Random vibrations theory and practice
Wirsching, Paul H; Ortiz, Keith
1995-01-01
Random Vibrations: Theory and Practice covers the theory and analysis of mechanical and structural systems undergoing random oscillations due to any number of phenomena— from engine noise, turbulent flow, and acoustic noise to wind, ocean waves, earthquakes, and rough pavement. For systems operating in such environments, a random vibration analysis is essential to the safety and reliability of the system. By far the most comprehensive text available on random vibrations, Random Vibrations: Theory and Practice is designed for readers who are new to the subject as well as those who are familiar with the fundamentals and wish to study a particular topic or use the text as an authoritative reference. It is divided into three major sections: fundamental background, random vibration development and applications to design, and random signal analysis. Introductory chapters cover topics in probability, statistics, and random processes that prepare the reader for the development of the theory of random vibrations a...
Directory of Open Access Journals (Sweden)
Hendri Harmoko
2009-01-01
Full Text Available An effective vibration isolation system is important for hard disk drives (HDD used in a harsh mechanical environment. This paper describes how to design, simulate, test and evaluate vibration isolation systems for operating HDD subjected to severe shock and random vibrations based on military specifications MIL-STD-810E. The well-defined evaluation criteria proposed in this paper can be used to effectively assess the performance of HDD vibration isolation system. Design concepts on how to achieve satisfactory shock and vibration isolation for HDD are described. The concepts are tested and further enhanced by the two design case studies presented here. It is shown that an effective vibration isolation system, that will allow a HDD to operate well when subjected to severe shock and random vibration, is feasible.
Piezoelectric energy harvesting from broadband random vibrations
International Nuclear Information System (INIS)
Adhikari, S; Friswell, M I; Inman, D J
2009-01-01
Energy harvesting for the purpose of powering low power electronic sensor systems has received explosive attention in the last few years. Most works using deterministic approaches focusing on using the piezoelectric effect to harvest ambient vibration energy have concentrated on cantilever beams at resonance using harmonic excitation. Here, using a stochastic approach, we focus on using a stack configuration and harvesting broadband vibration energy, a more practically available ambient source. It is assumed that the ambient base excitation is stationary Gaussian white noise, which has a constant power-spectral density across the frequency range considered. The mean power acquired from a piezoelectric vibration-based energy harvester subjected to random base excitation is derived using the theory of random vibrations. Two cases, namely the harvesting circuit with and without an inductor, have been considered. Exact closed-form expressions involving non-dimensional parameters of the electromechanical system have been given and illustrated using numerical examples
Piezoelectric energy harvesting from broadband random vibrations
Adhikari, S.; Friswell, M. I.; Inman, D. J.
2009-11-01
Energy harvesting for the purpose of powering low power electronic sensor systems has received explosive attention in the last few years. Most works using deterministic approaches focusing on using the piezoelectric effect to harvest ambient vibration energy have concentrated on cantilever beams at resonance using harmonic excitation. Here, using a stochastic approach, we focus on using a stack configuration and harvesting broadband vibration energy, a more practically available ambient source. It is assumed that the ambient base excitation is stationary Gaussian white noise, which has a constant power-spectral density across the frequency range considered. The mean power acquired from a piezoelectric vibration-based energy harvester subjected to random base excitation is derived using the theory of random vibrations. Two cases, namely the harvesting circuit with and without an inductor, have been considered. Exact closed-form expressions involving non-dimensional parameters of the electromechanical system have been given and illustrated using numerical examples.
Removal of Stationary Sinusoidal Noise from Random Vibration Signals.
Energy Technology Data Exchange (ETDEWEB)
Johnson, Brian; Cap, Jerome S.
2018-02-01
In random vibration environments, sinusoidal line noise may appear in the vibration signal and can affect analysis of the resulting data. We studied two methods which remove stationary sine tones from random noise: a matrix inversion algorithm and a chirp-z transform algorithm. In addition, we developed new methods to determine the frequency of the tonal noise. The results show that both of the removal methods can eliminate sine tones in prefabricated random vibration data when the sine-to-random ratio is at least 0.25. For smaller ratios down to 0.02 only the matrix inversion technique can remove the tones, but the metrics to evaluate its effectiveness also degrade. We also found that using fast Fourier transforms best identified the tonal noise, and determined that band-pass-filtering the signals prior to the process improved sine removal. When applied to actual vibration test data, the methods were not as effective at removing harmonic tones, which we believe to be a result of mixed-phase sinusoidal noise.
Probability of Failure in Random Vibration
DEFF Research Database (Denmark)
Nielsen, Søren R.K.; Sørensen, John Dalsgaard
1988-01-01
Close approximations to the first-passage probability of failure in random vibration can be obtained by integral equation methods. A simple relation exists between the first-passage probability density function and the distribution function for the time interval spent below a barrier before out......-crossing. An integral equation for the probability density function of the time interval is formulated, and adequate approximations for the kernel are suggested. The kernel approximation results in approximate solutions for the probability density function of the time interval and thus for the first-passage probability...
Topics in random walks in random environment
International Nuclear Information System (INIS)
Sznitman, A.-S.
2004-01-01
Over the last twenty-five years random motions in random media have been intensively investigated and some new general methods and paradigms have by now emerged. Random walks in random environment constitute one of the canonical models of the field. However in dimension bigger than one they are still poorly understood and many of the basic issues remain to this day unresolved. The present series of lectures attempt to give an account of the progresses which have been made over the last few years, especially in the study of multi-dimensional random walks in random environment with ballistic behavior. (author)
Force Limited Random Vibration Test of TESS Camera Mass Model
Karlicek, Alexandra; Hwang, James Ho-Jin; Rey, Justin J.
2015-01-01
The Transiting Exoplanet Survey Satellite (TESS) is a spaceborne instrument consisting of four wide field-of-view-CCD cameras dedicated to the discovery of exoplanets around the brightest stars. As part of the environmental testing campaign, force limiting was used to simulate a realistic random vibration launch environment. While the force limit vibration test method is a standard approach used at multiple institutions including Jet Propulsion Laboratory (JPL), NASA Goddard Space Flight Center (GSFC), European Space Research and Technology Center (ESTEC), and Japan Aerospace Exploration Agency (JAXA), it is still difficult to find an actual implementation process in the literature. This paper describes the step-by-step process on how the force limit method was developed and applied on the TESS camera mass model. The process description includes the design of special fixtures to mount the test article for properly installing force transducers, development of the force spectral density using the semi-empirical method, estimation of the fuzzy factor (C2) based on the mass ratio between the supporting structure and the test article, subsequent validating of the C2 factor during the vibration test, and calculation of the C.G. accelerations using the Root Mean Square (RMS) reaction force in the spectral domain and the peak reaction force in the time domain.
Yoon, Heonjun; Kim, Miso; Park, Choon-Su; Youn, Byeng D.
2018-01-01
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.
Energy Technology Data Exchange (ETDEWEB)
Cryns, Jackson W.; Hatchell, Brian K.; Santiago-Rojas, Emiliano; Silvers, Kurt L.
2013-07-01
Formal journal article Experimental analysis of a piezoelectric energy harvesting system for harmonic, random, and sine on random vibration Abstract: Harvesting power with a piezoelectric vibration powered generator using a full-wave rectifier conditioning circuit is experimentally compared for varying sinusoidal, random and sine on random (SOR) input vibration scenarios. Additionally, the implications of source vibration characteristics on harvester design are discussed. Studies in vibration harvesting have yielded numerous alternatives for harvesting electrical energy from vibrations but piezoceramics arose as the most compact, energy dense means of energy transduction. The rise in popularity of harvesting energy from ambient vibrations has made piezoelectric generators commercially available. Much of the available literature focuses on maximizing harvested power through nonlinear processing circuits that require accurate knowledge of generator internal mechanical and electrical characteristics and idealization of the input vibration source, which cannot be assumed in general application. In this manuscript, variations in source vibration and load resistance are explored for a commercially available piezoelectric generator. We characterize the source vibration by its acceleration response for repeatability and transcription to general application. The results agree with numerical and theoretical predictions for in previous literature that load optimal resistance varies with transducer natural frequency and source type, and the findings demonstrate that significant gains are seen with lower tuned transducer natural frequencies for similar source amplitudes. Going beyond idealized steady state sinusoidal and simplified random vibration input, SOR testing allows for more accurate representation of real world ambient vibration. It is shown that characteristic interactions from more complex vibrational sources significantly alter power generation and power processing
Directory of Open Access Journals (Sweden)
Jackson W. Cryns
2013-01-01
Full Text Available Harvesting power with a piezoelectric vibration powered generator using a full-wave rectifier conditioning circuit is experimentally compared for varying sinusoidal, random, and sine on random (SOR input vibration scenarios; the implications of source vibration characteristics on harvester design are discussed. The rise in popularity of harvesting energy from ambient vibrations has made compact, energy dense piezoelectric generators commercially available. Much of the available literature focuses on maximizing harvested power through nonlinear processing circuits that require accurate knowledge of generator internal mechanical and electrical characteristics and idealization of the input vibration source, which cannot be assumed in general application. Variations in source vibration and load resistance are explored for a commercially available piezoelectric generator. The results agree with numerical and theoretical predictions in the previous literature for optimal power harvesting in sinusoidal and flat broadband vibration scenarios. Going beyond idealized steady-state sinusoidal and flat random vibration input, experimental SOR testing allows for more accurate representation of real world ambient vibration. It is shown that characteristic interactions from more complex vibration sources significantly alter power generation and processing requirements by varying harvested power, shifting optimal conditioning impedance, inducing voltage fluctuations, and ultimately rendering idealized sinusoidal and random analyses incorrect.
Qubits in a random environment
International Nuclear Information System (INIS)
Akhalwaya, I; Fannes, M; Petruccione, F
2007-01-01
Decoherence phenomena in a small quantum system coupled to a complex environment can be modelled with random matrices. We propose a simple deterministic model in the limit of a high dimensional environment. The model is investigated numerically and some analytically addressable questions are singled out
Simulation of nonlinear random vibrations using artificial neural networks
Energy Technology Data Exchange (ETDEWEB)
Paez, T.L.; Tucker, S.; O`Gorman, C.
1997-02-01
The simulation of mechanical system random vibrations is important in structural dynamics, but it is particularly difficult when the system under consideration is nonlinear. Artificial neural networks provide a useful tool for the modeling of nonlinear systems, however, such modeling may be inefficient or insufficiently accurate when the system under consideration is complex. This paper shows that there are several transformations that can be used to uncouple and simplify the components of motion of a complex nonlinear system, thereby making its modeling and random vibration simulation, via component modeling with artificial neural networks, a much simpler problem. A numerical example is presented.
Random walk through fractal environments
Isliker, H.; Vlahos, L.
2002-01-01
We analyze random walk through fractal environments, embedded in 3-dimensional, permeable space. Particles travel freely and are scattered off into random directions when they hit the fractal. The statistical distribution of the flight increments (i.e. of the displacements between two consecutive hittings) is analytically derived from a common, practical definition of fractal dimension, and it turns out to approximate quite well a power-law in the case where the dimension D of the fractal is ...
Acceleration/vibration combined environment activities. Interim report
International Nuclear Information System (INIS)
Shuman, R.L.
1980-01-01
The combining of two environments, i.e., linear acceleration and vibration, for use in laboratory testing to determine the damage to some mechanical devices when simultaneously subjected to these two environments, is discussed. The use of a Genisco centrifuge with an Unholtz-Dickie vibration machine mounted on it is described. Initial efforts at operating a shaker on the centrifuge have not been completely successful, so modifications to the system are being made
RMS fatigue curves for random vibrations
International Nuclear Information System (INIS)
Brenneman, B.; Talley, J.G.
1984-01-01
Fatigue usage factors for deterministic or constant amplitude vibration stresses may be calculated with well known procedures and fatigue curves given in the ASME Boiler and Pressure Vessel Code. However, some phenomena produce nondeterministic cyclic stresses which can only be described and analyzed with statistical concepts and methods. Such stresses may be caused by turbulent fluid flow over a structure. Previous methods for solving this statistical fatigue problem are often difficult to use and may yield inaccurate results. Two such methods examined herein are Crandall's method and the ''3sigma'' method. The objective of this paper is to provide a method for creating ''RMS fatigue curves'' which accurately incorporate the requisite statistical information. These curves are given and may be used by analysts with the same ease and in the same manner as the ASME fatigue curves
Characterization and synthesis of random acceleration vibration specifications
Wijker, Jacob J; Ellenbroek, Marcellinus Hermannus Maria; de Boer, Andries; Papadrakakis, M.; Lagaros, N.D.; Plevris, V.
2013-01-01
Random acceleration vibration specifications for subsystems, i.e. instruments, equipment, are most times based on measurement during acoustic noise tests on system level, i.e. a spacecraft and measured by accelerometers, placed in the neighborhood of the interface between spacecraft and subsystem.
Inficon Transpector MPH Mass Spectrometer Random Vibration Test Report
Santiago-Bond, Jo; Captain, Janine
2015-01-01
The purpose of this test report is to summarize results from the vibration testing of the INFICON Transpector MPH100M model Mass Spectrometer. It also identifies requirements satisfied, and procedures used in the test. As a payload of Resource Prospector, it is necessary to determine the survivability of the mass spectrometer to proto-qualification level random vibration. Changes in sensitivity of the mass spectrometer can be interpreted as a change in alignment of the instrument. The results of this test will be used to determine any necessary design changes as the team moves forward with flight design.
Random walk through fractal environments
International Nuclear Information System (INIS)
Isliker, H.; Vlahos, L.
2003-01-01
We analyze random walk through fractal environments, embedded in three-dimensional, permeable space. Particles travel freely and are scattered off into random directions when they hit the fractal. The statistical distribution of the flight increments (i.e., of the displacements between two consecutive hittings) is analytically derived from a common, practical definition of fractal dimension, and it turns out to approximate quite well a power-law in the case where the dimension D F of the fractal is less than 2, there is though, always a finite rate of unaffected escape. Random walks through fractal sets with D F ≤2 can thus be considered as defective Levy walks. The distribution of jump increments for D F >2 is decaying exponentially. The diffusive behavior of the random walk is analyzed in the frame of continuous time random walk, which we generalize to include the case of defective distributions of walk increments. It is shown that the particles undergo anomalous, enhanced diffusion for D F F >2 is normal for large times, enhanced though for small and intermediate times. In particular, it follows that fractals generated by a particular class of self-organized criticality models give rise to enhanced diffusion. The analytical results are illustrated by Monte Carlo simulations
A comparison of random walks in dependent random environments
Scheinhardt, Willem R.W.; Kroese, Dirk
We provide exact computations for the drift of random walks in dependent random environments, including $k$-dependent and moving average environments. We show how the drift can be characterized and evaluated using Perron–Frobenius theory. Comparing random walks in various dependent environments, we
Insights from random vibration analyses using multiple earthquake components
International Nuclear Information System (INIS)
DebChaudhury, A.; Gasparini, D.A.
1981-01-01
The behavior of multi-degree-of-freedom systems subjected to multiple earthquake components is studied by the use of random vibration dynamic analyses. A linear system which has been decoupled into modes and has both translational and rotational degrees of freedom is analyzed. The seismic excitation is modelled as a correlated or uncorrelated, vector-valued, non-stationary random process having a Kanai-Tajimi type of frequency content. Non-stationarity is achieved by using a piece wise linear strength function. Therefore, almost any type of evolution and decay of an earthquake may be modelled. Also, in general, the components of the excitation have different frequency contents and strength functions; i.e. intensities and durations and the correlations between components can vary with time. A state-space, modal, random vibration approach is used. Exact analytical expressions for both the state transition matrix and the evolutionary modal covariance matrix are utilized to compute time histories of modal RMS responses. Desired responses are then computed by modal superposition. Specifically, relative displacement, relative velocity and absolute acceleration responses are studied. An important advantage of such analyses is that RMS responses vary smoothly in time therefore large time intervals may be used to generate response time histories. The modal superposition is exact; that is, all cross correlation terms between modal responses are included. (orig./RW)
International Nuclear Information System (INIS)
Perotin, L.; Granger, S.
1997-01-01
In order to improve the prediction of wear problems due to flow-induced vibration in PWR components, an inverse method for identifying a distributed random excitation acting on a dynamical system has been developed at EDF. This method, whose applications go far beyond the flow-induced vibration field, has been implemented into the MEIDEE software. This method is presented. (author)
Knots and Random Walks in Vibrated Granular Chains
International Nuclear Information System (INIS)
Ben-Naim, E.; Daya, Z. A.; Vorobieff, P.; Ecke, R. E.
2001-01-01
We study experimentally statistical properties of the opening times of knots in vertically vibrated granular chains. Our measurements are in good qualitative and quantitative agreement with a theoretical model involving three random walks interacting via hard-core exclusion in one spatial dimension. In particular, the knot survival probability follows a universal scaling function which is independent of the chain length, with a corresponding diffusive characteristic time scale. Both the large-exit-time and the small-exit-time tails of the distribution are suppressed exponentially, and the corresponding decay coefficients are in excellent agreement with theoretical values
Damping Estimation of Friction Systems in Random Vibrations
DEFF Research Database (Denmark)
Friis, Tobias; Katsanos, Evangelos; Amador, Sandro
Friction is one of the most efficient and economical mechanisms to reduce vibrations in structural mechanics. However, the estimation of the equivalent linear damping of the friction damped systems in experimental modal analysis and operational modal analysis can be adversely affected by several...... assumptions regarding the definition of the linear damping and the identification methods or may be lacking a meaningful interpretation of the damping. Along these lines, this project focuses on assessing the potential to estimate efficiently the equivalent linear damping of friction systems in random...
Random Vibration of Space Shuttle Weather Protection Systems
Directory of Open Access Journals (Sweden)
Isaac Elishakoff
1995-01-01
Full Text Available The article deals with random vibrations of the space shuttle weather protection systems. The excitation model represents a fit to the measured experimental data. The cross-spectral density is given as a convex combination of three exponential functions. It is shown that for the type of loading considered, the Bernoulli-Euler theory cannot be used as a simplified approach, and the structure will be more properly modeled as a Timoshenko beam. Use of the simple Bernoulli-Euler theory may result in an error of about 50% in determining the mean-square value of the bending moment in the weather protection system.
International Nuclear Information System (INIS)
Spreemann, Dirk; Hoffmann, Daniel; Folkmer, Bernd; Manoli, Yiannos
2008-01-01
This paper presents a design and optimization strategy for resonant electromagnetic vibration energy harvesting devices. An analytic expression for the magnetic field of cylindrical permanent magnets is used to build up an electromagnetic subsystem model. This subsystem is used to find the optimal resting position of the oscillating mass and to optimize the geometrical parameters (shape and size) of the magnet and coil. The objective function to be investigated is thereby the maximum voltage output of the transducer. An additional mechanical subsystem model based on well-known equations describing the dynamics of spring–mass–damper systems is established to simulate both nonlinear spring characteristics and the effect of internal limit stops. The mechanical subsystem enables the identification of optimal spring characteristics for realistic operation conditions such as stochastic vibrations. With the overall transducer model, a combination of both subsystems connected to a simple electrical circuit, a virtual operation of the optimized vibration transducer excited by a measured random acceleration profile can be performed. It is shown that the optimization approach results in an appreciable increase of the converter performance
Power Delivered to Mechanical Systems by Random Vibrations
Directory of Open Access Journals (Sweden)
Timothy S. Edwards
2009-01-01
Full Text Available This paper develops deformational response power descriptions of multiple degree-of-freedom systems due to stationary random vibration excitation. Two new concepts are developed. The deformational response power density (DRPD can be computed when a structure's natural frequencies and modal masses are available. The DRPD shows the spectral content of the deformational power delivered to a specific structure by the stationary, random excitation. This function can be found through a weighted windowing of the power spectrum of the input acceleration excitation. Deformational response input power spectra (DRIPS, similar to the input energy spectrum and shock response spectrum, give the power delivered to single-degree-of-freedom systems as a function of natural frequency. It is shown that the DRIPS is simply a smoothed version of the power spectrum of the input acceleration excitation. The DRIPS gives rise to a useful power-based data smoothing operation.
Random Vibration Testing of Advanced Wet Tantalum Capacitors
Teverovsky, Alexander
2015-01-01
Advanced wet tantalum capacitors allow for improved performance of power supply systems along with substantial reduction of size and weight of the systems that is especially beneficial for space electronics. Due to launch-related stresses, acceptance testing of all space systems includes random vibration test (RVT). However, many types of advanced wet tantalum capacitors cannot pass consistently RVT at conditions specified in MIL-PRF-39006, which impedes their use in space projects. This requires a closer look at the existing requirements, modes and mechanisms of failures, specifics of test conditions, and acceptance criteria. In this work, different lots of advanced wet tantalum capacitors from four manufacturers have been tested at step stress random vibration conditions while their currents were monitored before, during, and after the testing. It has been shown that the robustness of the parts and their reliability are mostly due to effective self-healing processes and limited current spiking or minor scintillations caused by RVT do not increase the risk of failures during operation. A simple model for scintillations events has been used to simulate current spiking during RVT and optimize test conditions. The significance of scintillations and possible effects of gas generation have been discussed and test acceptance criteria for limited current spiking have been suggested.
CR-Calculus and adaptive array theory applied to MIMO random vibration control tests
Musella, U.; Manzato, S.; Peeters, B.; Guillaume, P.
2016-09-01
Performing Multiple-Input Multiple-Output (MIMO) tests to reproduce the vibration environment in a user-defined number of control points of a unit under test is necessary in applications where a realistic environment replication has to be achieved. MIMO tests require vibration control strategies to calculate the required drive signal vector that gives an acceptable replication of the target. This target is a (complex) vector with magnitude and phase information at the control points for MIMO Sine Control tests while in MIMO Random Control tests, in the most general case, the target is a complete spectral density matrix. The idea behind this work is to tailor a MIMO random vibration control approach that can be generalized to other MIMO tests, e.g. MIMO Sine and MIMO Time Waveform Replication. In this work the approach is to use gradient-based procedures over the complex space, applying the so called CR-Calculus and the adaptive array theory. With this approach it is possible to better control the process performances allowing the step-by-step Jacobian Matrix update. The theoretical bases behind the work are followed by an application of the developed method to a two-exciter two-axis system and by performance comparisons with standard methods.
A simplified method for random vibration analysis of structures with random parameters
International Nuclear Information System (INIS)
Ghienne, Martin; Blanzé, Claude
2016-01-01
Piezoelectric patches with adapted electrical circuits or viscoelastic dissipative materials are two solutions particularly adapted to reduce vibration of light structures. To accurately design these solutions, it is necessary to describe precisely the dynamical behaviour of the structure. It may quickly become computationally intensive to describe robustly this behaviour for a structure with nonlinear phenomena, such as contact or friction for bolted structures, and uncertain variations of its parameters. The aim of this work is to propose a non-intrusive reduced stochastic method to characterize robustly the vibrational response of a structure with random parameters. Our goal is to characterize the eigenspace of linear systems with dynamic properties considered as random variables. This method is based on a separation of random aspects from deterministic aspects and allows us to estimate the first central moments of each random eigenfrequency with a single deterministic finite elements computation. The method is applied to a frame with several Young's moduli modeled as random variables. This example could be expanded to a bolted structure including piezoelectric devices. The method needs to be enhanced when random eigenvalues are closely spaced. An indicator with no additional computational cost is proposed to characterize the ’’proximity” of two random eigenvalues. (paper)
Reduction method for residual stress of welded joint using random vibration
International Nuclear Information System (INIS)
Aoki, Shigeru; Nishimura, Tadashi; Hiroi, Tetsumaro
2005-01-01
Welded joints are used for construction of many structures. Residual stress is induced near the bead caused by locally given heat. Tensile residual stress on the surface may reduce fatigue strength. In this paper, a new method for reduction of residual stress using vibration during welding is proposed. As vibrational load, random vibration, white noise and filtered white noise are used. Two thin plates are butt-welded. Residual stress is measured with a paralleled beam X-ray diffractometer with scintillation counter after removing quenched scale chemically. It is concluded that tensile residual stress near the bead is reduced by using random vibration during welding
A comparison of random walks in dependent random environments
Scheinhardt, Willem R.W.; Kroese, Dirk
2015-01-01
Although the theoretical behavior of one-dimensional random walks in random environments is well understood, the actual evaluation of various characteristics of such processes has received relatively little attention. This paper develops new methodology for the exact computation of the drift in such
Using piezo-electric material to simulate a vibration environment
Jepsen, Richard A.; Davie, Neil T.; Vangoethem, Douglas J.; Romero, Edward F.
2010-12-14
A target object can be vibrated using actuation that exploits the piezo-electric ("PE") property. Under combined conditions of vibration and centrifugal acceleration, a centrifugal load of the target object on PE vibration actuators can be reduced by using a counterweight that offsets the centrifugal loading. Target objects are also subjected to combinations of: spin, vibration, and acceleration; spin and vibration; and spin and acceleration.
Coupled continuous time-random walks in quenched random environment
Magdziarz, M.; Szczotka, W.
2018-02-01
We introduce a coupled continuous-time random walk with coupling which is characteristic for Lévy walks. Additionally we assume that the walker moves in a quenched random environment, i.e. the site disorder at each lattice point is fixed in time. We analyze the scaling limit of such a random walk. We show that for large times the behaviour of the analyzed process is exactly the same as in the case of uncoupled quenched trap model for Lévy flights.
Neutron flux response to regulating rod random vibrations
International Nuclear Information System (INIS)
Dach, K.; Nemec, J.; Pecinka, L.
The relation is presented for the mean square value of the deflection of the rod for the n-th vibration shape on an arbitrary site. The relation may serve the obtaining of a variable which may be used both in a mechanical, i.e., stress analysis and in the determination of neutron flux fluctuations. It is demonstrated that the vibration frequency introduced in the reactor by the regulating rod has the same response in the neutron flux. This effect was used in the localization of an enormously vibrating regulating rod. (J.P.)
Study on Nonlinear Vibration Analysis of Gear System with Random Parameters
Tong, Cao; Liu, Xiaoyuan; Fan, Li
2018-03-01
In order to study the dynamic characteristics of gear nonlinear vibration system and the influence of random parameters, firstly, a nonlinear stochastic vibration analysis model of gear 3-DOF is established based on Newton’s Law. And the random response of gear vibration is simulated by stepwise integration method. Secondly, the influence of stochastic parameters such as meshing damping, tooth side gap and excitation frequency on the dynamic response of gear nonlinear system is analyzed by using the stability analysis method such as bifurcation diagram and Lyapunov exponent method. The analysis shows that the stochastic process can not be neglected, which can cause the random bifurcation and chaos of the system response. This study will provide important reference value for vibration engineering designers.
Effect of Vibration on Pain Response to Heel Lance: A Pilot Randomized Control Trial.
McGinnis, Kate; Murray, Eileen; Cherven, Brooke; McCracken, Courtney; Travers, Curtis
2016-12-01
Applied mechanical vibration in pediatric and adult populations has been shown to be an effective analgesic for acute and chronic pain, including needle pain. Studies among the neonatal population are lacking. According to the Gate Control Theory, it is expected that applied mechanical vibration will have a summative effect with standard nonpharmacologic pain control strategies, reducing behavioral and physiologic pain responses to heel lancing. To determine the safety and efficacy of mechanical vibration for relief of heel lance pain among neonates. In this parallel design randomized controlled trial, eligible enrolled term or term-corrected neonates (n = 56) in a level IV neonatal intensive care unit were randomized to receive either sucrose and swaddling or sucrose, swaddling, and vibration for heel lance analgesia. Vibration was applied using a handheld battery-powered vibrator (Norco MiniVibrator, Hz = 92) to the lateral aspect of the lower leg along the sural dermatome throughout the heel lance procedure. Neonatal Pain, Agitation, and Sedation Scale (N-PASS) scores, heart rate, and oxygen saturations were collected at defined intervals surrounding heel lancing. Infants in the vibration group (n = 30) had significantly lower N-PASS scores and more stable heart rates during heel stick (P = .006, P = .037) and 2 minutes after heel lance (P = .002, P = .016) than those in the nonvibration group. There were no adverse behavioral or physiologic responses to applied vibration in the sample. Applied mechanical vibration is a safe and effective method for managing heel lance pain. This pilot study suggests that mechanical vibration warrants further exploration as a nonpharmacologic pain management tool among the neonatal population.
On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration
Directory of Open Access Journals (Sweden)
Fei Xu
2016-01-01
Full Text Available Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data is usually non-Gaussian. Two methodologies are presented in this paper for shaker simulation of wind-induced non-Gaussian vibration. The first methodology synthesizes the non-Gaussian signal offline and replicates it on the shaker in the Time Waveform Replication (TWR mode. A new synthesis method is used to model the non-Gaussian signal as a Gaussian signal multiplied by an amplitude modulation function (AMF. A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD, probability density function (PDF, and loading cycle distribution (LCD as the field data. The second methodology derives a damage equivalent Gaussian signal from the non-Gaussian signal based on the fatigue damage spectrum (FDS and the extreme response spectrum (ERS and reproduces it on the shaker in the closed-loop frequency domain control mode. The PSD level and the duration time of the derived Gaussian signal can be manipulated for accelerated testing purpose. A case study is presented to show that the derived PSD matches the damage potential of the non-Gaussian environment for both fatigue and peak response.
Angeli, Andrea; Cornelis, Bram; Troncossi, Marco
2018-03-01
In many real life environments, mechanical and electronic systems are subjected to vibrations that may induce dynamic loads and potentially lead to an early failure due to fatigue damage. Thus, qualification tests by means of shakers are advisable for the most critical components in order to verify their durability throughout the entire life cycle. Nowadays the trend is to tailor the qualification tests according to the specific application of the tested component, considering the measured field data as reference to set up the experimental campaign, for example through the so called "Mission Synthesis" methodology. One of the main issues is to define the excitation profiles for the tests, that must have, besides the (potentially scaled) frequency content, also the same damage potential of the field data despite being applied for a limited duration. With this target, the current procedures generally provide the test profile as a stationary random vibration specified by a Power Spectral Density (PSD). In certain applications this output may prove inadequate to represent the nature of the reference signal, and the procedure could result in an unrealistic qualification test. For instance when a rotating part is present in the system the component under analysis may be subjected to Sine-on-Random (SoR) vibrations, namely excitations composed of sinusoidal contributions superimposed to random vibrations. In this case, the synthesized test profile should preserve not only the induced fatigue damage but also the deterministic components of the environmental vibration. In this work, the potential advantages of a novel procedure to synthesize SoR profiles instead of PSDs for qualification tests are presented and supported by the results of an experimental campaign.
International Nuclear Information System (INIS)
Preumont, A.; Shilab, S.; Cornaggia, L.; Reale, M.; Labbe, P.; Noe, H.
1992-01-01
This benchmark exercise is the continuation of the state-of-the-art review (EUR 11369 EN) which concluded that the random vibration approach could be an effective tool in seismic analysis of nuclear power plants, with potential advantages on time history and response spectrum techniques. As compared to the latter, the random vibration method provides an accurate treatment of multisupport excitations, non classical damping as well as the combination of high-frequency modal components. With respect to the former, the random vibration method offers direct information on statistical variability (probability distribution) and cheaper computations. The disadvantages of the random vibration method are that it is based on stationary results, and requires a power spectral density input instead of a response spectrum. A benchmark exercise to compare the three methods from the various aspects mentioned above, on one or several simple structures has been made. The following aspects have been covered with the simplest possible models: (i) statistical variability, (ii) multisupport excitation, (iii) non-classical damping. The random vibration method is therefore concluded to be a reliable method of analysis. Its use is recommended, particularly for preliminary design, owing to its computational advantage on multiple time history analysis
International Nuclear Information System (INIS)
Perevezentsev, V.V.
2012-01-01
The generalizing empirical dependences of vibration movements on the random hydrodynamic loads have been obtained. Two characteristic regions of the influence of random hydrodynamic loads on the vibration movements have been discovered. With the values of random hydrodynamic loads more than 80 N/m, a considerable increase in the intensity of vibrations has been observed. It can be explained by the slippage of fuel element in the cell of the spacing lattice [ru
Analytical and Experimental Random Vibration of Nonlinear Aeroelastic Structures.
1987-01-28
vibrations. In civil engineenng the mechanical and strength eccentricity in the disks. Parameter variations exist in disk properties of the material vary...support. define the loading and resistance strength of the structure. Figure 10 shows the comparison between theoretical and experi- mental natural... dinamics . Sijthoff- Hilton, H H. and Feigen. M. Minimum weight analysis based on structural Noordhoff Co, Netherlands. reliability. J Aerospace Sc, 27
Dual resonant structure for energy harvesting from random vibration sources at low frequency
Directory of Open Access Journals (Sweden)
Shanshan Li
2016-01-01
Full Text Available We introduce a design with dual resonant structure which can harvest energy from random vibration sources at low frequency range. The dual resonant structure consists of two spring-mass subsystems with different frequency responses, which exhibit strong coupling and broad bandwidth when the two masses collide with each other. Experiments with piezoelectric elements show that the energy harvesting device with dual resonant structure can generate higher power output than the sum of the two separate devices from random vibration sources.
Zhang, Yulong; Wang, Tianyang; Zhang, Ai; Peng, Zhuoteng; Luo, Dan; Chen, Rui; Wang, Fei
2016-12-01
In this paper, we present design and test of a broadband electrostatic energy harvester with a dual resonant structure, which consists of two cantilever-mass subsystems each with a mass attached at the free edge of a cantilever. Comparing to traditional devices with single resonant frequency, the proposed device with dual resonant structure can resonate at two frequencies. Furthermore, when one of the cantilever-masses is oscillating at resonance, the vibration amplitude is large enough to make it collide with the other mass, which provides strong mechanical coupling between the two subsystems. Therefore, this device can harvest a decent power output from vibration sources at a broad frequency range. During the measurement, continuous power output up to 6.2-9.8 μW can be achieved under external vibration amplitude of 9.3 m/s 2 at a frequency range from 36.3 Hz to 48.3 Hz, which means the bandwidth of the device is about 30% of the central frequency. The broad bandwidth of the device provides a promising application for energy harvesting from the scenarios with random vibration sources. The experimental results indicate that with the dual resonant structure, the vibration-to-electricity energy conversion efficiency can be improved by 97% when an external random vibration with a low frequency filter is applied.
Characterization of Friction Joints Subjected to High Levels of Random Vibration
deSantos, Omar; MacNeal, Paul
2012-01-01
This paper describes the test program in detail including test sample description, test procedures, and vibration test results of multiple test samples. The material pairs used in the experiment were Aluminum-Aluminum, Aluminum- Dicronite coated Aluminum, and Aluminum-Plasmadize coated Aluminum. Levels of vibration for each set of twelve samples of each material pairing were gradually increased until all samples experienced substantial displacement. Data was collected on 1) acceleration in all three axes, 2) relative static displacement between vibration runs utilizing photogrammetry techniques, and 3) surface galling and contaminant generation. This data was used to estimate the values of static friction during random vibratory motion when "stick-slip" occurs and compare these to static friction coefficients measured before and after vibration testing.
Simeonov, P; Hsiao, H; Powers, J; Ammons, D; Kau, T; Amendola, A
2011-07-01
The risk of falls from height on a construction site increases under conditions which degrade workers' postural control. At elevation, workers depend heavily on sensory information from their feet to maintain balance. The study tested two hypotheses: "sensory enhancement"--sub-sensory (undetectable) random mechanical vibrations at the plantar surface of the feet can improve worker's balance at elevation; and "sensory suppression"--supra-sensory (detectable) random mechanical vibrations can have a degrading effect on balance in the same experimental settings. Six young (age 20-35) and six aging (age 45-60) construction workers were tested while standing in standard and semi-tandem postures on instrumented gel insoles. The insoles applied sub- or supra-sensory levels of random mechanical vibrations to the feet. The tests were conducted in a surround-screen virtual reality system, which simulated a narrow plank at elevation on a construction site. Upper body kinematics was assessed with a motion-measurement system. Postural stability effects were evaluated by conventional and statistical mechanics sway measures, as well as trunk angular displacement parameters. Analysis of variance did not confirm the "sensory enhancement" hypothesis, but provided evidence for the "sensory suppression" hypothesis. The supra-sensory vibration had a destabilizing effect, which was considerably stronger in the semi-tandem posture and affected most of the sway variables. Sensory suppression associated with elevated vibration levels on a construction site may increase the danger of losing balance. Construction workers at elevation, e.g., on a beam or narrow plank might be at increased risk of fall if they can detect vibrations under their feet. To reduce the possibility of losing balance, mechanical vibration to supporting structures used as walking/working surfaces should be minimized when performing construction tasks at elevation. Published by Elsevier Ltd.
Distributed fiber sparse-wideband vibration sensing by sub-Nyquist additive random sampling
Zhang, Jingdong; Zheng, Hua; Zhu, Tao; Yin, Guolu; Liu, Min; Bai, Yongzhong; Qu, Dingrong; Qiu, Feng; Huang, Xianbing
2018-05-01
The round trip time of the light pulse limits the maximum detectable vibration frequency response range of phase-sensitive optical time domain reflectometry ({\\phi}-OTDR). Unlike the uniform laser pulse interval in conventional {\\phi}-OTDR, we randomly modulate the pulse interval, so that an equivalent sub-Nyquist additive random sampling (sNARS) is realized for every sensing point of the long interrogation fiber. For an {\\phi}-OTDR system with 10 km sensing length, the sNARS method is optimized by theoretical analysis and Monte Carlo simulation, and the experimental results verify that a wide-band spars signal can be identified and reconstructed. Such a method can broaden the vibration frequency response range of {\\phi}-OTDR, which is of great significance in sparse-wideband-frequency vibration signal detection, such as rail track monitoring and metal defect detection.
DETERMINING THE RESPONSE IN CASE OF VIBRATIONS OF STRAIGHT BARS WITH RANDOM EXCITATIONS
Directory of Open Access Journals (Sweden)
Monica BALDEA
2012-05-01
Full Text Available By applying the finite element calculus to the study of bar vibrations, one obtains a system of linear diferential equations. One carries out the determination of the response to random stimulations by calculating the statistical terms as a function of the statistical terms of the stimulation
Stark, C.; Herkenrath, P.; Hollmann, H.; Waltz, S.; Becker, I.; Hoebing, L.; Semler, O.; Hoyer-Kuhn, H.; Duran, I.; Hero, B.; Hadders-Algra, M.; Schoenau, E.
OBJECTIVES: to investigate feasibility, safety and efficacy of home-based side-alternating whole body vibration (sWBV) to improve motor function in toddlers with cerebral palsy (CP). METHODS: Randomized controlled trial including 24 toddlers with CP (mean age 19 months (SD±3.1); 13 boys).
Snake representation of a superprocess in random environment
Mytnik, Leonid; Xiong, Jie; Zeitouni, Ofer
2011-01-01
We consider (discrete time) branching particles in a random environment which is i.i.d. in time and possibly spatially correlated. We prove a representation of the limit process by means of a Brownian snake in random environment.
Computer evaluation of random signals from vibration acoustic diagnostics
International Nuclear Information System (INIS)
Bahna, J.
1979-01-01
Definitions and relations are shown for the calculation of the characteristics of random signals used, such as the amplitude probability density, correlation functions and power spectral densities. The methods are described of digitizing a continuous signal for calculating the above characteristics. The algorithm of the fast Fourier transformation was used in the calculation. The design is described of a system whose essential part is an analog-to-digital converter. The system software is also described. (J.B.)
Fatigue failure of pb-free electronic packages under random vibration loads
Saravanan, S.; Prabhu, S.; Muthukumar, R.; Gowtham Raj, S.; Arun Veerabagu, S.
2018-03-01
The electronic equipment are used in several fields like, automotive, aerospace, consumer goods where they are subjected to vibration loads leading to failure of solder joints used in these equipment. This paper presents a methodology to predict the fatigue life of Pb-free surface mounted BGA packages subjected to random vibrations. The dynamic characteristics of the PCB, such as the natural frequencies, mode shapes and damping ratios were determined. Spectrum analysis was used to determine the stress response of the critical solder joint and the cumulative fatigue damage accumulated by the solder joint for a specific duration was determined.
Application of the random vibration approach in the seismic analysis of LMFBR structures
International Nuclear Information System (INIS)
Preumont, A.
1988-01-01
The first part discusses the general topic of the spectral analysis of linear multi-degree-of-freedom structure subjected to a stationary random field. Particular attention is given to structures with non-classical damping and hereditary characteristics. The method is implemented in the computer programme RANDOM. Next, the same concepts are applied to multi-supported structures subjected to a stationary seismic excitation. The method is implemented in the computer programme SEISME. Two related problems are dealt with in the next two chapters: (i) the relation between the input of the random vibration analysis and the traditional ground motion specification for seismic analysis (the Design Response Spectra) and (ii) the application of random vibration techniques to the direct generation of floor response spectra. Finally the problem of extracting information from costly time history analyses is addressed. This study has mainly been concerned with the methodology and the development of appropriate softwares. Some qualitative conclusions have been drawn regarding the expected benefit of the approach. They have been judged promising enough to motivate a benchmark exercise. Specifically, the random vibration approach will be compared to the current approximate methods (response spectrum) and time-history analyses (considered as representative of the true response) for a set of typical structures. The hope is that some of the flaws of the current approximate methods can be removed
Gray bootstrap method for estimating frequency-varying random vibration signals with small samples
Directory of Open Access Journals (Sweden)
Wang Yanqing
2014-04-01
Full Text Available During environment testing, the estimation of random vibration signals (RVS is an important technique for the airborne platform safety and reliability. However, the available methods including extreme value envelope method (EVEM, statistical tolerances method (STM and improved statistical tolerance method (ISTM require large samples and typical probability distribution. Moreover, the frequency-varying characteristic of RVS is usually not taken into account. Gray bootstrap method (GBM is proposed to solve the problem of estimating frequency-varying RVS with small samples. Firstly, the estimated indexes are obtained including the estimated interval, the estimated uncertainty, the estimated value, the estimated error and estimated reliability. In addition, GBM is applied to estimating the single flight testing of certain aircraft. At last, in order to evaluate the estimated performance, GBM is compared with bootstrap method (BM and gray method (GM in testing analysis. The result shows that GBM has superiority for estimating dynamic signals with small samples and estimated reliability is proved to be 100% at the given confidence level.
An Enhanced Random Vibration and Fatigue Model for Printed Circuit Boards
Directory of Open Access Journals (Sweden)
Bruno de Castro Braz
Full Text Available Abstract Aerospace vehicles are mostly exposed to random vibration loads during its operational lifetime. These harsh conditions excites vibration responses in the vehicles printed circuit boards, what can cause failure on mission functionality due to fatigue damage of electronic components. A novel analytical model to evaluate the useful life of embedded electronic components (capacitors, chips, oscillators etc. mounted on Printed Circuit Boards (PCB is presented. The fatigue damage predictions are calculated by the relative displacement between the PCB and the component, the lead stiffness, as well the natural vibration modes of the PCB and the component itself. Statistical methods are used for fatigue cycle counting. The model is applied to experimental fatigue tests of PCBs available on literature. The analytical results are of the same magnitude order of the experimental findings.
Greulich, Timm; Nell, Christoph; Koepke, Janine; Fechtel, Juliane; Franke, Maja; Schmeck, Bernd; Haid, Daniel; Apelt, Sandra; Filipovic, Silke; Kenn, Klaus; Janciauskiene, Sabina; Vogelmeier, Claus; Koczulla, Andreas Rembert
2014-04-11
Patients with stable COPD show improvements in exercise capacity and muscular function after the application of whole body vibration. We aimed to evaluate whether this modality added to conventional physiotherapy in exacerbated hospitalised COPD patients would be safe and would improve exercise capacity and quality of life. 49 hospitalised exacerbated COPD patients were randomized (1:1) to undergo physiotherapy alone or physiotherapy with the addition of whole body vibration. The primary endpoint was the between-group difference of the 6-minute walking test (day of discharge - day of admission). Secondary assessments included chair rising test, quality of life, and serum marker analysis. Whole body vibration did not cause procedure-related adverse events. Compared to physiotherapy alone, it led to significantly stronger improvements in 6-minute walking test (95.55 ± 76.29 m vs. 6.13 ± 81.65 m; p = 0.007) and St. Georges Respiratory Questionnaire (-6.43 ± 14.25 vs. 5.59 ± 19.15, p = 0.049). Whole body vibration increased the expression of the transcription factor peroxisome proliferator receptor gamma coactivator-1-α and serum levels of irisin, while it decreased serum interleukin-8. Whole body vibration during hospitalised exacerbations did not cause procedure-related adverse events and induced clinically significant benefits regarding exercise capacity and health-related quality of life that were associated with increased serum levels of irisin, a marker of muscle activity. German Clinical Trials Register DRKS00005979. Registered 17 March 2014.
Vibrational spectra of four-coordinated random networks with periodic boundary conditions
International Nuclear Information System (INIS)
Guttman, L.
1976-01-01
Examples of perfectly four-coordinated networks satisfying periodic boundary conditions are constructed by a pseudo-random process, starting from a crystalline region. The unphysical features (high density, large deviations from the tetrahedral bond-angle) are removed by systematic modification of the bonding scheme. The vibrational spectra are calculated, using a valence-force potential, and the neutron scattering is computed by a phonon-expansion approximation
Ji, Xiaoxu; Eger, Tammy R; Dickey, James P
2017-03-01
Seats and cushions can attenuate whole-body vibration (WBV) exposures and minimize health risks for heavy machine operators. We successfully developed neural network (NN) algorithms to identify the vibration attenuation properties for four different seating conditions (seat/cushion combinations), and implemented each of the NN models to predict the equivalent daily exposure A(8) values for various vehicles in the forestry and mining environments. We also evaluated the performance of the new prototype No-Jolt™ air-inflated cushion and the original cushion of each seat with jolt exposures. We observed that the air cushion significantly improved the vibration attenuation properties of the seat that initially had good performance, but not for the seat that had relatively poor vibration attenuation properties. In addition, operator's anthropometrics and sex influenced the performance of the air-inflated cushion when the vibration environment included jolt exposures. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
Chambers, Jeffrey A.
1994-01-01
Finite element analysis is regularly used during the engineering cycle of mechanical systems to predict the response to static, thermal, and dynamic loads. The finite element model (FEM) used to represent the system is often correlated with physical test results to determine the validity of analytical results provided. Results from dynamic testing provide one means for performing this correlation. One of the most common methods of measuring accuracy is by classical modal testing, whereby vibratory mode shapes are compared to mode shapes provided by finite element analysis. The degree of correlation between the test and analytical mode shapes can be shown mathematically using the cross orthogonality check. A great deal of time and effort can be exhausted in generating the set of test acquired mode shapes needed for the cross orthogonality check. In most situations response data from vibration tests are digitally processed to generate the mode shapes from a combination of modal parameters, forcing functions, and recorded response data. An alternate method is proposed in which the same correlation of analytical and test acquired mode shapes can be achieved without conducting the modal survey. Instead a procedure is detailed in which a minimum of test information, specifically the acceleration response data from a random vibration test, is used to generate a set of equivalent local accelerations to be applied to the reduced analytical model at discrete points corresponding to the test measurement locations. The static solution of the analytical model then produces a set of deformations that once normalized can be used to represent the test acquired mode shapes in the cross orthogonality relation. The method proposed has been shown to provide accurate results for both a simple analytical model as well as a complex space flight structure.
1977-09-01
procedure previously described cannot be K’. 1,. , .L" - Initialize ..’.:_"....- _-’ __- array IRAN ( NLINE = number of . . Pseudo- spectral lines) IRAN(K...random---- Inumber " ..-. ’.: •.-.-. 1 , NACT ...-- T - • - - Convert to complex K 1 , NLINE and randot..ize the phase of each spectral line of the...sensitivity and calibration while installed in the test set-up. THE COMPONENTS OF THE SYSTEM.- There is available on the market , a photo- - diode which
Vibrations in the urban environment controlling 222Rn migration in soils
International Nuclear Information System (INIS)
Wiegand, J.
1998-01-01
Comparable to investigations looking for a connection of 222 Rn and earthquakes, this study shows the influence of subsurface vibrations on the 222 Rn concentration of the soil-gas in urban environments. Generally, the 222 Rn concentration increases through vibrations induced by trains, street-traffic and activities at project sites. The spatial radius of the 222 Rn increase due to vibrations reach highest values at project sites where piled foundations or metal panels are rammed into the ground (> 60 m). Along railway tracks the radius is wider (> 30 m) than along heavy traffic roads ( 222 Rn concentrations in soil-gas due to vibrations is the highest at project sites (53%). Along heavy traffic roads the increase of 222 Rn concentrations by motor vehicle traffic is higher (37%) than that by railway traffic (11.5%). The maximum increase of 400% was observed in a distance of 1 m from a railway track. In the vicinity of railway tracks a difference of the vibration influence according to unconsolidated rock (11.1%) or solid rock (11.8%) was not noticed. Beside this vibration effect, the overall 222 Rn level decreases with increasing distance to the vibration source, but only at locations laying above solid rocks. The observation of the increase of 222 Rn concentrations can be explained by a 'pump effect': the mechanical vibration of soil and mineral particles leads to an upward motion of the whole volume of soil-gas. Therefore, 222 Rn is pumped out of the soil to the atmosphere and as a result the upward transport is increased. (author)
Pain control in orthodontics using a micropulse vibration device: A randomized clinical trial.
Lobre, Wendy D; Callegari, Brent J; Gardner, Gary; Marsh, Curtis M; Bush, Anneke C; Dunn, William J
2016-07-01
To investigate the relationship between a micropulse vibration device and pain perception during orthodontic treatment. This study was a parallel group, randomized clinical trial. A total of 58 patients meeting eligibility criteria were assigned using block allocation to one of two groups: an experimental group using the vibration device or a control group (n = 29 for each group). Patients used the device for 20 minutes daily. Patients rated pain intensity on a visual analog scale at appropriate intervals during the weeks after the separator or archwire appointment. Data were analyzed using repeated measures analysis of variance at α = .05. During the 4-month test period, significant differences between the micropulse vibration device group and the control group for overall pain (P = .002) and biting pain (P = .003) were identified. The authors observed that perceived pain was highest at the beginning of the month, following archwire adjustment. The micropulse vibration device significantly lowered the pain scores for overall pain and biting pain during the 4-month study period.
Random Vibration and Dynamic Analysis of a Planetary Gear Train in a Wind Turbine
Directory of Open Access Journals (Sweden)
Jianming Yang
2016-01-01
Full Text Available Premature failure of gearboxes is a big challenge facing the wind power industry. It highly depends on fully understanding the embedded dynamics to solve this problem. To this end, this paper investigates the random vibration and dynamics of planetary gear trains (PGTs in wind turbines under the excitation of wind turbulence. The turbulence is represented by the Von Karmon spectrum and implemented by passing white noise through a 2nd-order shaping filter. Then, extra equations are formed and added to the original governing equations of motion. With this augmented equation set, a recursive numerical algorithm based on stochastic Newmark scheme is applied to solve for the statistics of the responses starting from initial conditions. After simulation, the variances of the vibration responses and the dynamic meshing forces at gear meshes are obtained.
Random vibration sensitivity studies of modeling uncertainties in the NIF structures
International Nuclear Information System (INIS)
Swensen, E.A.; Farrar, C.R.; Barron, A.A.; Cornwell, P.
1996-01-01
The National Ignition Facility is a laser fusion project that will provide an above-ground experimental capability for nuclear weapons effects simulation. This facility will achieve fusion ignition utilizing solid-state lasers as the energy driver. The facility will cover an estimated 33,400 m 2 at an average height of 5--6 stories. Within this complex, a number of beam transport structures will be houses that will deliver the laser beams to the target area within a 50 microm ms radius of the target center. The beam transport structures are approximately 23 m long and reach approximately heights of 2--3 stories. Low-level ambient random vibrations are one of the primary concerns currently controlling the design of these structures. Low level ambient vibrations, 10 -10 g 2 /Hz over a frequency range of 1 to 200 Hz, are assumed to be present during all facility operations. Each structure described in this paper will be required to achieve and maintain 0.6 microrad ms laser beam pointing stability for a minimum of 2 hours under these vibration levels. To date, finite element (FE) analysis has been performed on a number of the beam transport structures. Certain assumptions have to be made regarding structural uncertainties in the FE models. These uncertainties consist of damping values for concrete and steel, compliance within bolted and welded joints, and assumptions regarding the phase coherence of ground motion components. In this paper, the influence of these structural uncertainties on the predicted pointing stability of the beam line transport structures as determined by random vibration analysis will be discussed
Directory of Open Access Journals (Sweden)
Wang Wei
2016-01-01
Full Text Available The related theory and algorithm of adaptive inverse control were presented through the research which pointed out the adaptive inverse control strategy could effectively eliminate the noise influence on the system control. Proposed using a frequency domain filter-X LMS adaptive inverse control algorithm, and the control algorithm was applied to the two-exciter hydraulic vibration test system of random shock vibration control process and summarized the process of the adaptive inverse control strategies in the realization of the random shock vibration test. The self-closed-loop and field test show that using the frequency-domain filter-X LMS adaptive inverse control algorithm can realize high precision control of random shock vibration test.
Random vibration tests of the anticoincidence system of the PAMELA satellite experiment
Pearce, M; Lundin, M; Lundqvist, J M
2002-01-01
PAMELA is a general purpose cosmic ray satellite experiment which will be launched early in 2003. An anticoincidence system surrounds the PAMELA silicon tracker to reject particles not clearly entering the acceptance of the experiment. The engineering model of the PAMELA anticounter system uses plastic scintillator which is read out by Hamamatsu R5900U photomultipliers. The anticounters have been subjected to the random vibration spectrum expected during the launch of PAMELA. The integrated amplitude experienced by the photomultipliers was O(20) g RMS. No degradation to the photomultiplier operation or mechanical assembly was observed.
Stark, C.; Herkenrath, P.; Hollmann, H.; Waltz, S.; Becker, I.; Hoebing, L.; Semler, O.; Hoyer-Kuhn, H.; Duran, I.; Hero, B.; Hadders-Algra, M.; Schoenau, E.
2016-01-01
Objectives: to investigate feasibility, safety and efficacy of home-based side-alternating whole body vibration (sWBV) to improve motor function in toddlers with cerebral palsy (CP). Methods: Randomized controlled trial including 24 toddlers with CP (mean age 19 months (SD?3.1); 13 boys). Intervention: 14 weeks sWBV with ten 9-minute sessions weekly (non-individualized). Group A started with sWBV, followed by 14 weeks without; in group B this order was reversed. Feasibility (?70% adherence) a...
Another Look at the Draft Mil-Std-1540E Unit Random Vibration Test Requirements
Perl, E.; Peterson, A. J..; Davis, D.
2012-07-01
The draft Mil-Std-1540E has been updated to reflect lessons learned since its publication as an SMC Standard in 2008, [1], and an earlier Aerospace Corporation Technical Report released in 2006, [2]. This paper discusses the technical rationale supporting some of the unit random vibration test requirements to provide better insight into their derivation and application to programs. It is intended that these requirements be tailored for each program to reflect the customer risk profile. Several tailoring options are provided and a two phase test strategy is discussed to highlight its applicability to utilizing heritage hardware in new applications.
Shock and vibration environments for large shipping containers on rail cars and trucks
International Nuclear Information System (INIS)
Magnuson, C.F.; Wilson, L.T.
1977-06-01
The purpose of this study was to provide definitions of shock and vibration environment to which fissile material shipping containers may be exposed during normal shipment by truck and rail cars. The definitions of vibration, shock superimposed on vibration and rail coupling shock result from existing data. The dependence of shock environment, from rail coupling operations, on parameters like cargo weight and shock attenuation couplers was also studied using spring-mass models. These studies show that for rail cars equipped with standard draft gear, the cargo response decreases with increased cargo weight until the springs bottom out. For rail cars equipped with shock attenuation couplers, cargo weight has little effect on cargo response. The study also shows the importance of matching couplers and tiedown stiffnesses to decrease the cargo response. Vibration and shock data samples have been obtained during truck shipment of heavy cargo and the data will be presented in subsequent reports. Similar data need to be obtained for rail shipment of heavy cargo and during rail coupling operations with heavy cargo
Cooperation evolution in random multiplicative environments
Yaari, G.; Solomon, S.
2010-02-01
Most real life systems have a random component: the multitude of endogenous and exogenous factors influencing them result in stochastic fluctuations of the parameters determining their dynamics. These empirical systems are in many cases subject to noise of multiplicative nature. The special properties of multiplicative noise as opposed to additive noise have been noticed for a long while. Even though apparently and formally the difference between free additive vs. multiplicative random walks consists in just a move from normal to log-normal distributions, in practice the implications are much more far reaching. While in an additive context the emergence and survival of cooperation requires special conditions (especially some level of reward, punishment, reciprocity), we find that in the multiplicative random context the emergence of cooperation is much more natural and effective. We study the various implications of this observation and its applications in various contexts.
