accordingly, any measure to control and/or reduce such skiing-related vibrations to a minimum should be recognized and applied. In this connection, wearable sensor technologies might help to better monitor and manage the overall back overuse-relevant vibration exposure of athletes

  5. The Use of Body Worn Sensors for Detecting the Vibrations Acting on the Lower Back in Alpine Ski Racing

    Directory of Open Access Journals (Sweden)

    Jörg Spörri


    Full Text Available This study explored the use of body worn sensors to evaluate the vibrations that act on the human body in alpine ski racing from a general and a back overuse injury prevention perspective. In the course of a biomechanical field experiment, six male European Cup-level athletes each performed two runs on a typical giant slalom (GS and slalom (SL course, resulting in a total of 192 analyzed turns. Three-dimensional accelerations were measured by six inertial measurement units placed on the right and left shanks, right and left thighs, sacrum, and sternum. Based on these data, power spectral density (PSD; i.e., the signal's power distribution over frequency was determined for all segments analyzed. Additionally, as a measure expressing the severity of vibration exposure, root-mean-square (RMS acceleration acting on the lower back was calculated based on the inertial acceleration along the sacrum's longitudinal axis. In both GS and SL skiing, the PSD values of the vibrations acting at the shank were found to be largest for frequencies below 30 Hz. While being transmitted through the body, these vibrations were successively attenuated by the knee and hip joint. At the lower back (i.e., sacrum sensor, PSD values were especially pronounced for frequencies between 4 and 10 Hz, whereas a corresponding comparison between GS and SL revealed higher PSD values and larger RMS values for GS. Because vibrations in this particular range (i.e., 4 to 10 Hz include the spine's resonant frequency and are known to increase the risk of structural deteriorations/abnormalities of the spine, they may be considered potential components of mechanisms leading to overuse injuries of the back in alpine ski racing. Accordingly, any measure to control and/or reduce such skiing-related vibrations to a minimum should be recognized and applied. In this connection, wearable sensor technologies might help to better monitor and manage the overall back overuse-relevant vibration

  6. Radiofrequency attenuator and method (United States)

    Warner, Benjamin P [Los Alamos, NM; McCleskey, T Mark [Los Alamos, NM; Burrell, Anthony K [Los Alamos, NM; Agrawal, Anoop [Tucson, AZ; Hall, Simon B [Palmerston North, NZ


    Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

  7. Animal Communications Through Seismic Vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Peggy (University of Tulsa)


    Substrate vibration has been important to animals as a channel of communication for millions of years, but our literature on vibration in this context of biologically relevant information is only decades old. The jaw mechanism of the earliest land vertebrates allowed them to perceive substrate vibrations as their heads lay on the ground long before airborne sounds could be heard. Although the exact mechanism of vibration production and the precise nature of the wave produced are not always understood, recent development of affordable instrumentation to detect and measure vibrations has allowed researchers to answer increasingly sophisticated questions about how animals send and receive vibration signals. We now know that vibration provides information used in predator defense, prey detection, recruitment to food, mate choice, intrasexual competition, and maternal/brood social interactions in a variety of insect orders, spiders, crabs, scorpions, chameleons, frogs, golden moles, mole rats, kangaroos rats, wallabies, elephants and bison.

  8. Performance evaluation of full-scale tuned liquid dampers (TLDs) for vibration control of large wind turbines using real-time hybrid testing

    DEFF Research Database (Denmark)

    Zhang, Zili; Staino, Andrea; Basu, Biswajit


    Highlights •Performance evaluation of full-scale tuned liquid dampers carried out for wind turbines. •Coupled blade-tower model considered in the numerical sub-structure. •Stochastic turbulence due to rotationally sampled spectra considered. •Effect of damping screens experimentally investigated...

  9. Vision Influence on Whole-Body Human Vibration Comfort Levels

    Directory of Open Access Journals (Sweden)

    Maria Lúcia Machado Duarte


    Full Text Available The well being of people needs to be a priority in the modern world. In that respect, vibration cannot be one more cause of stress. Besides that, vibration comfort is very important, since high levels may cause health or even tasks' accomplishment problems. Several parameters may influence the levels of vibration a human being supports. Among them, one can mention the influence of gender, age, corporeal mass index (CMI, temperature, humor, anxiety, hearing, posture, vision, etc. The first three parameters mentioned were already investigated in previous studies undertaken by GRAVI (Group of Acoustics and Vibration researchers. In this paper, the influence of vision is evaluated. The main objective with this series of tests performed is to try to quantify in a future the influence of each parameter in a global vibration comfort level. Conclusions are presented for the parameter investigated.


    Energy Technology Data Exchange (ETDEWEB)

    Xu, Hanbing [University of Tennessee, Knoxville (UTK); Meek, Thomas T. [University of Tennessee, Knoxville (UTK); Han, Qingyou [ORNL


    In order to investigate the effects of ultrasonic vibration on degassing of aluminum alloys, three experimental systems have been designed and built: one for ultrasonic degassing in open air, one for ultrasonic degassing under reduced pressure, and one for ultrasonic degassing with a purging gas. Experiments were first carried out in air to test degassing using ultrasonic vibration alone. The limitations with ultrasonic degassing were outlined. Further experiments were then performed under reduced pressures and in combination with purging argon gas. Experimental results suggest that ultrasonic vibration alone is efficient for degassing a small volume of melt. Ultrasonic vibration can be used for assisting vacuum degassing, making vacuum degassing much faster than that without using ultrasonic vibration. Ultrasonically assisted argon degassing is the fastest method for degassing among the three methods tested in this research. More importantly, dross formation during ultrasonically assisted argon degassing is much less than that during argon degassing. The mechanisms of ultrasonic degassing are discussed.

  11. [Vibrational physical exercises as the rehabilitation in gerontology]. (United States)

    Piatin, V F; Shirolapov, I V; Nikitin, O L


    Vibration biomechanical stimulation as the physiological basis of vibration physical exercises (whole body vibration) causes reflecting muscle contractions like tonic vibration reflex. This type of intervention leads to high intensive stimulation of proprioceptors as called muscle spindles which result in alteration in parameters of activity and developments of human physiological functions. This type of training has broad positive influence on organism. Acceleration physical exercises improve muscle performance, flexibility, nervous function, significantly increase bone mineral density, physiological secretion of anabolic hormones, growth and anti-aging factors; normalize/decrease cortisol as anti-stress effect and are beneficial for balance and mobility as well. It is showed acceleration training caused by vibration stimulus is beneficial for people suffering from osteoporosis and obesity, for rehabilitation of nervous and motor function in patients with Parkinson's disease, multiple sclerosis and stroke.

  12. Tactile direction discrimination and vibration detection in diabetic neuropathy. (United States)

    Löken, Linda S; Lundblad, L C; Elam, M; Olausson, H W


    To evaluate the clinical usefulness of quantitative testing of tactile direction discrimination (TDD) in patients with diabetic neuropathy. TDD and vibration detection were examined on the dorsum of the feet in 43 patients with type 1 diabetes mellitus and clinical signs and symptoms indicating mild neuropathy, and abnormal results for neurography, temperature detection, or heart rate variability. Test-retest examination of TDD was performed in nine of the patients. Twenty-six of the patients had abnormal TDD (sensitivity 0.60) and 20 had abnormal vibration detection (sensitivity 0.46). Ten of the patients had abnormal TDD and normal vibration detection. Four of the patients had abnormal vibration detection and normal TDD. Test-retest examination of TDD showed a high degree of reproducibility (r = 0.87). TDD seems more useful than vibration detection in examination of diabetic neuropathy.

  13. Researches Concerning to Minimize Vibrations when Processing Normal Lathe

    Directory of Open Access Journals (Sweden)

    Lenuța Cîndea


    Full Text Available In the cutting process, vibration is inevitable appearance, and in situations where the amplitude exceeds the limits of precision dimensional and shape of the surfaces generated vibrator phenomenon is detrimental.Field vibration is an issue of increasingly developed, so the futures will a better understanding of them and their use even in other sectors.The paper developed experimental measurement of vibrations at the lathe machining normal. The scheme described kinematical machine tool, cutting tool, cutting conditions, presenting experimental facility for measuring vibration occurring at turning. Experimental results have followed measurement of amplitude, which occurs during interior turning the knife without silencer incorporated. The tests were performed continuously for different speed, feed and depth of cut.

  14. Attenuated gastric distress but no benefit to performance with adaptation to octanoate-rich esterified oils in well-trained male cyclists

    DEFF Research Database (Denmark)

    Thorburn, M.S.; Vistisen, Bodil; Thorp, R.M.


    We investigated the effects of modifying a normal dietary fatty acid composition and ingestion of high-fat exercise supplements on gastrointestinal distress, substrate oxidation. and endurance cycling performance. Nine well-trained male cyclists completed a randomized triple-crossover comprising...

  15. Good vibrations. [Hydraulic turbines

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, P.


    The latest developments in the Voith Turbine Control and Automation System (VTLS), which couples digital control technology to hydropower plant equipment, are described. Prominent among these is the vibration diagnostics module for hydraulic turbines. It provides machine-specific diagnostic logic for a vibration monitoring and analysis system. Of the two other VTLS modules described, the operation module optimizes the control of a power plant with three or more turbines by considering the individual properties of each in turn, recommending which should be run, and how, in order to partition the load for a required power output. The cavitation module is a diagnostic system which enables the limits of operation of the turbines to be extended to bands just outside those determined by cavitation calculations. (3 figures). (UK)

  16. Experimental study on titanium wire drawing with ultrasonic vibration. (United States)

    Liu, Shen; Shan, Xiaobiao; Guo, Kai; Yang, Yuancai; Xie, Tao


    Titanium and its alloys have been widely used in aerospace and biomedical industries, however, they are classified as difficult-to-machine materials. In this paper, ultrasonic vibration is imposed on the die to overcome the difficulties during conventional titanium wire drawing processes at the room temperature. Numerical simulations were performed to investigate the variation of axial stress within the contacting region and study the change of the drawing stress with several factors in terms of the longitudinal amplitude and frequency of the applied ultrasonic vibration, the diameter reduction ratio, and the drawing force. An experimental testing equipment was established to measure the drawing torque and rotational velocity of the coiler drum during the wire drawing process. The result indicates the drawing force increases with the growth of the drawing velocity and the reduction ratio, whether with or without vibrations. Application of either form of ultrasonic vibrations contributes to the further decrease of the drawing force, especially the longitudinal vibration with larger amplitude. SEM was employed to detect the surface morphology of the processed wires drawn under the three circumstances. The surface quality of the drawn wires with ultrasonic vibrations was apparently improved compared with those using conventional method. In addition, the longitudinal and torsional composite vibration was more effective for surface quality improvement than pure longitudinal vibration, however, at the cost of weakened drawing force reduction effect. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. The application of SEAT values for predicting how compliant seats with backrests influence vibration discomfort. (United States)

    Basri, Bazil; Griffin, Michael J


    The extent to which a seat can provide useful attenuation of vehicle vibration depends on three factors: the characteristics of the vehicle motion, the vibration transmissibility of the seat, and the sensitivity of the body to vibration. The 'seat effective amplitude transmissibility' (i.e., SEAT value) reflects how these three factors vary with the frequency and the direction of vibration so as to predict the vibration isolation efficiency of a seat. The SEAT value is mostly used to select seat cushions or seat suspensions based on the transmission of vertical vibration to the principal supporting surface of a seat. This study investigated the accuracy of SEAT values in predicting how seats with backrests influence the discomfort caused by multiple-input vibration. Twelve male subjects participated in a four-part experiment to determine equivalent comfort contours, the relative discomfort, the location of discomfort, and seat transmissibility with three foam seats and a rigid reference seat at 14 frequencies of vibration in the range 1-20 Hz at magnitudes of vibration from 0.2 to 1.6 ms(-2) r.m.s. The 'measured seat dynamic discomfort' (MSDD) was calculated for each foam seat from the ratio of the vibration acceleration required to cause similar discomfort with the foam seat and with the rigid reference seat. Using the frequency weightings in current standards, the SEAT values of each seat were calculated from the ratio of overall ride values with the foam seat to the overall ride values with the rigid reference seat, and compared to the corresponding MSDD at each frequency. The SEAT values provided good predictions of how the foam seats increased vibration discomfort at frequencies around the 4-Hz resonance but reduced vibration discomfort at frequencies greater than about 6.3 Hz, with discrepancies explained by a known limitation of the frequency weightings. Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  18. A multi-ingredient containing, proteins, carbohydrate and creatine does not attenuate humoral immune response or performance decrease compared to carbohydrate during resistance training


    Ashrafi, Nadia; Seijo, Marcos; Pullen, Frank; Birthe V. Nielsen; Smith, Joshua; Wilkinson, Christian; Fu, Yue; Miller, Jack; Larumbe-Zabala, Eneko; Naclerio, Fernando


    Background: Nowadays, only carbohydrate has shown to be an effective countermeasure to exercise-induced immune dysfunction while the effect of protein remains controversial. The purpose of this study was to investigate the acute effects of a commercially available multi-nutrient supplement on performance and salivary markers of humoral immunity, following a bout of circuit resistance training in young athletes.\\ud \\ud Methods: Twelve recreationally resistance-trained males (age: 22 ± 1.4 year...

  19. Pickin’ up good vibrations

    CERN Multimedia

    Katarina Anthony


    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...

  20. Vibrational stability of graphene

    Directory of Open Access Journals (Sweden)

    Yangfan Hu


    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.

  1. A smart dynamic vibration absorber for suppressing the vibration of a string supported by flexible beams (United States)

    Nambu, Yohsuke; Yamamoto, Shota; Chiba, Masakatsu


    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.

  2. [Measurement and analysis of hand-transmitted vibration of vibration tools in workplace for automobile casting and assembly]. (United States)

    Xie, X S; Qi, C; Du, X Y; Shi, W W; Zhang, M


    To investigate the features of hand-transmitted vibration of common vibration tools in the workplace for automobile casting and assembly. From September to October, 2014, measurement and spectral analysis were performed for 16 typical hand tools(including percussion drill, pneumatic wrench, grinding machine, internal grinder, and arc welding machine) in 6 workplaces for automobile casting and assembly according to ISO 5349-1-2001 Mechanical vibration-Measurement and evaluation of human exposure to hand-transmitted vibration-part 1: General requirements and ISO 5349-2-2001 Mechanical vibration-Measurement and evaluation of human exposure to hand-transmitted vibration-Part 2: Practical guidance for measurement in the workplace. The vibration acceleration waveforms of shearing machine, arc welding machine, and pneumatic wrench were mainly impact wave and random wave, while those of internal grinder, angle grinder, percussion drill, and grinding machine were mainly long-and short-period waves. The daily exposure duration to vibration of electric wrench, pneumatic wrench, shearing machine, percussion drill, and internal grinder was about 150 minutes, while that of plasma cutting machine, angle grinder, grinding machine, bench grinder, and arc welding machine was about 400 minutes. The range of vibration total value(ahv) was as follows: pneumatic wrench 0.30~11.04 m/s(2), grinding wheel 1.61~8.97 m/s(2), internal grinder 1.46~8.70 m/s(2), percussion drill 11.10~14.50 m/s(2), and arc welding machine 0.21~2.18 m/s(2). The workers engaged in cleaning had the longest daily exposure duration to vibration, and the effective value of 8-hour energy-equivalent frequency-weighted acceleration for them[A(8)] was 8.03 m/s(2), while this value for workers engaged in assembly was 4.78 m/s(2). The frequency spectrogram with an 1/3-time frequency interval showed that grinding machine, angle grinder, and percussion drill had a high vibration acceleration, and the vibration limit curve

  3. Adaptive vibration control using synchronous demodulation with machine tool controller motor commutation (United States)

    Hopkins, David James [Livermore, CA


    A control system and method for actively reducing vibration in a spindle housing caused by unbalance forces on a rotating spindle, by measuring the force-induced spindle-housing motion, determining control signals based on synchronous demodulation, and provide compensation for the measured displacement to cancel or otherwise reduce or attenuate the vibration. In particular, the synchronous demodulation technique is performed to recover a measured spindle housing displacement signal related only to the rotation of a machine tool spindle, and consequently rejects measured displacement not related to spindle motion or synchronous to a cycle of revolution. Furthermore, the controller actuates at least one voice-coil (VC) motor, to cancel the original force-induced motion, and adapts the magnitude of voice coil signal until this measured displacement signal is brought to a null. In order to adjust the signal to a null, it must have the correct phase relative to the spindle angle. The feedback phase signal is used to adjust a common (to both outputs) commutation offset register (offset relative to spindle encoder angle) to force the feedback phase signal output to a null. Once both of these feedback signals are null, the system is compensating properly for the spindle-induced motion.

  4. Natural attenuation of herbicides

    DEFF Research Database (Denmark)

    Tuxen, Nina; Højberg, Anker Lajer; Broholm, Mette Martina


    A field injection experiment in a sandy, aerobic aquifer showed that two phenoxy acids MCPP (mecoprop) and dichlorprop were degraded within I in downgradient of the injection wells after an apparent lag period. The plume development and microbial measurements indicated that microbial growth....... The observations may be important for application of natural attenuation as a remedy in field scale systems....

  5. High-Performance Reaction Wheel Optimization for Fine-Pointing Space Platforms: Minimizing Induced Vibration Effects on Jitter Performance plus Lessons Learned from Hubble Space Telescope for Current and Future Spacecraft Applications (United States)

    Hasha, Martin D.


    The Hubble Space Telescope (HST) applies large-diameter optics (2.5-m primary mirror) for diffraction-limited resolution spanning an extended wavelength range (approx. 100-2500 nm). Its Pointing Control System (PCS) Reaction Wheel Assemblies (RWAs), in the Support Systems Module (SSM), acquired an unprecedented set of high-sensitivity Induced Vibration (IV) data for 5 flight-certified RWAs: dwelling at set rotation rates. Focused on 4 key ratios, force and moment harmonic values (in 3 local principal directions) are extracted in the RWA operating range (0-3000 RPM). The IV test data, obtained under ambient lab conditions, are investigated in detail, evaluated, compiled, and curve-fitted; variational trends, core causes, and unforeseen anomalies are addressed. In aggregate, these values constitute a statistically-valid basis to quantify ground test-to-test variations and facilitate extrapolations to on-orbit conditions. Accumulated knowledge of bearing-rotor vibrational sources, corresponding harmonic contributions, and salient elements of IV key variability factors are discussed. An evolved methodology is presented for absolute assessments and relative comparisons of macro-level IV signal magnitude due to micro-level construction-assembly geometric details/imperfections stemming from both electrical drive and primary bearing design parameters. Based upon studies of same-size/similar-design momentum wheels' IV changes, upper estimates due to transitions from ground tests to orbital conditions are derived. Recommended HST RWA choices are discussed relative to system optimization/tradeoffs of Line-Of-Sight (LOS) vector-pointing focal-plane error driven by higher IV transmissibilities through low-damped structural dynamics that stimulate optical elements. Unique analytical disturbance results for orbital HST accelerations are described applicable to microgravity efforts. Conclusions, lessons learned, historical context/insights, and perspectives on future applications

  6. Measurements of attenuation coefficient for evaluating the hardness of a cataract lens by a high-frequency ultrasonic needle transducer (United States)

    Chen, Ruimin; Tsui, Po-Hsiang; Zhou, Qifa; Humayun, Mark S; Shung, K Kirk


    A cataract is a clouding of the lens in the eye that affects vision. Phacoemulsification is the mostly common surgical method for treating cataracts, and determining that the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the use of an ultrasound needle transducer for invasive measurements of ultrasound attenuation coefficient to evaluate the hardness of the cataract lens. A 47 MHz high-frequency needle transducer with a diameter of 0.9 mm was fabricated by a polarized PMN-33%PT single crystal in the present study. The attenuation coefficients at different stages of an artificial porcine cataract lens were measured using the spectral shift approach. The hardness of the cataract lens was also evaluated by mechanical measurement of its elastic properties. The results demonstrated that the ultrasonic attenuation coefficient was increased from 0.048 ± 0.02 to 0.520 ± 0.06 dB mm−1 MHz−1 corresponding to an increase in Young’s modulus from 6 ± 0.4 to 96 ± 6.2 kPa as the cataract further developed. In order to evaluate the feasibility of combining needle transducer and phacoemulsification probe for real-time measurement during cataract surgery, the needle transducer was mounted on the phacoemulsification probe for a vibration test. The results indicated that there was no apparent damage to the tip of the needle transducer and the pulse–echo test showed that a good performance in sensitivity was maintained after the vibration test. PMID:19759408

  7. Measurements of attenuation coefficient for evaluating the hardness of a cataract lens by a high-frequency ultrasonic needle transducer

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.-C. [Department of Electronic Engineering, Fu Jen Catholic University, Taipei 24205, Taiwan (China); Chen Ruimin; Zhou Qifa; Shung, K Kirk [NIH Resource on Medical Ultrasonic Transducer Technology, Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089 (United States); Tsui, P.-H. [Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan (China); Humayun, Mark S [Doheny Retina Institute, Doheny Eye Institute, Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033 (United States)], E-mail:


    A cataract is a clouding of the lens in the eye that affects vision. Phacoemulsification is the mostly common surgical method for treating cataracts, and determining that the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the use of an ultrasound needle transducer for invasive measurements of ultrasound attenuation coefficient to evaluate the hardness of the cataract lens. A 47 MHz high-frequency needle transducer with a diameter of 0.9 mm was fabricated by a polarized PMN-33%PT single crystal in the present study. The attenuation coefficients at different stages of an artificial porcine cataract lens were measured using the spectral shift approach. The hardness of the cataract lens was also evaluated by mechanical measurement of its elastic properties. The results demonstrated that the ultrasonic attenuation coefficient was increased from 0.048 {+-} 0.02 to 0.520 {+-} 0.06 dB mm{sup -1} MHz{sup -1} corresponding to an increase in Young's modulus from 6 {+-} 0.4 to 96 {+-} 6.2 kPa as the cataract further developed. In order to evaluate the feasibility of combining needle transducer and phacoemulsification probe for real-time measurement during cataract surgery, the needle transducer was mounted on the phacoemulsification probe for a vibration test. The results indicated that there was no apparent damage to the tip of the needle transducer and the pulse-echo test showed that a good performance in sensitivity was maintained after the vibration test.

