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1

Significant characteristics of social response to noise and vibration  

NASA Technical Reports Server (NTRS)

Several surveys made since 1971 to investigate annoyance resulting from noise and vibration, from various sources were studied in order to quantify the relation between annoyance response to noise or vibration and properties of the respondent including factors such as noise exposure, etc. Samples collected by the social surveys and physical measurements were analyzed by multi-dimensional analysis.

Nishinomiya, G.

1979-01-01

2

Experimental response and vibrational characteristics of a slotted rotor  

NASA Astrophysics Data System (ADS)

This paper proposes to perform experimental tests on the vibrational characteristics of a slotted rotor. Changes in the responses of the n× amplitudes are examined for small and deep slots that can be considered as open cracks. The evolutions of the orbital patterns and the 2× harmonic components near one-half of the first critical speed are investigated in details to propose an efficient indicator of the presence of slots in rotor: a special attention is given to both the comparison of the horizontal and vertical maximum amplitudes of the 2× harmonic components, and changes in the size of the inside loop of orbits when the rotor is passing through one-half of the first critical speed. A huge experimental work considering the influences of the slot depth and the orientation of unbalance relative to the slot direction is investigated in order to examine the possibility of detecting the presence of a transverse slot in rotors.

Sinou, Jean-Jacques

2009-07-01

3

Experimental Research on Vibration Response Characteristics of Air Spring with Auxiliary Chamber  

Microsoft Academic Search

Based on Firestone 1T15M-2 diaphragm type air spring, the experiment system of air spring with auxiliary chamber was established. The influences of orifice diameter and auxiliary chamber volume to vibration response of air spring with auxiliary chamber were studied by the means of experiment. The experiment results show that, with the increase of orifice diameter, the stiffness of air spring

Wang Jiasheng; Zhu Sihong

2010-01-01

4

Vibrational Responses Of Structures To Impulses  

NASA Technical Reports Server (NTRS)

Report discusses propagation of vibrations in structure in response to impulsive and/or concentrated loads. Effects of pulsed loads treated by analyzing propagation of characteristic vibrational waves explicitly through each member of structure. This wave-front analysis used in combination with usual finite-element modal analysis to obtain more accurate representation of overall vibrational behavior.

Zak, Michail A.

1990-01-01

5

Vibration characteristics of circular nanoplates  

NASA Astrophysics Data System (ADS)

This article deals with free vibration of circular nanoplates with consideration of surface properties due to high surface to volume ratio. Classical laminated plate is employed with inclusion of surface elasticity and surface residual stress effects. Solution of the resulting differential equation leads to size dependent behavior of natural frequencies and mode shapes of vibration to be demonstrated. Deviation of the results from conventional theories is shown to be due to changes in the arguments of Bessel functions in the corresponding characteristic equations.

Assadi, Abbas; Farshi, Behrooz

2010-10-01

6

Vibration response of misaligned rotors  

NASA Astrophysics Data System (ADS)

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

Patel, Tejas H.; Darpe, Ashish K.

2009-08-01

7

Vibration  

NASA Technical Reports Server (NTRS)

Man's reactions to vibration are emphasized rather than his reactions to the vibrational characteristics of vehicles. Vibrational effects studies include: performance effects reflected in tracking proficiency, reaction time, visual impairment, and other measures related to man's ability to control a system; physiological reactions; biodynamic responses; subjective reactions; and human tolerance limits. Technological refinements in shaker systems and improved experimental designs are used to validate the data.

Hornick, R. J.

1973-01-01

8

Effect of Vibration on Retention Characteristics of Screen Acquisition Systems  

NASA Technical Reports Server (NTRS)

An analytical and experimental investigation of the effect of vibration on the retention characteristics of screen acquisition systems was performed. The functioning of surface tension devices using fine-mesh screens requires that the pressure differential acting on the screen be less than its pressure retention capability. When exceeded, screen breakdown will occur and gas-free expulsion of propellant will no longer be possible. An analytical approach to predicting the effect of vibration was developed. This approach considers the transmission of the vibration to the screens of the device and the coupling of the liquid and the screen in establishing the screen response. A method of evaluating the transient response of the gas/liquid interface within the screen was also developed.

Tegart, J. R.; Park, A. C.

1977-01-01

9

Impact-absorbing characteristics by applying ultrasonic vibration  

NASA Astrophysics Data System (ADS)

An impact-absorbing device that facilitates the application of ultrasonic vibrations was devised. Vibration distributions, springback characteristics, and impact-absorption characteristics were measured. We confirm that the springback amount decreases and the impact is absorbed upon the application of ultrasonic vibrations. When an aluminum alloy plate is crumpled, the maximum output voltage of the attached shock sensor decreases to 65% upon the application of ultrasonic vibrations as compared to when the ultrasonic vibrations are not applied.

Suzuki, Atsuyuki; Ueki, Eiichiro; Tsujino, Jiromaru

2012-05-01

10

Vibration characteristics of floating slab track  

NASA Astrophysics Data System (ADS)

Coupled equilibrium equations of suspended wheels and floating slab track system were solved with the fourth-order Runge-Kutta method to obtain the deflections, vibration velocities, and wheel-rail contact forces. The program was validated through several aspects. Cases with various vehicle speed, slab mass, and stiffness of slab bearing were analyzed to reveal the effects of slab bearing on track responses. The correlation between wheel-rail resonance and train speed was also discussed. It was found that rail deflections increase significantly as train speed increases. Although large slab mass may lower tuning frequency, it could also result in higher wheel-rail contact force and rail deflections. The floating slab track is effective in isolating loading above 10 Hz, which might present in some railway sections with irregularities. Adopting floating slab track for vibration control for environment along the railway may cause concerns about ride quality and track damages.

Kuo, Chen-Ming; Huang, Cheng-Hao; Chen, Yi-Yi

2008-11-01

11

Vibration characteristics of ultrasonic complex vibration for hole machining  

NASA Astrophysics Data System (ADS)

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

Asami, Takuya; Miura, Hikaru

2012-05-01

12

Vibration characteristics and birefringence of optical disk considering initial stress  

NASA Astrophysics Data System (ADS)

Recently a great deal of effort has been made to increase the data access speed and the data storage density of the optical memory disks such as CD-ROM, DVD, ASMO disk, etc. In the viewpoint of increasing the data access speed of the optical disk, it is of great importance to characterize accurately the vibration phenomena of the rotating disk, which is related to the critical speed and the characteristics of the frequency response. In this paper, we suggest a novel method to improve vibration characteristics of disk without deteriorating optical characteristics. The main idea is that the initial stress in the radial direction is to be imposed within the optical disk on purpose. By the synergy effect from the residual stress frozen in the disk combing the stress induced by the centrifugal force, the stiffness of the disk increases to have stronger resistance to disturbance, resulting in increasing critical speed. In order to enhance the synergy effect, parametric modifications related to the disk design and manufacturing were presented and evaluated. Based on the computer simulation and experiments, we verified the suggested ideas that it clearly improves the vibration characteristics of disk.

Park, Seong J.; Kim, Soo K.; Lee, C. Y.

1999-09-01

13

Technical characteristics of overhead cranes influencing the vibration exposure of the operators.  

PubMed

The study was undertaken to determine the technical factors responsible for the generation of vibration and shocks in overhead cranes and therefore responsible for complaints by the workers. Vibration measurements were made on the floor and on the seat of the cabin on 21 cranes. Vibration levels were correlated with the characteristics of the cranes. The study showed that vibration accelerations increased with the span of the crane and were very dependent upon the state of the runway. The type of speed regulation and the position of the cabin also play a significant role. The suspension systems of the cabin and the seat are clearly inadequate to give significant reduction of the vibration. In several cases, it was even shown to amplify the vibration in the most critical frequency range. These results should be taken into account by designers as well as maintenance services in order to prevent the development of vibration at the source. PMID:15676858

Piette, A; Malchaire, J

1992-04-01

14

Characteristic molecular vibrations of adenosine receptor ligands.  

PubMed

Although the regulation of membrane receptor activation is known to be crucial for molecular signal transduction, the molecular mechanism underlying receptor activation is not fully elucidated. Here we study the physicochemical nature of membrane receptor behavior by investigating the characteristic molecular vibrations of receptor ligands using computational chemistry and informatics methods. By using information gain, t-tests, and support vector machines, we have identified highly informative features of adenosine receptor (AdoR) ligand and corresponding functional amino acid residues such as Asn (6.55) of AdoR that has informative significance and is indispensable for ligand recognition of AdoRs. These findings may provide new perspectives and insights into the fundamental mechanism of class A G protein-coupled receptor activation. PMID:25622891

Chee, Hyun Keun; Yang, Jin-San; Joung, Je-Gun; Zhang, Byoung-Tak; Oh, S June

2015-02-13

15

Effects of vibration characteristics on the walking discomfort of floating floors on concrete slabs.  

PubMed

In the present study, the vibration characteristics of floating floor systems and the discomfort in walking upon them have been studied in concrete slab structures through mock-up floors experiments. Seven types of floor systems, with panels of various sizes and supporting beams with different joist spacings, were constructed based on actual conditions. For the vibration measurement, an ISO rubber ball dropped from a height of 20?cm was used as an impact source to reproduce human walking. The vibration characteristics were evaluated by calculating the vibration acceleration values and the autocorrelation function parameters for the floor structures. Finally, a human walking experiment was conducted to investigate subjective responses to the vibration characteristics of floating floors. From the results, it was found that the vibration acceleration values and walking discomfort varied with the supporting conditions of the floors and that these were highly correlated with each other. It was also found that more than 75% of subjects accepted the floors when the vibration value of the floor in terms of vibration does value (VDV) is below 4.8?ms(-1.75). In addition, a practical regression of the VDV was obtained and design guidelines for floating floors were suggested. PMID:25324073

Kim, Jae Ho; Jeon, Jin Yong

2014-10-01

16

Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness  

NASA Technical Reports Server (NTRS)

A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. Using a perturbation expansion technique the free vibration solution is obtained in a closed-form, and the effects of system parameters on beam response are explored. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.

Townsend, John S.

1987-01-01

17

Nonlinear frequency response analysis of structural vibrations  

NASA Astrophysics Data System (ADS)

In this paper we present a method for nonlinear frequency response analysis of mechanical vibrations of 3-dimensional solid structures. For computing nonlinear frequency response to periodic excitations, we employ the well-established harmonic balance method. A fundamental aspect for allowing a large-scale application of the method is model order reduction of the discretized equation of motion. Therefore we propose the utilization of a modal projection method enhanced with modal derivatives, providing second-order information. For an efficient spatial discretization of continuum mechanics nonlinear partial differential equations, including large deformations and hyperelastic material laws, we employ the concept of isogeometric analysis. Isogeometric finite element methods have already been shown to possess advantages over classical finite element discretizations in terms of higher accuracy of numerical approximations in the fields of linear vibration and static large deformation analysis. With several computational examples, we demonstrate the applicability and accuracy of the modal derivative reduction method for nonlinear static computations and vibration analysis. Thus, the presented method opens a promising perspective on application of nonlinear frequency analysis to large-scale industrial problems.