Doppler Spectrum from Moving Scatterers in a Random Environment
DEFF Research Database (Denmark)
Andersen, Jørgen Bach; Nielsen, Jesper Ødum; Pedersen, Gert Frølund
2009-01-01
A random non-line-of-sight environment with stationary transmitter and receiver is considered. In such an environment movement of a scatterer will lead to perturbations of the otherwise static channel with a resulting Doppler spectrum. This is quite a general situation in outdoor environments wit...
A novel vision-based mold monitoring system in an environment of intense vibration
International Nuclear Information System (INIS)
Hu, Fen; He, Zaixing; Zhao, Xinyue; Zhang, Shuyou
2017-01-01
Mold monitoring has been more and more widely used in the modern manufacturing industry, especially when based on machine vision, but these systems cannot meet the detection speed and accuracy requirements for mold monitoring because they must operate in environments that exhibit intense vibration during production. To ensure that the system runs accurately and efficiently, we propose a new descriptor that combines the geometric relationship-based global context feature and the local scale-invariant feature transform for the image registration step of the mold monitoring system. The experimental results of four types of molds showed that the detection accuracy of the mold monitoring system is improved in the environment with intense vibration. (paper)
A novel vision-based mold monitoring system in an environment of intense vibration
Hu, Fen; He, Zaixing; Zhao, Xinyue; Zhang, Shuyou
2017-10-01
Mold monitoring has been more and more widely used in the modern manufacturing industry, especially when based on machine vision, but these systems cannot meet the detection speed and accuracy requirements for mold monitoring because they must operate in environments that exhibit intense vibration during production. To ensure that the system runs accurately and efficiently, we propose a new descriptor that combines the geometric relationship-based global context feature and the local scale-invariant feature transform for the image registration step of the mold monitoring system. The experimental results of four types of molds showed that the detection accuracy of the mold monitoring system is improved in the environment with intense vibration.
DEFF Research Database (Denmark)
Liang, Shanshan; Crovetto, Andrea; Peng, Zhuoteng
2016-01-01
and experiments with piezoelectric elements show that the energy harvesting device with the bi-resonant structure can generate higher power output than that of the sum of the two separate devices from random vibration sources at low frequency, and hence significantly improves the vibration-to- electricity......This paper reports on a bi-resonant structure of piezoelectric PVDF films energy harvester (PPEH), which consists of two cantilevers with resonant frequencies of 15 Hz and 22 Hz. With increased acceleration, the vibration amplitudes of the two cantilever-mass structures are increased and collision...
Yu, Zhi-wu; Mao, Jian-feng; Guo, Feng-qi; Guo, Wei
2016-03-01
Rail irregularity is one of the main sources causing train-bridge random vibration. A new random vibration theory for the coupled train-bridge systems is proposed in this paper. First, number theory method (NTM) with 2N-dimensional vectors for the stochastic harmonic function (SHF) of rail irregularity power spectrum density was adopted to determine the representative points of spatial frequencies and phases to generate the random rail irregularity samples, and the non-stationary rail irregularity samples were modulated with the slowly varying function. Second, the probability density evolution method (PDEM) was employed to calculate the random dynamic vibration of the three-dimensional (3D) train-bridge system by a program compiled on the MATLAB® software platform. Eventually, the Newmark-β integration method and double edge difference method of total variation diminishing (TVD) format were adopted to obtain the mean value curve, the standard deviation curve and the time-history probability density information of responses. A case study was presented in which the ICE-3 train travels on a three-span simply-supported high-speed railway bridge with excitation of random rail irregularity. The results showed that compared to the Monte Carlo simulation, the PDEM has higher computational efficiency for the same accuracy, i.e., an improvement by 1-2 orders of magnitude. Additionally, the influences of rail irregularity and train speed on the random vibration of the coupled train-bridge system were discussed.
The biennial life strategy in a random environment
Roerdink, J.B.T.M.
1988-01-01
A discrete-time population model with two age classes is studied which describes the growth of biennial plants in a randomly varying environment. A fraction of the oldest age class delays its flowering each year. The solution of the model involves products of random matrices. We calculate the exact
On the nature of intramolecular vibrational energy transfer in dense molecular environments
Energy Technology Data Exchange (ETDEWEB)
Benten, Rebekka S. von [Institut fuer Physikalische Chemie der Universitaet Goettingen, Tammannstrasse 6, D-37077 Goettingen (Germany); Abel, Bernd, E-mail: Bernd.Abel@uni-lepzig.de [Wilhelm-Ostwald-Institut fuer Physikalische und Theoretische Chemie, Universitaet Leipzig, Linne-Strasse 2, D-04103 Leipzig (Germany)
2010-12-09
Graphical abstract: Mechanisms of IVR in multi-tiers of intramolecular energy levels in different molecular environments are investigated. - Abstract: Transient femtosecond-IR-pump-UV-absorption probe-spectroscopy has been employed to shed light on the nature of intramolecular vibrational energy transfer (IVR) in dense molecular environments ranging from the diluted gas phase to the liquid. A general feature in our experiments and those of others is that IVR proceeds via multiple timescales if overtones or combination vibrations of high frequency modes are excited. It has been found that collisions enhance IVR if its (slower) timescales can compete with collisions. This enhancement is, however, much more weaker and rather inefficient as opposed to the effect of collisions on intermolecular energy transfer which is well known. In a series of experiments we found that IVR depends not significantly on the average energy transferred in a collision but rather on the number of collisions. The collisions are much less efficient in affecting IVR than VET. We conclude that collision induced broadening of vibrational energy levels reduces the energy gaps and enhances existing couplings between tiers. The present results are an important step forward to rationalize and understand apparently different and not consistent results from different groups on different molecular systems between gas and liquid phases.
Approximations to the Probability of Failure in Random Vibration by Integral Equation Methods
DEFF Research Database (Denmark)
Nielsen, Søren R.K.; Sørensen, John Dalsgaard
Close approximations to the first passage probability of failure in random vibration can be obtained by integral equation methods. A simple relation exists between the first passage probability density function and the distribution function for the time interval spent below a barrier before...... passage probability density. The results of the theory agree well with simulation results for narrow banded processes dominated by a single frequency, as well as for bimodal processes with 2 dominating frequencies in the structural response....... outcrossing. An integral equation for the probability density function of the time interval is formulated, and adequate approximations for the kernel are suggested. The kernel approximation results in approximate solutions for the probability density function of the time interval, and hence for the first...
Muravyov, Alexander A.
1999-01-01
In this paper, a method for obtaining nonlinear stiffness coefficients in modal coordinates for geometrically nonlinear finite-element models is developed. The method requires application of a finite-element program with a geometrically non- linear static capability. The MSC/NASTRAN code is employed for this purpose. The equations of motion of a MDOF system are formulated in modal coordinates. A set of linear eigenvectors is used to approximate the solution of the nonlinear problem. The random vibration problem of the MDOF nonlinear system is then considered. The solutions obtained by application of two different versions of a stochastic linearization technique are compared with linear and exact (analytical) solutions in terms of root-mean-square (RMS) displacements and strains for a beam structure.
Application of empirical mode decomposition method for characterization of random vibration signals
Directory of Open Access Journals (Sweden)
Setyamartana Parman
2016-07-01
Full Text Available Characterization of finite measured signals is a great of importance in dynamical modeling and system identification. This paper addresses an approach for characterization of measured random vibration signals where the approach rests on a method called empirical mode decomposition (EMD. The applicability of proposed approach is tested in one numerical and experimental data from a structural system, namely spar platform. The results are three main signal components, comprising: noise embedded in the measured signal as the first component, first intrinsic mode function (IMF called as the wave frequency response (WFR as the second component and second IMF called as the low frequency response (LFR as the third component while the residue is the trend. Band-pass filter (BPF method is taken as benchmark for the results obtained from EMD method.
Shock and vibration environments for a large shipping container during truck transport (Part II)
International Nuclear Information System (INIS)
Magnuson, C.E.
1978-05-01
Purpose of this study was to obtain vibration and shock data during truck shipment of heavy cargo. These data were for use in determining any trends of vibration and shock environments with increased cargo weight. The new data were obtained on a ''piggyback'' basis during truck transport of 249 100N (56,000-pound) cargo which consisted of a spent fuel container and its supporting structure. The truck was driven from Mercury, Nevada, to Albuquerque, New Mexico. The routes traveled were US 95 from Mercury, Nevada, to Las Vegas, Nevada; US 93 from Las Vegas to Kingman, Arizona; and I-40/US 66 from Kingman to Albuquerque, New Mexico. Speeds varied from very slow to 88 km/hr (55 mph). A comparison of data from similar experiments with cargo weights varying from no-load to this load shows that the zero-to-peak acceleration amplitude levels of vibration are highest when trucks carry relatively light loads. This is true for the longitudinal and vertical axes of the vehicles in most frequency bands and for the transverse axis above 700 Hz. The shock response acceleration amplitudes for heavier cargo weights were less severe above 3 Hz in the vertical axis and higher between 8 and 20 Hz in the transverse axis. The highest acceleration amplitude of shock response in the longitudinal axis below about 20 Hz was produced in a trailer having a spring suspension system and carrying the 249 100N (56,000 pounds) load
Energy Technology Data Exchange (ETDEWEB)
Wong-McSweeney, D., E-mail: D.B.C.WongMcSweeney@salford.ac.uk [Acoustics Research Centre, University of Salford, Salford M5 4TW (United Kingdom); Woodcock, J.S.; Peris, E.; Waddington, D.C.; Moorhouse, A.T. [Acoustics Research Centre, University of Salford, Salford M5 4TW (United Kingdom); Redel-Macías, M.D. [Dep. Rural Engineering Campus de Rabanales, University of Córdoba, Córdoba (Spain)
2016-10-15
The aim of this paper is to investigate the use of different self-reported measures for assessing the human response to environmental vibration from the construction of an urban LRT (Light Rapid Transit) system. The human response to environmental stressors such as vibration and noise is often expressed in terms of exposure–response relationships that describe annoyance as a function of the magnitude of the vibration. These relationships are often the basis of noise and vibration policy and the setting of limit values. This paper examines measures other than annoyance by expressing exposure–response relationships for vibration in terms of self-reported concern about property damage and acceptability. The exposure–response relationships for concern about property damage and for acceptability are then compared with those for annoyance. It is shown that concern about property damage occurs at vibration levels well below those where there is any risk of damage. Earlier research indicated that concern for damage is an important moderator of the annoyance induced. Acceptability, on the other hand, might be influenced by both annoyance and concern, as well as by other considerations. It is concluded that exposure–response relationships expressing acceptability as a function of vibration exposure could usefully complement existing relationships for annoyance in future policy decisions regarding environmental vibration. The results presented in this paper are derived from data collected through a socio-vibration survey (N = 321) conducted for the construction of an urban LRT in the United Kingdom. - Highlights: • The human response to construction vibration is assessed in residential environments. • Exposure–response relationships are generated based on survey and semi-empirical vibration estimation. • Annoyance, concern and acceptability are compared as response measures. • Concern and acceptability are viable measures complementing annoyance.
Brogårdh, Christina; Flansbjer, Ulla-Britt; Lexell, Jan
2012-02-01
To evaluate the effects of whole-body vibration (WBV) training in individuals after stroke. A double-blind randomized controlled study with assessments pre- and posttraining. A university hospital rehabilitation department. Participants (N=31; mean age ± SD, 62±7 y; 6-101 mo poststroke) were randomized to an intervention group or a control group. Supervised WBV training (2 sessions/wk for 6wk; 12 repetitions of 40-60s WBV per session). The intervention group trained on a vibrating platform with a conventional amplitude (3.75 mm) and the control group on a "placebo" vibrating platform (0.2mm amplitude); the frequency was 25Hz on both platforms. All participants and examiners were blinded to the amplitudes of the 2 platforms. Primary outcome measures were isokinetic and isometric knee muscle strength (dynamometer). Secondary outcome measures were balance (Berg Balance Scale), muscle tone (Modified Ashworth Scale), gait performance (Timed Up & Go, comfortable gait speed, fast gait speed, and six-minute walk tests), and perceived participation (Stroke Impact Scale). There were no significant differences between the 2 groups after the WBV training. Significant but small improvements (Pnormative variation. Six weeks of WBV training on a vibration platform with conventional amplitude was not more efficient than a placebo vibrating platform. Therefore, the use of WBV training in individuals with chronic stroke and mild to moderate disability is not supported. Copyright © 2012 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
Ferebee, R. C.
1982-01-01
A computerized data bank system was developed for utilization of large amounts of vibration and acoustic data to formulate component random vibration design and test criteria. This system consists of a computer, graphics tablet, and a dry-silver hard copier which are all desk-top type hardware and occupy minimal space. The data bank contains data from the Saturn V and Titan III flight and static test programs. The vibration and acoustic data are stored in the form of power spectral density and one-third octave band plots over the frequency range from 20 to 2000 Hz. The data was stored by digitizing each spectral plot by tracing with the graphics tablet. The digitized data was statistically analyzed and the resulting 97.5% probability levels were stored on tape along with the appropriate structural parameters. Standard extrapolation procedures were programmed for prediction of component random vibration test criteria for new launch vehicle and payload configurations. This automated vibroacoustic data bank system greatly enhances the speed and accuracy of formulating vibration test criteria. In the future, the data bank will be expanded to include all data acquired from the space shuttle flight test program.
Damage Detection in Bridge Structure Using Vibration Data under Random Travelling Vehicle Loads
International Nuclear Information System (INIS)
Loh, C H; Hung, T Y; Chen, S F; Hsu, W T
2015-01-01
Due to the random nature of the road excitation and the inherent uncertainties in bridge-vehicle system, damage identification of bridge structure through continuous monitoring under operating situation become a challenge problem. Methods for system identification and damage detection of a continuous two-span concrete bridge structure in time domain is presented using interaction forces from random moving vehicles as excitation. The signals recorded in different locations of the instrumented bridge are mixed with signals from different internal and external (road roughness) vibration sources. The damage structure is also modelled as the stiffness reduction in one of the beam element. For the purpose of system identification and damage detection three different output-only modal analysis techniques are proposed: The covariance-driven stochastic subspace identification (SSI-COV), the blind source separation algorithms (called Second Order Blind Identification) and the multivariate AR model. The advantages and disadvantages of the three algorithms are discussed. Finally, the null-space damage index, subspace damage indices and mode shape slope change are used to detect and locate the damage. The proposed approaches has been tested in simulation and proved to be effective for structural health monitoring. (paper)
International Nuclear Information System (INIS)
Qing, Xinlin P; Beard, Shawn J; Kumar, Amrita; Sullivan, Kevin; Aguilar, Robert; Merchant, Munir; Taniguchi, Mike
2008-01-01
A series of tests have been conducted to determine the survivability and functionality of a piezoelectric-sensor-based active structural health monitoring (SHM) SMART Tape system under the operating conditions of typical liquid rocket engines such as cryogenic temperature and vibration loads. The performance of different piezoelectric sensors and a low temperature adhesive under cryogenic temperature was first investigated. The active SHM system for liquid rocket engines was exposed to flight vibration and shock environments on a simulated large booster LOX-H 2 engine propellant duct conditioned to cryogenic temperatures to evaluate the physical robustness of the built-in sensor network as well as operational survivability and functionality. Test results demonstrated that the developed SMART Tape system can withstand operational levels of vibration and shock energy on a representative rocket engine duct assembly, and is functional under the combined cryogenic temperature and vibration environment
Random regression models for detection of gene by environment interaction
Directory of Open Access Journals (Sweden)
Meuwissen Theo HE
2007-02-01
Full Text Available Abstract Two random regression models, where the effect of a putative QTL was regressed on an environmental gradient, are described. The first model estimates the correlation between intercept and slope of the random regression, while the other model restricts this correlation to 1 or -1, which is expected under a bi-allelic QTL model. The random regression models were compared to a model assuming no gene by environment interactions. The comparison was done with regards to the models ability to detect QTL, to position them accurately and to detect possible QTL by environment interactions. A simulation study based on a granddaughter design was conducted, and QTL were assumed, either by assigning an effect independent of the environment or as a linear function of a simulated environmental gradient. It was concluded that the random regression models were suitable for detection of QTL effects, in the presence and absence of interactions with environmental gradients. Fixing the correlation between intercept and slope of the random regression had a positive effect on power when the QTL effects re-ranked between environments.
Directory of Open Access Journals (Sweden)
Ronghui ZHENG
2017-12-01
Full Text Available A control method for Multi-Input Multi-Output (MIMO non-Gaussian random vibration test with cross spectra consideration is proposed in the paper. The aim of the proposed control method is to replicate the specified references composed of auto spectral densities, cross spectral densities and kurtoses on the test article in the laboratory. It is found that the cross spectral densities will bring intractable coupling problems and induce difficulty for the control of the multi-output kurtoses. Hence, a sequential phase modification method is put forward to solve the coupling problems in multi-input multi-output non-Gaussian random vibration test. To achieve the specified responses, an improved zero memory nonlinear transformation is utilized first to modify the Fourier phases of the signals with sequential phase modification method to obtain one frame reference response signals which satisfy the reference spectra and reference kurtoses. Then, an inverse system method is used in frequency domain to obtain the continuous stationary drive signals. At the same time, the matrix power control algorithm is utilized to control the spectra and kurtoses of the response signals further. At the end of the paper, a simulation example with a cantilever beam and a vibration shaker test are implemented and the results support the proposed method very well. Keywords: Cross spectra, Kurtosis control, Multi-input multi-output, Non-Gaussian, Random vibration test
Directory of Open Access Journals (Sweden)
Zhi-ping Zeng
2014-01-01
Full Text Available The paper describes the numerical simulation of the vertical random vibration of train-slab track-bridge interaction system by means of finite element method and pseudoexcitation method. Each vehicle is modeled as four-wheelset mass-spring-damper system with two-layer suspension systems. The rail, slab, and bridge girder are modeled by three-layer elastic Bernoulli-Euler beams connected with each other by spring and damper elements. The equations of motion for the entire system are derived according to energy principle. By regarding rail irregularity as a series of multipoint, different-phase random excitations, the random load vectors of the equations of motion are obtained by pseudoexcitation method. Taking a nine-span simply supported beam bridge traveled by a train consisting of 8 vehicles as an example, the vertical random vibration responses of the system are investigated. Firstly, the suitable number of discrete frequencies of rail irregularity is obtained by numerical experimentations. Secondly, the reliability and efficiency of pseudoexcitation method are verified through comparison with Monte Carlo method. Thirdly, the random vibration characteristics of train-slab track-bridge interaction system are analyzed by pseudoexcitation method. Finally, applying the 3σ rule for Gaussian stochastic process, the maximum responses of train-slab track-bridge interaction system with respect to various train speeds are studied.
International Nuclear Information System (INIS)
Granger, S.; Perotin, L.
1997-01-01
Maintaining the PWR components under reliable operating conditions requires a complex design to prevent various damaging processes, including fatigue and wear problems due to flow-induced vibration. In many practical situations, it is difficult, if not impossible, to perform direct measurements or calculations of the external forces acting on vibrating structures. Instead, vibrational responses can often be conveniently measured. This paper presents an inverse method for estimating a distributed random excitation from the measurement of the structural response at a number of discrete points. This paper is devoted to the presentation of the theoretical development. The force identification method is based on a modal model for the structure and a spatial orthonormal decomposition of the excitation field. The estimation of the Fourier coefficients of this orthonormal expansion is presented. As this problem turns out to be ill-posed, a regularization process is introduced. The minimization problem associated to this process is then formulated and its solutions is developed. (author)
Elfering, Achim; Schade, Volker; Stoecklin, Lukas; Baur, Simone; Burger, Christian; Radlinger, Lorenz
2014-05-01
Slip, trip, and fall injuries are frequent among health care workers. Stochastic resonance whole-body vibration training was tested to improve postural control. Participants included 124 employees of a Swiss university hospital. The randomized controlled trial included an experimental group given 8 weeks of training and a control group with no intervention. In both groups, postural control was assessed as mediolateral sway on a force plate before and after the 8-week trial. Mediolateral sway was significantly decreased by stochastic resonance whole-body vibration training in the experimental group but not in the control group that received no training (p < .05). Stochastic resonance whole-body vibration training is an option in the primary prevention of balance-related injury at work. Copyright 2014, SLACK Incorporated.
Energy Technology Data Exchange (ETDEWEB)
Farajpour, A., E-mail: ariobarzan.oderj@gmail.com; Rastgoo, A.; Mohammadi, M.
2017-03-15
Piezoelectric nanomaterials such as zinc oxide (ZnO) are of low toxicity and have many biomedical applications including optical imaging, drug delivery, biosensing and harvesting biomechanical energy using hybrid nanogenerators. In this paper, the vibration, buckling and smart control of microtubules (MTs) embedded in an elastic medium in thermal environment using a piezoelectric nanoshell (PNS) are investigated. The MT and PNS are considered to be coupled by a filament network. The PNS is subjected to thermal loads and an external electric voltage which operates to control the mechanical behavior of the MT. Using the nonlocal continuum mechanics, the governing differential equations are derived. An exact solution is presented for simply supported boundary conditions. The differential quadrature method is also used to solve the governing equations for other boundary conditions. A detailed parametric study is conducted to investigate the effects of the elastic constants of surrounding medium and internal filament matrix, scale coefficient, electric voltage, the radius-to-thickness ratio of PNSs and temperature change on the smart control of MTs. It is found that the applied electric voltage can be used as an effective controlling parameter for the vibration and buckling of MTs.
A bandwidth correction to the Allegri-Zhang solution for accelerated random vibration testing
Directory of Open Access Journals (Sweden)
Benasciutti Denis
2018-01-01
Full Text Available In 2008, Allegri and Zhang published a study [Int. J. Fatigue. 2008, 30(6:967-977] in which they provided an exact analytical solution to the inverse scaling law for accelerated vibration tests of linear systems submitted to stationary Gaussian excitations By combining finite element analysis with multiaxial spectral methods defined in the frequency-domain, their solution generalised the simple inverse power law model suggested in some standards. The solution adopted the “equivalent von Mises stress” multiaxial criterion combined with the narrow-band damage expression. This work aims to propose a bandwidth correction to the original Allegri-Zhang solution to account for the actual spectral banwidth of the local multiaxial stress. The corrected Allegri-Zhang solution is also extended to another multiaxial spectral method, namely the “Projection-by-Projection” criterion. A numerical example is finally discussed, in which the corrected solution is applied to an L-shaped beam submitted to random accelerations.
Fuzzy norm method for evaluating random vibration of airborne platform from limited PSD data
Directory of Open Access Journals (Sweden)
Wang Zhongyu
2014-12-01
Full Text Available For random vibration of airborne platform, the accurate evaluation is a key indicator to ensure normal operation of airborne equipment in flight. However, only limited power spectral density (PSD data can be obtained at the stage of flight test. Thus, those conventional evaluation methods cannot be employed when the distribution characteristics and priori information are unknown. In this paper, the fuzzy norm method (FNM is proposed which combines the advantages of fuzzy theory and norm theory. The proposed method can deeply dig system information from limited data, which probability distribution is not taken into account. Firstly, the FNM is employed to evaluate variable interval and expanded uncertainty from limited PSD data, and the performance of FNM is demonstrated by confidence level, reliability and computing accuracy of expanded uncertainty. In addition, the optimal fuzzy parameters are discussed to meet the requirements of aviation standards and metrological practice. Finally, computer simulation is used to prove the adaptability of FNM. Compared with statistical methods, FNM has superiority for evaluating expanded uncertainty from limited data. The results show that the reliability of calculation and evaluation is superior to 95%.
Stark, C; Herkenrath, P; Hollmann, H; Waltz, S; Becker, I; Hoebing, L; Semler, O; Hoyer-Kuhn, H; Duran, I; Hero, B; Hadders-Algra, M; Schoenau, E
2016-09-07
to investigate feasibility, safety and efficacy of home-based side-alternating whole body vibration (sWBV) to improve motor function in toddlers with cerebral palsy (CP). Randomized controlled trial including 24 toddlers with CP (mean age 19 months (SD±3.1); 13 boys). 14 weeks sWBV with ten 9-minute sessions weekly (non-individualized). Group A started with sWBV, followed by 14 weeks without; in group B this order was reversed. Feasibility (≥70% adherence) and adverse events were recorded; efficacy evaluated with the Gross Motor Function Measure (GMFM-66), Pediatric Evaluation of Disability Inventory (PEDI), at baseline (T0), 14 (T1) and 28 weeks (T2). Developmental change between T0 and T1 was similar in both groups; change scores in group A and B: GMFM-66 2.4 (SD±2.1) and 3.3 (SD±2.9) (p=0.412); PEDI mobility 8.4 (SD±6.6) and 3.5 (SD±9.2) (p=0.148), respectively. In two children muscle tone increased post-sWBV. 24 children received between 67 and 140 sWBV sessions, rate of completed sessions ranged from 48 to 100% and no dropouts were observed. A 14-week home-based sWBV intervention was feasible and safe in toddlers with CP, but was not associated with improvement in gross motor function.
National Research Council Canada - National Science Library
Colclough, Stephen
1998-01-01
The XM21 Decontaminant Pumper module of the Modular Decontamination System was analyzed using finite element analysis techniques to show why the first design iteration passed transportation vibration...
Energy Technology Data Exchange (ETDEWEB)
Malekzadeh, P., E-mail: p_malekz@yahoo.com [Department of Mechanical Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Fiouz, A.R.; Sobhrouyan, M. [Department of Civil Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of)
2012-01-15
A three-dimensional (3D) free vibration analysis of the functionally graded (FG) truncated conical shells subjected to thermal environment is presented. The material properties are assumed to be temperature-dependent and graded in the radius direction, which can vary according to a simple power law distribution. The initial thermal stresses are obtained accurately by solving the thermoelastic equilibrium equations and by considering the two-dimensional axisymmetric temperature distribution in the shell. The differential quadrature method (DQM) as an efficient and accurate numerical tool is adopted to solve the thermal and thermo-mechanical governing equations. For this purpose, a mapping technique is employed to transform the cross section of the shell into the computational domain of DQM. The convergence behavior of the method is numerically demonstrated and comparison studies with the available solutions in the literature are performed. The effects of temperature dependence of material properties, geometrical parameters, material graded index, thermal and mechanical boundary conditions on the frequency parameters of the FG truncated conical shells are carried out. - Highlights: Black-Right-Pointing-Pointer 3D free vibration analysis of the functionally graded truncated conical shells is presented. Black-Right-Pointing-Pointer Two-dimensional axisymmetric temperature distribution in the shell is assumed. Black-Right-Pointing-Pointer The material properties are assumed to be temperature-dependent. Black-Right-Pointing-Pointer Initial thermal stresses due to thermal environment are evaluated accurately and included. Black-Right-Pointing-Pointer Representing the effects of different parameters on the non-dimensional frequencies.
On reflexivity of random walks in a random environment on a metric space
International Nuclear Information System (INIS)
Rozikov, U.A.
2002-11-01
In this paper, we consider random walks in random environments on a countable metric space when jumps of the walks of the fractions are finite. The transfer probabilities of the random walk from x is an element of G (where G is the considering metric space) are defined by vector p(x) is an element of R k , k>1, where {p(x), x is an element of G} is the set of independent and indentically distributed random vectors. For the random walk, a sufficient condition of nonreflexivity is obtained. Examples for metric spaces Z d free groups and free product of finite numbers cyclic groups of the second order and some other metric spaces are considered. (author)
Polymer Chain Dynamics in a Random Environment: Heterogeneous Mobilities
International Nuclear Information System (INIS)
Niedzwiedz, K.; Wischnewski, A.; Monkenbusch, M.; Richter, D.; Strauch, M.; Straube, E.; Genix, A.-C.; Arbe, A.; Colmenero, J.
2007-01-01
We present a neutron scattering investigation on a miscible blend of two polymers with greatly different glass-transition temperatures T g . Under such conditions, the nearly frozen high-T g component imposes a random environment on the mobile chain. The results demand the consideration of a distribution of heterogeneous mobilities in the material and demonstrate that the larger scale dynamics of the fast component is not determined by the average local environment alone. This distribution of mobilities can be mapped quantitatively on the spectrum of local relaxation rates measured at high momentum transfers
Evolution of a Fluctuating Population in a Randomly Switching Environment.
Wienand, Karl; Frey, Erwin; Mobilia, Mauro
2017-10-13
Environment plays a fundamental role in the competition for resources, and hence in the evolution of populations. Here, we study a well-mixed, finite population consisting of two strains competing for the limited resources provided by an environment that randomly switches between states of abundance and scarcity. Assuming that one strain grows slightly faster than the other, we consider two scenarios-one of pure resource competition, and one in which one strain provides a public good-and investigate how environmental randomness (external noise) coupled to demographic (internal) noise determines the population's fixation properties and size distribution. By analytical means and simulations, we show that these coupled sources of noise can significantly enhance the fixation probability of the slower-growing species. We also show that the population size distribution can be unimodal, bimodal, or multimodal and undergoes noise-induced transitions between these regimes when the rate of switching matches the population's growth rate.
Continuous state branching processes in random environment: The Brownian case
Palau, Sandra; Pardo, Juan Carlos
2015-01-01
We consider continuous state branching processes that are perturbed by a Brownian motion. These processes are constructed as the unique strong solution of a stochastic differential equation. The long-term extinction and explosion behaviours are studied. In the stable case, the extinction and explosion probabilities are given explicitly. We find three regimes for the asymptotic behaviour of the explosion probability and, as in the case of branching processes in random environment, we find five...
Knight, Brent; Montgomery, Randall; Geist, David; Hunt, Ron; LaVerde, Bruce; Towner, Robert
2013-01-01
In a recent experimental study, small Particle Impact Dampers (PID) were bonded directly to the surface of printed circuit board (PCB) or printed wiring assemblies (PWA), reducing the random vibration response and increasing the fatigue life. This study provides data verifying practicality of this approach. The measured peak strain and acceleration response of the fundamental out of plane bending mode was significantly attenuated by adding a PID device. Attenuation of this mode is most relevant to the fatigue life of a PWA because the local relative displacements between the board and the supported components, which ultimately cause fatigue failures of the electrical leads of the board-mounted components are dominated by this mode. Applying PID damping at the board-level of assembly provides mitigation with a very small mass impact, especially as compared to isolation at an avionics box or shelf level of assembly. When compared with other mitigation techniques at the PWA level (board thickness, stiffeners, constrained layer damping), a compact PID device has the additional advantage of not needing to be an integral part of the design. A PID can simply be bonded to heritage or commercial off the shelf (COTS) hardware to facilitate its use in environments beyond which it was originally qualified. Finite element analysis and test results show that the beneficial effect is not localized and that the attenuation is not due to the simple addition of mass. No significant, detrimental reduction in frequency was observed. Side-by-side life testing of damped and un-damped boards at two different thicknesses (0.070" and 0.090") has shown that the addition of a PID was much more significant to the fatigue life than increasing the thickness. High speed video, accelerometer, and strain measurements have been collected to correlate with analytical results.
Directory of Open Access Journals (Sweden)
Masoud Ahmadi
2017-12-01
Full Text Available Nowadays, atomic-force microscopy plays a significant role in nanoscience and nanotechnology, and is widely used for direct measurement at atomic scale and scanning the sample surfaces. In tapping mode, the microcantilever of atomic-force microscope is excited at resonance frequency. Therefore, it is important to study its resonance. Moreover, atomic-force microscopes can be operated in fluid environments such as their applications in chemical and biological sensors. Additionally, piezoelectric microcantilevers are used to enhance atomic-force microscope scanning. Motivated by these considerations, presented herein is a finite element investigation into the nonlinear vibration behavior of piezoelectric microcantilever of atomic-force microscopes in fluid environment. For this purpose, a 3D finite element model coupled with a computational fluid dynamics model is introduced based upon a fluid-solid interaction analysis. First, the reliability of present fluid-solid interaction analysis is revealed by comparison with experimental data available in the literature. Then, numerical results are presented to study the influences of fluid dynamic viscosity and density on the resonance frequency, resonance amplitude and time response of piezoelectric microcantilever. It was shown that increasing the fluid density and dynamic viscosity results in the decrease of resonance frequency. For example, for density equal to 1000 kg/m3 , increasing the viscosity of fluid environment from 0.1 to 1, 10 and 20 mPa.s leads to decrease of resonance frequency about 3%, 29% and 42%, respectively. Also, the resonance amplitude of microcantilever increases as the density increases, while increasing dynamic viscosity has a decreasing effect on the resonance amplitude.
Lam, Freddy Mh; Chan, Philip Fl; Liao, L R; Woo, Jean; Hui, Elsie; Lai, Charles Wk; Kwok, Timothy Cy; Pang, Marco Yc
2018-04-01
To investigate whether a comprehensive exercise program was effective in improving physical function among institutionalized older adults and whether adding whole-body vibration to the program conferred additional therapeutic benefits. A single-blinded randomized controlled trial was conducted. This study was carried out in residential care units. In total, 73 older adults (40 women, mean age: 82.3 ± 7.3 years) were enrolled into this study. Participants were randomly allocated to one of the three groups: strength and balance program combined with whole-body vibration, strength and balance program without whole-body vibration, and social and recreational activities consisting of upper limb exercises only. All participants completed three training sessions per week for eight weeks. Assessment of mobility, balance, lower limb strength, walking endurance, and self-perceived balance confidence were conducted at baseline and immediately after the eight-week intervention. Incidences of falls requiring medical attention were recorded for one year after the end of the training period. A significant time × group interaction was found for lower limb strength (five-times-sit-to-stand test; P = 0.048), with the exercise-only group showing improvement (pretest: 35.8 ± 16.1 seconds; posttest: 29.0 ± 9.8 seconds), compared with a decline in strength among controls (pretest: 27.1 ± 10.4 seconds; posttest: 28.7 ± 12.3 seconds; P = 0.030). The exercise with whole-body vibration group had a significantly better outcome in balance confidence (pretest: 39.2 ± 29.0; posttest: 48.4 ± 30.6) than the exercise-only group (pretest: 35.9 ± 24.8; posttest: 38.2 ± 26.5; P = 0.033). The exercise program was effective in improving lower limb strength among institutionalized older adults but adding whole-body vibration did not enhance its effect. Whole-body vibration may improve balance confidence without enhancing actual balance performance.
Vibration and Acoustic Response of Rectangular Sandwich Plate under Thermal Environment
Directory of Open Access Journals (Sweden)
Yuan Liu
2013-01-01
Full Text Available In this paper, we focus on the vibration and acoustic response of a rectangular sandwich plate which is subjected to a concentrated harmonic force under thermal environment. The critical buckling temperature is obtained to decide the thermal load. The natural frequencies and modes as well as dynamic responses are acquired by using the analytical formulations based on equivalent non-classical theory, in which the effects of shear deformation and rotational inertia are taken into account. The rise of thermal load decreases the natural frequencies and moves response peaks to the low-frequency range. The specific features of sandwich plates with different formations are discussed subsequently. As the thickness ratio of facing to core increases, the natural frequencies are enlarged, and the response peaks float to the high-frequency region. Raising the Young's modulus of the core can cause the similar trends. The accuracy of the theoretical method is verified by comparing its results with those computed by the FEM/BEM.
Investigation of reactivity change and neutron noise due to random absorber vibrations. 2
International Nuclear Information System (INIS)
Barthel, R.
1984-01-01
Perturbations of the neutron flux due to stochastically excited vibrations of absorbers have been investigated using a one-dimensional core model with N pointlike absorbers. Taking into account the flux depressions near the absorbers, pronounced peaks in the spectral power densities of the flux fluctuations have been found at multiples of the resonance frequencies in addition to the direct imaging of the resonances of absorber vibrations. Investigation of the space dependence of the corresponding transfer functions has shown that a localization is possible by means of the double frequency effect and that the dispersion of absorber vibrations can be determined by using the triple frequency effect. The conclusions of the paper are qualitatively compared with results of noise measurements at a pressurized water reactor. (author)
Impact of the vibrations on the environment caused by passages of trains at variable speed
Directory of Open Access Journals (Sweden)
Kożuch Barbara
2016-01-01
Full Text Available The paper deals with negative environmental impact caused by the passages of different kinds of trains at variable speed. The study is based on the measurement results which took place in Poland in 2013 on the railway line no. 4. The effect of the traction unit – Pendolino (EMU 250 on the vibration climate was analysed. The impact of passages of new trains was compared to currently operated rolling stock. The speed of trains was varying between 40 and 250 km/h. Vibration measurements were conducted by stuff of an accredited Laboratory of Structural Mechanics at Cracow University of Technology (Accreditation No. AB 826. The influence of the indicated vibrations due to passages of the trains on the building in the neighbourhood of the line was investigated. The vibration assessment was done for horizontal components of vibrations according to Polish standard code. Assessment of environmental impact was presented by indicator of perceptibility of vibration through construction (WODB, which refers to the Scales of Dynamic Influences (SDI scales. The limits specified by standards in any of the passages have not been exceeded. The change of speed or rolling stock resulted in a change in the characteristic of the vibration spectrum.
Silva, Adriana Teresa; Dias, Miqueline Pivoto Faria; Calixto, Ruanito; Carone, Antonio Luis; Martinez, Beatriz Bertolaccini; Silva, Andreia Maria; Honorato, Donizeti Cesar
2014-04-01
The aim of this study was to investigate the acute effects of whole-body vibration on the motor function of patients with stroke. The present investigation was a randomized clinical trial studying 43 individuals with hemiparesis after stroke, with 33 subjects allocated to the intervention group and 10 subjects allocated to the control group. The intervention group was subjected to one session of vibration therapy (frequency of 50 Hz and amplitude of 2 mm) comprising four 1-min series with 1-min rest intervals between series in three body positions: bipedal stances with the knees flexed to 30 degrees and 90 degrees and a unipedal stance on the paretic limb. The analytical tests were as follows: simultaneous electromyography of the affected and unaffected tibialis anterior and rectus femoris muscles bilaterally in voluntary isometric contraction; the Six-Minute Walk Test; the Stair-Climb Test; and the Timed Get-Up-and-Go Test. The data were analyzed by independent and paired t tests and by analysis of covariance. There was no evidence of effects on the group and time interaction relative to variables affected side rectus femoris, unaffected side rectus femoris, affected side tibialis anterior, unaffected side tibialis anterior, and the Stair-Climb Test (P > 0.05). There was evidence of effects on the group interaction relative to variables Six-Minute Walk Test and Timed Get-Up-and-Go Test (P < 0.05). Whole-body vibration contributed little to improve the functional levels of stroke patients.
Fatigue damage from random vibration pulse process of tubular structural elements subject to wind
DEFF Research Database (Denmark)
Christensen, Claus F.; Ditlevsen, Ove Dalager
1997-01-01
In a wide range of the Reynolds number an elastically suspended circular cylinder surrounded by a homogeneous wind velocity field will generate vortex shedding of a frequency that by and large is proportional to the far field wind velocity. However, if the cylinder is free to vibrate, resonance w...
Marín, Pedro J; Ferrero, Cristina M; Menéndez, Héctor; Martín, Juan; Herrero, Azael J
2013-10-01
The aim of the present study was to analyze the effects of whole-body vibration on lower limb muscle architecture, muscle strength, and balance in stroke patients during a period of 3 mos. The inclusion criteria were having had ischemic or hemorrhagic stroke at least 6 mos before the study and a National Institutes of Health Stroke Scale score of greater than 1 and less than 20. The patients were randomly divided into two groups: an experimental group (n = 11, six men and five women; age, 62.4 ± 10.7 yrs; height, 1.64 ± 0.07 m; mass, 69.4 ± 12.9 kg) and a sham group (n = 9, five men and four women; age, 64.4 ± 7.6 yrs; height, 1.62 ± 0.07 m; mass, 75.0 ± 15.8 kg). The experimental group received a whole-body vibration treatment, with an increase in frequency, sets, and time per set during 17 sessions. The sham group performed the same exercises as that of the experimental group but was not exposed to vibration. Outcome variables included the muscle architecture (the rectus femoris, the vastus lateralis, and the medial gastrocnemius), the maximal isometric voluntary contraction of the knee extensors, and the Berg Balance Scale. There were no significant differences between the groups on the primary outcomes of lower limb muscle architecture, muscle strength, and balance. It seems that whole-body vibration exercise does not augment the increase in neuromuscular performance and lower limb muscle architecture induced by isometric exercise alone in stroke patients.
Powers, Anna; Scribano, Yohann; Lauvergnat, David; Mebe, Elsy; Benoit, David M; Bačić, Zlatko
2018-04-14
We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H 2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H 2 in the v=0 and v=1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H 2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H 2 inside a hydrate domain is assumed to be pairwise additive. The H 2 -H 2 O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H 2 , v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H 2 -H 2 O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H 2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H 2 change very little with the domain size, unlike the H 2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H 2 O molecules in the first three complete hydration shells around H 2 .
Powers, Anna; Scribano, Yohann; Lauvergnat, David; Mebe, Elsy; Benoit, David M.; Bačić, Zlatko
2018-04-01
We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v =0 and v =1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2-H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H2, v =0 or v =1 , is derived from the high-quality ab initio full-dimensional (9D) PES of the H2-H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.
Finite element random vibration method for soil-structure interaction analysis
International Nuclear Information System (INIS)
Romo-Organista, M.P.; Lysmer, J.; Seed, H.B.
1977-01-01
The authors present a method in which the seismic environment is defined directly in terms of the given design response spectrum. Response spectra cannot be used directly for random analysis, thus using extreme value theory a new procedure has been developed for converting the design response spectrum into a design power spectrum. This procedure is reversible and can also be used to compute response spectra the distribution of which can be expressed in terms of Confidence limits. Knowing the design power spctrum the resulting output power spectra and their statistical distribution can be computed by a response analysis of the soil-structure system in the frequency domain. Due to the complexity of soil structure systems, this is most conveniently done by the finite element method. Having obtained the power spectra for all motions in the system, these spectra can be used to determine other statistical information about the response such as maximum accelerations, stresses, bending moments, etc, all with appropriate confidence limits. This type of information is actually more useful for design than corresponding deterministic values. The authors have developed a computer program, PLUSH, which can perform the above procedures. Results obtained by the new method are in excellent agreement with the results of corresponding deterministic analysis. Furthermore, the probabilistic results can be obtained at a fraction of the cost of deterministic results
Human Activity Recognition in AAL Environments Using Random Projections
Directory of Open Access Journals (Sweden)
Robertas Damaševičius
2016-01-01
Full Text Available Automatic human activity recognition systems aim to capture the state of the user and its environment by exploiting heterogeneous sensors attached to the subject’s body and permit continuous monitoring of numerous physiological signals reflecting the state of human actions. Successful identification of human activities can be immensely useful in healthcare applications for Ambient Assisted Living (AAL, for automatic and intelligent activity monitoring systems developed for elderly and disabled people. In this paper, we propose the method for activity recognition and subject identification based on random projections from high-dimensional feature space to low-dimensional projection space, where the classes are separated using the Jaccard distance between probability density functions of projected data. Two HAR domain tasks are considered: activity identification and subject identification. The experimental results using the proposed method with Human Activity Dataset (HAD data are presented.
Human Activity Recognition in AAL Environments Using Random Projections.
Damaševičius, Robertas; Vasiljevas, Mindaugas; Šalkevičius, Justas; Woźniak, Marcin
2016-01-01
Automatic human activity recognition systems aim to capture the state of the user and its environment by exploiting heterogeneous sensors attached to the subject's body and permit continuous monitoring of numerous physiological signals reflecting the state of human actions. Successful identification of human activities can be immensely useful in healthcare applications for Ambient Assisted Living (AAL), for automatic and intelligent activity monitoring systems developed for elderly and disabled people. In this paper, we propose the method for activity recognition and subject identification based on random projections from high-dimensional feature space to low-dimensional projection space, where the classes are separated using the Jaccard distance between probability density functions of projected data. Two HAR domain tasks are considered: activity identification and subject identification. The experimental results using the proposed method with Human Activity Dataset (HAD) data are presented.
Random heteropolymers preserve protein function in foreign environments
Panganiban, Brian; Qiao, Baofu; Jiang, Tao; DelRe, Christopher; Obadia, Mona M.; Nguyen, Trung Dac; Smith, Anton A. A.; Hall, Aaron; Sit, Izaac; Crosby, Marquise G.; Dennis, Patrick B.; Drockenmuller, Eric; Olvera de la Cruz, Monica; Xu, Ting
2018-03-01
The successful incorporation of active proteins into synthetic polymers could lead to a new class of materials with functions found only in living systems. However, proteins rarely function under the conditions suitable for polymer processing. On the basis of an analysis of trends in protein sequences and characteristic chemical patterns on protein surfaces, we designed four-monomer random heteropolymers to mimic intrinsically disordered proteins for protein solubilization and stabilization in non-native environments. The heteropolymers, with optimized composition and statistical monomer distribution, enable cell-free synthesis of membrane proteins with proper protein folding for transport and enzyme-containing plastics for toxin bioremediation. Controlling the statistical monomer distribution in a heteropolymer, rather than the specific monomer sequence, affords a new strategy to interface with biological systems for protein-based biomaterials.
Localization of simulated damage on a steel beam from random vibrations
Czech Academy of Sciences Publication Activity Database
Bayer, Jan; Král, J.; Urushadze, Shota
2018-01-01
Roč. 62, č. 1 (2018), s. 112-116 ISSN 0553-6626 R&D Projects: GA ČR(CZ) GC17-26353J Institutional support: RVO:68378297 Keywords : damage localization * change of natural modes * flexibility matrix * flexibility curvatures * case study * damage detection * vibration monitoring Subject RIV: JM - Building Engineering OBOR OECD: Construction engineering, Municipal and structural engineering Impact factor: 0.313, year: 2016 https://pp.bme.hu/ci/ article /view/10625
The benefits of noise and nonlinearity: Extracting energy from random vibrations
Energy Technology Data Exchange (ETDEWEB)
Gammaitoni, Luca, E-mail: luca.gammaitoni@pg.infn.it [NiPS Laboratory, Universita di Perugia, I-06100 Perugia (Italy); Neri, Igor; Vocca, Helios [NiPS Laboratory, Universita di Perugia, I-06100 Perugia (Italy)
2010-10-05
Nonlinear behavior is the ordinary feature of the vast majority of dynamical systems and noise is commonly present in any finite temperature physical and chemical system. In this article we briefly review the potentially beneficial outcome of the interplay of noise and nonlinearity by addressing the novel field of vibration energy harvesting. The role of nonlinearity in a piezoelectric harvester oscillator dynamics is modeled with nonlinear stochastic differential equation.
Early, Derrick A.; Haile, William B.; Turczyn, Mark T.; Griffin, Thomas J. (Technical Monitor)
2001-01-01
NASA Goddard Space Flight Center and the European Space Agency (ESA) conducted a disturbance verification test on a flight Solar Array 3 (SA3) for the Hubble Space Telescope using the ESA Large Space Simulator (LSS) in Noordwijk, the Netherlands. The LSS cyclically illuminated the SA3 to simulate orbital temperature changes in a vacuum environment. Data acquisition systems measured signals from force transducers and accelerometers resulting from thermally induced vibrations of the SAI The LSS with its seismic mass boundary provided an excellent background environment for this test. This paper discusses the analysis performed on the measured transient SA3 responses and provides a summary of the results.
Evolution of the concentration PDF in random environments modeled by global random walk
Suciu, Nicolae; Vamos, Calin; Attinger, Sabine; Knabner, Peter
2013-04-01
The evolution of the probability density function (PDF) of concentrations of chemical species transported in random environments is often modeled by ensembles of notional particles. The particles move in physical space along stochastic-Lagrangian trajectories governed by Ito equations, with drift coefficients given by the local values of the resolved velocity field and diffusion coefficients obtained by stochastic or space-filtering upscaling procedures. A general model for the sub-grid mixing also can be formulated as a system of Ito equations solving for trajectories in the composition space. The PDF is finally estimated by the number of particles in space-concentration control volumes. In spite of their efficiency, Lagrangian approaches suffer from two severe limitations. Since the particle trajectories are constructed sequentially, the demanded computing resources increase linearly with the number of particles. Moreover, the need to gather particles at the center of computational cells to perform the mixing step and to estimate statistical parameters, as well as the interpolation of various terms to particle positions, inevitably produce numerical diffusion in either particle-mesh or grid-free particle methods. To overcome these limitations, we introduce a global random walk method to solve the system of Ito equations in physical and composition spaces, which models the evolution of the random concentration's PDF. The algorithm consists of a superposition on a regular lattice of many weak Euler schemes for the set of Ito equations. Since all particles starting from a site of the space-concentration lattice are spread in a single numerical procedure, one obtains PDF estimates at the lattice sites at computational costs comparable with those for solving the system of Ito equations associated to a single particle. The new method avoids the limitations concerning the number of particles in Lagrangian approaches, completely removes the numerical diffusion, and
Long-range epidemic spreading in a random environment.
Juhász, Róbert; Kovács, István A; Iglói, Ferenc
2015-03-01
Modeling long-range epidemic spreading in a random environment, we consider a quenched, disordered, d-dimensional contact process with infection rates decaying with distance as 1/rd+σ. We study the dynamical behavior of the model at and below the epidemic threshold by a variant of the strong-disorder renormalization-group method and by Monte Carlo simulations in one and two spatial dimensions. Starting from a single infected site, the average survival probability is found to decay as P(t)∼t-d/z up to multiplicative logarithmic corrections. Below the epidemic threshold, a Griffiths phase emerges, where the dynamical exponent z varies continuously with the control parameter and tends to zc=d+σ as the threshold is approached. At the threshold, the spatial extension of the infected cluster (in surviving trials) is found to grow as R(t)∼t1/zc with a multiplicative logarithmic correction and the average number of infected sites in surviving trials is found to increase as Ns(t)∼(lnt)χ with χ=2 in one dimension.
Filippi, Guido M; Brunetti, Orazio; Botti, Fabio M; Panichi, Roberto; Roscini, Mauro; Camerota, Filippo; Cesari, Matteo; Pettorossi, Vito E
2009-12-01
Filippi GM, Brunetti O, Botti FM, Panichi R, Roscini M, Camerota F, Cesari M, Pettorossi VE. Improvement of stance control and muscle performance induced by focal muscle vibration in young-elderly women: a randomized controlled trial. To determine the effect of a particular protocol of mechanical vibration, applied focally and repeatedly (repeated muscle vibration [rMV]) on the quadriceps muscles, on stance and lower-extremity muscle power of young-elderly women. Double-blind randomized controlled trial; 3-month follow-up after intervention. Human Physiology Laboratories, University of Perugia, Italy. Sedentary women volunteers (N=60), randomized in 3 groups (mean age +/- SD, 65.3+/-4.2y; range, 60-72). rMV (100Hz, 300-500microm, in three 10-minute sessions a day for 3 consecutive days) was applied to voluntary contracted quadriceps (vibrated and contracted group) and relaxed quadriceps (vibrated and relaxed group). A third group received placebo stimulation (nonvibrated group). Area of sway of the center of pressure, vertical jump height, and leg power. Twenty-four hours after the end of the complete series of applications, the area of sway of the center of pressure decreased significantly by approximately 20%, vertical jump increased by approximately 55%, and leg power increased by approximately 35%. These effects were maintained for at least 90 days after treatment. rMV is a short-lasting and noninvasive protocol that can significantly and persistently improve muscle performance in sedentary young-elderly women.
International Nuclear Information System (INIS)
Ansari, A.; Ring, P.
2006-01-01
The excitation energies and electric multipole decay rates of the lowest lying 2 + and 3 - vibrational states in Pb, Sn, and Ni nuclei are calculated following relativistic quasiparticle random-phase approximation formalism based on the relativistic Hartree-Bogoliubov mean field. Two sets of Lagrangian parameters, NL1 and NL3, are used to investigate the effect of the nuclear force. Overall there is good agreement with the available experimental data for a wide range of mass numbers considered here, and the NL3 set seems to be a better choice. However, strictly speaking, these studies point toward the need of a new set of force parameters that could produce more realistic single-particle levels, at least in vicinity of the Fermi surface, of a wide range of nuclear masses
Baumbach, Sebastian Felix; Fasser, Mariette; Polzer, Hans; Sieb, Michael; Regauer, Markus; Mutschler, Wolf; Schieker, Matthias; Blauth, Michael
2013-01-14
Ankle sprains often result in ankle instability, which is most likely caused by damage to passive structures and neuromuscular impairment. Whole body vibration (WBV) is a neuromuscular training method improving those impaired neurologic parameters. The aim of this study is to compare the current gold standard functional treatment to functional treatment plus WBV in patients with acute unilateral unstable inversion ankle sprains. 60 patients, aged 18-40 years, presenting with an isolated, unilateral, acute unstable inversion ankle sprain will be included in this bicentric, biphasic, randomized controlled trial. Samples will be randomized by envelope drawing. All patients will be allowed early mobilization and pain-dependent weight bearing, limited functional immobilization by orthosis, PRICE, NSARDs as well as home and supervised physiotherapy. Supervised physical therapy will take place twice a week, for 30 minutes for a period of 6 weeks, following a standardized intervention protocol. During supervised physical therapy, the intervention group will perform exercises similar to those of the control group, on a side-alternating sinusoidal vibration platform. Two time-dependent primary outcome parameters will be assessed: short-term outcome after six weeks will be postural control quantified by the sway index; mid-term outcome after one year will be assessed by subjective instability, defined by the presence of giving-way attacks. Secondary outcome parameters include: return to pre-injury level of activities, residual pain, recurrence, objective instability, energy/coordination, Foot and Ankle Disability Index and EQ 5D. This is the first trial investigating the effects of WBV in patients with acute soft tissue injury. Inversion ankle sprains often result in ankle instability, which is most likely due to damage of neurological structures. Due to its unique, frequency dependent, influence on various neuromuscular parameters, WBV is a promising treatment method for
Directory of Open Access Journals (Sweden)
Baumbach Sebastian Felix
2013-01-01
Full Text Available Abstract Background Ankle sprains often result in ankle instability, which is most likely caused by damage to passive structures and neuromuscular impairment. Whole body vibration (WBV is a neuromuscular training method improving those impaired neurologic parameters. The aim of this study is to compare the current gold standard functional treatment to functional treatment plus WBV in patients with acute unilateral unstable inversion ankle sprains. Methods/Design 60 patients, aged 18–40 years, presenting with an isolated, unilateral, acute unstable inversion ankle sprain will be included in this bicentric, biphasic, randomized controlled trial. Samples will be randomized by envelope drawing. All patients will be allowed early mobilization and pain-dependent weight bearing, limited functional immobilization by orthosis, PRICE, NSARDs as well as home and supervised physiotherapy. Supervised physical therapy will take place twice a week, for 30 minutes for a period of 6 weeks, following a standardized intervention protocol. During supervised physical therapy, the intervention group will perform exercises similar to those of the control group, on a side-alternating sinusoidal vibration platform. Two time-dependent primary outcome parameters will be assessed: short-term outcome after six weeks will be postural control quantified by the sway index; mid-term outcome after one year will be assessed by subjective instability, defined by the presence of giving-way attacks. Secondary outcome parameters include: return to pre-injury level of activities, residual pain, recurrence, objective instability, energy/coordination, Foot and Ankle Disability Index and EQ 5D. Discussion This is the first trial investigating the effects of WBV in patients with acute soft tissue injury. Inversion ankle sprains often result in ankle instability, which is most likely due to damage of neurological structures. Due to its unique, frequency dependent, influence on various
Shock and vibration environments encountered during normal rail transportation of heavy cargo
International Nuclear Information System (INIS)
Magnuson, C.F.
1982-08-01
This study was conducted to obtain vibration and superimposed shock data during normal rail shipment of heavy cargo. The data were obtained during a regularly scheduled rail shipment of a 45-tonne (50-ton) cargo which consisted of an empty spent-fuel container, its supporting structure, and associated hoisting devices. The shipment was made over rail lines which are operated by the Atchison, Topeka, and Santa Fe Railway Company between Denver, Colorado and Albuquerque, New Mexico. The instrumented rail car was equipped with 0.38-m (15-in.) hydraulic end-of-car coupling devices. The 99 percentile levels of vibration acceleration amplitudes and single degree-of-freedom superimposed shock response spectra for the longitudinal, transverse, and vertical axes are presented
Benefits of Spacecraft Level Vibration Testing
Gordon, Scott; Kern, Dennis L.