  8. Performance analysis of proportional-integral feedback control for the reduction of stick-slip-induced torsional vibrations in oil well drillstrings (United States)

    Monteiro, Hugo L. S.; Trindade, Marcelo A.


    The stick-slip phenomenon, in the process of drilling oil wells, can lead to large fluctuations in drill-bit angular velocity, due to the interaction between drill-bit and rock formation, and, thus, cause irreparable damage to the process. In this work, the performance of control laws applied to the rotary table (responsible for moving the drillstring) is analyzed, in order to reduce stick-slip and drill-bit angular velocity oscillations. The control laws implemented are based on a PI (Proportional-Integral) controller, for which the torque applied to the rotating table has components proportional and integral to the table angular velocity with constant or variable WOB (Weight-On-Bit). For the drillstring, a finite element model with a linear interpolation for the torsional motion was proposed. The torque at drill-bit was modeled considering a non-regularized dry friction model, with parameters that were adjusted using empirical data proposed in literature. Several performance criteria were analyzed and it was observed that a minimization of the mean deviation of the drill-bit angular velocity relative to the target one would provide the best operating condition. Parametric analyses of proportional and integral control gains were performed, yielding level curves for the mean deviation of drill-bit angular velocity. From these curves, stability regions were defined in which the deviation is acceptable. These regions were observed to be wider for smaller values of WOB and higher values of target angular velocity and vice-versa. In addition, the inclusion of a controlled dynamic WOB was proposed leading to reduced levels of mean deviation of angular velocity and, thus, improving stability regions for the drilling process.

  9. Scalable high-performance algorithm for the simulation of exciton-dynamics. Application to the light harvesting complex II in the presence of resonant vibrational modes

    DEFF Research Database (Denmark)

    Kreisbeck, Christoph; Kramer, Tobias; Aspuru-Guzik, Alán


    the exciton dynamics within a density-matrix formalism are known, but are restricted to small systems with less than ten sites due to their computational complexity. To study the excitonic energy transfer in larger systems, we adapt and extend the exact hierarchical equation of motion (HEOM) method to various...... high-performance many-core platforms using the Open Compute Language (OpenCL). For the light-harvesting complex II (LHC II) found in spinach, the HEOM results deviate from predictions of approximate theories and clarify the time-scale of the transfer-process. We investigate the impact of resonantly...

  10. A low-dose, 6-week bovine colostrum supplementation maintains performance and attenuates inflammatory indices following a Loughborough Intermittent Shuttle Test in soccer players. (United States)

    Kotsis, Yiannis; Mikellidi, Anastasia; Aresti, Cleopatra; Persia, Eleni; Sotiropoulos, Aristomenis; Panagiotakos, Demosthenes B; Antonopoulou, Smaragdi; Nomikos, Tzortzis


    The aim of the study was to investigate the effect of a 6-week, low-dose bovine colostrum (BC) supplementation on exercise-induced muscle damage (EIMD) and performance decline in soccer players following the Loughborough Intermittent Shuttle Test (LIST) during a competitive season period. In a double-blind, randomized, placebo-controlled design, two groups of soccer players were allocated to a 3.2 g/day of whey protein (WP, N = 8) or BC (N = 10) and performed a pre- and a post-supplementation LIST. Maximum isometric voluntary contraction, squat jump (SQJ), countermovement jump, muscle soreness, blood cell counts, creatine kinase (CK), C-reactive protein (CRP) and interleukin-6 (IL-6) were monitored for 2, 24, 48, 72 h post-LIST. LIST induced transient increases in leukocytes, granulocytes, CK, muscle soreness, CRP, IL-6 and declines in lymphocytes and performance indices. Supplementation resulted in a faster recovery of SQJ, CK and CRP compared to pre-supplementation kinetics (trial × time: p = 0.001, 0.056, 0.014, respectively) and lower incremental area under the curve (iAUC) for IL-6, only in the BC group [pre-: 31.1 (6.78-46.9), post-: 14.0 (-0.16 to 23.5) pg h/ml, p = 0.034]. Direct comparison of the two groups after supplementation demonstrated higher iAUC of SQJ [WP: -195.2 (-229.0 to (-52.5)), BC: -15.8 (-93.2 to 16.8) cm h, p = 0.034], a trend for lower iAUC of CK in the BC group [WP: 18,785 (4651-41,357), BC: 8842 (4807-14,802) U h/L, p = 0.081] and a significant intervention × time interaction for CRP (p = 0.038) in favor of BC. Post-exercise EIMD may be reduced and performance better maintained by a low dose of BC administration following LIST in soccer players.


    Directory of Open Access Journals (Sweden)

    Akinori Fukudomet


    Full Text Available The purpose of present study was to compare the effect of Ia afferent attenuation on the activity of alpha motor neuron (MN during concentric and eccentric action. Eight male subjects were enrolled in the present study. The experiments consisted of two sessions of MVC measurements, since all subjects performed both maximal concentric and eccentric action. EMG signals were simultaneously measured. To establish the baseline of strength, subjects were asked to perform MVC of knee extension in each session. After finishing the measurements, 20 min of vibration stimulation was applied. Immediately after finishing vibration stimulation, the MVC and AEMG were again measured. The means of MVC for concentric knee extension at pre and post- vibration stimulation were 192.2 ± 49.3 Nm and 162.3 ± 47.9 Nm, respectively. The means of MVC for eccentric knee extension at pre and post-vibration stimulation were 299.7 ± 77.0 Nm and 247.3 ± 88. 6 Nm, respectively. Two-factor repeated ANOVA detected significant differences in the MVC. Both main effects for pre-post condition (F(1,7=, p = 0.0033 and action (F(1,7=26.35, p = 0.0013 were noted. No interaction effect (action x condition was noted. The means of AEMG (vastus lateralis (VL, vastus medialis (VM, rectus femoris (RF at pre and post -vibration stimulation were decreased. Two-factor repeated ANOVA detected significant differences in AEMG (VM and VL. Both main effects for pre-post condition (VL;F(1,7=7.27, p = 0.0308, VM; F(1,7=9.55, p = 0.0175 and action (F(1,7=12.40, p = 0.0097 were noted in the VL and the VM but not in the RF. Furthermore, significant interaction (action x condition effect was noted in the VM (F(1,7=7.03, p = 0.0328 but not in the VL. The MVC and the EMG activity of the VL in response to the prolonged vibration stimulation were significantly reduced in eccentric contraction over concentric contraction. These results represented that a deactivation effect on the alpha MN of the VL during

  12. Soap film vibration: origin of the dissipation. (United States)

    Acharige, Sébastien Kosgodagan; Elias, Florence; Derec, Caroline


    We investigate the complex dispersion relationship of a transverse antisymmetric wave on a horizontal soap film. Experimentally, the complex wave number k at a fixed forcing frequency is determined by measuring the vibrating amplitude of the soap film: the wavelength (linked to the real part of k) is determined by the spatial variation of the amplitude; the decay length (linked to the imaginary part of k) is determined by analyzing the resonance curves of the vibrating wave as a function of frequency. Theoretically, we compute the complex dispersion relationship taking into account the physical properties of the bulk liquid and gas phase, and of the gas-liquid interfaces. The comparison between the computation (developed to the leading order under our experimental conditions) and the experimental results confirms that the phase velocity is fixed by the interplay between surface tension, and liquid and air inertia, as reported in previous studies. Moreover, we show that the attenuation of the transverse antisymmetric wave originates from the viscous dissipation in the gas phase surrounding the liquid film. This result is an important step in understanding the propagation of an acoustic wave in liquid foam, using a bottom-up approach.

  13. A multi-ingredient containing carbohydrate, proteins L-glutamine and L-carnitine attenuates fatigue perception with no effect on performance, muscle damage or immunity in soccer players.

    Directory of Open Access Journals (Sweden)

    Fernando Naclerio

    Full Text Available We investigated the effects of ingesting a multi-ingredient (53 g carbohydrate, 14.5 g whey protein, 5 g glutamine, 1.5 g L-carnitine-L-tartrate supplement, carbohydrate only, or placebo on intermittent performance, perception of fatigue, immunity, and functional and metabolic markers of recovery. Sixteen amateur soccer players ingested their respective treatments before, during and after performing a 90-min intermittent repeated sprint test. Primary outcomes included time for a 90-min intermittent repeated sprint test (IRS followed by eleven 15 m sprints. Measurements included creatine kinase, myoglobin, interleukine-6, Neutrophil; Lymphocytes and Monocyte before (pre, immediately after (post, 1 h and 24 h after exercise testing period. Overall, time for the IRS and 15 m sprints was not different between treatments. However, the perception of fatigue was attenuated (P<0.001 for the multi-ingredient (15.9±1.4 vs. placebo (17.8±1.4 but not for the carbohydrate (17.0±1.9 condition. Several changes in immune/inflammatory indices were noted as creatine kinase peaked at 24 h while Interleukin-6 and myoglobin increased both immediately after and at 1 h compared with baseline (P<0.05 for all three conditions. However, Myoglobin (P<0.05 was lower 1 h post-exercise for the multi-ingredient (241.8±142.6 ng·ml(-1 and CHO (265.4±187.8 ng·ml(-1 vs. placebo (518.6±255.2 ng·ml(-1. Carbohydrate also elicited lower neutrophil concentrations vs. multi-ingredient (3.9±1.5 10(9/L vs. 4.9±1.8 10(9/L, P = 0.016 and a reduced (P<0.05 monocytes count (0.36±0.09 10(9/L compared to both multi-ingredient (0.42±0.09 10(9/L and placebo (0.42±0.12 10(9/L. In conclusion, multi-ingredient and carbohydrate supplements did not improve intermittent performance, inflammatory or immune function. However, both treatments did attenuate serum myoglobin, while only carbohydrate blunted post-exercise leukocytosis.


    Directory of Open Access Journals (Sweden)

    Smirnov Vladimir Alexandrovich


    Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.

  15. Random vibrations theory and practice

    CERN Document Server

    Wirsching, Paul H; Ortiz, Keith


    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...


    Energy Technology Data Exchange (ETDEWEB)

    Martin E. Cobern


    The objective of this program is to develop a system to both monitor the vibration of a bottomhole assembly, and to adjust the properties of an active damper in response to these measured vibrations. Phase I of this program, which entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype, was completed on May 31, 2004. The principal objectives of Phase II are: more extensive laboratory testing, including the evaluation of different feedback algorithms for control of the damper; design and manufacture of a field prototype system; and, testing of the field prototype in drilling laboratories and test wells. As a result of the lower than expected performance of the MR damper noted last quarter, several additional tests were conducted. These dealt with possible causes of the lack of dynamic range observed in the testing: additional damping from the oil in the Belleville springs; changes in properties of the MR fluid; and, residual magnetization of the valve components. Of these, only the last was found to be significant. By using a laboratory demagnetization apparatus between runs, a dynamic range of 10:1 was achieved for the damper, more than adequate to produce the needed improvements in drilling. Additional modeling was also performed to identify a method of increasing the magnetic field in the damper. As a result of the above, several changes were made in the design. Additional circuitry was added to demagnetize the valve as the field is lowered. The valve was located to above the Belleville springs to reduce the load placed upon it and offer a greater range of materials for its construction. In addition, to further increase the field strength, the coils were relocated from the mandrel to the outer housing. At the end of the quarter, the redesign was complete and new parts were on order. The project is approximately three months behind schedule at this time.

  17. Research of vibration controlling based on programmable logic controller for electrostatic precipitator (United States)

    Zhang, Zisheng; Li, Yanhu; Li, Jiaojiao; Liu, Zhiqiang; Li, Qing


    In order to improve the reliability, stability and automation of electrostatic precipitator, circuits of vibration motor for ESP and vibration control ladder diagram program are investigated using Schneider PLC with high performance and programming software of Twidosoft. Operational results show that after adopting PLC, vibration motor can run automatically; compared with traditional control system of vibration based on single-chip microcomputer, it has higher reliability, better stability and higher dust removal rate, when dust emission concentrations <= 50 mg m-3, providing a new method for vibration controlling of ESP.

  18. Do whole-body vibrations affect spatial hearing? (United States)

    Frissen, Ilja; Guastavino, Catherine


    To assist the human operator, modern auditory interfaces increasingly rely on sound spatialisation to display auditory information and warning signals. However, we often operate in environments that apply vibrations to the whole body, e.g. when driving a vehicle. Here, we report three experiments investigating the effect of sinusoidal vibrations along the vertical axis on spatial hearing. The first was a free-field, narrow-band noise localisation experiment with 5- Hz vibration at 0.88 ms(-2). The other experiments used headphone-based sound lateralisation tasks. Experiment 2 investigated the effect of vibration frequency (4 vs. 8 Hz) at two different magnitudes (0.83 vs. 1.65 ms(-2)) on a left-right discrimination one-interval forced-choice task. Experiment 3 assessed the effect on a two-interval forced-choice location discrimination task with respect to the central and two peripheral reference locations. In spite of the broad range of methods, none of the experiments show a reliable effect of whole-body vibrations on localisation performance. We report three experiments that used both free-field localisation and headphone lateralisation tasks to assess their sensitivity to whole-body vibrations at low frequencies. None of the experiments show a reliable effect of either frequency or magnitude of whole-body vibrations on localisation performance.

  19. Research on a Composite Power-Superimposed Ultrasonic Vibrator for Wire Drawing

    Directory of Open Access Journals (Sweden)

    Shen Liu


    Full Text Available Vibration power and amplitude are essential factors in ultrasonic drawing processes, especially for difficult-to-draw materials like titanium and its alloys. This paper presents a new composite power-superimposed ultrasonic vibrator for wire drawing which was driven by three separate ultrasonic transducers. The transducers were uniformly distributed around the circular cross section of the vibrator, with their axes along the radial direction and pointing to the center. The vibrator can concentrate the vibrational energy of multiple transducers and transform the radial vibration into a longitudinal vibrator because of the Poisson effect and therefore output larger vibration power and amplitude. In the paper, the four-terminal network method was used to establish the vibration equations of the vibrator. The FE model was established in ANSYS to investigate its characteristics under various excitation conditions. A prototype was manufactured and measurements were performed to verify the validation of FEA results. The results matched well with the theoretical results. It was found that the composite vibrator achieved an amplitude of about 40 μm when driven by square wave signals with 120° in phase difference, which implies a potential way of applying ultrasonic vibration to the processing of difficult-to-draw materials.

  20. Assessment of hand-transmitted vibration exposure from motorized forks used for beach-cleaning operations. (United States)

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


    Motorized vibrating manure forks were used in beach-cleaning operations following the massive Deepwater Horizon oil spill in the Gulf of Mexico during the summer of 2010. The objectives of this study were to characterize the vibration emissions of these motorized forks and to provide a first approximation of hand-transmitted vibration exposures to workers using these forks for beach cleaning. Eight operators were recruited to operate the motorized forks during this laboratory study. Four fork configurations were used in the study; two motor speeds and two fork basket options were evaluated. Accelerations were measured near each hand as the operators completed the simulated beach-cleaning task. The dominant vibration frequency for these tools was identified to be around 20 Hz. Because acceleration was found to increase with motor speed, workers should consider operating these tools with just enough speed to get the job done. These forks exhibited considerable acceleration magnitudes when unloaded. The study results suggest that the motor should not be operated with the fork in the unloaded state. Anti-vibration gloves are not effective at attenuating the vibration frequencies produced by these forks, and they may even amplify the transmitted vibration and increase hand/arm fatigue. While regular work gloves are suitable, vibration-reducing gloves may not be appropriate for use with these tools. These considerations may also be generally applicable for the use of motorized forks in other workplace environments.

  1. Lattice vibrational modes and their frequency shifts in semiconductor nanowires. (United States)

    Yang, Li; Chou, M Y


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

  2. Airflow induced vibration of the Si-IT prototype

    CERN Document Server

    Dijkstra, H; De Aguiar, V; Rigo, V


    In this note we present the results of air-flow induced vibration tests performed on mechanical prototypes of the Si option of the Inner Tracker upgrade. We made a modal analyze where we observed the eigenfrequency of the Si-ladder structure at ∼30 Hz as previously measured at CERN. Flowing dry-air to cool the prototypes we do not observe a lock-in state of the vortex induced vibration (VIV). The maximum observed vibration amplitude is calculated. We conclude that the VIV excites the eigenfrequency almost independently from the air-flow speed, and with an amplitude which does not damage the structure.

  3. Frequency ranges and attenuation of macroseismic effects (United States)

    Tosi, Patrizia; De Rubeis, Valerio; Sbarra, Paola


    Macroseismic intensity is assessed on the basis of the effects caused by an earthquake. These effects reflect the expression of both the intensity and frequency of the ground motion, thus complicating prediction equation modelling. Here we analysed data of several macroseismic transitory effects caused by recent Italian earthquakes in order to study their attenuation as a function of magnitude and hypocentral distance and to obtain a specific prediction equation, of simple functional form, that could be applied to each of the effects under analysis. We found that the different attenuation behaviours could be clearly defined by the values of the specially formulated magnitude-distance scaling ratio (S), thus allowing to group the effects on the basis of the S value. The oscillation of hanging objects and liquids, together with the feeling of dizziness, were separated from most other variables, such as the effects of the earthquake on small objects, china and windows, which were caused by a vibration of higher frequency. Besides, the greater value of S, associated with the perception of the seismic sound, explained the peculiarity of this phenomenon. As a result, we recognized the frequency range associated with each effect through comparisons with the ground motion prediction equations and, in particular, with the 5 per cent damped horizontal response spectra. Here we show the importance of appropriately selecting the diagnostic elements to be used for intensity assessment in order to improve the correlation with ground motion.

  4. Design for Vibration Monitoring: A Methodology for Reliable and Cost-Effective Vibration Monitoring (United States)

    Tumer, Irem Y.; Koga, Dennis (Technical Monitor)


    The purpose of health monitoring systems is to detect failures or defects for increased safety and performance and to provide on-condition maintenance with reduced costs. The problems associated with health monitoring systems include high rates of false alarms and missed failures, which make monitoring an unreliable and costly task. The reason for this is that unaccounted variations invalidate signal modeling assumptions. Our approach was to focus on vibration monitoring of rotating components. We analyzed baseline signals to determine statistical variations, identify and model factors that influence vibrations (pre-production vs. post-production variations), determine hit and false alarm rates with baseline flight data, model and predict effects of defects and variations on vibrations, and develop algorithms and metrics for failure and anomaly detection in the presence of variations.