Weeger, Oliver; Wever, Utz; Simeon, Bernd

2014-12-01

18

Vibration Exposure and Biodynamic Responses during Whole-Body Vibration Training  

Microsoft Academic Search

ABERCROMBY, A. F. J., W. E. AMONETTE, C. S. LAYNE, B. K. MCFARLIN, M. R. HINMAN, and W. H. PALOSKI. Vibration Exposure and Biodynamic Responses during Whole-Body Vibration Training. Med. Sci. Sports Exerc., Vol. 39, No. 10, pp. 1794-1800, 2007. Purpose: Excessive, chronic whole-body vibration (WBV) has a number of negative side effects on the human body, including disorders of

ANDREW F. J. ABERCROMBY; WILLIAM E. AMONETTE; CHARLES S. LAYNE; BRIAN K. MCFARLIN; MARTHA R. HINMAN; WILLIAM H. PALOSKI

2007-01-01

19

Characteristics and principle of the new cyclostationary and non-Gaussian omni-axis vibration environment  

Microsoft Academic Search

The omni-axis random vibration environment characteristics of repetitive shock machine, a new vibration equipment for reliability enhancement testing, is roundly studied. Firstly the omni-axis vibration acceleration is sampled by using triple axis accelerator under different intensity of vibration. Secondly the all-sided characteristics of the vibration signal is extracted according to related index by using mathematic and physical descriptions such as

Jiang Pei; Hou Jianjun

2010-01-01

20

Firmness evaluation of melon using its vibration characteristic and finite element analysis.  

PubMed

The "Huang gua" melons were measured for their physical properties including firmness and static elastic modulus. The vibrational characteristics of fruits and vegetables are governed by their elastic modulus (firmness), mass, and geometry. Therefore, it is possible to evaluate firmness of fruits and vegetables based on their vibrational characteristics. Analysis of the vibration responses of a fruit is suggested for measuring elastic properties (Firmness) non-destructively. The impulse response method is often used to measure firmness of fruits. The fruit was excited using three types of balls (wooden, steel and rubber) and the vibration is detected by an accelerometer. The Instron device was used to measure the static elastic modulus of the inner, middle and outer portions of melon flesh. Finite element (FE) technique was used to determine the optimum excitation location of the chosen measurement sensor and to analyze the mode shape fruits. Four types of mode shapes (torsional or flexural mode shape, first-type, second-type spherical mode and breathing mode shape) were found. Finite element simulation results agreed well with experimental results. Correlation between the firmness and resonant frequency (r2=0.91) and between the resonant frequency and stiffness factor (r2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested. PMID:15909331

Nourain, Jamal; Ying, Yi-bin; Wang, Jian-ping; Rao, Xiu-qin; Yu, Chao-gang

2005-06-01

21

Hormonal responses to whole-body vibration in men  

Microsoft Academic Search

The aim of this study was to evaluate the acute responses of blood hormone concentrations and neuromuscular performance following\\u000a whole-body vibration (WBV) treatment. Fourteen male subjects [mean (SD) age 25 (4.6)?years] were exposed to vertical sinusoidal\\u000a WBV, 10 times for 60?s, with 60?s rest between the vibration sets (a rest period lasting 6?min was allowed after 5 vibration\\u000a sets). Neuromuscular

Carmelo Bosco; M. Iacovelli; O. Tsarpela; M. Cardinale; M. Bonifazi; J. Tihanyi; M. Viru; A. De Lorenzo; A. Viru

2000-01-01

22

Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness  

NASA Technical Reports Server (NTRS)

A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. The effects of system parameters on beam response are explored with a perturbation expansion technique. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.

Townsend, John S.

1987-01-01

23

Aircraft noise induced building vibration and effects on human response  

NASA Technical Reports Server (NTRS)

The acoustic loads resulting from aircraft noise and sonic booms which can induce vibration in the structure and result in radiation of noise into its interior, rattling of items in contact with the structure, and the perception of the inhabitants that the structure is vibrating, are investigated. In particular, the response of buildings, particularly residential structures, to aircraft noise and the resulting effects on human response have been the subjects of considerable research at the NASA Langley Research Center. These studies are reviewed with particular emphasis on the response of houses to aircraft overflight noise and any increase in noise annoyance caused by the perception of vibration and rattling.

Powell, Clemans A.; Shepherd, Kevin P.

1989-01-01

24

Human discomfort response to noise combined with vertical vibration  

NASA Technical Reports Server (NTRS)

An experimental investigation was conducted (1) to determine the effects of combined environmental noise and vertical vibration upon human subjective discomfort response, (2) to develop a model for the prediction of passenger discomfort response to the combined environment, and (3) to develop a set of noise-vibration curves for use as criteria in ride quality design. Subjects were exposed to parametric combinations of noise and vibrations through the use of a realistic laboratory simulator. Results indicated that accurate prediction of passenger ride comfort requires knowledge of both the level and frequency content of the noise and vibration components of a ride environment as well as knowledge of the interactive effects of combined noise and vibration. A design tool in the form of an empirical model of passenger discomfort response to combined noise and vertical vibration was developed and illustrated by several computational examples. Finally, a set of noise-vibration criteria curves were generated to illustrate the fundamental design trade-off possible between passenger discomfort and the noise-vibration levels that produce the discomfort.

Leatherwood, J. D.

1979-01-01

25

Evaluation of High Freuqency Vibrator Response  

E-print Network

Accurate analysis of the motion of a commercial high frequency hydraulic vibrator commonly used for near-surface applications demonstrated that the rigid body assumption of the weighted-sum approximation is not valid ...

Hendrix, Craig Michael

2012-08-12

26

Vibration and formability characteristics of aluminum-polymer sandwich materials  

NASA Astrophysics Data System (ADS)

Metal/polymer/metal sandwich materials are finding increasing use in the automotive industry primarily as lightweight alternatives to steel and aluminum alloys. In addition to low density they also offer other functional benefits e.g. improved vibration damping. In order to exploit such beneficial characteristics it is necessary to examine the manufacturability of these materials. In this work the vibration characteristics and formability were examined in selected materials, chosen from a group of aluminum/polypropylene/aluminum sandwich materials. First, a systematic study was carried out on vibration characteristics of square sandwich plates using 3D finite element models and usefulness of such a 3D displacement field in understanding the damping mechanisms as well as their contributions toward the modal damping were discussed. Second, a study of stretch formability of several sandwich materials was conducted. Since the knowledge of tensile properties is essential for understanding the formability, those properties were determined by performing uniaxial tensile tests on several aluminum/polypropylene/aluminum (HyliteRTM) sandwich materials and their constituent materials. The phenomena of diffused necking and deformation of material up to and beyond the point of necking were systematically investigated. Furthermore, the formability of sandwich materials was assessed by comparing the experimentally determined forming limit diagrams (FLDs) of monolithic 5182 aluminum and several sandwich materials. In addition to the experimental research, theoretical modeling was carried out to predict formability based on the concept of growth of pre-existing defects. One such model, known as M-K analysis, was utilized on the basis of defects existing in (i) the aluminum skins and (ii) the overall thickness of the sandwich. The experimental and theoretical results suggest that the levels of forming limit in sandwich materials are far less than those for monolithic materials of equivalent stiffness. This result may be related to smaller defect factor in the skin of the sandwich materials.

Somayajulu, Thamma S. V.

27

The flaminio obelisk in Rome: vibrational characteristics as part of preservation efforts  

USGS Publications Warehouse

The purpose of the paper is to study the vibrational characteristics of the Flaminio Obelisk in Rome as part of general studies being performed for preservation purposes. The state of preservation of the monument is described as well as the sonic method used to evaluate the integrity of the sections. The results of the sonic tests are used to determine reductions in the cross-sectional properties. A stick model including two rotational frequency independent soil springs at the basement level of the obelisk is developed. A response spectrum and stress analysis according to the Italian Seismic Code is performed considering and evaluating the degraded characteristics of sections. -from Authors

Bongiovanni, G.; Celebi, M.; Clemente, P.

1990-01-01

28

NORTHWESTERN UNIVERSITY Residential Crack Response to Vibrations from Underground Mining  

E-print Network

facilitates simultaneous measurement of crack response to environmental changes and various dynamic events. These crack responses to blast vibrations were compared to responses to environmental changes as well as occupant activities. The second component was the design and qualification of a mounting system to measure

29

Damage Identification of Piles Based on Vibration Characteristics  

PubMed Central

A method of damage identification of piles was established by using vibration characteristics. The approach focused on the application of the element strain energy and sensitive modals. A damage identification equation of piles was deduced using the structural vibration equation. The equation contained three major factors: change rate of element modal strain energy, damage factor of pile, and sensitivity factor of modal damage. The sensitive modals of damage identification were selected by using sensitivity factor of modal damage firstly. Subsequently, the indexes for early-warning of pile damage were established by applying the change rate of strain energy. Then the technology of computational analysis of wavelet transform was used to damage identification for pile. The identification of small damage of pile was completely achieved, including the location of damage and the extent of damage. In the process of identifying the extent of damage of pile, the equation of damage identification was used in many times. Finally, a stadium project was used as an example to demonstrate the effectiveness of the proposed method of damage identification for piles. The correctness and practicability of the proposed method were verified by comparing the results of damage identification with that of low strain test. The research provided a new way for damage identification of piles. PMID:25506062

Zhang, Xiaozhong; Yao, Wenjuan; Chen, Bo; Liu, Dewen

2014-01-01

30

Automated calculation of anharmonic vibrational contributions to first hyperpolarizabilities: quadratic response functions from vibrational configuration interaction wave functions.  

PubMed

Quadratic response functions are derived and implemented for a vibrational configuration interaction state. Combined electronic and vibrational quadratic response functions are derived using Born-Oppenheimer vibronic product wave functions. Computational tractable expressions are derived for determining the total quadratic response contribution as a sum of contributions involving both electronic and vibrational linear and quadratic response functions. In the general frequency-dependent case this includes a new and more troublesome type of electronic linear response function. Pilot calculations for the FH, H(2)O, CH(2)O, and pyrrole molecules demonstrate the importance of vibrational contributions for accurate comparison to experiment and that the vibrational contributions in some cases can be very large. The calculation of transition properties between vibrational states is combined with sum-over-states expressions for analysis purposes. On the basis of this some simple analysis methods are suggested. Also, a preliminary study of the effect of finite lifetimes on quadratic response functions is presented. PMID:20568841

Hansen, Mikkel Bo; Christiansen, Ove; Hättig, Christof

2009-10-21

31

An optimized semiclassical approximation for vibrational response functions  

PubMed Central

The observables of multidimensional infrared spectroscopy may be calculated from nonlinear vibrational response functions. Fully quantum dynamical calculations of vibrational response functions are generally impractical, while completely classical calculations are qualitatively incorrect at long times. These challenges motivate the development of semiclassical approximations to quantum mechanics, which use classical mechanical information to reconstruct quantum effects. The mean-trajectory (MT) approximation is a semiclassical approach to quantum vibrational response functions employing classical trajectories linked by deterministic transitions representing the effects of the radiation-matter interaction. Previous application of the MT approximation to the third-order response function R(3)(t3, t2, t1) demonstrated that the method quantitatively describes the coherence dynamics of the t3 and t1 evolution times, but is qualitatively incorrect for the waiting-time t2 period. Here we develop an optimized version of the MT approximation by elucidating the connection between this semiclassical approach and the double-sided Feynman diagrams (2FD) that represent the quantum response. Establishing the direct connection between 2FD and semiclassical paths motivates a systematic derivation of an optimized MT approximation (OMT). The OMT uses classical mechanical inputs to accurately reproduce quantum dynamics associated with all three propagation times of the third-order vibrational response function. PMID:23556706

Gerace, Mallory; Loring, Roger F.