2015-01-01
NASA-HDBK-7008 Spacecraft Level Dynamic Environments Testing discusses the approaches, benefits, dangers, and recommended practices for spacecraft level dynamic environments testing, including vibration testing. This paper discusses in additional detail the benefits and actual experiences of vibration testing spacecraft for NASA Goddard Space Flight Center (GSFC) and Jet Propulsion Laboratory (JPL) flight projects. JPL and GSFC have both similarities and differences in their spacecraft level vibration test approach: JPL uses a random vibration input and a frequency range usually starting at 5 Hz and extending to as high as 250 Hz. GSFC uses a sine sweep vibration input and a frequency range usually starting at 5 Hz and extending only to the limits of the coupled loads analysis (typically 50 to 60 Hz). However, both JPL and GSFC use force limiting to realistically notch spacecraft resonances and response (acceleration) limiting as necessary to protect spacecraft structure and hardware from exceeding design strength capabilities. Despite GSFC and JPL differences in spacecraft level vibration test approaches, both have uncovered a significant number of spacecraft design and workmanship anomalies in vibration tests. This paper will give an overview of JPL and GSFC spacecraft vibration testing approaches and provide a detailed description of spacecraft anomalies revealed.
International Nuclear Information System (INIS)
Ashraf, K; Md Khir, M H; Baharudin, Z; Dennis, J O
2013-01-01
This paper presents a bounded vibration energy harvester to effectively harvest energy from a wide band of low-frequency environmental vibrations ranging from 10 to 18 Hz. Rigid mechanical stoppers are used to confine the seismic mass movement within the elastic limits of the spring. Experimental results show the effectiveness of the proposed technique in increasing the efficiency of the energy harvester. When excited at a frequency of 10 Hz with a peak acceleration of 1 g, the harvester responds at a higher frequency of 20 Hz and gives a peak power of 2.68 mW and a peak to peak voltage of 2.62 V across a load of 220 Ω. The average power density of 65.74 μW cm −3 obtained at 10 Hz 1 g excitation monotonically increases with frequency up to 341.86 μW cm −3 at 18 Hz. An analytical model describing the nonlinear dynamics of the proposed harvester is also presented. A simple technique to estimate the energy losses during impact and thereof a method to incorporate these losses in the model are suggested. The presented model not only predicts the experimental voltage waveform and frequency response of the device with good similarity but also predicts the RMS voltage from the harvester for the whole range of operating frequencies with an RMS error of 5.2%. (paper)
Qing, Xinlin (Inventor); Beard, Shawn J. (Inventor); Li, Irene (Inventor)
2013-01-01
Sensors affixed to various such structures, where the sensors can withstand, remain affixed, and operate while undergoing both cryogenic temperatures and high vibrations. In particular, piezoelectric single crystal transducers are utilized, and these sensors are coupled to the structure via a low temperature, heat cured epoxy. This allows the transducers to monitor the structure while the engine is operating, even despite the harsh operating conditions. Aspects of the invention thus allow for real time monitoring and analysis of structures that operate in conditions that previously did not permit such analysis. A further aspect of the invention relates to use of piezoelectric single crystal transducers. In particular, use of such transducers allows the same elements to be used as both sensors and actuators.
Random Scenario Generation for a Multiple Target Tracking Environment Evaluation
DEFF Research Database (Denmark)
Hussain, Dil Muhammad Akbar
2006-01-01
, which were normally crossing targets, was to test the efficiency of the track splitting algorithm for different situations. However this approach only gives a measure of performance for a specific, possibly unrealistic, scenario and it was felt appropriate to develop procedures that would enable a more...... general performance assessment. Therefore, a random target motion scenario is adopted. Its implementation in particular for testing the track splitting algorithm using Kalman filters is used and a couple of tracking performance parameters are computed to investigate such random scenarios....
Bagherian, Ali; Sheikhfathollahi, Mahmood
2016-01-01
Topical anesthesia has been widely advocated as an important component of atraumatic administration of intraoral local anesthesia. The aim of this study was to use direct observation of children's behavioral pain reactions during local anesthetic injection using cotton-roll vibration method compared with routine topical anesthesia. Forty-eight children participated in this randomized controlled clinical trial. They received two separate inferior alveolar nerve block or primary maxillary molar infiltration injections on contralateral sides of the jaws by both cotton-roll vibration (a combination of topical anesthesia gel, cotton roll, and vibration for physical distraction) and control (routine topical anesthesia) methods. Behavioral pain reactions of children were measured according to the author-developed face, head, foot, hand, trunk, and cry (FHFHTC) scale, resulting in total scores between 0 and 18. The total scores on the FHFHTC scale ranged between 0-5 and 0-10 in the cotton-roll vibration and control methods, respectively. The mean ± standard deviation values of total scores on FHFHTC scale were lower in the cotton-roll vibration method (1.21 ± 1.38) than in control method (2.44 ± 2.18), and this was statistically significant (P anesthesia in reducing behavioral pain reactions in children during local anesthesia administration.
Multi-Exciter Vibroacoustic Simulation of Hypersonic Flight Vibration
International Nuclear Information System (INIS)
GREGORY, DANNY LYNN; CAP, JEROME S.; TOGAMI, THOMAS C.; NUSSER, MICHAEL A.; HOLLINGSHEAD, JAMES RONALD
1999-01-01
Many aerospace structures must survive severe high frequency, hypersonic, random vibration during their flights. The random vibrations are generated by the turbulent boundary layer developed along the exterior of the structures during flight. These environments have not been simulated very well in the past using a fixed-based, single exciter input with an upper frequency range of 2 kHz. This study investigates the possibility of using acoustic ardor independently controlled multiple exciters to more accurately simulate hypersonic flight vibration. The test configuration, equipment, and methodology are described. Comparisons with actual flight measurements and previous single exciter simulations are also presented
Bounds on the vibrational energy that can be harvested from random base motion
Langley, R. S.
2015-03-01
This paper is concerned with the development of upper bounds on the energy harvesting performance of a general multi-degree-of-freedom nonlinear electromechanical system that is subjected to random base motion and secondary applied periodic forces. The secondary forces are applied with the aim of enhancing the energy harvested from the base motion, and they may constitute direct excitation, or they may produce parametric terms in the equations of motion. It is shown that when the base motion has white noise acceleration then the power input by the base is always πS0 M / 2 where S0 is the single sided spectral density of the acceleration, and M is the mass of the system. This implies that although the secondary forces may enhance the energy harvested by causing a larger fraction of the power input from the base to be harvested rather than dissipated, there is an upper limit on the power that can be harvested. Attention is then turned to narrow band excitation, and it is found that in the absence of secondary forces a bound can be derived for a single degree of freedom system with linear damping and arbitrary nonlinear stiffness. The upper bound on the power input by the base is πM max [ S (ω) ] / 2, where S (ω) is the single sided base acceleration spectrum. The validity of this result for more general systems is found to be related to the properties of the first Wiener kernel, and this issue is explored analytically and by numerical simulation.
Directory of Open Access Journals (Sweden)
Siewe Jan
2010-06-01
Full Text Available Abstract Background Osteoarthritis (OA is the most common degenerative arthropathy. Load-bearing joints such as knee and hip are more often affected than spine or hands. The prevalence of gonarthrosis is generally higher than that of coxarthrosis. Because no cure for OA exists, the main emphasis of therapy is analgesic treatment through either mobility or medication. Non-pharmacologic treatment is the first step, followed by the addition of analgesic medication, and ultimately by surgery. The goal of non-pharmacologic and non-invasive therapy is to improve neuromuscular function, which in turn both prevents formation of and delays progression of OA. A modification of conventional physiotherapy, whole body vibration has been successfully employed for several years. Since its introduction, this therapy is in wide use at our facility not only for gonarthrosis, but also coxarthrosis and other diseases leading to muscular imbalance. Methods/Design This study is a randomized, therapy-controlled trial in a primary care setting at a university hospital. Patients presenting to our outpatient clinic with initial symptoms of gonarthrosis will be assessed against inclusion and exclusion criteria. After patient consent, 6 weeks of treatment will ensue. During the six weeks of treatment, patients will receive one of two treatments, conventional physiotherapy or whole-body-vibration exercises of one hour three times a week. Follow-up examinations will be performed immediately after treatment and after another 6 and 20 weeks, for a total study duration of 6 months. 20 patients will be included in each therapy group. Outcome measurements will include objective analysis of motion and ambulation as well as examinations of balance and isokinetic force. The Western Ontario and McMaster Universities Arthritis Index and SF-12 scores, the patients' overall status, and clinical examinations of the affected joint will be carried out. Discussion As new physiotherapy
Stein, Gregor; Knoell, Peter; Faymonville, Christoph; Kaulhausen, Thomas; Siewe, Jan; Otto, Christina; Eysel, Peer; Zarghooni, Kourosh
2010-06-21
Osteoarthritis (OA) is the most common degenerative arthropathy. Load-bearing joints such as knee and hip are more often affected than spine or hands. The prevalence of gonarthrosis is generally higher than that of coxarthrosis.Because no cure for OA exists, the main emphasis of therapy is analgesic treatment through either mobility or medication. Non-pharmacologic treatment is the first step, followed by the addition of analgesic medication, and ultimately by surgery.The goal of non-pharmacologic and non-invasive therapy is to improve neuromuscular function, which in turn both prevents formation of and delays progression of OA. A modification of conventional physiotherapy, whole body vibration has been successfully employed for several years. Since its introduction, this therapy is in wide use at our facility not only for gonarthrosis, but also coxarthrosis and other diseases leading to muscular imbalance. This study is a randomized, therapy-controlled trial in a primary care setting at a university hospital. Patients presenting to our outpatient clinic with initial symptoms of gonarthrosis will be assessed against inclusion and exclusion criteria. After patient consent, 6 weeks of treatment will ensue. During the six weeks of treatment, patients will receive one of two treatments, conventional physiotherapy or whole-body-vibration exercises of one hour three times a week. Follow-up examinations will be performed immediately after treatment and after another 6 and 20 weeks, for a total study duration of 6 months. 20 patients will be included in each therapy group.Outcome measurements will include objective analysis of motion and ambulation as well as examinations of balance and isokinetic force. The Western Ontario and McMaster Universities Arthritis Index and SF-12 scores, the patients' overall status, and clinical examinations of the affected joint will be carried out. As new physiotherapy techniques develop for the treatment of OA, it is important to
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Lai CL
2013-12-01
Full Text Available Chung-Liang Lai,1,2 Shiuan-Yu Tseng,1,2 Chung-Nan Chen,3 Wan-Chun Liao,2 Chun-Hou Wang,4 Meng-Chih Lee,1,5,* Pi-Shan Hsu5,* 1Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan; 2Department of Physical Medicine and Rehabilitation, Taichung Hospital, Ministry of Health and Welfare, Taichung, Taiwan; 3Department of Radiology, Taichung Hospital, Ministry of Health and Welfare, Taichung, Taiwan; 4School of Physical Therapy, Chung Shan Medical University, Taichung, Taiwan; 5Department of Family Medicine, Taichung Hospital, Ministry of Health and Welfare, Taichung, Taiwan*These authors contributed equally to this workBackground: The issue of osteoporosis-induced fractures has attracted the world's attention. Postmenopausal women are particularly at risk for this type of fracture. The nonmedicinal intervention for postmenopausal women is mainly exercise. Whole body vibration (WBV is a simple and convenient exercise. There have been some studies investigating the effect of WBV on osteoporosis; however, the intervention models and results are different. This study mainly investigated the effect of high-frequency and high-magnitude WBV on the bone mineral density (BMD of the lumbar spine in postmenopausal women.Methods: This study randomized 28 postmenopausal women into either the WBV group or the control group for a 6-month trial. The WBV group received an intervention of high-frequency (30 Hz and high-magnitude (3.2 g WBV in a natural full-standing posture for 5 minutes, three times per week, at a sports center. Dual-energy X-ray absorptiometry was used to measure the lumbar BMD of the two groups before and after the intervention.Results: Six months later, the BMD of the WBV group had significantly increased by 2.032% (P=0.047, while that of the control group had decreased by 0.046% (P=0.188. The comparison between the two groups showed that the BMD of the WBV group had increased significantly (P=0.016.Conclusion: This study found
Spatial birth-and-death processes in random environment
Fernandez, Roberto; Ferrari, Pablo A.; Guerberoff, Gustavo R.
2004-01-01
We consider birth-and-death processes of objects (animals) defined in ${\\bf Z}^d$ having unit death rates and random birth rates. For animals with uniformly bounded diameter we establish conditions on the rate distribution under which the following holds for almost all realizations of the birth rates: (i) the process is ergodic with at worst power-law time mixing; (ii) the unique invariant measure has exponential decay of (spatial) correlations; (iii) there exists a perfect-simulation algorit...
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Kazem Reza Kashyzadeh
2015-09-01
Full Text Available The impact of a suitable suspension system for passenger comfort and vehicle steering is an obvious order and direct impact on the safety of passengers must be considered, to do so different kinds of tests must be exerted, one of these is fatigue testing which is one of the most significant ones. Another issue is the high cost in practical ways, and to cope with this issue various ways must be assessed and analyzed, one of the best and the most efficient ways is modelling and testing in virtual software environments. In the present paper, predict fatigue life of suspension component and package of automotive suspension are the main purposes. First, using MATLAB software, road roughness according to the intercity roads for constant vehicle velocity (100 Km/h has been studied. After that frequency response of components has been analysed, its critical points determined to calculate the fatigue life of the part, and the amount of critical stress obtained based on Von Misses, Tresca and Max Principle criterion for a quarter car model (passive suspension System in 206 Peugeot. Fatigue life of the vehicle components are calculated in terms of kilo-Meters in specialized fatigue software such as 116944, 92638.9, 46388.9 and 191388.9 Km respectively wheel hub, pitman arm, suspension arm and package of suspension. Finally, to prove the given results of the finite element method compared with reported results by other researchers and the results match very well with those.
Lotka-Volterra system in a random environment
Dimentberg, Mikhail F.
2002-03-01
Classical Lotka-Volterra (LV) model for oscillatory behavior of population sizes of two interacting species (predator-prey or parasite-host pairs) is conservative. This may imply unrealistically high sensitivity of the system's behavior to environmental variations. Thus, a generalized LV model is considered with the equation for preys' reproduction containing the following additional terms: quadratic ``damping'' term that accounts for interspecies competition, and term with white-noise random variations of the preys' reproduction factor that simulates the environmental variations. An exact solution is obtained for the corresponding Fokker-Planck-Kolmogorov equation for stationary probability densities (PDF's) of the population sizes. It shows that both population sizes are independent γ-distributed stationary random processes. Increasing level of the environmental variations does not lead to extinction of the populations. However it may lead to an intermittent behavior, whereby one or both population sizes experience very rare and violent short pulses or outbreaks while remaining on a very low level most of the time. This intermittency is described analytically by direct use of the solutions for the PDF's as well as by applying theory of excursions of random functions and by predicting PDF of peaks in the predators' population size.
International Nuclear Information System (INIS)
Shit, G.C.; Majee, Sreeparna
2015-01-01
Unsteady flow of blood and heat transfer characteristics in the neighborhood of an overlapping constricted artery have been investigated in the presence of magnetic field and whole body vibration. The laminar flow of blood is taken to be incompressible and Newtonian fluid with variable viscosity depending upon temperature with an aim to provide resemblance to the real situation in the physiological system. The unsteady flow mechanism in the constricted artery is subjected to a pulsatile pressure gradient arising from systematic functioning of the heart and from the periodic body acceleration. The numerical computation has been performed using finite difference method by developing Crank–Nicolson scheme. The results show that the volumetric flow rate, skin-friction and the rate of heat transfer at the wall are significantly altered in the downstream of the constricted region. The axial velocity profile, temperature and flow rate increases with increase in temperature dependent viscosity, while the opposite trend is observed in the case of skin-friction and flow impedance. - Highlights: • We have investigated the pulsatile MHD flow of blood and heat transfer in arteries. • The influence of periodic body acceleration has been taken into account. • The temperature dependent viscosity of blood is considered. • The variable viscosity has an increasing effect on blood flow and heat transfer. • The overall temperature distribution enhances in the presence of magnetic field
Energy Technology Data Exchange (ETDEWEB)
Shit, G.C., E-mail: gopal_iitkgp@yahoo.co.in; Majee, Sreeparna
2015-08-15
Unsteady flow of blood and heat transfer characteristics in the neighborhood of an overlapping constricted artery have been investigated in the presence of magnetic field and whole body vibration. The laminar flow of blood is taken to be incompressible and Newtonian fluid with variable viscosity depending upon temperature with an aim to provide resemblance to the real situation in the physiological system. The unsteady flow mechanism in the constricted artery is subjected to a pulsatile pressure gradient arising from systematic functioning of the heart and from the periodic body acceleration. The numerical computation has been performed using finite difference method by developing Crank–Nicolson scheme. The results show that the volumetric flow rate, skin-friction and the rate of heat transfer at the wall are significantly altered in the downstream of the constricted region. The axial velocity profile, temperature and flow rate increases with increase in temperature dependent viscosity, while the opposite trend is observed in the case of skin-friction and flow impedance. - Highlights: • We have investigated the pulsatile MHD flow of blood and heat transfer in arteries. • The influence of periodic body acceleration has been taken into account. • The temperature dependent viscosity of blood is considered. • The variable viscosity has an increasing effect on blood flow and heat transfer. • The overall temperature distribution enhances in the presence of magnetic field.
Ko, Ming-Chen; Wu, Long-Shan; Lee, Sangwoo; Wang, Chien-Chun; Lee, Po-Fu; Tseng, Ching-Yu; Ho, Chien-Chang
2017-01-01
Background Aging is associated with decreased balance, which increases falling risk. The objective of the current study was to determine the feasibility and effects of whole-body vibration (WBV) training on knee extensor muscle power, limits of stability, and sit-to-stand performance among community-dwelling middle-aged and older adults in the United States. Methods A randomized pilot study with participant blinding was conducted. Feasibility outcomes included recruitment and compliance rate....
Semi-active vibration control in cable-stayed bridges under the condition of random wind load
International Nuclear Information System (INIS)
Heo, G; Joonryong, Jeon
2014-01-01
This paper aims at an experimental study on the real-time vibration control of bridge structures using a semi-active vibration control method that has been in the spotlight recently. As structures are becoming larger and larger, structural harmful vibration caused by unspecified external forces such as earthquakes, gusts of wind, and collisions has been brought to attention as an important issue. These harmful vibrations can cause not only user anxiety but also severe structural damage or even complete failure of structures. Therefore, in view of structural safety and economical long-term maintenance, real-time control technology of the harmful structural vibration is urgently required. In this paper, a laboratory-scale model of a cable-stayed bridge was built, and a shear-type MR damper and a semi-active vibration control algorithm (Lyapunov and clipped optimal) were applied for the control of harmful vibration of the model bridge, in real time. On the basis of the test results, each semi-active control algorithm was verified quantitatively. (papers)
Value of the future: Discounting in random environments
Farmer, J. Doyne; Geanakoplos, John; Masoliver, Jaume; Montero, Miquel; Perelló, Josep
2015-05-01
We analyze how to value future costs and benefits when they must be discounted relative to the present. We introduce the subject for the nonspecialist and take into account the randomness of the economic evolution by studying the discount function of three widely used processes for the dynamics of interest rates: Ornstein-Uhlenbeck, Feller, and log-normal. Besides obtaining exact expressions for the discount function and simple asymptotic approximations, we show that historical average interest rates overestimate long-run discount rates and that this effect can be large. In other words, long-run discount rates should be substantially less than the average rate observed in the past, otherwise any cost-benefit calculation would be biased in favor of the present and against interventions that may protect the future.
DiBiase, Andrew T; Woodhouse, Neil R; Papageorgiou, Spyridon N; Johnson, Nicola; Slipper, Carmel; Grant, James; Alsaleh, Maryam; Khaja, Yousef; Cobourne, Martyn T
2018-04-01
A multicenter parallel 3-arm randomized clinical trial was carried out in 3 university hospitals in the United Kingdom to investigate the effect of supplemental vibratory force on space closure and treatment outcome with fixed appliances. Eighty-one subjects less than 20 years of age with mandibular incisor irregularity undergoing extraction-based fixed appliance treatment were randomly allocated to supplementary (20 minutes/day) use of an intraoral vibrational device (AcceleDent; OrthoAccel Technologies, Houston, Tex) (n = 29), an identical nonfunctional (sham) device (n = 25), or fixed-appliance only (n = 27). Space closure in the mandibular arch was measured from dental study casts taken at the start of space closure, at the next appointment, and at completion of space closure. Final records were taken at completion of treatment. Data were analyzed blindly on a per-protocol basis with descriptive statistics, 1-way analysis of variance, and linear regression modeling with 95% confidence intervals. Sixty-one subjects remained in the trial at start of space closure, with all 3 groups comparable for baseline characteristics. The overall median rate of initial mandibular arch space closure (primary outcome) was 0.89 mm per month with no difference for either the AcceleDent group (difference, -0.09 mm/month; 95% CI, -0.39 to 0.22 mm/month; P = 0.57) or the sham group (difference, -0.02 mm/month; 95% CI, -0.32 to 0.29 mm/month; P = 0.91) compared with the fixed only group. Similarly, no significant differences were identified between groups for secondary outcomes, including overall treatment duration (median, 18.6 months; P >0.05), number of visits (median, 12; P >0.05), and percentage of improvement in the Peer Assessment Rating (median, 90.0%; P >0.05). Supplemental vibratory force during orthodontic treatment with fixed appliances does not affect space closure, treatment duration, total number of visits, or final occlusal outcome. NCT02314975
Gerçeker, Gülçin Ö; Binay, Şeyda; Bilsin, Elif; Kahraman, Ayşe; Yılmaz, Hatice B
2018-03-17
The aim of this study was to evaluate the effects of the virtual reality (VR) and external cold and vibration methods on pain scores in children aged 7 to 12 years during phlebotomy. A randomized controlled study. The sample of children (n = 121) was allocated to the groups (group 1, VR; group 2, external cold and vibration; group 3, control) by blocked randomization. Pain scores were assessed after the phlebotomy using self-report, parent's reports, report from the nurse who attempted the phlebotomy, and researchers' report with the Wong-Baker FACES scale. Pain scores were determined to be lower in groups 1 and 2. Although there was no difference between the groups 1 and 2, a statistically significant difference was found between groups 1 or 2 and group 3 based on all pain scores. Results suggest that VR and external cold and vibration are effective in reducing the pain in 7- to 12-year-old children during phlebotomy. VR can be used safely for the pain management of children who are growing up in the age of technology. Copyright © 2018 American Society of PeriAnesthesia Nurses. Published by Elsevier Inc. All rights reserved.
Water-mediated influence of a crowded environment on internal vibrations of a protein molecule.
Kuffel, Anna; Zielkiewicz, Jan
2016-02-14
The influence of crowding on the protein inner dynamics is examined by putting a single protein molecule close to one or two neighboring protein molecules. The presence of additional molecules influences the amplitudes of protein fluctuations. Also, a weak dynamical coupling of collective velocities of surface atoms of proteins separated by a layer of water is detected. The possible mechanisms of these phenomena are described. The cross-correlation function of the collective velocities of surface atoms of two proteins was decomposed into the Fourier series. The amplitude spectrum displays a peak at low frequencies. Also, the results of principal component analysis suggest that the close presence of an additional protein molecule influences the high-amplitude, low-frequency modes in the most prominent way. This part of the spectrum covers biologically important protein motions. The neighbor-induced changes in the inner dynamics of the protein may be connected with the changes in the velocity power spectrum of interfacial water. The additional protein molecule changes the properties of solvation water and in this way it can influence the dynamics of the second protein. It is suggested that this phenomenon may be described, at first approximation, by a damped oscillator driven by an external random force. This model was successfully applied to conformationally rigid Choristoneura fumiferana antifreeze protein molecules.
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Chaudhari Virendra Kumar
2017-01-01
Full Text Available This paper deals with the investigation of nonlinear free vibration behavior of elastically supported carbon nanotube reinforced composite (CNTRC beam subjected to thermal loading with random system properties. Material properties of each constituent’s material, volume fraction exponent and foundation parameters are considered as uncorrelated Gaussian random input variables. The beam is supported by a Pasternak foundation with Winkler cubic nonlinearity. The higher order shear deformation theory (HSDT with von-Karman non-linearity is used to formulate the governing equation using Hamilton principle. Convergence and validation study is carried out through the comparison with the available results in the literature for authenticity and accuracy of the present approach used in the analysis. First order perturbation technique (FOPT,Second order perturbation technique (SOPT and Monte Carlo simulation (MCS methods are employed to investigate the effect of geometric configuration, volume fraction exponent, foundation parameters, distribution of reinforcement and thermal loading on nonlinear vibration characteristics CNTRC beam.The present work signifies the accurate analysis of vibrational behaviour influences by different random variables. Results are presented in terms of mean, variance (COV and probability density function (PDF for various aforementioned parameters.
Zhang, Li; Weng, Changshui; Liu, Miao; Wang, Qiuhua; Liu, Liming; He, Yao
2014-01-01
To study the effects of whole-body vibration exercises on the mobility function, balance and general health status, and its feasibility as an intervention in frail elderly patients. Pilot randomized controlled trial. Forty-four frail older persons (85.27 ± 3.63 years) meeting the Fried Frailty Criteria. All eligible subjects were randomly assigned to the experimental group, who received a whole-body vibration exercise alone (vibration amplitude: 1-3 mm; frequency: 6-26 Hz; 4-5 bouts × 60 seconds; 3-5 times weekly), or a control group, who received usual care and exercises for eight weeks. The Timed Up and Go Test, 30-second chair stand test, lower extremities muscle strength, balance function, balance confidence and General Health Status were assessed at the beginning of the study, after four weeks and eight weeks of the intervention. Whole-body vibration exercise reduced the time of the Timed Up and Go Test (40.47 ± 15.94 s to 21.34 ± 4.42 s), improved the bilateral knees extensor strength (6.96 ± 1.70 kg to 11.26 ± 2.08 kg), the posture stability (surface area ellipse: 404.58 ± 177.05 to 255.95 ± 107.28) and General Health Status (Short-form Health Survey score: 24.51 ± 10.69 and 49.63 ± 9.85 to 45.03 ± 11.15 and 65.23 ± 9.39, respectively). The repeated-measures ANOVA showed that there were significant differences in the Timed Up and Go Test, 30-second chair stand test, bilateral knees extensor strength, activities-specific balance confidence score and general health status between the two groups (P balance and the general health status in the frail elderly.
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Wolbert van den Hoorn
2018-03-01
Full Text Available Aging is associated with changes in balance control and elderly take longer to adapt to changing sensory conditions, which may increase falls risk. Low amplitude calf muscle vibration stimulates local sensory afferents/receptors and affects sense of upright when applied in stance. It has been used to assess the extent the nervous system relies on calf muscle somatosensory information and to rapidly change/perturb part of the somatosensory information causing balance unsteadiness by addition and removal of the vibratory stimulus. This study assessed the effect of addition and removal of calf vibration on balance control (in the absence of vision in elderly individuals (>65 years, n = 99 who did (n = 41 or did not prospectively report falls (n = 58, and in a group of young individuals (18–25 years, n = 23. Participants stood barefoot and blindfolded on a force plate for 135 s. Vibrators (60 Hz, 1 mm attached bilaterally over the triceps surae muscles were activated twice for 15 s; after 15 and 75 s (45 s for recovery. Balance measures were applied in a windowed (15 s epoch manner to compare center-of-pressure (CoP motion before, during and after removal of calf vibration between groups. In each epoch, CoP motion was quantified using linear measures, and non-linear measures to assess temporal structure of CoP motion [using recurrence quantification analysis (RQA and detrended fluctuation analysis]. Mean CoP displacement during and after vibration did not differ between groups, which suggests that calf proprioception and/or weighting assigned by the nervous system to calf proprioception was similar for the young and both groups of older individuals. Overall, compared to the elderly, CoP motion of young was more predictable and persistent. Balance measures were not different between fallers and non-fallers before and during vibration. However, non-linear aspects of CoP motion of fallers and non-fallers differed after removal of vibration, when
Heterogeneous Dynamics of Coupled Vibrations
Cringus, Dan; Jansen, Thomas I. C.; Pshenichnikov, Maxim S.; Schoenlein, RW; Corkum, P; DeSilvestri, S; Nelson, KA; Riedle, E
2009-01-01
Frequency-dependent dynamics of coupled stretch vibrations of a water molecule are revealed by 2D IR correlation spectroscopy. These are caused by non-Gaussian fluctuations of the environment around the individual OH stretch vibrations.
Genomic-Enabled Prediction Kernel Models with Random Intercepts for Multi-environment Trials
Cuevas, Jaime; Granato, Italo; Fritsche-Neto, Roberto; Montesinos-Lopez, Osval A.; Burgueño, Juan; Bandeira e Sousa, Massaine; Crossa, José
2018-01-01
In this study, we compared the prediction accuracy of the main genotypic effect model (MM) without G×E interactions, the multi-environment single variance G×E deviation model (MDs), and the multi-environment environment-specific variance G×E deviation model (MDe) where the random genetic effects of the lines are modeled with the markers (or pedigree). With the objective of further modeling the genetic residual of the lines, we incorporated the random intercepts of the lines (l) and generated another three models. Each of these 6 models were fitted with a linear kernel method (Genomic Best Linear Unbiased Predictor, GB) and a Gaussian Kernel (GK) method. We compared these 12 model-method combinations with another two multi-environment G×E interactions models with unstructured variance-covariances (MUC) using GB and GK kernels (4 model-method). Thus, we compared the genomic-enabled prediction accuracy of a total of 16 model-method combinations on two maize data sets with positive phenotypic correlations among environments, and on two wheat data sets with complex G×E that includes some negative and close to zero phenotypic correlations among environments. The two models (MDs and MDE with the random intercept of the lines and the GK method) were computationally efficient and gave high prediction accuracy in the two maize data sets. Regarding the more complex G×E wheat data sets, the prediction accuracy of the model-method combination with G×E, MDs and MDe, including the random intercepts of the lines with GK method had important savings in computing time as compared with the G×E interaction multi-environment models with unstructured variance-covariances but with lower genomic prediction accuracy. PMID:29476023
Random neural Q-learning for obstacle avoidance of a mobile robot in unknown environments
Directory of Open Access Journals (Sweden)
Jing Yang
2016-07-01
Full Text Available The article presents a random neural Q-learning strategy for the obstacle avoidance problem of an autonomous mobile robot in unknown environments. In the proposed strategy, two independent modules, namely, avoidance without considering the target and goal-seeking without considering obstacles, are first trained using the proposed random neural Q-learning algorithm to obtain their best control policies. Then, the two trained modules are combined based on a switching function to realize the obstacle avoidance in unknown environments. For the proposed random neural Q-learning algorithm, a single-hidden layer feedforward network is used to approximate the Q-function to estimate the Q-value. The parameters of the single-hidden layer feedforward network are modified using the recently proposed neural algorithm named the online sequential version of extreme learning machine, where the parameters of the hidden nodes are assigned randomly and the sample data can come one by one. However, different from the original online sequential version of extreme learning machine algorithm, the initial output weights are estimated subjected to quadratic inequality constraint to improve the convergence speed. Finally, the simulation results demonstrate that the proposed random neural Q-learning strategy can successfully solve the obstacle avoidance problem. Also, the higher learning efficiency and better generalization ability are achieved by the proposed random neural Q-learning algorithm compared with the Q-learning based on the back-propagation method.
Bieniek, Ronald
2008-05-01
Rates for collisionally induced transitions between molecular vibrational levels are important in modeling a variety of non-LTE processes in astrophysical environments. Two examples are SiO masering in circumstellar envelopes in certain late-type stars [1] and the vibrational populations of molecular hydrogen in shocked interstellar medium [cf 2]. A simple exponential-potential model of molecular collisions leads to a two-parameter analytic expression for state-to-state and thermally averaged rates for collisionally induced vibrational-translational (VT) transitions in diatomic molecules [3,4]. The thermally averaged rates predicted by this formula have been shown to be in excellent numerical agreement with absolute experimental and quantum mechanical rates over large temperature ranges and initial vibrational excitation levels in a variety of species, e.g., OH, O2, N2 [3] and even for the rate of H2(v=1)+H2, which changes by five orders of magnitude in the temperature range 50-2000 K [4]. Analogous analytic rates will be reported for vibrational transitions in SiO due to collisions with H2 and compared to the numerical fit of quantum-mechanical rates calculated by Bieniek and Green [5]. [1] Palov, A.P., Gray, M.D., Field, D., & Balint-Kurti, G.G. 2006, ApJ, 639, 204. [2] Flower, D. 2007, Molecular Collisions in the Interstellar Medium (Cambridge: Cambridge Univ. Press) [3] Bieniek, R.J. & Lipson, S.J. 1996, Chem. Phys. Lett. 263, 276. [4] Bieniek, R.J. 2006, Proc. NASA LAW (Lab. Astrophys. Workshop) 2006, 299; http://www.physics.unlv.edu/labastro/nasalaw2006proceedings.pdf. [5] Bieniek, R.J., & Green, S. 1983, ApJ, 265, L29 and 1983, ApJ, 270, L101.
Ajori, S; Ansari, R; Darvizeh, M
2016-03-01
The adsorption of biomolecules on the walls of carbon nanotubes (CNTs) in an aqueous environment is of great importance in the field of nanobiotechnology. In this study, molecular dynamics (MD) simulations were performed to understand the mechanical vibrational behavior of single- and double-walled carbon nanotubes (SWCNTs and DWCNTs) under the physical adsorption of four important biomolecules (L-alanine, guanine, thymine, and uracil) in vacuum and an aqueous environment. It was observed that the natural frequencies of these CNTs in vacuum reduce under the physical adsorption of biomolecules. In the aqueous environment, the natural frequency of each pure CNT decreased as compared to its natural frequency in vacuum. It was also found that the frequency shift for functionalized CNTs as compared to pure CNTs in the aqueous environment was dependent on the radius and the number of walls of the CNT, and could be positive or negative.
Nelson, A D; Camilleri, M; Acosta, A; Boldingh, A; Busciglio, I; Burton, D; Ryks, M; Zinsmeister, A R
2017-07-01
In an open-label study of 26 patients with IBS-C and chronic constipation, treatment with a vibrating (VIBRANT) capsule twice a week for 7.5 weeks resulted in 88.5% responders. Effects on colonic transit are unclear. We aimed to compare effects of VIBRANT and sham capsule treatment on colonic transit in patients with functional constipation. Patients with functional constipation (Rome III criteria) were randomized to VIBRANT or sham capsule treatment for 8 weeks and underwent scintigraphic colonic transit measurements during week 8. We estimated the overall rate of colonic transit from the slope of progression of colonic geometric center over 48 hours. The capsule was activated 8 hours after ingestion, and the vibration sequence included 240 cycles. There were no significant group differences in overall colonic transit [GC48, 2.76 (IQR 2.42-4.03) for sham group and 3.46 (2.55-4.61) for active treatment group (P=.13)]. Additionally, the progression of the isotope through the colon was numerically faster, though not significantly different (slope, P=.14) in the VIBRANT capsule group compared to the sham group. Three participants in the VIBRANT capsule group had accelerated colonic transit at 32 hours and faster colonic transit slope compared to the 95th percentile of the sham group. Although there were no group differences between VIBRANT and sham capsule treatment on colonic transit, at least one (and possibly three) of 12 patients receiving the VIBRANT capsule had faster colonic transit. The vibration parameters to accelerate colonic transit in patients with functional constipation require further optimization. © 2017 John Wiley & Sons Ltd.
Mainz, Jochen G; Schädlich, Katja; Schien, Claudia; Michl, Ruth; Schelhorn-Neise, Petra; Koitschev, Assen; Koitschev, Christiane; Keller, Peter M; Riethmüller, Joachim; Wiedemann, Baerbel; Beck, James F
2014-01-01
Rationale In cystic fibrosis (CF), the paranasal sinuses are sites of first and persistent colonization by pathogens such as Pseudomonas aeruginosa. Pathogens subsequently descend to the lower airways, with P. aeruginosa remaining the primary cause of premature death in patients with the inherited disease. Unlike conventional aerosols, vibrating aerosols applied with the PARI Sinus™ nebulizer deposit drugs into the paranasal sinuses. This trial assessed the effects of vibrating sinonasal inhalation of the antibiotic tobramycin in CF patients positive for P. aeruginosa in nasal lavage. Objectives To evaluate the effects of sinonasal inhalation of tobramycin on P. aeruginosa quantification in nasal lavage; and on patient quality of life, measured with the Sino-Nasal Outcome Test (SNOT-20), and otologic and renal safety and tolerability. Methods Patients were randomized to inhalation of tobramycin (80 mg/2 mL) or placebo (2 mL isotonic saline) once daily (4 minutes/nostril) with the PARI Sinus™ nebulizer over 28 days, with all patients eligible for a subsequent course of open-label inhalation of tobramycin for 28 days. Nasal lavage was obtained before starting and 2 days after the end of each treatment period by rinsing each nostril with 10 mL of isotonic saline. Results Nine patients participated, six initially receiving tobramycin and three placebo. Sinonasal inhalation was well tolerated, with serum tobramycin <0.5 mg/L and stable creatinine. P. aeruginosa quantity decreased in four of six (67%) patients given tobramycin, compared with zero of three given placebo (non-significant). SNOT-20 scores were significantly lower in the tobramycin than in the placebo group (P=0.033). Conclusion Sinonasal inhalation of vibrating antibiotic aerosols appears promising for reducing pathogen colonization of paranasal sinuses and for control of symptoms in patients with CF. PMID:24596456
Lee, Jung-Sun; Kim, Chang-Yong; Kim, Hyeong-Dong
2016-08-01
The aim of this study was to determine the effect of whole-body vibration training combined with task-related training on arm function, spasticity, and grip strength in subjects with poststroke hemiplegia. Forty-five subjects with poststroke were randomly allocated to 3 groups, each with 15 subjects as follows: control group, whole-body vibration group, and whole-body vibration plus task-related training group. Outcome was evaluated by clinical evaluation and measurements of the grip strength before and 4 weeks after intervention. Our results show that there was a significantly greater increase in the Fugl-Meyer scale, maximal grip strength of the affected hand, and grip strength normalized to the less affected hand in subjects undergoing the whole-body vibration training compared with the control group after the test. Furthermore, there was a significantly greater increase in the Wolf motor function test and a decrease in the modified Ashworth spasticity total scores in subjects who underwent whole-body vibration plus task-related training compared with those in the other 2 groups after the test. The findings indicate that the use of whole-body vibration training combined with task-related training has more benefits on the improvement of arm function, spasticity, and maximal grip strength than conventional upper limb training alone or with whole-body vibration in people with poststroke hemiplegia.
[On the extinction of populations with several types in a random environment].
Bacaër, Nicolas
2018-03-01
This study focuses on the extinction rate of a population that follows a continuous-time multi-type branching process in a random environment. Numerical computations in a particular example inspired by an epidemic model suggest an explicit formula for this extinction rate, but only for certain parameter values. Copyright © 2018 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Directory of Open Access Journals (Sweden)
Shui-Ting Zhou
2017-01-01
Full Text Available This study is about the impact of the performance and the sensitivity analysis for parameters of the torsion bar suspension in the electric sight-seeing car, which the authors’ laboratory designed and which is used in the authors’ university. The suspension stiffness was calculated by using the virtual work principle, the vector algebra, and tensor of finite rotation methods and was verified by the ADAMS software. Based on the random vibration analysis method, the paper analyzed the dynamic tire load (DTL, suspension working space (SWS, and comfort performance parameters. For the purpose of decreasing the displacement of the suspension and limiting the frequency of impacting the stop block, the paper examined the three parameters and optimized the basic parameters of the torsion bar. The results show that the method achieves a great effect and contributes an accurate value for the general layout design.
Avena, L.; Hollander, den W.Th.F.; Redig, F.H.J.
2009-01-01
Consider a one-dimensional shift-invariant attractive spin-ip system in equilibrium, constituting a dynamic random environment, together with a nearest-neighbor random walk that on occupied sites has a local drift to the right but on vacant sites has a local drift to the left. In [2] we proved a law
Avena, L.; Hollander, den W.Th.F.; Redig, F.H.J.
2010-01-01
Consider a one-dimensional shift-invariant attractive spin-flip system in equilibrium, constituting a dynamic random environment, together with a nearest-neighbor random walk that on occupied sites has a local drift to the right but on vacant sites has a local drift to the left. In previous work we
Bogaerts, An; Delecluse, Christophe; Boonen, Steven; Claessens, Albrecht L; Milisen, Koen; Verschueren, Sabine M P
2011-03-01
Falls in the elderly constitute a growing public health problem. This randomized controlled trial investigated the potential benefit of 6 months of whole body vibration (WBV) training and/or vitamin D supplementation on balance, functionality and estimated fall risk in institutionalized elderly women. A total of 113 women (mean age: 79.6) were randomly assigned to either a WBV or a no-training group, receiving either a conventional dose (880 IU/d) or a high dose (1600 IU/d) of vitamin D3. The WBV group performed exercises on a vibration platform 3×/week. Balance was evaluated by computerized posturography. Functionality was assessed by 10 m walk test, Timed up and Go (TUG) performance and endurance capacity (Shuttle Walk). Fall risk was determined with the Physiological Profile Assessment. Performance on the 10 m walk test and on TUG improved over time in all groups. For none of the parameters, high-dose vitamin D resulted in a better performance than conventional dosing. The improvements in the WBV group in endurance capacity, walking at preferred speed, and TUG were significantly larger than the changes with supplementation alone. No additional benefit of WBV training could be detected on fall risk and postural control, although sway velocity and maximal isometric knee extension strength improved only in the WBV group. This trial showed that a high-dose vitamin D supplementation is not more efficient than conventional dosing in improving functionality in institutionalized elderly. WBV training on top of vitamin D supplementation provided an added benefit with regard to walking, TUG performance, and endurance capacity. Copyright © 2010 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Sohn, Jung Woo; Choi, Seung-Bok
2014-01-01
In the present work, the modal characteristics and vibration control performance of a cylindrical structure in air and water are experimentally investigated, and the results are presented in time and frequency domains. In order to achieve this goal, an end-capped cylindrical shell structure is considered as a host structure, and MFC (macro fiber composite) actuators, which are flexible, are bonded on the surface of the structure. After manufacturing a cylindrical shell structure with aluminum, a modal test is carried out, and the natural frequencies of the proposed structure are obtained and analyzed. To verify the modal test results, a finite element analysis is also performed, and the results are compared with the modal test results. By using the experimentally obtained modal characteristics, a state space control model is established. An optimal controller is then designed in order to control the unwanted vibration and is experimentally realized. It has been shown that the structural vibration can be effectively decreased with the optimal control methodology in both air and water environmental conditions. (technical note)
Predicting Statistical Distributions of Footbridge Vibrations
DEFF Research Database (Denmark)
Pedersen, Lars; Frier, Christian
2009-01-01
The paper considers vibration response of footbridges to pedestrian loading. Employing Newmark and Monte Carlo simulation methods, a statistical distribution of bridge vibration levels is calculated modelling walking parameters such as step frequency and stride length as random variables...
Vibration insensitive interferometry
Millerd, James; Brock, Neal; Hayes, John; Kimbrough, Brad; North-Morris, Michael; Wyant, James C.
2017-11-01
The largest limitation of phase-shifting interferometry for optical testing is the sensitivity to the environment, both vibration and air turbulence. An interferometer using temporal phase-shifting is very sensitive to vibration because the various phase shifted frames of interferometric data are taken at different times and vibration causes the phase shifts between the data frames to be different from what is desired. Vibration effects can be reduced by taking all the phase shifted frames simultaneously and turbulence effects can be reduced by averaging many measurements. There are several techniques for simultaneously obtaining several phase-shifted interferograms and this paper will discuss two such techniques: 1) Simultaneous phase-shifting interferometry on a single detector array (PhaseCam) and 2) Micropolarizer phase-shifting array. The application of these techniques for the testing of large optical components, measurement of vibrational modes, the phasing of segmented optical components, and the measurement of deformations of large diffuse structures is described.
Directory of Open Access Journals (Sweden)
Lal Achchhe
2017-09-01
Full Text Available This paper presents the free vibration response of piezo laminated composite geometrically nonlinear conical shell panel subjected to a thermo-electrical loading. The temperature field is assumed to be a uniform distribution over the shell surface and through the shell thickness and the electric field is assumed to be the transverse component E2 only. The material properties are assumed to be independent of the temperature and the electric field. The basic formulation is based on higher order shear deformation plate theory (HSDT with von-Karman nonlinearity. A C0 nonlinear finite element method based on direct iterative approach is outlined and applied to solve nonlinear generalized eigenvalue problem. Parametric studies are carried out to examine the effect of amplitude ratios, stacking sequences, cone angles, piezoelectric layers, applied voltages, circumferential length to thickness ratios, change in temperatures and support boundary conditions on the nonlinear natural frequency of laminated conical shell panels. The present outlined approach has been validated with those available results in the literature.
Security Flaws in an Efficient Pseudo-Random Number Generator for Low-Power Environments
Peris-Lopez, Pedro; Hernandez-Castro, Julio C.; Tapiador, Juan M. E.; Millán, Enrique San; van der Lubbe, Jan C. A.
In 2004, Settharam and Rhee tackled the design of a lightweight Pseudo-Random Number Generator (PRNG) suitable for low-power environments (e.g. sensor networks, low-cost RFID tags). First, they explicitly fixed a set of requirements for this primitive. Then, they proposed a PRNG conforming to these requirements and using a free-running timer [9]. We analyze this primitive discovering important security faults. The proposed algorithm fails to pass even relatively non-stringent batteries of randomness such as ENT (i.e. a pseudorandom number sequence test program). We prove that their recommended PRNG has a very short period due to the flawed design of its core. The internal state can be easily revealed, compromising its backward and forward security. Additionally, the rekeying algorithm is defectively designed mainly related to the unpractical value proposed for this purpose.
Ekrami, Yasamin; Cook, Joseph S.
2011-01-01
In order to mitigate catastrophic failures on future generation space vehicles, engineers at the National Aeronautics and Space Administration have begun to integrate a novel crew abort systems that could pull a crew module away in case of an emergency at the launch pad or during ascent. The Max Launch Abort System (MLAS) is a recent test vehicle that was designed as an alternative to the baseline Orion Launch Abort System (LAS) to demonstrate the performance of a "tower-less" LAS configuration under abort conditions. The MLAS II test vehicle will execute a propulsive coast stabilization maneuver during abort to control the vehicles trajectory and thrust. To accomplish this, the spacecraft will integrate an Attitude Control System (ACS) with eight hypergolic monomethyl hydrazine liquid propulsion engines that are capable of operating in a quick pulsing mode. Two main elements of the ACS include a propellant distribution subsystem and a pressurization subsystem to regulate the flow of pressurized gas to the propellant tanks and the engines. The CAD assembly of the Attitude Control System (ACS) was configured and integrated into the Launch Abort Vehicle (LAV) design. A dynamic random vibration analysis was conducted on the Main Propulsion System (MPS) helium pressurization panels to assess the response of the panel and its components under increased gravitational acceleration loads during flight. The results indicated that the panels fundamental and natural frequencies were farther from the maximum Acceleration Spectral Density (ASD) vibrations which were in the range of 150-300 Hz. These values will direct how the components will be packaged in the vehicle to reduce the effects high gravitational loads.
International Nuclear Information System (INIS)
Maestrini, A.P.
1979-04-01
Several problems related to the application of the theory of random by means of state variables are studied. The well-known equations that define the propagation of the mean and the variance for linear and non-linear systems are first presented. The Monte Carlo method is next resorted to in order to determine the applicability of the hypothesis of a normally distributed output in case of linear systems subjected to non-Gaussian excitations. Finally, attention is focused on the properties of linear filters and modulation functions proposed to simulate seismic excitations as non stationary random processes. Acceleration spectra obtained by multiplying rms spectra by a constant factor are compared with design spectra suggested by several authors for various soil conditions. In every case, filter properties are given. (Author) [pt
Energy Technology Data Exchange (ETDEWEB)
Alekhin, S.A.; Chernov, V.S.; Denisenko, V.V.; Gorodnyanskiy, I.F.; Prokopov, L.I.; Tikhonov, Yu.P.
1983-01-01
The vibration mixer is proposed which contains a housing, vibration drive with rod installed in the upper part of the mixing mechanism made in the form of a hollow shaft with blades. In order to improve intensity of mixing and dispersion of the mud, the shaft with the blades is arranged on the rod of the vibrator and is equipped with a cam coupling whose drive disc is attached to the vibration rod. The rod is made helical, while the drive disc of the cam coupling is attached to the helical surface of the rod. In addition, the vibration mixer is equipped with perforated discs installed on the ends of the rods.
On the equilibrium state of a small system with random matrix coupling to its environment
Lebowitz, J. L.; Pastur, L.
2015-07-01
We consider a random matrix model of interaction between a small n-level system, S, and its environment, a N-level heat reservoir, R. The interaction between S and R is modeled by a tensor product of a fixed n× n matrix and a N× N Hermitian random matrix. We show that under certain ‘macroscopicity’ conditions on R, the reduced density matrix of the system {{ρ }S}=T{{r}R}ρ S\\cup R(eq), is given by ρ S(c)˜ exp \\{-β {{H}S}\\}, where HS is the Hamiltonian of the isolated system. This holds for all strengths of the interaction and thus gives some justification for using ρ S(c) to describe some nano-systems, like biopolymers, in equilibrium with their environment (Seifert 2012 Rep. Prog. Phys. 75 126001). Our results extend those obtained previously in (Lebowitz and Pastur 2004 J. Phys. A: Math. Gen. 37 1517-34) (Lebowitz et al 2007 Contemporary Mathematics (Providence RI: American Mathematical Society) pp 199-218) for a special two-level system.
Description of vibrational properties of random alloy ZnTe1-xSex within the percolation model
International Nuclear Information System (INIS)
Souhabi, Jihane; Chafi, Allal; Kassem, Mohammed; Nassour, Ayoub; Gleize, Jerome; Postnikov, A.V.; Hugel, J.; Pages, Olivier
2009-01-01
We discuss the classification of the phonon type behavior of semiconductor alloys as apparent in the Raman and infrared spectra, i.e. in terms of types (i) 1-bond→1-mode and (ii) 2-bond→1-mode (both covered by the Modified Random Element Isodisplacement model, operating at the macroscopic scale), and also (iii) the modified 2-mode type (exceptional), in the framework of the recent 1-bond→2-mode percolation model based on a description of the alloy disorder at the mesoscopic scale. The leading systems of types (i) and (iii), i.e., InGaAs and InGaP, respectively, were earlier shown to obey the percolation model. The aim of this work is to investigate whether the percolation model further extends to the leading system of the last type (ii), i.e. ZnTeSe. With this end in view, we perform a careful re-examination of the Raman and infrared spectra of this alloy, as available in the literature. Special attention is awarded to the discussion and modeling of the puzzling multi-mode infrared reflectivity spectra. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Single Event Upset in Static Random Access Memories in Atmospheric Neutron Environments
Arita, Yutaka; Takai, Mikio; Ogawa, Izumi; Kishimoto, Tadafumi
2003-07-01
Single-event upsets (SEUs) in a 0.4 μm 4 Mbit complementary metal oxide semiconductor (CMOS) static random access memory (SRAM) were investigated in various atmospheric neutron environments at sea level, at an altitude of 2612 m mountain, at an altitude of commercial airplane, and at an underground depth of 476 m. Neutron-induced SEUs increase with the increase in altitude. For a device with a borophosphosilicate glass (BPSG) film, SEU rates induced by thermal neutrons increase with the decrease in the cell charge of a memory cell. A thermal neutron-induced SEU is significant in SRAMs with a small cell charge. With the conditions of small cell charge, thermal neutron-induced SEUs account for 60% or more of the total neutron-induced SEUs. The SEU rate induced by atmospheric thermal neutrons can be estimated by an acceleration test using 252Cf.
Single event upset in static random access memories in atmospheric neutron environments
Arita, Y; Ogawa, I; Kishimoto, T
2003-01-01
Single-event upsets (SEUs) in a 0.4 mu m 4Mbit complementary metal oxide semiconductor (CMOS) static random access memory (SRAM) were investigated in various atmospheric neutron environments at sea level, at an altitude of 2612 m mountain, at an altitude of commercial airplane, and at an underground depth of 476m. Neutron-induced SEUs increase with the increase in altitude. For a device with a borophosphosilicate glass (BPSG) film, SEU rates induced by thermal neutrons increase with the decrease in the cell charge of a memory cell. A thermal neutron-induced SEU is significant in SRAMs with a small cell charge. With the conditions of small cell charge, thermal neutron-induced SEUs account for 60% or more of the total neutron-induced SEUs. The SEU rate induced by atmospheric thermal neutrons can be estimated by an acceleration test using sup 2 sup 5 sup 2 Cf. (author)
Directory of Open Access Journals (Sweden)
Flávia de Andrade e Souza Mazuchi
2018-03-01
Full Text Available Abstract AIMS (Stroke patients often present sensory-motor alterations and less aerobic capacity. Joint position sense, which is crucial for balance and gait control, is also affected in stroke patients. To compare the effect of two exercise training protocols (walking in deep water and on a treadmill on the knee position sense of stroke patients. METHODS This study was designed as a randomized controlled clinical trial. Twelve adults, who suffered a stroke at least one year prior to the start of the study, were randomly assigned to one of two groups: 1 pool group submitted to aerobic deep water walking training; and 2 the treadmill group which was submitted to aerobic walk on a treadmill. Measurements: The position sense, absolute error and variable error, of the knee joint was evaluated prior to and after nine weeks of aerobic training. RESULTS The pool group presented smaller absolute (13.9o versus 6.1o; p < 0.05 and variable (9.2o versus 3.9o; p < 0.05 errors after nine-weeks gait training than the treadmill group. CONCLUSIONS Nine-week aerobic exercise intervention in aquatic environment improved precision in the position sense of the knee joint of stroke patients, suggesting a possible application in a rehabilitation program.
Performance analysis of an acoustic time reversal system in dynamic and random oceanic environments
Khosla, Sunny Rajendra
This dissertation provides a theoretical framework along with specific performance predictions for an acoustic time reversal system in shallow oceanic environments. Acoustic time-reversal is a robust means of retrofocusing acoustic energy, in both time and space, to the original sound-source location without any information about the acoustic environment in which it is deployed. The effect of three performance limiting oceanic complexities addressed, include (i)ambient noise field, (ii)reflection and volume scattering from a deterministic soliton internal wave traveling on the thermocline between two water masses, and (iii)volume scattering from a random superposition of linear internal waves convecting a gradient in the sound speed profile. The performance analysis establishes acoustic time reversal to be a promising technology for a two-way communication system in an oceanic medium. For an omni-directional noisy environment a general formulation for the probability of retrofocusing is developed that includes the effect of the medium, accounts for the system hardware and the acoustic parameters. Monte-Carlo simulations in both, a free-space environment and a shallow-ocean sound-channel environment compare well with theory. A 41 element TRA spanning a shallow water depth of 60 m is predicted to return a 70% focal probability at -15 dB SNR for a source to array range of 6 km. Preliminary research with broadband signals suggest that they should outperform narrowband response in both free space and sound channel environments. The impact of the nonlinear solitary waves is addressed using a two-path Green's function to treat the presence of a flat thermocline, and the single scattering Born approximation to address scattering from the soliton internal wave. It is predicted that a stationary soliton located along ray turning paths between the source and the TRA can lead to both enhanced and degraded focal performance. Based on extension of previous research in wave
Directory of Open Access Journals (Sweden)
Yu-Chih Chen
2009-06-01
Conclusion: The results suggest that chest vibration may contribute to expectoration and thus improve lung collapse among ventilated patients in an ICU. Chest vibration nursing intervention is a safe and effective alternative pulmonary clearance method and can be used on patients who are on ventilators in ICUs.
DEFF Research Database (Denmark)
Sørensen, Herman
1997-01-01
Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board......Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board...
Vibration Considerations for Cryogenic Tanks Using Glass Bubbles Insulation
Werlink, Rudolph J.; Fesmire, James E.; Sass, Jared P.