  5. Chaotic vortex induced vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, J.; Sheridan, J. [Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, Victoria 3800 (Australia); Leontini, J. S. [Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia); Lo Jacono, D. [Institut de Mécanique des Fluides de Toulouse (IMFT), CNRS, UPS and Université de Toulouse, 31400 Toulouse (France)


    This study investigates the nature of the dynamic response of an elastically mounted cylinder immersed in a free stream. A novel method is utilized, where the motion of the body during a free vibration experiment is accurately recorded, and then a second experiment is conducted where the cylinder is externally forced to follow this recorded trajectory. Generally, the flow response during both experiments is identical. However, particular regimes exist where the flow response is significantly different. This is taken as evidence of chaos in these regimes.

  6. Lattice Vibrations in Chlorobenzenes:

    DEFF Research Database (Denmark)

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


    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...

  7. Changes in EMG activity in the upper trapezius muscle due to local vibration exposure. (United States)

    Aström, Charlotte; Lindkvist, Markus; Burström, 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 musculoskeletal disorders has not yet been described. One suggestion has been that the vibration causes muscular fatigue. This study investigates whether vibration exposure changes the development of muscular fatigue in the trapezius muscle. Thirty-seven volunteers (men and women) performed a sub-maximal isometric shoulder elevation for 3 min. This was repeated four times, two times with induced vibration and two times without. Muscle activity was measured before and after each 3-min period to look at changes in the electromyography parameters. The result showed a significantly smaller mean frequency decrease when performing the shoulder elevation with vibration (-2.51 Hz) compared to without vibration (-4.04 Hz). There was also a slightly higher increase in the root mean square when exposed to vibration (5.7% of maximal voluntary contraction) compared to without (3.8% of maximal voluntary contraction); however, this was not statistically significant. The results of the present study indicate that short-time exposure to vibration has no negative acute effects on the fatiguing of upper trapezius muscle.

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

    Indian Academy of Sciences (India)

    Quantum dynamics of vibrational excitations and vibrational charge transfer processes in H+ + O2 collisions at collision energy 23 eV ... The Fritz Haber Research Centre and The Department of Physical Chemisry, Hebrew University of Jerusalem, Jerusalem, Israel 91904; Department of Chemistry, Indian Institute of ...

  9. Experimental identification of viscous damping in linear vibration (United States)

    Srikantha Phani, A.; Woodhouse, J.


    This paper is concerned with the experimental evaluation of the performance of viscous damping identification methods in linear vibration theory. Both existing and some new methods proposed by the present authors [A.S. Phani, J. Woodhouse, Viscous damping identification in linear vibration, Journal of Sound and Vibration 303 (3-5) (2007) 475-500] are applied to experimental data measured on two test structures: a coupled three cantilever beam with moderate modal overlap and a free-free beam with low modal overlap. The performance of each method is quantified and compared based on three norms and the best methods are identified. The role of complex modes in damping identification from vibration measurements is critically assessed.

  10. Soft tissue conduction as a possible contributor to the limited attenuation provided by hearing protection devices

    Directory of Open Access Journals (Sweden)

    Shai Chordekar


    Full Text Available Context: Damage to the auditory system by loud sounds can be avoided by hearing protection devices (HPDs such as earmuffs, earplugs, or both for maximum attenuation. However, the attenuation can be limited by air conduction (AC leakage around the earplugs and earmuffs by the occlusion effect (OE and by skull vibrations initiating bone conduction (BC. Aims: To assess maximum attenuation by HPDs and possible flanking pathways to the inner ear. Subjects and Methods: AC attenuation and resulting thresholds were assessed using the real ear attenuation at threshold (REAT procedure on 15 normal-hearing participants in four free-field conditions: (a unprotected ears, (b ears covered with earmuffs, (c ears blocked with deeply inserted customized earplugs, and (d ears blocked with both earplugs and earmuffs. BC thresholds were assessed with and without earplugs to assess the OE. Results: Addition of earmuffs to earplugs did not cause significantly greater attenuation than earplugs alone, confirming minimal AC leakage through the external meatus and the absence of the OE. Maximum REATs ranged between 40 and 46 dB, leading to thresholds of 46–54 dB HL. Furthermore, calculation of the acoustic impedance mismatch between air and bone predicted at least 60 dB attenuation of BC. Conclusion: Results do not support the notion that skull vibrations (BC contributed to the limited attenuation provided by traditional HPDs. An alternative explanation, supported by experimental evidence, suggests transmission of sound to inner ear via non-osseous pathways such as skin, soft tissues, and fluid. Because the acoustic impedance mismatch between air and soft tissues is smaller than that between air and bone, air-borne sounds would be transmitted to soft tissues more effectively than to bone, and therefore less attenuation is expected through soft tissue sound conduction. This can contribute to the limited attenuation provided by traditional HPDs. The present study

  11. Literature survey on anti-vibration gloves

    CSIR Research Space (South Africa)

    Sampson, E


    Full Text Available ............................................................................................................... 1 2. HAND ARM VIBRATION SYNDROME (HAVS).......................................................... 2 2.1 Hand-arm vibration................................................. Error! Bookmark not defined. 2.2 Human Response to vibration...

  12. Vibration Analysis of a Residential Building

    Directory of Open Access Journals (Sweden)

    Sampaio Regina Augusta


    Full Text Available The aim of this paper is to present the results of a study regarding vibration problems in a 17 storey residential building during pile driving in its vicinity. The structural design of the building was checked according to the Brazilian standards NBR6118 and NBR6123, and using commercial finite element software. An experimental analysis was also carried out using low frequency piezo-accelerometers attached to the building structure. Structure vibrations were recorded under ambient conditions. Four monitoring tests were performed on different days. The objective of the first monitoring test was an experimental modal analysis. To obtain de modal parameters, data was processed in the commercial software ARTEMIS employing two methods: the Stochastic Subspace Identification and the Frequency Domain Decomposition. Human comfort was investigated considering the International Standard ISO 2631. The Portuguese standard, NP2074, was also used as a reference, since it aims to limit the adverse effects of vibrations in structures caused by pile driving in the vicinity of the structure. The carried out experimental tests have shown that, according to ISO2301, the measure vibration levels are above the acceptance limits. However, velocity peaks are below the limits established by NP2074. It was concluded that, although the structure has adequate capacity to resist internal forces according to normative criteria, it has low horizontal stiffness, which could be verified by observing the vibration frequencies and mode shapes obtained with the finite element models, and its similarity with the experimental results. Thus, the analyses indicate the occurrence of discomfort by the residents.

  13. Vibrations in lightweight structures - Efficiency and reduction of numerical models


    Flodén, Ola


    Multi-storey wood buildings have been increasing in popularity since a century-old ban on the construction of such buildings was lifted in 1994. Compared to conventional concrete structures, it is more difficult to build lightweight structures in such a way that noise and disturbing vibrations is avoided. To design buildings of high performance regarding sound and vibrations, it is desirable to have tools for predicting the effects of structural modifications prior to construction. The long-t...

  14. Spatiotemporal analysis of normal and pathological human vocal fold vibrations. (United States)

    Krausert, Christopher R; Liang, Yufang; Zhang, Yu; Rieves, Adam L; Geurink, Kyle R; Jiang, Jack J


    For spatiotemporal analysis to become a relevant clinical tool, it must be applied to human vocal fold vibration. Receiver operating characteristic (ROC) analysis will help assess the ability of spatiotemporal parameters to detect pathological vibration. Spatiotemporal parameters of correlation length and entropy were extracted from high-speed videos of 124 subjects, 67 without vocal fold pathology and 57 with either vocal fold polyps or nodules. Mann-Whitney rank sum tests were performed to compare normal vocal fold vibrations to pathological vibrations, and ROC analysis was used to assess the diagnostic value of spatiotemporal analysis. A statistically significant difference was found between the normal and pathological groups in both correlation length (P nodules and polyps groups in either correlation length (P = .227) or entropy (P = .943). The ROC analysis showed an area under the curve of 0.63 for correlation length and 0.51 for entropy. Although they could not effectively distinguish vibration of vocal folds with nodules from those with polyps, the spatiotemporal parameters correlation length and entropy exhibit the ability to differentiate normal and pathological vocal fold vibration and may represent a diagnostic tool for objectively detecting abnormal vibration in the future, especially in neurological voice disorders and vocal folds without a visible lesion. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. Vibration Control via Stiffness Switching of Magnetostrictive Transducers (United States)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.


    This paper presents a computational study of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magnetomechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.25; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping.

  16. Experimental investigation of torsional vibration isolation using Magneto Rheological Elastomer

    Directory of Open Access Journals (Sweden)

    Praveen Shenoy K


    Full Text Available Rotating systems suffer from lateral and torsional vibrations which have detrimental effect on the roto-dynamic performance. Many available technologies such as vibration isolators and vibration absorbers deal with the torsional vibrations to a certain extent, however passive isolators and absorbers find less application when the input conditions are dynamic. The present work discusses use of a smart material called as Magneto Rheological Elastomer (MRE, whose properties can be changed based on magnetic field input, as a potential isolator for torsional vibrations under dynamic loading conditions. Carbonyl Iron Particles (CIP of average size 5 μm were mixed with RTV Silicone rubber to form the MRE. The effect of magnetic field on the system parameters was comprehended under impulse loading conditions using a custom built in-house system. Series arrangement of accelerometers were used to differentiate between the torsional and the bending modes of vibration of the system. Impact hammer tests were carried out on the torsional system to study its response, in the presence and absence of magnetic field. The tests revealed a shift in torsional frequency in the presence of magnetic field which elucidates the ability of MRE to work as a potential vibration isolator for torsional systems.

  17. Vibration Antiresonance Design for a Spacecraft Multifunctional Structure

    Directory of Open Access Journals (Sweden)

    Dong-Xu Li


    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.

  18. A Novel Wireless and Temperature-Compensated SAW Vibration Sensor

    Directory of Open Access Journals (Sweden)

    Wen Wang


    Full Text Available A novel wireless and passive surface acoustic wave (SAW based temperature-compensated vibration sensor utilizing a flexible Y-cut quartz cantilever beam with a relatively substantial proof mass and two one-port resonators is developed. One resonator acts as the sensing device adjacent to the clamped end for maximum strain sensitivity, and the other one is used as the reference located on clamped end for temperature compensation for vibration sensor through the differential approach. Vibration directed to the proof mass flex the cantilever, inducing relative changes in the acoustic propagation characteristics of the SAW travelling along the sensing device, and generated output signal varies in frequency as a function of vibration.  A theoretical mode using the Rayleigh method was established to determine the optimal dimensions of the cantilever beam. Coupling of Modes (COM model was used to extract the optimal design parameters of the SAW devices prior to fabrication. The performance of the developed SAW sensor attached to an antenna towards applied vibration was evaluated wirelessly by using the precise vibration table, programmable incubator chamber, and reader unit.  High vibration sensitivity of ~10.4 kHz/g, good temperature stability, and excellent linearity were observed in the wireless measurements.

  19. Vibrational Sensing in Marine Invertebrates (United States)


    VIBRATIONAL SENSING IN MARINE INVERTEBRATES Peter A. Jumars School of Oceanography University of Washington Box 357940 Seattle, WA 98195-7940 (206...DATES COVERED 00-00-1997 to 00-00-1997 4. TITLE AND SUBTITLE Vibrational Sensing in Marine Invertebrates 5a. CONTRACT NUMBER 5b. GRANT NUMBER

  20. Vibrations and Stability: Solved Problems

    DEFF Research Database (Denmark)

    Thomsen, Jon Juel

    Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003.......Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003....

  1. Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades (United States)

    Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas


    Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.

  2. The origins of vibration theory (United States)

    Dimarogonas, A. D.


    The Ionian School of natural philosophy introduced the scientific method of dealing with natural phenomena and the rigorous proofs for abstract propositions. Vibration theory was initiated by the Pythagoreans in the fifth century BC, in association with the theory of music and the theory of acoustics. They observed the natural frequency of vibrating systems and proved that it is a system property and that it does not depend on the excitation. Pythagoreans determined the fundamental natural frequencies of several simple systems, such as vibrating strings, pipes, vessels and circular plates. Aristoteles and the Peripatetic School founded mechanics and developed a fundamental understanding of statics and dynamics. In Alexandrian times there were substantial engineering developments in the field of vibration. The pendulum as a vibration, and probably time, measuring device was known in antiquity, and was further developed by the end of the first millennium AD.

  3. A fractional-order controller for vibration suppression of uncertain structures. (United States)

    Aghababa, Mohammad Pourmahmood


    The problem of active control of vibration structures has attracted much attention over the past decades. A general description of the control problem of vibration systems is to design an active controller to suppress the vibrations of the system induced by external disturbances such as an earthquake. In this paper, a novel fractional-order sliding mode control is introduced to attenuate the vibrations of structures with uncertainties and disturbances. After establishing a stable fractional sliding surface, a sliding mode control law is proposed. Then, the global asymptotic stability of the closed-loop system is analytically proved using fractional Lyapunov stability theorem. Finally, the robustness and applicability of the technique are verified using two examples, including a three degree of freedom structure and a two-story shear building. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

  4. Identification for Active Vibration Control of Flexible Structure Based on Prony Algorithm

    Directory of Open Access Journals (Sweden)

    Xianjun Sheng


    Full Text Available Flexible structures have been widely used in many fields due to the advantages of light quality, small damping, and strong flexibility. However, flexible structures exhibit the vibration in the process of manipulation, which reduces the pointing precision of the system and causes fatigue of the machine. So, this paper focuses on the identification method for active vibration control of flexible structure. The modal parameters and transfer function of the system are identified from the step response signal based on Prony algorithm, while the vibration is attenuated by using the input shaping technique designed according to the parameters identified from the Prony algorithm. Eventually, the proposed approach is applied to the most common flexible structure, a piezoelectric cantilever beam actuated by Macro Fiber Composite (MFC. The experimental results demonstrate that the Prony algorithm is very effective and accurate on the dynamic modeling of flexible structure and input shaper could significantly reduce the vibration and improve the response speed of system.

  5. Thickness vibrations of a piezoelectric plate with dissipation. (United States)

    Lee, Peter C Y; Liu, Ninghui; Ballato, Arthur


    The three-dimensional (3-D) equations of linear piezoelectricity with quasi-electrostatic approximation are extended to include losses attributed to the acoustic viscosity and electrical conductivity. These equations are used to investigate effects of dissipation on the propagation of plane waves in an infinite solid and forced thickness vibrations in an infinite piezoelectric plate with general symmetry. For a harmonic plane wave propagating in an arbitrary direction in an unbounded solid, the complex eigenvalue problem is solved from which the effective elastic stiffness, viscosity, and conductivity are computed. For the forced thickness vibrations of an infinite plate, the complex coupling factor K*, input admittance Y are derived and an explicit, approximate expression for K* is obtained in terms of material properties. Effects of the viscosity and conductivity on the resonance frequency, modes, admittance, attenuation coefficient, dynamic time constant, coupling factor, and quality factor are calculated and examined for quartz and ceramic barium titanate plates.

  6. Mars Pathfinder Airbag Impact Attenuation System (United States)

    Waye, Donald; Cole, J. Kenneth; Rivellini, Tommaso P.


    The Mars Pathfinder spacecraft, scheduled for launch in December 1996, is designed to validate a low cost Entry, Descent, and Landing system and to perform scientific surface operations. The Jet Propulsion Laboratory and Sandia National Laboratories teamed to design, fabricate, test and validate a prototype 0.38 scale model of an airbag impact attenuation system. A computer code was developed to predict the performance of the airbag system. A test program in Sandia's High Altitude Chamber was performed to validate the code and demonstrate the feasibility of the airbag concept and design. In addition, freefall tests were performed at representative velocities to demonstrate the structural integrity of the airbag system design. The feasibility program demonstrated that the airbag impact attenuation design will protect the lander upon impact with the Martian surface.

  7. A new vibration mechanism of balancing machine for satellite-borne spinning rotors

    Directory of Open Access Journals (Sweden)

    Wang Qiuxiao


    Full Text Available The centrifugal force and overturning moment generated by satellite-borne rotating payload have a significant impact on the stability of on-orbit satellite attitude, which must be controlled to the qualified range. For the satellite-borne rotors’ low working revs and large centroidal deviation and height, and that the horizontal vibration produced by centrifugal force is not of the same magnitude as the torsional vibration by overturning moment, the balancing machine’s measurement accuracy is low. Analysis shows that the mixture of horizontal vibration and torsional vibration of the vibrational mechanism contribute mainly to the machine’s performance, as well as the instability of vibration center position. A vibrational mechanism was put forward, in which the horizontal and torsional vibration get separated effectively by way of fixing the vibration center. From experimental results, the separation between the weak centrifugal force signal and the strong moment signal was realized, errors caused by unstable vibration center are avoided, and the balancing machine based on this vibration structure is able to meet the requirements of dynamic balancing for the satellite’s rotating payloads in terms of accuracy and stability.

  8. Development of vibrational analysis for detection of antisymmetric shells

    CERN Document Server

    Esmailzadeh-Khadem, S; Rezaee, M


    In this paper, vibrational behavior of bodies of revolution with different types of structural faults is studied. Since vibrational characteristics of structures are natural properties of system, the existence of any structural faults causes measurable changes in these properties. Here, this matter is demonstrated. In other words, vibrational behavior of a body of revolution with no structural faults is analyzed by two methods of I) numerical analysis using super sap software, II) Experimental model analysis, and natural frequencies and mode shapes are obtained. Then, different types of cracks are introduced in the structure, and analysis is repeated and the results are compared. Based on this study, one may perform crack detection by measuring the natural frequencies and mode shapes of the samples and comparing with reference information obtained from the vibration analysis of the original structure with no fault.

  9. Silicon Micromachined Sensor for Broadband Vibration Analysis (United States)

    Gutierrez, Adolfo; Edmans, Daniel; Cormeau, Chris; Seidler, Gernot; Deangelis, Dave; Maby, Edward


    The development of a family of silicon based integrated vibration sensors capable of sensing mechanical resonances over a broad range of frequencies with minimal signal processing requirements is presented. Two basic general embodiments of the concept were designed and fabricated. The first design was structured around an array of cantilever beams and fabricated using the ARPA sponsored multi-user MEMS processing system (MUMPS) process at the Microelectronics Center of North Carolina (MCNC). As part of the design process for this first sensor, a comprehensive finite elements analysis of the resonant modes and stress distribution was performed using PATRAN. The dependence of strain distribution and resonant frequency response as a function of Young's modulus in the Poly-Si structural material was studied. Analytical models were also studied. In-house experimental characterization using optical interferometry techniques were performed under controlled low pressure conditions. A second design, intended to operate in a non-resonant mode and capable of broadband frequency response, was proposed and developed around the concept of a cantilever beam integrated with a feedback control loop to produce a null mode vibration sensor. A proprietary process was used to integrat a metal-oxide semiconductor (MOS) sensing device, with actuators and a cantilever beam, as part of a compatible process. Both devices, once incorporated as part of multifunction data acquisition and telemetry systems will constitute a useful system for NASA launch vibration monitoring operations. Satellite and other space structures can benefit from the sensor for mechanical condition monitoring functions.

  10. Reducing whole body vibration in forklift drivers. (United States)

    Motmans, R


    Forklift drivers in warehouses are often exposed to whole body vibration (WBV) during the total day. There is however an association between working as a forklift operator and the development of low back pain. In this study the exposure to WBV was measured in five forklift drivers who performed a standardised order picking task during 10 minutes. The effect of driving surface (uneven concrete vs. new flat concrete), driving speed (15 km/h vs. 8 km/h) and seat suspension (mechanical suspension vs. air suspension) was investigated. Improving the driving surface was the most effective preventive measure by reducing the whole body vibration with 39%, from 1.14 to 0.69 m/s2. Lowering the speed limit resulted in a reduction of WBV with 26% (1.05 vs. 0.78 m/s2). An air suspension seat was 22% more effective compared to mechanical suspension (1.02 vs. 0.80 m/s2). On uneven concrete an air suspension seat performed even better by reducing the WBV by 29% (1.33 vs. 0.95 m/s2). A combination of a new driving surface, limiting the maximum speed and the introduction of an air suspension seat reduced the whole body vibrations below the action limit of 0.5 m/s2 as mentioned in the European directive. None of the interventions were effective enough on their own.