2013-01-01

32

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

NASA Astrophysics Data System (ADS)

As externally bonded fiber-reinforced polymer (FRP) is a critical load-bearing component of strengthened or retrofitted civil infrastructures, the betterment of structural health monitoring (SHM) methodology for such composites is imperative. Henceforth the vibrational characteristics of near surface interfacial defects involving delamination and trapped air pockets at the FRP-concrete interface are investigated in this study using a finite element approach. Intuitively, due to its lower interfacial stiffness compared with an intact interface, a damaged region is expected to have a set of resonance frequencies different from an intact region when excited by acoustic waves. It has been observed that, when excited acoustically, both the vibrational amplitudes and frequency peaks in the response spectrum of the defects demonstrate a significant deviation from an intact FRP-bonded region. For a thin sheet of FRP bonded to concrete with sizable interfacial defects, the fundamental mode under free vibration is shown to be relatively low, in the order of kHz. Due to the low resonance frequencies of the defects, the use of low-cost equipment for interfacial defect detection via response spectrum analysis is highly feasible.

Cheng, Tin Kei; Lau, Denvid

2014-04-01

33

Vibrational coupled cluster response theory: a general implementation.  

PubMed

The calculation of vibrational contributions to molecular properties using vibrational coupled cluster (VCC) response theory is discussed. General expressions are given for expectation values, linear response functions, and transition moments. It is shown how these expressions can be evaluated for arbitrary levels of excitation in the wave function parameterization as well as for arbitrary coupling levels in the potential and property surfaces. The convergence of the method is assessed by benchmark calculations on formaldehyde. Furthermore, excitation energies and infrared intensities are calculated for the fundamental vibrations of furan using VCC limited to up to two-mode and up to three-mode excitations, VCC[2] and VCC[3], as well as VCC with full two-mode and approximate three-mode couplings, VCC[2pt3]. PMID:21303104

Seidler, Peter; Sparta, Manuel; Christiansen, Ove

2011-02-01

34

Analytical design and evaluation of an active control system for helicopter vibration reduction and gust response alleviation  

NASA Technical Reports Server (NTRS)

An analytical study was conducted to define the basic configuration of an active control system for helicopter vibration and gust response alleviation. The study culminated in a control system design which has two separate systems: narrow band loop for vibration reduction and wider band loop for gust response alleviation. The narrow band vibration loop utilizes the standard swashplate control configuration to input controller for the vibration loop is based on adaptive optimal control theory and is designed to adapt to any flight condition including maneuvers and transients. The prime characteristics of the vibration control system is its real time capability. The gust alleviation control system studied consists of optimal sampled data feedback gains together with an optimal one-step-ahead prediction. The prediction permits the estimation of the gust disturbance which can then be used to minimize the gust effects on the helicopter.

Taylor, R. B.; Zwicke, P. E.; Gold, P.; Miao, W.

1980-01-01

35

Vibration Response Imaging (VRI) of the Lungs in Pediatric Patients  

Microsoft Academic Search

Background: Pediatric chest imaging such as chest radiology and computed tomography largely contribute to the diagnosis and management of pediatric pulmonary disorders 1 . However, these technologies emit radiation 2 and cannot detect the whole range of pulmonary complaints 3,4 . Vibration Response Imaging (VRI) is a novel technology providing a non-invasive, radiation free dynamic image of the lungs. A

G. Livnat; F. Hakim; L. Bentur

36

Rocket Launch-Induced Vibration and Ignition Overpressure Response  

NASA Technical Reports Server (NTRS)

Rocket-induced vibration and ignition overpressure response environments are predicted in the low-frequency (5 to 200 hertz) range. The predictions are necessary to evaluate their impact on critical components, structures, and facilities in the immediate vicinity of the rocket launch pad.

Caimi, Raoul E.; Margashayam, Ravi N.; Nayfeh, Jamal F.; Thompson, Karen (Technical Monitor)

2001-01-01

37

Cell Mechanotransduction: Cell ResponsesTo NanoscaleVibrations  

E-print Network

and for stem cell transplant Can use osteogenic chemicals however not always in vivo Image of cellular-scale patterns Nanoscale topographies being produced via electron beam lithography Mesenchymal stem cells (MSCCell Mechanotransduction: Cell ResponsesTo NanoscaleVibrations Peter Childs, Stuart Reid, Fiona

Greenaway, Alan

38

Comparative evaluation of Space Transportation System (STS)-3 flight and acoustic test random vibration response of the OSS-1 payload  

NASA Technical Reports Server (NTRS)

A comparative evaluation of the Space Transportation System (STS)-3 flight and acoustic test random vibration response of the Office of Space Science-1 (OSS-1) payload is presented. The results provide insight into the characteristics of vibroacoustic response of pallet payload components in the payload bay during STS flights.

On, F. J.

1983-01-01

39

RESPONSE OF CRACKS TO CONSTRUCTION VIBRATIONS AND ENVIRONMENTAL EFFECTS  

Microsoft Academic Search

This paper summarizes micro-inch response of cosmetic cracks in a typical slab-on- grade ranch style house to both construction equipment-induced vibration and environmental (weather) effects. This structure was instrumented, and its response studied as part of the development of an Autonomous Crack Measurement (ACM) system. ACM systems are intended to record -- with a single sensor -- micro-inch crack displacements

Charles H. Dowding; Mickey L. Snider

40

Vibration characteristics of OH-58A helicopter main rotor transmission  

NASA Technical Reports Server (NTRS)

Experimental vibration tests covering a range of torque and speed conditions were performed on the OH-58A helicopter main rotor transmission at the NASA Lewis Research Center. Signals from accelerometers located on the transmission housing were analyzed by using Fourier spectra, power spectral density functions, and averaging techniques. Most peaks of the Fourier spectra occurred at the spiral bevel and planetary gear mesh harmonics. The highest level of vibration occurred at the spiral bevel meshing frequency. Transmission speed and vibration measurement location had a significant effect on measured vibration; transmission torque and measurement direction had a small effect.

Lewicki, David G.; Coy, John J.

1987-01-01

41

Semiclassical nonlinear response functions for coupled anharmonic vibrations.  

PubMed

Observables in linear and nonlinear infrared spectroscopy may be computed from vibrational response functions describing nuclear dynamics on a single electronic surface. We demonstrate that the Herman-Kluk (HK) semiclassical approximation to the quantum propagator yields an accurate representation of quantum coherence effects in linear and nonlinear response functions for coupled anharmonic oscillators. A considerable numerical price is paid for this accuracy; the calculation requires a multidimensional integral over a highly oscillatory integrand that also grows without bound as a function of evolution times. The interference among classical trajectories in the HK approximation produces quantization of good action variables. By treating this interference analytically, we develop a mean-trajectory (MT) approximation that requires only the propagation of classical trajectories linked by transitions in action. The MT approximation accurately reproduces coherence effects in response functions of coupled anharmonic oscillators in a regime in which the observables are strongly influenced by these interactions among vibrations. PMID:19947691

Gruenbaum, Scott M; Loring, Roger F

2009-11-28

42

Characteristics of spaceborne cooler passive vibration isolator by using a compressed shape memory alloy mesh washer  

NASA Astrophysics Data System (ADS)

Cryogenic coolers produce undesirable micro-vibrations during on-orbit operation, which may seriously affect the image quality of high-resolution observation satellites. Micro-vibrations can be easily isolated by mounting the cooler on a vibration isolator with low stiffness to attenuate the vibration transmitted to the satellite structure. However, the structural safety of a cooler supported by an isolator with low stiffness cannot be guaranteed under the much more severe vibration condition of a launch environment. In this study, to guarantee vibration isolation performance in a launch environment while effectively isolating the micro-vibrations from the cooler on-orbit, a new type of passive vibration isolation system by using a compressed shape memory alloy mesh washer was proposed and investigated. The basic characteristics of the isolator were measured in static and free vibration tests of the isolator, and a simple equivalent model of the isolator was proposed. The effectiveness of the isolator design in a launch environment was demonstrated through sine vibration, random vibration, and shock tests.

Oh, Hyun-Ung; Kwon, Seong-Cheol; Youn, Se-Hyun

2015-01-01

43

Vibration characteristics of ring-stiffened orthotropic shells of revolution  

NASA Technical Reports Server (NTRS)

Computer program solves vibration modes and frequencies of thin shells of revolution having general meridional curvature and orthotropic elastic properties in order to evaluate the dynamic behavior of structures with thin shelled components.

Adelman, H. M.; Catherines, D. S.; Durling, B. J.; Steeves, E. C.; Walton, W. C., Jr.

1971-01-01

44

Vibration characteristics of composite fan blades and comparison with measured data  

NASA Technical Reports Server (NTRS)

The vibration characteristics of a composite fan blade for high-tip-speed applications were determined theoretically and the results compared with measured data. The theoretical results were obtained using a computerized capability consisting of NASTRAN coupled with composite mechanics by way of pre- and postprocessors. The predicted vibration frequencies and mode shapes were in reasonable agreement with the measured data. Theoretical results showed that different laminate configurations from the same composite system had only small effects on the blade frequency. However, the use of adhesively bonded titanium/beryllium laminar composites may improve considerably the blade vibration characteristics.

Chamis, C. C.

1976-01-01

45

Non-linear torsional vibration characteristics of an internal combustion engine crankshaft assembly  

NASA Astrophysics Data System (ADS)

Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines. The linear lumped mass method, which has been universally applied to the dynamic modeling of engine crankshaft assembly, reveals obvious simulation errors. The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness. In this paper, a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method. The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments. The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method. The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method. The simulation results are compared with a lumped mass model and a detailed model using the system matrix method. Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration, and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor. The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia. This research project is aimed at improving nonlinear dynamics theory, and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.

Huang, Ying; Yang, Shouping; Zhang, Fujun; Zhao, Changlu; Ling, Qiang; Wang, Haiyan

2012-07-01

46

Optimization of Training Sets for Neural-Net Processing of Characteristic Patterns from Vibrating Solids  

NASA Technical Reports Server (NTRS)

Artificial neural networks have been used for a number of years to process holography-generated characteristic patterns of vibrating structures. This technology depends critically on the selection and the conditioning of the training sets. A scaling operation called folding is discussed for conditioning training sets optimally for training feed-forward neural networks to process characteristic fringe patterns. Folding allows feed-forward nets to be trained easily to detect damage-induced vibration-displacement-distribution changes as small as 10 nm. A specific application to aerospace of neural-net processing of characteristic patterns is presented to motivate the conditioning and optimization effort.

Decker, Arthur J.

2001-01-01

47

Modeling vibration response and damping of cables and cabled structures  

NASA Astrophysics Data System (ADS)

In an effort to model the vibration response of cabled structures, the distributed transfer function method is developed to model cables and a simple cabled structure. The model includes shear effects, tension, and hysteretic damping for modeling of helical stranded cables, and includes a method for modeling cable attachment points using both linear and rotational damping and stiffness. The damped cable model shows agreement with experimental data for four types of stranded cables, and the damped cabled beam model shows agreement with experimental data for the cables attached to a beam structure, as well as improvement over the distributed mass method for cabled structure modeling.

Spak, Kaitlin S.; Agnes, Gregory S.; Inman, Daniel J.