2011-01-01
The use of glass bubbles as an efficient and practical thermal insulation system has been previously demonstrated in cryogenic storage tanks. One such example is a spherical, vacuum-jacketed liquid hydrogen vessel of 218,000 liter capacity where the boiloff rate has been reduced by approximately 50 percent. Further applications may include non-stationary tanks such as mobile tankers and tanks with extreme duty cycles or exposed to significant vibration environments. Space rocket launch events and mobile tanker life cycles represent two harsh cases of mechanical vibration exposure. A number of bulk fill insulation materials including glass bubbles, perlite powders, and aerogel granules were tested for vibration effects and mechanical behavior using a custom design holding fixture subjected to random vibration on an Electrodynamic Shaker. The settling effects for mixtures of insulation materials were also investigated. The vibration test results and granular particle analysis are presented with considerations and implications for future cryogenic tank applications. A thermal performance update on field demonstration testing of a 218,000 L liquid hydrogen storage tank, retrofitted with glass bubbles, is presented. KEYWORDS: Glass bubble, perlite, aerogel, insulation, liquid hydrogen, storage tank, mobile tanker, vibration.
Adaptive learning algorithms for vibration energy harvesting
International Nuclear Information System (INIS)
Ward, John K; Behrens, Sam
2008-01-01
By scavenging energy from their local environment, portable electronic devices such as MEMS devices, mobile phones, radios and wireless sensors can achieve greater run times with potentially lower weight. Vibration energy harvesting is one such approach where energy from parasitic vibrations can be converted into electrical energy through the use of piezoelectric and electromagnetic transducers. Parasitic vibrations come from a range of sources such as human movement, wind, seismic forces and traffic. Existing approaches to vibration energy harvesting typically utilize a rectifier circuit, which is tuned to the resonant frequency of the harvesting structure and the dominant frequency of vibration. We have developed a novel approach to vibration energy harvesting, including adaptation to non-periodic vibrations so as to extract the maximum amount of vibration energy available. Experimental results of an experimental apparatus using an off-the-shelf transducer (i.e. speaker coil) show mechanical vibration to electrical energy conversion efficiencies of 27–34%
Unger, Marianne; Jelsma, Jennifer; Stark, Christina
2013-01-01
This study aimed to determine whether strengthening trunk muscles using vibration can improve posture and gait in children with spastic-type cerebral palsy (STCP). A total of 27 children (6-13 years) participated in a single-blinded pre-post crossover experimental trial. The 1-Minute Walk Test, 2D-posturography, ultrasound imaging and sit-ups in one minute were used to assess effect on gait, posture, resting abdominal muscle thickness and functional strength. Significant increase in distance walked (p posture, an increase in sit-ups executed (p posture were maintained at 4-weeks post-intervention. A trunk-targeted intervention using vibration can improve posture and gait in children with STCP without any known side effects. It is recommended that vibration and specific trunk strengthening is included in training or rehabilitation programmes. Effects of vibration on force generation and spasticity need further investigation.
Directory of Open Access Journals (Sweden)
Ali Bagherian
2016-01-01
Conclusion: It may be concluded that the cotton-roll vibration method can be more helpful than the routine topical anesthesia in reducing behavioral pain reactions in children during local anesthesia administration.
International Nuclear Information System (INIS)
Arnal, R.S.; Martin, G.V.; Gonzalez, J.L.M.-C.
1988-01-01
This paper studies the local vibrations of reactor components driven by Gaussian coloured and white forces, when nonlinear vibrations arise. We study also the important problem of noise sources, modelization and the noise propagation through the neutron field using the discrete ordinates transport theory. Finally, we study the effect of the neutron field upon the PSD (power spectral density) of the noise source and we analyse the problem of fitting neutron noise experimental data to perform pattern recognition analysis. (author)
Emergent dynamics of Cucker-Smale flocking particles in a random environment
Ha, Seung-Yeal; Jeong, Jiin; Noh, Se Eun; Xiao, Qinghua; Zhang, Xiongtao
2017-02-01
We present a new kinetic Cucker-Smale-Fokker-Planck (CS-FP) type equation with a degenerate diffusion, which describes the dynamics for an ensemble of infinitely many Cucker-Smale particles in a random environment. The asymptotic dynamics of the CS-FP equation exhibits a threshold-like phenomenon depending on the relative strength between the coupling strength and the noise strength. In the small coupling regime, the noise effect becomes dominant, which induces the velocity variance to increase to infinity exponentially fast. In contrast, the velocity alignment effect is strong in the large coupling regime, and the velocity variance tends to zero exponentially fast. We present the global existence of classical solutions to the CS-FP equation for a sufficiently smooth initial datum without smallness in its size. For the kinetic CS-FP equation with a metric dependent communication weight, we provide a uniform-in-time mean-field limit from the stochastic CS-model to the kinetic CS-FP equation without convergence rate.
DEFF Research Database (Denmark)
Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen
2012-01-01
In this paper we describe a field study conducted with a wearable vibration belt where we test to determine the vibration intensity sensitivity ranges on a large diverse group of participants with evenly distributed ages and...
Nokes, L D; Thorne, G C
1988-01-01
Measurements of various mechanical properties of skeletal material using vibration techniques have been reported. The purposes of such investigations include the monitoring of pathogenic disorders such as osteoporosis, the rate and extent of fracture healing, and the status of internal fixations. Early investigations pioneered the application of conventional vibration measurement equipment to biological systems. The more recent advent of the microcomputer has made available to research groups more sophisticated techniques for data acquisition and analysis. The economical advantages of such equipment has led to the development of portable research instrumentation which lends itself to use in a clinical environment. This review article reports on the developments and progression of the various vibrational techniques and theories as applied to musculoskeletal systems.
Malagnini, Luca; Dreger, Douglas S.
2016-07-01
Although optimal, computing the moment tensor solution is not always a viable option for the calculation of the size of an earthquake, especially for small events (say, below Mw 2.0). Here we show an alternative approach to the calculation of the moment-rate spectra of small earthquakes, and thus of their scalar moments, that uses a network-based calibration of crustal wave propagation. The method works best when applied to a relatively small crustal volume containing both the seismic sources and the recording sites. In this study we present the calibration of the crustal volume monitored by the High-Resolution Seismic Network (HRSN), along the San Andreas Fault (SAF) at Parkfield. After the quantification of the attenuation parameters within the crustal volume under investigation, we proceed to the spectral correction of the observed Fourier amplitude spectra for the 100 largest events in our data set. Multiple estimates of seismic moment for the all events (1811 events total) are obtained by calculating the ratio of rms-averaged spectral quantities based on the peak values of the ground velocity in the time domain, as they are observed in narrowband-filtered time-series. The mathematical operations allowing the described spectral ratios are obtained from Random Vibration Theory (RVT). Due to the optimal conditions of the HRSN, in terms of signal-to-noise ratios, our network-based calibration allows the accurate calculation of seismic moments down to Mw < 0. However, because the HRSN is equipped only with borehole instruments, we define a frequency-dependent Generalized Free-Surface Effect (GFSE), to be used instead of the usual free-surface constant F = 2. Our spectral corrections at Parkfield need a different GFSE for each side of the SAF, which can be quantified by means of the analysis of synthetic seismograms. The importance of the GFSE of borehole instruments increases for decreasing earthquake's size because for smaller earthquakes the bandwidth available
Zhong, Zhao-Ming; Wu, Xiu-Hua; Huang, Zhi-Ping; Li, Wei; Ding, Ruo-Ting; Yu, Hui; Chen, Jian-Ting
2014-01-01
Background Alendronate (ALE) is a conventional drug used to treat osteoporosis. Low-magnitude whole-body vibration (WBV) exercise has been developed as a potential treatment for osteoporosis. The aim of this study was to investigate whether low-magnitude WBV could enhance the protective effect of ALE on bone properties in ovariectomized rats. Methods A total of 128 Sprague-Dawley rats were randomly divided into five groups (SHAM, OVX+VEH, OVX+WBV, OVX + ALE, OVX+WBV+ALE). The level of WBV applied was 0.3 g at 45–55 Hz for 20 min/day, 5 day/week and for 3 months. ALE was administered in dose of 1 mg/Kg once a week. Every four weeks eight rats from each group were sacrificed and their blood and both tibiae were harvested. The expression of osteocalcin and CTX in serum was measured by enzyme-linked immunosorbent assay (ELISA) and the tibiae were subjected to metaphyseal three-point bending and μCT analysis. Results Osteocalcin rose after ovariectomy and was not appreciably changed by either alendronate or WBV alone or in combination. Alendronate treatment significantly prevented an increase in CTX. WBV alone treatment did not alter this effect. Compared with the OVX+WBV group, nearly all tested indices such as the BV/TV, TV apparent, Tb.N, Tb.Th, and Conn.D were higher in the OVX+ALE group at week 12.Compared with the OVX+WBV group, certain tested indices such as BV/TV, TV apparent, Tb.N, and Con.D, were higher in the OVX+WBV+ALE group at week 12. At week 12, tibiae treated with WBV+ALE exhibited a significantly higher Fmax compared to the OVX+VEH group, and a significant difference was also found in energy absorption between the OVX+WBV+ALE and OVX+VEH groups. Conclusions Compared with the WBV, ALE was more effective at preventing bone loss and improved the trabecular architecture. However, WBV enhanced the effect of alendronate in ovariectomized rats by inducing further improvements in trabecular architecture. PMID:24796785
DEFF Research Database (Denmark)
Jepsen, Ditte Beck; Ryg, Jesper; Jørgensen, Niklas Rye
2018-01-01
Background: PaVOS is a randomized controlled trial (RCT) which aims to address the use of whole-body vibration exercise (WBV) in combination with parathyroid hormone 1-34 fragment teriparatide (PTH 1-34) treatment in patients with osteoporosis. PTH 1-34 is an effective but expensive anabolic...... fracture risk. Methods/design: PaVOS is a multicenter, assessor-blinded, superiority, two-armed randomized controlled trial (RCT). Postmenopausal women (n = 40, aged 50 years and older) starting taking PTH 1-34 from outpatient clinics will be randomized and assigned to a PTH 1-34 + WBV-exercise group...... (intervention group), or a PTH 1-34-alone group (control group). The intervention group will undergo WBV three sessions a week (12 min each, including 1:1 ratio of exercise: rest, 30 Hz, 1 mm amplitude) for a 12-month intervention period. Both the intervention and the control group will receive PTH 1...
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Vahid Behravesh
2012-08-01
Full Text Available Presented article is studying the issue of path navigating for numerous robots. Our presented approach is based on both priority and the robust method for path finding in repetitive dynamic. Presented model can be generally implementable and useable: We do not assume any restriction regarding the quantity of levels of freedom for robots, and robots of diverse kinds can be applied at the same time. We proposed a random method and hill-climbing technique in the area based on precedence plans, which is used to determine a solution to a given trajectory planning problem and to make less the extent of total track. Our method plans trajectories for particular robots in the setting-time scope. Therefore, in order to specifying the interval of constant objects similar to other robots and the extent of the tracks which is traversed. For measuring the hazard for robots to conflict with each other it applied a method based on probability of the movements of robots. This algorithm applied to real robots with successful results. The proposed method performed and judged on both real robots and in simulation. We performed sequence of100tests with 8 robots for comparing with coordination method and current performances are effective. However, maximizing the performance is still possible. These performances estimations performed on Windows operating system and 3GHz Intel Pentium IV with and compiles with GCC 3.4. We used our PCGA robot for all experiments. For a large environment of 19×15m2where we accomplished 40tests, our model is competent to plan high-quality paths in a severely short time (less than a second. Moreover, this article utilized lookup tables to keep expenses the formerly navigated robots made, increasing the number of robots don’t expand computation time.
Sierau, Susan; Dähne, Verena; Brand, Tilman; Kurtz, Vivien; von Klitzing, Kai; Jungmann, Tanja
2016-01-01
Based on the US Nurse-Family Partnership (NFP) program, the German home visiting program "Pro Kind" offered support for socially and financially disadvantaged first-time mothers from pregnancy until the children's second birthday. A multi-centered, longitudinal randomized controlled trial (RCT) was conducted to assess its effectiveness on mothers and children. A total of 755 women with multiple risk factors were recruited, 394 received regular home visits (treatment group), while 361 only had access to standard community services (control group). Program influences on family environment (e.g., quality of home, social support), maternal competencies (e.g., maternal self-efficacy, empathy, parenting style), and child development (e.g., cognitive and motor development) were assessed from mothers' program intake in pregnancy to children's second birthday based on self-reports in regular interviews and developmental tests. Generalized estimating equations (GEE) models showed small, but significant positive treatment effects on parental self-efficacy, and marginally significant effects on social support, and knowledge on child rearing. Maternal stress, self-efficacy, and feelings of attachment in the TG tend to show a more positive development over time. Subgroup effects were found for high-risk mothers in the TG, who reported more social support over time and, generally, had children with higher developmental scores compared to their CG counterparts. Post hoc analyses of implementation variables revealed the quality of the helping relationship as a significant indicator of treatment effects. Results are discussed in terms of implementation and public policy differences between NFP and Pro Kind.
Random recurrence equations and ruin in a Markov-dependent stochastic economic environment
DEFF Research Database (Denmark)
Collamore, Jeffrey F.
2009-01-01
series models. Our results build upon work of Goldie, who has developed tail asymptotics applicable for independent sequences of random variables subject to a random recurrence equation. In contrast, we adopt a general approach based on the theory of Harris recurrent Markov chains and the associated...
Scaling Limit of Symmetric Random Walk in High-Contrast Periodic Environment
Piatnitski, A.; Zhizhina, E.
2017-11-01
The paper deals with the asymptotic properties of a symmetric random walk in a high contrast periodic medium in Z^d, d≥1. From the existing homogenization results it follows that under diffusive scaling the limit behaviour of this random walk need not be Markovian. The goal of this work is to show that if in addition to the coordinate of the random walk in Z^d we introduce an extra variable that characterizes the position of the random walk inside the period then the limit dynamics of this two-component process is Markov. We describe the limit process and observe that the components of the limit process are coupled. We also prove the convergence in the path space for the said random walk.
van den Hoorn, Wolbert; Kerr, Graham K.; van Dieën, Jaap H.; Hodges, Paul W.
2018-01-01
Aging is associated with changes in balance control and elderly take longer to adapt to changing sensory conditions, which may increase falls risk. Low amplitude calf muscle vibration stimulates local sensory afferents/receptors and affects sense of upright when applied in stance. It has been used
Uchiyama, Ayako; Odagiri, Yuko; Ohya, Yumiko; Takamiya, Tomoko; Inoue, Shigeru; Shimomitsu, Teruichi
2013-01-01
Improvement of psychosocial work environment has proved to be valuable for workers' mental health. However, limited evidence is available for the effectiveness of participatory interventions. The purpose of this study was to investigate the effect on mental health among nurses of a participatory intervention to improve the psychosocial work environment. A cluster randomized controlled trial was conducted in hospital settings. A total of 434 nurses in 24 units were randomly allocated to 11 intervention units (n=183) and 13 control units (n=218). A participatory program was provided to the intervention units for 6 months. Depressive symptoms as mental health status and psychosocial work environment, assessed by the Job Content Questionnaire, the Effort-Reward Imbalance Questionnaire, and the Quality Work Competence questionnaire, were measured before and immediately after the 6-month intervention by a self-administered questionnaire. No significant intervention effect was observed for mental health status. However, significant intervention effects were observed in psychosocial work environment aspects, such as Coworker Support (pwork environment, but not mental health, among Japanese nurses.
2009-01-01
Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.
Umesh P. Agarwal; Rajai Atalla
2010-01-01
Vibrational spectroscopy is an important tool in modern chemistry. In the past two decades, thanks to significant improvements in instrumentation and the development of new interpretive tools, it has become increasingly important for studies of lignin. This chapter presents the three important instrumental methods-Raman spectroscopy, infrared (IR) spectroscopy, and...
Smart accelerometer. [vibration damage detection
Bozeman, Richard J., Jr. (Inventor)
1994-01-01
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.
PREFACE: Vibrations at surfaces Vibrations at surfaces
Rahman, Talat S.
2011-12-01
Central Florida, Orlando, in March 2010. Several speakers at this meeting were invited to contribute to the special section in this issue. As is clear from the articles in this special section, the phenomenon of vibrations at surfaces continues to be a dynamic field of investigation. In fact, there is a resurgence of effort because the insights provided by surface dynamics are still fundamental to the development of an understanding of the microscopic factors that control surface structure formation, diffusion, reaction and structural stability. Examination of dynamics at surfaces thus complements and supplements the wealth of information that is obtained from real-space techniques such as scanning tunneling microscopy. Vibrational dynamics is, of course, not limited to surfaces. Surfaces are important since they provide immediate deviation from the bulk. They display how lack of symmetry can lead to new structures, new local atomic environments and new types of dynamical modes. Nanoparticles, large molecules and nanostructures of all types, in all kinds of local environments, provide further examples of regions of reduced symmetry and coordination, and hence display characteristic vibrational modes. Given the tremendous advance in the synthesis of a variety of nanostructures whose functionalization would pave the way for nanotechnology, there is even greater need to engage in experimental and theoretical techniques that help extract their vibrational dynamics. Such knowledge would enable a more complete understanding and characterization of these nanoscale systems than would otherwise be the case. The papers presented here provide excellent examples of the kind of information that is revealed by vibrations at surfaces. Vibrations at surface contents Poisoning and non-poisoning oxygen on Cu(410)L Vattuone, V Venugopal, T Kravchuk, M Smerieri, L Savio and M Rocca Modifying protein adsorption by layers of glutathione pre-adsorbed on Au(111)Anne Vallée, Vincent Humblot
Fatigue Damage Spectrum calculation in a Mission Synthesis procedure for Sine-on-Random excitations
International Nuclear Information System (INIS)
Angeli, Andrea; Troncossi, Marco; Cornelis, Bram
2016-01-01
In many real-life environments, certain mechanical and electronic components may be subjected to Sine-on-Random vibrations, i.e. excitations composed of random vibrations superimposed on deterministic (sinusoidal) contributions, in particular sine tones due to some rotating parts of the system (e.g. helicopters, engine-mounted components,...). These components must be designed to withstand the fatigue damage induced by the “composed” vibration environment, and qualification tests are advisable for the most critical ones. In the case of an accelerated qualification test, a proper test tailoring which starts from the real environment (measured vibration signals) and which preserves not only the accumulated fatigue damage but also the “nature” of the excitation (i.e. sinusoidal components plus random process) is important to obtain reliable results. In this paper, the classic time domain approach is taken as a reference for the comparison of different methods for the Fatigue Damage Spectrum (FDS) calculation in case of Sine-on-Random vibration environments. Then, a methodology to compute a Sine-on-Random specification based on a mission FDS is proposed. (paper)
International Nuclear Information System (INIS)
Li, C.T.; Klein, A.
1979-01-01
The theory of anharmonic nuclear vibrational motion (nonlinear equations-of-motion method) developed in the preceding paper is applied to atsup 60,62,64atNi, which exhibit one and two phonon quadrupole collective states. A model Hamiltonian consisting of a modified pairing plus quadrupole interaction is studied first by comparing the results of the nonlinear equations-of-motion method with those of an exact diagonalization. Contrary to popular opinion, the model chosen fails to produce a vibrational spectrum, except in the case of 60 Ni, and as a consequence, the nonlinear equations-of-motion method, designed specifically to describe vibrational spectra, accords well with the exact calculations only for this case. A simple method is then described, within the framework of the nonlinear equations-of-motion method, for refining the model Hamiltonian so as to bring it into accord with experiment. In practice, it is found that a simple additional parameter in the Hamiltonian suffices to yield descriptions of the quadrupole states in Ni isotopes comparable in precision to the most up-to-date versions (modified, adjusted, etc.) of the surface delta interaction model
DEFF Research Database (Denmark)
Valentini, Chiara
2017-01-01
The term environment refers to the internal and external context in which organizations operate. For some scholars, environment is defined as an arrangement of political, economic, social and cultural factors existing in a given context that have an impact on organizational processes and structures....... For others, environment is a generic term describing a large variety of stakeholders and how these interact and act upon organizations. Organizations and their environment are mutually interdependent and organizational communications are highly affected by the environment. This entry examines the origin...... and development of organization-environment interdependence, the nature of the concept of environment and its relevance for communication scholarships and activities....
International Nuclear Information System (INIS)
Alili, Smail; Rugh, Hans Henrik
2008-01-01
We consider a supercritical branching process in time-dependent environment ξ. We assume that the offspring distributions depend regularly (C k or real-analytically) on real parameters λ. We show that the extinction probability q λ (ξ), given the environment ξ 'inherits' this regularity whenever the offspring distributions satisfy a condition of contraction-type. Our proof makes use of the Poincaré metric on the complex unit disc and a real-analytic implicit function theorem
Nonlinear complexity behaviors of agent-based 3D Potts financial dynamics with random environments
Xing, Yani; Wang, Jun
2018-02-01
A new microscopic 3D Potts interaction financial price model is established in this work, to investigate the nonlinear complexity behaviors of stock markets. 3D Potts model, which extends the 2D Potts model to three-dimensional, is a cubic lattice model to explain the interaction behavior among the agents. In order to explore the complexity of real financial markets and the 3D Potts financial model, a new random coarse-grained Lempel-Ziv complexity is proposed to certain series, such as the price returns, the price volatilities, and the random time d-returns. Then the composite multiscale entropy (CMSE) method is applied to the intrinsic mode functions (IMFs) and the corresponding shuffled data to study the complexity behaviors. The empirical results indicate that the 3D financial model is feasible.
Flávia de Andrade e Souza Mazuchi; Aline Bigongiari; Juliana Valente Francica; Patricia Martins Franciulli; Luis Mochizuki; Joseph Hamill; Ulysses Fernandes Ervilha
2018-01-01
Abstract AIMS (Stroke patients often present sensory-motor alterations and less aerobic capacity. Joint position sense, which is crucial for balance and gait control, is also affected in stroke patients). To compare the effect of two exercise training protocols (walking in deep water and on a treadmill) on the knee position sense of stroke patients. METHODS This study was designed as a randomized controlled clinical trial. Twelve adults, who suffered a stroke at least one year prior to the ...
Lotka-Volterra systems in environments with randomly disordered temporal periodicity
Naess, Arvid; Dimentberg, Michael F.; Gaidai, Oleg
2008-08-01
A generalized Lotka-Volterra model for a pair of interacting populations of predators and prey is studied. The model accounts for the prey’s interspecies competition and therefore is asymptotically stable, whereas its oscillatory behavior is induced by temporal variations in environmental conditions simulated by those in the prey’s reproduction rate. Two models of the variations are considered, each of them combining randomness with “hidden” periodicity. The stationary joint probability density function (PDF) of the number of predators and prey is calculated numerically by the path integration (PI) method based on the use of characteristic functions and the fast Fourier transform. The numerical results match those for the asymptotic case of white-noise variations for which an analytical solution is available. Several examples are studied, with calculations of important characteristics of oscillations, for example the expected rate of up-crossings given the level of the predator number. The calculated PDFs may be of predominantly random (unimodal) or predominantly periodic nature (bimodal). Thus, the PI method has been demonstrated to be a powerful tool for studies of the dynamics of predator-prey pairs. The method captures the random oscillations as observed in nature, taking into account potential periodicity in the environmental conditions.
Extinction transition in stochastic population dynamics in a random, convective environment
International Nuclear Information System (INIS)
Juhász, Róbert
2013-01-01
Motivated by modeling the dynamics of a population living in a flowing medium where the environmental factors are random in space, we have studied an asymmetric variant of the one-dimensional contact process, where the quenched random reproduction rates are systematically greater in one direction than in the opposite one. The spatial disorder turns out to be a relevant perturbation but, according to results of Monte Carlo simulations, the behavior of the model at the extinction transition is different from the (infinite-randomness) critical behavior of the disordered symmetric contact process. Depending on the strength a of the asymmetry, the critical population drifts either with a finite velocity or with an asymptotically vanishing velocity as x(t) ∼ t μ(a) , where μ(a) < 1. Dynamical quantities are non-self-averaging at the extinction transition; the survival probability, for instance, shows multiscaling, i.e. it is characterized by a broad spectrum of effective exponents. For a sufficiently weak asymmetry, a Griffiths phase appears below the extinction transition, where the survival probability decays as a non-universal power of the time while, above the transition, another extended phase emerges, where the front of the population advances anomalously with a diffusion exponent continuously varying with the control parameter. (paper)
Theory And Working Of Noise And Vibration
International Nuclear Information System (INIS)
Jeong, Il Rok
1988-09-01
This book deals with theory of noise including physical property of noise like term and characteristic of sound, occurrence of sound, characteristic of noise pollution and main cause of occurrence of noise, technique of prevention of noise with noise reduction, construction guide for prevention of noise, and measure of interior noise. It also has the theory of vibration such as an introduction of vibration, and technology of prevention of vibration, official test method of environmental pollution, and summary of protection of the environment.
Compare, Angelo; Zarbo, Cristina; Marín, Elena; Meloni, Alessia; Rubio-Arias, Jacobo A; Berengüí, Rosendo; Grossi, Enzo; Shonin, Edo; Martini, Gianmaria; Alcaraz, Pedro E
2014-05-20
Evidence demonstrates that physical exercise and psychological wellbeing are closely interlinked, particularly in older-aged women. However, research investigating how different forms of exercise influence mental health in older-aged women is underdeveloped. A randomized controlled trial (N = 300) will assess the relative effectiveness of two different exercise programs (whole-body vibration and Multicomponent Training) for improving psychological wellbeing in older-aged women. The following outcomes will be assessed at three time points (that is, pre, post, and follow-up): psychological wellbeing, proactive attitude, quality of life, and happiness. Results will have important implications for preventing psychological and physiological disease in older-aged women and for managing health-related costs for this population group. Number NCT01966562 on Clinical Gov database the 8 October 2013.
Dissimilar Dynamics of Coupled Water Vibrations
Jansen, Thomas L. C.; Cringus, Dan; Pshenichnikov, Maxim S.
2009-01-01
Dissimilar dynamics of coupled stretch vibrations of a water molecule are revealed by two-dimensional, IR correlation spectroscopy. These are caused by essentially non-Gaussian fluctuations of the electric field exerted by the environment on the individual OH stretch vibrations. Non-Gaussian
Directory of Open Access Journals (Sweden)
Coleman Karen J
2012-06-01
Full Text Available Abstract Background The Healthy Options for Nutrition Environments in Schools (Healthy ONES study was an evidence-based public health (EBPH randomized group trial that adapted the Institute for Healthcare Improvement’s (IHI rapid improvement process model to implement school nutrition policy and environmental change. Methods A low-income school district volunteered for participation in the study. All schools in the district agreed to participate (elementary = 6, middle school = 2 and were randomly assigned within school type to intervention (n = 4 and control (n =4 conditions following a baseline environmental audit year. Intervention goals were to 1 eliminate unhealthy foods and beverages on campus, 2 develop nutrition services as the main source on campus for healthful eating (HE, and 3 promote school staff modeling of HE. Schools were followed across a baseline year and two intervention years. Longitudinal assessment of height and weight was conducted with second, third, and sixth grade children. Behavioral observation of the nutrition environment was used to index the amount of outside foods and beverages on campuses. Observations were made monthly in each targeted school environment and findings were presented as items per child per week. Results From an eligible 827 second, third, and sixth grade students, baseline height and weight were collected for 444 second and third grade and 135 sixth grade students (51% reach. Data were available for 73% of these enrolled students at the end of three years. Intervention school outside food and beverage items per child per week decreased over time and control school outside food and beverage items increased over time. The effects were especially pronounced for unhealthy foods and beverage items. Changes in rates of obesity for intervention school (28% baseline, 27% year 1, 30% year 2 were similar to those seen for control school (22% baseline, 22% year 1, 25% year 2 children
National Aeronautics and Space Administration — Ground vibration tests or modal surveys are routinely conducted to support flutter analysis for subsonic and supersonic vehicles. However, vibration testing...
International Nuclear Information System (INIS)
Sakairi, M.; Shimoyama, Y.; Nagasawa, D.
2008-01-01
A new type of electrochemical random signal (electrochemical noise) analysis technique was applied to localized corrosion of anodic oxide film formed 1100 aluminum alloy in 0.5 kmol/m 3 H 3 BO 4 /0.05 kmol/m 3 Na 2 B 4 O 7 with 0.01 kmol/m 3 NaCl. The effect of anodic oxide film structure, barrier type, porous type, and composite type on galvanic corrosion resistance was also examined. Before localized corrosion started, incubation period for pitting corrosion, both current and potential slightly change as initial value with time. The incubation period of porous type anodic oxide specimens are longer than that of barrier type anodic oxide specimens. While pitting corrosion, the current and potential were changed with fluctuations and the potential and the current fluctuations show a good correlation. The records of the current and potential were processed by calculating the power spectrum density (PSD) by the Fast Fourier Transform (FFT) method. The potential and current PSD decrease with increasing frequency, and the slopes are steeper than or equal to minus one (-1). This technique allows observation of electrochemical impedance changes during localized corrosion
Pure random search for ambient sensor distribution optimisation in a smart home environment.
Poland, Michael P; Nugent, Chris D; Wang, Hui; Chen, Liming
2011-01-01
Smart homes are living spaces facilitated with technology to allow individuals to remain in their own homes for longer, rather than be institutionalised. Sensors are the fundamental physical layer with any smart home, as the data they generate is used to inform decision support systems, facilitating appropriate actuator actions. Positioning of sensors is therefore a fundamental characteristic of a smart home. Contemporary smart home sensor distribution is aligned to either a) a total coverage approach; b) a human assessment approach. These methods for sensor arrangement are not data driven strategies, are unempirical and frequently irrational. This Study hypothesised that sensor deployment directed by an optimisation method that utilises inhabitants' spatial frequency data as the search space, would produce more optimal sensor distributions vs. the current method of sensor deployment by engineers. Seven human engineers were tasked to create sensor distributions based on perceived utility for 9 deployment scenarios. A Pure Random Search (PRS) algorithm was then tasked to create matched sensor distributions. The PRS method produced superior distributions in 98.4% of test cases (n=64) against human engineer instructed deployments when the engineers had no access to the spatial frequency data, and in 92.0% of test cases (n=64) when engineers had full access to these data. These results thus confirmed the hypothesis.
Theory of vibration protection
Karnovsky, Igor A
2016-01-01
This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...
The efficacy of airflow and seat vibration on reducing visually induced motion sickness.
D'Amour, Sarah; Bos, Jelte E; Keshavarz, Behrang
2017-09-01
Visually induced motion sickness (VIMS) is a well-known sensation in virtual environments and simulators, typically characterized by a variety of symptoms such as pallor, sweating, dizziness, fatigue, and/or nausea. Numerous methods to reduce VIMS have been previously introduced; however, a reliable countermeasure is still missing. In the present study, the effect of airflow and seat vibration to alleviate VIMS was investigated. Eighty-two participants were randomly assigned to one of four groups (airflow, vibration, combined airflow and vibration, and control) and then exposed to a 15 min long video of a bicycle ride shot from first-person view. VIMS was measured using the Fast Motion Sickness Scale (FMS) and the Simulator Sickness Questionnaire (SSQ). Results showed that the exposure of airflow significantly reduced VIMS, whereas the presence of seat vibration, in contrast, did not have an impact on VIMS. Additionally, we found that females reported higher FMS scores than males, however, this sex difference was not found in the SSQ scores. Our findings demonstrate that airflow can be an effective and easy-to-apply technique to reduce VIMS in virtual environments and simulators, while vibration applied to the seat is not a successful method.
Magnetoelectric coupling of a magnetoelectric flux gate sensor in vibration noise circumstance
Directory of Open Access Journals (Sweden)
Zhaoqiang Chu
2018-01-01
Full Text Available A magnetoelectric (ME flux gate sensor (MEFGS consisting of piezoelectric PMN-PT single crystals and ferromagnetic amorphous alloy ribbon in a self-differential configuration is featured with the ability of weak magnetic anomaly detection. Here, we further investigated its ME coupling and magnetic field detection performance in vibration noise circumstance, including constant frequency, impact, and random vibration noise. Experimental results show that the ME coupling coefficient of MEFGS is as high as 5700 V/cm*Oe at resonant frequency, which is several orders magnitude higher than previously reported differential ME sensors. It was also found that under constant and impact vibration noise circumstance, the noise reduction and attenuation factor of MEFGS are over 17 and 85.7%, respectively. This work is important for practical application of MEFGS in real environment.
Directory of Open Access Journals (Sweden)
Faggiano Fabrizio
2011-05-01
Full Text Available Abstract Background Although social environments may influence alcohol-related behaviours in youth, the relationship between neighbourhood socioeconomic context and effectiveness of school-based prevention against underage drinking has been insufficiently investigated. We study whether the social environment affects the impact of a new school-based prevention programme on alcohol use among European students. Methods During the school year 2004-2005, 7079 students 12-14 years of age from 143 schools in nine European centres participated in this cluster randomised controlled trial. Schools were randomly assigned to either control or a 12-session standardised curriculum based on the comprehensive social influence model. Randomisation was blocked within socioeconomic levels of the school environment. Alcohol use and alcohol-related problem behaviours were investigated through a self-completed anonymous questionnaire at baseline and 18 months thereafter. Data were analysed using multilevel models, separately by socioeconomic level. Results At baseline, adolescents in schools of low socioeconomic level were more likely to report problem drinking than other students. Participation in the programme was associated in this group with a decreased odds of reporting episodes of drunkenness (OR = 0.60, 95% CI = 0.44-0.83, intention to get drunk (OR = 0.60, 95% CI = 0.45-0.79, and marginally alcohol-related problem behaviours (OR = 0.70, 95% CI = 0.46-1.06. No significant programme's effects emerged for students in schools of medium or high socioeconomic level. Effects on frequency of alcohol consumption were also stronger among students in disadvantaged schools, although the estimates did not attain statistical significance in any subgroup. Conclusions It is plausible that comprehensive social influence programmes have a more favourable effect on problematic drinking among students in underprivileged social environments. Trial registration ISRCTN: ISRCTN
Optical fiber grating vibration sensor for vibration monitoring of hydraulic pump
Zhang, Zhengyi; Liu, Chuntong; Li, Hongcai; He, Zhenxin; Zhao, Xiaofeng
2017-06-01
In view of the existing electrical vibration monitoring traditional hydraulic pump vibration sensor, the high false alarm rate is susceptible to electromagnetic interference and is not easy to achieve long-term reliable monitoring, based on the design of a beam of the uniform strength structure of the fiber Bragg grating (FBG) vibration sensor. In this paper, based on the analysis of the vibration theory of the equal strength beam, the principle of FBG vibration tuning based on the equal intensity beam is derived. According to the practical application of the project, the structural dimensions of the equal strength beam are determined, and the optimization design of the vibrator is carried out. The finite element analysis of the sensor is carried out by ANSYS, and the first order resonant frequency is 94.739 Hz. The vibration test of the sensor is carried out by using the vibration frequency of 35 Hz and the vibration source of 50 Hz. The time domain and frequency domain analysis results of test data show that the sensor has good dynamic response characteristics, which can realize the accurate monitoring of the vibration frequency and meet the special requirements of vibration monitoring of hydraulic pump under specific environment.
Directory of Open Access Journals (Sweden)
Paweł Kiper
2014-01-01
Full Text Available Objectives. To study whether the reinforced feedback in virtual environment (RFVE is more effective than traditional rehabilitation (TR for the treatment of upper limb motor function after stroke, regardless of stroke etiology (i.e., ischemic, hemorrhagic. Design. Randomized controlled trial. Participants. Forty-four patients affected by stroke. Intervention. The patients were randomized into two groups: RFVE (N=23 and TR (N=21, and stratified according to stroke etiology. The RFVE treatment consisted of multidirectional exercises providing augmented feedback provided by virtual reality, while in the TR treatment the same exercises were provided without augmented feedbacks. Outcome Measures. Fugl-Meyer upper extremity scale (F-M UE, Functional Independence Measure scale (FIM, and kinematics parameters (speed, time, and peak. Results. The F-M UE (P=0.030, FIM (P=0.021, time (P=0.008, and peak (P=0.018, were significantly higher in the RFVE group after treatment, but not speed (P=0.140. The patients affected by hemorrhagic stroke significantly improved FIM (P=0.031, time (P=0.011, and peak (P=0.020 after treatment, whereas the patients affected by ischemic stroke improved significantly only speed (P=0.005 when treated by RFVE. Conclusion. These results indicated that some poststroke patients may benefit from RFVE program for the recovery of upper limb motor function. This trial is registered with NCT01955291.
Bostock, Sophie; Luik, Annemarie I; Espie, Colin A
2016-07-01
Evaluating digital cognitive behavioral therapy (dCBT) for insomnia in a workplace environment. Within a randomized controlled trial in a Fortune 500 company, we randomized 270 self-identified poor sleepers [180 M/90 F: mean age 33.6 years (23 to 56 years)] to dCBT (n = 135) or waiting list (WL, n = 135). dCBT comprised six online sessions delivered by an animated therapist. Major assessments were at baseline and posttreatment. Sleep Condition Indicator (SCI) scores were significantly higher for the dCBT group [interaction term: F (1,485) = 15.63, P < 0.0001], representing Cohen's d of 1.10 following dCBT (d = 0.34 for WL). On the Work Productivity and Impairment questionnaire, "presenteeism" demonstrated significant improvements following dCBT [F(1,485) = 10.99, P = 0.001: d = 0.64 for dCBT, d = 0.09 for WL]. Effects for "abseenteeism" failed to reach statistical significance (P = 0.101). dCBT is effective in improving sleep and work-based productivity in adults with insomnia.
Fundamental Vibration of Molecular Hydrogen
Dickenson, G. D.; Niu, M. L.; Salumbides, E. J.; Komasa, J.; Eikema, K. S. E.; Pachucki, K.; Ubachs, W.
2013-05-01
The fundamental ground tone vibration of H2, HD, and D2 is determined to an accuracy of 2×10-4cm-1 from Doppler-free laser spectroscopy in the collisionless environment of a molecular beam. This rotationless vibrational splitting is derived from the combination difference between electronic excitation from the X1Σg+, v=0, and v=1 levels to a common EF1Σg+, v=0 level. Agreement within 1σ between the experimental result and a full ab initio calculation provides a stringent test of quantum electrodynamics in a chemically bound system.
International Nuclear Information System (INIS)
Kwak, Mun Gyu; Na, Sung Su; Baek, Gwang Hyeon; Song, Chul Gi; Han, Sang Bo
2001-09-01
This book deals with vibration of machine which gives descriptions of free vibration using SDOF system, forced vibration using SDOF system, vibration of multi-degree of freedom system like introduction and normal form, distribution system such as introduction, free vibration of bar and practice problem, approximate solution like lumped approximations and Raleigh's quotient, engineering by intuition and experience, real problem and experimental method such as technology of signal, fourier transform analysis, frequency analysis and sensor and actuator.
Hilário, M.; Hollander, den W.Th.F.; Sidoravicius, V.; Soares dos Santos, R.; Teixeira, A.
2014-01-01
In this paper we study a random walk in a one-dimensional dynamic random environment consisting of a collection of independent particles performing simple symmetric random walks in a Poisson equilibrium with density ¿¿(0,8). At each step the random walk performs a nearest-neighbour jump, moving to
Enhanced vibration diagnostics using vibration signature analysis
International Nuclear Information System (INIS)
Ahmed, S.; Shehzad, K.; Zahoor, Y.; Mahmood, A.; Bibi, A.
2001-01-01
Symptoms will appear in equipment, as well as in human beings. when 'suffering from sickness. Symptoms of abnormality in equipment are vibration, noise, deformation, temperature, pressure, electric current, crack, wearing, leakage etc. these are called modes of failure. If the mode of failure is vibration then the vibration signature analysis can be effectively used in order to diagnose the machinery problems. Much valuable information is contained within these vibration 'Spectra' or 'Signatures' but is only of use if the analyst can unlock its 'Secrets'. This paper documents a vibration problem in the motor of a centrifugal pump (Type ETA). It focuses mainly on the roll of modern vibration monitoring system in problem analysis. The problem experienced was the motor unstability and noise due to high vibration. Using enhanced vibration signature data, the problem was analyzed. which suggested that the rotor eccentricity was the cause of excessive noise and vibration in the motor. In conclusion, advanced electronic monitoring and diagnostic systems provide powerful information for machine's condition assessment and problem analysis. Appropriate interpretation and use of this information is important for accurate and effective vibration analysis. (author)
Recent advances in micro-vibration isolation
Liu, Chunchuan; Jing, Xingjian; Daley, Steve; Li, Fengming
2015-05-01
Micro-vibration caused by disturbance sources onboard spacecraft can severely degrade the working environment of sensitive payloads. Some notable vibration control methods have been developed particularly for the suppression or isolation of micro-vibration over recent decades. Usually, passive isolation techniques are deployed in aerospace engineering. Active isolators, however, are often proposed to deal with the low frequency vibration that is common in spacecraft. Active/passive hybrid isolation has also been effectively used in some spacecraft structures for a number of years. In semi-active isolation systems, the inherent structural performance can be adjusted to deal with variation in the aerospace environment. This latter approach is potentially one of the most practical isolation techniques for micro-vibration isolation tasks. Some emerging advanced vibration isolation methods that exploit the benefits of nonlinearity have also been reported in the literature. This represents an interesting and highly promising approach for solving some challenging problems in the area. This paper serves as a state-of-the-art review of the vibration isolation theory and/or methods which were developed, mainly over the last decade, specifically for or potentially could be used for, micro-vibration control.
Shock and vibration protection of submerged jet impingement cooling systems: Theory and experiment
International Nuclear Information System (INIS)
Haji Hosseinloo, Ashkan; Tan, Siow Pin; Yap, Fook Fah; Toh, Kok Chuan
2014-01-01
In the recent years, advances in high power density electronics and computing systems have pushed towards more advanced thermal management technologies and higher-capacity cooling systems. Among different types of cooling systems, jet impingement technology has gained attention and been widely used in different industries for its adaptability, cooling uniformity, large heat capacity, and ease of its localization. However, these cooling systems may not function properly in dynamically harsh environment inherent in many applications such as land, sea and air transportation. In this research article, a novel double-chamber jet impingement cooling system is fabricated and its performance is studied in harsh environment. Using the authors' previous studies, isolators with optimum properties are selected to ruggedize the chassis containing the cooling chamber against shock and random vibration. Experiments are conducted on both hard-mounted and isolated chassis and the cooling performance of the system is assessed using the inlet, and impingement surface temperatures of the cooling chamber. The experimental results show the isolation system prevents any failure that otherwise would occur, and also does not compromise the thermal performance of the system. - Highlights: • A novel double-chamber jet impingement cooling system was designed and fabricated. • Comprehensive set of random vibration and shock tests are conducted. • The isolation system proved to protect the cooling system properly against mechanical failure. • Cooling system performance was not significantly affected by the input random vibration and shock
[Occupational standing vibration rate and vibrational diseases].
Karnaukh, N G; Vyshchipan, V F; Haumenko, B S
2003-12-01
Occupational standing vibration rate is proposed in evaluating a degree of impairment of an organism activity. It will allow more widely to introduce specification of quality and quantity in assessment of the development of vibrational disease. According out-patient and inpatient obtained data we have established criterial values of functional changes in accordance with accumulated occupational standing vibration rate. The nomogram was worked out for defining a risk of the development of vibrational disease in mine workers. This nomogram more objectively can help in diagnostics of the disease.
Phosphate vibrations as reporters of DNA hydration
Corcelli, Steven
The asymmetric phosphate stretch vibrational frequency is extraordinarily sensitive to its local solvent environment. Using density functional theory calculations on the model compound dimethyl phosphate, the asymmetric phosphate stretch vibrational frequency was found to shift linearly with the magnitude of an electric field along the symmetry axis of the PO2 moiety (i.e. the asymmetric phosphate stretch is an excellent linear vibrational Stark effect probe). With this linear relationship established, asymmetric phosphate stretch vibrational frequencies were computed during the course of a molecular dynamics simulation of fully hydrated DNA. Moreover, contributions to shifts in the frequencies from subpopulations of water molecules (e.g. backbone, minor groove, major groove, etc.) were calculated to reveal how phosphate vibrations report the onset of DNA hydration in experiments that vary the relative humidity of non-condensing (dry) DNA samples.
Energy Technology Data Exchange (ETDEWEB)
Souhabi, Jihane; Chafi, Allal; Kassem, Mohammed; Nassour, Ayoub; Gleize, Jerome; Postnikov, A.V.; Hugel, J.; Pages, Olivier [Laboratoire de Physique des Milieux Denses, Universite Paul Verlaine - Metz, 1 Bd Arago, 57070 Metz (France)
2009-05-15
We discuss the classification of the phonon type behavior of semiconductor alloys as apparent in the Raman and infrared spectra, i.e. in terms of types (i) 1-bond{yields}1-mode and (ii) 2-bond{yields}1-mode (both covered by the Modified Random Element Isodisplacement model, operating at the macroscopic scale), and also (iii) the modified 2-mode type (exceptional), in the framework of the recent 1-bond{yields}2-mode percolation model based on a description of the alloy disorder at the mesoscopic scale. The leading systems of types (i) and (iii), i.e., InGaAs and InGaP, respectively, were earlier shown to obey the percolation model. The aim of this work is to investigate whether the percolation model further extends to the leading system of the last type (ii), i.e. ZnTeSe. With this end in view, we perform a careful re-examination of the Raman and infrared spectra of this alloy, as available in the literature. Special attention is awarded to the discussion and modeling of the puzzling multi-mode infrared reflectivity spectra. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Directory of Open Access Journals (Sweden)
Courtney D. Perry
2016-05-01
Full Text Available Women tend to gain weight at midlife (40–60 years increasing risk of obesity-related chronic diseases. Within specific eating occasions, needs related to the physical and social environment may result in less healthy eating behavior, which can lead to weight gain over time. The purpose of this study was to determine if a dietitian-delivered nutrition counseling intervention tailored to eating occasion needs could improve diet and prevent weight gain among midlife women over two years. A randomized controlled trial was conducted with healthy midlife women (n = 354 in one U.S. metropolitan area. The intervention group (n = 185 received ten hours of individual nutrition counseling from dietitians over six months, while women in a control group (n = 169 received no counseling. Measured height, weight and waist circumference, and dietary intakes were collected at baseline and every six months over two years. Mixed linear models were used to test for intervention effect on change in outcome variables over time. Dietary intakes of fruit, reduced/low-fat dairy foods and refined grains were significantly improved over time in the intervention compared to control group. However, the intervention had no effect on weight over time (p = 0.48. Nutrition counseling tailored to address eating occasion needs improved self-reported diet but did not significantly affect weight change.
Jung, Miyeon; Jonides, John; Northouse, Laurel; Berman, Marc G; Koelling, Todd M; Pressler, Susan J
In heart failure (HF), attention may be decreased because of lowered cerebral blood flow and increased attentional demands needed for self-care. Guided by the Attention Restoration Theory, the objective was to test the efficacy of the natural restorative environment (NRE) intervention on improving attention and mood among HF patients and healthy adults. A randomized crossover pilot study was conducted among 20 HF patients and an age- and education-matched comparison group of 20 healthy adults to test the efficacy of the NRE intervention compared with an active control intervention. Neuropsychological tests were administered to examine attention, particularly attention span, sustained attention, directed attention, and attention switching, at before and after the intervention. Mood was measured with the Positive and Negative Affect Schedule. No significant differences were found in attention and mood after the NRE intervention compared with the control intervention among the HF patients and the healthy adults. In analyses with HF patients and healthy adults combined (n = 40), significant differences were found. Compared with the control intervention, sustained attention improved after the NRE intervention (P = .001) regardless of the presence of HF. Compared with the healthy adults, HF patients performed significantly worse on attention switching after the control intervention (P = .045). The NRE intervention may be efficacious in improving sustained attention in HF patients. Future studies are needed to enhance the NRE intervention to be more efficacious and tailored for HF patients and test the efficacy in a larger sample of HF patients.
Directory of Open Access Journals (Sweden)
Mohamed Idhammad
2018-01-01
Full Text Available Cloud Computing services are often delivered through HTTP protocol. This facilitates access to services and reduces costs for both providers and end-users. However, this increases the vulnerabilities of the Cloud services face to HTTP DDoS attacks. HTTP request methods are often used to address web servers’ vulnerabilities and create multiple scenarios of HTTP DDoS attack such as Low and Slow or Flooding attacks. Existing HTTP DDoS detection systems are challenged by the big amounts of network traffic generated by these attacks, low detection accuracy, and high false positive rates. In this paper we present a detection system of HTTP DDoS attacks in a Cloud environment based on Information Theoretic Entropy and Random Forest ensemble learning algorithm. A time-based sliding window algorithm is used to estimate the entropy of the network header features of the incoming network traffic. When the estimated entropy exceeds its normal range the preprocessing and the classification tasks are triggered. To assess the proposed approach various experiments were performed on the CIDDS-001 public dataset. The proposed approach achieves satisfactory results with an accuracy of 99.54%, a FPR of 0.4%, and a running time of 18.5s.
Aldrin, Magne; Raastad, Ragnhild; Tvete, Ingunn Fride; Berild, Dag; Frigessi, Arnoldo; Leegaard, Truls; Monnet, Dominique L; Walberg, Mette; Müller, Fredrik
2013-04-15
Association between previous antibiotic use and emergence of antibiotic resistance has been reported for several microorganisms. The relationship has been extensively studied, and although the causes of antibiotic resistance are multi-factorial, clear evidence of antibiotic use as a major risk factor exists. Most studies are carried out in countries with high consumption of antibiotics and corresponding high levels of antibiotic resistance, and currently, little is known whether and at what level the associations are detectable in a low antibiotic consumption environment. We conduct an ecological, retrospective study aimed at determining the impact of antibiotic consumption on antibiotic-resistant Pseudomonas aeruginosa in three hospitals in Norway, a country with low levels of antibiotic use. We construct a sophisticated statistical model to capture such low signals. To reduce noise, we conduct our study at hospital ward level. We propose a random effect Poisson or binomial regression model, with a reparametrisation that allows us to reduce the number of parameters. Inference is likelihood based. Through scenario simulation, we study the potential effects of reduced or increased antibiotic use. Results clearly indicate that the effects of consumption on resistance are present under conditions with relatively low use of antibiotic agents. This strengthens the recommendation on prudent use of antibiotics, even when consumption is relatively low. Copyright © 2012 John Wiley & Sons, Ltd.
Beecher, L. C.; Williams, F. T.
1970-01-01
Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.
Berry, D.P.; Buckley, F.; Dillon, P.; Evans, R.D.; Rath, M.; Veerkamp, R.F.
2003-01-01
(Co)variance components for milk yield, body condition score (BCS), body weight (BW), BCS change and BW change over different herd-year mean milk yields (HMY) and nutritional environments (concentrate feeding level, grazing severity and silage quality) were estimated using a random regression model.
Nahavandi, Amir; Korayem, Moharam Habibnejad
2015-10-01
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.
Vibration Measurement with PULSE and DSPACE Equipment
Directory of Open Access Journals (Sweden)
Radim KLEČKA
2009-06-01
Full Text Available This contribution describes techniques and results of measurement with TIRA vibration generator. A method of experimental modal analysis allows next restore of vibration data. The goal is check validity of head expanders and screw connection. This process is based to using ME’scope environment. Another goal is check possibilities of dSPACE platform to vibration measurement. This task includes design of connection between dSPACE system and power amplifier, creating of graphical user interface and analyzing main configuration parameters to improve quality of drive signal.
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-.
International Nuclear Information System (INIS)
McIntyre, A.D.; Turnbull, R.G.H.
1992-01-01
The development of the hydrocarbon resources of the North Sea has resulted in both offshore and onshore environmental repercussions, involving the existing physical attributes of the sea and seabed, the coastline and adjoining land. The social and economic repercussions of the industry were equally widespread. The dramatic and speedy impact of the exploration and exploitation of the northern North Sea resources in the early 1970s, on the physical resources of Scotland was quickly realised together with the concern that any environmental and social damage to the physical and social fabric should be kept to a minimum. To this end, a wide range of research and other activities by central and local government, and other interested agencies was undertaken to extend existing knowledge on the marine and terrestrial environments that might be affected by the oil and gas industry. The outcome of these activities is summarized in this paper. The topics covered include a survey of the marine ecosystems of the North Sea, the fishing industry, the impact of oil pollution on seabirds and fish stocks, the ecology of the Scottish coastline and the impact of the petroleum industry on a selection of particular sites. (author)
Vibrational communication of subterranean rodents
HROUZKOVÁ, Ema
2012-01-01
This PhD. thesis focuses on the vibrational communication of subterranean mammals, in particular, vocal communication of bathyergids (Heliophobius argenteocinereus, Fukomys mechowii, Fukomys darlingi) and seismic communication of Tachyoryctes. We recorded and analyzed the vocalization of three species and discussed the physical parameters of their vocalization in relationship to the special underground acoustic environment. Moreover, social systems of African mole-rats range from solitary to ...
International Nuclear Information System (INIS)
Punia, D. T.; Donnermeyer, D.; Pope, M.
1984-01-01
An apparatus to monitor and record, for an industrial environment, two natural frequencies with respect to a ''seated spinal system'', namely, approximately 10 Hz and approximately 4 Hz, the natural resonant frequencies of the spine. Raw acceleration signals are amplified, conditioned and filtered to allow only 20 Hz or less to pass. The signals are then divided into two respective channels, namely, below 20 Hz and below 8 Hz, following parallel paths through an amplitude detector and through a zero crossover detector, rectifier and digital filter. In each path the amplitude detector controls a storage flip-flop, which enables an associated decade counter when amplitude criteria are met. The digital filter supplies an output, via an AND gate, to the counter if both amplitude and frequency criteria are met. Thus, a count is stored in the counter if both amplitude and frequency criteria are met. EAch channel has an LED display which can be turned on, after exposure, to display the number of events recorded
Effect of multi axis vibration and subject postures on sketching ...
African Journals Online (AJOL)
Sedentary activities such as reading, writing, sketching, etc. are affected due to the train vibrations. Therefore, the present study investigates the extent of perceived difficulty and distortion in a sketching task by seated subjects in two postures under low frequency, multi axial random vibrations. Thirty male voluntary subjects ...
Vibration of hydraulic machinery
Wu, Yulin; Liu, Shuhong; Dou, Hua-Shu; Qian, Zhongdong
2013-01-01
Vibration of Hydraulic Machinery deals with the vibration problem which has significant influence on the safety and reliable operation of hydraulic machinery. It provides new achievements and the latest developments in these areas, even in the basic areas of this subject. The present book covers the fundamentals of mechanical vibration and rotordynamics as well as their main numerical models and analysis methods for the vibration prediction. The mechanical and hydraulic excitations to the vibration are analyzed, and the pressure fluctuations induced by the unsteady turbulent flow is predicted in order to obtain the unsteady loads. This book also discusses the loads, constraint conditions and the elastic and damping characters of the mechanical system, the structure dynamic analysis, the rotor dynamic analysis and the system instability of hydraulic machines, including the illustration of monitoring system for the instability and the vibration in hydraulic units. All the problems are necessary for vibration pr...
Hewitt, Sue; Dong, Ren G; Welcome, Daniel E; McDowell, Thomas W
2015-03-01
For exposure to hand-transmitted vibration (HTV), personal protective equipment is sold in the form of anti-vibration (AV) gloves, but it remains unclear how much these gloves actually reduce vibration exposure or prevent the development of hand-arm vibration syndrome in the workplace. This commentary describes some of the issues that surround the classification of AV gloves, the assessment of their effectiveness and their applicability in the workplace. The available information shows that AV gloves are unreliable as devices for controlling HTV exposures. Other means of vibration control, such as using alternative production techniques, low-vibration machinery, routine preventative maintenance regimes, and controlling exposure durations are far more likely to deliver effective vibration reductions and should be implemented. Furthermore, AV gloves may introduce some adverse effects such as increasing grip force and reducing manual dexterity. Therefore, one should balance the benefits of AV gloves and their potential adverse effects if their use is considered. © Crown copyright 2014.
Application of system concept in vibration and noise reduction
Directory of Open Access Journals (Sweden)
SHENG Meiping
2017-08-01
Full Text Available Although certain vibration and noise control technologies are maturing, such as vibration absorption, vibration isolation, sound absorption and sound insulation, and new methods for specific frequency bands or special environments have been proposed unceasingly, there is still no guarantee that practical effective vibration and noise reduction can be obtained. An important constraint for vibration and noise reduction is the lack of a system concept, and the integrity and relevance of such practical systems as ship structure have not obtained enough attention. We have tried to use the system engineering theory in guiding vibration and noise reduction, and have already achieved certain effects. Based on the system concept, the noise control of a petroleum pipeline production workshop has been completed satisfactorily, and the abnormal noise source identification of an airplane has been accomplished successfully. We want to share our experience and suggestions to promote the popularization of the system engineering theory in vibration and noise control.