  11. Active isolation of vibrations with adaptive structures (United States)

    Guigou, C.; Fuller, C. R.; Wagstaff, P. R.


    Vibration transmission in structures is controlled by means of a technique which employs distributed arrays of piezoelectric transducers bonded to the supporting structure. Distributed PVDF piezoelectric strips are employed as error sensors, and a two-channel feedforward adaptive LMS algorithm is used for minimizing error signals and thereby controlling the structure. A harmonic force input excites a thick plate, and a receiving plate is configured with three pairs of piezoelectric actuators. Modal analyses are performed to determine the resonant frequencies of the system, and a scanning laser vibrometer is used to study the shape of the response of the receiving plate during excitation with and without the control algorithm. Efficient active isolation of the vibrations is achieved with modal suppression, and good control is noted in the on-resonance cases in which increased numbers of PVDF sensors and piezoelectric actuators are employed.

  12. Mistuned Vibration of Radial Inflow Turbine Impeller (United States)

    Hattori, Hiroaki; Unno, Masaru; Hayashi, Masazumi

    This paper is concerned with the numerical prediction of impeller blade vibration due to excitation by the wake of nozzle guide vanes in turbochargers. This problem is particularly important as turbochargers are used in a broad range of operation conditions, leading to some unavoidable resonant frequencies. In the paper, first the unsteady pressure distributions on the rotor blades are analyzed and structural response analysis is performed for the excitation component with largest contribution to pressure fluctuation. In a parametric survey, pressure expansion ratio and inlet flow temperature are varied in order to investigate the impact on vibration response. Unsteady CFD+FEM prediction well explains the qualitative trends that appeared in experimental survey. The result also points out that a fluctuation in natural frequency among the blades of only a few percent may cause large magnification factors. Finally, adjustment of disk thickness is suggested as a measure to reduce the magnification factor and its effectiveness demonstrated numerically as well as experimentally.

  13. Remote vibration monitoring system using wireless internet data transfer (United States)

    Lemke, John


    Vibrations from construction activities can affect infrastructure projects in several ways. Within the general vicinity of a construction site, vibrations can result in damage to existing structures, disturbance to people, damage to sensitive machinery, and degraded performance of precision instrumentation or motion sensitive equipment. Current practice for monitoring vibrations in the vicinity of construction sites commonly consists of measuring free field or structural motions using velocity transducers connected to a portable data acquisition unit via cables. This paper describes an innovative way to collect, process, transmit, and analyze vibration measurements obtained at construction sites. The system described measures vibration at the sensor location, performs necessary signal conditioning and digitization, and sends data to a Web server using wireless data transmission and Internet protocols. A Servlet program running on the Web server accepts the transmitted data and incorporates it into a project database. Two-way interaction between the Web-client and the Web server is accomplished through the use of a Servlet program and a Java Applet running inside a browser located on the Web client's computer. Advantages of this system over conventional vibration data logging systems include continuous unattended monitoring, reduced costs associated with field data collection, instant access to data files and graphs by project team members, and the ability to remotely modify data sampling schemes.

  14. Characterizing and mitigating vibrations for SCExAO (United States)

    Lozi, Julien; Guyon, Olivier; Jovanovic, Nemanja; Singh, Garima; Goebel, Sean; Norris, Barnaby; Okita, Hirofumi


    The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument, under development for the Subaru Telescope, has currently the fastest on-sky wavefront control loop, with a pyramid wavefront sensor running at 3.5 kHz. But even at that speed, we are still limited by low-frequency vibrations. The current main limitation was found to be vibrations attributed mainly to the rotation of the telescope. Using the fast wavefront sensors, cameras and accelerometers, we managed to identify the origin of most of the vibrations degrading our performance. Low-frequency vibrations are coming from the telescope drive in azimuth and elevation, as well as the elevation encoders when the target is at transit. Other vibrations were found at higher frequency coming from the image rotator inside Subaru's adaptive optics facility AO188. Different approaches are being implemented to take care of these issues. The PID control of the image rotator has been tuned to reduce their high-frequency contribution. We are working with the telescope team to tune the motor drives and reduce the impact of the elevation encoder. A Linear Quadratic Gaussian controller (LQG, or Kalman filter) is also being implemented inside SCExAO to control these vibrations. These solutions will not only improve significantly SCExAOs performance, but will also help all the other instruments on the Subaru Telescope, especially the ones behind AO188. Ultimately, this study will also help the development of the TMT, as these two telescopes share very similar drives.

  15. Vibration response of misaligned rotors (United States)

    Patel, Tejas H.; Darpe, Ashish K.


    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.

  16. Granular Media-Based Tunable Passive Vibration Suppressor (United States)

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


    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

  17. Effects of whole-body vibration exercise on the endocrine system of healthy men. (United States)

    Di Loreto, C; Ranchelli, A; Lucidi, P; Murdolo, G; Parlanti, N; De Cicco, A; Tsarpela, O; Annino, G; Bosco, C; Santeusanio, F; Bolli, G B; De Feo, P


    Whole-body vibration is reported to increase muscle performance, bone mineral density and stimulate the secretion of lipolytic and protein anabolic hormones, such as GH and testosterone, that might be used for the treatment of obesity. To date, as no controlled trial has examined the effects of vibration exercise on the human endocrine system, we performed a randomized controlled study, to establish whether the circulating concentrations of glucose and hormones (insulin, glucagon, cortisol, epinephrine, norepinephrine, GH, IGF-1, free and total testosterone) are affected by vibration in 10 healthy men [age 39 +/- 3, body mass index (BMI) of 23.5 +/- 0.5 kg/m2, mean +/- SEM]. Volunteers were studied on two occasions before and after standing for 25 min on a ground plate in the absence (control) or in the presence (vibration) of 30 Hz whole body vibration. Vibration slightly reduced plasma glucose (30 min: vibration 4.59 +/- 0.21, control 4.74 +/- 0.22 mM, p=0.049) and increased plasma norepinephrine concentrations (60 min: vibration 1.29 +/- 0.18, control 1.01 +/- 0.07 nM, p=0.038), but did not change the circulating concentrations of other hormones. These results demonstrate that vibration exercise transiently reduces plasma glucose, possibly by increasing glucose utilization by contracting muscles. Since hormonal responses, with the exception of norepinephrine, are not affected by acute vibration exposure, this type of exercise is not expected to reduce fat mass in obese subjects.

  18. Tissue vibration in prolonged running. (United States)

    Friesenbichler, Bernd; Stirling, Lisa M; Federolf, Peter; Nigg, Benno M


    The impact force in heel-toe running initiates vibrations of soft-tissue compartments of the leg that are heavily dampened by muscle activity. This study investigated if the damping and frequency of these soft-tissue vibrations are affected by fatigue, which was categorized by the time into an exhaustive exercise. The hypotheses were tested that (H1) the vibration intensity of the triceps surae increases with increasing fatigue and (H2) the vibration frequency of the triceps surae decreases with increasing fatigue. Tissue vibrations of the triceps surae were measured with tri-axial accelerometers in 10 subjects during a run towards exhaustion. The frequency content was quantified with power spectra and wavelet analysis. Maxima of local vibration intensities were compared between the non-fatigued and fatigued states of all subjects. In axial (i.e. parallel to the tibia) and medio-lateral direction, most local maxima increased with fatigue (supporting the first hypothesis). In anterior-posterior direction no systematic changes were found. Vibration frequency was minimally affected by fatigue and frequency changes did not occur systematically, which requires the rejection of the second hypothesis. Relative to heel-strike, the maximum vibration intensity occurred significantly later in the fatigued condition in all three directions. With fatigue, the soft tissue of the triceps surae oscillated for an extended duration at increased vibration magnitudes, possibly due to the effects of fatigue on type II muscle fibers. Thus, the protective mechanism of muscle tuning seems to be reduced in a fatigued muscle and the risk of potential harm to the tissue may increase. Copyright © 2010 Elsevier Ltd. All rights reserved.

  19. Tndon vibration does not alter recovery time following fatigue. (United States)

    Christie, Anita D; Miller, Nick R


    Tendon vibration has been shown to enhance muscle activity and to increase muscular endurance times. The impact of vibration on recovery from fatigue, however, is not known. This study aims to determine whether tendon vibration reduces recovery time following fatiguing contractions. Eight sedentary males (22 ± 2.8 yr) performed a fatiguing protocol of ankle dorsiflexor muscles on two separate days, with a minimum of 48 h between visits. Surface EMG was recorded from the tibialis anterior muscle while participants were performing 25 maximal voluntary contractions (MVCs), each lasting 5 s and separated by 2 s. Following the fatiguing protocol, recovery was assessed with 3-s MVC each minute over a 10-min period. Recovery time was defined as the time at which force had returned to 90% of baseline values. At one visit, vibration was applied to the distal tendon of the tibialis anterior muscle between MVCs (throughout recovery). The alternate visit involved a sham condition in which no vibration was applied. MVC force (P = 0.48) and EMG amplitude (P = 0.26) were not significantly different across testing days. Both MVC force (P fatigue protocol. However, there were no significant interaction effects for MVC force (P = 0.82) or EMG amplitude (P = 0.09), indicating similar levels of fatigue across days. With tendon vibration, MVC force recovered within 4.0 ± 2.5 min, which was not different from the sham condition (5.3 ± 1.8 min; P = 0.42). Similarly, EMG recovery time was not different between vibration condition (3.9 ± 3.8 min) and sham condition (4.9 ± 2.5 min) (P = 0.41). These results suggest that activation of excitatory group Ia afferents through tendon vibration does not substantially alter recovery time following fatigue.

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

    CERN Document Server

    Wilson, E Bright; Cross, Paul C


    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.

  1. Avoid heat transfer equipment vibration

    Energy Technology Data Exchange (ETDEWEB)

    Ganapathy, V.


    Tube bundles in heat exchangers, boilers, superheaters and heaters are often subject to vibration and noise problems. Vibration can lead to tube thinning and wear, resulting in tube failures. Excessive noise can be a problem to plant operating personnel. Large gas pressure drop across the equipment is also a side effect, which results in large operating costs. With the design checks presented in this paper, one can predict during design if problems associated with noise and vibration are likely to occur in petroleum refineries.


    Directory of Open Access Journals (Sweden)

    Kazimierz Zaleski


    Full Text Available The article presents the results of studies on the effect of technological parameters of vibration shot peening upon the shape of bearing curves and the parameters of that curve. The topography of surface formed in result of vibration shot peening and pre-machining, which was grinding, were analyzed. The material used in the studies was alloy steel 30HGSA. The shot peening process was performed on an appliance equipped with a kinematic vibrator. Shot peening time t, vibrator oscillations (vibrations frequency ν, as well as vibrator oscillations amplitude A were changed within: t = 1–15 min, ν = 17,5–35 Hz, A = 10,3–17,3 mm. For measuring surface roughness and determining the bearing curve the appliance T8000 RC120-400 by Hommel-Etamic was used together with the software. In result of the machining performed surface roughness decreased, and the parameters of bearing curve improved.

  3. Experimental and theoretical investigation of passive damping concepts for member forced and free vibration (United States)

    Razzaq, Zia; Mykins, David W.


    Potential passive damping concepts for use in space structures are identified. The effectiveness of copper brush, wool swab, and silly putty in chamber dampers is investigated through natural vibration tests on a tubular aluminum member. The member ends have zero translation and possess partial rotational restraints. The silly putty in chamber dampers provide the maximum passive damping efficiency. Forced vibration tests are then conducted with one, two, and three damper chambers containing silly putty. Owing to the limitation of the vibrator used, the performance of these dampers could not be evaluated experimentally until the forcing function was disengaged. Nevertheless, their performance is evaluated through a forced dynamic finite element analysis conducted as a part of this investigation. The theoretical results based on experimentally obtained damping ratios indicate that the passive dampers are considerably more effective under member natural vibration than during forced vibration. Also, the maximum damping under forced vibration occurs at or near resonance.

  4. EMC characteristics of composite structure - Electric/electromagnetic shielding attenuation (United States)

    Wegertseder, P.; Breitsameter, R.


    The paper reports electric/electromagnetic shielding-attenuation experiments performed on different test boxes built with the same materials and processes as those to be used for the construction of a helicopter. The measurements are performed in the frequency range of 14 to 18 GHz, and the effects of different composite materials, jointing and bonding of structure parts of the boxes, application and bonding of the mesh, the construction of access panels, and conductive seals on these panels are assessed. It is demonstrated that moderate electric/electromagnetic shielding-attenuation values can be achieved by composite structures made from carbon, and materials and procedures required for high shielding attenuation are discussed.

  5. Bridge Condition Assessment based on Vibration Responses of Passenger Vehicle (United States)

    Miyamoto, Ayaho; Yabe, Akito


    In this paper, we propose a new method of assessing the condition of existing short- and medium-span reinforced/prestressed concrete bridges based on vibration monitoring data obtained from a public bus. This paper not only describes details of a prototype monitoring system that uses information technology and sensors capable of providing more accurate knowledge of bridge performance than conventional ways but also shows a few specific examples of bridge condition assessment based on vehicle vibrations measured by using an in-service public bus equipped with vibration measurement instrumentation. This paper also describes a sensitivity analysis of deteriorating bridges based on simulation of the acceleration response of buses conducted by the "substructure method" employing a finite element model to verify the above bridge performance results. The main conclusions obtained in this study can be summarized as follows: (1) Because the vibration responses of passenger vehicles, such as buses, have a good linear relationship with the vibration responses of the target bridges, the proposed system can be used as a practical monitoring system for bridge condition assessment. (2) The results of sensitivity analysis performed by the substructure method show that bus vibration responses are useful for evaluating target bridge performance. (3) The proposed method was applied to a network of real bridges in a local area to evaluate its effectiveness. The results indicate that the proposed method can be used to prioritize the repair/strengthening works of existing bridges based on various vibration information in order to help bridge administrators establish rational maintenance strategies.

  6. Bridge Condition Assessment based on Vibration Responses of Passenger Vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Miyamoto, Ayaho [Graduate School of Science and Engineering, Yamaguchi University, Ube (Japan); Yabe, Akito, E-mail:, E-mail: [Seismic Engineering Department, KOZO KEIKAKU Engineering Inc. Tokyo (Japan)


    In this paper, we propose a new method of assessing the condition of existing short- and medium-span reinforced/prestressed concrete bridges based on vibration monitoring data obtained from a public bus. This paper not only describes details of a prototype monitoring system that uses information technology and sensors capable of providing more accurate knowledge of bridge performance than conventional ways but also shows a few specific examples of bridge condition assessment based on vehicle vibrations measured by using an in-service public bus equipped with vibration measurement instrumentation. This paper also describes a sensitivity analysis of deteriorating bridges based on simulation of the acceleration response of buses conducted by the 'substructure method' employing a finite element model to verify the above bridge performance results. The main conclusions obtained in this study can be summarized as follows: (1) Because the vibration responses of passenger vehicles, such as buses, have a good linear relationship with the vibration responses of the target bridges, the proposed system can be used as a practical monitoring system for bridge condition assessment. (2) The results of sensitivity analysis performed by the substructure method show that bus vibration responses are useful for evaluating target bridge performance. (3) The proposed method was applied to a network of real bridges in a local area to evaluate its effectiveness. The results indicate that the proposed method can be used to prioritize the repair/strengthening works of existing bridges based on various vibration information in order to help bridge administrators establish rational maintenance strategies.

  7. 14 CFR 33.63 - Vibration. (United States)


    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.63 Section 33.63 Aeronautics... 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. ...

  8. 14 CFR 33.83 - Vibration test. (United States)


    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.83 Section 33.83... STANDARDS: AIRCRAFT ENGINES Block Tests; Turbine Aircraft Engines § 33.83 Vibration test. (a) Each engine must undergo vibration surveys to establish that the vibration characteristics of those components that...

  9. 14 CFR 33.33 - Vibration. (United States)


    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration. 33.33 Section 33.33 Aeronautics... STANDARDS: AIRCRAFT ENGINES Design and Construction; Reciprocating Aircraft Engines § 33.33 Vibration. The... vibration and without imparting excessive vibration forces to the aircraft structure. ...

  10. 14 CFR 33.43 - Vibration test. (United States)


    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Vibration test. 33.43 Section 33.43... STANDARDS: AIRCRAFT ENGINES Block Tests; Reciprocating Aircraft Engines § 33.43 Vibration test. (a) Each engine must undergo a vibration survey to establish the torsional and bending vibration characteristics...

  11. 49 CFR 178.819 - Vibration test. (United States)


    ... 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...

  12. Rectangular Parallelepiped Vibration in Plane Strain State


    Hanckowiak, Jerzy


    In this paper we present a vibration spectrum of a homogenous parallelepiped (HP) under the action of volume and surface forces resulting from the exponent displacements entering the Fourier transforms. Vibration under the action of axial surface tractions and the free vibration are described separately. A relationship between the high frequency vibration and boundary conditions (BC) is also considered.

  13. Vibration reduction for vision systems on board unmanned aerial vehicles using a neuro-fuzzy controller


    Marichal, N.; Tomas-Rodriguez, M.; Hernandez, A.; Castillo, S; Campoy, P.


    In this paper, an intelligent control approach based on neuro-fuzzy systems performance is presented, with the objective of counteracting the vibrations that affect the low-cost vision platform onboard an unmanned aerial system of rotating nature. A scaled dynamical model of a helicopter is used to simulate vibrations on its fuselage. The impact of these vibrations on the low-cost vision system will be assessed and an intelligent control approach will be derived in order to reduce its detrime...

  14. Damping Transversal Vibrations of the Offset Cylinder of the Offset Press

    Directory of Open Access Journals (Sweden)

    Eglė Šalvienė


    Full Text Available Investigation into the influence of a dynamic vibration damper on the intensity of the absolute forced transversal vibrations of the blanket cylinder of the web printing offset press was performed. The analytical and numerical examination of the dynamic model of the cylinder was done. The obtained results have disclosed that the application of the damper decreases the intensity of printing cylinder vibrations.Article in Lithuanian

  15. Lessons Learned on the Application of Vibration Absorbers for Enhanced Cannon Stabilization

    Directory of Open Access Journals (Sweden)

    Eric Kathe


    Full Text Available This paper will summarize the successful application of muzzle-end vibration absorbers to reduce cannon vibration. This technology constitutes a weapons stabilization approach that focuses on passive mechanical structural modification of the cannon, rather than relying upon an external control law to actively cancel vibrations. Challenges encountered during field testing, non-ideal behavior, and performance evaluation using digital signal processing will be highlighted.

  16. Continuum vibration analysis of dielectric elastomer membranes (United States)

    Nalbach, S.; Rizzello, G.; Seelecke, S.


    Dielectric Elastomer (DE) transducers are well known for the possibility of responding to an applied voltage with relatively large actuation strains, often larger than 100%, and for their relatively high actuation bandwidth (order of several kHz). However, up to date there are relatively few applications which use the dynamic behavior of DEs. Some relevant examples include loudspeakers and fluid dispensers. Motivated by the potentialities of DEs in high-frequency applications, the aim of this work is the investigation of the continuous vibrations observed when DE membranes are actuated electrically. The system under analysis consists of a circular DE membrane pre-loaded with a spring. While exciting the DE membrane actuator with high-voltage, high-frequency signals, the motion of the membrane is detected with a 3D laser vibrometer which uses Doppler effect to reconstruct the system spectrum and vibration modes. An extensive experimental investigation is performed to study the influence of system parameters, such as membrane geometry and pre-stress, on the membrane frequency spectrum and vibrational modes.