2015-02-01

48

Analysis of proposed criteria for human response to vibration  

NASA Technical Reports Server (NTRS)

The development of criteria for human vibration response is reviewed, including the evolution of the ISO standard 2631. The document is analyzed to show why its application to vehicle ride evaluation is strongly opposed. Alternative vertical horizontal limits for comfort are recommended in the ground vehicle ride frequency range above 1 Hz. These values are derived by correlating the absorbed power findings of Pradko and Lee with other established criteria. Special emphasis is placed on working limits in the frequency range of 1 to 10 Hz since this is the most significant area in ground vehicle ride evaluation.

Janeway, R. N.

1975-01-01

49

Vibration Characteristics of a Vertical Round Tube According to Heat Transfer Regimes  

SciTech Connect

This paper presents the results of an experimental work on the effects of boiling heat transfer regimes on the flow-induced vibration (FIV). The experiment has been performed using an electrically heated vertical round tube through which water flows at atmospheric pressure. Vibration characteristics of the heated tube are changed significantly by heat transfer regimes and flow patterns. For single-phase liquid convection, the rod vibrations are negligible. However, on the beginning of subcooled nucleate boiling at tube exit, vibration level becomes very large. As bubble departure occurs at the nucleation site of heated surface, the vibration decreases to saturated boiling region where thermal equilibrium quality becomes 0.0 at tube exit. In saturated boiling region, vibration amplitude increases with exit quality up to a certain maximum value due to the reinforced turbulence then decreases. At liquid film dryout condition, vibration could be regarded as negligible, however, these results cannot be extended to DNB-type CHF mechanism. Frequency analysis results of vibration signals suggested that excitation sources be different with heat transfer regimes. This study would contribute to improve the understanding of the relationship between boiling heat transfer and FIV. (authors)

Yong Ho Lee; Soon Heung Chang [Korea Advanced Institute of Science and Technology, 373-1, Guseung-dong, Yuseong-ku, Daejeon, 305-701 (Korea, Republic of); Won-Pil Baek [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)

2002-07-01

50

Hormonal responses to whole-body vibration in men.  

PubMed

The aim of this study was to evaluate the acute responses of blood hormone concentrations and neuromuscular performance following whole-body vibration (WBV) treatment. Fourteen male subjects [mean (SD) age 25 (4.6) years] were exposed to vertical sinusoidal WBV, 10 times for 60 s, with 60 s rest between the vibration sets (a rest period lasting 6 min was allowed after 5 vibration sets). Neuromuscular performance tests consisting of counter-movement jumps and maximal dynamic leg presses on a slide machine, performed with an extra load of 160% of the subjects body mass, and with both legs were administered before and immediately after the WBV treatment. The average velocity, acceleration, average force, and power were calculated and the root mean square electromyogram (EMGrms) were recorded from the vastus lateralis and rectus femoris muscles simultaneously during the leg-press measurement. Blood samples were also collected, and plasma concentrations of testosterone (T), growth hormone (GH) and cortisol (C) were measured. The results showed a significant increase in the plasma concentration of T and GH, whereas C levels decreased. An increase in the mechanical power output of the leg extensor muscles was observed together with a reduction in EMGrms activity. Neuromuscular efficiency improved, as indicated by the decrease in the ratio between EMGrms and power. Jumping performance, which was measured using the counter-movement jump test, was also enhanced. Thus, it can be argued that the biological mechanism produced by vibration is similar to the effect produced by explosive power training (jumping and bouncing). The enhancement of explosive power could have been induced by an increase in the synchronisation activity of the motor units, and/or improved co-ordination of the synergistic muscles and increased inhibition of the antagonists. These results suggest that WBV treatment leads to acute responses of hormonal profile and neuromuscular performance. It is therefore likely that the effect of WBV treatment elicited a biological adaptation that is connected to a neural potentiation effect, similar to those reported to occur following resistance and explosive power training. In conclusion, it is suggested that WBV influences proprioceptive feedback mechanisms and specific neural components, leading to an improvement of neuromuscular performance. Moreover, since the hormonal responses, characterised by an increase in T and GH concentration and a decrease in C concentration, and the increase in neuromuscular effectiveness were simultaneous but independent, it is speculated that the two phenomena might have common underlying mechanisms. PMID:10774867

Bosco, C; Iacovelli, M; Tsarpela, O; Cardinale, M; Bonifazi, M; Tihanyi, J; Viru, M; De Lorenzo, A; Viru, A

2000-04-01

51

Evaluation of human response to structural vibrations induced by sonic booms  

NASA Technical Reports Server (NTRS)

The topic is addressed of building vibration response to sonic boom and the evaluation of the associated human response to this vibration. An attempt is made to reexamine some of the issues addressed previously and to offer fresh insight that may assist in reassessing the potential impact of sonic boom over populated areas. Human response to vibration is reviewed first and a new human vibration response criterion curve is developed as a function of frequency. The difference between response to steady state versus impulsive vibration is addressed and a 'vibration exposure' or 'vibration energy' descriptor is suggested as one possible way to evaluate duration effects on response to transient vibration from sonic booms. New data on the acoustic signature of rattling objects are presented along with a review of existing data on the occurrence of rattle. Structural response to sonic boom is reviewed and a new descriptor, 'Acceleration Exposure Level' is suggested which can be easily determined from the Fourier Spectrum of a sonic boom. A preliminary assessment of potential impact from sonic booms is provided in terms of human response to vibration and detection of rattle based on a synthesis of the preceding material.

Sutherland, Louis C.; Czech, J.

1992-01-01

52

Dose-response relation between exposure to two types of hand-arm vibration and sensorineural perception of vibration.  

PubMed Central

OBJECTIVES--31 railway workers and 32 lumberjacks were examined to compare the dose-response relation between the exposure to two types of hand-arm vibration and the sensory disturbances in peripheral nerves as evaluated by the vibration perception thresholds (VPTs). METHODS--Clinical examinations were carried out that included measurements of the VPTs, and electroneuromyography (ENMG), and an inquiry to confirm the use of vibrating tools. Diseases of the central nervous system and neuropathies were checked by inquiry and a clinical examination, diabetes was excluded by a blood sample analysis, and the subjects with carpal tunnel syndrome confirmed with ENMG were excluded from the study. RESULTS--Lifetime use of hand held tamping machines (railway workers) and chain saws (lumberjacks) had a significant correlation with the VPTs at frequencies from 32 to 500 Hz. The increase of the VPTs (250 Hz) in relation to use of vibrating tools was 1.8-fold higher on average in the whole group and 2.3-fold higher in the young (< 45) railway workers who had used hand held tamping machines, than in the corresponding groups of lumberjacks, who had used chain saws, whereas the frequency weighted acceleration of vibration in tamping machines was fourfold. CONCLUSION--There was a significant dose-response relation between the exposure to hand-arm vibration and the VPTs. The VPTs as a function of the frequency weighted acceleration of vibration and the exposure to vibration gave promising results for assessment of the risk of damage to sensory nerves induced by vibration. PMID:7795756

Virokannas, H

1995-01-01

53

Research on vibration response of a multi-faulted rotor system using LMD-based time-frequency representation  

NASA Astrophysics Data System (ADS)

Unbalance, fatigue crack and rotor-stator rub are the three common and important faults in a rotor-bearing system. They are originally interconnected each other, and their vibration behaviors do often show strong nonlinear and transient characteristic, especially when more than one of them coexist in the system. This article is aimed to study the vibration response of the rotor system in presence of multiple rotor faults such as unbalance, crack, and rotor-stator rub, using local mean decomposition-based time-frequency representation. Equations of motion of the multi-faulted Jeffcott rotor, including unbalance, crack, and rub, are presented. By solving the motion equations, steady-state vibration response is obtained in presence of multiple rotor faults. As a comparison, Hilbert-Huang transformation, based on empirical mode decomposition, is also applied to analyze the multi-faults data. By the study some diagnostic recommendations are derived.

Jiao, Weidong; Qian, Suxiang; Chang, Yongping; Yang, Shixi

2012-12-01

54

Vibration testing based on impulse response excited by laser ablation  

NASA Astrophysics Data System (ADS)

This paper proposes an innovative vibration testing method based on impulse response excited by laser ablation. In conventional vibration testing using an impulse hammer, high-frequency elements of over tens of kilohertz are barely present in the excitation force. A pulsed high-power YAG laser is used in this study for producing an ideal impulse force on a structural surface. Illuminating a point on a metal with the well-focused YAG laser, laser ablation is caused by generation of plasma on the metal. As a result, an ideal impulse excitation force generated by laser ablation is applied to the point on the structure. Therefore, it is possible to measure high-frequency FRFs due to the laser excitation. A water droplet overlay on the metal is used to adjust the force magnitude of laser excitation. An aluminum block that has nine natural frequencies below 40 kHz is employed as a test piece. The validity of the proposed method is verified by comparing the FRFs of the block obtained by the laser excitation, impulse hammer, and finite element analysis. Furthermore, the relationship between accuracy of FRF measurements and sensitivity of sensors is investigated.

Kajiwara, Itsuro; Hosoya, Naoki

2011-10-01

55

Vibration Characteristics of Piezoelectric Lead Zirconate Titanate by Fluid Flow in Intravascular Oxygenator  

NASA Astrophysics Data System (ADS)

In this paper, we describe the enhancement in oxygen transfer rate in hollow-fiber-membrane (HFM) modules using a plumbum piezoelectric lead zirconate titanate (PZT) actuator and a piezoelectric poly vinylidene fluoride (PVDF) sensor. We developed a vibrating intravascular lung assist device (VIVLAD) for patients having chronic respiratory problems and performed experiments on hydrodynamic flow through a bundle of sinusoidal vibrating hollow fibers. These modules were used to provide some insight into how wall vibrations might enhance the performance of an intravascular lung assist device. The experimental design and procedure are then applied to the fabrication of a device used to assess the effectiveness of membrane vibrations. The test section was a cylindrical duct with an inner diameter of 30 mm. The flow rate was controlled by a pump and monitored by a built-in flowmeter. The vibration apparatus was composed of a piezovibrator, a function generator, and a power amplifier. The direction of vibration was radial to the fluid flow. Gas flow rates of up to 6 L/min through 120-cm-long hollow fibers were achieved by exciting the piezovibrator. The time and frequency responses of PVDF sensors were investigated through various frequencies in VIVLAD. In these devices, the flow of blood and the source of oxygen were separated by a semipermeable membrane that allows oxygen and carbon dioxide to diffuse into and out of the fluid, respectively. Results of the experiments have shown that a vibrating intravascular lung assist device performs effectively.

Kim, Gi?Beum; Hong, Chul?Un; Kwon, Tae?Kyu

2006-04-01

56

Effect of vibration on retention characteristics of screen acquisition systems. [for surface tension propellant acquisition  

NASA Technical Reports Server (NTRS)

The design of surface tension propellant acquisition systems using fine-mesh screen must take into account all factors that influence the liquid pressure differentials within the system. One of those factors is spacecraft vibration. Analytical models to predict the effects of vibration have been developed. A test program to verify the analytical models and to allow a comparative evaluation of the parameters influencing the response to vibration was performed. Screen specimens were tested under conditions simulating the operation of an acquisition system, considering the effects of such parameters as screen orientation and configuration, screen support method, screen mesh, liquid flow and liquid properties. An analytical model, based on empirical coefficients, was most successful in predicting the effects of vibration.

Tegart, J. R.; Aydelott, J. C.