Review of Energy Harvesters Utilizing Bridge Vibrations
Directory of Open Access Journals (Sweden)
Farid Ullah Khan
2016-01-01
Full Text Available For health monitoring of bridges, wireless acceleration sensor nodes (WASNs are normally used. In bridge environment, several forms of energy are available for operating WASNs that include wind, solar, acoustic, and vibration energy. However, only bridge vibration has the tendency to be utilized for embedded WASNs application in bridge structures. This paper reports on the recent advancements in the area of vibration energy harvesters (VEHs utilizing bridge oscillations. The bridge vibration is narrowband (1 to 40 Hz with low acceleration levels (0.01 to 3.8 g. For utilization of bridge vibration, electromagnetic based vibration energy harvesters (EM-VEHs and piezoelectric based vibration energy harvesters (PE-VEHs have been developed. The power generation of the reported EM-VEHs is in the range from 0.7 to 1450000 μW. However, the power production by the developed PE-VEHs ranges from 0.6 to 7700 μW. The overall size of most of the bridge VEHs is quite comparable and is in mesoscale. The resonant frequencies of EM-VEHs are on the lower side (0.13 to 27 Hz in comparison to PE-VEHs (1 to 120 Hz. The power densities reported for these bridge VEHs range from 0.01 to 9539.5 μW/cm3 and are quite enough to operate most of the commercial WASNs.
Proceedings of second international conference on vibration engineering and technology of machinery
International Nuclear Information System (INIS)
2002-12-01
This volume of proceedings of the conference on vibration engineering cover a wide range of fields spanning diagnostics and condition monitoring, dynamics of rotors, dynamics of structures, computational methods, vehicle dynamics, vibration control, fluid-structure interaction, random and non-linear vibration. Many of these topics are also important to nuclear industry. The papers relevant to INIS are indexed separately
Directory of Open Access Journals (Sweden)
Rahu Mati
2008-08-01
Full Text Available Abstract Background Preventive drugs require long-term trials to show their effectiveness or harms and often a lot of changes occur during post-marketing studies. The purpose of this article is to describe the research process in a long-term randomized controlled trial and discuss the impact and consequences of changes in the research environment. Methods The Estonian Postmenopausal Hormone Therapy trial (EPHT, originally planned to continue for five years, was planned in co-operation with the Women's International Study of Long-Duration Oestrogen after Menopause (WISDOM in the UK. In addition to health outcomes, EPHT was specifically designed to study the impact of postmenopausal hormone therapy (HT on health services utilization. Results After EPHT recruited in 1999–2001 the Women's Health Initiative (WHI in the USA decided to stop the estrogen-progestin trial after a mean of 5.2 years in July 2002 because of increased risk of breast cancer and later in 2004 the estrogen-only trial because HT increased the risk of stroke, decreased the risk of hip fracture, and did not affect coronary heart disease incidence. WISDOM was halted in autumn 2002. These decisions had a major influence on EPHT. Conclusion Changes in Estonian society challenged EPHT to find a balance between the needs of achieving responses to the trial aims with a limited budget and simultaneously maintaining the safety of trial participants. Flexibility was the main key for success. Rapid changes are not limited only to transiting societies but are true also in developed countries and the risk must be included in planning all long-term trials. The role of ethical and data monitoring committees in situations with emerging new data from other studies needs specification. Longer funding for preventive trials and more flexibility in budgeting are mandatory. Who should prove the effectiveness of an (old drug for a new preventive indication? In preventive drug trials companies may
2002-01-01
Next week-end, the Geneva Science History Museum invites you to a Science Night under the banner of waves and vibrations. Scientists, artists and storytellers from more than forty institutes and local or regional associations will show that waves and vibrations form an integral part of our environment. You will be able to get in contact with the nature of waves through interactive exhibitions on sound and light and through hands-on demonstrations arranged in the Park of the Perle du Lac. On the CERN stand, you will be able to measure the speed of light with a bar of chocolate, and understand the scattering of waves with plastic ducks. Amazing, no? In addition to the stands, the Night will offer many other activities: reconstructions of experiments, a play, a concert of crystal glasses, an illuminated fountain, a house of spirits. More information Science Night, 6 and 7 July, Park of the Perle du Lac, Geneva
Vibrational analysis of a shipboard free electron laser beam path
Gallant, Bryan M.
2011-01-01
This thesis explores the deployment of a free electron laser (FEL) weapon system in a shipboard vibration environment. A concept solid model of a shipboard FEL is developed and used as a basis for a finite element model which is subjected to vibration simulation in MATLAB. Vibration input is obtained from ship shock trials data and wave excited motion data from ship motion simulation software. Emphasis is placed on the motion of electron beam path components of the FEL and the feasibility of ...
Bandshapes in vibrational spectroscopy
International Nuclear Information System (INIS)
Dijkman, F.G.
1978-01-01
A detailed account is given of the development of modern bandshape theories since 1965. An investigation into the relative contributions of statistical irreversible relaxation processes is described, for a series of molecules in which gradually the length of one molecular axis is increased. An investigation into the theoretical and experimental investigation of the broadening brought about by the effect of fluctuating intermolecular potentials on the vibrational frequency is also described. The effect of an intermolecular perturbative potential on anharmonic and Morse oscillators is discussed and the results are presented of a computation on the broadening of the vibrational band of some diatomic molecules in a rigid lattice type solvent. The broadening of the OH-stretching vibration in a number of aliphatic alcohols, the vibrational bandshapes of the acetylenic C-H stretching vibration and of the symmetric methyl stretching vibration are investigated. (Auth./ C.F.)
International Nuclear Information System (INIS)
Liu Meng; Wang Ke
2012-01-01
Highlights: ► Random population model with pulse toxicant input in polluted environments. ► Threshold between persistence and extinction is obtained. ► Different random noises have different effects on the persistence of the population. ► Impulsive period plays a key role in determining persistence of the population. ► Simulation figures support the analytical findings. - Abstract: Taking both white noises and colored noises into account, a stochastic single-species model with Markov switching and impulsive toxicant input in a polluted environment is proposed and investigated. Sufficient conditions for extinction, non-persistence in the mean, weak persistence and stochastic permanence are established. The threshold between weak persistence and extinction is obtained. Some simulation figures are introduced to illustrate the main results.
Physical model study of neutron noise induced by vibration of reactor internals
International Nuclear Information System (INIS)
Liu Jinhui; Gu Fangyu
1999-01-01
The author presents a physical model of neutron noise induced by reactor internals vibration in frequency domain. Based on system control theory, the reactor dynamic equations are coupled with random vibration equation, and non-linear terms are also taken into accounted while treating the random vibration. Experiments carried out on a zero-power reactor show that the model can be used to describe dynamic character of neutron noise induced by internals' vibration. The model establishes a method to help to determine internals'vibration features, and to diagnosis anomalies through neutron noise
Transfer vibration through spine
Benyovszky, Adam
2012-01-01
Transfer Vibration through Spine Abstract In the bachelor project we deal with the topic of Transfer Vibration through Spine. The problem of TVS is trying to be solved by the critical review method. We analyse some diagnostic methods and methods of treatment based on this principle. Close attention is paid to the method of Transfer Vibration through Spine that is being currently solved by The Research Institute of Thermomechanics in The Czech Academy of Sciences in cooperation with Faculty of...
Effects of Vibration Therapy in Pediatric Immunizations.
Benjamin, Arika L; Hendrix, Thomas J; Woody, Jacque L
2016-01-01
A randomized clinical trial of 100 children (52 boys, 48 girls) ages 2 months to 7 years was conducted to evaluate the effect of vibration therapy without cold analgesia on pain. A convenience sample was recruited at two sites: a publicly funded, free immunization clinic and a private group pediatric practice. Participants were randomly assigned to receive vibration therapy via a specialized vibrating device or standard care. All children regardless of intervention group were allowed to be distracted and soothed by the parent. Pain was evaluated using the FLACC score, which two nurses assessed at three points in time: prior to, during, and after the injection(s). Data were analyzed using a two-independent samples-paired t-test. Results show that vibration therapy had no effect on pain scores in the younger age groups studied (2 months ≤ 1 year, > 1 year ≤ 4 years). In the oldest age group (> 4 to 7 years of age), a heightened pain reading was found in the period from preinjection to post-injection periods (p = 0.045). These results indicate that the addition of vibration therapy (without cold analgesia) to standard soothing techniques is no more effective in reducing immunization pain than standard soothing techniques alone, and thus, is not indicated for use with immunization pain. Recommendations include further evaluation of interventions.
Quantum Monte Carlo for vibrating molecules
International Nuclear Information System (INIS)
Brown, W.R.; Lawrence Berkeley National Lab., CA
1996-08-01
Quantum Monte Carlo (QMC) has successfully computed the total electronic energies of atoms and molecules. The main goal of this work is to use correlation function quantum Monte Carlo (CFQMC) to compute the vibrational state energies of molecules given a potential energy surface (PES). In CFQMC, an ensemble of random walkers simulate the diffusion and branching processes of the imaginary-time time dependent Schroedinger equation in order to evaluate the matrix elements. The program QMCVIB was written to perform multi-state VMC and CFQMC calculations and employed for several calculations of the H 2 O and C 3 vibrational states, using 7 PES's, 3 trial wavefunction forms, two methods of non-linear basis function parameter optimization, and on both serial and parallel computers. In order to construct accurate trial wavefunctions different wavefunctions forms were required for H 2 O and C 3 . In order to construct accurate trial wavefunctions for C 3 , the non-linear parameters were optimized with respect to the sum of the energies of several low-lying vibrational states. In order to stabilize the statistical error estimates for C 3 the Monte Carlo data was collected into blocks. Accurate vibrational state energies were computed using both serial and parallel QMCVIB programs. Comparison of vibrational state energies computed from the three C 3 PES's suggested that a non-linear equilibrium geometry PES is the most accurate and that discrete potential representations may be used to conveniently determine vibrational state energies
Study on vibration behaviors of engineered barrier system
Energy Technology Data Exchange (ETDEWEB)
Mikoshiba, Tadashi; Ogawa, Nobuyuki; Minowa, Chikahiro [National Research Inst. for Earth Science and Disaster Prevention, Tsukuba, Ibaraki (Japan)
1999-02-01
Small engineered barrier model was mode and tested by vibrating with the random wave and the real earthquake wave. The wave observed at Kamaishi (N-S, N-W), Iwate Prefecture, in September 6, 1993, and Kobe (N-S) etc. were used as the real earthquake waves. The trial overpack showed non-linear characteristics (soft spring) by vibrating with the random wave. The pressure and acceleration of trial overpack and constraint container increased with increasing the vibration level of the real earthquake wave. The trial overpack moved the maximum 1.7 mm of displacement and 16 mm subsidence. The results showed both waves rocked the trialpack. (S.Y.)
Vibration and Acoustic Testing for Mars Micromission Spacecraft
Kern, Dennis L.; Scharton, Terry D.
1999-01-01
The objective of the Mars Micromission program being managed by the Jet Propulsion Laboratory (JPL) for NASA is to develop a common spacecraft that can carry telecommunications equipment and a variety of science payloads for exploration of Mars. The spacecraft will be capable of carrying robot landers and rovers, cameras, probes, balloons, gliders or aircraft, and telecommunications equipment to Mars at much lower cost than recent NASA Mars missions. The lightweight spacecraft (about 220 Kg mass) will be launched in a cooperative venture with CNES as a TWIN auxiliary payload on the Ariane 5 launch vehicle. Two or more Mars Micromission launches are planned for each Mars launch opportunity, which occur every 26 months. The Mars launch window for the first mission is November 1, 2002 through April 2003, which is planned to be a Mars airplane technology demonstration mission to coincide with the 100 year anniversary of the Kittyhawk flight. Several subsequent launches will create a telecommunications network orbiting Mars, which will provide for continuous communication with lenders and rovers on the Martian surface. Dedicated science payload flights to Mars are slated to start in 2005. This new cheaper and faster approach to Mars exploration calls for innovative approaches to the qualification of the Mars Micromission spacecraft for the Ariane 5 launch vibration and acoustic environments. JPL has in recent years implemented new approaches to spacecraft testing that may be effectively applied to the Mars Micromission. These include 1) force limited vibration testing, 2) combined loads, vibration and modal testing, and 3) direct acoustic testing. JPL has performed nearly 200 force limited vibration tests in the past 9 years; several of the tests were on spacecraft and large instruments, including the Cassini and Deep Space One spacecraft. Force limiting, which measures and limits the spacecraft base reaction force using triaxial force gages sandwiched between the
Mechanical vibration and shock analysis, sinusoidal vibration
Lalanne, Christian
2014-01-01
Everything engineers need to know about mechanical vibration and shock...in one authoritative reference work! This fully updated and revised 3rd edition addresses the entire field of mechanical vibration and shock as one of the most important types of load and stress applied to structures, machines and components in the real world. Examples include everything from the regular and predictable loads applied to turbines, motors or helicopters by the spinning of their constituent parts to the ability of buildings to withstand damage from wind loads or explosions, and the need for cars to m
Hydroelastic Vibrations of Ships
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher; Folsø, Rasmus
2002-01-01
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...
Surface vibrational spectroscopy
International Nuclear Information System (INIS)
Erskine, J.L.
1984-01-01
A brief review of recent studies which combine measurements of surface vibrational energies with lattice dynamical calculations is presented. These results suggest that surface vibrational spectroscopy offers interesting prospects for use as a molecular-level probe of surface geometry, adsorbate bond distances and molecular orientations
Gearbox vibration diagnostic analyzer
1992-01-01
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.
Handbook Of Noise And Vibration
International Nuclear Information System (INIS)
1995-12-01
This book is about noise and vibration. The first chapter has explanations of noise such as basic of sound, influence of noise, assessment of noise, measurement of prevention of noise and technology, case of noise measurement and soundproof. The second chapter describes vibration with outline, theory of vibration, interpretation of vibration, measurement for reduction of vibration, case of design of protection against vibration. It deals with related regulation and method of measurement.
Vibrations of rotating machinery
Matsushita, Osami; Kanki, Hiroshi; Kobayashi, Masao; Keogh, Patrick
2017-01-01
This book opens with an explanation of the vibrations of a single degree-of-freedom (dof) system for all beginners. Subsequently, vibration analysis of multi-dof systems is explained by modal analysis. Mode synthesis modeling is then introduced for system reduction, which aids understanding in a simplified manner of how complicated rotors behave. Rotor balancing techniques are offered for rigid and flexible rotors through several examples. Consideration of gyroscopic influences on the rotordynamics is then provided and vibration evaluation of a rotor-bearing system is emphasized in terms of forward and backward whirl rotor motions through eigenvalue (natural frequency and damping ratio) analysis. In addition to these rotordynamics concerning rotating shaft vibration measured in a stationary reference frame, blade vibrations are analyzed with Coriolis forces expressed in a rotating reference frame. Other phenomena that may be assessed in stationary and rotating reference frames include stability characteristic...
Birnbach, D J; King, D; Vlaev, I; Rosen, L F; Harvey, P D
2013-09-01
This study investigated the impact of a fresh scent on the rate of hand hygiene compliance (HHC) among novice healthcare providers. In all, 165 participants examined a standardized patient with one sample exposed to fresh scent (N = 79) and the other exposed to the standard environment (N = 86). Hand hygiene behaviours were tracked before patient contact using video surveillance. The standard environment group had an HHC rate of 51% whereas participants in the fresh scent group had a higher HHC rate of 80% (P behaviour may be subconsciously influenced by cues in the environment. © 2013 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.
Vibrational Spectroscopy of Chromatographic Interfaces
Energy Technology Data Exchange (ETDEWEB)
Jeanne E. Pemberton
2011-03-10
Chromatographic separations play a central role in DOE-supported fundamental research related to energy, biological systems, the environment, and nuclear science. The overall portfolio of research activities in the Separations and Analysis Program within the DOE Office of Basic Energy Sciences includes support for activities designed to develop a molecular-level understanding of the chemical processes that underlie separations for both large-scale and analytical-scale purposes. The research effort funded by this grant award was a continuation of DOE-supported research to develop vibrational spectroscopic methods to characterize the interfacial details of separations processes at a molecular level.
Fulkerson, Jayne A; Friend, Sarah; Horning, Melissa; Flattum, Colleen; Draxten, Michelle; Neumark-Sztainer, Dianne; Gurvich, Olga; Garwick, Ann; Story, Mary; Kubik, Martha Y
2018-02-01
Research has demonstrated a significant positive association between frequent family meals and children's dietary intake; however, the promotion of healthful family meals has not been rigorously tested for key food environment and nutrition-related behavioral outcomes in a randomized trial. To describe family home food environment and nutrition-related parent and child personal and behavioral outcomes of the Healthy Home Offerings via the Mealtime Environment Plus program, the first rigorously tested family meals intervention targeting childhood obesity prevention. Randomized controlled trial. Baseline, postintervention (12 months, 93% retention), and follow-up (21 months, 89% retention) data (surveys and dietary recalls) were collected. Children aged 8 to 12 years (N=160) and their parents were randomized to intervention (n=81) or control (n=79) groups. The intervention included five parent goal-setting calls and 10 monthly sessions delivered to families in community settings that focused on experiential nutrition activities and education, meal planning, cooking skill development, and reducing screen time. Family home food environment outcomes and nutrition-related child and parent personal and behavioral outcomes. Analyses used generalized linear mixed models. Primary comparisons were contrasts between intervention and control groups at postintervention and follow-up, with adjustments for child age and parent education. Compared with control parents, intervention parents showed greater improvement over time in scores of self-efficacy for identifying appropriate portion sizes, with significant differences in adjusted means at both post-intervention (P=0.002) and follow-up (P=0.01). Intervention children were less likely to consume at least one sugar-sweetened beverage daily at post-intervention than control children (P=0.04). The Healthy Home Offerings via the Mealtime Environment Plus program involved the entire family and targeted personal, behavioral, and
Directory of Open Access Journals (Sweden)
Kai Kang
2018-01-01
Full Text Available There is a growing concern that business enterprises focus primarily on their economic activities and ignore the impact of these activities on the environment and the society. This paper investigates a novel sustainable inventory-allocation planning model with carbon emissions and defective item disposal over multiple periods under a fuzzy random environment. In this paper, a carbon credit price and a carbon cap are proposed to demonstrate the effect of carbon emissions’ costs on the inventory-allocation network costs. The percentage of poor quality products from manufacturers that need to be rejected is assumed to be fuzzy random. Because of the complexity of the model, dynamic programming-based particle swarm optimization with multiple social learning structures, a DP-based GLNPSO, and a fuzzy random simulation are proposed to solve the model. A case is then given to demonstrate the efficiency and effectiveness of the proposed model and the DP-based GLNPSO algorithm. The results found that total costs across the inventory-allocation network varied with changes in the carbon cap and that carbon emissions’ reductions could be utilized to gain greater profits.
Vibration study of the APS magnet support assemblies
International Nuclear Information System (INIS)
Wambsganss, M.W.; Jendrzejczyk, J.A.; Chen, S.S.
1990-11-01
Stability of the positron closed orbit is a requirement for successful operation of the Advanced Photon Source. The fact that vibration of the storage ring quadrupole magnets can lead to distortion of the positron closed orbit and to potentially unacceptable beam emittance growth provides the motivation for the subject studies. Low frequency vibrations can be controlled with steering magnets using feedback systems, provided the vibration amplitudes are within the dynamic range of the controllers. High frequency vibration amplitudes, on the other hand, are out of the range of the controller and, therefore must be limited to ensure the emittance growth will not exceed a prescribed value. Vibration criteria were developed based on the requirement that emittance growth be limited to 10 percent. Recognizing that the quadrupole magnets have the most significant effect, three different scenarios were considered: vibration of a single quadrupole within the storage ring, random vibration of all the quadrupoles in the ring, and the hypothetical case of a plane wave sweeping across the site and the quadrupoles following the motion of the plane wave. The maximum allowable peak vibration amplitudes corresponding to these three vibration scenarios are given. The criteria associated with the passage of a plane wave is dependent on wavelength, or, alternatively, on frequency given the wave speed. The wave speed used is that measured as a part of the geotechnical investigation at the APS site
Silicon micromachined vibrating gyroscopes
Voss, Ralf
1997-09-01
This work gives an overview of silicon micromachined vibrating gyroscopes. Market perspectives and fields of application are pointed out. The advantage of using silicon micromachining is discussed and estimations of the desired performance, especially for automobiles are given. The general principle of vibrating gyroscopes is explained. Vibrating silicon gyroscopes can be divided into seven classes. for each class the characteristic principle is presented and examples are given. Finally a specific sensor, based on a tuning fork for automotive applications with a sensitivity of 250(mu) V/degrees is described in detail.
System Detects Vibrational Instabilities
Bozeman, Richard J., Jr.
1990-01-01
Sustained vibrations at two critical frequencies trigger diagnostic response or shutdown. Vibration-analyzing electronic system detects instabilities of combustion in rocket engine. Controls pulse-mode firing of engine and identifies vibrations above threshold amplitude at 5.9 and/or 12kHz. Adapted to other detection and/or control schemes involving simultaneous real-time detection of signals above or below preset amplitudes at two or more specified frequencies. Potential applications include rotating machinery and encoders and decoders in security systems.
Lanzani, Guglielmo; De Silvestri, Sandro
2007-01-01
Vibrational spectroscopy is a powerful investigation tool for a wide class of materials covering diverse areas in physics, chemistry and biology. The continuous development in the laser field regarding ultrashort pulse generation has led to the possibility of producing light pulses that can follow vibrational motion coupled to the electronic transitions in molecules and solids in real time. Aimed at researchers and graduate students using vibrational spectroscopy, this book provides both introductory chapters as well as more advanced contents reporting on recent progress. It also provides a good starting point for scientists seeking a sound introduction to ultrafast optics and spectroscopic techniques.
Vibration behavior of the artificial barrier system
International Nuclear Information System (INIS)
Mikoshiba, Tadashi; Ogawa, Nobuyuki; Nakamura, Izuru
2000-01-01
This study aims at production of a mimic specimen of artificial barrier, experimental elucidation of influence of seismic motion due to a vibration experiment on the artificial barrier system, and establishment of an evaluating method on its long-term behavior. The study has been carried out under a cooperative study of the National Research Institute for Earth Science and Disaster Prevention and the Japan Nuclear Cycle Development Institute. In 1998 fiscal year, an artificial barrier specimen initiated by crosscut road was produced, and their random wave and actual seismic wave vibrations were carried out to acquire their fundamental data. As a result of the both vibrations, it was found that in a Case 2 specimen of which buffer material was swelled by poured water, the material was integrated with a mimic over-pack to vibrate under judgement of eigen-frequency, maximum acceleration ratio, and so forth on the test results. And, in a Case 1 specimen, it was thought that the mimic over-pack showed an extreme non-linear performance (soft spring) because of reducing eigen-frequency with increase of its vibration level. (G.K.)
Vibration behavior of the artificial barrier system
Energy Technology Data Exchange (ETDEWEB)
Mikoshiba, Tadashi; Ogawa, Nobuyuki; Nakamura, Izuru [National Research Inst. for Earth sceince and Disaster Prevention (Japan)
2000-02-01
This study aims at production of a mimic specimen of artificial barrier, experimental elucidation of influence of seismic motion due to a vibration experiment on the artificial barrier system, and establishment of an evaluating method on its long-term behavior. The study has been carried out under a cooperative study of the National Research Institute for Earth Science and Disaster Prevention and the Japan Nuclear Cycle Development Institute. In 1998 fiscal year, an artificial barrier specimen initiated by crosscut road was produced, and their random wave and actual seismic wave vibrations were carried out to acquire their fundamental data. As a result of the both vibrations, it was found that in a Case 2 specimen of which buffer material was swelled by poured water, the material was integrated with a mimic over-pack to vibrate under judgement of eigen-frequency, maximum acceleration ratio, and so forth on the test results. And, in a Case 1 specimen, it was thought that the mimic over-pack showed an extreme non-linear performance (soft spring) because of reducing eigen-frequency with increase of its vibration level. (G.K.)
He, Xin; Shan, Meijing; Liu, Meng
2018-02-01
An n-species stochastic Lotka-Volterra cooperative model in a polluted environment is proposed and studied. For each species, sufficient conditions for extinction, non-persistence in the mean and weak persistence in the mean are established. The threshold between weak persistence in the mean and extinction is obtained. Several numerical figures are also worked out to validate the theoretical results.
Cermak, Sharon A.; Stein Duker, Leah I.; Williams, Marian E.; Dawson, Michael E.; Lane, Christianne J.; Polido, José C.
2015-01-01
This pilot and feasibility study examined the impact of a sensory adapted dental environment (SADE) to reduce distress, sensory discomfort, and perception of pain during oral prophylaxis for children with autism spectrum disorder (ASD). Participants were 44 children ages 6-12 (n = 22 typical, n = 22 ASD). In an experimental crossover design, each…
Verdaasdonk, E.G.G.; Dankelman, J.; Lange, J.F.; Stassen, L.P.S.
2007-01-01
Background- Laparoscopic suturing is one of the most difficult tasks in endoscopic surgery, requiring extensive training. The aim of this study was to determine the transfer validity of knot-tying training on a virtual-reality (VR) simulator to a realistic laparoscopic environment. Methods- Twenty
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 th...... theory is unchanged in comparison to the 3rd edition. Only a few errors have been corrected.......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...
Improved Laser Vibration Radar
National Research Council Canada - National Science Library
Hilaire, Pierre
1998-01-01
.... This thesis reconfigured an existing CO2 laboratory laser radar system that is capable of measuring the frequencies of vibration of a simulated target into a more compact and rugged form for field testing...
NIF Ambient Vibration Measurements
International Nuclear Information System (INIS)
Noble, C.R.; Hoehler, M.S.; S.C. Sommer
1999-01-01
LLNL has an ongoing research and development project that includes developing data acquisition systems with remote wireless communication for monitoring the vibrations of large civil engineering structures. In order to establish the capability of performing remote sensing over an extended period of time, the researchers needed to apply this technology to a real structure. The construction of the National Ignition Facility provided an opportunity to test the data acquisition system on a large structure to monitor whether the facility is remaining within the strict ambient vibration guidelines. This document will briefly discuss the NIF ambient vibration requirements and summarize the vibration measurements performed during the Spring and Summer of 1999. In addition, a brief description of the sensors and the data acquisition systems will be provided in Appendix B
Energy Technology Data Exchange (ETDEWEB)
Alekhin, S.A.; Denisenko, V.V.; Dzhalalov, M.G.; Kirichek, F.P.; Pitatel, Yu.A.; Prokopov, L.I.; Tikhonov, Yu.P.
1982-01-01
A vibration sieve is proposed which includes a vibration drive, a body and a screen installed on shock absorbers, a device for washing out the screen, and a subassembly for loading the material. To increase the operational reliability and effectiveness of the vibration sieve by improving the cleaning of the screen, the loading subassembly is equipped with a baffle with a lever which is hinged to it. The device for washing out the screen is made in the form of an electromagnet with a connecting rod, a switch and an eccentric, a friction ratchet mechanism and sprinkling systems. Here, the latter are interconnected, using a connecting rod, while the sprinkling system is installed on rollers under the screen. The electromagnetic switch is installed under the lever. The body is made with grooves for installing the sprinkling system. The vibration sieve is equipped with a switch which interacts with the connecting rod. The friction ratchet mechanism is equipped with a lug.
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...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....
Energy Technology Data Exchange (ETDEWEB)
Philip J. Reid
2009-09-21
The conference focuses on using vibrational spectroscopy to probe structure and dynamics of molecules in gases, liquids, and interfaces. The goal is to bring together a collection of researchers who share common interests and who will gain from discussing work at the forefront of several connected areas. The intent is to emphasize the insights and understanding that studies of vibrations provide about a variety of systems.
Identification of Damping from Structural Vibrations
DEFF Research Database (Denmark)
Bajric, Anela
Reliable predictions of the dynamic loads and the lifetime of structures are inﬂuenced by the limited accuracy concerning the level of structural damping. The mechanisms of damping cannot be derived analytically from ﬁrst principles, and in the design of structures the damping is therefore based...... on experience or estimated from measurements. This thesis consists of an extended summary and three papers which focus on enhanced methods for identiﬁcation of damping from random struc-tural vibrations. The developed methods are validated by stochastic simulations, experimental data and full-scale measurements...... which are representative of the vibrations in small and large-scale structures. The ﬁrst part of the thesis presents an automated procedure which is suitable for estimation of the natural frequencies and the modal damping ratios from random response of structures. The method can be incorporated within...
Vibration dynamics of single atomic nanocontacts
International Nuclear Information System (INIS)
Khater, A; Bourahla, B; Tigrine, R
2007-01-01
The motivation for this work is to introduce a model for an atomic nanocontact, whereby its mechanical properties can be analysed via the local spectra. The model system consists of two sets of triple parallel semi-infinite atomic chains joined by a single atom in between. We calculate the vibration spectra and the local densities of vibration states, in the harmonic approximation, for the irreducible set of sites that constitute the nanocontact domain. The nanocontact observables are numerically calculated for different cases of elastic hardening and softening, to investigate how the local dynamics can respond to changes in the microscopic environment on the domain. We have also calculated the phonon scattering and coherent conductance at the nanocontact, derived in a Landauer-Buettiker matrix approach. The analysis of the spectra, of the densities of vibration states, and of the phonon conductance, identifies characteristic features and demonstrates the central role of a core subset of sites in the nanocontact domain
Flow-induced vibration of helical coil compression springs
International Nuclear Information System (INIS)
Stokes, F.E.; King, R.A.
1983-01-01
Helical coil compression springs are used in some nuclear fuel assembly designs to maintain holddown and to accommodate thermal expansion. In the reactor environment, the springs are exposed to flowing water, elevated temperatures and pressures, and irradiation. Flow parallel to the longitudinal axis of the spring may excite the spring coils and cause vibration. The purpose of this investigation was to determine the flow-induced vibration (FIV) response characteristics of the helical coil compression springs. Experimental tests indicate that a helical coil spring responds like a single circular cylinder in cross-flow. Two FIV excitation mechanisms control spring vibration. Namely: 1) Turbulent Buffeting causes small amplitude vibration which increases as a function of velocity squared. 2) Vortex Shedding causes large amplitude vibration when the spring natural frequency and Strouhal frequency coincide. Several methods can be used to reduce or to prevent vortex shedding large amplitude vibrations. One method is compressing the spring to a coil pitch-to-diameter ratio of 2 thereby suppressing the vibration amplitude. Another involves modifying the spring geometry to alter its stiffness and frequency characteristics. These changes result in separation of the natural and Strouhal frequencies. With an understanding of how springs respond in the flowing water environment, the spring physical parameters can be designed to avoid large amplitude vibration. (orig.)
International Nuclear Information System (INIS)
Fu Geyan; Zhu Qirong
1998-11-01
It is pointed out that the main reason making nuclear power plants reactors leak is the vibration of internals of reactors. The factors which lead the vibration all have randomness and obscureness. The obscure reliability theory is introduced to the vibration system of internals of nuclear power reactor. Based on a quantity of designing and moving data, the obscure factors effecting the vibration reliability of the internals of nuclear power plant reactor are analyzed and the anti-vibration reliability criteria and the evaluating model are given. And the anti-vibration reliability measures are advanced from different quarters of the machine design and building, the thermohydraulics design, the control of reactivity, etc.. They may benefit the theory and practice for building and perfecting the vibration obscure reliability model of the reactor internals
Pierce, Brandon L; Tong, Lin; Argos, Maria; Gao, Jianjun; Farzana, Jasmine; Roy, Shantanu; Paul-Brutus, Rachelle; Rahaman, Ronald; Rakibuz-Zaman, Muhammad; Parvez, Faruque; Ahmed, Alauddin; Quasem, Iftekhar; Hore, Samar K; Alam, Shafiul; Islam, Tariqul; Harjes, Judith; Sarwar, Golam; Slavkovich, Vesna; Gamble, Mary V; Chen, Yu; Yunus, Mohammad; Rahman, Mahfuzar; Baron, John A; Graziano, Joseph H; Ahsan, Habibul
2013-12-01
Arsenic exposure through drinking water is a serious global health issue. Observational studies suggest that individuals who metabolize arsenic efficiently are at lower risk for toxicities such as arsenical skin lesions. Using two single nucleotide polymorphisms(SNPs) in the 10q24.32 region (near AS3MT) that show independent associations with metabolism efficiency, Mendelian randomization can be used to assess whether the association between metabolism efficiency and skin lesions is likely to be causal. Using data on 2060 arsenic-exposed Bangladeshi individuals, we estimated associations for two 10q24.32 SNPs with relative concentrations of three urinary arsenic species (representing metabolism efficiency): inorganic arsenic (iAs), monomethylarsonic acid(MMA) and dimethylarsinic acid (DMA). SNP-based predictions of iAs%, MMA% and DMA% were tested for association with skin lesion status among 2483 cases and 2857 controls. Causal odds ratios for skin lesions were 0.90 (95% confidence interval[CI]: 0.87, 0.95), 1.19 (CI: 1.10, 1.28) and 1.23 (CI: 1.12, 1.36)for a one standard deviation increase in DMA%, MMA% and iAs%,respectively. We demonstrated genotype-arsenic interaction, with metabolism-related variants showing stronger associations with skin lesion risk among individuals with high arsenic exposure (synergy index: 1.37; CI: 1.11, 1.62). We provide strong evidence for a causal relationship between arsenic metabolism efficiency and skin lesion risk. Mendelian randomization can be used to assess the causal role of arsenic exposure and metabolism in a wide array of health conditions.exposure and metabolism in a wide array of health conditions.Developing interventions that increase arsenic metabolism efficiency are likely to reduce the impact of arsenic exposure on health.
Vibrational characteristics and wear of fuel rods
International Nuclear Information System (INIS)
Schmugar, K.L.
1977-01-01
Fuel rod wear, due to vibration, is a continuing concern in the design of liquid-cooled reactors. In my report, the methodology and models that are used to predict fuel rod vibrational response and vibratory wear, in a light water reactor environment, are discussed. This methodology is being followed at present in the design of Westinghouse Nuclear Fuel. Fuel rod vibrations are expressed as the normal bending modes, and sources of rod vibration are examined with special emphasis on flow-induced mechanisms in the stable flow region. In a typical Westinghouse PWR fuel assembly design, each fuel rod is supported at multiple locations along the rod axis by a square-shaped 'grid cell'. For a fuel rod /grid support system, the development of small oscillatory motions, due to fluid flow at the rod/grid interface, results in material wear. A theoretical wear mode is developed using the Archard Theory of Adhesive Wear as the basis. Without question certainty, fretting wear becomes a serious problem if it progresses to the stage where the fuel cladding is penetrated and fuel is exposed to the coolant. Westinghouse fuel is designed to minimize fretting wear by limiting the relative motion between the fuel rod and its supports. The wear producing motion between the fuel rod and its supports occurs when the vibration amplitude exceeds the slippage threshold amplitude
Savolainen-Kopra, Carita; Haapakoski, Jaason; Peltola, Piia A; Ziegler, Thedi; Korpela, Terttu; Anttila, Pirjo; Amiryousefi, Ali; Huovinen, Pentti; Huvinen, Markku; Noronen, Heikki; Riikkala, Pia; Roivainen, Merja; Ruutu, Petri; Teirilä, Juha; Vartiainen, Erkki; Hovi, Tapani
2012-01-16
Hand hygiene is considered as an important means of infection control. We explored whether guided hand hygiene together with transmission-limiting behaviour reduces infection episodes and lost days of work in a common work environment in an open cluster-randomized 3-arm intervention trial. A total of 21 clusters (683 persons) were randomized to implement hand hygiene with soap and water (257 persons), with alcohol-based hand rub (202 persons), or to serve as a control (224 persons). Participants in both intervention arms also received standardized instructions on how to limit the transmission of infections. The intervention period (16 months) included the emergence of the 2009 influenza pandemic and the subsequent national hand hygiene campaign influencing also the control arm. In the total follow-up period there was a 6.7% reduction of infection episodes in the soap-and water arm (p = 0.04). Before the onset of the anti-pandemic campaign, a statistically significant (p = 0.002) difference in the mean occurrence of infection episodes was observed between the control (6.0 per year) and the soap-and-water arm (5.0 per year) but not between the control and the alcohol-rub arm (5.6 per year). Neither intervention had a decreasing effect on absence from work. We conclude that intensified hand hygiene using water and soap together with behavioural recommendations can reduce the occurrence of self-reported acute illnesses in common work environment. Surprisingly, the occurrence of reported sick leaves also increased in the soap-and water-arm. ClinicalTrials.gov: NCT00981877 The Finnish Work Environment Fund and the National Institute for Health and Welfare.
Directory of Open Access Journals (Sweden)
Savolainen-Kopra Carita
2012-01-01
Full Text Available Abstract Background Hand hygiene is considered as an important means of infection control. We explored whether guided hand hygiene together with transmission-limiting behaviour reduces infection episodes and lost days of work in a common work environment in an open cluster-randomized 3-arm intervention trial. Methods A total of 21 clusters (683 persons were randomized to implement hand hygiene with soap and water (257 persons, with alcohol-based hand rub (202 persons, or to serve as a control (224 persons. Participants in both intervention arms also received standardized instructions on how to limit the transmission of infections. The intervention period (16 months included the emergence of the 2009 influenza pandemic and the subsequent national hand hygiene campaign influencing also the control arm. Results In the total follow-up period there was a 6.7% reduction of infection episodes in the soap-and water arm (p = 0.04. Before the onset of the anti-pandemic campaign, a statistically significant (p = 0.002 difference in the mean occurrence of infection episodes was observed between the control (6.0 per year and the soap-and-water arm (5.0 per year but not between the control and the alcohol-rub arm (5.6 per year. Neither intervention had a decreasing effect on absence from work. Conclusions We conclude that intensified hand hygiene using water and soap together with behavioural recommendations can reduce the occurrence of self-reported acute illnesses in common work environment. Surprisingly, the occurrence of reported sick leaves also increased in the soap-and water-arm. Trial Registration ClinicalTrials.gov: NCT00981877 Source of funding The Finnish Work Environment Fund and the National Institute for Health and Welfare.
Two-phase flow induced parametric vibrations in structural systems
International Nuclear Information System (INIS)
Hara, Fumio
1980-01-01
This paper is divided into two parts concerning piping systems and a nuclear fuel pin system. The significant experimental results concerning the random vibration induced in an L-shaped pipe by air-water two-phase flow and the theoretical analysis of the vibration are described in the first part. It was clarified for the first time that the parametric excitation due to the periodic changes of system mass, centrifugal force and Coriolis force was the mechanism of exciting the vibration. Moreover, the experimental and theoretical analyses of the mechanism of exciting vibration by air-water two-phase flow in a straight, horizontal pipe were carried out, and the first natural frequency of the piping system was strongly related to the dominant frequency of void signals. The experimental results on the vibration of a nuclear fuel pin model in parallel air-water two-phase flow are reported in the latter part. The relations between vibrational strain variance and two-phase flow velocity or pressure fluctuation, and the frequency characteristics of vibrational strain variance were obtained. The theoretical analysis of the dynamic interaction between air-water two-phase flow and a fuel pin structure, and the vibrational instability of fuel pins in alternate air and water slugs or in large bubble flow are also reported. (Kako, I.)
Lendvay, Thomas S.; Brand, Timothy C.; White, Lee; Kowalewski, Timothy; Jonnadula, Saikiran; Mercer, Laina; Khorsand, Derek; Andros, Justin; Hannaford, Blake; Satava, Richard M.
2014-01-01
Background Pre-operative simulation “warm-up” has been shown to improve performance and reduce errors in novice and experienced surgeons, yet existing studies have only investigated conventional laparoscopy. We hypothesized a brief virtual reality (VR) robotic warm-up would enhance robotic task performance and reduce errors. Study Design In a two-center randomized trial, fifty-one residents and experienced minimally invasive surgery faculty in General Surgery, Urology, and Gynecology underwent a validated robotic surgery proficiency curriculum on a VR robotic simulator and on the da Vinci surgical robot. Once successfully achieving performance benchmarks, surgeons were randomized to either receive a 3-5 minute VR simulator warm-up or read a leisure book for 10 minutes prior to performing similar and dissimilar (intracorporeal suturing) robotic surgery tasks. The primary outcomes compared were task time, tool path length, economy of motion, technical and cognitive errors. Results Task time (-29.29sec, p=0.001, 95%CI-47.03,-11.56), path length (-79.87mm, p=0.014, 95%CI -144.48,-15.25), and cognitive errors were reduced in the warm-up group compared to the control group for similar tasks. Global technical errors in intracorporeal suturing (0.32, p=0.020, 95%CI 0.06,0.59) were reduced after the dissimilar VR task. When surgeons were stratified by prior robotic and laparoscopic clinical experience, the more experienced surgeons(n=17) demonstrated significant improvements from warm-up in task time (-53.5sec, p=0.001, 95%CI -83.9,-23.0) and economy of motion (0.63mm/sec, p=0.007, 95%CI 0.18,1.09), whereas improvement in these metrics was not statistically significantly appreciated in the less experienced cohort(n=34). Conclusions We observed a significant performance improvement and error reduction rate among surgeons of varying experience after VR warm-up for basic robotic surgery tasks. In addition, the VR warm-up reduced errors on a more complex task (robotic
Directory of Open Access Journals (Sweden)
Antonov N.V.
2016-01-01
Full Text Available We study effects of the random fluid motion on a system in a self-organized critical state. The latter is described by the continuous stochastic model proposed by Hwa and Kardar [Phys. Rev. Lett. 62: 1813 (1989]. The advecting velocity field is Gaussian, not correlated in time, with the pair correlation function of the form ∝ δ(t − t′/k⊥d-1+ξ , where k⊥ = |k⊥| and k⊥ is the component of the wave vector, perpendicular to a certain preferred direction – the d-dimensional generalization of the ensemble introduced by Avellaneda and Majda [Commun. Math. Phys. 131: 381 (1990]. Using the field theoretic renormalization group we show that, depending on the relation between the exponent ξ and the spatial dimension d, the system reveals different types of large-scale, long-time scaling behaviour, associated with the three possible fixed points of the renormalization group equations. They correspond to ordinary diffusion, to passively advected scalar field (the nonlinearity of the Hwa–Kardar model is irrelevant and to the “pure” Hwa–Kardar model (the advection is irrelevant. For the special case ξ = 2(4 − d/3 both the nonlinearity and the advection are important. The corresponding critical exponents are found exactly for all these cases.
Vibration transducer calibration techniques
Brinkley, D. J.
1980-09-01
Techniques for the calibration of vibration transducers used in the Aeronautical Quality Assurance Directorate of the British Ministry of Defence are presented. Following a review of the types of measurements necessary in the calibration of vibration transducers, the performance requirements of vibration transducers, which can be used to measure acceleration, velocity or vibration amplitude, are discussed, with particular attention given to the piezoelectric accelerometer. Techniques for the accurate measurement of sinusoidal vibration amplitude in reference-grade transducers are then considered, including the use of a position sensitive photocell and the use of a Michelson laser interferometer. Means of comparing the output of working-grade accelerometers with that of previously calibrated reference-grade devices are then outlined, with attention given to a method employing a capacitance bridge technique and a method to be used at temperatures between -50 and 200 C. Automatic calibration procedures developed to speed up the calibration process are outlined, and future possible extensions of system software are indicated.
Directory of Open Access Journals (Sweden)
Gu Wenbin
2015-01-01
Full Text Available Due to the lack of proper instrumentations and the difficulties in underwater measurements, the studies about water bottom vibration induced by underwater drilling blasting are seldom reported. In order to investigate the propagation and attenuation laws of blasting induced water bottom vibration, a water bottom vibration monitor was developed with consideration of the difficulties in underwater measurements. By means of this equipment, the actual water bottom vibration induced by underwater drilling blasting was measured in a field experiment. It shows that the water bottom vibration monitor could collect vibration signals quite effectively in underwater environments. The followed signal analysis shows that the characteristics of water bottom vibration and land ground vibration induced by the same underwater drilling blasting are quite different due to the different geological environments. The amplitude and frequency band of water bottom vibration both exceed those of land ground vibration. Water bottom vibration is mainly in low-frequency band that induced by blasting impact directly acts on rock. Besides the low-frequency component, land vibration contains another higher frequency band component that induced by followed water hammer wave acts on bank slope.
Effect of structural design on traffic-induced building vibrations
DEFF Research Database (Denmark)
Persson, Peter; Andersen, Lars Vabbersgaard; Persson, Kent
2017-01-01
Population growth and urbanization results in densified cities, where new buildings are being built closer to existing vibration sources such as road-, tram- and rail traffic. In addition, new transportation systems are constructed closer to existing buildings. Potential disturbing vibrations...... are one issue to consider in planning urban environment and densification of cities. Vibrations can be disturbing for humans but also for sensitive equipment in, for example, hospitals. In determining the risk for disturbing vibrations, the distance between the source and the receiver, the ground...... properties, and type and size of the building are governing factors. In the paper, a study is presented aiming at investigating the influence of various parameters of the building's structural design on vibration levels in the structure caused by ground surface loads, e.g. traffic. Parameters studied...
Karcher, Michael J
2008-06-01
The effect of providing youth school-based mentoring (SBM), in addition to other school-based support services, was examined with a sample of 516 predominately Latino students across 19 schools. Participants in a multi-component, school-based intervention program run by a youth development agency were randomly assigned to one of two conditions: (1) supportive services alone or (2) supportive services plus SBM. Compared to community-based mentoring, the duration of the SBM was brief (averaging eight meetings), partly because the agency experienced barriers to retaining mentors. Intent-to-treat (ITT) main effects of SBM were tested using hierarchical linear modeling (HLM) and revealed small, positive main effects of mentoring on self-reported connectedness to peers, self-esteem (global and present-oriented), and social support from friends, but not on several other measures, including grades and social skills. Three-way cross-level interactions of sex and school level (elementary, middle, and high school) revealed that elementary school boys and high school girls benefited the most from mentoring. Among elementary school boys, those in the mentoring condition reported higher social skills (empathy and cooperation), hopefulness, and connectedness both to school and to culturally different peers. Among high school girls, those mentored reported greater connectedness to culturally different peers, self-esteem, and support from friends. Findings suggest no or iatrogenic effects of mentoring for older boys and younger girls. Therefore, practitioners coordinating multi-component programs that include SBM would be wise to provide mentors to the youth most likely to benefit from SBM and bolster program practices that help to support and retain mentors.
Recovering Intrinsic Fragmental Vibrations Using the Generalized Subsystem Vibrational Analysis.
Tao, Yunwen; Tian, Chuan; Verma, Niraj; Zou, Wenli; Wang, Chao; Cremer, Dieter; Kraka, Elfi
2018-05-08
Normal vibrational modes are generally delocalized over the molecular system, which makes it difficult to assign certain vibrations to specific fragments or functional groups. We introduce a new approach, the Generalized Subsystem Vibrational Analysis (GSVA), to extract the intrinsic fragmental vibrations of any fragment/subsystem from the whole system via the evaluation of the corresponding effective Hessian matrix. The retention of the curvature information with regard to the potential energy surface for the effective Hessian matrix endows our approach with a concrete physical basis and enables the normal vibrational modes of different molecular systems to be legitimately comparable. Furthermore, the intrinsic fragmental vibrations act as a new link between the Konkoli-Cremer local vibrational modes and the normal vibrational modes.
Arnetz, J E; Hasson, H
2007-07-01
Lack of professional development opportunities among nursing staff is a major concern in elderly care and has been associated with work dissatisfaction and staff turnover. There is a lack of prospective, controlled studies evaluating the effects of educational interventions on nursing competence and work satisfaction. The aim of this study was to evaluate the possible effects of an educational "toolbox" intervention on nursing staff ratings of their competence, psychosocial work environment and overall work satisfaction. The study was a prospective, non-randomized, controlled intervention. Nursing staff in two municipal elderly care organizations in western Sweden. In an initial questionnaire survey, nursing staff in the intervention municipality described several areas in which they felt a need for competence development. Measurement instruments and educational materials for improving staff knowledge and work practices were then collated by researchers and managers in a "toolbox." Nursing staff ratings of their competence and work were measured pre and post-intervention by questionnaire. Staff ratings in the intervention municipality were compared to staff ratings in the reference municipality, where no toolbox was introduced. Nursing staff ratings of their competence and psychosocial work environment, including overall work satisfaction, improved significantly over time in the intervention municipality, compared to the reference group. Both competence and work environment ratings were largely unchanged among reference municipality staff. Multivariate analysis revealed a significant interaction effect between municipalities over time for nursing staff ratings of participation, leadership, performance feedback and skills' development. Staff ratings for these four scales improved significantly in the intervention municipality as compared to the reference municipality. Compared to a reference municipality, nursing staff ratings of their competence and the
Vibrational spectra of aminoacetonitrile
International Nuclear Information System (INIS)
Bak, B.; Hansen, E.L.; Nicolaisen, F.M.; Nielsen, O.F.
1975-01-01
The preparation of pure, stable aminoacetonitrile(1-amino, 1'-cyanomethane)CH 2 NH 2 CN (1) is described. The Raman spectrum, now complete, and a novel infrared spectrum extending over the 50-3600 cm -1 region are reported. A tentative normal vibration analysis is presented and supported by Raman and infrared data from the spectra of CH 2 NHDCN (2) and CH 2 ND 2 CN (3). The predominance of the trans rotamer may be attributed to intramolecular hydrogen bonding but this is too unimportant to influence the vibrational frequencies of gaseous 1, 2, and 3. However, large gas/liquid frequency shifts occur. (author)
Kaliski, S
2013-01-01
This book gives a comprehensive overview of wave phenomena in different media with interacting mechanical, electromagnetic and other fields. Equations describing wave propagation in linear and non-linear elastic media are followed by equations of rheological models, models with internal rotational degrees of freedom and non-local interactions. Equations for coupled fields: thermal, elastic, electromagnetic, piezoelectric, and magneto-spin with adequate boundary conditions are also included. Together with its companion volume Vibrations and Waves. Part A: Vibrations this work provides a wealth
DEFF Research Database (Denmark)
Nielsen, Søren R. K.
The present textbook has been written based on previous lecture notes for a course on stochastic vibration theory that is being given on the 9th semester at Aalborg University for M. Sc. students in structural engineering. The present 2nd edition of this textbook on linear stochastic vibration th...... theory is basically unchanged in comparison to the 1st edition. Only section 4.2 on single input - single output systems and chapter 6 on offshore structures have been modified in order to enhance the clearness....
Vibration Spectrum Analysis for Indicating Damage on Turbine and Steam Generator Amurang Unit 1
Directory of Open Access Journals (Sweden)
Beny Cahyono
2017-12-01
Full Text Available Maintenance on machines is a mandatory asset management activity to maintain asset reliability in order to reduce losses due to failure. 89% of defects have random failure mode, the proper maintenance method is predictive maintenance. Predictive maintenance object in this research is Steam Generator Amurang Unit 1, which is predictive maintenance is done through condition monitoring in the form of vibration analysis. The conducting vibration analysis on Amurang Unit 1 Steam Generator is because vibration analysis is very effective on rotating objects. Vibration analysis is predicting the damage based on the vibration spectrum, where the vibration spectrum is the result of separating time-based vibrations and simplifying them into vibrations based on their frequency domain. The transformation of time-domain-wave into frequency-domain-wave is using the application of FFT, namely AMS Machinery. The measurement of vibration value is done on turbine bearings and steam generator of Unit 1 Amurang using Turbine Supervisory Instrument and CSI 2600 instrument. The result of this research indicates that vibration spectrum from Unit 1 Amurang Power Plant indicating that there is rotating looseness, even though the vibration value does not require the Unit 1 Amurang Power Plant to stop operating (shut down. This rotating looseness, at some point, can produce some indications that similar with the unbalance. In order to avoid more severe vibrations, it is necessary to do inspection on the bearings in the Amurang Unit 1 Power Plant.
An Assessment of Using Vibrational Compaction of Calcined HLW and LLW in DWPF Canisters
International Nuclear Information System (INIS)
Yi, Yun-Bo; Amme, Robert C.; Shayer, Zeev
2008-01-01
Since 1963, the INEL has calcined almost 8 million gallons of liquid mixed waste and liquid high-level waste, converting it to some 1.1 million gallons of dry calcine (about 4275.0 m3), which consists of alumina-and zirconia-based calcine and zirconia-sodium blend calcine. In addition, if all existing and projected future liquid wastes are solidified, approximately 2,000 m3 of additional calcine will be produced primarily from sodium-bearing waste. Calcine is a more desirable material to store than liquid radioactive waste because it reduces volume, is much less corrosive, less chemically reactive, less mobile under most conditions, easier to monitor and more protective of human health and the environment. This paper describes the technical issue involved in the development of a feasible solution for further volume reduction of calcined nuclear waste for transportation and long term storage, using a standard DWPF canister. This will be accomplished by developing a process wherein the canisters are transported into a vibrational machine, for further volume reduction by about 35%. The random compaction experiments show that this volume reduction is achievable. The main goal of this paper is to demonstrate through computer modeling that it is feasible to use volume reduction vibrational machine without developing stress/strain forces that will weaken the canister integrity. Specifically, the paper presents preliminary results of the stress/strain analysis of the DWPF canister as a function of granular calcined height during the compaction and verifying that the integrity of the canister is not compromised. This preliminary study will lead to the development of better technology for safe compactions of nuclear waste that will have significant economical impact on nuclear waste storage and treatment. The preliminary results will guide us to find better solutions to the following questions: 1) What are the optimum locations and directions (vertical versus horizontal or
Xu, Jiuping
2014-01-01
This paper presents an extension of the multimode resource-constrained project scheduling problem for a large scale construction project where multiple parallel projects and a fuzzy random environment are considered. By taking into account the most typical goals in project management, a cost/weighted makespan/quality trade-off optimization model is constructed. To deal with the uncertainties, a hybrid crisp approach is used to transform the fuzzy random parameters into fuzzy variables that are subsequently defuzzified using an expected value operator with an optimistic-pessimistic index. Then a combinatorial-priority-based hybrid particle swarm optimization algorithm is developed to solve the proposed model, where the combinatorial particle swarm optimization and priority-based particle swarm optimization are designed to assign modes to activities and to schedule activities, respectively. Finally, the results and analysis of a practical example at a large scale hydropower construction project are presented to demonstrate the practicality and efficiency of the proposed model and optimization method. PMID:24550708
Xu, Jiuping; Feng, Cuiying
2014-01-01
This paper presents an extension of the multimode resource-constrained project scheduling problem for a large scale construction project where multiple parallel projects and a fuzzy random environment are considered. By taking into account the most typical goals in project management, a cost/weighted makespan/quality trade-off optimization model is constructed. To deal with the uncertainties, a hybrid crisp approach is used to transform the fuzzy random parameters into fuzzy variables that are subsequently defuzzified using an expected value operator with an optimistic-pessimistic index. Then a combinatorial-priority-based hybrid particle swarm optimization algorithm is developed to solve the proposed model, where the combinatorial particle swarm optimization and priority-based particle swarm optimization are designed to assign modes to activities and to schedule activities, respectively. Finally, the results and analysis of a practical example at a large scale hydropower construction project are presented to demonstrate the practicality and efficiency of the proposed model and optimization method.
Return to Flying Duties Following Centrifuge or Vibration Exposures
Scheuring, Richard A.; Clarke, Jonathan; Jones, Jeffrey A.
2009-01-01
Introduction: In an effort to determine the human performance limits for vibration in spacecraft being developed by NASA, astronauts were evaluated during a simulated launch profile in a centrifuge/vibration environment and separate vibration-only simulation. Current USAF and Army standards for return to flight following centrifuge exposures require 12-24 hours to pass before a crewmember may return to flying duties. There are no standards on vibration exposures and return to flying duties. Based on direct observation and provocative neurological testing of the astronauts, a new standard for return to flying duties following centrifuge and/or vibration exposures was established. Methods: 13 astronaut participants were exposed to simulated launch profiles in a + 3.5 Gx bias centrifuge/vibration environment and separately on a vibration table at the NASA-Ames Research Center. Each subject had complete neurological evaluations pre- and post-exposure for the centrifuge/vibration runs with the NASA neurological function rating scale (NFRS). Subjects who participated in the vibration-only exposures had video oculography performed with provocative maneuvers in addition to the NFRS. NFRS evaluations occurred immediately following each exposure and at 1 hour post-run. Astronauts who remained symptomatic at 1 hour had repeat NFRS performed at 1 hour intervals until the crewmember was asymptomatic. Results: Astronauts in the centrifuge/vibration study averaged a 3-5 point increase in NFRS scores immediately following exposure but returned to baseline 3 hours post-run. Subjects exposed to the vibration-only simulation had a 1-3 point increase following exposure and returned to baseline within 1-2 hours. Pre- and post- vibration exposure video oculography did not reveal any persistent ocular findings with provocative testing 1 hour post-exposure. Discussion: Based on direct observations and objective measurement of neurological function in astronauts following simulated launch
Hansson, J E; Eklund, L; Kihlberg, S; Ostergren, C E
1987-03-01
The main objective of the study was to find efficient hand tools which caused only minor vibration loading. Vibration measurements were carried out under standardised working conditions. The time during which car body repairers in seven companies were exposed to vibration was determined. Chisel hammers, impact wrenches, sanders and saws were the types of tools which generated the highest vibration accelerations. The average daily exposure at the different garages ranged from 22 to 70 min. The risk of vibration injury is currently rated as high. The difference between the highest and lowest levels of vibration was considerable in most tool categories. Therefore the choice of tool has a major impact on the magnitude of vibration exposure. The importance of choosing the right tools and working methods is discussed and a counselling service on vibration is proposed.