  17. Vibrational Spectroscopy in Studies of Atmospheric Corrosion

    Directory of Open Access Journals (Sweden)

    Saman Hosseinpour


    Full Text Available Vibrational spectroscopy has been successfully used for decades in studies of the atmospheric corrosion processes, mainly to identify the nature of corrosion products but also to quantify their amounts. In this review article, a summary of the main achievements is presented with focus on how the techniques infrared spectroscopy, Raman spectroscopy, and vibrational sum frequency spectroscopy can be used in the field. Several different studies have been discussed where these instruments have been used to assess both the nature of corrosion products as well as the properties of corrosion inhibitors. Some of these techniques offer the valuable possibility to perform in-situ measurements in real time on ongoing corrosion processes, which allows the kinetics of formation of corrosion products to be studied, and also minimizes the risk of changing the surface properties which may occur during ex-situ experiments. Since corrosion processes often occur heterogeneously over a surface, it is of great importance to obtain a deeper knowledge about atmospheric corrosion phenomena on the nano scale, and this review also discusses novel vibrational microscopy techniques allowing spectra to be acquired with a spatial resolution of 20 nm.

  18. Vibrational Damping of Composite Materials


    Biggerstaff, Janet M.


    The purpose of this research was to develop new methods of vibrational damping in polymeric composite materials along with expanding the knowledge of currently used vibrational damping methods. A new barrier layer technique that dramatically increased damping in viscoelastic damping materials that interacted with the composite resin was created. A method for testing the shear strength of damping materials cocured in composites was developed. Directional damping materials, where the loss facto...

  19. 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....

  20. Harmonic vibrations of multispan beams

    DEFF Research Database (Denmark)

    Dyrbye, Claes


    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...... the n´th and the (n+1)´th eigenfrequency. The reason for this phenomenon is explained.Keywords: Vibrations, Eigenfrequencies, Beams....

  1. Smart accelerometer. [vibration damage detection (United States)

    Bozeman, Richard J., Jr. (Inventor)


    The invention discloses methods and apparatus for detecting vibrations from machines which indicate an impending malfunction for the purpose of preventing additional damage and allowing for an orderly shutdown or a change in mode of operation. The method and apparatus is especially suited for reliable operation in providing thruster control data concerning unstable vibration in an electrical environment which is typically noisy and in which unrecognized ground loops may exist.

  2. Improved Predictions for Geotechnical Vibrations


    Macijauskas, Darius


    In urban areas where the infrastructure is dense and construction of new structures is near existing and sensitive buildings, frequently vibrations, caused by human activities, occur. Generated waves in the soil may adversely affect surrounding buildings. These vibrations have to be predicted a priori by using currently available knowledge of the soil dynamics. Current research, conducted by Deltares research institute, showed that the reliability of methods for prediction of m...

  3. Stress analysis of vibrating pipelines (United States)

    Zachwieja, Janusz


    The pipelines are subject to various constraints variable in time. Those vibrations, if not monitored for amplitude and frequency, may result in both the fatigue damage in the pipeline profile at high stress concentration and the damage to the pipeline supports. If the constraint forces are known, the system response may be determined with high accuracy using analytical or numerical methods. In most cases, it may be difficult to determine the constraint parameters, since the industrial pipeline vibrations occur due to the dynamic effects of the medium in the pipeline. In that case, a vibration analysis is a suitable alternative method to determine the stress strain state in the pipeline profile. Monitoring the pipeline vibration levels involves a comparison between the measured vibration parameters and the permissible values as depicted in the graphs for a specific pipeline type. Unfortunately, in most cases, the studies relate to the petrochemical industry and thus large diameter, long and straight pipelines. For a pipeline section supported on both ends, the response in any profile at the entire section length can be determined by measuring the vibration parameters at two different profiles between the pipeline supports. For a straight pipeline section, the bending moments, variable in time, at the ends of the analysed section are a source of the pipe excitation. If a straight pipe section supported on both ends is excited by the bending moments in the support profile, the starting point for the stress analysis are the strains, determined from the Euler-Bernoulli equation. In practice, it is easier to determine the displacement using the experimental methods, since the factors causing vibrations are unknown. The industrial system pipelines, unlike the transfer pipelines, are straight sections at some points only, which makes it more difficult to formulate the equation of motion. In those cases, numerical methods can be used to determine stresses using the

  4. Vibrational spectroscopic characterization of fluoroquinolones (United States)

    Neugebauer, U.; Szeghalmi, A.; Schmitt, M.; Kiefer, W.; Popp, J.; Holzgrabe, U.


    Quinolones are important gyrase inhibitors. Even though they are used as active agents in many antibiotics, the detailed mechanism of action on a molecular level is so far not known. It is of greatest interest to shed light on this drug-target interaction to provide useful information in the fight against growing resistances and obtain new insights for the development of new powerful drugs. To reach this goal, on a first step it is essential to understand the structural characteristics of the drugs and the effects that are caused by the environment in detail. In this work we report on Raman spectroscopical investigations of a variety of gyrase inhibitors (nalidixic acid, oxolinic acid, cinoxacin, flumequine, norfloxacin, ciprofloxacin, lomefloxacin, ofloxacin, enoxacin, sarafloxacin and moxifloxacin) by means of micro-Raman spectroscopy excited with various excitation wavelengths, both in the off-resonance region (532, 633, 830 and 1064 nm) and in the resonance region (resonance Raman spectroscopy at 244, 257 and 275 nm). Furthermore DFT calculations were performed to assign the vibrational modes, as well as for an identification of intramolecular hydrogen bonding motifs. The effect of small changes in the drug environment was studied by adding successively small amounts of water until physiological low concentrations of the drugs in aqueous solution were obtained. At these low concentrations resonance Raman spectroscopy proved to be a useful and sensitive technique. Supplementary information was obtained from IR and UV/vis spectroscopy.

  5. Modeling of Axial Spring Stiffness in Active Vibration Controlled Drilling

    Directory of Open Access Journals (Sweden)

    Pao William


    Full Text Available During drilling process, substantial amount of vibration and shock are induced to the drill string. Active vibration controlled drilling is introduced to reduce the vibration and increase the efficiency of drilling process. In this system, two main components that determine the damping coefficient are magnetorheological (MR damper and spring assembly. Performance of vibration damping system is depending on the viscosity of MR fluid in the damper and spring constant of spring assembly. One of the key issues that are unclear from the design is the correlation between the axial spring stiffness configuration and the damping force which needs to be tuned actively. There has been lack of studies on how the viscosity of MR fluid on the active vibration damper affects the damping stiffness of the whole system. The objective of the project is to extract the correlations for the viscous damping coefficient, equivalent spring stiffness and power input to the system. Simplified vibration model is thus created using Simulink, together with experimental data fed from APS Technology’s in-house team. Inputs of the simulation such as force exerted, mass of mandrel, spring constant and step time are based on the experimental data and can be adjusted to suit different experiments. By having the model, behavior of the system can be studied and analyzed. From the simulation, it is also observed that the relationship between damping coefficient and power input of the system is linear.

  6. A vibration correction method for free-fall absolute gravimeters (United States)

    Qian, J.; Wang, G.; Wu, K.; Wang, L. J.


    An accurate determination of gravitational acceleration, usually approximated as 9.8 m s‑2, has been playing an important role in the areas of metrology, geophysics, and geodetics. Absolute gravimetry has been experiencing rapid developments in recent years. Most absolute gravimeters today employ a free-fall method to measure gravitational acceleration. Noise from ground vibration has become one of the most serious factors limiting measurement precision. Compared to vibration isolators, the vibration correction method is a simple and feasible way to reduce the influence of ground vibrations. A modified vibration correction method is proposed and demonstrated. A two-dimensional golden section search algorithm is used to search for the best parameters of the hypothetical transfer function. Experiments using a T-1 absolute gravimeter are performed. It is verified that for an identical group of drop data, the modified method proposed in this paper can achieve better correction effects with much less computation than previous methods. Compared to vibration isolators, the correction method applies to more hostile environments and even dynamic platforms, and is expected to be used in a wider range of applications.

  7. Vibrationally assisted electron transfer mechanism of olfaction: myth or reality? (United States)

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


    Smell is a vital sense for animals. The mainstream explanation of smell is based on recognition of the odorant molecules through characteristics of their surface, e.g., shape, but certain experiments suggest that such recognition is complemented by recognition of vibrational modes. According 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, thereby, recent experiments performed on Drosophila melanogaster. Our demonstration is based on known physical properties of biological electron transfer and on ab initio calculations on odorants carried out for the purpose of the present study. We identify a range of physical characteristics which 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 homology modeling.

  8. Vibrational modes of nanolines (United States)

    Heyliger, Paul R.; Flannery, Colm M.; Johnson, Ward L.


    Brillouin-light-scattering spectra previously have been shown to provide information on acoustic modes of polymeric lines fabricated by nanoimprint lithography. Finite-element methods for modeling such modes are presented here. These methods provide a theoretical framework for determining elastic constants and dimensions of nanolines from measured spectra in the low gigahertz range. To make the calculations feasible for future incorporation in inversion algorithms, two approximations of the boundary conditions are employed in the calculations: the rigidity of the nanoline/substrate interface and sinusoidal variation of displacements along the nanoline length. The accuracy of these approximations is evaluated as a function of wavenumber and frequency. The great advantage of finite-element methods over other methods previously employed for nanolines is the ability to model any cross-sectional geometry. Dispersion curves and displacement patterns are calculated for modes of polymethyl methacrylate nanolines with cross-sectional dimensions of 65 nm × 140 nm and rectangular or semicircular tops. The vibrational displacements and dispersion curves are qualitatively similar for the two geometries and include a series of flexural, Rayleigh-like, and Sezawa-like modes. This paper is a contribution of the National Institute of Standards and Technology and is not subject to copyright in the United States.

  9. Harmonic vibrations and waves in a cylindrical helically anisotropic shell (United States)

    Panfilov, I. A.; Ustinov, Yu. A.


    A Kirchhoff-Love type applied theory is used to study the specific characteristics of harmonic waves and vibrations of a helically anisotropic shell. Special attention is paid to axisymmetric and bending vibrations. In both cases, the dispersion equations are constructed and a qualitative and numerical analysis of their roots and the corresponding elementary solutions is performed. It is shown that the skew anisotropy in the axisymmetric case generates a relation between the longitudinal and torsional vibrations which is mathematically described by the amplitude coefficients of homogeneous waves. In the case of a shell with rigidly fixed end surfaces, the dependence of the first two natural frequencies on the shell length and the helical line slope α, i.e., the geometric parameter of helical anisotropy, is studied. A boundary value problem in which longitudinal vibrations are generated on one of the end surfaces and the other end is free of forces and moments is considered to analyze the degree of transformation of longitudinal vibrations into longitudinally torsional vibrations. In the case of bending vibrations, two problems for a half-infinite shell are studied as well. In the first problem, the waves are excited kinematically by generating harmonic vibrations of the shell end surface in the plane of the axial cross-section, and it is shown that the axis generally moves in some closed trajectories far from the end surface. In the second problem, the reflection of a homogeneous wave incident on the shell end is examined. It is shown that the "boundary resonance" phenomenon can arise in some cases.

  10. Micro-jitter attenuation of spaceborne cooler by using a blade-type hyperelastic shape memory alloy passive isolator (United States)

    Kwon, Seong-Cheol; Jeon, Young-Hyeon; Oh, Hyun-Ung


    In this study, the primary design objective is to develop a passive isolator that can guarantee structural safety of the cooler assembly in a launch vibration environment without a launch locking mechanism, while effectively isolating the cooler-induced micro-jitter during the on-orbit operation of the cooler. To achieve the design objective, we focused on the utilization of characteristics of the hyperelastic shape memory effects. The major advantage of the isolator is that the micro-jitter isolation performance is much less sensitive to the aligned position of the isolator in comparison with the conventional isolator. Moreover, implementation of an additional 0g compensation device during a satellite level on-ground test, such as a jitter measurement test, is not required. In this study, the basic characteristics of the isolator were measured using the torque test and free vibration test. The micro-jitter attenuation capability and position sensitivity of the proposed isolator design were validated by the micro-jitter measurement test.

  11. Attenuated radon transform: theory and application in medicine and biology

    Energy Technology Data Exchange (ETDEWEB)

    Gullberg, G.T.


    A detailed analysis is given of the properties of the attenuated Radon transform and of how increases in photon attenuation influence the numerical accuracy and computation efficiency of iterative and convolution algorithms used to determine its inversion. The practical applications for this work involve quantitative assessment of the distribution of injected radiopharmaceuticals and radionuclides in man and animals for basic physiological and biochemical studies as well as clinical studies in nuclear medicine. A mathematical structure is developed using function theory and the theory of linear operators on Hilbert spaces which lends itself to better understanding the spectral properties of the attenuated Radon transform. The continuous attenuated Radon transform reduces to a matrix operator for discrete angular and lateral sampling, and the reconstruction problem reduces to a system of linear equations. For the situation of variable attenuation coefficient frequently found in nuclear medicine applications of imaging the heart and chest, the procedure developed in this thesis involves iterative techniques of performing the generalized inverse. For constant attenuation coefficient less than 0.15 cm/sup -1/, convolution methods can reliably reconstruct a 30 cm object with 0.5 cm resolution. However, for high attenuation coefficients or for the situation where there is variable attenuation such as reconstruction of distribution of isotopes in the heart, iterative techniques developed in this thesis give the best results. (ERB)

  12. Shunted Piezoelectric Vibration Damping Analysis Including Centrifugal Loading Effects (United States)

    Min, James B.; Duffy, Kirsten P.; Provenza, Andrew J.


    Excessive vibration of turbomachinery blades causes high cycle fatigue problems which require damping treatments to mitigate vibration levels. One method is the use of piezoelectric materials as passive or active dampers. Based on the technical challenges and requirements learned from previous turbomachinery rotor blades research, an effort has been made to investigate the effectiveness of a shunted piezoelectric for the turbomachinery rotor blades vibration control, specifically for a condition with centrifugal rotation. While ample research has been performed on the use of a piezoelectric material with electric circuits to attempt to control the structural vibration damping, very little study has been done regarding rotational effects. The present study attempts to fill this void. Specifically, the objectives of this study are: (a) to create and analyze finite element models for harmonic forced response vibration analysis coupled with shunted piezoelectric circuits for engine blade operational conditions, (b) to validate the experimental test approaches with numerical results and vice versa, and (c) to establish a numerical modeling capability for vibration control using shunted piezoelectric circuits under rotation. Study has focused on a resonant damping control using shunted piezoelectric patches on plate specimens. Tests and analyses were performed for both non-spinning and spinning conditions. The finite element (FE) shunted piezoelectric circuit damping simulations were performed using the ANSYS Multiphysics code for the resistive and inductive circuit piezoelectric simulations of both conditions. The FE results showed a good correlation with experimental test results. Tests and analyses of shunted piezoelectric damping control, demonstrating with plate specimens, show a great potential to reduce blade vibrations under centrifugal loading.

  13. Tennis Racket Vibrations and Shock Transmission to the Wrist during Forehand Drive. (United States)

    Rogowski, Isabelle; Creveaux, Thomas; Triquigneaux, Sylvain; Macé, Pierre; Gauthier, Fabien; Sevrez, Violaine


    This study aimed to investigate the effects of two different racket models and two different forehand drive velocities on the three-dimensional vibration behavior of the racket and shock transmission to the player's wrist under real playing conditions. Nine tennis players performed a series of crosscourt flat forehand drives at two velocities, using a lightly and a highly vibrant racket. Two accelerometers were fixed on the racket frame and the player's wrist. The analysis of vibration signals in both time and frequency domains showed no interaction effect of velocity and racket conditions either on the racket vibration behavior or on shock transmission. An increase in playing velocity enlarged the amount of vibrations at the racket and wrist, but weakly altered their frequency content. As compared to a racket perceived as highly vibrating, a racket perceived as lightly vibrating damped longer in the out-of-plane axis of the racket and shorter on the other axis of the racket and on the wrist, and displayed a lower amount of energy in the high frequency of the vibration signal at the racket and wrist. These findings indicated that the playing velocity must be controlled when investigating the vibration loads due to the racket under real playing conditions. Similarly, a reduced perception of vibration by the tennis player would be linked to decreased amplitude of the racket vibration signal, which may concentrate the signal energy in the low frequencies.

  14. Vibration measurements of high-heat-load monochromators for DESY PETRA III extension

    Energy Technology Data Exchange (ETDEWEB)

    Kristiansen, Paw, E-mail: [FMB Oxford Ltd, Unit 1 Ferry Mills, Oxford OX2 0ES (United Kingdom); Horbach, Jan; Döhrmann, Ralph; Heuer, Joachim [DESY, Deutsches Elektronen-Synchrotron Hamburg, Notkestrasse 85, 22607 Hamburg (Germany)


    Vibration measurements of a cryocooled double-crystal monochromator are presented. The origins of the vibrations are identified. The minimum achieved vibration of the relative pitch between the two crystals is 48 nrad RMS and the minimum achieved absolute vibration of the second crystal is 82 nrad RMS. The requirement for vibrational stability of beamline optics continues to evolve rapidly to comply with the demands created by the improved brilliance of the third-generation low-emittance storage rings around the world. The challenge is to quantify the performance of the instrument before it is installed at the beamline. In this article, measurement techniques are presented that directly and accurately measure (i) the relative vibration between the two crystals of a double-crystal monochromator (DCM) and (ii) the absolute vibration of the second-crystal cage of a DCM. Excluding a synchrotron beam, the measurements are conducted under in situ conditions, connected to a liquid-nitrogen cryocooler. The investigated DCM utilizes a direct-drive (no gearing) goniometer for the Bragg rotation. The main causes of the DCM vibration are found to be the servoing of the direct-drive goniometer and the flexibility in the crystal cage motion stages. It is found that the investigated DCM can offer relative pitch vibration down to 48 nrad RMS (capacitive sensors, 0–5 kHz bandwidth) and absolute pitch vibration down to 82 nrad RMS (laser interferometer, 0–50 kHz bandwidth), with the Bragg axis brake engaged.

  15. Free vibration analysis of linear particle chain impact damper (United States)

    Gharib, Mohamed; Ghani, Saud


    produces a smaller contact force for each mass while maintaining the same effect of the single unit impact damper. The analytical and experimental work showed that the multiunit impact damper is more functional than the conventional single unit impact damper in reducing noise and vibration [17]. The bean bag impact damper is considered as another form of multiunit impact damper. It consists of a flexible bag packed with small spherical particles (e.g. lead shots). The resilience of the damper can be varied by adjusting the tightness of the flexible bag. It is found that the bean bag impact damper is better than the conventional impact damper in vibration suppression, contact forces reductions, and noise attenuation [19]. The particle/granular impact damper consists of a cavity(s) filled with ceramic/metal particles or powders with small granule sizes. Better damping performances are achieved when using metal particles with high density (lead or tungsten steel) [23]. Other investigations recommended using multiple particle impact dampers that involve friction, impact and shear mechanisms to achieve optimal damping effect [22]. The resilient impact damper is similar to the conventional impact dampers. The only difference is that the deformation of the impact damper with the stops during the collision is taken into account [24]. The buffered impact damper is an extension of the resilient impact damper by adding a flexible buffer layer to the stops to absorb the energy of the moving mass. The experimental work shows that the buffer zone reduces the impact forces, avoids high acceleration and reduces the contact forces by absorbing more of the impact energy and increasing the contact time [25].

  16. Measurement of ground and nearby building vibration and noise induced by trains in a metro depot. (United States)

    Zou, Chao; Wang, Yimin; Wang, Peng; Guo, Jixing


    Metro depots are where subway trains are parked and where maintenance is carried out. They usually occupy the largest ground areas in metro projects. Due to land utilization problems, Chinese cities have begun to develop over-track buildings above metro depots for people's life and work. The frequently moving trains, when going into and out of metro depots, can cause excessive vibration and noise to over-track buildings and adversely affect the living quality of the building occupants. Considering the current need of reliable experimental data for the construction of metro depots, field measurements of vibration and noise on the ground and inside a nearby 3-story building subjected to moving subway trains were conducted in a metro depot at Guangzhou, China. The amplitudes and frequency contents of velocity levels were quantified and compared. The composite A-weighted equivalent sound levels and maximum sound levels were captured. The predicted models for vibration and noise of metro depot were proposed based on existing models and verified. It was found that the vertical vibrations were significantly greater than the horizontal vibrations on the ground and inside the building near the testing line. While at the throat area, the horizontal vibrations near the curved track were remarkably greater than the vertical vibrations. The attenuation of the vibrations with frequencies above 50 Hz was larger than the ones below 50 Hz, and the frequencies of vibration transmitting to adjacent buildings were mainly within 10-50 Hz. The largest equivalent sound level generated in the throat area was smaller than the testing line one, but the instantaneous maximum sound level induced by wheels squeal, contact between wheels and rail joints as well as turnout was close to or even greater than the testing line one. The predicted models gave a first estimation for design and assessment of newly built metro depots. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. LCLS XTOD Attenuator System System Concept Report

    Energy Technology Data Exchange (ETDEWEB)

    Kishiyama, K; Roeben, M; Trent, J; Ryutov, D; Shen, S


    The attenuator system for the Linac Coherent Light Source (LCLS) X-ray Transport, Optics and Diagnostics (XTOD) system has been configured and analyzed by the Lawrence Livermore National Laboratory's New Technologies Engineering Division (NTED) as requested by the SLAC/LCLS program. The system layout, performance analyses and selection of the vacuum components are presented in this System Conceptual Review (SCR) report. Also included are the plans for prototype, procurement, mechanical integration, and the cost estimates.