1978-01-01

57

Seismic site-response analysis based on random vibration theory  

NASA Astrophysics Data System (ADS)

Local geology influences earthquake ground motions, which is of importance in specifying ground motion levels for seismic design in practice. This effect is quantified through site response analysis, which involves the propagation of seismic waves from bedrock to the free surface through soft layers. Site response analysis provides a set or several sets of scale factors given as function of frequency at the surface. Empirical characterization of site response requires a large data set over a wide range of magnitudes and distances of events. In reality, especially in low to moderate seismicity regions such as the Korean Peninsula, empirical characterization of site response is not plausible. Thus numerical modeling is only a viable tool for site response in those regions. On the other hand, most of conventional modeling procedures include a step for developing some appropriate synthetic waveforms as input motions to be used in site response analyses. The waveforms are typically synthesized by matching the spectrum, such as uniform hazard response spectrum, on basement rock obtained from the seismic hazard analysis. However, these synthetics are fundamentally problematic in spite of spectral matching because it is based on the amplitude spectrum only without phase information. As an alternative, an approach based on random vibration theory (RVT) is introduced without the need of waveform generations. RVT explains that a given response spectrum can be converted into a power spectrum density function. It is performed in the frequency domain and deals with the statistical representation of responses. It requires the transfer function for the velocity profile of a site. The transfer function is initially developed by computations of receiver functions using the reflectivity method assuming no attenuation for the profile under consideration of various incidence angles. Then the transfer function is iteratively updated with varying attenuation until the results are compatible with the observed modulus and damping which can be obtained through the in-situ or lab tests for the profile. After the final iteration on the transfer function, the maximum amplification responses can be obtained with the extreme values of shear stress and strain on the profile. Thus this approach combines the observational results of material properties with the analytical results based on the reflectivity calculations of a layered structure, which makes it able to estimate site response in reducing unphysical manipulations.

Kang, T.; Jang, H.

2013-12-01

58

Material characteristics of a vehicle door seal and its effect on vehicle vibrations  

Microsoft Academic Search

The vibration characteristics of the door panels are affected by the weatherstrip seals used in between the doors and vehicle body along the perimeter of the doors. The weatherstrip seals exhibit nonlinear and viscoelastic material properties that vary with frequency, temperature, strain rate and amplitude, and previous load history. The material properties of the seal must be investigated carefully in

E. Dikmen; I. Basdogan

2008-01-01

59

Comparative biodynamic response of two primate species to the same vibrational environment.  

PubMed

Four Rhesus monkeys and three baboons, all young adult males of nearly the same size (8-17 kg), were implanted with an accelerometer on the upper thoracic and lower lumbar spinous process, respectively. Each animal was exposed to sinusoidal vibrations from 4 to 50 Hz at +/- 0.177 and 0.283 rms GZ acceleration levels, respectively, for approximately 30 s/frequency and to the whole vibration spectrum for about 1h X d-1 up to 4 consecutive days. The impedance magnitude, impedance phase and transmissibility between the seat and two spinal accelerometers were compared at the two acceleration levels. The resonant frequency, other impedance characteristics, and the linearity of the response were compared between the two primate species. Modeling parameters, including the damping and elastic coefficients and spring mass, were calculated from impedance data using an established two-mass model. The majority of each species showed a tendency to be less rigid at 0.283 rms Gz than the lower G level, suggesting more decoupling from the seat with higher acceleration. Over most of the frequency range tested, all the animals vibrated out of phase rather than rigidly with the seat. When the impedance and transmissibility results of the two species were plotted and compared, it raised the question of the phylogenicity and the appropriateness of selecting as a biodynamic model the baboon over the Rhesus monkey in the interspecies scaling efforts up to man. PMID:4062769

Slonim, A R

1985-10-01

60

[Short-term memory characteristics of vibration intensity tactile perception on human wrist].  

PubMed

In this study, a recall experiment and a recognition experiment were designed to assess the human wrist's short-term memory characteristics of tactile perception on vibration intensity, by using a novel homemade vibrotactile display device based on the spatiotemporal combination vibration of multiple micro vibration motors as a test device. Based on the obtained experimental data, the short-term memory span, recognition accuracy and reaction time of vibration intensity were analyzed. From the experimental results, some important conclusions can be made: (1) The average short-term memory span of tactile perception on vibration intensity is 3 ± 1 items; (2) The greater difference between two adjacent discrete intensities of vibrotactile stimulation is defined, the better average short-term memory span human wrist gets; (3) There is an obvious difference of the average short-term memory span on vibration intensity between the male and female; (4) The mechanism of information extraction in short-term memory of vibrotactile display is to traverse the scanning process by comparison; (5) The recognition accuracy and reaction time performance of vibrotactile display compares unfavourably with that of visual and auditory. The results from this study are important for designing vibrotactile display coding scheme. PMID:25516517

Hao, Fei; Chen, Li-Juan; Lu, Wei; Song, Ai-Guo

2014-12-25

61

Light-induced vibration characteristics of free-standing carbon nanotube films fabricated by vacuum filtration  

NASA Astrophysics Data System (ADS)

In this paper, we fabricated carbon nanotube (CNT) films with different thickness by vacuum filtration method, and the films were separated from Mixed Cellulose Ester membranes with burn-off process. The thickness of CNT films with different concentrations of CNTs 50 mg, 100 mg, 150 mg, and 200 mg are 10.36 ?m, 20.90 ?m, 30.19 ?m, and 39.98 ?m respectively. The CNT bundles are homogeneously distributed and entangled with each other, and still maintain 2D continuous network structures after burn-off process. The optical absorptivity of the films is between 84% and 99% at wavelengths ranging from 400 nm to 2500 nm. Vibration characteristics were measured with the Fabry-Perot (F-P) interferometer vibration measurement system. CNT films vibrate only under the xenon light irradiating perpendicularly to the surface. Vibration recorded by Fabry-Perot interferometer is considered to be caused by the time-dependent thermal moment, which is due to the temperature differences of two sides of CNT films. The vibration frequency spectrums between 0.1 ˜ 0.5 Hz were obtained by the Fast Fourier Transform spectra from time domain to frequency domain, and showed a linear relationship with films thickness, which is in accordance with theoretical model of thermal induced vibration.

Li, Junying; Zhu, Yong; Wang, Xin; Wang, Ning; Zhang, Jie

2014-07-01

62

Neural-Net Processing of Characteristic Patterns From Electronic Holograms of Vibrating Blades  

NASA Technical Reports Server (NTRS)

Finite-element-model-trained artificial neural networks can be used to process efficiently the characteristic patterns or mode shapes from electronic holograms of vibrating blades. The models used for routine design may not yet be sufficiently accurate for this application. This document discusses the creation of characteristic patterns; compares model generated and experimental characteristic patterns; and discusses the neural networks that transform the characteristic patterns into strain or damage information. The current potential to adapt electronic holography to spin rigs, wind tunnels and engines provides an incentive to have accurate finite element models lor training neural networks.

Decker, Arthur J.

1999-01-01

63

The application of transfer functions in the prediction of structural response to blast induced ground vibration  

SciTech Connect

This paper outlines the theory behind transfer functions and illustrates their application in the prediction of structural response to blast induced ground vibration. The ability to predict the response of a structure to a recorded ground vibration is desirable for a number of reasons: structural or cosmetic damage often occurs, or is alleged to have occurred, away from the location at which vibration has been monitored, and humans or sensitive equipment likely to be affected by vibration are also often some distance from the monitoring location. Existing techniques used for structural response prediction include: (1) PPV ratio/amplification -- This approach is overly simplistic and only predicts the PPV and not the whole vibration response, (2) Lumped Mass Models -- These techniques assume structures act as lumped mass systems and also require a good deal of expertise to produce the full vibration response. The technique of transfer functions overcomes these problems by measuring the actual response of each structural monitoring point relative to a fixed location outside of the structure. The application of this technique to structural response prediction is illustrated with three case studies associated with vibrations from surface mine blasting: A simple shaking table model; soil/foundation response; and typical U.K. domestic house. These case studies are used to illustrate how transfer functions are calculated and their limitations in use by comparing actual and predicted responses.

Farnfield, R.A. [Univ. of Leeds (United Kingdom). Dept. of Mining and Mineral Engineering

1994-12-31

64

Experimental studies of subjective response to road traffic-induced building vibration.  

PubMed

The road traffic-induced building vibration was recorded continuously for 24 hr in three orthogonal axes outside and inside the building. Several alternative objective methods of quantifying the severity of exposures to whole-body road traffic-induced building vibration are used. The relationship between the results of all objective evaluation methods of vibration-induced by road traffic and the subjective responses to building vibration are compared. It was conducted that the ISO 2631-2 z-axis frequency weighting combined with a measure of vibration dose value (VDV = [integral of a4(t) dt)]1/4 may use a practicable objective evaluation procedure in buildings than L10 percentile vibration levels. It was also cleared that the L10 percentile vibration levels at the ground boundary of the regulation law of Japan Environmental Agency must be low levels. PMID:9583307

Maeda, S; Morioka, M; Yonekawa, Y; Kanada, K; Takahashi, Y

1998-04-01

65

Piezoelectric Instruments of High Natural Frequency Vibration Characteristics and Protection Against Interference by Mass Forces  

NASA Technical Reports Server (NTRS)

The exploration of the processes accompanying engine combustion demands quick-responding pressure-recording instruments, among which the piezoelectric type has found widespread use because of its especially propitious properties as vibration-recording instruments for high frequencies. Lacking appropriate test methods, the potential errors of piezoelectric recorders in dynamic measurements could only be estimated up to now. In the present report a test method is described by means of which the resonance curves of the piezoelectric pickup can be determined; hence an instrumental appraisal of the vibration characteristics of piezoelectric recorders is obtainable.

Gohlka, Werner

1943-01-01

66

Free vibration and dynamic response analysis of spinning structures  

NASA Technical Reports Server (NTRS)

The proposed effort involved development of numerical procedures for efficient solution of free vibration problems of spinning structures. An eigenproblem solution procedure, based on a Lanczos method employing complex arithmetic, was successfully developed. This task involved formulation of the numerical procedure, FORTRAN coding of the algorithm, checking and debugging of software, and implementation of the routine in the STARS program. A graphics package for the E/S PS 300 as well as for the Tektronix terminals was successfully generated and consists of the following special capabilities: (1) a dynamic response plot for the stresses and displacements as functions of time; and (2) a menu driven command module enabling input of data on an interactive basis. Finally, the STARS analysis capability was further improved by implementing the dynamic response analysis package that provides information on nodal deformations and element stresses as a function of time. A number of test cases were run utilizing the currently developed algorithm implemented in the STARS program and such results indicate that the newly generated solution technique is significantly more efficient than other existing similar procedures.

1986-01-01

67

Experimental investigation of the vibration characteristics of a model of an asymmetric multielement space shuttle  

NASA Technical Reports Server (NTRS)

Vibration investigations of a model of the asymmetric multielement space shuttle were made. The influence on overall motions of local deformation in the vicinity of element interfaces, high modal density, low structural damping, and high responsiveness in the crew cabin are included in the findings. Mode frequencies generally increase with decreasing propellant masses and staging of elements.

Blanchard, U. J.