Evaluation of Bus Vibration Comfort Based on Passenger Crowdsourcing Mode
Directory of Open Access Journals (Sweden)
Hong Zhao
2016-01-01
Full Text Available Vibration comfort is an important factor affecting the quality of service (QoS of bus. In order to make people involved in supervising bus’s vibration comfort and improve passengers’ riding experience, a novel mode of passenger crowdsourcing is introduced. In this paper, comfort degree of bus vibration is calculated from bus’s vibration signals collected by passengers’ smartphones and sent through WiFi to the Boa web server which shows the vibration comfort on the LCD deployed in bus and maybe trigger alarm lamp when the vibration is beyond the threshold. Three challenges here have been overcome: firstly, space coordinate transformation algorithm is used to solve the constant drift of signals collected; secondly, a low-pass filter is designed to isolate gravity from signals real-timely via limited computing resources; thirdly, an embedded evaluation system is developed according to the calculation procedure specified by criterion ISO 2631-1997. Meanwhile, the model proposed is tested in a practical running environment, the vibration data in whole travel are recorded and analyzed offline. The results show that comfort degree of vibration obtained from the experimental system is identical with the truth, and this mode is proved to be effective.
Development of adaptive helicopter seat systems for aircrew vibration mitigation
Chen, Yong; Wickramasinghe, Viresh; Zimcik, David G.
2008-03-01
Helicopter aircrews are exposed to high levels of whole body vibration during flight. This paper presents the results of an investigation of adaptive seat mount approaches to reduce helicopter aircrew whole body vibration levels. A flight test was conducted on a four-blade helicopter and showed that the currently used passive seat systems were not able to provide satisfactory protection to the helicopter aircrew in both front-back and vertical directions. Long-term exposure to the measured whole body vibration environment may cause occupational health issues such as spine and neck strain injuries for aircrew. In order to address this issue, a novel adaptive seat mount concept was developed to mitigate the vibration levels transmitted to the aircrew body. For proof-of-concept demonstration, a miniature modal shaker was properly aligned between the cabin floor and the seat frame to provide adaptive actuation authority. Adaptive control laws were developed to reduce the vibration transmitted to the aircrew body, especially the helmet location in order to minimize neck and spine injuries. Closed-loop control test have been conducted on a full-scale helicopter seat with a mannequin configuration and a large mechanical shaker was used to provide representative helicopter vibration profiles to the seat frame. Significant vibration reductions to the vertical and front-back vibration modes have been achieved simultaneously, which verified the technical readiness of the adaptive mount approach for full-scale flight test on the vehicle.
Parametric analysis of protective grid flow induced vibration
Energy Technology Data Exchange (ETDEWEB)
Ryu, Jooyoung; Eom, Kyongbo; Jeon, Sangyoun; Suh, Jungmin [KEPCO NF Co., Daejeon (Korea, Republic of)
2012-10-15
Protective grid (P-grid) flow-induced vibration in a nuclear power reactor is one of the critical factors for the mechanical integrity of a nuclear fuel. The P-grid is located at the lower most position above the bottom nozzle of the nuclear fuel as shown in Fig. 1, and it is required for not only filtering debris, but also supporting fuel rods. On the other hand, P-grid working conditions installed in a nuclear fuel in a reactor are severe in terms of flow speed, temperature and pressure. Considering such a severe condition of P-grid's functional performance in working environment, excessive vibration could be developed. Furthermore, if the P-grid is exposed to high levels of excessive vibration over a long period of time, fatigue failure could be unavoidable. Therefore, it is important to reduce excessive vibration while maintaining P-grid's own functional performance. KEPCO Nuclear Fuel has developed a test facility - Investigation Flow-induced Vibration (INFINIT) - to study flow-induced vibration caused by flowing coolant at various flow rates. To investigate specific relationships between configuration of P-grid and flow-induced vibration characteristics, several types of the P-grids were tested in INFINIT facility. And, based on the test results through parametric studies, the flow-induced vibration characteristics could be analyzed, and critical design parameters were found.
Remote monitoring of vibrational information in spider webs
Mortimer, B.; Soler, A.; Siviour, C. R.; Vollrath, F.
2018-06-01
Spiders are fascinating model species to study information-acquisition strategies, with the web acting as an extension of the animal's body. Here, we compare the strategies of two orb-weaving spiders that acquire information through vibrations transmitted and filtered in the web. Whereas Araneus diadematus monitors web vibration directly on the web, Zygiella x-notata uses a signal thread to remotely monitor web vibration from a retreat, which gives added protection. We assess the implications of these two information-acquisition strategies on the quality of vibration information transfer, using laser Doppler vibrometry to measure vibrations of real webs and finite element analysis in computer models of webs. We observed that the signal thread imposed no biologically relevant time penalty for vibration propagation. However, loss of energy (attenuation) was a cost associated with remote monitoring via a signal thread. The findings have implications for the biological use of vibrations by spiders, including the mechanisms to locate and discriminate between vibration sources. We show that orb-weaver spiders are fascinating examples of organisms that modify their physical environment to shape their information-acquisition strategy.
Evidence of impaired learning during whole-body vibration
Sherwood, N.; Griffin, M. J.
1992-01-01
A study of the effects of whole-body vibration on learning and memory was conducted, in which a context-dependent experimental design was used. Forty subjects completed a simple associative learning task, half during exposure to 16 Hz whole-body sinusoidal vertical vibration at 2.0 m s -2 r.m.s. and half while static. The results show that the rates of learning of the two groups differed, with that of the vibrated subjects significantly impaired. A second session, one week later, indicated that information learnt in one vibration environment could be recalled equally well in a different environment, suggesting no context-dependent effects on memory processes.
Topology optimization of free vibrations of fiber laser packages
DEFF Research Database (Denmark)
Hansen, Lars Voxen
2005-01-01
The optimization problems described in the present paper are inspired by the problem of fiber laser package design for vibrating environments. The optical frequency of tuned fiber lasers glued to stiff packages is sensitive to acoustic or other mechanical vibrations. The paper presents a method...... for reducing this sensitivity by limiting the glue point movement on the package while using only a limited knowledge of vibrating external forces. By use of topology optimization a density distribution for the package is obtained, where the critical eigenmode of the package only effects a small elongation...
Automatic detection of atrial fibrillation in cardiac vibration signals.
Brueser, C; Diesel, J; Zink, M D H; Winter, S; Schauerte, P; Leonhardt, S
2013-01-01
We present a study on the feasibility of the automatic detection of atrial fibrillation (AF) from cardiac vibration signals (ballistocardiograms/BCGs) recorded by unobtrusive bedmounted sensors. The proposed system is intended as a screening and monitoring tool in home-healthcare applications and not as a replacement for ECG-based methods used in clinical environments. Based on BCG data recorded in a study with 10 AF patients, we evaluate and rank seven popular machine learning algorithms (naive Bayes, linear and quadratic discriminant analysis, support vector machines, random forests as well as bagged and boosted trees) for their performance in separating 30 s long BCG epochs into one of three classes: sinus rhythm, atrial fibrillation, and artifact. For each algorithm, feature subsets of a set of statistical time-frequency-domain and time-domain features were selected based on the mutual information between features and class labels as well as first- and second-order interactions among features. The classifiers were evaluated on a set of 856 epochs by means of 10-fold cross-validation. The best algorithm (random forests) achieved a Matthews correlation coefficient, mean sensitivity, and mean specificity of 0.921, 0.938, and 0.982, respectively.
Structural Stability and Vibration
DEFF Research Database (Denmark)
Wiggers, Sine Leergaard; Pedersen, Pauli
at the University of Southern Denmark, it reports on fundamental formulas and makes uses of graphical representation to promote understanding. Thanks to the emphasis put on analytical methods and numerical results, the book is meant to make students and engineers familiar with all fundamental equations...... and their derivation, thus stimulating them to write interactive and dynamic programs to analyze instability and vibrational modes....
Vibrational Spectroscopy and Astrobiology
Chaban, Galina M.; Kwak, D. (Technical Monitor)
2001-01-01
Role of vibrational spectroscopy in solving problems related to astrobiology will be discussed. Vibrational (infrared) spectroscopy is a very sensitive tool for identifying molecules. Theoretical approach used in this work is based on direct computation of anharmonic vibrational frequencies and intensities from electronic structure codes. One of the applications of this computational technique is possible identification of biological building blocks (amino acids, small peptides, DNA bases) in the interstellar medium (ISM). Identifying small biological molecules in the ISM is very important from the point of view of origin of life. Hybrid (quantum mechanics/molecular mechanics) theoretical techniques will be discussed that may allow to obtain accurate vibrational spectra of biomolecular building blocks and to create a database of spectroscopic signatures that can assist observations of these molecules in space. Another application of the direct computational spectroscopy technique is to help to design and analyze experimental observations of ice surfaces of one of the Jupiter's moons, Europa, that possibly contains hydrated salts. The presence of hydrated salts on the surface can be an indication of a subsurface ocean and the possible existence of life forms inhabiting such an ocean.
Indian Academy of Sciences (India)
The vibrating string problem is the source of much mathe- matics and physics. ... ing this science [mechanics],and the art of solving the problems pertaining to it, to .... used tools for finding maxima and minima of functions of several variables.
International Nuclear Information System (INIS)
Richards, D.J.W.
1977-01-01
The heat exchangers of various types are common items of plant in the generation and transmission of electricity. The amount of attention given to the flow-induced vibrations of heat exchangers by designers is usually related to the operational history of similar items of plant. Consequently, if a particular design procedure yields items of plant which behave in a satisfactory manner during their operational life, there is little incentive to improve or refine the design procedure. On the other hand, failures of heat exchangers clearly indicate deficiencies in the design procedures or in the data available to the designer. When such failures are attributable to flow-induced vibrations, the identification of the mechanisms involved is a prime importance. Ideally, basic research work provides the background understanding and the techniques necessary to be able to identify the important mechanisms. In practice, the investigation of a flow-induced vibration problem may identify the presence of mechanisms but may not be able to quantify their effects adequately. In these circumstances the need for additional work is established and the objectives of the research programme emerge. The purpose of this paper is to outline the background to the current research programme at C.E.R.L. on heat exchanger vibration
DEFF Research Database (Denmark)
Jönsson, Jeppe; Hansen, Lars Pilegaard
1994-01-01
work has been done on the measurement of the exact load functions and related reponse analysis. A recent work using a spectral description has been performed by Per-Erik Erikson and includes a good literature survey. Bachmann and Ammann give a good overview of vibrations caused by human activity. Other...
Energy Technology Data Exchange (ETDEWEB)
Richards, D J.W. [CERL, CEGB, Leatherhead, Surrey (United Kingdom)
1977-12-01
The heat exchangers of various types are common items of plant in the generation and transmission of electricity. The amount of attention given to the flow-induced vibrations of heat exchangers by designers is usually related to the operational history of similar items of plant. Consequently, if a particular design procedure yields items of plant which behave in a satisfactory manner during their operational life, there is little incentive to improve or refine the design procedure. On the other hand, failures of heat exchangers clearly indicate deficiencies in the design procedures or in the data available to the designer. When such failures are attributable to flow-induced vibrations, the identification of the mechanisms involved is a prime importance. Ideally, basic research work provides the background understanding and the techniques necessary to be able to identify the important mechanisms. In practice, the investigation of a flow-induced vibration problem may identify the presence of mechanisms but may not be able to quantify their effects adequately. In these circumstances the need for additional work is established and the objectives of the research programme emerge. The purpose of this paper is to outline the background to the current research programme at C.E.R.L. on heat exchanger vibration.
General principles of vibrational spectroscopies
Weckhuysen, B.M.; Schoonheydt, R.A.
2000-01-01
Atoms in molecules and solids do not remain in fixed relative positions, but vibrate about some mean position. This vibrational motion is quantized and at room temperature, most of the molecules in a given sample are in their lowest vibrational state. Absorption of electromagnetic radiation with
High-Temperature Vibration Damper
Clarke, Alan; Litwin, Joel; Krauss, Harold
1987-01-01
Device for damping vibrations functions at temperatures up to 400 degrees F. Dampens vibrational torque loads as high as 1,000 lb-in. but compact enough to be part of helicopter rotor hub. Rotary damper absorbs energy from vibrating rod, dissipating it in turbulent motion of viscous hydraulic fluid forced by moving vanes through small orifices.
Shock and vibration technology with applications to electrical systems
Eshleman, R. L.
1972-01-01
A survey is presented of shock and vibration technology for electrical systems developed by the aerospace programs. The shock environment is surveyed along with new techniques for modeling, computer simulation, damping, and response analysis. Design techniques based on the use of analog computers, shock spectra, optimization, and nonlinear isolation are discussed. Shock mounting of rotors for performance and survival, and vibration isolation techniques are reviewed.
Vibration Antiresonance Design for a Spacecraft Multifunctional Structure
Li, Dong-Xu; Liu, Wang; Hao, Dong
2017-01-01
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 b...
Directory of Open Access Journals (Sweden)
Jianxu Zhou
2018-03-01
Full Text Available Hydraulic vibration exists in various water conveyance projects and has resulted in different operating problems, but its obvious effects on system’s pressure head and stable operation have not been definitively addressed in the issued codes for engineering design, especially considering the uncertainties of hydraulic vibration. After detailed analysis of the randomness in hydraulic vibration and the commonly used stochastic approaches, in the basic equations for hydraulic vibration analysis, the random parameters and the formed stochastic equations were discussed for further probabilistic characteristic analysis of the random variables. Furthermore, preliminary investigation of the stochastic analysis of hydraulic vibration in pressurized pipelines and possible self-excited vibration in pumped-storage systems was presented for further consideration. The detailed discussion indicates that it is necessary to conduct further and systematic stochastic analysis of hydraulic vibration. Further, with the obtained frequencies and amplitudes in the form of a probability statement, the stochastic characteristics of various hydraulic vibrations can be investigated in detail and these solutions will be more reasonable for practical applications. Eventually, the stochastic analysis of hydraulic vibration will provide a basic premise to introduce its effect into the engineering design of water diversion and hydropower systems.
The effects of vibration-reducing gloves on finger vibration
Welcome, Daniel E.; Dong, Ren G.; Xu, Xueyan S.; Warren, Christopher; McDowell, Thomas W.
2015-01-01
Vibration-reducing (VR) gloves have been used to reduce the hand-transmitted vibration exposures from machines and powered hand tools but their effectiveness remains unclear, especially for finger protection. The objectives of this study are to determine whether VR gloves can attenuate the vibration transmitted to the fingers and to enhance the understanding of the mechanisms of how these gloves work. Seven adult male subjects participated in the experiment. The fixed factors evaluated include hand force (four levels), glove condition (gel-filled, air bladder, no gloves), and location of the finger vibration measurement. A 3-D laser vibrometer was used to measure the vibrations on the fingers with and without wearing a glove on a 3-D hand-arm vibration test system. This study finds that the effect of VR gloves on the finger vibration depends on not only the gloves but also their influence on the distribution of the finger contact stiffness and the grip effort. As a result, the gloves increase the vibration in the fingertip area but marginally reduce the vibration in the proximal area at some frequencies below 100 Hz. On average, the gloves reduce the vibration of the entire fingers by less than 3% at frequencies below 80 Hz but increase at frequencies from 80 to 400 Hz. At higher frequencies, the gel-filled glove is more effective at reducing the finger vibration than the air bladder-filled glove. The implications of these findings are discussed. Relevance to industry Prolonged, intensive exposure to hand-transmitted vibration can cause hand-arm vibration syndrome. Vibration-reducing gloves have been used as an alternative approach to reduce the vibration exposure. However, their effectiveness for reducing finger-transmitted vibrations remains unclear. This study enhanced the understanding of the glove effects on finger vibration and provided useful information on the effectiveness of typical VR gloves at reducing the vibration transmitted to the fingers. The new
Universality in the dynamical properties of seismic vibrations
Chatterjee, Soumya; Barat, P.; Mukherjee, Indranil
2018-02-01
We have studied the statistical properties of the observed magnitudes of seismic vibration data in discrete time in an attempt to understand the underlying complex dynamical processes. The observed magnitude data are taken from six different geographical locations. All possible magnitudes are considered in the analysis including catastrophic vibrations, foreshocks, aftershocks and commonplace daily vibrations. The probability distribution functions of these data sets obey scaling law and display a certain universality characteristic. To investigate the universality features in the observed data generated by a complex process, we applied Random Matrix Theory (RMT) in the framework of Gaussian Orthogonal Ensemble (GOE). For all these six places the observed data show a close fit with the predictions of RMT. This reinforces the idea of universality in the dynamical processes generating seismic vibrations.
Study on vibration behaviors of engineered barrier system
International Nuclear Information System (INIS)
Mikoshiba, Tadashi; Ogawa, Nobuyuki; Minowa, Chikahiro
1998-01-01
High-level radioactive wastes have been buried underground by packing into a strong sealed container made from carbon steel (over-pack) with buffer material (bentonite). The engineered barrier system constructed with an overpack and buffer materials must be resistant to earthquakes as well as invasion of groundwater for a long period. Therefore, seismic evaluation of barrier system for earthquakes is indispensable especially in Japan to keep its structural safety. Here, the effects of earthquake vibration on the engineered barrier systems were investigated experimentally. Random-wave vibration and practical seismic wave one were loaded for the systems and fundamental data were obtained. For the former vibration the response characteristics of both engineered barrier models constructed with overpack and bentonite were non-linear. For the latter one, the stress in bentonite was increased in proportion to the vibration level. (M.N.)
Fueled viking generator S/N 106 acceptance vibration test report
International Nuclear Information System (INIS)
Anderson, C.; Brewer, C.O.; Abrahamson, S.G.
1976-01-01
The Viking Generator S/N 106 was vibrated to the Teledyne Isotope Flight Acceptance Schedule (Random Only) with no deviation from normal generator functional output. Radiographic analysis and power tests before and after the vibration test indicated no change in the condition of the generator. The work was conducted in the Alpha Fuels Environmental Test Facility at Mound Laboratory
Energy Technology Data Exchange (ETDEWEB)
Dong, Hui; Lewis, Nicholas H. C.; Oliver, Thomas A. A.; Fleming, Graham R., E-mail: grfleming@lbl.gov [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, Californial 94720 (United States); Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720 (United States)
2015-05-07
Changes in the electronic structure of pigments in protein environments and of polar molecules in solution inevitably induce a re-adaption of molecular nuclear structure. Both changes of electronic and vibrational energies can be probed with visible or infrared lasers, such as two-dimensional electronic spectroscopy or vibrational spectroscopy. The extent to which the two changes are correlated remains elusive. The recent demonstration of two-dimensional electronic-vibrational (2DEV) spectroscopy potentially enables a direct measurement of this correlation experimentally. However, it has hitherto been unclear how to characterize the correlation from the spectra. In this paper, we present a theoretical formalism to demonstrate the slope of the nodal line between the excited state absorption and ground state bleach peaks in the spectra as a characterization of the correlation between electronic and vibrational transition energies. We also show the dynamics of the nodal line slope is correlated to the vibrational spectral dynamics. Additionally, we demonstrate the fundamental 2DEV spectral line-shape of a monomer with newly developed response functions.
International Nuclear Information System (INIS)
Chen, S.S.
1975-06-01
Several mathematical models have been proposed for calculating fuel rod responses in axial flows based on a single rod consideration. The spacing between fuel rods in liquid metal fast breeder reactors is small; hence fuel rods will interact with one another due to fluid coupling. The objective of this paper is to study the coupled vibration of fuel bundles. To account for the fluid coupling, a computer code, AMASS, is developed to calculate added mass coefficients for a group of circular cylinders based on the potential flow theory. The equations of motion for rod bundles are then derived including hydrodynamic forces, drag forces, fluid pressure, gravity effect, axial tension, and damping. Based on the equations, a method of analysis is presented to study the free and forced vibrations of rod bundles. Finally, the method is applied to a typical LMFBR fuel bundle consisting of seven rods
Research on vibration signal analysis and extraction method of gear local fault
Yang, X. F.; Wang, D.; Ma, J. F.; Shao, W.
2018-02-01
Gear is the main connection parts and power transmission parts in the mechanical equipment. If the fault occurs, it directly affects the running state of the whole machine and even endangers the personal safety. So it has important theoretical significance and practical value to study on the extraction of the gear fault signal and fault diagnosis of the gear. In this paper, the gear local fault as the research object, set up the vibration model of gear fault vibration mechanism, derive the vibration mechanism of the gear local fault and analyzes the similarities and differences of the vibration signal between the gear non fault and the gears local faults. In the MATLAB environment, the wavelet transform algorithm is used to denoise the fault signal. Hilbert transform is used to demodulate the fault vibration signal. The results show that the method can denoise the strong noise mechanical vibration signal and extract the local fault feature information from the fault vibration signal..
Katarina Anthony
2015-01-01
In preparation for the civil engineering work on the HL-LHC, vibration measurements were carried out at the LHC’s Point 1 last month. These measurements will help evaluate how civil engineering work could impact the beam, and will provide crucial details about the site’s geological make-up before construction begins. A seismic truck at Point 1 generated wave-like vibrations measured by EN/MME. From carrying out R&D to produce state-of-the-art magnets to developing innovative, robust materials capable of withstanding beam impact, the HL-LHC is a multi-faceted project involving many groups and teams across CERN’s departments. It was in this framework that the project management mandated CERN's Mechanical and Materials Engineering (EN/MME) group to measure the propagation of vibrations around Point 1. Their question: can civil engineering work for the HL-LHC – the bulk of which is scheduled for LS2 – begin while the LHC is running? Alth...
Vibrational stability of graphene
Directory of Open Access Journals (Sweden)
Yangfan Hu
2013-05-01
Full Text Available The mechanical stability of graphene as temperature rises is analyzed based on three different self-consistent phonon (SCP models. Compared with three-dimensional (3-D materials, the critical temperature Ti at which instability occurs for graphene is much closer to its melting temperature Tm obtained from Monte Carlo simulation (Ti ≃ 2Tm, K. V. Zakharchenko, A. Fasolino, J. H. Los, and M. I. Katsnelson, J. Phys. Condens. Matter 23, 202202. This suggests that thermal vibration plays a significant role in melting of graphene while melting for 3-D materials is often dominated by topologic defects. This peculiar property of graphene derives from its high structural anisotropy, which is characterized by the vibrational anisotropic coefficient (VAC, defined upon its Lindermann ratios in different directions. For any carbon based material with a graphene-like structure, the VAC value must be smaller than 5.4 to maintain its stability. It is also found that the high VAC value of graphene is responsible for its negative thermal expansion coefficient at low temperature range. We believe that the VAC can be regarded as a new criterion concerning the vibrational stability of any low-dimensional (low-D materials.
Vibration Antiresonance Design for a Spacecraft Multifunctional Structure
Directory of Open Access Journals (Sweden)
Dong-Xu Li
2017-01-01
Full Text Available Spacecraft must withstand rigorous mechanical environment experiences such as acceleration, noise, vibration, and shock during the process of launching, satellite-vehicle separation, and so on. In this paper, a new spacecraft multifunctional structure concept designed by us is introduced. The multifunctional structure has the functions of not only load bearing, but also vibration reduction, energy source, thermal control, and so on, and we adopt a series of viscoelastic parts as connections between substructures. Especially in this paper, a vibration antiresonance design method is proposed to realize the vibration reduction. The complex zero-point equations of the vibration system are firstly established, and then the vibration antiresonance design for the system is achieved. For solving the difficulties due to viscoelastic characteristics of the connecting parts, we present the determining formulas to obtain the structural parameters, so that the complex zero-point equations can be satisfied. Numerical simulation and ground experiment demonstrate the correctness and effectiveness of the proposed method. This method can solve the structural vibration control problem under the function constraints of load bearing and energy supplying and will expand the performance of spacecraft functional modules.
Signal Processing Methods for Removing the Effects of Whole Body Vibration upon Speech
Bitner, Rachel M.; Begault, Durand R.
2014-01-01
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.
Directory of Open Access Journals (Sweden)
V.V. Rao
2015-06-01
Full Text Available This paper describes the comparison between Vibration Analysis (VA and Acoustic Emission (AE method to predict the defect severity in rolling element bearings with respect to the gradual increase of defect size. In bearing fault diagnosis vibration based methods are very popular, but the signals acquired by its transducers from the bearings are distorted by other faults and mechanical noise from the equipment. Vibration based methods are effective when the defect in the bearings has already become severe. AE is a non destructive testing (NDT technique used in structural health monitoring and its application for bearing defect diagnosis is gaining momentum as an alternate diagnostic tool because of its inherent high signal-to-noise-ratio (SNR. A bearing test rig was designed and set up to study the various defects in rolling element bearings in real environment. In earlier cases, though the researchers studied on different types of seeded defects with random sizes, they could not ascertain the correlation between their defect sizes and the vibration amplitude. The experimental investigation reported in this paper is centered on seeded defect of same type with gradual increase of its size on outer race of radially loaded cylindrical roller bearings and running the defective bearing at different speeds and loads. Data acquired through AE & vibration probes simultaneously for better diagnosis. Comparisons between AE and VA over a range of speed and load conditions at gradual increase of defect size are presented and from them it is concluded that AE method is superior to identify the severity of defect.
Energy Technology Data Exchange (ETDEWEB)
Wang, Hesheng [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China); Chen, Weidong, E-mail: wdchen@sjtu.edu.cn [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China); Xu, Lifei; He, Tao [Key Laboratory of System Control and Information Processing, Ministry of Education of China (China); Department of Automation, Shanghai Jiao Tong University, Shanghai 200240 (China)
2015-10-15
Highlights: • Vision-based online vibration estimation method for a flexible arm is proposed. • The vibration signal is obtained by image processing in unknown environments. • Vibration parameters are estimated by short-time Fourier transformation. - Abstract: The vibration should be suppressed if it happens during the motion of a flexible robot or under the influence of external disturbance caused by its structural features and material properties, because the vibration may affect the positioning accuracy and image quality. In Tokamak environment, we need to get the real-time vibration information on vibration suppression of robotic arm, however, some sensors are not allowed in the extreme Tokamak environment. This paper proposed a vision-based method for online vibration estimation of a flexible manipulator, which is achieved by utilizing the environment image information from the end-effector camera to estimate its vibration. Short-time Fourier Transformation with adaptive window length method is used to estimate vibration parameters of non-stationary vibration signals. Experiments with one-link flexible manipulator equipped with camera are carried out to validate the feasibility of this method in this paper.
International Nuclear Information System (INIS)
Wang, Hesheng; Chen, Weidong; Xu, Lifei; He, Tao
2015-01-01
Highlights: • Vision-based online vibration estimation method for a flexible arm is proposed. • The vibration signal is obtained by image processing in unknown environments. • Vibration parameters are estimated by short-time Fourier transformation. - Abstract: The vibration should be suppressed if it happens during the motion of a flexible robot or under the influence of external disturbance caused by its structural features and material properties, because the vibration may affect the positioning accuracy and image quality. In Tokamak environment, we need to get the real-time vibration information on vibration suppression of robotic arm, however, some sensors are not allowed in the extreme Tokamak environment. This paper proposed a vision-based method for online vibration estimation of a flexible manipulator, which is achieved by utilizing the environment image information from the end-effector camera to estimate its vibration. Short-time Fourier Transformation with adaptive window length method is used to estimate vibration parameters of non-stationary vibration signals. Experiments with one-link flexible manipulator equipped with camera are carried out to validate the feasibility of this method in this paper.
Blasting vibrations control: The shortcomings of traditional methods
Energy Technology Data Exchange (ETDEWEB)
Vuillaume, P.M.; Kiszlo, M. [Institut National de l`Environnement Industriel et des Risques, Verneuil en Halatte (France); Bernard, T. [Compagnie Nouvelle de Scientifiques, Nice (France)
1996-12-31
In the context of its studies for the French ministry of the environment and for the French national coal board, INERIS (the French institute for the industrial environment and hazards, formerly CERCHAR) has made a complete critical survey of the methods generally used to reduce the levels of blasting vibrations. It is generally acknowledged that the main parameter to control vibrations is the so-called instantaneous charge, or charge per delay. This should be reduced as much as possible in order to diminish vibration levels. On account of this, the use of a new generation of blasting devices, such as non-electric detonators or electronic sequential timers has been developed since the seventies. INERIS has collected data from about 900 blasts in 2 quarries and 3 open pit mines. These data include input parameters such as borehole diameter, burden, spacing, charge per hole, charge per delay, total fired charge, etc ... They also include output measurements, such as vibration peak particle velocities, and main frequencies. These data have been analyzed with the help of multi variable statistical tools. Blasting tests were undertaken to evaluate new methods of vibrations control, such as the superposition of vibration signals. These methods appear to be accurate in many critical cases, but certainly would be highly improved with a better accuracy of firing delays. The development of electronic detonators seems to be the way of the future for a better blasting control.
Reducing vibration transfer from power plants by active methods
Kiryukhin, A. V.; Milman, O. O.; Ptakhin, A. V.
2017-12-01
The possibility of applying the methods of active damping of vibration and pressure pulsations for reducing their transfer from power plants into the environment, the seating, and the industrial premises are considered. The results of experimental works implemented by the authors on the active broadband damping of vibration and dynamic forces after shock-absorption up to 15 dB in the frequency band up to 150 Hz, of water pressure pulsations in the pipeline up to 20 dB in the frequency band up to 600 Hz, and of spatial low-frequency air noise indoors of a diesel generator at discrete frequency up to 20 dB are presented. It is shown that a reduction of vibration transfer through a vibration-isolating junction (expansion joints) of pipelines with liquid is the most complicated and has hardly been developed so far. This problem is essential for vibration isolation of power equipment from the seating and the environment through pipelines with water and steam in the power and transport engineering, shipbuilding, and in oil and gas pipelines in pumping stations. For improving efficiency, reducing the energy consumption, and decreasing the overall dimensions of equipment, it is advisable to combine the work of an active system with passive damping means, the use of which is not always sufficient. The executive component of the systems of active damping should be placed behind the vibration isolators (expansion joints). It is shown that the existence of working medium and connection of vibration with pressure pulsations in existing designs of pipeline expansion joints lead to growth of vibration stiffness of the expansion joint with the environment by two and more orders as compared with the static stiffness and makes difficulties for using the active methods. For active damping of vibration transfer through expansion joints of pipelines with a liquid, it is necessary to develop expansion joint structures with minimal connection of vibrations and pulsations and minimal
Survey of vibration amplitudes throughout the linac
International Nuclear Information System (INIS)
Werner, K.L.
1984-01-01
The magnitude of vibrations of the Linac structure due to on site disturbances, such as cooling towers, pumps, generators, Highway 280 overpass traffic, is of interest. CN-263, for example, discusses tolerances of random (i.e., uncorrelated) quad jitter and suggests that amplitudes should not exceed 0.7 microns rms. This note describes the results of a series of measurements carried out in the summer of 1983. In general, the tolerance is not exceeded, but there appears not to be a good safety factor at low frequencies
A Novel Ropes-DrivenWideband Piezoelectric Vibration Energy Harvester
Directory of Open Access Journals (Sweden)
Jinhui Zhang
2016-12-01
Full Text Available This paper presents a novel piezoelectric vibration energy harvester (PVEH in which a high-frequency generating beam (HFGB is driven by an array of low-frequency driving beams (LFDBs using ropes. Two mechanisms based on frequency upconversion and multimodal harvesting work together to broaden the frequency bandwidth of the proposed vibration energy harvester (VEH. The experimental results show that the output power of generating beam (GB remains unchanged with the increasing number of driving beams (DBs, compared with the traditional arrays of beams vibration energy harvester (AB-VEH, and the output power and bandwidth behavior can be adjusted by parameters such as acceleration, rope margin, and stiffness of LFDBs, which shows the potential to achieve unlimited wideband vibration energy-harvesting for a variable environment.
Energy evaluation of protection effectiveness of anti-vibration gloves.
Hermann, Tomasz; Dobry, Marian Witalis
2017-09-01
This article describes an energy method of assessing protection effectiveness of anti-vibration gloves on the human dynamic structure. The study uses dynamic models of the human and the glove specified in Standard No. ISO 10068:2012. The physical models of human-tool systems were developed by combining human physical models with a power tool model. The combined human-tool models were then transformed into mathematical models from which energy models were finally derived. Comparative energy analysis was conducted in the domain of rms powers. The energy models of the human-tool systems were solved using numerical simulation implemented in the MATLAB/Simulink environment. The simulation procedure demonstrated the effectiveness of the anti-vibration glove as a method of protecting human operators of hand-held power tools against vibration. The desirable effect is achieved by lowering the flow of energy in the human-tool system when the anti-vibration glove is employed.
VIBRATION ISOLATION SYSTEM PROBABILITY ANALYSIS
Directory of Open Access Journals (Sweden)
Smirnov Vladimir Alexandrovich
2012-10-01
Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.
Prototype observation and influencing factors of environmental vibration induced by flood discharge
Directory of Open Access Journals (Sweden)
Xin Wang
2017-01-01
Full Text Available Due to a wide range of field vibration problems caused by flood discharge at the Xiangjiaba Hydropower Station, vibration characteristics and influencing factors were investigated based on prototype observation. The results indicate that field vibrations caused by flood discharge have distinctive characteristics of constancy, low frequency, small amplitude, and randomness with impact, which significantly differ from the common high-frequency vibration characteristics. Field vibrations have a main frequency of about 0.5–3.0 Hz and the characteristics of long propagation distance and large-scale impact. The vibration of a stilling basin slab runs mainly in the vertical direction. The vibration response of the guide wall perpendicular to the flow is significantly stronger than it is in other directions and decreases linearly downstream along the guide wall. The vibration response of the underground turbine floor is mainly caused by the load of unit operation. Urban environmental vibration has particular distribution characteristics and change patterns, and is greatly affected by discharge, scheduling modes, and geological conditions. Along with the increase of the height of residential buildings, vibration responses show a significant amplification effect. The horizontal and vertical vibrations of the 7th floor are, respectively, about 6 times and 1.5 times stronger than the corresponding vibrations of the 1st floor. The vibration of a large-scale chemical plant presents the combined action of flood discharge and working machines. Meanwhile, it is very difficult to reduce the low-frequency environmental vibrations. Optimization of the discharge scheduling mode is one of the effective measures of reducing the flow impact loads at present. Choosing reasonable dam sites is crucial.
Vibration damping method and apparatus
Redmond, James M.; Barney, Patrick S.; Parker, Gordon G.; Smith, David A.
1999-01-01
The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof.
Atomic beams probe surface vibrations
International Nuclear Information System (INIS)
Robinson, A.L.
1982-01-01
In the last two years, surface scientist have begun trying to obtain the vibrational frequencies of surface atoms in both insulating and metallic crystals from beams of helium atoms. It is the inelastic scattering that researchers use to probe surface vibrations. Inelastic atomic beam scattering has only been used to obtain vibrational frequency spectra from clean surfaces. Several experiments using helium beams are cited. (SC)
Piezoelectric Bimorph Cantilever for Vibration-Producing-Hydrogen
Directory of Open Access Journals (Sweden)
Guangming Cheng
2012-12-01
Full Text Available A device composed of a piezoelectric bimorph cantilever and a water electrolysis device was fabricated to realize piezoelectrochemical hydrogen production. The obvious output of the hydrogen and oxygen through application of a mechanical vibration of ~0.07 N and ~46.2 Hz was observed. This method provides a cost-effective, recyclable, environment-friendly and simple way to directly split water for hydrogen fuels by scavenging mechanical waste energy forms such as noise or traffic vibration in the environment.
Institute of Scientific and Technical Information of China (English)
田鹏伟
2015-01-01
The paper illustrates the reasons for the random observation errors in water environment,analyzes definitions,features and regulation of the random observation errors,and explores precautions in the random observation errors in water environment evaluation,so as to provide some reference for the treatment of water pollution.%阐述了水环境评价中产生随机观测误差的原因，分析了随机观测误差的定义、特点及其规律性，并对随机观测误差需注意的事项进行了研究探讨，为水污染的治理提供了一定的参考依据。
Digital analysis of vibrations
International Nuclear Information System (INIS)
Bohnstedt, H.J.; Walter, G.
1982-01-01
Vibrational measurements, e.g. on turbomachinery, can be evaluated rapidly and economically with the aid of a combination of the following instruments: a desk-top computer, a two-channel vector filter and a FFT spectral analyzer. This equipment combination is available within the Allianz Centre for Technology and has also been used for mobile, on-site investigations during the last year. It enables calculation and display of time functions, kinetic shaft orbits, displacement diagrams. Bode plots, polar-coordinate plots, cascade diagrams and histograms. (orig.) [de
Turbine blade vibration dampening
Cornelius, C.C.; Pytanowski, G.P.; Vendituoli, J.S.
1997-07-08
The present turbine wheel assembly increases component life and turbine engine longevity. The combination of the strap and the opening combined with the preestablished area of the outer surface of the opening and the preestablished area of the outer circumferential surface of the strap and the friction between the strap and the opening increases the life and longevity of the turbine wheel assembly. Furthermore, the mass ``M`` or combined mass ``CM`` of the strap or straps and the centrifugal force assist in controlling vibrations and damping characteristics. 5 figs.
Lattice Vibrations in Chlorobenzenes:
DEFF Research Database (Denmark)
Reynolds, P. A.; Kjems, Jørgen; White, J. W.
1974-01-01
Lattice vibrational dispersion curves for the ``intermolecular'' modes in the triclinic, one molecule per unit cell β phase of p‐C6D4Cl2 and p‐C6H4Cl2 have been obtained by inelastic neutron scattering. The deuterated sample was investigated at 295 and at 90°K and a linear extrapolation to 0°K...... was applied in order to correct for anharmonic effects. Calculations based on the atom‐atom model for van der Waals' interaction and on general potential parameters for the aromatic compounds agree reasonably well with the experimental observations. There is no substantial improvement in fit obtained either...
Vibration control, machine diagnostics
International Nuclear Information System (INIS)
1990-01-01
Changing vibrations announce damage in the form of wear or cracks on components of, e.g., engine rotors, pumps, power plant turbo sets, rounding-up tools, or marine diesel engines. Therefore, machine diagnostics use frequency analyses, system tests, trend analyses as well as expert systems to localize or estimate the causes of these damages and malfunctions. Data acquisistion, including not only sensors, but also reliable and redundant data processing systems and analyzing systems, play an important role. The lectures pertaining to the data base are covered in detail. (DG) [de
Off-axis Modal Active Vibration Control Of Rotational Vibrations
Babakhani, B.; de Vries, Theodorus J.A.; van Amerongen, J.
Collocated active vibration control is an effective and robustly stable way of adding damping to the performance limiting vibrations of a plant. Besides the physical parameters of the Active Damping Unit (ADU) containing the collocated actuator and sensor, its location with respect to the
Zhou, Danfeng; Yu, Peichang; Wang, Lianchun; Li, Jie
2017-11-01
The levitation gap of the urban maglev train is around 8 mm, which puts a rather high requirement on the smoothness of the track. In practice, it is found that the track irregularity may cause stability problems when the maglev train is traveling. In this paper, the dynamic response of the levitation module, which is the basic levitation structure of the urban maglev train, is investigated in the presence of track irregularities. Analyses show that due to the structural configuration of the levitation module, the vibration of the levitation gap may be amplified and "resonances" may be observed under some specified track wavelengths and train speeds; besides, it is found that the gap vibration of the rear levitation unit in a levitation module is more significant than that of the front levitation unit, which agrees well with practice. To suppress the vibration of the rear levitation gap, an adaptive vibration control method is proposed, which utilizes the information of the front levitation unit as a reference. A pair of mirror FIR (finite impulse response) filters are designed and tuned by an adaptive mechanism, and they produce a compensation signal for the rear levitation controller to cancel the disturbance brought by the track irregularity. Simulations under some typical track conditions, including the sinusoidal track profile, random track irregularity, as well as track steps, indicate that the adaptive vibration control scheme can significantly reduce the amplitude of the rear gap vibration, which provides a method to improve the stability and ride comfort of the maglev train.
The effect of mechanical vibration on orthodontically induced root resorption.
Yadav, Sumit; Dobie, Thomas; Assefnia, Amir; Kalajzic, Zana; Nanda, Ravindra
2016-09-01
To investigate the effect of low-frequency mechanical vibration (LFMV) on orthodontically induced root resorption. Forty male CD1, 12-week-old mice were used for the study. The mice were randomly divided into five groups: group 1 (baseline)-no spring and no mechanical vibration, group 2-orthodontic spring but no vibration, group 3-orthodontic spring and 5 Hz of vibration applied to the maxillary first molar, group 4-orthodontic spring and 10 Hz of vibration applied to maxillary first molar, and group 5-orthodontic spring and 20 Hz of vibration applied to maxillary first molar. In the different experimental groups, the first molar was moved mesially for 2 weeks using a nickel-titanium coil spring delivering 10 g of force. LFMVs were applied at 5 Hz, 10 Hz, and 20 Hz. Microfocus X-ray computed tomography imaging was used to analyze root resorption. Additionally, to understand the mechanism, we applied LFMV to MC3T3 cells, and gene expression analyses were done for receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG). Orthodontic tooth movement leads to decreased root volume (increased root resorption craters). Our in vivo experiments showed a trend toward increase in root volume with different frequencies of mechanical vibration. In vitro gene expression analyses showed that with 20 Hz of mechanical vibration, there was a significant decrease in RANKL and a significant increase in OPG expression. There was a trend toward decreased root resorption with different LFMVs (5 Hz, 10 Hz, and 20 Hz); however, it was not more statistically significant than the orthodontic-spring-only group.
Santana, Mário L; Bignardi, Annaiza Braga; Pereira, Rodrigo Junqueira; Menéndez-Buxadera, Alberto; El Faro, Lenira
2016-02-01
The present study had the following objectives: to compare random regression models (RRM) considering the time-dependent (days in milk, DIM) and/or temperature × humidity-dependent (THI) covariate for genetic evaluation; to identify the effect of genotype by environment interaction (G×E) due to heat stress on milk yield; and to quantify the loss of milk yield due to heat stress across lactation of cows under tropical conditions. A total of 937,771 test-day records from 3603 first lactations of Brazilian Holstein cows obtained between 2007 and 2013 were analyzed. An important reduction in milk yield due to heat stress was observed for THI values above 66 (-0.23 kg/day/THI). Three phases of milk yield loss were identified during lactation, the most damaging one at the end of lactation (-0.27 kg/day/THI). Using the most complex RRM, the additive genetic variance could be altered simultaneously as a function of both DIM and THI values. This model could be recommended for the genetic evaluation taking into account the effect of G×E. The response to selection in the comfort zone (THI ≤ 66) is expected to be higher than that obtained in the heat stress zone (THI > 66) of the animals. The genetic correlations between milk yield in the comfort and heat stress zones were less than unity at opposite extremes of the environmental gradient. Thus, the best animals for milk yield in the comfort zone are not necessarily the best in the zone of heat stress and, therefore, G×E due to heat stress should not be neglected in the genetic evaluation.
Vibration of heat exchange components in liquid and two-phase cross-flow
International Nuclear Information System (INIS)
Pettigrew, M.J.
1978-05-01
Heat exchange components must be analysed at the design stage to avoid flow-induced vibration problems. This paper presents information required to formulate flow-induced vibration excitation mechanisms in liquid and two-phase cross-flow. Three basic excitation mechanisms are considered, namely: 1) fluidelastic instability, 2) periodic wake shedding, and 3) response to random flow turbulence. The vibration excitation information is deduced from vibration response data for various types of tube bundles. Sources of information are: 1) fundamental studies on tube bundles, 2) model testing, 3) field measurements, and 4) operating experiences. Fluidelastic instability is formulated in terms of dimensionless flow velocity and dimensionless damping; periodic wake shedding in terms of Strouhal number and lift coefficient; and random turbulence excitation in terms of statistical parameters of random forces. Guidelines are recommended for design purposes. (author)
Vibrational spectra of ordered perovskites
Corsmit, A.F.; Hoefdraad, H.E.; Blasse, G.
1972-01-01
The vibrational spectra of the molecular M6+O6 (M = Mo, Te, W) group in ordered perovskites of the type Ba2M2+M6+O6 are reported. These groups have symmetry Oh, whereas their site symmetry is also Oh. An assignment of the internal vibrations is presented.
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....
Occupant traffic estimation through structural vibration sensing
Pan, Shijia; Mirshekari, Mostafa; Zhang, Pei; Noh, Hae Young
2016-04-01
The number of people passing through different indoor areas is useful in various smart structure applications, including occupancy-based building energy/space management, marketing research, security, etc. Existing approaches to estimate occupant traffic include vision-, sound-, and radio-based (mobile) sensing methods, which have placement limitations (e.g., requirement of line-of-sight, quiet environment, carrying a device all the time). Such limitations make these direct sensing approaches difficult to deploy and maintain. An indirect approach using geophones to measure floor vibration induced by footsteps can be utilized. However, the main challenge lies in distinguishing multiple simultaneous walkers by developing features that can effectively represent the number of mixed signals and characterize the selected features under different traffic conditions. This paper presents a method to monitor multiple persons. Once the vibration signals are obtained, features are extracted to describe the overlapping vibration signals induced by multiple footsteps, which are used for occupancy traffic estimation. In particular, we focus on analysis of the efficiency and limitations of the four selected key features when used for estimating various traffic conditions. We characterize these features with signals collected from controlled impulse load tests as well as from multiple people walking through a real-world sensing area. In our experiments, the system achieves the mean estimation error of +/-0.2 people for different occupant traffic conditions (from one to four) using k-nearest neighbor classifier.
Low Cost Digital Vibration Meter.
Payne, W Vance; Geist, Jon
2007-01-01
This report describes the development of a low cost, digital Micro Electro Mechanical System (MEMS) vibration meter that reports an approximation to the RMS acceleration of the vibration to which the vibration meter is subjected. The major mechanical element of this vibration meter is a cantilever beam, which is on the order of 500 µm in length, with a piezoresistor deposited at its base. Vibration of the device in the plane perpendicular to the cantilever beam causes it to bend, which produces a measurable change in the resistance of a piezoresistor. These changes in resistance along with a unique signal-processing scheme are used to determine an approximation to the RMS acceleration sensed by the device.
Integrated cable vibration control system using wireless sensors
Jeong, Seunghoo; Cho, Soojin; Sim, Sung-Han
2017-04-01
As the number of long-span bridges is increasing worldwide, maintaining their structural integrity and safety become an important issue. Because the stay cable is a critical member in most long-span bridges and vulnerable to wind-induced vibrations, vibration mitigation has been of interest both in academia and practice. While active and semi-active control schemes are known to be quite effective in vibration reduction compared to the passive control, requirements for equipment including data acquisition, control devices, and power supply prevent a widespread adoption in real-world applications. This study develops an integrated system for vibration control of stay-cables using wireless sensors implementing a semi-active control. Arduino, a low-cost single board system, is employed with a MEMS digital accelerometer and a Zigbee wireless communication module to build the wireless sensor. The magneto-rheological (MR) damper is selected as a damping device, controlled by an optimal control algorithm implemented on the Arduino sensing system. The developed integrated system is tested in a laboratory environment using a cable to demonstrate the effectiveness of the proposed system on vibration reduction. The proposed system is shown to reduce the vibration of stay-cables with low operating power effectively.
A vibration correction method for free-fall absolute gravimeters
Qian, J.; Wang, G.; Wu, K.; Wang, L. J.
2018-02-01
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.
Hand-arm vibration in tropical rain forestry workers.
Futatsuka, M; Inaoka, T; Ohtsuka, R; Sakurai, T; Moji, K; Igarashi, T
1995-01-01
Working conditions and health hazards including vibration syndrome related to forestry work using chain-saws were studied in Papua New Guinea and Indonesia. The subjects comprised 291 workers including 97 chain-saw operators. The health examination consisted of peripheral circulatory and sensory tests in the upper extremities. The vibration spectrum measured at the handle of the chain-saw indicated that these acceleration levels would lead to a moderately high risk of hand-arm vibration syndrome (HAVS). The peripheral circulatory function tests revealed dysfunction after more than five years vibration exposure. However, in general, the results of the function tests and subjective complaints showed fewer health problems compared to those of Japanese forestry workers. The reason of such differences of vibration effects seem to be the following: (1) warmer climate (more than 25 degrees C throughout the year), (2) young workers and short work experience. (3) short time vibration exposures on working days in the natural forests, (4) seasonal changes in logging work (5) healthy workers effects. Thus, we found no clear evidence that the workers of our study suffered from HAVS. A principal component analysis was applied. The factor score of the components of the reactive dynamics of peripheral circulation differed significantly after more than five years' exposure. On the other hand, we cannot deny the possibility that subclinical dysfunction of peripheral circulation may be caused by chain-saw operation in the tropics in future. Further investigations on the HAVS among forestry workers in the tropic environment are needed.
Vibration aging of diesel-engine mounted electrical equipment
International Nuclear Information System (INIS)
Lee, B.J.; Morton, W.C.
1994-01-01
The Emergency Diesel Generator (EDG) in a Nuclear Power Plant is considered to be a component which is essential to safe plant operation. Failures of auxiliary equipment directly mounted on the EDG creates costly repairs, and compromises the engine's availability and reliability. Although IEEE-323 requires addressing of safety-related components due to mechanically induced vibration, very few guidelines exist in the nuclear industry to show how this may be accounted for. Most engine vendors rely on the empirical experience data as the basis of their evaluation for vibration. Upgrade of engine controls, addition of monitoring devices and other engine modifications require design and installation of new equipment to be mounted directly on the engine. This necessitates the evaluation for engine-induced vibration which is considered to be one of the most severe design parameters. This paper discusses the engine vibration characteristics, and the acquisition of extensive field vibration data on the diesel engine under operating conditions. The data is then used to develop life cycle vibration qualification test profiles that can be applied with confidence in a laboratory environment to qualify engine-mounted equipment. The intent is to validate a product's ability to survive under worst case, extended service on-engine conditions. This paper describes the procedures and approaches used to achieve those goals, and provides developed profile examples and test results
Wang, Xu; Bi, Fengrong; Du, Haiping
2018-05-01
This paper aims to develop an 5-degree-of-freedom driver and seating system model for optimal vibration control. A new method for identification of the driver seating system parameters from experimental vibration measurement has been developed. The parameter sensitivity analysis has been conducted considering the random excitation frequency and system parameter uncertainty. The most and least sensitive system parameters for the transmissibility ratio have been identified. The optimised PID controllers have been developed to reduce the driver's body vibration.
Jans, Elijah R.; Eckert, Zakari; Frederickson, Kraig; Rich, Bill; Adamovich, Igor V.
2017-06-01
Measurements of the vibrational distribution function of carbon monoxide produced via a reaction between carbon vapor and molecular oxygen has shown a total population inversion on vibrational levels 4-7. Carbon vapor, produced using an arc discharge to sublimate graphite, is mixed with an argon oxygen flow. The excited carbon monoxide is vibrationally populated up to level v=14, at low temperatures, T=400-450 K, in a collision-dominated environment, 15-20 Torr, with total population inversions between v=4-7. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of the reaction enthalpy. Kinetic modeling of the flow reactor, including state specific vibrational processes, was performed to infer the vibrational distribution of the products of the reaction. The results show viability of developing of a new chemical CO laser from the reaction of carbon vapor and oxygen.
Energy Technology Data Exchange (ETDEWEB)
Schubert, Alexander, E-mail: schubert@irsamc.ups-tlse.fr; Meier, Christoph [Laboratoire Collisions Agrégats et Réactivité, IRSAMC, UMR CNRS 5589, Université Paul Sabatier, 31062 Toulouse (France); Falvo, Cyril [Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France)
2016-08-07
We present mixed quantum-classical simulations on relaxation and dephasing of vibrationally excited carbon monoxide within a protein environment. The methodology is based on a vibrational surface hopping approach treating the vibrational states of CO quantum mechanically, while all remaining degrees of freedom are described by means of classical molecular dynamics. The CO vibrational states form the “surfaces” for the classical trajectories of protein and solvent atoms. In return, environmentally induced non-adiabatic couplings between these states cause transitions describing the vibrational relaxation from first principles. The molecular dynamics simulation yields a detailed atomistic picture of the energy relaxation pathways, taking the molecular structure and dynamics of the protein and its solvent fully into account. Using the ultrafast photolysis of CO in the hemoprotein FixL as an example, we study the relaxation of vibrationally excited CO and evaluate the role of each of the FixL residues forming the heme pocket.
International Nuclear Information System (INIS)
Lutz, H.D.; Willich, P.
1977-01-01
The FIR absorption spectra of pyrite type compounds RuS 2 , RuSsub(2-x)Sesub(x), RuSe 2 , RuTe 2 , OsS 2 , OsSe 2 , and PtP 2 as well as loellingite type phosphides FeP 2 , RuP 2 , and OsP 2 are reported. For RuS 2 , RuSe 2 , RuTe 2 , OsS 2 , and PtP 2 all of the five infrared allowed modes (k = 0) are observed. As a first result of a numerical normal coordinate treatment vibration forms of pyrite structure are communicated. The spectra show that lattice forces of corresponding sulfides, tellurides, and phosphides are about the same strength, but increase strongly by substitution of iron by ruthenium and especially of ruthenium by osmium. The lattice constants of the RuSsub(2-x)Sesub(x) solid solution obey Vegard's rule. (author)
Vibration condition measure instrument of motor using MEMS accelerometer
Chen, Jun
2018-04-01
In this work, a novel vibration condition measure instrument of motor using a digital micro accelerometer is proposed. In order to reduce the random noise found in the data, the sensor modeling is established and also the Kalman filter (KMF) is developed. According to these data from KMF, the maximum vibration displacement is calculated by the integration algorithm with the DC bias removed. The high performance micro controller unit (MCU) is used in the implementation of controller. By the IIC digital interface port, the data are transmitted from sensor to controller. The hardware circuits of the sensor and micro controller are designed and tested. With the computational formula of maximum displacement and FFT, the high precession results of displacement and frequency are gotten. Finally, the paper presents various experimental results to prove that this instrument is suitable for application in electrical motor vibration measurement.
Noise and Vibration Risk Prevention Virtual Web for Ubiquitous Training
Redel-Macías, María Dolores; Cubero-Atienza, Antonio J.; Martínez-Valle, José Miguel; Pedrós-Pérez, Gerardo; del Pilar Martínez-Jiménez, María
2015-01-01
This paper describes a new Web portal offering experimental labs for ubiquitous training of university engineering students in work-related risk prevention. The Web-accessible computer program simulates the noise and machine vibrations met in the work environment, in a series of virtual laboratories that mimic an actual laboratory and provide the…
Vibrational properties of complex solids
International Nuclear Information System (INIS)
Fagas, G.
1999-11-01
Following a brief outline of the statistical analysis of spectra with respect to random matrix theory predictions and of numerical methods for calculating the elastic scattering matrix, statistical studies of vibrational spectra in disordered and complex solids, as well as studies of phonon transport across imperfect structures, are presented. The analysis of spectral statistics of lattice modes in a disordered crystal, confirmed GOE Wigner-Dyson statistical correlations of the eigenmode frequencies of a block of a disordered solid. Spectral correlations in the optic phonon spectrum of a solid with a polyatomic unit cell are also analysed using the Wigner-Dyson statistical approach. Despite the fact that all force constants are real, it is demonstrated that the statistics are predominantly of the GUE type depending on the location within the Brillouin zone of a crystal and the unit cell symmetry. Analytic and numerical results for the crossover from GOE to GUE statistics are presented. A method originally developed to probe electron transport on a mesoscopic scale is used to study generic properties of elastic phonon transport at a disordered interface. The results show that phonon transmittance is a strong function of frequency and the disorder correlation length. At low frequencies the transmittance at a given frequency increases as the correlation length decreases. This is also reflected by different power-laws for phonon conductance across correlated and uncorrelated disordered interfaces which are in approximate agreement with perturbation theory of an elastic continuum. Finally we present an analysis of acoustic-phonon propagation across long, free-standing, insulating wires with rough surfaces. We find that owing to a crossover from ballistic propagation of the lowest-frequency phonon mode at ω 1 πc/W to a diffusive (or even localized) behavior upon the increase of phonon frequency, followed by reentrance into the quasiballistic regime, the heat
Vibrational Spectroscopy of Ionic Liquids.
Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C
2017-05-24
Vibrational spectroscopy has continued use as a powerful tool to characterize ionic liquids since the literature on room temperature molten salts experienced the rapid increase in number of publications in the 1990's. In the past years, infrared (IR) and Raman spectroscopies have provided insights on ionic interactions and the resulting liquid structure in ionic liquids. A large body of information is now available concerning vibrational spectra of ionic liquids made of many different combinations of anions and cations, but reviews on this literature are scarce. This review is an attempt at filling this gap. Some basic care needed while recording IR or Raman spectra of ionic liquids is explained. We have reviewed the conceptual basis of theoretical frameworks which have been used to interpret vibrational spectra of ionic liquids, helping the reader to distinguish the scope of application of different methods of calculation. Vibrational frequencies observed in IR and Raman spectra of ionic liquids based on different anions and cations are discussed and eventual disagreements between different sources are critically reviewed. The aim is that the reader can use this information while assigning vibrational spectra of an ionic liquid containing another particular combination of anions and cations. Different applications of IR and Raman spectroscopies are given for both pure ionic liquids and solutions. Further issues addressed in this review are the intermolecular vibrations that are more directly probed by the low-frequency range of IR and Raman spectra and the applications of vibrational spectroscopy in studying phase transitions of ionic liquids.
The Shock and Vibration Digest. Volume 7, Number 7, July 1975.
Contents: News briefs; Feature article: The application of skeleton curves and limit envelopes to analysis of nonlinear vibration; Abstracts from the current literature--analysis and design, computer programs, environments, phenomenology, experimentation, components, systems; Author index ; Literature review; Book reviews.
Molecular vibrations the theory of infrared and Raman vibrational spectra
Wilson, E Bright; Cross, Paul C
1980-01-01
Pedagogical classic and essential reference focuses on mathematics of detailed vibrational analyses of polyatomic molecules, advancing from application of wave mechanics to potential functions and methods of solving secular determinant.
Dissipation enhanced vibrational sensing in an olfactory molecular switch
International Nuclear Information System (INIS)
Chęcińska, Agata; Heaney, Libby; Pollock, Felix A.; Nazir, Ahsan
2015-01-01
Motivated by a proposed olfactory mechanism based on a vibrationally activated molecular switch, we study electron transport within a donor-acceptor pair that is coupled to a vibrational mode and embedded in a surrounding environment. We derive a polaron master equation with which we study the dynamics of both the electronic and vibrational degrees of freedom beyond previously employed semiclassical (Marcus-Jortner) rate analyses. We show (i) that in the absence of explicit dissipation of the vibrational mode, the semiclassical approach is generally unable to capture the dynamics predicted by our master equation due to both its assumption of one-way (exponential) electron transfer from donor to acceptor and its neglect of the spectral details of the environment; (ii) that by additionally allowing strong dissipation to act on the odorant vibrational mode, we can recover exponential electron transfer, though typically at a rate that differs from that given by the Marcus-Jortner expression; (iii) that the ability of the molecular switch to discriminate between the presence and absence of the odorant, and its sensitivity to the odorant vibrational frequency, is enhanced significantly in this strong dissipation regime, when compared to the case without mode dissipation; and (iv) that details of the environment absent from previous Marcus-Jortner analyses can also dramatically alter the sensitivity of the molecular switch, in particular, allowing its frequency resolution to be improved. Our results thus demonstrate the constructive role dissipation can play in facilitating sensitive and selective operation in molecular switch devices, as well as the inadequacy of semiclassical rate equations in analysing such behaviour over a wide range of parameters
Microgravity Active Vibration Isolation System on Parabolic Flights
Dong, Wenbo; Pletser, Vladimir; Yang, Yang
2016-07-01
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
Putting a damper on drilling's bad vibrations
Energy Technology Data Exchange (ETDEWEB)
Jardine, S [Sedco forex, Montrouge (France); Malone, D [Anadrill, Sugar Land, TX (United States); Sheppard, M [Schlumberger Cambridge Research, Cambridge (United Kingdom)
1994-01-01
Harmful drilling vibrations are costing the industry dearly. Three main vibration types (axial, torsional and transverse) are explained and its causes discussed. Technology exists to eliminate most vibrations, but requires more systematic deployment than is usual. Hardware that eliminates vibrations is reviewed, including downhole shock measurement, torque feedback shock guards and antiwhirl bits. 9 figs., 11 refs.
Low frequency vibrations disrupt left-right patterning in the Xenopus embryo.
Directory of Open Access Journals (Sweden)
Laura N Vandenberg
Full Text Available The development of consistent left-right (LR asymmetry across phyla is a fascinating question in biology. While many pharmacological and molecular approaches have been used to explore molecular mechanisms, it has proven difficult to exert precise temporal control over functional perturbations. Here, we took advantage of acoustical vibration to disrupt LR patterning in Xenopus embryos during tightly-circumscribed periods of development. Exposure to several low frequencies induced specific randomization of three internal organs (heterotaxia. Investigating one frequency (7 Hz, we found two discrete periods of sensitivity to vibration; during the first period, vibration affected the same LR pathway as nocodazole, while during the second period, vibration affected the integrity of the epithelial barrier; both are required for normal LR patterning. Our results indicate that low frequency vibrations disrupt two steps in the early LR pathway: the orientation of the LR axis with the other two axes, and the amplification/restriction of downstream LR signals to asymmetric organs.
Active Vibration Control of a Railway Vehicle Carbody Using Piezoelectric Elements
Molatefi, Habibollah; Ayoubi, Pejman; Mozafari, Hozhabr
2017-07-01
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.
Vibration measurements of automobile catalyst
Aatola, Seppo
1994-09-01
Vibration of catalyst cell, which is inside the casing of the catalyst, is difficult to measure with usual measuring instrumentation. When catalyst is in use, there is hot exhaust gas flow though the catalyst cell and temperature of the cell is approximately +900 degree(s)C. Therefore non-contact Laser- Doppler-Vibrometer was used to measure vibration velocity of the catalyst cell. The laser beam was directed towards the cell through pipe which was put through and welded to the casing of the catalyst. The outer end of the pipe was screw down with a tempered class to prevent exhaust gas flow from the pipe. The inner end of the pipe was open and few millimeters away from the measuring point. Catalyst was attached to the engine with two ways, rigidly close to the engine and flexible under the engine. The engine was running in test bench under controlled conditions. Vibration measurements were carried out during constant running speeds of the engine. Vibration signals were captured and analyzed with FFT-analyzer. Vibration of catalyst cell was strongest at running speed of 5000 rpm, from 10 to 20 g (1 g equals 9.81 ms-2), when catalyst was attached rigidly close to the engine. At running speed of 3000 rpm, vibration of catalyst cell was from 2 to 3 g in most cases, when catalyst was attached either rigidly or flexible to the engine. It is estimated that in real life, i.e. when catalyst is attached to car with same engine, vibration of catalyst cell at running speed of 5000 rpm is somewhere between 1 and 10 g. At running speed of 3000 rpm, which may be more often used when driving car (car speed approximately 100 kmh-1), vibration of catalyst cell is probably few g's.
Vibrational excitation from heterogeneous catalysis
International Nuclear Information System (INIS)
Purvis, G.D. III; Redmon, M.J.; Woken, G. Jr.
1979-01-01
Classical trajectories have been used by numerous researchers to investigate the dynamics of exothermic chemical reactions (atom + diatom) with a view toward understanding what leads to vibrational excitation of the product molecule. Unlike these studies, the case where the reaction is catalyzed by a solid surface is considered. The trajectory studies indicate that there should be conditions under which considerable vibrational energy appears in the product molecules without being lost to the solid during the course of the reaction. 2 figures, 3 tables
Vibrational Spectral Studies of Gemfibrozil
Benitta, T. Asenath; Balendiran, G. K.; James, C.
2008-11-01
The Fourier Transform Raman and infrared spectra of the crystallized drug molecule 5-(2,5-Dimethylphenoxy)-2,2-dimethylpentanoic acid (Gemfibrozil) have been recorded and analyzed. Quantum chemical computational methods have been employed using Gaussian 03 software package based on Hartree Fock method for theoretically modeling the grown molecule. The optimized geometry and vibrational frequencies have been predicted. Observed vibrational modes have been assigned with the aid of normal coordinate analysis.
Vibrational anomalies and marginal stability of glasses
Marruzzo, Alessia
2013-01-01
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.
Jeon, Yun-Hee; Simpson, Judy M; Li, Zhicheng; Cunich, Michelle M; Thomas, Tamsin H; Chenoweth, Lynn; Kendig, Hal L
2015-07-01
To evaluate the effectiveness of a leadership and management program in aged care. Double-blind cluster randomized controlled trial. Twelve residential and community-aged care sites in Australia. All care staff employed for 6 months or longer at the aged care sites were invited to participate in the surveys at 3 time points: baseline (time 1), 9 months from baseline (time 2), and 9 months after completion of time 2 (time 3) from 2011 to 2013. At each time point, at least 500 care staff completed a survey. At baseline (N = 503) the largest age group was 45 to 54 years (37%), and the majority of care staff were born in Australia (70%), spoke English (94%), and had at least completed secondary education (57%). A 12-month Clinical Leadership in Aged Care (CLiAC) program for middle managers, which aimed to further develop their leadership and management skills in creating positive workplace relationships and in enabling person-centered, evidence-based care. The primary outcomes were care staff ratings of the work environment, care quality and safety, and staff turnover rates. Secondary outcomes were care staff's intention to leave their employer and profession, workplace stress, job satisfaction, and cost-effectiveness of implementing the program. Absenteeism was excluded due to difficulty in obtaining reliable data. Managers' self-rated knowledge and skills in leadership and management are not included in this article, which focuses on care staff perceptions only. At 6 months after its completion, the CLiAC program was effective in improving care staff's perception of management support [mean difference 0.61, 95% confidence interval (CI) 0.04-1.18; P = .04]. Compared with the control sites, care staff at the intervention sites perceived their managers' leadership styles as more transformational (mean difference 0.30, 95% CI 0.09-0.51; P = .005), transactional (mean difference 0.22, 95% CI 0.05-0.39; P = .01), and less passive avoidant (mean difference 0.30, 95% CI 0
Laser method of acoustical emission control from vibrating surfaces
Motyka, Zbigniew
2013-01-01
For limitation of the noise in environment, the necessity occurs of determining and location of sources of sounds emitted from surfaces of many machines and devices, assuring in effect the possibility of suitable constructional changes implementation, targeted at decreasing of their nuisance. In the paper, the results of tests and calculations are presented for plane surface sources emitting acoustic waves. The tests were realized with the use of scanning laser vibrometer which enabled remote registration and the spectral analysis of the surfaces vibrations. The known hybrid digital method developed for determination of sound wave emission from such surfaces divided into small finite elements was slightly modified by distinguishing the phase correlations between such vibrating elements. The final method being developed may find use in wide range of applications for different forms of vibrations of plane surfaces.
Fiber Bragg Grating vibration sensor with DFB laser diode
Siska, Petr; Brozovic, Martin; Cubik, Jakub; Kepak, Stanislav; Vitasek, Jan; Koudelka, Petr; Latal, Jan; Vasinek, Vladimir
2012-01-01
The Fiber Bragg Grating (FBG) sensors are nowadays used in many applications. Thanks to its quite big sensitivity to a surrounding environment, they can be used for sensing of temperature, strain, vibration or pressure. A fiber Bragg grating vibration sensor, which is interrogated by a distributed feedback laser diode (DFB) is demonstrated in this article. The system is based on the intensity modulation of the narrow spectral bandwidth of the DFB laser, when the reflection spectrum of the FBG sensor is shifted due to the strain that is applied on it in form of vibrations caused by acoustic wave pressure from loud speaker. The sensor's response in frequency domain and strain is measured; also the factor of sensor pre-strain impact on its sensitivity is discussed.
Energy harvesting from vibration using a piezoelectric membrane
Energy Technology Data Exchange (ETDEWEB)
Ericka, M.; Vasic, D.; Costa, F.; Tliba, S. [Ecole Normale Superieure de Cachan, Systemes et Applications des Technologies de l' Information et de l' Energie (SATIE, UMR 8029), 94 - Cachan (France); Poulin, G. [Ecole Nationale Superieure d' Ingenieurs Electriciens de Grenoble, Laboratoire d' Automatique de Grenoble, 38 (France)
2005-09-01
In this paper we investigate the capability of harvesting the electric energy from mechanical vibrations in a dynamic environment through a piezoelectric membrane transducer. This transducer consists of 2 layers lead zirconate titanate (PZT)/brass, the brass layer is embedded over the whole circumference by epoxy adhesive. A very small vibration gives a consequent deformation of the membrane which generates electric energy. Due to the impedance matrices connecting the efforts and flows of the membrane, we have established the dynamic electric equivalent circuit of the transducer. In a first study and in order to validate theoretical results, we performed experiments with a vibrating machine moving a macroscopic 25 mm diameter piezoelectric membrane. A power of 1.8 mW was generated at the resonance frequency (2.58 kHz) across a 56 k{omega} optimal resistor and for a 2 g acceleration. (authors)
Pfeiffer, Tobias; Weber, Stefan; Klier, Jens; Bachtler, Sebastian; Molter, Daniel; Jonuscheit, Joachim; Von Freymann, Georg
2018-05-14
In many industrial fields, like automotive and painting industry, the thickness of thin layers is a crucial parameter for quality control. Hence, the demand for thickness measurement techniques continuously grows. In particular, non-destructive and contact-free terahertz techniques access a wide range of thickness determination applications. However, terahertz time-domain spectroscopy based systems perform the measurement in a sampling manner, requiring fixed distances between measurement head and sample. In harsh industrial environments vibrations of sample and measurement head distort the time-base and decrease measurement accuracy. We present an interferometer-based vibration correction for terahertz time-domain measurements, able to reduce thickness distortion by one order of magnitude for vibrations with frequencies up to 100 Hz and amplitudes up to 100 µm. We further verify the experimental results by numerical calculations and find very good agreement.
Vibration condition monitoring of planetary gearbox under varying external load
Energy Technology Data Exchange (ETDEWEB)
Bartelmus, W.; Zimroz, R. [Wroclaw University of Technology, Wroclaw (Poland)
2009-01-15
The paper shows that for condition monitoring of planetary gearboxes it is important to identify the external varying load condition. In the paper, systematic consideration has been taken of the influence of many factors on the vibration signals generated by a system in which a planetary gearbox is included. These considerations give the basis for vibration signal interpretation, development of the means of condition monitoring, and for the scenario of the degradation of the planetary gearbox. Real measured vibration signals obtained in the industrial environment are processed. The signals are recorded during normal operation of the diagnosed objects, namely planetary gearboxes, which are a part of the driving system used in a bucket wheel excavator, used in lignite mines. It has been found that the most important factor of the proper planetary gearbox condition is connected with perturbation of arm rotation, where an arm rotation gives rise to a specific vibration signal whose properties are depicted by a short-time Fourier transform (STFT) and Wigner-Ville distribution presented as a time-frequency map. The paper gives evidence that there are two dominant low-frequency causes that influence vibration signal modulation, i.e. the varying load, which comes from the nature of the bucket wheel digging process, and the arm/carrier rotation. These two causes determine the condition of the planetary gearboxes considered.
Skyrme RPA description of γ-vibrational states in rare-earth nuclei
Directory of Open Access Journals (Sweden)
Nesterenko V.O.
2016-01-01
Full Text Available The lowest γ-vibrational states with Kπ = 2+γ in well-deformed Dy, Er and Yb isotopes are investigated within the self-consistent separable quasiparticle random-phase-approximation (QRPA approach based on the Skyrme functional. The energies Eγ and reduced transition probabilities B(E2γ of the states are calculated with the Skyrme force SV-mas10. We demonstrate the strong effect of the pairing blocking on the energies of γ-vibrational states. It is also shown that collectivity of γ-vibrational states is strictly determined by keeping the Nilsson selection rules in the corresponding lowest 2qp configurations.
Off-resonant vibrational excitation: Orientational dependence and spatial control of photofragments
DEFF Research Database (Denmark)
Machholm, Mette; Henriksen, Niels Engholm
2000-01-01
Off-resonant and resonant vibrational excitation with short intense infrared (IR) laser pulses creates localized oscillating wave packets, but differs by the efficiency of the excitation and surprisingly by the orientational dependence. Orientational selectivity of the vibrational excitation...... of randomly oriented heteronuclear diatomic molecules can be obtained under simultaneous irradiation by a resonant and an off-resonant intense IR laser pulse: Molecules with one initial orientation will be vibrationally excited, while those with the opposite orientation will be at rest. The orientation-dependent...... distribution. (C) 2000 American Institute of Physics....
Vibrational spectroscopy of proteins
International Nuclear Information System (INIS)
Schwaighofer, A.
2013-01-01
Two important steps for the development of a biosensor are the immobilization of the biological component (e.g. protein) on a surface and the enhancement of the signal to improve the sensitivity of detection. To address these subjects, the present work describes Fourier transform infrared (FTIR) investigations of several proteins bound to the surface of an attenuated total reflection (ATR) crystal. Furthermore, new nanostructured surfaces for signal enhancement were developed for use in FTIR microscopy. The mitochondrial redox-protein cytochrome c oxidase (CcO) was incorporated into a protein-tethered bilayer lipid membrane (ptBLM) on an ATR crystal featuring a roughened two-layer gold surface for signal enhancement. Electrochemical excitation by periodic potential pulses at different modulation frequencies was followed by time-resolved FTIR spectroscopy. Phase sensitive detection was used for deconvolution of the IR spectra into vibrational components. A model based on protonation-dependent chemical reaction kinetics could be fitted to the time evolution of IR bands attributed to several different redox centers of the CcO. Further investigations involved the odorant binding protein 14 (OBP14) of the honey bee (Apis mellifera), which was studied using ATR-FTIR spectroscopy and circular dichroism. OBP14 was found to be thermally stable up to 45 °C, thus permitting the potential application of this protein for the fabrication of biosensors. Thermal denaturation measurements showed that odorant binding increases the thermal stability of the OBP-odorant complex. In another project, plasmonic nanostructures were fabricated that enhance the absorbance in FTIR microscopy measurements. The nanostructures are composed of an array of round-shaped insulator and gold discs on top of a continuous gold layer. Enhancement factors of up to ⁓125 could be observed with self-assembled monolayers of dodecanethiol molecules immobilized on the gold surface (author) [de
1980-09-01
Smallwood and D. L. Gregory, Sandia Laboratories, Albuquerque, NM A NEW METHOD OF IMPROVING SPECTRA SHAPING IN REVERBERANT CHAMBERS...DAMPING M. M. Wallace and C. W. Bert, The University of Oklahoma, Norman , OK CONTRIBUTIONS TO THE DYNAMIC ANALYSIS OF MAGLEV VEHICLES ON ELEVATED GUIDEWAYS...RANDOM VIBRATION EXTRENAL CONTROL STRATEGY D. 0. Smallwood D. L. Gregory Sandia Laboratories Albuquerque, NM This paper discusses the theoretical basis for
Fisher, J; Van-Dongen, M; Sutherland, R
2015-09-01
Research considering combined vibration and strength training is extensive yet results are equivocal. However, to date there appears no research which has considered the combination of both direct vibration and whole-body vibration when used in an isometric deadlift position. The aim of this study was to compare groups performing isometric training with and without direct and whole-body vibration. Twenty four participants (19-24 years) were randomly divided into: isometric training with vibration (ST+VT: N.=8), isometric training without vibration (ST: N.=8), and control (CON: N.=8). Within the training groups participants trained twice per week, for 6 weeks, performing 6-sets of maximal isometric deadlift contractions, increasing in duration from 30 seconds to 40 seconds (weeks 1-6). Hip and knee angle was maintained at 60° and 110°, respectively for both testing and training. Training sessions for ST+VT were identical to ST with the addition of a direct vibratory stimulus through hand-held straps and whole-body vibration via standing on vibration a platform. The amplitude remained constant (2 mm) throughout the intervention whilst the frequency increased from 35Hz to 50Hz. Pre- and post-test isometric strength was measured using an isometric deadlift dynamometer. Results revealed significant increases in isometric strength for both ST+VT (Pstrength training.
Ferguson, Steven L; Kim, Eonho; Seo, Dong-Il; Bemben, Michael G
2013-12-01
This study compared the effects of 3 weeks of upper-body vibration training, vibration and stretching, and stretching alone on shoulder flexibility in college-aged men. Twenty-one men were randomly assigned to vibration-stretching (VS; n = 8), vibration only (VO; n = 6), or stretching only (SO; n = 7) groups that trained 3 times per week for 3 weeks. All 3 groups performed 9 total sets of 30-second stretches. The VS group performed four 30-second upper-body vibration exercises and five 30-second upper-body stretching exercises. The VO group performed nine 30-second upper-body vibration exercises. The SO group performed nine 30-second upper-body stretching exercises. Shoulder flexion (SF), shoulder extension (SE), and shoulder transverse extension (STE) were assessed by a Leighton Flexometer and back scratch tests bilaterally (BSR, BSL) were measured via tape measure. A 1-way analysis of variance (ANOVA) evaluated groups at baseline and a 2-way repeated-measures ANOVA evaluated the interventions over time. At baseline, there were no group differences in age, height, or weight. There was a significant (p alone or combined with stretching, is a viable alternative to a standard stretching routine when attempting to increase shoulder flexibility. Adding vibration training to a flexibility regimen may improve the likelihood of regularly performing flexibility sessions because of increased variety.
Entropy for Mechanically Vibrating Systems
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
Energy expenditure and substrate utilization during whole body vibration
Directory of Open Access Journals (Sweden)
Ravena Santos Raulino
2015-04-01
Full Text Available INTRODUCTION AND OBJECTIVE: the aim of this study was to investigate whether the addition of vibration during interval training would raise oxygen consumption VO2 to the extent necessary for weight management and to evaluate the influence of the intensity of the vibratory stimulus for prescribing the exercise program in question. METHODS: VO2, measured breath by breath, was evaluated at rest and during the four experimental conditions to determine energy expenditure, metabolic equivalent MET, respiratory exchange ratio RER, % Kcal from fat, and rate of fat oxidation. Eight young sedentary females age 22±1 years, height 163.88± 7.62 cm, body mass 58.35±10.96 kg, and VO2 max 32.75±3.55 mLO2.Kg-1.min-1 performed interval training duration = 13.3 min to the upper and lower limbs both with vibration 35 Hz and 2 mm, 40 Hz and 2 mm, 45 Hz and 2 mm and without vibration. The experimental conditions were randomized and balanced at an interval of 48 hours. RESULTS: the addition of vibration to exercise at 45 Hz and 2 mm resulted in an additional increase of 17.77±12.38% of VO2 compared with exercise without vibration. However, this increase did not change the fat oxidation rate p=0.42 because intensity of exercise 29.1±3.3 %VO2max, 2.7 MET was classified as mild to young subjects. CONCLUSION: despite the influence of vibration on VO2 during exercise, the increase was insufficient to reduce body weight and did not reach the minimum recommendation of exercise prescription for weight management for the studied population.
PC based vibration monitoring system
International Nuclear Information System (INIS)
Jain, Sanjay K.; Roy, D.A.; Pithawa, C.K.; Patil, R.K.
2004-01-01
Health of large rotating machinery gets reflected in the vibration signature of the rotor and supporting structures and proper recording of these signals and their analysis can give a clear picture of the health of the machine. Using these data and their trending, it is possible to predict an impending trouble in the machine so that preventive action can be taken in time and catastrophic failure can be avoided. Continuous monitoring and analysis can give quick warning and enable operator to take preventive measures. Reactor Control Division, BARC is developing a PC based Vibration monitoring system for turbo generator machinery. The System can acquire 20 vibration signals at a rate of 5000 samples per second and also 15 process signals at a rate of 100 samples/ sec. The software for vibration monitoring system includes acquisition modules, analysis modules and Graphical User Interface module. The acquisition module involves initialization, setting of required parameters and acquiring the data from PC-based data acquisition cards. The acquired raw vibration data is then stored for analysis using various software packages. The display and analysis of acquired data is done in LabVIEW 7.0 where the data is displayed in time as well as frequency domain along with the RMS value of the signal. (author)
The influence of noise and vibration upon creatine kinase activity in blood serum
Energy Technology Data Exchange (ETDEWEB)
Jonderko, G; Gabryel, A; Jonderko, K; Konca, A; Marcisz, C; Olak, Z; Szramek-Urbaniak, A
1982-02-01
The investigations comprised part of the workers employed in a factory of prefabricated concrete elements. The creatine kinase (CK) activity was determined before and after a day's work in the following groups of workers: These exposed to noise and vibration exceeding the allowed norm; those exposed to noise, performing the same hard physical work as group I and exposed to vibration not exceeding 79dB in particular octave bands, and those practising physical work a group I and II but in environment free from noise and vibration, and a control group of persons not exposed to any of the tested factors (vibration, noise, work). The obtained results indicate that the determination of the CK activity may serve as a test of exposure to vibration and noise.
On generalized fractional vibration equation
International Nuclear Information System (INIS)
Dai, Hongzhe; Zheng, Zhibao; Wang, Wei
2017-01-01
Highlights: • The paper presents a generalized fractional vibration equation for arbitrary viscoelastically damped system. • Some classical vibration equations can be derived from the developed equation. • The analytic solution of developed equation is derived under some special cases. • The generalized equation is particularly useful for developing new fractional equivalent linearization method. - Abstract: In this paper, a generalized fractional vibration equation with multi-terms of fractional dissipation is developed to describe the dynamical response of an arbitrary viscoelastically damped system. It is shown that many classical equations of motion, e.g., the Bagley–Torvik equation, can be derived from the developed equation. The Laplace transform is utilized to solve the generalized equation and the analytic solution under some special cases is derived. Example demonstrates the generalized transfer function of an arbitrary viscoelastic system.
General vibration monitoring: Experimental hall
International Nuclear Information System (INIS)
Jendrzejczyk, J.A.; Wambsganss, M.W.; Smith, R.K.
1993-01-01
The reported vibration data were generated from measurements made on the experimental hall floor on December 2, 1992. At the time of the measurements, the ESRF hydrolevel was set-up in the Early Assembly Area (EAA) of the experimental hall and was being used to measure static displacement (settlement) of the floor. The vibration measurement area was on and adjacent to the EAA, in the vicinity of the ESRF hydrolevel test which was in progress. This report summarizes the objectives, instrumentation, measurement locations, observations, and conclusions, and provides selected results in the form of RMS vs. time plots, and power spectral densities from which frequency information can be derived. Measured response amplitudes were within the vibration criteria established for the APS
Edgington, Eugene
2007-01-01
Statistical Tests That Do Not Require Random Sampling Randomization Tests Numerical Examples Randomization Tests and Nonrandom Samples The Prevalence of Nonrandom Samples in Experiments The Irrelevance of Random Samples for the Typical Experiment Generalizing from Nonrandom Samples Intelligibility Respect for the Validity of Randomization Tests Versatility Practicality Precursors of Randomization Tests Other Applications of Permutation Tests Questions and Exercises Notes References Randomized Experiments Unique Benefits of Experiments Experimentation without Mani
Vibration damage testing of thermal barrier fibrous blanket insulation
International Nuclear Information System (INIS)
Black, W.E.; Betts, W.S.
1984-01-01
GA Technologies is engaged in a long-term, multiphase program to determine the vibration characteristics of thermal barrier components leading to qualification of assemblies for High Temperature Gas-Cooled Reactor (HTGR) service. The phase of primary emphasis described herein is the third in a series of acoustic tests and uses as background the more elemental tests preceding it. Two sizes of thermal barrier coverplates with one fibrous blanket insulation type were tested in an acoustic environment at sound pressure levels up to 160 dB. Three tests were conducted using sinusoidal and random noise for up to 200 h duration at room temperature. Frequent inspections were made to determine the progression of degradation using definition of stages from a prior test program. Initially the insulation surface adjacent to the metallic seal sheets (noise side) assumed a chafed or polished appearance. This was followed by flattening of the as-received pillowed surface. This stage was followed by a depression being formed in the vicinity of the free edge of the coverplate. Next, loose powder from within the blanket and from fiber erosion accumulated in the depression. Prior experience showed that the next stage of deterioration exhibited a consolidation of the powder to form a local crust. In this test series, this last stage generally failed to materialize. Instead, surface holes generated by solid ceramic particulates (commonly referred to as 'shot') constituted the stage following powdering. With the exception of some manufacturing-induced anomalies, the final stage, namely, gross fiber breakup, did not occur. It is this last stage that must be prevented for the thermal barrier to maintain its integrity. (orig./GL)
The Shock and Vibration Bulletin. Part 2. Vibration Analysis.
1977-09-01
J.N. Tait, Naval Air Development Center, Warminster, PA EVALUATION OF AN ADAPTIVE FILTER AS A DIGITAL TRACKING FILTER D.O. Smallwood and D.L. Gregory...Oklahoma Norman , Oklahoma In contrast to the considerable information abailable on free vibration of isotropic plates, there is only a very limited
Vibration Analysis for Steam Dryer of APR1400 Steam Generator
Energy Technology Data Exchange (ETDEWEB)
Han, Sung-heum; Ko, Doyoung [KHNP CRI, Daejeon (Korea, Republic of); Cho, Minki [Doosan Heavy Industry, Changwon (Korea, Republic of)
2016-10-15
This paper is related to comprehensive vibration assessment program for APR1400 steam generator internals. According to U.S. Nuclear Regulatory Commission, Regulatory Guide 1.20 (Rev.3, March 2007), we conducted vibration analysis for a steam dryer as the second steam separator of steam generator internals. The vibration analysis was performed at the 100 % power operating condition as the normal operation condition. The random hydraulic loads were calculated by the computational fluid dynamics and the structural responses were predicted by power spectral density analysis for the probabilistic method. In order to meet the recently revised U.S. NRC RG 1.20 Rev.3, the CVAP against the potential adverse flow effects in APR1400 SG internals should be performed. This study conducted the vibration response analysis for the SG steam dryer as the second moisture separator at the 100% power condition, and evaluated the structural integrity. The predicted alternating stress intensities were evaluated to have more than 17.78 times fatigue margin compared to the endurance limit.
Uncertainty Quantification for Monitoring of Civil Structures from Vibration Measurements
Döhler, Michael; Mevel, Laurent
2014-05-01
Health Monitoring of civil structures can be performed by detecting changes in the modal parameters of a structure, or more directly in the measured vibration signals. For a continuous monitoring the excitation of a structure is usually ambient, thus unknown and assumed to be noise. Hence, all estimates from the vibration measurements are realizations of random variables with inherent uncertainty due to (unknown) process and measurement noise and finite data length. In this talk, a strategy for quantifying the uncertainties of modal parameter estimates from a subspace-based system identification approach is presented and the importance of uncertainty quantification in monitoring approaches is shown. Furthermore, a damage detection method is presented, which is based on the direct comparison of the measured vibration signals without estimating modal parameters, while taking the statistical uncertainty in the signals correctly into account. The usefulness of both strategies is illustrated on data from a progressive damage action on a prestressed concrete bridge. References E. Carden and P. Fanning. Vibration based condition monitoring: a review. Structural Health Monitoring, 3(4):355-377, 2004. M. Döhler and L. Mevel. Efficient multi-order uncertainty computation for stochastic subspace identification. Mechanical Systems and Signal Processing, 38(2):346-366, 2013. M. Döhler, L. Mevel, and F. Hille. Subspace-based damage detection under changes in the ambient excitation statistics. Mechanical Systems and Signal Processing, 45(1):207-224, 2014.
Shock and Vibration. Volume 1, Issue 1
National Research Council Canada - National Science Library
Pilkey, Walter D
1994-01-01
..., and earthquake engineering. Among the specific areas to be covered are vibration testing and control, vibration condition monitoring and diagnostics, shock hardenings, modal technology, shock testing, data acquisition, fluid...
Novel active vibration absorber with magnetorheological fluid
Energy Technology Data Exchange (ETDEWEB)
Gerlach, T; Ehrlich, J; Boese, H [Fraunhofer-Institut fuer Silicatforschung ISC, Neunerplatz 2, D-97082 Wuerzburg (Germany)], E-mail: thomas.gerlach@isc.fraunhofer.de
2009-02-01
Disturbing vibrations diminish the performance of technical high precision devices significantly. In search of a suitable solution for reducing these vibrations, a novel concept of active vibration reduction was developed which exploits the special properties of magnetorheological fluids. In order to evaluate the concept of such an active vibration absorber (AVA) a demonstrator was designed and manufactured. This demonstrator generates a force which counteracts the motion of the vibrating body. Since the counterforce is generated by a centrifugal exciter, the AVA provides the capability to compensate vibrations even in two dimensions. To control the strength of the force transmitted to the vibrating body, the exciter is based on a tunable MR coupling. The AVA was integrated in an appropriate testing device to investigate its performance. The recorded results show a significant reduction of the vibration amplitudes by an order of magnitude.
Isotope separation using vibrationally excited molecules
International Nuclear Information System (INIS)
1979-01-01
This invention relates to isotope separation employing isotopically selective vibrational excitation and vibration-translation reactions of the excited particles. Uranium enrichment, using uranium hexafluoride, is a particular embodiment. (U.K.)
Application of eigenfunction orthogonalities to vibration problems
CSIR Research Space (South Africa)
Fedotov, I
2009-07-01
Full Text Available The modelling of vibration problems is of great importance in engineering. A popular method of analysing such problems is the variational method. The simplest vibration model is represented using the example of a long rod. Two kinds...
Combined Effects of High-Speed Railway Noise and Ground Vibrations on Annoyance.
Yokoshima, Shigenori; Morihara, Takashi; Sato, Tetsumi; Yano, Takashi
2017-07-27
The Shinkansen super-express railway system in Japan has greatly increased its capacity and has expanded nationwide. However, many inhabitants in areas along the railways have been disturbed by noise and ground vibration from the trains. Additionally, the Shinkansen railway emits a higher level of ground vibration than conventional railways at the same noise level. These findings imply that building vibrations affect living environments as significantly as the associated noise. Therefore, it is imperative to quantify the effects of noise and vibration exposures on each annoyance under simultaneous exposure. We performed a secondary analysis using individual datasets of exposure and community response associated with Shinkansen railway noise and vibration. The data consisted of six socio-acoustic surveys, which were conducted separately over the last 20 years in Japan. Applying a logistic regression analysis to the datasets, we confirmed the combined effects of vibration/noise exposure on noise/vibration annoyance. Moreover, we proposed a representative relationship between noise and vibration exposures, and the prevalence of each annoyance associated with the Shinkansen railway.
An introduction to random vibrations, spectral & wavelet analysis
Newland, D E
2005-01-01
One of the first engineering books to cover wavelet analysis, this classic text describes and illustrates basic theory, with a detailed explanation of the workings of discrete wavelet transforms. Computer algorithms are explained and supported by examples and a set of problems, and an appendix lists ten computer programs for calculating and displaying wavelet transforms.Starting with an introduction to probability distributions and averages, the text examines joint probability distributions, ensemble averages, and correlation; Fourier analysis; spectral density and excitation response relation
Design, simulation, fabrication, and characterization of MEMS vibration energy harvesters
Oxaal, John
Energy harvesting from ambient sources has been a longtime goal for microsystem engineers. The energy available from ambient sources is substantial and could be used to power wireless micro devices, making them fully autonomous. Self-powered wireless sensors could have many applications in for autonomous monitoring of residential, commercial, industrial, geological, or biological environments. Ambient vibrations are of particular interest for energy harvesting as they are ubiquitous and have ample kinetic energy. In this work a MEMS device for vibration energy harvesting using a variable capacitor structure is presented. The nonlinear electromechanical dynamics of a gap-closing type structure is experimentally studied. Important experimental considerations such as the importance of reducing off-axis vibration during testing, characterization methods, dust contamination, and the effect of grounding on parasitic capacitance are discussed. A comprehensive physics based model is developed and validated with two different microfabricated devices. To achieve maximal power, devices with high aspect ratio electrodes and a novel two-level stopper system are designed and fabricated. The maximum achieved power from the MEMS device when driven by sinusoidal vibrations was 3.38 muW. Vibrations from HVAC air ducts, which have a primary frequency of 65 Hz and amplitude of 155 mgrms, are targeted as the vibration source and devices are designed for maximal power harvesting potential at those conditions. Harvesting from the air ducts, the devices reached 118 nW of power. When normalized to the operating conditions, the best figure of merit of the devices tested was an order of magnitude above state-of-the-art of the devices (1.24E-6).
Neurocognitive responses to a single session of static squats with whole body vibration.
Amonette, William E; Boyle, Mandy; Psarakis, Maria B; Barker, Jennifer; Dupler, Terry L; Ott, Summer D
2015-01-01
The purpose of this study was to determine if the head accelerations using a common whole body vibration (WBV) exercise protocol acutely reduced neurocognition in healthy subjects. Second, we investigated differential responses to WBV plates with 2 different delivery mechanisms: vertical and rotational vibrations. Twelve healthy subjects (N = 12) volunteered and completed a baseline (BASE) neurocognitive assessment: the Immediate Postconcussion Assessment and Cognitive Test (ImPACT). Subjects then participated in 3 randomized exercise sessions separated by no more than 2 weeks. The exercise sessions consisted of five 2-minute sets of static hip-width stance squats, with the knees positioned at a 45° angle of flexion. The squats were performed with no vibration (control [CON]), with a vertically vibrating plate (vertical vibration [VV]), and with a rotational vibrating plate (rotational vibration [RV]) set to 30 Hz with 4 mm of peak-to-peak displacement. The ImPACT assessments were completed immediately after each exercise session and the composite score for 5 cognitive domains was analyzed: verbal memory, visual memory, visual motor speed, reaction time, and impulse control. Verbal memory scores were unaffected by exercise with or without vibration (p = 0.40). Likewise, visual memory was not different (p = 0.14) after CON, VV, or RV. Significant differences were detected for visual motor speed (p = 0.006); VV was elevated compared with BASE (p = 0.01). There were no significant differences (p = 0.26) in reaction time or impulse control (p = 0.16) after exercise with or without vibration. In healthy individuals, 10 minutes of 30 Hz, 4-mm peak-to-peak displacement vibration exposure with a 45° angle of knee flexion did not negatively affect neurocognition.
Whole-Body Vibrations Associated With Alpine Skiing: A Risk Factor for Low Back Pain?
Directory of Open Access Journals (Sweden)
Matej Supej
2018-03-01
Full Text Available Alpine skiing, both recreational and competitive, is associated with high rates of injury. Numerous studies have shown that occupational exposure to whole-body vibrations is strongly related to lower back pain and some suggest that, in particular, vibrations of lower frequencies could lead to overuse injuries of the back in connection with alpine ski racing. However, it is not yet known which forms of skiing involve stronger vibrations and whether these exceed safety thresholds set by existing standards and directives. Therefore, this study was designed to examine whole-body vibrations connected with different types of skiing and the associated potential risk of developing low back pain. Eight highly skilled ski instructors, all former competitive ski racers and equipped with five accelerometers and a Global Satellite Navigation System to measure vibrations and speed, respectively, performed six different forms of skiing: straight running, plowing, snow-plow swinging, basic swinging, short swinging, and carved turns. To estimate exposure to periodic, random and transient vibrations the power spectrum density (PSD and standard ISO 2631-1:1997 parameters [i.e., the weighted root-mean-square acceleration (RMS, crest factor, maximum transient vibration value and the fourth-power vibration dose value (VDV] were calculated. Ground reaction forces were estimated from data provided by accelerometers attached to the pelvis. The major novel findings were that all of the forms of skiing tested produced whole-body vibrations, with highest PSD values of 1.5–8 Hz. Intensified PSD between 8.5 and 35 Hz was observed only when skidding was involved. The RMS values for 10 min of short swinging or carved turns, as well as all 10-min equivalent VDV values exceeded the limits set by European Directive 2002/44/EC for health and safety. Thus, whole-body vibrations, particularly in connection with high ground reaction forces, contribute to a high risk for low back
Experimental studies on flow-induced vibration to support steam generator design
International Nuclear Information System (INIS)
Pettigrew, M.J.; Gorman, D.J.
1977-06-01
Vibration experiments were done on small tube bundles of triangular and square lattice configurations in both liquid and two-phase (air-water) cross-flow. The effects of flow velocity, simulated steam quality, lattice orientation, tube location and tube frequency were explored. Tube response to random flow turbulence excitation and fluidelastic instability were observed in both liquid and two-phase cross-flow. Fluidelastic instability criteria and random forcing function characterizations are derived from this work. This information may be used in the vibration analysis of shell-and-tube heat exchanger components. (author)
An overview of the Canadian program to investigate vibration and fretting in nuclear fuel assemblies
International Nuclear Information System (INIS)
Oldaker, I.E.; Lane, A.D.; Forrest, C.F.
The development of a model that would allow the fuel designer to predict the occurrence of fretting could materially reduce the amount of development testing of a new fuel design. To achieve this, we are working in several areas: to identify and measure the phenomena that excite fuel to vibrate, and to study their relation to reactor design features; to predict the vibratory response of a fuel assembly as a function of its design and environment, and; to study the relationship between vibration and fretting to determine when vibration results in fretting. (author)
Vibrational properties of amorphous semiconductors
International Nuclear Information System (INIS)
Schulz, P.A.B.
1985-01-01
A model for the lattice dynamics of a-Si 1-X N X is introduced. This model is based on a Born hamiltonian, solved in the Bethe lattice approximation. Starting from the local density of vibrational states, we analize the infrared absoption spectra of this material. (author) [pt
Ultrafast vibrations of gold nanorings
DEFF Research Database (Denmark)
Kelf, T; Tanaka, Y; Matsuda, O
2011-01-01
We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We...
Monothiodibenzoylmethane: Structural and vibrational assignments
DEFF Research Database (Denmark)
Hansen, Bjarke Knud Vilster; Gorski, Alexander; Posokhov, Yevgen
2007-01-01
vibrational spectra were compared with theoretical transitions obtained with B3LYP/cc-pVTZ density functional theory (DFT). The results leave no doubt that the stable ground state configuration of TDBM corresponds to the intramolecularly hydrogen bonded enol form (e-CCC), and that the photoproduct corresponds...
Low-Vibration Oscillating Compressor
Studer, P. A.
1984-01-01
Oscillating compressor momentum compensated: produces little vibration in its supporting structure. Compressure requires no lubrication and virtually free of wear. Compresses working fluids such as helium, nitrogen or chlorfluorocarbons for Stirling-cycle refrigeration or other purposes. Compressor includes two mutually opposed ferromagnetic pistons of same shape and mass. Electromagnetic flux links both pistons, causing magnetic attraction between them.
Vibrational relaxation in OCS mixtures
International Nuclear Information System (INIS)
Simpson, C.J.S.M.; Gait, P.D.; Simmie, J.M.
1976-01-01
Experimental measurements are reported of vibrational relaxation times which may be used to show whether there is near resonant vibration-rotation energy transfer between OCS and H 2 , D 2 or HD. Vibrational relaxation times have been measured in OCS and OCS mixtures over the temperature range 360 to 1000 K using a shock tube and a laser schlieren system. The effectiveness of the additives in reducing the relaxation time of OCS is in the order 4 He 3 He 2 2 and HD. Along this series the effect of an increase in temperature changes from the case of speeding up the rate with 4 He to retarding it with D 2 , HD and H 2 . There is no measurable difference in the effectiveness of n-D 2 and o-D 2 and little, or no, difference between n-H 2 and p-H 2 . Thus the experimental results do not give clear evidence for rotational-vibration energy transfer between hydrogen and OCS. This contrasts with the situation for CO 2 + H 2 mixtures. (author)
Vibrational entropies in metallic alloys
Ozolins, Vidvuds; Asta, Mark; Wolverton, Christopher
2000-03-01
Recently, it has been recognized that vibrational entropy can have significant effects on the phase stability of metallic alloys. Using density functional linear response calculations and molecular dynamics simulations we study three representative cases: (i) phase diagram of Al-rich Al-Sc alloys, (ii) stability of precipitate phases in CuAl_2, and (iii) phonon dynamics in bcc Zr. We find large vibrational entropy effects in all cases. In the Al-Sc system, vibrations increase the solid solubility of Sc in Al by decreasing the stability of the L12 (Al_3Sc) phase. This leads to a nearly ten-fold increase in the solid solubility of Sc in Al at T=800 K. In the Cu-Al system, our calculations predict that the tetragonal Laves phase of CuAl2 has 0.35 kB/atom higher vibrational entropy than the cubic CaF_2-type phase (the latter is predicted to be the T=0 K ground state of CuAl_2). This entropy difference causes a structural transformation in CuAl2 precipitates from the fluorite to the tetragonal Laves phase around T=500 K. Finally, we analyze the highly unusual dynamics of anharmonically stabilized bcc Zr, finding large diffuse-scattering intensity streaks between the bcc Bragg peaks.
Ultrafast vibrations of gold nanorings
DEFF Research Database (Denmark)
Kelf, T; Tanaka, Y; Matsuda, O
2011-01-01
We investigate the vibrational modes of gold nanorings on a silica substrate with an ultrafast optical technique. By comparison with numerical simulations, we identify several resonances in the gigahertz range associated with axially symmetric deformations of the nanoring and substrate. We elucid...
Autonomous Byte Stream Randomizer
Paloulian, George K.; Woo, Simon S.; Chow, Edward T.
2013-01-01
Net-centric networking environments are often faced with limited resources and must utilize bandwidth as efficiently as possible. In networking environments that span wide areas, the data transmission has to be efficient without any redundant or exuberant metadata. The Autonomous Byte Stream Randomizer software provides an extra level of security on top of existing data encryption methods. Randomizing the data s byte stream adds an extra layer to existing data protection methods, thus making it harder for an attacker to decrypt protected data. Based on a generated crypto-graphically secure random seed, a random sequence of numbers is used to intelligently and efficiently swap the organization of bytes in data using the unbiased and memory-efficient in-place Fisher-Yates shuffle method. Swapping bytes and reorganizing the crucial structure of the byte data renders the data file unreadable and leaves the data in a deconstructed state. This deconstruction adds an extra level of security requiring the byte stream to be reconstructed with the random seed in order to be readable. Once the data byte stream has been randomized, the software enables the data to be distributed to N nodes in an environment. Each piece of the data in randomized and distributed form is a separate entity unreadable on its own right, but when combined with all N pieces, is able to be reconstructed back to one. Reconstruction requires possession of the key used for randomizing the bytes, leading to the generation of the same cryptographically secure random sequence of numbers used to randomize the data. This software is a cornerstone capability possessing the ability to generate the same cryptographically secure sequence on different machines and time intervals, thus allowing this software to be used more heavily in net-centric environments where data transfer bandwidth is limited.
Vibration characteristics of tubes in a heat exchanger
International Nuclear Information System (INIS)
Simonis; Steininger, D.
1985-01-01
Circumferential tube cracking has occurred in the once-through steam generators used in nuclear power plants. Analyses of failed tubes indicate that a fatigue process induced by tube vibration could cause the leaks. To investigate the vibration amplitude of tube spans during reactor operation, twenty-three tube spans were instrumented with accelerometers and strain gages at Three Mile Island Unit 2. To aid in the interpretation of the operational vibration measurements, tests were performed, in air, to determine the predominant resonant frequencies and mode shapes of selected tubes. By adapting modal analysis techniques, the two predominant response frequencies were determined for 100 randomly selected tube spans and the 23 instrumented tube spans; plus, the predominant mode shape was determined for five tube spans bounded by the tube sheet and the fifteenth support plate and one tube span bounded by the ninth and tenth support plate. The average value for the first and second predominant response frequency was 65 Hz and 170 Hz, respectively. The predominant frequencies for the individual tube spans are distributed randomly with no spatial orientation. The first predominant mode shape for the six tube spans tested corresponded to a classical beam with elastic supports. The equivalent stiffness of the elastic supports depend upon the tube span tested
Effect of shelf aging on vibration transmissibility of anti-vibration gloves
SHIBATA, Nobuyuki
2017-01-01
Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 yr of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves. PMID:28978817
Directory of Open Access Journals (Sweden)
Gao Joseph
2010-06-01
Full Text Available Abstract Background Duration of efficacy and safety of lisdexamfetamine dimesylate (LDX was assessed in adults (18-55 years with attention-deficit/hyperactivity disorder (ADHD using the simulated adult workplace environment. Methods After open-label dose optimization (4-week with LDX, 30-70 mg/d, subjects entered a 2-week randomized, double-blind, placebo-controlled crossover phase. Efficacy assessments included the Permanent Product Measure of Performance (PERMP total score (attempted+correct measured predose and from 2 to 14 hours postdose, averaged across postdose sessions (primary and at each time point vs placebo (secondary, and ADHD Rating Scale IV (ADHD-RS-IV with adult prompts at baseline and crossover visits. Safety assessments included treatment-emergent adverse events (TEAEs, vital signs, and electrocardiograms. Results Of 127 randomized subjects, 105 were in the intention-to-treat population and 103 completed the study. While receiving LDX vs placebo, adults had greater improvement (P P ≤ .0017 for each time point and change from predose (P P Conclusions LDX significantly improved PERMP scores vs placebo and maintained improvement throughout the day from the first (2 hours to last (14 hours postdose time point vs placebo in adults with ADHD. Trial Registration ClinicalTrials.gov Identifier: NCT00697515 Safety and Efficacy Workplace Environment Study of Lisdexamfetamine Dimesylate (LDX in Adults With Attention-Deficit Hyperactivity Disorder (ADHD http://www.clinicaltrials.gov/ct2/show/NCT00697515?term=NCT00697515&rank=1
The Standard Deviation of Launch Vehicle Environments
Yunis, Isam
2005-01-01
Statistical analysis is used in the development of the launch vehicle environments of acoustics, vibrations, and shock. The standard deviation of these environments is critical to accurate statistical extrema. However, often very little data exists to define the standard deviation and it is better to use a typical standard deviation than one derived from a few measurements. This paper uses Space Shuttle and expendable launch vehicle flight data to define a typical standard deviation for acoustics and vibrations. The results suggest that 3dB is a conservative and reasonable standard deviation for the source environment and the payload environment.
Blaya, Joaquín A; Shin, Sonya S; Yagui, Martin; Contreras, Carmen; Cegielski, Peter; Yale, Gloria; Suarez, Carmen; Asencios, Luis; Bayona, Jaime; Kim, Jihoon; Fraser, Hamish S F
2014-01-01
Lost, delayed or incorrect laboratory results are associated with delays in initiating treatment. Delays in treatment for Multi-Drug Resistant Tuberculosis (MDR-TB) can worsen patient outcomes and increase transmission. The objective of this study was to evaluate the impact of a laboratory information system in reducing delays and the time for MDR-TB patients to culture convert (stop transmitting). 78 primary Health Centers (HCs) in Lima, Peru. Participants lived within the catchment area of participating HCs and had at least one MDR-TB risk factor. The study design was a cluster randomized controlled trial with baseline data. The intervention was the e-Chasqui web-based laboratory information system. Main outcome measures were: times to communicate a result; to start or change a patient's treatment; and for that patient to culture convert. 1671 patients were enrolled. Intervention HCs took significantly less time to receive drug susceptibility test (DST) (median 11 vs. 17 days, Hazard Ratio 0.67 [0.62-0.72]) and culture (5 vs. 8 days, 0.68 [0.65-0.72]) results. The time to treatment was not significantly different, but patients in intervention HCs took 16 days (20%) less time to culture convert (p = 0.047). The eChasqui system reduced the time to communicate results between laboratories and HCs and time to culture conversion. It is now used in over 259 HCs covering 4.1 million people. This is the first randomized controlled trial of a laboratory information system in a developing country for any disease and the only study worldwide to show clinical impact of such a system. ClinicalTrials.gov NCT01201941.
Yang, Feng; Munoz, Jose; Han, Long-Zhu; Yang, Fei
2017-05-24
This study examined the effects of controlled whole-body vibration training on reducing risk of slip-related falls in people with obesity. Twenty-three young adults with obesity were randomly assigned into either the vibration or placebo group. The vibration and placebo groups respectively received 6-week vibration and placebo training on a side-alternating vibration platform. Before and after the training, the isometric knee extensors strength capacity was measured for the two groups. Both groups were also exposed to a standardized slip induced by a treadmill during gait prior to and following the training. Dynamic stability and fall incidences responding to the slip were also assessed. The results indicated that vibration training significantly increased the muscle strength and improved dynamic stability control at recovery touchdown after the slip occurrence. The improved dynamic stability could be resulted from the enhanced trunk segment movement control, which may be attributable to the strength increment caused by the vibration training. The decline of the fall rates from the pre-training slip to the post-training one was greater among the vibration group than the placebo group (45% vs. 25%). Vibration-based training could be a promising alternative or additional modality to active exercise-based fall prevention programs for people with obesity. Copyright © 2017 Elsevier Ltd. All rights reserved.
Contact parameter identification for vibrational response variability prediction
DEFF Research Database (Denmark)
Creixell Mediante, Ester; Brunskog, Jonas; Jensen, Jakob Søndergaard
2018-01-01
industry, where the vibrational behavior of the structures within the hearing frequency range is critical for the performance of the devices. A procedure to localize the most probable contact areas and determine the most sensitive contact points with respect to variations in the modes of vibration......Variability in the dynamic response of assembled structures can arise due to variations in the contact conditions between the parts that conform them. Contact conditions are difficult to model accurately due to randomness in physical properties such as contact surface, load distribution...... or geometric details. Those properties can vary for a given structure due to the assembly and disassembly process, and also across nominally equal items that are produced in series. This work focuses on modeling the contact between small light-weight plastic pieces such as those used in the hearing aid...
Geometric Filtering Effect of Vertical Vibrations in Railway Vehicles
Directory of Open Access Journals (Sweden)
Mădălina Dumitriu
2012-09-01
Full Text Available The paper herein examines the geometric filtering effect coming from the axle base of a railway vehicle upon the vertical vibrations behavior, due to the random irregularities of the track. For this purpose, the complete model of a two-level suspension and flexible carbody vehicle has been taken into account. Following the modal analysis, the movement equations have been treated in an original manner and brought to a structure that points out at the symmetrical and anti-symmetrical decoupled movements of vehicle and their excitation modes. There has been shown that the geometric filtering has a selective behavior in decreasing the level of vibrations, and its contribution is affected by the axle base magnitude, rolling speed and frequency range.
Calculation of the ex-core neutron noise induced by fuel vibrations in PWRs
International Nuclear Information System (INIS)
Tran Hoai Nam; Cao Van Chung; Hoang Thanh Phi Hung; Hoang Van Khanh
2015-01-01
Calculation of the neutron noise induced by fuel assembly vibrations in two pressurized water reactor (PWR) cores has been performed to investigate the effect of cycle burnup on the properties of the ex-core detector noise. Pendular vibrations of individual fuel assemblies were assumed to occur at different locations in the core. The auto power spectra density (APSD) of the ex-core detector noise was evaluated with the assumption of stochastic vibrations along a random two-dimensional trajectory. The results show that no general monotonic variation of APSD was found. The increase of APSD occurs predominantly for peripheral assemblies. Assuming simultaneous vibrations of a number of fuel assemblies uniformly distributed over the core with the more realistic perturbation model, the effect of the peripheral assemblies will dominate and the increase of the amplitude of the ex-core neutron noise with burnup can be confirmed. (author)
Experience in WWER fuel assemblies vibration analysis
International Nuclear Information System (INIS)
Ovtcharov, O.; Pavelko, V.; Usanov, A.; Arkadov, G.; Dolgov, A.; Molchanov, V.
2003-01-01
It is stated that the vibration studies of internals and the fuel assemblies should be conducted during the reactor designing, commissioning and commercial operation stages and the analysis methods being used should complement each other. The present paper describes the methods and main results of the vibration noise studies of internals and the fuel assemblies of the operating NPPs with WWER reactors, as an example of the implementation of the comprehensive approach to the analysis on equipment flow-induced vibration. At that, the characteristics of internals and fuel assemblies vibration loading were dealt jointly as they are elements of the same compound oscillating system and their vibrations have the interrelated nature
Vibration isolation of a ship's seat
Agahi, Maryam; Samani, Mehrdad B.; Behzad, Mehdi
2005-05-01
Different factors cause vibration. These vibrations make the voyages difficult and reduce comfort and convenience in passenger ships. In this paper, the creating factors of vibration have discussed first, then with mathematical modelling it will be attempted to minimize the vibration over the crew's seat. The modelling consists of a system with two degrees of freedom and by using vibrationisolation with passive method of Tuned Mass Damper (TMD) it will be tried to reduce the vibration over personnel. Moreover using active control systems will be compared with passive systems.