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

    Directory of Open Access Journals (Sweden)

    Felix Weber


    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.

  19. Signal Processing Methods for Removing the Effects of Whole Body Vibration upon Speech (United States)

    Bitner, Rachel M.; Begault, Durand R.


    Humans may be exposed to whole-body vibration in environments where clear speech communications are crucial, particularly during the launch phases of space flight and in high-performance aircraft. Prior research has shown that high levels of vibration cause a decrease in speech intelligibility. However, the effects of whole-body vibration upon speech are not well understood, and no attempt has been made to restore speech distorted by whole-body vibration. In this paper, a model for speech under whole-body vibration is proposed and a method to remove its effect is described. The method described reduces the perceptual effects of vibration, yields higher ASR accuracy scores, and may significantly improve intelligibility. Possible applications include incorporation within communication systems to improve radio-communication systems in environments such a spaceflight, aviation, or off-road vehicle operations.

  20. Electron--impact resonant vibration excitation cross sections and rate coefficients for carbon monoxide

    CERN Document Server

    Laporta, V; Tennyson, J; Celiberto, R; 10.1088/0963-0252/21/4/045005


    Resonant vibrational and rotation-vibration excitation cross sections for electron-CO scattering are calculated in the 0-10 eV energy range for all 81 vibrational states of CO, assuming that the excitation occur via the 2{\\Pi} shape resonance. Static exchange plus polarization calculations performed using the R-matrix method are used to estimate resonance positions and widths as functions of internuclear separation. The effects of nuclear motion are considered using a local complex potential model. Good agreement is obtained with available experimental data on excitation from the vibrational ground state. Excitation rates and cross sections are provided as a functions of the initial CO vibrational state for all ground state vibrational levels.

  1. Spherical tuned liquid damper for vibration control in wind turbines

    DEFF Research Database (Denmark)

    Chen, Jun-Ling; Georgakis, Christos T.


    A tuned liquid damper (TLD), which consisted of two-layer hemispherical containers, partially filled with water, was investigated as a cost-effective method to reduce the wind-induced vibration of wind turbines. A 1/20 scaled test model was designed to investigate its performance on the shaking...... table. Three groups of equivalent ground accelerations were inputted to simulate the wind-induced dynamic response under different load cases. The influence of rotors and nacelle was assumed to be a concentrated tip mass. A series of free and forced vibration experiments were performed on the shaking...

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


    樹野, 淳也; 前田, 節雄; 横田, 和樹; 平, 雄一郎


    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...

  3. Adaptive PI control strategy for flat permanent magnet linear synchronous motor vibration suppression (United States)

    Meng, Fanwei; Liu, Chengying; Li, Zhijun; Wang, Liping


    Due to low damping ratio, flat permanent magnet linear synchronous motor's vibration is difficult to be damped and the accuracy is limited. The vibration suppressing results are not good enough in the existing research because only the longitudinal direction vibration is considered while the normal direction vibration is neglected. The parameters of the direct-axis current controller are set to be the same as those of the quadrature-axis current controller commonly. This causes contradiction between signal noise and response. To suppress the vibration, the electromagnetic force model of the flat permanent magnet synchronous linear motor is formulated first. Through the analysis of the effect that direct-axis current noise and quadrature-axis current noise have on both direction vibration, it can be declared that the conclusion that longitudinal direction vibration is only related to the quadrature-axis current noise while the normal direction vibration is related to both the quadrature-axis current noise and direct-axis current noise. Then, the simulation test on current loop with a low-pass filter is conducted and the results show that the low-pass filter can not suppress the vibration but makes the vibration more severe. So a vibration suppressing strategy that the proportional gain of direct-axis current controller adapted according to quadrature-axis reference current is proposed. This control strategy can suppress motor vibration by suppressing direct-axis current noise. The experiments results about the effect of K p and T i on normal direction vibration, longitudinal vibration and the position step response show that this strategy suppresses vibration effectively while the motor's motion performance is not affected. The maximum reduction of vibration can be up to 40%. In addition, current test under rated load condition is also conducted and the results show that the control strategy can avoid the conflict between the direct-axis current and the quadrature

  4. Vibration Control via Stiffness Switching of Magnetostrictive Transducers (United States)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.


    In this paper, a computational study is presented of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.

  5. 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:,; Moreira, R.G. [Petroleo Brasileiro S.A. - PETROBRAS, Cabiunas, RJ (Brazil)], E-mail:


    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

  6. Electromyographic assessment of muscle fatigue during isometric vibration training at varying frequencies. (United States)

    Mischi, M; Rabotti, C; Cardinale, M


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

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

    Directory of Open Access Journals (Sweden)

    Mihai Valentin Predoi


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

  8. Numerical Analysis of the Influence of Low Frequency Vibration on Bubble Growth. (United States)

    Han, D; Kedzierski, Mark A


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

  9. Whole-body vibration therapy in intensive care patients: A feasibility and safety study. (United States)

    Boeselt, Tobias; Nell, Christoph; Kehr, Katahrina; Holland, Angélique; Dresel, Marc; Greulich, Timm; Tackenberg, Björn; Kenn, Klaus; Boeder, Johannes; Klapdor, Benjamin; Kirschbaum, Andreas; Vogelmeier, Claus; Alter, Peter; Koczulla, Andreas Rembert


    Admission to the intensive care unit is associated with sustained loss of muscle mass, reduced quality of life and increased mortality. Early rehabilitation measures may counteract this process. New approaches to rehabilitation while the patient remains in bed are whole-body vibration alone and whole-body vibration with a dumbbell. The aims of this study are to determine the safety of whole-body vibration for patients admitted to the intensive care unit, and to compare the effects of these techniques in intensive care unit patients and healthy subjects. Twelve intensive care unit patients and 12 healthy subjects using whole-body vibration for the first time were examined while lying in bed. First both groups performed whole body vibration over 3 min. In a second step whole body vibration with dumbbell was performed. In order to determine the safety of the training intensity, heart rate, oxygen saturation and blood pressure were measured. The study was approved by the Marburg ethics committee. There were minor reversible and transient increases in diastolic blood pressure (p = 0.005) and heart rate (p = 0.001) in the control group with whole-body vibration with a dumbbell. In intensive care patients receiving whole-body vibration alone, there were increases in diastolic blood pressure (p = 0.011) and heart rate (p vibration and whole-body vibration with a dumbbell for intensive care unit in-bed patients. No clinically significant safety problems were found. Whole-body vibration and whole-body vibration with a dumbbell might therefore be alternative methods for use in early in-bed rehabilitation, not only for hospitalized patients.

  10. Development and evaluation of a generic active helicopter vibration controller (United States)

    Davis, M. W.


    A computerized generic active controller is developed, which alleviates helicopter vibration by closed-loop implementation of higher harmonic control (HHC). In the system, the higher harmonic blade pitch is input through a standard helicopter swashplate; for a four-blade helicopter rotor the 4/rev vibration in the rotorcraft is minimized by inducing cyclic pitch motions at 3, 4, and 5/rev in the rotating system. The controller employs the deterministic, cautious, and dual control approaches and two linear system models (local and global), as well as several methods of limiting control. Based on model testing, performed at moderate to high values of forward velocity and rotor thrust, reductions in the rotor test apparatus vibration from 75 to 95 percent are predicted, with HHC pitch amplitudes of less than one degree. Good performance is also noted for short-duration maneuvers.

  11. Modelling of magnetostriction of transformer magnetic core for vibration analysis

    Directory of Open Access Journals (Sweden)

    Marks Janis


    Full Text Available Magnetostriction is a phenomenon occurring in transformer core in normal operation mode. Yet in time, it can cause the delamination of magnetic core resulting in higher level of vibrations that are measured on the surface of transformer tank during diagnostic tests. The aim of this paper is to create a model for evaluating elastic deformations in magnetic core that can be used for power transformers with intensive vibrations in order to eliminate magnetostriction as a their cause. Description of the developed model in Matlab and COMSOL software is provided including restrictions concerning geometry and properties of materials, and the results of performed research on magnetic core anisotropy are provided. As a case study modelling of magnetostriction for 5-legged 200 MVA power transformer with the rated voltage of 13.8/137kV is conducted, based on which comparative analysis of vibration levels and elastic deformations is performed.

  12. Vibrational microspectroscopy analysis of human lenses (United States)

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


    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.

  13. A Vibrating Wire System For Quadrupole Fiducialization

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Zachary


    A vibrating wire system is being developed to fiducialize the quadrupoles between undulator segments in the LCLS. This note provides a detailed analysis of the system. The LCLS will have quadrupoles between the undulator segments to keep the electron beam focused. If the quadrupoles are not centered on the beam axis, the beam will receive transverse kicks, causing it to deviate from the undulator axis. Beam based alignment will be used to move the quadrupoles onto a straight line, but an initial, conventional alignment must place the quadrupole centers on a straight line to 100 {micro}m. In the fiducialization step of the initial alignment, the position of the center of the quadrupole is measured relative to tooling balls on the outside of the quadrupole. The alignment crews then use the tooling balls to place the magnet in the tunnel. The required error on the location of the quadrupole center relative to the tooling balls must be less than 25 {micro}m. In this note, we analyze a system under construction for the quadrupole fiducialization. The system uses the vibrating wire technique to position a wire onto the quadrupole magnetic axis. The wire position is then related to tooling balls using wire position detectors. The tooling balls on the wire position detectors are finally related to tooling balls on the quadrupole to perform the fiducialization. The total 25 {micro}m fiducialization error must be divided between these three steps. The wire must be positioned onto the quadrupole magnetic axis to within 10 {micro}m, the wire position must be measured relative to tooling balls on the wire position detectors to within 15 {micro}m, and tooling balls on the wire position detectors must be related to tooling balls on the quadrupole to within 10 {micro}m. The techniques used in these three steps will be discussed. The note begins by discussing various quadrupole fiducialization techniques used in the past and discusses why the vibrating wire technique is our method

  14. Vibration Signal Forecasting on Rotating Machinery by means of Signal Decomposition and Neurofuzzy Modeling

    Directory of Open Access Journals (Sweden)

    Daniel Zurita-Millán


    Full Text Available Vibration monitoring plays a key role in the industrial machinery reliability since it allows enhancing the performance of the machinery under supervision through the detection of failure modes. Thus, vibration monitoring schemes that give information regarding future condition, that is, prognosis approaches, are of growing interest for the scientific and industrial communities. This work proposes a vibration signal prognosis methodology, applied to a rotating electromechanical system and its associated kinematic chain. The method combines the adaptability of neurofuzzy modeling with a signal decomposition strategy to model the patterns of the vibrations signal under different fault scenarios. The model tuning is performed by means of Genetic Algorithms along with a correlation based interval selection procedure. The performance and effectiveness of the proposed method are validated experimentally with an electromechanical test bench containing a kinematic chain. The results of the study indicate the suitability of the method for vibration forecasting in complex electromechanical systems and their associated kinematic chains.


    Directory of Open Access Journals (Sweden)

    Gaidaichuk V.V.


    Full Text Available On the basis of the non-holonomic mechanics methods, the problem of the whirling vibrations of a bit of a drillstring, which is prestressed by longitudinal force and rotates under the applied forces is stated. The analysis of the mechanism of the vibration self-excitation is performed. It is shown that they can be both stable and unstable.

  16. Vibration Control of Structures using Vibro-Impact Nonlinear Energy Sinks

    Directory of Open Access Journals (Sweden)

    M. Ahmadi


    Full Text Available Using Vibro-Impact Nonlinear Energy Sinks (VI NESs is one of the novel strategies to control structural vibrations and mitigate their seismic response. In this system, a mass is tuned on the structure floor, so that it has a specific distance from an inelastic constraint connected to the floor mass. In case of structure stimulation, the displaced VI NES mass collides with the  inelastic constraint and upon impacts, energy is dissipated. In the present work, VI NES is studied when its parameters, including clearance and stiffness ratio, are simultaneously optimized. Harmony search as a recent meta-heuristic algorithm is efficiently specialized and utilized for the aforementioned continuous optimization problem. The optimized attached VI NES is thus shown to be capable of interacting with the primary structure over a wide range of frequencies. The resulting controlled response is then investigated, in a variety of low and medium rise steel moment frames, via nonlinear dynamic time history analyses. Capability of the VI NES to dissipate siesmic input energy of earthquakes and their capabilitiy in reducing response of srtructures effectively, through vibro-impacts between the energy sink’s mass and the floor mass, is discussed by extracting several performance indices and the corresponding Fourier spectra. Results of the numerical simulations done on some structural model examples reveal that the optimized VI NES has caused successive redistribution of energy from low-frequency high-amplitude vibration modes to high-frequency low-amplitude modes, bringing about the desired attenuation of the structural responses.

  17. Adaptive control of an active seat for occupant vibration reduction (United States)

    Gan, Zengkang; Hillis, Andrew J.; Darling, Jocelyn


    The harmful effects on human performance and health caused by unwanted vibration from vehicle seats are of increasing concern. This paper presents an active seat system to reduce the vibration level transmitted to the seat pan and the occupants' body under low frequency periodic excitation. Firstly, the detail of the mechanical structure is given and the active seat dynamics without external load are characterized by vibration transmissibility and frequency responses under different excitation forces. Owing the nonlinear and time-varying behaviour of the proposed system, a Filtered-x least-mean-square (FXLMS) adaptive control algorithm with on-line Fast-block LMS (FBLMS) identification process is employed to manage the system operation for high vibration cancellation performance. The effectiveness of the active seat system is assessed through real-time experimental tests using different excitation profiles. The system identification results show that an accurate estimation of the secondary path is achieved by using the FBLMS on-line technique. Substantial reduction is found for cancelling periodic vibration containing single and multiple frequencies. Additionally, the robustness and stability of the control system are validated through transient switching frequency tests.


    Energy Technology Data Exchange (ETDEWEB)

    Joel Walls; M.T. Taner; Gary Mavko; Jack Dvorkin


    Wave-induced variations of pore pressure in a partially-saturated reservoir result in oscillatory liquid flow. The viscous losses during this flow are responsible for wave attenuation. The same viscous effects determine the changes in the dynamic bulk modulus of the system versus frequency. These changes are necessarily linked to attenuation via the causality condition. We analytically quantify the frequency dependence of the bulk modulus of a partially saturated rock by assuming that saturation is patchy and then link these changes to the inverse quality factor. As a result, the P-wave attenuation is quantitatively linked to saturation and thus can serve as a saturation indicator.

  19. Nutrient-rich dairy proteins improve appendicular skeletal muscle mass and physical performance, and attenuate the loss of muscle strength in older men and women subjects: a single-blind randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Alemán-Mateo H


    Full Text Available Heliodoro Alemán-Mateo,1 Virginia Ramírez Carreón,1 Liliana Macías,1 Humberto Astiazaran-García,1 Ana Cristina Gallegos-Aguilar,1 José Rogelio Ramos Enríquez2 1Coordinación de Nutrición, Centro de Investigación en Alimentación y Desarrollo, A.C., 2Laboratorio de Análisis Clínicos e Investigación, Departamento de Ciencias Químico Biológicas, Universidad de Sonora, Hermosillo, Mexico Background: At present, it is unknown whether the use of nutrient-rich dairy proteins improves the markers of sarcopenia syndrome. Therefore, our proposal was to investigate whether ­adding 210 g of ricotta cheese daily would improve skeletal muscle mass, handgrip strength, and ­physical performance in non-sarcopenic older subjects.Subjects and methods: This was a single-blind randomized clinical trial that included two homogeneous, randomized groups of men and women over 60 years of age. Participants in the intervention group were asked to consume their habitual diet but add 210 g of ricotta cheese (IG/HD + RCH, while the control group was instructed to consume only their habitual diet (CG/HD. Basal and 12-week follow-up measurements included appendicular skeletal muscle mass (ASMM by dual-energy X-ray absorptiometry, handgrip strength by a handheld dynamometer, and physical performance using the short physical performance battery (SPPB and the stair-climb power test (SCPT. The main outcomes were relative changes in ASMM, strength, SPPB, and SCPT.Results: ASMM increased in the IG/HD + RCH (0.6±3.5 kg, but decreased in the CG/HD (–1.0±2.6. The relative change between groups was statistically significant (P=0.009. The relative change in strength in both groups was negative, but the loss of muscle strength was more pronounced in CG/HD, though in this regard statistical analysis found only a tendency (P=0.07. The relative change in the balance-test scores was positive for the IG/HD + RCH, while in the CG/HD it was negative, as those individuals had

  20. Examples of law of seismic wave attenuation

    Directory of Open Access Journals (Sweden)

    Z. Kaláb


    Full Text Available The article summarizes experimental seismological measurements of vibration effects of blasting operations. During tunnel excavation can watch a variety of effects on the near or distant surroundings of the building. One of the most discussed are the effects of vibration, while the most important vibrations are caused when part of the excavation technology also use blasting. In this paper, we focus on the design summary of results from experimental seismological measurements, and the values of the maximum amplitude of vibration, which are measured at small distances from the source of vibration. For comparison also gives the results of experimental measurements of vibration induced at larger distances, or quarries.

  1. Ultrasonic metal welding with a vibration source using longitudinal and torsional vibration transducers (United States)

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


    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.

  2. Force illusions and drifts observed during muscle vibration. (United States)

    Reschechtko, Sasha; Cuadra, Cristian; Latash, Mark L


    We explored predictions of a scheme that views position and force perception as a result of measuring proprioceptive signals within a reference frame set by ongoing efferent process. In particular, this hypothesis predicts force illusions caused by muscle vibration and mediated via changes in both afferent and efferent components of kinesthesia. Healthy subjects performed accurate steady force production tasks by pressing with the four fingers of one hand (the task hand) on individual force sensors with and without visual feedback. At various times during the trials, subjects matched the perceived force using the other hand. High-frequency vibration was applied to one or both of the forearms (over the hand and finger extensors). Without visual feedback, subjects showed a drop in the task hand force, which was significantly smaller under the vibration of that forearm. Force production by the matching hand was consistently higher than that of the task hand. Vibrating one of the forearms affected the matching hand in a manner consistent with the perception of higher magnitude of force produced by the vibrated hand. The findings were consistent between the dominant and nondominant hands. The effects of vibration on both force drift and force mismatching suggest that vibration led to shifts in both signals from proprioceptors and the efferent component of perception, the referent coordinate and/or coactivation command. The observations fit the hypothesis on combined perception of kinematic-kinetic variables with little specificity of different groups of peripheral receptors that all contribute to perception of forces and coordinates. NEW & NOTEWORTHY We show that vibration of hand/finger extensors produces consistent errors in finger force perception. Without visual feedback, finger force drifted to lower values without a drift in the matching force produced by the other hand; hand extensor vibration led to smaller finger force drift. The findings fit the scheme with

  3. Entropy for Mechanically Vibrating Systems (United States)

    Tufano, Dante

    The research contained within this thesis deals with the subject of entropy as defined for and applied to mechanically vibrating systems. This work begins with an overview of entropy as it is understood in the fields of classical thermodynamics, information theory, statistical mechanics, and statistical vibroacoustics. Khinchin's definition of entropy, which is the primary definition used for the work contained in this thesis, is introduced in the context of vibroacoustic systems. The main goal of this research is to to establish a mathematical framework for the application of Khinchin's entropy in the field of statistical vibroacoustics by examining the entropy context of mechanically vibrating systems. The introduction of this thesis provides an overview of statistical energy analysis (SEA), a modeling approach to vibroacoustics that motivates this work on entropy. The objective of this thesis is given, and followed by a discussion of the intellectual merit of this work as well as a literature review of relevant material. Following the introduction, an entropy analysis of systems of coupled oscillators is performed utilizing Khinchin's definition of entropy. This analysis develops upon the mathematical theory relating to mixing entropy, which is generated by the coupling of vibroacoustic systems. The mixing entropy is shown to provide insight into the qualitative behavior of such systems. Additionally, it is shown that the entropy inequality property of Khinchin's entropy can be reduced to an equality using the mixing entropy concept. This equality can be interpreted as a facet of the second law of thermodynamics for vibroacoustic systems. Following this analysis, an investigation of continuous systems is performed using Khinchin's entropy. It is shown that entropy analyses using Khinchin's entropy are valid for continuous systems that can be decomposed into a finite number of modes. The results are shown to be analogous to those obtained for simple oscillators

  4. Characterizing X-ray Attenuation of Containerized Cargo

    Energy Technology Data Exchange (ETDEWEB)

    Birrer, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Divin, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Glenn, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Martz, H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wang, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)


    X-ray inspection systems can be used to detect radiological and nuclear threats in imported cargo. In order to better understand performance of these systems, the attenuation characteristics of imported cargo need to be determined. This project focused on developing image processing algorithms for segmenting cargo and using x-ray attenuation to quantify equivalent steel thickness to determine cargo density. These algorithms were applied to over 450 cargo radiographs. The results are summarized in this report.