1977-01-01

68

Vibration characteristics of Ni-Ti pseudo-elastic wire inter-weaved fabric composites  

NASA Astrophysics Data System (ADS)

This paper presents a study on the vibration characteristics of Ni-Ti wire inter-weaved glass fabric/epoxy composites. The Ni-Ti pseudo-elastic wires were used as warp yarns and embedded in the fabric preforms with various weaving methods. Dynamic Mechanical Analyzer (DMA) and vibration test technique were used to reveal the dynamical behaviors of specimens in different frequencies of vibration. The storage modulus E', the loss tan?, the natural frequency f and damping ratio ? were examined. The energy dissipation behaviors of the Ni-Ti pseudo-elastic wire, the geometry of textile fabric was also studied. The effect of weaving method on the vibration behavior in Shape Memory Alloy (SMA) based textile composites was considered. The results showed that: (I) the energy dissipation capacity of the wire could be significantly improved by increasing the tensile strain and speed, but slightly affected by loading frequency; (II) the woven of few Ni-Ti warps caused the increase of the storage modulus and the change of the loss tan?. In the buckling vibration, the damping effects of Ni-Ti pseudo-elastic wires vary with the woven structures. The compact woven structure with proper Ni-Ti warp architectures would receive a small amplitude and good damping.

Xu, Lei; Wang, Rui; Yang, Qiuhong; Dong, Li

2009-07-01

69

Vibration behavior and response to an accidental collision of SFT prototype in Qiandao Lake (China)  

Microsoft Academic Search

This article presents free vibration analysis of the submerged floating tunnel (SFT) prototype, which has been designed to be built in Qiandao Lake (China). As an approximation the supporting effect of the tethers is omitted in the calculation of beam-like bending vibrations. As a case study, the response of the SFT prototype to an accidental collision by an object like

Shuangyin Zhang; Lei Wang; Youshi Hong

2010-01-01

70

Neuromuscular response of the trunk to inertial based sudden perturbations following whole body vibration exposure.  

PubMed

The effects of whole body vibration exposure on the neuromuscular responses following inertial-based trunk perturbations were examined. Kinematic and surface EMG (sEMG) data were collected while subjects were securely seated on a robotic platform. Participants were either exposed to 10min of vibration or not, which was followed by sudden inertial trunk perturbations with and without timing and direction knowledge. Amplitude of sEMG was analyzed for data collected during the vibration protocol, whereas the onset of sEMG activity and lumbar spine angle were analyzed for the perturbation protocol. Data from the vibration protocol did not show a difference in amplitude of sEMG for participants exposed to vibration and those not. The perturbation protocol data showed that those not exposed to vibration had a 14% faster muscle onset, despite data showing no difference in fatigue level. PMID:25241645

MacIntyre, Danielle; Cort, Joel A

2014-12-01

71

Flight and Analytical Methods for Determining the Coupled Vibration Response of Tandem Helicopters  

NASA Technical Reports Server (NTRS)

Chapter one presents a discussion of flight-test and analysis methods for some selected helicopter vibration studies. The use of a mechanical shaker in flight to determine the structural response is reported. A method for the analytical determination of the natural coupled frequencies and mode shapes of vibrations in the vertical plane of tandem helicopters is presented in Chapter two. The coupled mode shapes and frequencies are then used to calculate the response of the helicopter to applied oscillating forces.

Yeates, John E , Jr; Brooks, George W; Houbolt, John C

1957-01-01

72

Responses of the frog primary vestibular afferents to direct vibration of the semicircular canal  

NASA Technical Reports Server (NTRS)

Responses of primary afferents (PA) of lateral semicircular canal to sinusoidal vibration of the canal wall within the range 0.05-200 Hz (mean amplitudes 5-15 microns) in immobilized frogs were studied. Dynamic characteristics (gain, phase) of relative linear velocity of the vibrator (micron X/s) were examined. At 0.2 Hz, the gain was 5.35 + or - 3.19 imp X/s /micron X/s (mean; S.D.; n=14) and linearly decreased if the frequency rose. Phase lag of relative velocity at 0.05 Hz was 49.8 deg + or - 16.5 deg (n=13) and at 1 Hz 97 deg + or - 9.4 deg (n=22). At 100 Hz phase lag was about 240 deg. Three groups of PA are described: wide range PA reacting in the range from 0.05 up to 60-180 Hz; high frequency PA responding in the range from 20-40 up to 100-150 Hz; and low frequency PA responding in the range from 0.05 up to 2-20 Hz.

Orlov, I. V.

1980-01-01

73

Nonlinear subjective and dynamic responses of seated subjects exposed to horizontal whole-body vibration  

NASA Astrophysics Data System (ADS)

The effect of the magnitude of fore-and-aft and lateral vibration on the subjective and mechanical responses of seated subjects has been investigated experimentally using simultaneous measurements of relative discomfort and apparent mass. Twelve male subjects were exposed to sinusoidal vibration at nine frequencies (between 1.6 and 10 Hz) at four magnitudes (in the range 0.125-1.0 m s -2 r.m.s.) in both horizontal directions (fore-and-aft and lateral). The method of magnitude estimation was used to estimate discomfort relative to that caused by a 4 Hz reference vibration in the same axis. The apparent mass was calculated from the acceleration and the applied force so as to quantify the mechanical response of the body. With each direction of excitation, the apparent mass was normalised by dividing it by the apparent mass obtained at 4 Hz, so that the mechanical responses could be compared with the subjective responses. The relative discomfort and the normalised apparent mass were similarly affected by the frequency and magnitude of vibration, with significant correlations between the relative discomfort and the normalised apparent mass. The results indicate that the discomfort caused by horizontal whole-body vibration is associated with the apparent mass in a frequency range where motion of the whole body is dominant. In this frequency range, the nonlinear subjective responses may be attributed, at least in part, to the nonlinear dynamic responses to horizontal whole-body vibration.

Subashi, G. H. M. J.; Nawayseh, N.; Matsumoto, Y.; Griffin, M. J.

2009-03-01

74

Neurocognitive responses to a single session of static squats with whole body vibration.  

PubMed

Amonette, WE, Boyle, M, Psarakis, MB, Barker, J, Dupler, TL, and Ott, SD. Neurocognitive responses to a single session of static squats with whole body vibration. J Strength Cond Res 29(1): 96-100, 2015-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. PMID:25536489

Amonette, William E; Boyle, Mandy; Psarakis, Maria B; Barker, Jennifer; Dupler, Terry L; Ott, Summer D

2015-01-01

75

Dose-response patterns for vibration-induced white finger  

PubMed Central

Aims: To investigate alternative relations between cumulative exposures to hand-transmitted vibration (taking account of vibration magnitude, lifetime exposure duration, and frequency of vibration) and the development of white finger (Raynaud's phenomenon). Methods: Three previous studies have been combined to provide a group of 1557 users of powered vibratory tools in seven occupational subgroups: stone grinders, stone carvers, quarry drillers, dockyard caulkers, dockyard boilermakers, dockyard painters, and forest workers. The estimated total operating duration in hours was thus obtained for each subject, for each tool, and for all tools combined. From the vibration magnitudes and exposure durations, seven alternative measurements of cumulative exposure were calculated for each subject, using expressions of the form: dose = ?amiti, where ai is the acceleration magnitude on tool i, ti is the lifetime exposure duration for tool i, and m = 0, 1, 2, or 4. Results: For all seven alternative dose measures, an increase in dose was associated with a significant increase in the occurrence of vibration-induced white finger, after adjustment for age and smoking. However, dose measures with high powers of acceleration (m > 1) faired less well than measures in which the weighted or unweighted acceleration, and lifetime exposure duration, were given equal weight (m = 1). Dose determined solely by the lifetime exposure duration (without consideration of the vibration magnitude) gave better predictions than measures with m greater than unity. All measures of dose calculated from the unweighted acceleration gave better predictions than the equivalent dose measures using acceleration frequency-weighted according to current standards. Conclusions: Since the total duration of exposure does not discriminate between exposures accumulated over the day and those accumulated over years, a linear relation between vibration magnitude and exposure duration seems appropriate for predicting the occurrence of vibration-induced white finger. Poorer predictions were obtained when the currently recommended frequency weighting was employed than when accelerations at all frequencies were given equal weight. Findings suggest that improvements are possible to both the frequency weighting and the time dependency used to predict the development of vibration-induced white finger in current standards. PMID:12499452

Griffin, M; Bovenzi, M; Nelson, C

2003-01-01

76

Crack Response to Blast Vibrations and Moisture Induced Volumetric Changes in Foundation Soils  

E-print Network

Crack Response to Blast Vibrations and Moisture Induced Volumetric Changes in Foundation Soils By C, Evanston, IL. Abstract In this paper vibratory crack response is compared to that produced by volumetric compared vibratory responses of cracks to atmospheric effects such as those produced by the passage

77

Axial vibration characteristics of a cylindrical, radially polarized piezoelectric transducer with different electrode patterns.  

PubMed

A circular cylindrical piezoelectric transducer with radial polarization is proposed. The axial vibration characteristics of the transducer are studied by three different methods: analytical calculation, FEM simulation and experiment. The symmetric and asymmetric excitation conditions are discussed in the Haskins and Walsh model. For the resonance frequencies of the transducer, the results from the above three methods coincide well with each other. For the vibration amplitude, there are some deviations between the FEM simulation and measurement results; some possible reasons for this are discussed. The influence of the electrode patterns on the excitation modes are also investigated in detail. Based on the study described in this paper, the research methodology for a cylindrical piezoelectric transducer is clarified. PMID:19818980

Sun, Dongming; Wang, Sheng; Hata, Seiichi; Shimokohbe, Akira

2010-03-01

78

Vibration manual  

NASA Technical Reports Server (NTRS)

Guidelines of the methods and applications used in vibration technology at the MSFC are presented. The purpose of the guidelines is to provide a practical tool for coordination and understanding between industry and government groups concerned with vibration of systems and equipments. Topics covered include measuring, reducing, analyzing, and methods for obtaining simulated environments and formulating vibration specifications. Methods for vibration and shock testing, theoretical aspects of data processing, vibration response analysis, and techniques of designing for vibration are also presented.

Green, C.

1971-01-01

79

ADAPTIVE RESPONSES OF HUMAN SKELETAL MUSCLE TO VIBRATION EXPOSURE  

Microsoft Academic Search

Summary The aim of this study was to investigate the effects of whole-body vibrations (WBV) on the mechanical behaviour of human skeletal muscle. For this purpose, six female volleyball players at national level were recruited voluntarily. They were tested with maximal dynamic leg press exercise on a slide machine with extra loads of 70, 90, 110 and 130 kg. After

C. Bosco; R. Colli; E. Introini; M. Cardinale; M. Iacovelli; A. Madella; J. Tihanyi; A. Viru

1999-01-01

80

Vibrational characteristics of diethyltoluenediamines (DETDA) functionalized carbon nanotubes using molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

Functionalization of carbon nanotubes (CNTs) can be viewed as an important process by which the dispersion and solubility of CNTs in the matrices of nanocomposites are improved. Covalent functionalization can affect the mechanical behavior of CNTs. In this paper, the vibrational behavior of diethyltoluenediamines (DETDA) functionalized CNTs is investigated utilizing molecular dynamics simulations in canonical ensemble at room temperature. The models of simulations are divided into two categories of functionalized CNTs with regular and random distributions of DETDA polymers. The results demonstrate that natural frequency of functionalized CNTs is lower than that of pristine ones. Also, it is observed that buckling phenomenon occurs during vibration for functionalized CNTs with regular distribution of polymers. It is further observed that polymer mass and van der Waals (vdW) forces are responsible for frequency changes in functionalized CNTs with random and regular distribution patterns of CNTs, respectively.