Hand-arm vibration syndrome in South African gold miners.
Nyantumbu, Busi; Barber, Chris M; Ross, Mary; Curran, Andrew D; Fishwick, David; Dias, Belinda; Kgalamono, Spo; Phillips, James I
2007-01-01
Hand-arm vibration syndrome (HAVS) is associated with the use of hand-held vibrating tools. Affected workers may experience symptoms of tingling, numbness, loss of grip strength and pain. Loss of dexterity may impair everyday activities, and potentially increase the risk of occupational accidents. Although high vibration levels (up to 31 m/s(2)) have been measured in association with rock drills, HAVS has not been scientifically evaluated in the South African mining industry. The aim of this study was to determine the prevalence and severity of HAVS in South African gold miners, and to identify the tools responsible. A cross-sectional study was conducted in a single South African gold-mine. Participants were randomly selected from mineworkers returning from annual leave, comprising 156 subjects with occupational exposure to vibration, and 140 workers with no exposure. Miners who consented to participate underwent a clinical HAVS assessment following the UK Health and Safety Laboratory protocol. The prevalence of HAVS in vibration-exposed gold miners was 15%, with a mean latent period of 5.6 years. Among the non-exposed comparison group, 5% had signs and symptoms indistinguishable from HAVS. This difference was statistically significant (P < 0.05). All the cases of HAVS gave a history of exposure to rock drills. The study has diagnosed the first cases of HAVS in the South African mining industry. The prevalence of HAVS was lower than expected, and possible explanations for this may include a survivor population, and lack of vascular symptom reporting due to warm-ambient temperatures.
Fault diagnosis in spur gears based on genetic algorithm and random forest
Cerrada, Mariela; Zurita, Grover; Cabrera, Diego; Sánchez, René-Vinicio; Artés, Mariano; Li, Chuan
2016-03-01
There are growing demands for condition-based monitoring of gearboxes, and therefore new methods to improve the reliability, effectiveness, accuracy of the gear fault detection ought to be evaluated. Feature selection is still an important aspect in machine learning-based diagnosis in order to reach good performance of the diagnostic models. On the other hand, random forest classifiers are suitable models in industrial environments where large data-samples are not usually available for training such diagnostic models. The main aim of this research is to build up a robust system for the multi-class fault diagnosis in spur gears, by selecting the best set of condition parameters on time, frequency and time-frequency domains, which are extracted from vibration signals. The diagnostic system is performed by using genetic algorithms and a classifier based on random forest, in a supervised environment. The original set of condition parameters is reduced around 66% regarding the initial size by using genetic algorithms, and still get an acceptable classification precision over 97%. The approach is tested on real vibration signals by considering several fault classes, one of them being an incipient fault, under different running conditions of load and velocity.
Sound & Vibration 20 Design Guidelines for Health Care Facilities
Tocci, Gregory; Cavanaugh, William
2013-01-01
Sound, vibration, noise and privacy have significant impacts on health and performance. As a result, they are recognized as essential components of effective health care environments. However, acoustics has only recently become a prominent consideration in the design, construction, and operation of healthcare facilities owing to the absence, prior to 2010, of clear and objective guidance based on research and best practices. Sound & Vibration 2.0 is the first publication to comprehensively address this need. Sound & Vibration 2.0 is the sole reference standard for acoustics in health care facilities and is recognized by: the 2010 FGI Guidelines for the Design and Construction of Health Care Facilities (used in 60 countries); the US Green Building Council’s LEED for Health Care (used in 87 countries); The Green Guide for Health Care V2.2; and the International Code Council (2011). Sound & Vibration 2.0 was commissioned by the Facility Guidelines Institute in 2005, written by the Health Care Acous...
Autonomous target recognition using remotely sensed surface vibration measurements
Geurts, James; Ruck, Dennis W.; Rogers, Steven K.; Oxley, Mark E.; Barr, Dallas N.
1993-09-01
The remotely measured surface vibration signatures of tactical military ground vehicles are investigated for use in target classification and identification friend or foe (IFF) systems. The use of remote surface vibration sensing by a laser radar reduces the effects of partial occlusion, concealment, and camouflage experienced by automatic target recognition systems using traditional imagery in a tactical battlefield environment. Linear Predictive Coding (LPC) efficiently represents the vibration signatures and nearest neighbor classifiers exploit the LPC feature set using a variety of distortion metrics. Nearest neighbor classifiers achieve an 88 percent classification rate in an eight class problem, representing a classification performance increase of thirty percent from previous efforts. A novel confidence figure of merit is implemented to attain a 100 percent classification rate with less than 60 percent rejection. The high classification rates are achieved on a target set which would pose significant problems to traditional image-based recognition systems. The targets are presented to the sensor in a variety of aspects and engine speeds at a range of 1 kilometer. The classification rates achieved demonstrate the benefits of using remote vibration measurement in a ground IFF system. The signature modeling and classification system can also be used to identify rotary and fixed-wing targets.
Stochastic many-body perturbation theory for anharmonic molecular vibrations
Energy Technology Data Exchange (ETDEWEB)
Hermes, Matthew R. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)
2014-08-28
A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value of a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm{sup −1} and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.
Control of pipe vibrations; Schwingungsminderung bei Rohrleitungen
Energy Technology Data Exchange (ETDEWEB)
Sinambari, G.R. [FH Bingen, Fachrichtung Umweltschutz, und IBS Ingenieurbuero fuer Schall- und Schwingungstechnik GmbH, Frankenthal (Germany); Thorn, U. [IBS Ingenieurbuero fuer Schall- und Schwingungstechnik GmbH, Frankenthal (Germany)
2005-06-01
Following commissioning of a new vacuum system for the refinery of MiRO Mineraloelraffinerie Oberrhein GmbH and Co. KG, vibrations occurred in the furnace exhaust pipes. As these had to be regarded as critical for the fatigue strength of the pipes, the pipes' vibration response in the critical frequency range was investigated immediately by means of a vibration analysis, and appropriate measures for vibration control were elaborated. All investigations, and the installation of the hydraulic vibration dampers, took place with the system operating. The effectiveness of the measures taken was checked by means of measurements following installation. The measures succeeded in attenuating the vibrations to a level at which, empirically, damage need no longer be expected. This paper illustrates the procedure for developing the vibration control measures and the essential results of the investigations. (orig.)
Vibrations on board and health effects
DEFF Research Database (Denmark)
Jensen, Anker; Jepsen, Jørgen Riis
2014-01-01
There is only limited knowledge of the exposure to vibrations of ships’ crews and their risk of vibration-induced health effects. Exposure to hand-arm vibrations from the use of vibrating tools at sea does not differ from that in the land-based trades. However, in contrast to most other work places...... of the health consequences of whole body vibrations in land-transportation, such exposure at sea may affect ships’ passengers and crews. While the relation of back disorders to high levels of whole body vibration has been demonstrated among e.g. tractor drivers, there are no reported epidemiological evidence...... for such relation among seafarers except for fishermen, who, however, are also exposed to additional recognised physical risk factors at work. The assessment and reduction of vibrations by naval architects relates to technical implications of this impact for the ships’ construction, but has limited value...
Interfacial instabilities in vibrated fluids
Porter, Jeff; Laverón-Simavilla, Ana; Tinao Perez-Miravete, Ignacio; Fernandez Fraile, Jose Javier
2016-07-01
Vibrations induce a range of different interfacial phenomena in fluid systems depending on the frequency and orientation of the forcing. With gravity, (large) interfaces are approximately flat and there is a qualitative difference between vertical and horizontal forcing. Sufficient vertical forcing produces subharmonic standing waves (Faraday waves) that extend over the whole interface. Horizontal forcing can excite both localized and extended interfacial phenomena. The vibrating solid boundaries act as wavemakers to excite traveling waves (or sloshing modes at low frequencies) but they also drive evanescent bulk modes whose oscillatory pressure gradient can parametrically excite subharmonic surface waves like cross-waves. Depending on the magnitude of the damping and the aspect ratio of the container, these locally generated surfaces waves may interact in the interior resulting in temporal modulation and other complex dynamics. In the case where the interface separates two fluids of different density in, for example, a rectangular container, the mass transfer due to vertical motion near the endwalls requires a counterflow in the interior region that can lead to a Kelvin-Helmholtz type instability and a ``frozen wave" pattern. In microgravity, the dominance of surface forces favors non-flat equilibrium configurations and the distinction between vertical and horizontal applied forcing can be lost. Hysteresis and multiplicity of solutions are more common, especially in non-wetting systems where disconnected (partial) volumes of fluid can be established. Furthermore, the vibrational field contributes a dynamic pressure term that competes with surface tension to select the (time averaged) shape of the surface. These new (quasi-static) surface configurations, known as vibroequilibria, can differ substantially from the hydrostatic state. There is a tendency for the interface to orient perpendicular to the vibrational axis and, in some cases, a bulge or cavity is induced
Directory of Open Access Journals (Sweden)
M.M. Rahman
2011-12-01
Full Text Available Trains and cars are the most important modes of transportation throughout the world. In highly developed countries, trains have become essential for human use as the most well-known form of public transportation, whereas the car plays a significant role in prompt human travel from one place to another. The high magnitude of vibration caused by trains and cars may cause health problems in humans, especially low back pain. The aim of this study was to evaluate and validate the values of daily exposure to vibration A(8 and the vibration dose value (VDV in passengers travelling by train and car and to assess the effects produced by this exposure on the human body. Moreover, this study introduces a newly developed whole-body vibration measurement instrumentation system. One train travelling from the east coast to the south of Malaysia was chosen to conduct the study. Whole-body vibration exposure was measured over 8 hours, which is equal to the duration of normal occupational exposure. One car was chosen randomly and whole-body vibration exposure was measured for 5 min and 10 min. All the data were computed using an IEPE(ICPTM accelerometer sensor connected to a DT9837 device which is capable of effectively measuring and analysing vibration. The vibration results were displayed on a personal computer using a custom graphical user interface (GUI. Matlab software was used to interpret the data. From the results, the whole-body vibration exposure level could be determined. It can be concluded that the whole-body vibration absorbed by the human body is enhanced when the magnitude of the vibration exposure experienced by the passengers increased. This was shown by the increased values of daily exposure to vibration A(8 and VDV calculated in the study.
Ergonomic Evaluation of Vibrations of a Rototiller with New Blade
Directory of Open Access Journals (Sweden)
H Gholami
2017-10-01
Full Text Available Introduction One of the most important problems arising with operation of the conventional rototillers is severe vibration of the machine handle which is transmitted to the user’s hands, arms and shoulders. Long period exposure of the hand-transmitted vibration may cause various diseases such as white finger syndrome. Therefore in this study, vibrations of a new type of rototiller with ridged blades were investigated at the position of handle/hand interface in different working conditions. Finally, the maximum allowable exposure time to the rototiller users in continuous tillage operation was obtained according to ISO 5349-1. Materials and Methods Experiments were carried out in one of the farms with silty clay soil texture, located in Sari city, Mazandaran province, Iran. Vibration measurements were performed according to ISO 5349-1 and ISO 5349-2 standards in two different modes, including in situ mode and tillage mode. Vibrational parameters were obtained in three blade rotational speeds, i.e., low speed (140-170 rpm, medium speed (170-200, and high speed (200-230. Blade rotational speed varied by changing engine speed using the throttle control lever. In each experiment, different vibrational values were individually recorded in three directions (x, y, and z. Experimental design and data analysis were performed in a Randomized Complete Block Design with three replications using the SPSS16 software. Results and Discussion Based on the obtained results in this study, the RMS of acceleration increased by increasing in rotational speed for all of the conducted experiments. The reason is that number of cutting per unit of time and consequently the frequency of changing in the dynamic forces exerting on the blades dramatically increases with increasing the rotational speed of the blades. Noteworthy is that in most cases the variation of acceleration in the tillage mode showed similar trend with vibrational values in the idling mode. This
Attitudes Toward, and Use of, Vibrators in China.
Jing, Shen; Lay, Alixe; Weis, Laura; Furnham, Adrian
2018-01-02
The current study examined the relationship between traditional masculine traits and attitudes toward vibrator use, actual vibrator use, and frequency of vibrator use in China. In all, 235 Chinese females aged between 16 and 58 years completed a questionnaire regarding attitudes toward, and personal use of, vibrators. The results showed a positive association between masculine traits and attitudes toward women's vibrator use, attitudes toward vibrator use and actual vibrator use, as well as frequency of vibrator use. The findings revealed an indirect path in which masculinity influences actual and frequency of vibrator use through attitudes toward women's vibrator use. Limitations and implications of the study are discussed.
Coffeng, Jennifer K; Boot, Cécile R L; Duijts, Saskia F A; Twisk, Jos W R; van Mechelen, Willem; Hendriksen, Ingrid J M
2014-01-01
To investigate the effectiveness of a worksite social and physical environment intervention on need for recovery (i.e., early symptoms of work-related mental and physical fatigue), physical activity and relaxation. Also, the effectiveness of the separate interventions was investigated. In this 2 × 2 factorial design study, 412 office employees from a financial service provider participated. Participants were allocated to the combined social and physical intervention, to the social intervention only, to the physical intervention only or to the control group. The primary outcome measure was need for recovery. Secondary outcomes were work-related stress (i.e., exhaustion, detachment and relaxation), small breaks, physical activity (i.e., stair climbing, active commuting, sport activities, light/moderate/vigorous physical activity) and sedentary behavior. Outcomes were measured by questionnaires at baseline, 6 and 12 months follow-up. Multilevel analyses were performed to investigate the effects of the three interventions. In all intervention groups, a non-significant reduction was found in need for recovery. In the combined intervention (n = 92), exhaustion and vigorous physical activities decreased significantly, and small breaks at work and active commuting increased significantly compared to the control group. The social intervention (n = 118) showed a significant reduction in exhaustion, sedentary behavior at work and a significant increase in small breaks at work and leisure activities. In the physical intervention (n = 96), stair climbing at work and active commuting significantly increased, and sedentary behavior at work decreased significantly compared to the control group. None of the interventions was effective in improving the need for recovery. It is recommended to implement the social and physical intervention among a population with higher baseline values of need for recovery. Furthermore, the intervention itself could be improved by increasing the
Directory of Open Access Journals (Sweden)
Jennifer K Coffeng
Full Text Available To investigate the effectiveness of a worksite social and physical environment intervention on need for recovery (i.e., early symptoms of work-related mental and physical fatigue, physical activity and relaxation. Also, the effectiveness of the separate interventions was investigated.In this 2 × 2 factorial design study, 412 office employees from a financial service provider participated. Participants were allocated to the combined social and physical intervention, to the social intervention only, to the physical intervention only or to the control group. The primary outcome measure was need for recovery. Secondary outcomes were work-related stress (i.e., exhaustion, detachment and relaxation, small breaks, physical activity (i.e., stair climbing, active commuting, sport activities, light/moderate/vigorous physical activity and sedentary behavior. Outcomes were measured by questionnaires at baseline, 6 and 12 months follow-up. Multilevel analyses were performed to investigate the effects of the three interventions.In all intervention groups, a non-significant reduction was found in need for recovery. In the combined intervention (n = 92, exhaustion and vigorous physical activities decreased significantly, and small breaks at work and active commuting increased significantly compared to the control group. The social intervention (n = 118 showed a significant reduction in exhaustion, sedentary behavior at work and a significant increase in small breaks at work and leisure activities. In the physical intervention (n = 96, stair climbing at work and active commuting significantly increased, and sedentary behavior at work decreased significantly compared to the control group.None of the interventions was effective in improving the need for recovery. It is recommended to implement the social and physical intervention among a population with higher baseline values of need for recovery. Furthermore, the intervention itself could be improved by
Dynamical response of vibrating ferromagnets
Gaganidze, E; Ziese, M
2000-01-01
The resonance frequency of vibrating ferromagnetic reeds in a homogeneous magnetic field can be substantially modified by intrinsic and extrinsic field-related contributions. Searching for the physical reasons of the field-induced resonance frequency change and to study the influence of the spin glass state on it, we have measured the low-temperature magnetoelastic behavior and the dynamical response of vibrating amorphous and polycrystalline ferromagnetic ribbons. We show that the magnetoelastic properties depend strongly on the direction of the applied magnetic field. The influence of the re-entrant spin glass transition on these properties is discussed. We present clear experimental evidence that for applied fields perpendicular to the main area of the samples the behavior of ferromagnetic reeds is rather independent of the material composition and magnetic state, exhibiting a large decrease of the resonance frequency. This effect can be very well explained with a model based on the dynamical response of t...
Vibration of imperfect rotating disk
Directory of Open Access Journals (Sweden)
Půst L.
2011-12-01
Full Text Available This study is concerned with the theoretical and numerical calculations of the flexural vibrations of a bladed disk. The main focus of this study is to elaborate the basic background for diagnostic and identification methods for ascertaining the main properties of the real structure or an experimental model of turbine disks. The reduction of undesirable vibrations of blades is proposed by using damping heads, which on the experimental model of turbine disk are applied only on a limited number of blades. This partial setting of damping heads introduces imperfection in mass, stiffness and damping distribution on the periphery and leads to more complicated dynamic properties than those of a perfect disk. Calculation of FEM model and analytic—numerical solution of disk behaviour in the limited (two modes frequency range shows the splitting of resonance with an increasing speed of disk rotation. The spectrum of resonance is twice denser than that of a perfect disk.
Tool-specific performance of vibration-reducing gloves for attenuating fingers-transmitted vibration
Welcome, Daniel E.; Dong, Ren G.; Xu, Xueyan S.; Warren, Christopher; McDowell, Thomas W.
2016-01-01
BACKGROUND Fingers-transmitted vibration can cause vibration-induced white finger. The effectiveness of vibration-reducing (VR) gloves for reducing hand transmitted vibration to the fingers has not been sufficiently examined. OBJECTIVE The objective of this study is to examine tool-specific performance of VR gloves for reducing finger-transmitted vibrations in three orthogonal directions (3D) from powered hand tools. METHODS A transfer function method was used to estimate the tool-specific effectiveness of four typical VR gloves. The transfer functions of the VR glove fingers in three directions were either measured in this study or during a previous study using a 3D laser vibrometer. More than seventy vibration spectra of various tools or machines were used in the estimations. RESULTS When assessed based on frequency-weighted acceleration, the gloves provided little vibration reduction. In some cases, the gloves amplified the vibration by more than 10%, especially the neoprene glove. However, the neoprene glove did the best when the assessment was based on unweighted acceleration. The neoprene glove was able to reduce the vibration by 10% or more of the unweighted vibration for 27 out of the 79 tools. If the dominant vibration of a tool handle or workpiece was in the shear direction relative to the fingers, as observed in the operation of needle scalers, hammer chisels, and bucking bars, the gloves did not reduce the vibration but increased it. CONCLUSIONS This study confirmed that the effectiveness for reducing vibration varied with the gloves and the vibration reduction of each glove depended on tool, vibration direction to the fingers, and finger location. VR gloves, including certified anti-vibration gloves do not provide much vibration reduction when judged based on frequency-weighted acceleration. However, some of the VR gloves can provide more than 10% reduction of the unweighted vibration for some tools or workpieces. Tools and gloves can be matched for
Surveillance of vibrations in PWR
International Nuclear Information System (INIS)
Espefaelt, R.; Lorenzen, J.; Aakerhielm, F.
1980-07-01
The core of a PWR - including fuel elements, internal structure, control rods and core support structure inside the pressure vessel - is subjected to forces which can cause vibrations. One sensitive means to detect and analyse such vibrations is by means of the noise from incore and excore neutron detector signals. In this project noise recordings have been made on two occasions in the Ringhals 2 plant and the obtained data been analysed using the Studsvik Noise Analysis Program System (SNAPS). The results have been intepreted and a detailed description of the vibrational status of the core and pressure vessel internals has been produced. On the basis of the obtained results it is proposed that neutron signal noise analysis should be performed at each PWR plant in the beginning, middle and end of each fuel cycle and an analysis be made using the methods developed in the project. It would also provide a contribution to a higher degree of preparedness for diagnostic tasks in case of unexpected and abnormal events. (author)
Coffeng, Jennifer K.; Boot, Cécile R. L.; Duijts, Saskia F. A.; Twisk, Jos W. R.; van Mechelen, Willem; Hendriksen, Ingrid J. M.
2014-01-01
Objective To investigate the effectiveness of a worksite social and physical environment intervention on need for recovery (i.e., early symptoms of work-related mental and physical fatigue), physical activity and relaxation. Also, the effectiveness of the separate interventions was investigated. Methods In this 2×2 factorial design study, 412 office employees from a financial service provider participated. Participants were allocated to the combined social and physical intervention, to the social intervention only, to the physical intervention only or to the control group. The primary outcome measure was need for recovery. Secondary outcomes were work-related stress (i.e., exhaustion, detachment and relaxation), small breaks, physical activity (i.e., stair climbing, active commuting, sport activities, light/moderate/vigorous physical activity) and sedentary behavior. Outcomes were measured by questionnaires at baseline, 6 and 12 months follow-up. Multilevel analyses were performed to investigate the effects of the three interventions. Results In all intervention groups, a non-significant reduction was found in need for recovery. In the combined intervention (n = 92), exhaustion and vigorous physical activities decreased significantly, and small breaks at work and active commuting increased significantly compared to the control group. The social intervention (n = 118) showed a significant reduction in exhaustion, sedentary behavior at work and a significant increase in small breaks at work and leisure activities. In the physical intervention (n = 96), stair climbing at work and active commuting significantly increased, and sedentary behavior at work decreased significantly compared to the control group. Conclusion None of the interventions was effective in improving the need for recovery. It is recommended to implement the social and physical intervention among a population with higher baseline values of need for recovery. Furthermore, the intervention
Mechanism of laser and rf plasma in vibrational nonequilibrium CO-N2 gas mixture
International Nuclear Information System (INIS)
Lou Guofeng; Adamovich, Igor V.
2009-01-01
This paper investigates the mechanism of plasma created by focused CO laser and rf electric field. The plasma is created in a CO/N 2 environment, at a total pressure of 600 torr. Ionization of the gases occurs by an associative ionization mechanism, in collisions of two highly vibrationally excited molecules. These highly vibrationally excited states are populated by resonance absorption of the CO radiation followed by anharmonic vibration-vibration (V-V) pumping. Moreover N 2 also becomes vibrationally excited due to collisions with vibrationally excited CO. The coupled rf reduced electric field E/N is sufficiently low to prevent electron impact ionization that may create plasma individually, so when a subbreakdown rf field is applied to the plasma, collisions between the free electrons heated by the field and the diatomic species create additional vibrational excitation both in the region occupied by the CO laser beam and outside of the laser beam region. The numerical results show plasma created in both regions (in and out of the CO laser beam region) with the associative ionization mechanism. This suggests a method for creating a stable nonequilibrium plasma. The calculation result is verified by comparison the synthetic spectrum to a measured one.
Juhász, Imre Benedek; Csurgay, Árpád I.
2018-04-01
In recent years, the role of molecular vibrations in exciton energy transfer taking place during the first stage of photosynthesis attracted increasing interest. Here, we present a model formulated as a Lindblad-type master equation that enables us to investigate the impact of undamped and especially damped intramolecular vibrational modes on the exciton energy transfer, particularly its efficiency. Our simulations confirm the already reported effects that the presence of an intramolecular vibrational mode can compensate the energy detuning of electronic states, thus promoting the energy transfer; and, moreover, that the damping of such a vibrational mode (in other words, vibrational relaxation) can further enhance the efficiency of the process by generating directionality in the energy flow. As a novel result, we show that this enhancement surpasses the one caused by pure dephasing, and we present its dependence on various system parameters (time constants of the environment-induced relaxation and excitation processes, detuning of the electronic energy levels, frequency of the intramolecular vibrational modes, Huang-Rhys factors, temperature) in dimer model systems. We demonstrate that vibrational-relaxation-enhanced exciton energy transfer (VREEET) is robust against the change of these characteristics of the system and occurs in wide ranges of the investigated parameters. With simulations performed on a heptamer model inspired by the Fenna-Matthews-Olson (FMO) complex, we show that this mechanism can be even more significant in larger systems at T = 300 K. Our results suggests that VREEET might be prevalent in light-harvesting complexes.
Attitudes Toward, and Use of, Vibrators in China
Jing, S.; Lay, A.; Weis, L.; Furnham, A.
2018-01-01
The current study examined the relationship between traditional masculine traits and attitudes toward vibrator use, actual vibrator use, and frequency of vibrator use in China. In all, 235 Chinese females aged between 16 and 58 years completed a questionnaire regarding attitudes toward, and personal use of, vibrators. The results showed a positive association between masculine traits and attitudes toward women's vibrator use, attitudes toward vibrator use and actual vibrator use, as well as f...
Adaptive Piezoelectric Absorber for Active Vibration Control
Directory of Open Access Journals (Sweden)
Sven Herold
2016-02-01
Full Text Available Passive vibration control solutions are often limited to working reliably at one design point. Especially applied to lightweight structures, which tend to have unwanted vibration, active vibration control approaches can outperform passive solutions. To generate dynamic forces in a narrow frequency band, passive single-degree-of-freedom oscillators are frequently used as vibration absorbers and neutralizers. In order to respond to changes in system properties and/or the frequency of excitation forces, in this work, adaptive vibration compensation by a tunable piezoelectric vibration absorber is investigated. A special design containing piezoelectric stack actuators is used to cover a large tuning range for the natural frequency of the adaptive vibration absorber, while also the utilization as an active dynamic inertial mass actuator for active control concepts is possible, which can help to implement a broadband vibration control system. An analytical model is set up to derive general design rules for the system. An absorber prototype is set up and validated experimentally for both use cases of an adaptive vibration absorber and inertial mass actuator. Finally, the adaptive vibration control system is installed and tested with a basic truss structure in the laboratory, using both the possibility to adjust the properties of the absorber and active control.
Ground test for vibration control demonstrator
Meyer, C.; Prodigue, J.; Broux, G.; Cantinaud, O.; Poussot-Vassal, C.
2016-09-01
In the objective of maximizing comfort in Falcon jets, Dassault Aviation is developing an innovative vibration control technology. Vibrations of the structure are measured at several locations and sent to a dedicated high performance vibration control computer. Control laws are implemented in this computer to analyse the vibrations in real time, and then elaborate orders sent to the existing control surfaces to counteract vibrations. After detailing the technology principles, this paper focuses on the vibration control ground demonstration that was performed by Dassault Aviation in May 2015 on Falcon 7X business jet. The goal of this test was to attenuate vibrations resulting from fixed forced excitation delivered by shakers. The ground test demonstrated the capability to implement an efficient closed-loop vibration control with a significant vibration level reduction and validated the vibration control law design methodology. This successful ground test was a prerequisite before the flight test demonstration that is now being prepared. This study has been partly supported by the JTI CleanSky SFWA-ITD.
Head and Helmet Biodynamics and Tracking Performance in Vibration Environments
National Research Council Canada - National Science Library
Smith, Suzanne D; Smith, Jeanne A
2006-01-01
...) and Up (40" elevation, 0" azimuth)], and three helmet CCs were tested. The overall head, helmet, and helmet slippage displacement rotations, and rms tracking error and percent time-on-target were evaluated...
Investigation and analysis the vibration of handles of chainsaw without cutting
Directory of Open Access Journals (Sweden)
M Feyzi
2016-04-01
(VMI-192. The accelerometer mounted on an adapter inserted between the handle and accelerometer. The experiments were conducted in split plot completely randomized design. Ninety tests in two handles, three speeds of engine, three perpendicular axes and five repeats were conducted. The vibration acceleration at various conditions was measured and the root mean square of vibration acceleration was calculated based on acceleration-time spectrum. To investigate the characteristics of vibration in different speeds, the vibration spectrums in time domain were converted to spectrums in frequency domain. The frequency weighted RMS acceleration at 1/3rd octave bands from 6.3Hz to 1250Hz and the vibration total value was calculated from frequency spectrum. To analyze the obtained data, SAS software was used. Furthermore, the Duncan's multiple range tests were used to compare the RMS values. Results and Discussion: Main source of vibration of chainsaw was single cylinder engine. The acceleration spectra of employed chainsaw had peaks in frequencies in accordance with the speed of engine. These peaks in 2800 rpm, 10000 rpm and 13300 rpm speeds of engine occurred in 46.5Hz, 166.5Hz and 221.5Hz, respectively. To achieve a safe design for handle of portable tools, identifying the frequency which leads to the maximum value of vibration acceleration is very useful. To avoid the resonance phenomenon, the natural frequency of handle must be far from dominant frequency of engine. The results of ANOVA showed that the RMS acceleration in different axes and different speeds were significant at 1% level. The maximum value of vibration acceleration, at idling engine speed, occurred in the lateral axis. In addition, the mentioned variable was maximized in normal and axial axes at nominal and racing speeds, respectively. The total value of vibration was increased when the speed of engine moving away from nominal speed. This increase in rear handle is very larger than front handle. The total
Damping of monopole vibrations in time dependent Hartree-Fock theory
International Nuclear Information System (INIS)
Vautherin, D.; Stringari, S.
1979-01-01
Monopole vibrations in oxygen-16 and calcium-40 have been investigated in time-dependent Hartree-Fock theory. The characteristic damping time obtained is tau approximately 1.5x10 -22 sec. This value is in good agreement with the width of the monopole mode calculated in the random phase approximation
Van Dyke, Michael B.
2013-01-01
Present preliminary work using lumped parameter models to approximate dynamic response of electronic units to random vibration; Derive a general N-DOF model for application to electronic units; Illustrate parametric influence of model parameters; Implication of coupled dynamics for unit/board design; Demonstrate use of model to infer printed wiring board (PWB) dynamics from external chassis test measurement.
1975-06-01
CONTROL TECHNIQUES FOR DIGITAL CONTROL OF RANDOM VOIRATION TESTS J. D. Tebba and D. 0. Smallwood , Sandia Laboratories, Albuquerque. New Mexico VIBRATION...for dynamic end quasi-static loading conditions. (14] Norman . Jaons, T. 0. Uran and S. A. Tekin. SM1210=1 "The Dynamic riastic Behavior of Fully
Vibration-type particle separation device with piezoceramic vibrator
Ooe, Katsutoshi; Doi, Akihiro
2008-12-01
During hemanalysis, it is necessary to separate blood cells from whole blood. Many blood separation methods, for example, centrifugation and filtering, are in practical use. However, the use of these methods involves problems from the perspectives of processing speed and processing volume. We develop new types of blood separation devices that use piezo-ceramic vibrators. The first device uses a capillary. One end of the capillary is fixed to the device frame, and the other is fixed to a piezo-ceramic vibrator. The vibrator transmits bending waves to the capillary. This device can process only a small amount of solution; therefore, it is not suitable for hemanalysis. In order to solve this problem, we developed a second device; this device has a pair of thin glass plates with a small gap as a substitute for the capillary used in the first device. These devices are based on the fact that particles heavier than water move toward transverse velocity antinodes while those lighter than water move toward velocity nodes. In this report, we demonstrate the highspeed separation of silica microbeads and 50-vol% glycerol water by using these devices. The first device can separate the abovementioned solution within 3 min while the second can separate it within 1 min. Both devices are driven by a rectangular wave of 15 to 20 Vpp. Furthermore, it has been confirmed that red blood cells are separated from diluted whole blood using the first device within approximately 1 min. These devices have transparency, so they can compose as the analysis system with the chemical analyzer easily.
High-Power Piezoelectric Vibration Characteristics of Textured SrBi2Nb2O9 Ceramics
Kawada, Shinichiro; Ogawa, Hirozumi; Kimura, Masahiko; Shiratsuyu, Kosuke; Niimi, Hideaki
2006-09-01
The high-power piezoelectric vibration characteristics of textured SrBi2Nb2O9 (SBN) ceramics, that is bismuth-layer-structured ferroelectrics, were studied in the longitudinal mode (33-mode) by constant current driving method and compared with those of ordinary randomly oriented SBN and widely used Pb(Ti,Zr)O3 (PZT) ceramics. In the case of textured SBN ceramics, resonant properties are stable up to a vibration velocity of 2.6 m/s. Vibration velocity at resonant frequency increases proportionally with the applied electric field, and resonant frequency is almost constant in high-vibration-velocity driving. On the other hand, in the case of randomly oriented SBN and PZT ceramics, the increase in vibration velocity is not proportional to the applied high electric field, and resonant frequency decreases with increasing vibration velocity. The resonant sharpness Q of textured SBN ceramics is about 2000, even at a vibration velocity of 2.6 m/s. Therefore, textured SBN ceramics are good candidates for high-power piezoelectric applications.
Vibration isolation and damping in high precision equipment
Bukkems, B.; Ruijl, T.; Simons, J.
2017-06-01
All systems located in a laboratory environment or factory are subject to disturbances. These disturbances can either come from the surroundings, e.g. floor-induced vibrations, or from the system itself, e.g. stage-induced vibrations. In many cases it is needed to minimize the effect of these disturbances. This can either be done by isolating the system from its disturbance source or by applying damping to the system. In this paper we present various cases in which we have effectively reduced the impact of disturbances on the system's performance, either by improving its isolation system, by minimizing the impact of stage reaction forces, or by designing polymer damping into the system.
Influence of noise and vibration upon creatine kinase activity in blood serum
Energy Technology Data Exchange (ETDEWEB)
Jonderko, G; Gabryel, A; Jonderko, K; Konca, A; Marcisz, C; Olak, Z; Szramek-Urbaniak, A
1982-02-01
The investigations comprised part of the workers employed in a factory of prefabricated concrete elements. The creatine kinase (CK) activity was determined before and after a day's work in the following groups of workers: I - exposed to noise and vibration exceeding the allowed norm, II - exposed to noise, performing the same hard physical work as group I and exposed to vibration not exceeding 79 dB in particular octave bands, III - practising physical work as group I and II but in environment free from noise and vibration, and a control group of persons not exposed to any of the tested factors. The obtained results indicate that the determination of the CK activity may serve as a test of exposure to vibration and noise.
Fang, Yuanyuan; Zuo, Yanyan; Xia, Zhaowang
2018-03-01
The noise level is getting higher with the development of high-power marine power plant. Mechanical noise is one of the most obvious noise sources which not only affect equipment reliability, riding comfort and working environment, but also enlarge underwater noise. The periodic truss type device which is commonly applied in fields of aerospace and architectural is introduced to floating raft construction in ship. Four different raft frame structure are designed in the paper. The vibration transmissibility is taken as an evaluation index to measure vibration isolation effect. A design scheme with the best vibration isolation effect is found by numerical method. Plate type and the optimized periodic truss type raft frame structure are processed to experimental verify vibration isolation effect of the structure of the periodic raft. The experimental results demonstrate that the same quality of the periodic truss floating raft has better isolation effect than that of the plate type floating raft.
Identification of Bearing Failure Using Signal Vibrations
Yani, Irsyadi; Resti, Yulia; Burlian, Firmansyah
2018-04-01
Vibration analysis can be used to identify damage to mechanical systems such as journal bearings. Identification of failure can be done by observing the resulting vibration spectrum by measuring the vibration signal occurring in a mechanical system Bearing is one of the engine elements commonly used in mechanical systems. The main purpose of this research is to monitor the bearing condition and to identify bearing failure on a mechanical system by observing the resulting vibration. Data collection techniques based on recordings of sound caused by the vibration of the mechanical system were used in this study, then created a database system based bearing failure due to vibration signal recording sounds on a mechanical system The next step is to group the bearing damage by type based on the databases obtained. The results show the percentage of success in identifying bearing damage is 98 %.
Unjamming a granular hopper by vibration
Janda, A.; Maza, D.; Garcimartín, A.; Kolb, E.; Lanuza, J.; Clément, E.
2009-07-01
We present an experimental study of the outflow of a hopper continuously vibrated by a piezoelectric device. Outpouring of grains can be achieved for apertures much below the usual jamming limit observed for non-vibrated hoppers. Granular flow persists down to the physical limit of one grain diameter, a limit reached for a finite vibration amplitude. For the smaller orifices, we observe an intermittent regime characterized by alternated periods of flow and blockage. Vibrations do not significantly modify the flow rates both in the continuous and the intermittent regime. The analysis of the statistical features of the flowing regime shows that the flow time significantly increases with the vibration amplitude. However, at low vibration amplitude and small orifice sizes, the jamming time distribution displays an anomalous statistics.
Cleaning device for vibrational hose filter
Energy Technology Data Exchange (ETDEWEB)
Engels, R
1978-01-05
Filter hoses out of web in dust separators can be cleaned by enforced vibrations. The efficiency of the cleaning is a maximum if the vibrations are at about the individual frequency of the whole arrangement. In the interior of the hose a cage from bars parallel to the wall of the hose is placed on its total length. The bars are fixed at one end and connected with a vibration exciter at the other end. The unilaterally fixed vibration bars can be adjusted to the individual frequency of the vibration exciter. If the hose filter is flown through from the outer to the inner side the vibration bars serve as a supporting body. In the reverse case the bars are placed on the outer side of the hose filter.
The Dictionary On Environment and Pollution
International Nuclear Information System (INIS)
1989-01-01
This book is the dictionary for environment and pollution, which puts the words in alphabetical order. It includes words such as street refuse, powdered soap, sodium hydroxide, waste caustics, causticization, vibration acceleration level, gasoline, and processed fuel. This dictionary gives descriptions on each word which is related the environment and pollution.
Research In Diagnosing Bearing Defects From Vibrations
Zoladz, T.; Earhart, E.; Fiorucci, T.
1995-01-01
Report describes research in bearing-defect signature analysis - use of vibration-signal analysis to diagnose defects in roller and ball bearings. Experiments performed on bearings in good condition and other bearings in which various parts scratched to provide known defects correlated with vibration signals. Experiments performed on highly instrumented motor-driven rotor assembly at speeds up to 10,050 r/min, using accelerometers, velocity probes, and proximity sensors mounted at various locations on assembly to measure vibrations.
Probabilistic structural damage identification based on vibration data
International Nuclear Information System (INIS)
Hao, H.; Xia, Y.
2001-01-01
Vibration-based methods are being rapidly developed and applied to detect structural damage in civil, mechanical and aerospace engineering communities in the last two decades. But uncertainties existing in the structural model and measured vibration data might lead to unreliable results. This paper will present some recent research results to tackle the above mentioned uncertainty problems. By assuming each of the FE model parameters and measured vibration data as a normally distributed random variable, a probabilistic damage detection procedure is developed based on perturbation method and validated by Monte Carlo simulation technique. With this technique, the damage probability of each structural element can be determined. The method developed has been verified by applying it to identify the damages of laboratory tested structures. It was proven that, as compared to the deterministic damage identification method, the present method can not only reduce the possibility of false identification, but also give the identification results in terms of probability. which is deemed more realistic and practical in detecting possible damages in a structure. It has also been found that the modal data included in damage identification analysis have a great influence on the identification results. With a sensitivity study, an optimal measurement set for damage detection is determined. This set includes the optimal measurement locations and the most appropriate modes that should be used in the damage identification analysis. Numerical results indicated that if the optimal set determined in a pre-analysis is used in the damage detection better results will be achieved. (author)
Flow induced vibrational excitation of nuclear reactor structures
International Nuclear Information System (INIS)
Gibert, R.J.
1979-01-01
The pressure fluctuations generated by disturbed flows, encountered in nuclear reactors induce vibrations in the structures. In order to make forecastings for these vibrational levels, it is necessary to know the characteristics of the random pressure fluctuations induced in the walls by the main flow peculiarities of the circuits. This knowledge is essentially provided by experimentation which shows that most of the energy from these fluctuations is in the low frequency area. It is also necessary to determine the transfer functions of the fluid-structure coupled system. Given the frequency range of the excitations, a calculation of the characteristics of the first eigenmodes is generally sufficient. This calculation is carried out by finite element codes, the modal dampings being assessed separately. In this paper, emphasis is placed mainly on the analysis of the sources of excitation due to flow peculiarities. Some examples will also be given of assessments of vibrations in real structures (pipes, reactor internals, etc.) and of comparisons with the experimental results obtained on models or on a site [fr
Quasiparticles and Nuclear Vibrational States; Kvazichastitsy i vibratsionnye sostoyaniya yader
Energy Technology Data Exchange (ETDEWEB)
Sorensen, R. A. [Carnegie-Mellon University, Pittsburgh, PA (United States)
1968-12-15
The level structure associated with various nuclear vibrations is described. It is shown how these vibrations are described in terms of particle or quasi - particle excitations by means of the harmonic random phase approximation. Vibrations corresponding to different modes of excitation are compared. Motions corresponding to the enhancement of three different simple operators are considered: (a) the E2 one-body operator, (b) the operator causing the removal or addition of a like, zero-coupled pair of nucleons from the nucleus, and (c) the operator for allowed beta decay which changes one proton to a neutron or one neutron to a proton. (author) [Russian] Da etsja opisanie str u ktu ry urovnej, svjazannyh s razlichnymi jadernymi kolebanijami. Pokazano, kak takie vibracii mogut byt' opisany s pomoshh'ju chastichnyh i kvazichastichnyh vozbuzhdenij v garmonicheskom priblizhenii metoda sluchajnyhfaz. Sravnivajutsja kolebanija, sootvetstvujushhie razlichnym tipam vozbuzhdenij. R assm atrivaju tsja dvizhenija, sootvetstvujushhie uvelicheniju trehraz lichnyh prostyh operatorov: a) odnochastichnyj operator E2-perehoda, v) operator pogloshhenija ili porozhdenija sparennyh nuklonov s nulevym momentom, s) operator razreshennogo /3-raspada, zamenjajushhij proton na nejtron ili nejtron na proton. (author)
Vibration-based monitoring and diagnostics using compressive sensing
Ganesan, Vaahini; Das, Tuhin; Rahnavard, Nazanin; Kauffman, Jeffrey L.
2017-04-01
Vibration data from mechanical systems carry important information that is useful for characterization and diagnosis. Standard approaches rely on continually streaming data at a fixed sampling frequency. For applications involving continuous monitoring, such as Structural Health Monitoring (SHM), such approaches result in high volume data and rely on sensors being powered for prolonged durations. Furthermore, for spatial resolution, structures are instrumented with a large array of sensors. This paper shows that both volume of data and number of sensors can be reduced significantly by applying Compressive Sensing (CS) in vibration monitoring applications. The reduction is achieved by using random sampling and capitalizing on the sparsity of vibration signals in the frequency domain. Preliminary experimental results validating CS-based frequency recovery are also provided. By exploiting the sparsity of mode shapes, CS can also enable efficient spatial reconstruction using fewer spatially distributed sensors. CS can thereby reduce the cost and power requirement of sensing as well as streamline data storage and processing in monitoring applications. In well-instrumented structures, CS can enable continued monitoring in case of sensor or computational failures.
Dynamic Characteristics of Buildings from Signal Processing of Ambient Vibration
Dobre, Daniela; Sorin Dragomir, Claudiu
2017-10-01
The experimental technique used to determine the dynamic characteristics of buildings is based on records of low intensity oscillations of the building produced by various natural factors, such as permanent agitation type microseismic motions, city traffic, wind etc. The possibility of recording these oscillations is provided by the latest seismic stations (Geosig and Kinemetrics digital accelerographs). The permanent microseismic agitation of the soil is a complex form of stationary random oscillations. The building filters the soil excitation, selects and increases the components of disruptive vibrations corresponding to its natural vibration periods. For some selected buildings, with different instrumentation schemes for the location of sensors (in free-field, at basement, ground floor, roof level), a correlation between the dynamic characteristics resulted from signal processing of ambient vibration and from a theoretical analysis will be presented. The interpretation of recording results could highlight the behavior of the whole structure. On the other hand, these results are compared with those from strong motions, or obtained from a complex dynamic analysis, and they are quite different, but they are explicable.
First international conference on vibration control in optics and metrology
International Nuclear Information System (INIS)
Baker, L.R.
1987-01-01
This book contains 27 selections. Some of the titles are: Use of optics for vibration analysis of automotive components; Use of pulsed lasers for vibration analysis in the nuclear power industry; Vibration analysis of photocopiers; Control of ground vibrations; Design of low-vibration buildings: two case histories; and Continuous pulsed electronic speckle pattern interferometry
Developed vibration waveform monitoring unit for CBM
International Nuclear Information System (INIS)
Hamada, T.; Hotsuta, K.; Hirose, I.; Morita, E.
2007-01-01
In nuclear power plants, many rotating machines such as pumps and fans are in use. Shikoku Research Institute Inc. has recently developed easy-to-use tools to facilitate the maintenance of such equipment. They include a battery-operated vibration waveform monitoring unit which allows unmanned vibration monitoring on a regular basis and data collection even from intermittently operating equipment, a waveform data collector which can be used for easy collection, storage, control, and analysis of raw vibration waveform data during normal operation, and vibration analysis and evaluation tools. A combination of these tools has a high potential for optimization of rotating equipment maintenance. (author)
Electromagnetic Vibration Energy Harvesting for Railway Applications
Directory of Open Access Journals (Sweden)
Bradai S.
2018-01-01
Full Text Available Safe localization of trains via GPS and wireless sensors is essential for railway traffic supervision. Especially for freight trains and because normally no power source is available on the wagons, special solutions for energy supply have to be developed based on energy harvesting techniques. Since vibration is available in this case, it provides an interesting source of energy. Nevertheless, in order to have an efficient design of the harvesting system, the existing vibration needs to be investigated. In this paper, we focus on the characterization of vibration parameters in railway application. We propose an electromagnetic vibration converter especially developed to this application. Vibration profiles from a train traveling between two German cities were measured using a data acquisition system installed on the train’s wagon. Results show that the measured profiles present multiple frequency signals in the range of 10 to 50 Hz and an acceleration of up to 2 g. A prototype for a vibration converter is designed taking into account the real vibration parameters, robustness and integrability requirements. It is based on a moving coil attached to a mechanical spring. For the experimental emulation of the train vibrations, a shaker is used as an external artificial vibration source controlled by a laser sensor in feedback. A maximum voltage of 1.7 V peak to peak which corresponds to a maximum of 10 mW output power where the applied excitation frequency is close to the resonant frequency of the converter which corresponds to 27 Hz.
The Efficacy of Anti-vibration Gloves
Hewitt, Sue; Dong, Ren; McDowell, Tom; Welcome, Daniel
2016-01-01
Anyone seeking to control the risks from vibration transmitted to the hands and arms may contemplate the use of anti-vibration gloves. To make an informed decision about any type of personal protective equipment, it is necessary to have performance data that allow the degree of protection to be estimated. The information provided with an anti-vibration glove may not be easy to understand without some background knowledge of how gloves are tested and does not provide any clear route for estimating likely protection. Some of the factors that influence the potential efficacy of an anti-vibration glove include how risks from hand–arm vibration exposure are assessed, how the standard test for a glove is carried out, the frequency range and direction of the vibration for which protection is sought, how much hand contact force or pressure is applied and the physical limitations due to glove material and construction. This paper reviews some of the background issues that are useful for potential purchasers of anti-vibration gloves. Ultimately, anti-vibration gloves cannot be relied on to provide sufficient and consistent protection to the wearer and before their use is contemplated all other available means of vibration control ought first to be implemented. PMID:27582615
Axisymmetric vibrations of thick shells of revolution
International Nuclear Information System (INIS)
Suzuki, Katsuyoshi; Kosawada, Tadashi; Takahashi, Shin
1983-01-01
Axisymmetric shells of revolution are used for chemical plants, nuclear power plants, aircrafts, structures and so on, and the elucidation of their free vibration is important for the design. In this study, the axisymmetric vibration of a barrel-shaped shell was analyzed by the modified thick shell theory. The Lagrangian during one period of the vibration of a shell of revolution was determined, and from its stopping condition, the vibration equations and the boundary conditions were derived. The vibration equations were analyzed strictly by using the series solution. Moreover, the basic equations for the strain of a shell and others were based on those of Love. As the examples of numerical calculation, the natural frequency and vibration mode of the symmetrical shells of revolution fixed at both ends and supported at both ends were determined, and their characteristics were clarified. By comparing the results of this study with the results by thin shell theory, the effects of shearing deformation and rotary inertia on the natural frequency and vibration mode were clarified. The theoretical analysis and the numerical calculation are described. The effects of shearing deformation and rotary inertia on the natural frequency became larger in the higher order vibration. The vibration mode did not much change in both theories. (Kako, I.)
Aircraft gas turbine engine vibration diagnostics
Directory of Open Access Journals (Sweden)
Stanislav Fábry
2017-11-01
Full Text Available In the Czech and Slovak aviation are in service elderly aircrafts, usually produced in former Soviet Union. Their power units can be operated in more efficient way, in case of using additional diagnostic methods that allow evaluating their health. Vibration diagnostics is one of the methods indicating changes of rotational machine dynamics. Ground tests of aircraft gas turbine engines allow vibration recording and analysis. Results contribute to airworthiness evaluation and making corrections, if needed. Vibration sensors distribution, signal recording and processing are introduced in a paper. Recorded and re-calculated vibration parameters are used in role of health indicators.
Investigation on active vibration isolation of a Stewart platform with piezoelectric actuators
Wang, Chaoxin; Xie, Xiling; Chen, Yanhao; Zhang, Zhiyi
2016-11-01
A Stewart platform with piezoelectric actuators is presented for micro-vibration isolation. The Jacobi matrix of the Stewart platform, which reveals the relationship between the position/pointing of the payload and the extensions of the six struts, is derived by kinematic analysis. The dynamic model of the Stewart platform is established by the FRF (frequency response function) synthesis method. In the active control loop, the direct feedback of integrated forces is combined with the FxLMS based adaptive feedback to dampen vibration of inherent modes and suppress transmission of periodic vibrations. Numerical simulations were conducted to prove vibration isolation performance of the Stewart platform under random and periodical disturbances, respectively. In the experiment, the output consistencies of the six piezoelectric actuators were measured at first and the theoretical Jacobi matrix as well as the feedback gain of each piezoelectric actuator was subsequently modified according to the measured consistencies. The direct feedback loop was adjusted to achieve sufficient active damping and the FxLMS based adaptive feedback control was adopted to suppress vibration transmission in the six struts. Experimental results have demonstrated that the Stewart platform can achieve 30 dB attenuation of periodical disturbances and 10-20 dB attenuation of random disturbances in the frequency range of 5-200 Hz.
Zhu, Qiao; Yue, Jun-Zhou; Liu, Wei-Qun; Wang, Xu-Dong; Chen, Jun; Hu, Guang-Di
2017-04-01
This work is focused on the active vibration control of piezoelectric cantilever beam, where an adaptive feedforward controller (AFC) is utilized to reject the vibration with unknown multiple frequencies. First, the experiment setup and its mathematical model are introduced. Due to that the channel between the disturbance and the vibration output is unknown in practice, a concept of equivalent input disturbance (EID) is employed to put an equivalent disturbance into the input channel. In this situation, the vibration control can be achieved by setting the control input be the identified EID. Then, for the EID with known multiple frequencies, the AFC is introduced to perfectly reject the vibration but is sensitive to the frequencies. In order to accurately identify the unknown frequencies of EID in presence of the random disturbances and un-modeled nonlinear dynamics, the time-frequency-analysis (TFA) method is employed to precisely identify the unknown frequencies. Consequently, a TFA-based AFC algorithm is proposed to the active vibration control with unknown frequencies. Finally, four cases are given to illustrate the efficiency of the proposed TFA-based AFC algorithm by experiment.
Coupled lateral-torsional-axial vibrations of a helical gear-rotor-bearing system
Li, Chao-Feng; Zhou, Shi-Hua; Liu, Jie; Wen, Bang-Chun
2014-10-01
Considering the axial and radial loads, a mathematical model of angular contact ball bearing is deduced with Hertz contact theory. With the coupling effects of lateral, torsional and axial vibrations taken into account, a lumped-parameter nonlinear dynamic model of helical gearrotor-bearing system (HGRBS) is established to obtain the transmission system dynamic response to the changes of different parameters. The vibration differential equations of the drive system are derived through the Lagrange equation, which considers the kinetic and potential energies, the dissipative function and the internal/external excitation. Based on the Runge-Kutta numerical method, the dynamics of the HGRBS is investigated, which describes vibration properties of HGRBS more comprehensively. The results show that the vibration amplitudes have obvious fluctuation, and the frequency multiplication and random frequency components become increasingly obvious with changing rotational speed and eccentricity at gear and bearing positions. Axial vibration of the HGRBS also has some fluctuations. The bearing has self-variable stiffness frequency, which should be avoided in engineering design. In addition, the bearing clearance needs little attention due to its slightly discernible effect on vibration response. It is suggested that a careful examination should be made in modelling the nonlinear dynamic behavior of a helical gear-rotor-bearing system.
Flow induced vibrations of piping
International Nuclear Information System (INIS)
Gibert, R.J.; Axisa, F.
1977-01-01
In order to design the supports of piping systems, estimations of the vibrations induced by the fluid conveyed through the pipes are generally needed. For that purpose it is necessary to calculate the model parameters of liquid containing pipes. In most computer codes, fluid effects are accounted for just by adding the fluid mass to the structure. This may lead to serious errors. This paper presents a method to take into account these effects, by solving a coupled mechanical-acoustical problem: the computer code TEDEL of the C.E.A /D.E.M.T. System, based on the finite-elements method, has been extended to calculate simultaneously the pressure fluctuations in the fluid and the vibrations of the pipe. By this way the mechanical-acoustical coupled eigenmodes of any piping system can be obtained. These eigenmodes are used to determine the response of the system to various sources. Equations have been written in the hypohesis that acoustical wave lengths remain large compared to the diameter of the pipe. The method has been checked by an experiment performed on the GASCOGNE loop at D.E.M.T. The piping system under test consists of a tube with four elbows. The circuit is ended at each extremity by a large vessel which performs acoustical isolation by generating modes for the pressure. Excitation of the circuit is caused by a valve located near the downstream vessel. This provides an efficient localised broad band acoustical source. The comparison between the test results and the calculations has shown that the low frequency resonant characteristics of the pipe and the vibrational amplitude at various flow-rates can be correctly predicted
International Nuclear Information System (INIS)
Tahir-Kheli, R.A.
1975-01-01
A few simple problems relating to random magnetic systems are presented. Translational symmetry, only on the macroscopic scale, is assumed for these systems. A random set of parameters, on the microscopic scale, for the various regions of these systems is also assumed. A probability distribution for randomness is obeyed. Knowledge of the form of these probability distributions, is assumed in all cases [pt
EMBEDDED SYSTEMS FOR VIBRATION MONITORING
Directory of Open Access Journals (Sweden)
Miloš Milovančević
2014-08-01
Full Text Available The purpose of the research presented in this paper is the development of the optimal micro configuration for vibration monitoring of pumping aggregate, based on Microchip’s microcontroller (MC. Hardware used is 10-bit MC, upgraded with 12/bit A/D converter. Software for acquisition and data analysis is optimized for testing turbo pumps with rotation speed up to 2000 rpm. This software limitation is set for automatic diagnostics and for individual and manual vibro-diagnostic; the only limitation is set by accelerometer performance. The authors have performed numerous measurements on a wide range of turbo aggregates for establishing the operational condition of pumping aggregates.
Introduction to vibrations and waves
Pain, H John
2015-01-01
Based on the successful multi-edition book "The Physics ofVibrations and Waves" by John Pain, the authors carry overthe simplicity and logic of the approach taken in the originalfirst edition with its focus on the patterns underlying andconnecting so many aspects of physical behavior, whilst bringingthe subject up-to-date so it is relevant to teaching in the21st century.The transmission of energy by wave propagation is a key conceptthat has applications in almost every branch of physics withtransmitting mediums essentially acting as a continuum of coupledoscillators. The characterization of t
Vibration diagnostics instrumentation for ILC
Energy Technology Data Exchange (ETDEWEB)
Bertolini, A.
2007-06-15
The future e{sup -}e{sup +} 500 GeV International Linear Collider will rely on unprecedented nanometer scale particle beam size at the interaction point, in order to achieve the design luminosity. Tight tolerances on static and dynamic alignment of the accelerator cavities and optical components are demanded to transport and focus the high energy electron and positron beams with reasonable position jitter and low emittance. A brief review of techniques and devices evaluated and developed so far for the vibration diagnostics of the machine is presented in this paper. (orig.)