  5. Tricolor attenuation model for shadow detection. (United States)

    Tian, Jiandong; Sun, Jing; Tang, Yandong


    Shadows, the common phenomena in most outdoor scenes, bring many problems in image processing and computer vision. In this paper, we present a novel method focusing on extracting shadows from a single outdoor image. The proposed tricolor attenuation model (TAM) that describe the attenuation relationship between shadow and its nonshadow background is derived based on image formation theory. The parameters of the TAM are fixed by using the spectral power distribution (SPD) of daylight and skylight, which are estimated according to Planck's blackbody irradiance law. Based on the TAM, a multistep shadow detection algorithm is proposed to extract shadows. Compared with previous methods, the algorithm can be applied to process single images gotten in real complex scenes without prior knowledge. The experimental results validate the performance of the model.

  6. Mechanical Vibrations Modeling and Measurement

    CERN Document Server

    Schmitz, Tony L


    Mechanical Vibrations:Modeling and Measurement describes essential concepts in vibration analysis of mechanical systems. It incorporates the required mathematics, experimental techniques, fundamentals of modal analysis, and beam theory into a unified framework that is written to be accessible to undergraduate students,researchers, and practicing engineers. To unify the various concepts, a single experimental platform is used throughout the text to provide experimental data and evaluation. Engineering drawings for the platform are included in an appendix. Additionally, MATLAB programming solutions are integrated into the content throughout the text. This book also: Discusses model development using frequency response function measurements Presents a clear connection between continuous beam models and finite degree of freedom models Includes MATLAB code to support numerical examples that are integrated into the text narrative Uses mathematics to support vibrations theory and emphasizes the practical significanc...

  7. Vibration Isolation Technology (VIT) ATD Project (United States)

    Lubomski, Joseph F.; Grodsinsky, Carlos M.; Logsdon, Kirk A.; Rohn, Douglas A.; Ramachandran, N.


    A fundamental advantage for performing material processing and fluid physics experiments in an orbital environment is the reduction in gravity driven phenomena. However, experience with manned spacecraft such as the Space Transportation System (STS) has demonstrated a dynamic acceleration environment far from being characterized as a 'microgravity' platform. Vibrations and transient disturbances from crew motions, thruster firings, rotating machinery etc. can have detrimental effects on many proposed microgravity science experiments. These same disturbances are also to be expected on the future space station. The Microgravity Science and Applications Division (MSAD) of the Office of Life and Microgravity Sciences and Applications (OLMSA), NASA Headquarters recognized the need for addressing this fundamental issue. As a result an Advanced Technology Development (ATD) project was initiated in the area of Vibration Isolation Technology (VIT) to develop methodologies for meeting future microgravity science needs. The objective of the Vibration Isolation Technology ATD project was to provide technology for the isolation of microgravity science experiments by developing methods to maintain a predictable, well defined, well characterized, and reproducible low-gravity environment, consistent with the needs of the microgravity science community. Included implicitly in this objective was the goal of advising the science community and hardware developers of the fundamental need to address the importance of maintaining, and how to maintain, a microgravity environment. This document will summarize the accomplishments of the VIT ATD which is now completed. There were three specific thrusts involved in the ATD effort. An analytical effort was performed at the Marshall Space Flight Center to define the sensitivity of selected experiments to residual and dynamic accelerations. This effort was redirected about half way through the ATD focusing specifically on the sensitivity of

  8. Development of a semi-active dynamic vibration absorber for longitudinal vibration of propulsion shaft system based on magnetorheological elastomer (United States)

    Liu, Gaoyu; Lu, Kun; Zou, Donglin; Xie, Zhongliang; Rao, Zhushi; Ta, Na


    The control of the longitudinal pulsating force and the vibration generated is very important to improve the stealth performance of a submarine. Magnetorheological elastomer (MRE) is a kind of intelligent composite material, whose mechanical properties can be continuously, rapidly and reversibly controlled by an external magnetic field. It can be used as variable-stiffness components in the design of a semi-active dynamic vibration absorber (SDVA), which is one of the effective means of longitudinal vibration control. In this paper, an SDVA is designed based on the MRE’s magnetic-induced variable stiffness characteristic. Firstly, a mechanical model of the propulsion shaft system with the SDVA is proposed, theoretically discussed and numerically validated. Then, the mechanical performance of the MRE under different magnetic fields is tested. In addition, the magnetic circuit and the overall structure of the SDVA are designed. Furthermore, electromagnetic and thermodynamic simulations are carried out to guarantee the structural design. The frequency shift property of the SDVA is found through dynamic simulations and validated by a frequency shift experiment. Lastly, the vibration absorption capacity of the SDVA is investigated. The results show that the magnetorheological effect of the MRE and the frequency shift of the SDVA are obvious; the SDVA has relatively acceptable vibration absorption capacity.


    Energy Technology Data Exchange (ETDEWEB)

    Martin E. Cobern


    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.


    Energy Technology Data Exchange (ETDEWEB)

    Martin E. Cobern


    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. The month of June, 2004 was primarily occupied with the writing of the Phase I Final Report, the sole deliverable of Phase I, which will be submitted in the next quarter. Redesign of the laboratory prototype and design of the downhole (Phase II) prototype was

  11. Integrated Microfluidic Variable Optical Attenuator (United States)


    indices , the optical output power is gradually attenuated. We obtain a maximum attenuation of 28 dB when the fluid refractive index changes from 1.557 to...Electron. 23, pp. 1348-1354 (2005). 14. J. M. Ruano, V. Benoit, J. S. Aitchison , and J. M. Cooper, “Flame hydrolysis deposition of glass on silicon for...different refractive indices flowing in a microfluidic channel as the cladding for a segment of straight optical waveguide. Recently, the integration of

  12. Electronic Properties of Si-Hx Vibrational Modes at Si Waveguide Interface. (United States)

    Bashouti, Muhammad Y; Yousefi, Peyman; Ristein, Jürgen; Christiansen, Silke H


    Attenuated total reflectance (ATR) and X-ray photoelectron spectroscopy in suite with Kelvin probe were conjugated to explore the electronic properties of Si-Hx vibrational modes by developing Si waveguide with large dynamic detection range compared with conventional IR. The Si 2p emission and work-function related to the formation and elimination of Si-Hx bonds at Si surfaces are monitored based on the detection of vibrational mode frequencies. A transition between various Si-Hx bonds and thus related vibrational modes is monitored for which effective momentum transfer could be demonstrated. The combination of the aforementioned methods provides for results that permit a model for the kinetics of hydrogen termination of Si surfaces with time and advanced surface characterizing of hybrid-terminated semiconducting solids.

  13. Understanding acoustics an experimentalist’s view of acoustics and vibration

    CERN Document Server

    Garrett, Steven L


    This textbook provides a unified approach to acoustics and vibration suitable for use in advanced undergraduate and first-year graduate courses on vibration and fluids. The book includes thorough treatment of vibration of harmonic oscillators, coupled oscillators, isotropic elasticity, and waves in solids including the use of resonance techniques for determination of elastic moduli. Drawing on 35 years of experience teaching introductory graduate acoustics at the Naval Postgraduate School and Penn State, the author presents a hydrodynamic approach to the acoustics of sound in fluids that provides a uniform methodology for analysis of lumped-element systems and wave propagation that can incorporate attenuation mechanisms and complex media. This view provides a consistent and reliable approach that can be extended with confidence to more complex fluids and future applications. Understanding Acoustics opens with a mathematical introduction that includes graphing and statistical uncertainty, followed by five chap...

  14. Stroboscopic shearography for vibration analysis (United States)

    Steinchen, Wolfgang; Kupfer, Gerhard; Maeckel, Peter; Voessing, Frank


    Digital Shearography, a laser interferometric technique in conjunction with the digital image processing, has the potential for vibration analysis due to its simple optical system and insensitivity against small rigid body motions. This paper will focus on its recent developments for vibration analysis and for nondestructive testing (NDT) by dynamic (harmonical) excitation. With the introduction of real time observation using automatically refreshing reference frame, both small and large rigid body motions are greatly suppressed. The development of a smaller and more mobile measuring device in conjunction with a user guided comfortable program Shearwin enables the digital shearography to be applied easily as an industrial online testing tool.

  15. Vibrational Collapse of Hexapod Packings (United States)

    Zhao, Yuchen; Ding, Jingqiu; Barés, Jonathan; Zheng, Hu; Dierichs, Karola; Menges, Achim; Behringer, Robert


    Columns made of convex noncohesive grains like sand collapse after being released from a confining container. However, structures built from non-convex grains can be stable without external support. In the current experiments, we investigate the effect of vibration on destroying such columns. The change of column height during vertical vibration, can be well characterized by stretched exponential relaxation when the column is short, which is in agreement with previous work, while a faster collapse happens when the column is tall. We investigate the collapse after the fast process including its dependence on column geometry, and on interparticle and basal friction.

  16. Innovative Techniques Simplify Vibration Analysis (United States)


    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."

  17. Diffusion mobility of the hydrogen atom with allowance for the anharmonic attenuation of migrating atom state

    Energy Technology Data Exchange (ETDEWEB)

    Kashlev, Y.A., E-mail:


    Evolution of vibration relaxation of hydrogen atoms in metals with the close-packed lattice at high and medium temperatures is investigated based on non-equilibrium statistical thermodynamics, in that number on using the retarded two-time Green function method. In accordance with main kinetic equation – the generalized Fokker- Plank- Kolmogorov equation, anharmonism of hydrogen atoms vibration in potential wells does not make any contribution to collision effects. It influences the relaxation processes at the expense of interference of fourth order anharmonism with single-phonon scattering on impurity hydrogen atoms. Therefore, the total relaxation time of vibration energy of system metal-hydrogen is written as a product of two factors: relaxation time of system in harmonic approximation and dimensionless anharmonic attenuation of quantum hydrogen state.

  18. Characterization of real-world vibration sources with a view toward optimal energy harvesting architectures (United States)

    Rantz, Robert; Roundy, Shad


    A tremendous amount of research has been performed on the design and analysis of vibration energy harvester architectures with the goal of optimizing power output; most studies assume idealized input vibrations without paying much attention to whether such idealizations are broadly representative of real sources. These "idealized input signals" are typically derived from the expected nature of the vibrations produced from a given source. Little work has been done on corroborating these expectations by virtue of compiling a comprehensive list of vibration signals organized by detailed classifications. Vibration data representing 333 signals were collected from the NiPS Laboratory "Real Vibration" database, processed, and categorized according to the source of the signal (e.g. animal, machine, etc.), the number of dominant frequencies, the nature of the dominant frequencies (e.g. stationary, band-limited noise, etc.), and other metrics. By categorizing signals in this way, the set of idealized vibration inputs commonly assumed for harvester input can be corroborated and refined, and heretofore overlooked vibration input types have motivation for investigation. An initial qualitative analysis of vibration signals has been undertaken with the goal of determining how often a standard linear oscillator based harvester is likely the optimal architecture, and how often a nonlinear harvester with a cubic stiffness function might provide improvement. Although preliminary, the analysis indicates that in at least 23% of cases, a linear harvester is likely optimal and in no more than 53% of cases would a nonlinear cubic stiffness based harvester provide improvement.

  19. Experimental Study on Interfacial Area Transport of Two-Phase Flow under Vibration Conditions

    Directory of Open Access Journals (Sweden)

    Xiu Xiao


    Full Text Available An experimental study on air-water two-phase flow under vibration condition has been conducted using double-sensor conductivity probe. The test section is an annular geometry with hydraulic diameter of 19.1 mm. The vibration frequency ranges from 0.47 Hz to 2.47 Hz. Local measurements of void fraction, interfacial area concentration (IAC, and Sauter mean diameter have been performed along one radius in the vibration direction. The result shows that local parameters fluctuate continuously around the base values in the vibration cycle. Additional bubble force due to inertia is used to explain lateral bubble motions. The fluctuation amplitudes of local void fraction and IAC increase significantly with vibration frequency. The radial distribution of local parameters at the maximum vibration displacement is specifically analyzed. In the void fraction and IAC profiles, the peak near the inner wall is weakened or even disappearing and a strong peak skewed to outer wall is gradually observed with the increase of vibration frequency. The nondimensional peak void fraction can reach a maximum of 49% and the mean relative variation of local void fraction can increase to more than 29% as the vibration frequency increases to 2.47 Hz. But the increase of vibration frequency does not bring significant change to bubble diameter.

  20. Effect of Bio Ethanol and Diesel Blend on Small Diesel Engine Vibration

    Directory of Open Access Journals (Sweden)

    S.H Hashemi Fard


    Full Text Available The use of Bio-ethanol as an alternative diesel engine fuel is rapidly increasing. Bio-ethanol is mixed with diesel fuel at different ratios and used in CI and SI engines. Since vibrations have direct effects on users and engine components, for this reason analysis of vibration resulting from combustion in CI engines is very important. In this study, evaluation of vibration was performed for both diesel and ethanol blends. Commercial diesel fuel (D100, E2 (2% ethanol and 98% diesel fuel, E5, E10, E15 and E20 were used in a two-wheel MITSUBISHI tractor. The engine was tested in 1200, 1600, 2000 and 2400 rpm for all fuel blends, and also the effect of load was investigated for D100 and E10. Results showed that vibration is significantly affected by fuel blend. It was observed that E10 had the lowest vibration while E20 had the highest value. It was also observed that vibration increased as engine speed increased for all fuel blends. It was found that both axial and lateral vibrations affected significantly by load. The lateral vibrations decreased continuously with load rise , but the axial vibrations increased initially but started to follow a reverse trend.

  1. The Effects of Local Vibration on Balance, Power, and Self-Reported Pain After Exercise. (United States)

    Custer, Lisa; Peer, Kimberly S; Miller, Lauren


    Muscle fatigue and acute muscle soreness occur after exercise. Application of a local vibration intervention may reduce the consequences of fatigue and soreness. To examine the effects of a local vibration intervention after a bout of exercise on balance, power, and self-reported pain. Single-blind crossover study. Laboratory. 19 healthy, moderately active subjects. After a 30-min bout of full-body exercise, subjects received either an active or a sham vibration intervention. The active vibration intervention was performed bilaterally over the muscle bellies of the triceps surae, quadriceps, hamstrings, and gluteals. At least 1 wk later, subjects repeated the bout, receiving the other vibration intervention. Static balance, dynamic balance, power, and self-reported pain were measured at baseline, after the vibration intervention, and 24 h postexercise. After the bout of exercise, subjects had reduced static and dynamic balance and increased self-reported pain regardless of vibration intervention. There were no differences between outcome measures between the active and sham vibration conditions. The local vibration intervention did not affect balance, power, or self-reported pain.

  2. Descriptive analysis of combine cabin vibrations and their effect on the human body (United States)

    Hostens, I.; Ramon, H.


    All on- and off-road vehicles are exposed to vibrations caused by unevenness of road or soil profile, moving elements within the machine or implements. A higher prevalence of low back pain is found in drivers of off-road machinery than in other drivers. In this study, significantly higher levels of low-frequency vibrations are found in the cabin of a combine, driving at high speed (20 km/h) on a concrete surface, compared to driving slower on field road. Comfort values indicate that injury can result from long-term driving on the field as well as on a concrete road. As seats with suspension systems are the main transmission paths of vibration towards the spine of the driver, their vibration attenuating characteristics play an important role in comfort assessment. The resonant frequency of seats with passive suspension system, used in agricultural machinery, lies in the low-frequency range most excited in agricultural machinery. A seat with air suspension is found to attenuate better frequencies above 4 Hz and provide more comfort to the driver than a seat with a mechanical suspension.

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

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.


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

  4. A self-adaptive anti-vibration pipeline-filtering algorithm (United States)

    Wu, Houde; Wang, Bin; Zhao, Ming; Xu, Wenhai


    The mobile pipeline-filtering algorithm is a real-time algorithm that performs well in detecting small dim targets, but it is particularly sensitive to interframe vibration of sequence images. When searching for small dim targets at sea based on an infrared imaging system, irregular and random vibration of the airborne imaging platform causes huge interference problems for the mobile pipeline-filtering. This paper puts forward a pipeline-filtering algorithm that has a good performance on self-adaptive anti-vibration. In the block matching method using the normalized cross-correlations coefficient (NCC), the interframe vibration of sequence images is acquired in real time and used to correct coordinates of the single-frame detection results, and then the corrected detection results are used to complete the mobile pipelinefiltering. Experimental results show that the algorithm can overcome the problem of interframe vibration of sequence images, thus realizing accurate detection of small dim maritime targets.

  5. Resonant vibration control of rotating beams

    DEFF Research Database (Denmark)

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


    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....

  6. Isogeometric Shape Optimization of Vibrating Membranes

    DEFF Research Database (Denmark)

    Nguyen, Dang Manh; Evgrafov, Anton; Gersborg, Allan Roulund


    We consider a model problem of isogeometric shape optimization of vibrating membranes whose shapes are allowed to vary freely. The main obstacle we face is the need for robust and inexpensive extension of a B-spline parametrization from the boundary of a domain onto its interior, a task which has...... perform a number of numerical experiments with our isogeometric shape optimization algorithm and present smooth, optimized membrane shapes. Our conclusion is that isogeometric analysis fits well with shape optimization.......We consider a model problem of isogeometric shape optimization of vibrating membranes whose shapes are allowed to vary freely. The main obstacle we face is the need for robust and inexpensive extension of a B-spline parametrization from the boundary of a domain onto its interior, a task which has...... to be performed in every optimization iteration. We experiment with two numerical methods (one is based on the idea of constructing a quasi-conformal mapping, whereas the other is based on a spring-based mesh model) for carrying out this task, which turn out to work sufficiently well in the present situation. We...

  7. Practical design of a nonlinear tuned vibration absorber

    DEFF Research Database (Denmark)

    Grappasonni, C.; Habib, G.; Detroux, T.


    The aim of the paper is to develop a new nonlinear tuned vibration absorber (NLTVA) capable of mitigating the vibrations of nonlinear systems which are known to exhibit frequency-energy-dependent oscillations. A nonlinear generalization of Den Hartog's equal-peak method is proposed to ensure equal...... peaks in the nonlinear frequency response for a large range of forcing amplitudes. An analytical tuning procedure is developed and provides the load-deflection characteristic of the NLTVA. Based on this prescribed relation, the NLTVA design is performed by two different approaches, namely thanks to (i...