Ajori, S.; Ansari, R.

2015-02-01

81

Vibration characteristics of a large wind turbine tower on non-rigid foundations  

NASA Technical Reports Server (NTRS)

Vibration characteristics of the Mod-OA wind turbine supported by nonrigid foundations were investigated for a range of soil rigidities. The study shows that the influence of foundation rotation on the fundamental frequency of the wind turbine is quite significant for cohesive soils or loose sand. The reduction in natural frequency can be greater than 20 percent. However, for a foundation resting on well graded, dense granular materials or bedrock, such effect is small and the foundation can be treated as a fixed base.

Yee, S. T.; Cang, T. Y. P.; Scavuzzo, R. J.; Timmerman, D. H.; Fenton, J. W.

1977-01-01

82

Lunar seismic profiling experiment. [Apollo 17 flight measurements of lunar surface vibrations to determine subsurface characteristics  

NASA Technical Reports Server (NTRS)

The Apollo 17 lunar seismic profiling experiment was conducted to record the vibrations of the lunar surface as induced by explosive charges, the thrust of the lunar module ascent engine, and the crash of the lunar module ascent stage. Analysis of the data obtained made it possible to determine the internal characteristics of the lunar crust to a depth of several kilometers. The test equipment used in the experiment is described. Maps showing the location of the geophones and the deployed explosive packages are provided. Samples of the seismic signals recorded by the lunar seismic profiling experiment geophones are included.

Kovach, R. L.; Watkins, J. S.; Talwani, P.

1973-01-01

83

A numerical method for determining the natural vibration characteristics of rotating nonuniform cantilever blades  

NASA Technical Reports Server (NTRS)

A method is presented for determining the free vibration characteristics of a rotating blade having nonuniform spanwise properties and cantilever boundary conditions. The equations which govern the coupled flapwise, chordwise, and torsional motion of such a blade are solved using an integrating matrix method. By expressing the equations of motion and matrix notation, utilizing the integrating matrix as an operator, and applying the boundary conditions, the equations are formulated into an eigenvalue problem whose solutions may be determined by conventional methods. Computer results are compared with experimental data.

White, W. F., Jr.; Malatino, R. E.

1975-01-01

84

Vibration characteristics analysis of a 20-high Sendzimir mill with localized defect on the working roller  

NASA Astrophysics Data System (ADS)

The working roller associating with local defect of the twenty-high roll mill not only significantly affects the mill performance, but also reduces surface quality of the strip steel. In this paper, the roll mill model with local defect on the working roller is established. The dynamic rolling process is simulated using the Finite Element Analysis. Effects of the local defect on the vibration characteristics of the roll mill and the surface quality of the strip steel are presented. The calculated results are validated using experimental data.

He, R. Y.; Liu, J.; Yuan, Y. L.; Shao, Y. M.; Xiao, H. F.

2012-05-01

85

Study on vibration characteristics of the shaft system for a dredging pump based on FEM  

NASA Astrophysics Data System (ADS)

The dynamic characteristics of the shaft system for a dredging pump were studied with the Finite Element Method (FEM) by SAMCEF ROTOR. At first, the influence of the fluid-solid coupling interaction of mud water and impeller, water sealing and pump shaft on the lateral critical speeds were analyzed. The results indicated that the mud water must be taken into consideration, while the water sealing need not to. Then the effects of radial and thrust rolling bearings on the lateral critical speeds were discussed, which shows that the radial bearing close to the impeller has greatest impact on the 1st order critical speed. At last, the upper and lower limits of the critical speeds of lateral, axial and torsional vibration were calculated. The rated speed of the dredging pump was far less than the predicted critical speed, which can ensure the safe operation of the unit. Each vibration mode is also shown in this paper. This dynamic analysis method offers some reference value on the research of vibration and stability of the shaft system in dredging pump.

Zhai, L. M.; Qin, L.; Liu, C. Y.; Liu, X.; He, L. Y.; He, Y.; Wang, Z. W.

2012-11-01

86

The use of statistical characteristics of reducer vibrations as diagnostic symptoms  

NASA Technical Reports Server (NTRS)

The results of a statistical analysis of the vibrations of the experimental RS-1 reducer stand, with a spiral-gear transmission, operating on a closed circuit, are presented. The analysis was carried out on the Minsk-2 and Minsk-32 digital computers, with two-channel analog-digital converter, built in the Institute of the Science of Mechanics. Two-dimensional distribution patterns, conditional dispersions and dispersion ratios were calculated. The octave-band-filtered first harmonics of the tooth frequency f sub z of the vibrations at two different measurement points were considered as the components of the vibration process to be analyzed. The regression lines, corresponding to different values of the loading torque, are presented. Since it was not the gear drive parameters which were determined by diagnostic methods, but the characteristics most sensitive to change in state of the object of the investigation, the loading torque, which is the simplest and most accessible for measurement, was chosen as the condition parameter.

Balitskiy, F. Y.; Genkin, M. D.; Ivanova, M. A.; Sokolova, A. G.

1973-01-01

87

Subjective response to seated fore-and-aft direction whole-body vibration  

Microsoft Academic Search

Subjective response to seated, fore-and-aft direction, whole-body vibration of the type experienced in automobiles was investigated. Fore-and-aft acceleration was measured at the seat guide of a small automobile when driving over two representative road surfaces, and was replicated in a laboratory setting using a whole-body vibration test rig and rigid seat. A single 15s section of each of the two

T. M. Hacaambwa; J. Giacomin

2007-01-01

88

Response of a flexible filament in a flowing soap film subject to a forced vibration  

NASA Astrophysics Data System (ADS)

The interactions between flexible plates and fluids are important physical phenomena. A flag in wind is one of the most simplified and classical models for studying the problem. In this paper, we investigated the response of a flag in flow with an externally forced vibration by using flexible filaments and soap film. Experiments show that for a filament that is either in oscillation or stationary, the external forced vibration leads to its oscillation. A synchronization phenomenon occurs in the experiments. A small perturbation leads to a large response of flapping amplitude in response. The insight provided here is helpful to the applications in the flow control, energy harvesting, and bionic propulsion areas.

Jia, Laibing; Xiao, Qing; Wu, Haijun; Wu, Yanfeng; Yin, Xiezhen

2015-01-01

89

Forced response approach of a parametric vibration with a trigonometric series  

NASA Astrophysics Data System (ADS)

A forced vibration problem with parametric stiffness is modeled by feedback structure in this manuscript, and the forced response is expressed as a special trigonometric series. The forced response of this problem is determined by algebraic equation. By applying harmonic balance and limitation operation, all coefficients of the harmonic components in the forced response solution are fully approached. The investigation result shows that the new approach has an advantage in the computational time and accuracy, and it is very significant for the theoretical research and engineering application in dealing with the problem of forced parametric vibration.

Huang, Dishan

2015-02-01

90

Comparison of Subjective Responses to Vibration and Shock with Standard Analysis Methods and Absorbed Power  

NASA Astrophysics Data System (ADS)

Evaluation of human exposure whole-body vibration (WBV) and shock can be carried out in a variety of ways. The most commonly used standards for predicting discomfort from WBV are BS6841 (1987) and ISO2631-1 (1997) which offer different frequency weightings (Wband Wk) and three methods of assessment: vibration dose value (VDV), estimated VDV (eVDV) and maximum transient vibration value (MTVV). Previous studies have also used DRI and absorbed power for assessments of shock and WBV. This paper reports a laboratory study in which 24 human subjects were exposed to 15 vertical vibration stimuli comprising of random vibration, repeated shocks and combinations of random vibration and shocks at 0·5, 1·0 and 1·5 m/s2r.m.s. Subjects rated the discomfort from the vibration on a numerical scale after each exposure. Acquired acceleration signals were analyzed using VDV, r.m.s. and MTVV for unweighted,Wb , Wkand DRI weighted signals. Acceleration and force were combined to give a measure of absorbed power. Subjective responses were correlated to vibration magnitude for the 13 analysis types. VDV was the best standard method of assessment; MTVV was the worst. Wband Wkfrequency weightings showed slightly greater correlations between vibration magnitude and discomfort than DRI weighted or unweighted signals. For VDV, there were no significant differences between the correlations obtained using any frequency weighting. For assessment of all stimuli types together, absorbed power gave higher correlations with subjective discomfort than acceleration-based methods. It is concluded that the methods described in ISO2631-1 should be clarified and simplified. Due to the difficulty in measuring absorbed power in the field, methods proposed in BS6841 are recommended as the most appropriate for assessment of discomfort from continuous vibration or repeated shocks.

MANSFIELD, N. J.; HOLMLUND, P.; LUNDSTRÖM, R.

2000-02-01

91

Spectral response characteristics of photovoltaic materials  

NASA Astrophysics Data System (ADS)

The most efficient solar modules use multiple materials of slightly varying composition and electronic characteristics to convert different bandwidths of the solar spectrum into usable electricity. Cells made in this fashion generally require very expensive, high precision equipment leading to a high cost of the modules. It has been suggested that an optical system be used to disperse the sunlight into its constituent wavelengths (see Conte et. al. (1989)[22]) with different materials strategically placed under the appropriate bandwidth of light to produce higher efficiency, low cost modules. The proper selection and placement of materials requires detailed knowledge of the response of various materials to different wavelengths of light. Solid State Theory calculates this response through complicated mathematical models describing the band structure of the materials and the density of states for charge carriers. The research described herein defines this response through experiment. The experiment designed for this research examines the response of commercially available photovoltaic cells of various materials. Concentrated sunlight is passed through filters with known transmittance to illuminate a photovoltaic cell. The incident irradiance, and thereby the incident power, on the cell is recorded as well as the power output by the cell. These two powers are compared for each filter, and the results are plotted as efficiency vs. wavelength providing an experimental check for theoretical calculations. This experiment can be performed on any photovoltaic material of interest to determine optimal material selection and placement under the dispersed sunlight for a solar module. The combination of the methods developed in this research and the optics described in the paper by Conte et. al. can be used to produce an inexpensive, high efficiency solar module.

Hanselman, Daniel L.

92

The vibration characteristics of a coupled helicopter rotor-fuselage by a finite element analysis  

NASA Technical Reports Server (NTRS)

The dynamic coupling between the rotor system and the fuselage of a simplified helicopter model in hover was analytically investigated. Mass, aerodynamic damping, and elastic and centrifugal stiffness matrices are presented for the analytical model; the model is based on a beam finite element, with polynomial mass and stiffness distributions for both the rotor and fuselage representations. For this analytical model, only symmetric fuselage and collective blade degrees of freedom are treated. Real and complex eigen-analyses are carried out to obtain coupled rotor-fuselage natural modes and frequencies as a function of rotor speed. Vibration response results are obtained for the coupled system subjected to a radially uniform, harmonic blade loading. The coupled response results are compared with response results from an uncoupled analysis in which hub loads for an isolated rotor system subjected to the same sinusoidal blade loading as the coupled system are applied to a free-free fuselage.

Rutkowski, M. J.

1983-01-01

93

Subjective response to combined noise and vibration during flight of a large twin-jet airplane  

NASA Technical Reports Server (NTRS)

A NASA twin-jet airplane was used to obtain controlled noise and vibration environments during flight while obtaining subjective responses from 13 passenger-subjects (6 females and 7 males). Subjective ratings of overall comfort, comfort when considering only vibration, and comfort when considering only noise were obtained during times of different vibration and noise environments. Passenger-subjects were able to distinguish and rate noise better than vibration. In addition, there was a statistically significant difference in ratings of ride comfort due to both sex type and flight experience. Males rated flying discomfort much more severely than females when rating the overall ride and the ride when considering only the noise environment. Experienced passengers also rated the overall ride to be more uncomfortable than inexperienced passengers.