  8. Reducing friction-induced vibration using intelligent active force ...

    Indian Academy of Sciences (India)

    (FIV). Thus, it should be reduced or controlled as much as possible in order to achieve quieter vehicle (brake system), better performance (position control systems and clutches) and quality products. There were typically three major mechanisms that contributing to the generation of friction induced vibration namely: negative ...

  9. Construction Vibration Impacts on the Center for Integrated Nanotechnologies.

    Energy Technology Data Exchange (ETDEWEB)

    Hearne, Sean J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kostranchuk, Theodore [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jungjohann, Katherine Leigh [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bussmann, Ezra [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Swartzentruber, Brian [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Weiss, Karl [Arizona State Univ., Mesa, AZ (United States); Wowk, Victor [Machine Dynamics, Inc., Sale Creek, TN (United States)


    Under the direction of the James W. Todd, Assistant Manager for Engineering within the National Nuclear Security Administration Sandia Field Office, the team listed above has performed the attached study to evaluate the vibration sensitivity of the Center for Integrated Nanotechnolog ies and propose possible mitigation strategies .

  10. Analysis of a Lorentz force based vibration exciter using permanent ...

    Indian Academy of Sciences (India)

    This work presents performance analysis of a Lorentz force based noncontact vibration exciter by mounting a couple of permanent magnets on a piezoelectric stack. A conductor is attached to the structure to be excited and is placed midway between unlike poles of a couple of permanent magnets. The permanent magnets ...

  11. Effect of vibration frequency on biopsy needle insertion force. (United States)

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


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

  12. Combined Euler column vibration isolation and energy harvesting (United States)

    Davis, R. B.; McDowell, M. D.


    A new device that combines vibration isolation and energy harvesting is modeled, simulated, and tested. The vibration isolating portion of the device uses post-buckled beams as its spring elements. Piezoelectric film is applied to the beams to harvest energy from their dynamic flexure. The entire device operates passively on applied base excitation and requires no external power or control system. The structural system is modeled using the elastica, and the structural response is applied as forcing on the electric circuit equation to predict the output voltage and the corresponding harvested power. The vibration isolation and energy harvesting performance is simulated across a large parameter space and the modeling approach is validated with experimental results. Experimental transmissibilities of 2% and harvested power levels of 0.36 μW are simultaneously demonstrated. Both theoretical and experimental data suggest that there is not necessarily a trade-off between vibration isolation and harvested power. That is, within the practical operational range of the device, improved vibration isolation will be accompanied by an increase in the harvested power as the forcing frequency is increased.

  13. Acute and chronic neuromuscular adaptations to local vibration training. (United States)

    Souron, Robin; Besson, Thibault; Millet, Guillaume Y; Lapole, Thomas


    Vibratory stimuli are thought to have the potential to promote neural and/or muscular (re)conditioning. This has been well described for whole-body vibration (WBV), which is commonly used as a training method to improve strength and/or functional abilities. Yet, this technique may present some limitations, especially in clinical settings where patients are unable to maintain an active position during the vibration exposure. Thus, a local vibration (LV) technique, which consists of applying portable vibrators directly over the tendon or muscle belly without active contribution from the participant, may present an alternative to WBV. The purpose of this narrative review is (1) to provide a comprehensive overview of the literature related to the acute and chronic neuromuscular changes associated with LV, and (2) to show that LV training may be an innovative and efficient alternative method to the 'classic' training programs, including in the context of muscle deconditioning prevention or rehabilitation. An acute LV application (one bout of 20-60 min) may be considered as a significant neuromuscular workload, as demonstrated by an impairment of force generating capacity and LV-induced neural changes. Accordingly, it has been reported that a training period of LV is efficient in improving muscular performance over a wide range of training (duration, number of session) and vibration (frequency, amplitude, site of application) parameters. The functional improvements are principally triggered by adaptations within the central nervous system. A model illustrating the current research on LV-induced adaptations is provided.


    Directory of Open Access Journals (Sweden)

    Ljubomir Vračar


    Full Text Available The purpose of the research presented in this paper is the development of the smart mobile phone application for vibration monitoring of pumping aggregate, based on Microchip’s microcontroller (MC. Hardware used is based on Bluetooth connection between smart sensor and smart mobile phone. Software for acquisition and data analysis is optimized for imbedded application in smart sensors. Smart acceleration sensor in conjunction with Bluetooth connection to smart mobile phone creates one touch mobile vibration monitoring system. The authors have performed numerous measurements on a wide range of aggregates for establishing the operating functionality of the newly created system. The possibility of system application I rail vehicle vibration monitoring is also analyzed.

  15. Planetary Gearbox Fault Detection Using Vibration Separation Techniques (United States)

    Lewicki, David G.; LaBerge, Kelsen E.; Ehinger, Ryan T.; Fetty, Jason


    Studies were performed to demonstrate the capability to detect planetary gear and bearing faults in helicopter main-rotor transmissions. The work supported the Operations Support and Sustainment (OSST) program with the U.S. Army Aviation Applied Technology Directorate (AATD) and Bell Helicopter Textron. Vibration data from the OH-58C planetary system were collected on a healthy transmission as well as with various seeded-fault components. Planetary fault detection algorithms were used with the collected data to evaluate fault detection effectiveness. Planet gear tooth cracks and spalls were detectable using the vibration separation techniques. Sun gear tooth cracks were not discernibly detectable from the vibration separation process. Sun gear tooth spall defects were detectable. Ring gear tooth cracks were only clearly detectable by accelerometers located near the crack location or directly across from the crack. Enveloping provided an effective method for planet bearing inner- and outer-race spalling fault detection.

  16. Low-energy isovector quadrupole vibrations

    Energy Technology Data Exchange (ETDEWEB)

    Faessler, A.; Nojarov, R.


    The low-lying isovector quadrupole vibrations are described by an extension of the vibrational model allowing independent proton and neutron vibrations coupled by the symmetry energy. The recently detected low-lying isovector states in nearly spherical nuclei with N=84 are described well concerning their energies and E2/M1 mixing ratios. (orig.).

  17. Ground Vibration Measurements at LHC Point 4

    Energy Technology Data Exchange (ETDEWEB)

    Bertsche, Kirk; /SLAC; Gaddi, Andrea; /CERN


    Ground vibration was measured at Large Hadron Collider (LHC) Point 4 during the winter shutdown in February 2012. This report contains the results, including power and coherence spectra. We plan to collect and analyze vibration data from representative collider halls to inform specifications for future linear colliders, such as ILC and CLIC. We are especially interested in vibration correlations between final focus lens locations.

  18. Rotor Vibration Reduction via Active Hybrid Bearings

    DEFF Research Database (Denmark)

    Nicoletti, Rodrigo; Santos, Ilmar


    The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... with experiment, and simulations show the feasibility of controlling shaft vibration through this active device....

  19. 33 CFR 159.103 - Vibration test. (United States)


    ... 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...

  20. 14 CFR 27.907 - Engine vibration. (United States)


    ... 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...

  1. 14 CFR 29.251 - Vibration. (United States)


    ... 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...

  2. 14 CFR 29.907 - Engine vibration. (United States)


    ... 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...

  3. 14 CFR 27.251 - Vibration. (United States)


    ... 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...

  4. 49 CFR 178.608 - Vibration standard. (United States)


    ... 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...

  5. 49 CFR 178.985 - Vibration test. (United States)


    ... 49 Transportation 2 2010-10-01 2010-10-01 false Vibration test. 178.985 Section 178.985... Testing of Large Packagings § 178.985 Vibration test. (a) General. All rigid Large Packaging and flexible Large Packaging design types must be capable of withstanding the vibration test. (b) Test method. (1) A...

  6. Vibration measurements on timber frame floors

    NARCIS (Netherlands)

    Kuilen, J.W.G. van de; Oosterhout, G.P.C. van; Donkervoort, R.


    In the design of lightweight floors vibrational aspects become more and more important. With the foreseen introduction of Eurocode 5 the vibration of timber floors becomes a part of the design for serviceability. Design rules for the vibrational behaviour are given in Eurocode 5. The first rule is

  7. Vibrations in a moving flexible robot arm (United States)

    Wang, P. K. C.; Wei, Jin-Duo


    The vibration in a flexible robot arm modeled by a moving slender prismatic beam is considered. It is found that the extending and contracting motions have destabilizing and stabilizing effects on the vibratory motions, respectively. The vibration analysis is based on a Galerkin approximation with time-dependent basis functions. Typical numerical results are presented to illustrate the qualitative features of vibrations.

  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 (United States)

    Hunt, Ronald Allen (Inventor)


    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. Wideband Piezomagnetoelastic Vibration Energy Harvesting

    DEFF Research Database (Denmark)

    Lei, Anders; Thomsen, Erik Vilain


    This work presents a small-scale wideband piezomagnetoelastic vibration energy harvester (VEH) aimed for operation at frequencies of a few hundred Hz. The VEH consists of a tape-casted PZT cantilever with thin sheets of iron foil attached on each side of the free tip. The wideband operation...

  11. Ultrafast vibrations of gold nanorings

    DEFF Research Database (Denmark)

    Kelf, T; Tanaka, Y; Matsuda, O


    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...

  12. Rotor position and vibration control for aerospace flywheel energy storage devices and other vibration based devices (United States)

    Alexander, B. X. S.

    Flywheel energy storage has distinct advantages over conventional energy storage methods such as electrochemical batteries. Because the energy density of a flywheel rotor increases quadratically with its speed, the foremost goal in flywheel design is to achieve sustainable high speeds of the rotor. Many issues exist with the flywheel rotor operation at high and varying speeds. A prominent problem is synchronous rotor vibration, which can drastically limit the sustainable rotor speed. In a set of projects, the novel Active Disturbance Rejection Control (ADRC) is applied to various problems of flywheel rotor operation. These applications include rotor levitation, steady state rotation at high speeds and accelerating operation. Several models such as the lumped mass model and distributed three-mass models have been analyzed. In each of these applications, the ADRC has been extended to cope with disturbance, noise, and control effort optimization; it also has been compared to various industry-standard controllers such as PID and PD/observer, and is proven to be superior. The control performance of the PID controller and the PD/observer currently used at NASA Glenn has been improved by as much as an order of magnitude. Due to the universality of the second order system, the results obtained in the rotor vibration problem can be straightforwardly extended to other vibrational systems, particularly, the MEMS gyroscope. Potential uses of a new nonlinear controller, which inherits the ease of use of the traditional PID, are also discussed.

  13. Effect of attenuation correction on image quality in emission tomography (United States)

    Denisova, N. V.; Ondar, M. M.


    In this paper, mathematical modeling and computer simulations of myocardial perfusion SPECT imaging are performed. The main factors affecting the quality of reconstructed images in SPECT are anatomical structures, the diastolic volume of a myocardium and attenuation of gamma rays. The purpose of the present work is to study the effect of attenuation correction on image quality in emission tomography. The basic 2D model describing a Tc-99m distribution in a transaxial slice of the thoracic part of a patient body was designed. This model was used to construct four phantoms simulated various anatomical shapes: 2 male and 2 female patients with normal, obese and subtle physique were included in the study. Data acquisition model which includes the effect of non-uniform attenuation, collimator-detector response and Poisson statistics was developed. The projection data were calculated for 60 views in accordance with the standard myocardial perfusion SPECT imaging protocol. Reconstructions of images were performed using the OSEM algorithm which is widely used in modern SPECT systems. Two types of patient's examination procedures were simulated: SPECT without attenuation correction and SPECT/CT with attenuation correction. The obtained results indicate a significant effect of the attenuation correction on the SPECT images quality.

  14. Two-dimensional dynamic fluid bowtie attenuators. (United States)

    Hermus, James R; Szczykutowicz, Timothy P


    Fluence field modulated (FFM) CT allows for improvements in image quality and dose reduction. To date, only one-dimensional modulators have been proposed, as the extension to two-dimensional (2-D) modulation is difficult with solid-metal attenuation-based fluence field modulated designs. This work proposes to use liquid and gas to attenuate the x-ray beam, as unlike solids, these materials can be arranged allowing for 2-D fluence modulation. The thickness of liquid and the pressure for a given path length of gas were determined that provided the same attenuation as 30 cm of soft tissue at 80, 100, 120, and 140 kV. Liquid iodine, zinc chloride, cerium chloride, erbium oxide, iron oxide, and gadolinium chloride were studied. Gaseous xenon, uranium hexafluoride, tungsten hexafluoride, and nickel tetracarbonyl were also studied. Additionally, we performed a proof-of-concept experiment using a 96 cell array in which the liquid thickness in each cell was adjusted manually. Liquid thickness varied as a function of kV and chemical composition, with erbium oxide allowing for the smallest thickness. For the gases, tungsten hexaflouride required the smallest pressure to compensate for 30 cm of soft tissue. The 96 cell iodine attenuator allowed for a reduction in both dynamic range to the detector and scatter-to-primary ratio. For both liquids and gases, when k-edges were located within the diagnostic energy range used for imaging, the mean beam energy exhibited the smallest change with compensation amount. The thickness of liquids and the gas pressure seem logistically implementable within the space constraints of C-arm-based cone beam CT (CBCT) and diagnostic CT systems. The gas pressures also seem logistically implementable within the space and tube loading constraints of CBCT and diagnostic CT systems.

  15. Effect of vibration on muscle strength imbalance in lower extremity using multi-control whole body vibration platform. (United States)

    Yu, Chang Ho; Seo, Shin Bae; Kang, Seung Rok; Kim, Kyung; Kwon, Tae Kyu


    This study shows the improvement of muscle activity and muscle strength imbalance in the lower extremities through independent exercise loads in vibration platform. Twenty females of age 20 participated in this study. The subjects were divided into WBV group, with more than 10% of muscle strength imbalance between left and right the lower extremities, and control group, with less than 10% of muscle strength imbalance between left and right the lower extremities. As the prior experiment showed, different exercise postures provide different muscular activities. As a result, the highest muscular activity was found to be in the low squat posture. Therefore, the LS posture was selected for the exercise in this experiment. Vibration intensities were applied to dominant muscle and non-dominant muscle, and the vibration frequency was fixed at 25Hz for the WBV group. The control group was asked to perform the same exercise as the WBV group, without stimulated vibration. This exercise was conducted for a total of 4 weeks. As a result, the WBV group which showed an average deviation of 16% before the experiment, tended to decrease approximately to 5%. In this study, vibration exercise using load deviation is shown to be effective in improving the muscle strength imbalance.

  16. Design of a Maglev Vibration Test Platform for the Research of Maglev Vehicle-girder Coupled Vibration Problem

    Directory of Open Access Journals (Sweden)

    Zhou Danfeng


    Full Text Available The maglev vehicle-girder coupled vibration problem has been encountered in many maglev test or commercial lines, which significantly degrade the performance of the maglev train. In previous research on the principle of the coupled vibration problem, it has been discovered that the fundamental model of the maglev girder can be simplified as a series of mass-spring resonators of different but related resonance frequencies, and that the stability of the vehicle-girder coupled system can be investigated by separately examining the stability of each mass-spring resonator – electromagnet coupled system. Based on this conclusion, a maglev test platform, which includes a single electromagnetic suspension control system, is built for experimental study of the coupled vibration problem. The guideway of the test platform is supported by a number of springs so as to change its flexibility. The mass of the guideway can also be changed by adjusting extra weights attached to it. By changing the flexibility and mass of the guideway, the rules of the maglev vehicle-girder coupled vibration problem are to be examined through experiments, and related theory on the vehicle-girder self-excited vibration proposed in previous research is also testified.

  17. Microgravity Active Vibration Isolation System on Parabolic Flights (United States)

    Dong, Wenbo; Pletser, Vladimir; Yang, Yang


    The Microgravity Active Vibration Isolation System (MAIS) aims at reducing on-orbit vibrations, providing a better controlled lower gravity environment for microgravity physical science experiments. The MAIS will be launched on Tianzhou-1, the first cargo ship of the China Manned Space Program. The principle of the MAIS is to suspend with electro-magnetic actuators a scientific payload, isolating it from the vibrating stator. The MAIS's vibration isolation capability is frequency-dependent and a decrease of vibration of about 40dB can be attained. The MAIS can accommodate 20kg of scientific payload or sample unit, and provide 30W of power and 1Mbps of data transmission. The MAIS is developed to support microgravity scientific experiments on manned platforms in low earth orbit, in order to meet the scientific requirements for fluid physics, materials science, and fundamental physics investigations, which usually need a very quiet environment, increasing their chances of success and their scientific outcomes. The results of scientific experiments and technology tests obtained with the MAIS will be used to improve future space based research. As the suspension force acting on the payload is very small, the MAIS can only be operative and tested in a weightless environment. The 'Deutsches Zentrum für Luft- und Raumfahrt e.V.' (DLR, German Aerospace Centre) granted a flight opportunity to the MAIS experiment to be tested during its 27th parabolic flight campaign of September 2015 performed on the A310 ZERO-G aircraft managed by the French company Novespace, a subsidiary of the 'Centre National d'Etudes Spatiales' (CNES, French Space Agency). The experiment results confirmed that the 6 degrees of freedom motion control technique was effective, and that the vibration isolation performance fulfilled perfectly the expectations based on theoretical analyses and simulations. This paper will present the design of the MAIS and the experiment results obtained during the

  18. Ultra-low vibration linear stirling cryogenic refrigerator for sub-nano resolution microscopy (United States)

    Riabzev, S. V.; Veprik, A. M.; Vilenchik, H. S.; Pundak, N.; Castiel, E.


    Wide use of so called "dry-cooling" technology, eventually replacing the LN2 cooling approach in high-resolution instrumentation, such as Scanning Electronic Microscopes, Helium Ion Microscopes, Superconductive Quantum Interference Devices, etc., motivates further quieting of appropriate cryogenic refrigerators. Linear Stirling cryogenic refrigerators are known to be a major source of harmful vibration export compromising the overall performance of vibration-sensitive equipment. The dual-piston approach to a design of a linear compressor yields inherently low vibration export and, therefore, is widely accepted across the industry. However, the residual vibration disturbance originated even from the technological tolerances, natural wear and contamination cannot be completely eliminated. Moreover, a vibration disturbance produced by a pneumatically driven cold head is much more powerful as compared to this of a compressor. The authors successfully redesigned the existing Ricor model K535 Stirling cryogenic refrigerator for use in vibration-sensitive electronic microscopy, where the image resolution is specified in angstroms. The objective was achieved by passive mechanical counterbalancing of the expander portion of the refrigerator, in a combination with an active two-axis control of residual vibrations, relying on National Instruments CompactRIO hardware, incorporating a real-time processor and reconfigurable FPGA for reliable stand-alone embedded application, developed using LabVIEW graphical programming tools. The attainable performance of the Ultra-Low Vibration linear Stirling cryogenic refrigerator RICOR model K535-ULV was evaluated through the full-scale experimentation.

  19. Analysis of muscle fatigue induced by isometric vibration exercise at varying frequencies. (United States)

    Mischi, M; Rabotti, C; Cardinale, M


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

  20. Vibration test report for in-chimney bracket and instrumented fuel assembly

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Jeong Soo; Yoon, D. B.; Cho, Y. G.; Ahn, G. H.; Lee, J. H.; Park, J.H


    The vibration levels of in-chimney bracket structure which is installed in reactor chimney and instrumented fuel assembly(Type-B Bundle) are investigated under the steady state normal operating condition of the reactor. For this purpose, 4 acceleration data on the guide tube of the instrumented fuel assembly and in-chimney bracket structures subjected to fluid induced vibration are measured. For the analysis of the vibration data, vibration analysis program which can perform basic time and frequency domain analysis, is prepared, and its reliability is verified by comparing the analysis results with those of commercial analysis program(I-DEAS). In time domain analysis, maximum amplitudes, and RMS values of accelerations and displacements from the measured vibration signal, are obtained. The frequency components of the vibration data are analyzed by using the frequency domain analysis. These analysis results show that the levels of the measured vibrations are within the allowable level, and the low frequency component near 10 Hz is dominant in the vibration signal. For the evaluation of the structural integrity on the in-chimney bracket and related structures including the instrumented fuel assembly, the static analysis for ANSYS finite element model is carried out. These analysis results show that the maximum stresses are within the allowable stresses of the ASME code, and the maximum displacement of the top of the flow tube is within the displacement limit. Therefore any damage on the structural integrity is not expected when the irradiation test is performed using the in-chimney bracket.