Clevenson, S. A.

1976-01-01

94

Adaptive responses of human skeletal muscle to vibration exposure.  

PubMed

The aim of this study was to investigate the effects of whole-body vibrations (WBV) on the mechanical behaviour of human skeletal muscle. For this purpose, six female volleyball players at national level were recruited voluntarily. They were tested with maximal dynamic leg press exercise on a slide machine with extra loads of 70, 90, 110 and 130 kg. After the testing, one leg was randomly assigned to the control treatment (C) and the other to the experimental treatment (E) consisting of vibrations. The subjects were then retested at the end of the treatment using the leg press. Results showed remarkable and statistically significant enhancement of the experimental treatment in average velocity (AV), average force (AF) and average power (AP) (P < 0.05-0.005). Consequently, the velocity-force and power-force relationship shifted to the right after the treatment. In conclusion, it was affirmed that the enhancement could be caused by neural factors, as athletes were well accustomed to the leg press exercise and the learning effect was minimized. PMID:10200901

Bosco, C; Colli, R; Introini, E; Cardinale, M; Tsarpela, O; Madella, A; Tihanyi, J; Viru, A

1999-03-01

95

Modal Analysis and Study of the Vibration Characteristics of the Thermoelectric Modules of Vehicle Exhaust Power-Generation Systems  

NASA Astrophysics Data System (ADS)

Thermoelectric (TE) materials and modules are important components of vehicle exhaust power-generation systems. The road and the engine, the main sources of vibration of TE modules, have substantial effects on the vibration characteristics of TE modules. In this work, modal analysis and the vibration characteristics of TE modules were investigated in detail. On the basis of the TE modules and their service environment, simulations for modal analysis were performed by use of the finite-element method, and the natural frequencies and mode shapes of the TE modules were obtained. The numerical results were used to compare the natural frequencies of TE modules under different contact stiffness with the range of excitation frequencies of road and engine, in an attempt to prevent severe resonance. The effects on the vibration characteristics of geometric dimensions, service temperature, and thermal stress of the TE modules are also discussed in detail. The results reveal the vibration characteristics of the TE modules and provide theoretical guidance for structure optimization in the design of vehicle exhaust power-generation systems.

Chen, Gang; Mu, Yu; Zhai, Pengcheng; Yu, Rui; Li, Guodong; Zhang, Qingjie

2014-06-01

96

Intelligent control for braking-induced longitudinal vibration responses of floating-type railway bridges  

NASA Astrophysics Data System (ADS)

This paper presents an intelligent control method and its engineering application in the control of braking-induced longitudinal vibration of floating-type railway bridges. Equations of motion for the controlled floating-type railway bridges have been established based on the analysis of the longitudinal vibration responses of floating-type railway bridges to train braking and axle-loads of moving trains. For engineering applications of the developed theory, a full-scale 500 kN smart magnetorheologic (MR) damper has been designed, fabricated and used to carry out experiments on the intelligent control of braking-induced longitudinal vibration. The procedure for using the developed intelligent method in conjunction with the full-scale 500 kN MR dampers has been proposed and used to control the longitudinal vibration responses of the deck of floating-type railway bridges induced by train braking and axle-loads of moving trains. This procedure has been applied to the longitudinal vibration control of the Tian Xingzhou highway and railway cable-stayed bridge over the Yangtze River in China. The simulated results have shown that the intelligent control system using the smart MR dampers can effectively control the longitudinal response of the floating-type railway bridge under excitations of braking and axle-loads of moving trains.

Qu, Wei-Lian; Qin, Shun-Quan; Tu, Jian-Weia; Liu, Jia; Zhou, Qiang; Cheng, Haibin; Pi, Yong-Lin

2009-12-01

97

Machinery vibration: Origins, impressions and cures  

SciTech Connect

The current trend toward high performance (speed, power, flow, etc.) and low eight are causing new machinery dynamics problems. Vibration diagnostics engineering of rotor-bearing-casing systems must consider both internal and external influences to effectively predict and diagnose these problems. It is assumed that machinery vibration data are free from ambiguity, error, conform to a standard and clearly identify the physical cause(s) responsible for vibration. Rotor vibration due to internal forces are described: unbalance force characteristics; response characteristics; and rules of rotor fundamental response. Rotor vibration due to external forces include: rotating aerodynamic stall; oil whirl; oil whip; structural resonance; vane/blade passing vibration; misalignment; rotor rubbing; gear mesh vibrations; and shaft crack. These are also discussed.

Haq, I. (Bechtel Petroleum Operations, Inc., Tupman, CA (United States))

1995-01-01

98

Analysis of non-linear response of the human body to vertical whole-body vibration.  

PubMed

The human response to vibration is typically studied using linear estimators of the frequency response function, although different literature works evidenced the presence of non-linear effects in whole-body vibration response. This paper analyses the apparent mass of standing subjects using the conditioned response techniques in order to understand the causes of the non-linear behaviour. The conditioned apparent masses were derived considering models of increasing complexity. The multiple coherence function was used as a figure of merit for the comparison between the linear and the non-linear models. The apparent mass of eight male subjects was studied in six configurations (combinations of three vibration magnitudes and two postures). The contribution of the non-linear terms was negligible and was endorsed to the change of modal parameters during the test. Since the effect of the inter-subject variability was larger than that due to the increase in vibration magnitude, the biodynamic response should be more meaningfully modelled using a linear estimator with uncertainty rather than looking for a non-linear modelling. PMID:25105223

Tarabini, Marco; Solbiati, Stefano; Moschioni, Giovanni; Saggin, Bortolino; Scaccabarozzi, Diego

2014-01-01

99

A spider's biological vibration filter: micromechanical characteristics of a biomaterial surface.  

PubMed

A strain-sensing lyriform organ (HS-10) found on all of the legs of a Central American wandering spider (Cupiennius salei) detects courtship, prey and predator vibrations transmitted by the plant on which it sits. It has been suggested that the viscoelastic properties of a cuticular pad directly adjacent to the sensory organ contribute to the organ's pronounced high-pass characteristics. Here, we investigate the micromechanical properties of the cuticular pad biomaterial in search of a deeper understanding of its impact on the function of the vibration sensor. These properties are considered to be an effective adaptation for the selective detection of signals for frequencies >40 Hz. Using surface force spectroscopy mapping we determine the elastic modulus of the pad surface over a temperature range of 15-40 °C at various loading frequencies. In the glassy state, the elastic modulus was ~100 MPa, while in the rubbery state the elastic modulus decreased to 20 MPa. These data are analyzed according to the principle of time-temperature superposition to construct a master curve that relates mechanical properties, temperature and stimulus frequencies. By estimating the loss and storage moduli vs. temperature and frequency it was possible to make a direct comparison with electrophysiology experiments, and it was found that the dissipation of energy occurs within a frequency window whose position is controlled by environmental temperatures. PMID:25065547

Young, Seth L; Chyasnavichyus, Marius; Erko, Maxim; Barth, Friedrich G; Fratzl, Peter; Zlotnikov, Igor; Politi, Yael; Tsukruk, Vladimir V

2014-11-01

100

Free-vibration characteristics and correlation of a space station split-blanket solar array  

NASA Technical Reports Server (NTRS)

Two methods for studying the free-vibration characteristics of a large split-blanket solar array in a zero-g cantilevered configuration are presented. The zero-g configuration corrresponds to an on-orbit configuration of the Space Station solar array. The first method applies the equations of continuum mechanics to determine the natural frequencies of the array; the second uses the finite element method program, MSC/NASTRAN. The stiffness matrix from the NASTRAN solution was found to be erroneously grounded. The results from the two methods are compared. It is concluded that the grounding does not seriously compromise the solution to the elastic modes of the solar array. However, the correct rigid body modes need to be included to obtain the correct dynamic model.

Carney, Kelly S.; Shaker, Francis J.

1989-01-01

101

Scanning LDV for vibration measurement of filiform hairs in crickets in response to induced airflow  

NASA Astrophysics Data System (ADS)

Cercal hairs represent in cricket a wind sensitive escape system, able to detect the airflow generated from predating species. These sensors have been studied as a biomimetic concept to allow the development of MEMS for biomedical use. In particular, the behaviour of the hairs, including airflow response, resonant frequency and damping, has been investigated up to a frequency of 20 kHz. The microscopic nature of the hairs, the complex vibrations of excited hairs and the high damping of the system suggested that the use of Laser Doppler vibrometry could possibly improve the test performance. Two types of tests were performed: in the first case the hairs were indirectly excited using the signal obtained from a vibrating aluminium plate, whilst in the second case the hairs were directly excited using a white noise chirp. The results from the first experiment indicated that the hairs move in-phase with the exciting signal up to frequencies in the order of 10 kHz, responding to the vibration modes of the plate with a signal attenuation of 12 to 20 dB. The chirp experiment revealed the presence of rotational resonant modes at 6850 and 11300 Hz. No clear effect of hair length was perceivable on the vibration response of the filiform sensors. The obtained results proved promising to support the mechanical and vibration characterisation of the hairs and suggest that scanning Laser vibrometry can be used extensively on highly dampened biological materials.

Santulli, C.; Finn, T. J.; Seidel, R.; Jeronimidis, G.

2006-06-01

102

Study on Vibration Characteristics of a High-rise Building using results of Microtremor, Manpower Excitation Measurements, Earthquake Observations and Simulations of a 3D Moment-frame structure  

NASA Astrophysics Data System (ADS)

In the Tokyo metropolitan area, high-rise buildings will suffer strong ground motions in near future. In order to estimate damage of the buildings and to carry out counter measures for reducing the damage, it is necessary to know the accurate vibration characteristics of the buildings during the strong ground motions. The purpose of the paper is to investigate vibration characteristics of the Shinjuku Campus building of the 28th floors in Shinjuku, Tokyo, which is a steel structure of moment frames with143 m height. First, we constructed a 3D moment frame model and compared vibration characteristics, such as the natural periods and the corresponding mode shapes, with those obtained by microtremors measurements and manpower excitations. We obtained excellent agreements between them. Second, we compared the observed building response during earthquakes with those of the simulations; we again obtained agreements.

Hoshi, Yukio; Hisada, Yoshiaki; Yamashita, Tetsuo; Masuzawa, Yoe; Shimamura, Kenta

103

NEUROMOTOR RESPONSE TO WHOLE BODY VIBRATION TRANSMISSIBILITY IN THE HORIZONTAL DIRECTION AND ITS MATHEMATICAL MODEL  

E-print Network

NEUROMOTOR RESPONSE TO WHOLE BODY VIBRATION TRANSMISSIBILITY IN THE HORIZONTAL DIRECTION AND ITS MATHEMATICAL MODEL By Vinay Hanumanthareddygari Submitted to graduate degree program in Mechanical Engineering and the Graduate Faculty... of the University of Kansas School of Engineering in partial fulfillment of the requirements for the degree of Master of Science Committee: ______________________ Dr. Sara E. Wilson, Chairperson ______________________ Dr. Terry N. Faddis...

Hanumanthareddygari, Vinay

2010-09-02

104

Study of T53 engine vibration  

NASA Technical Reports Server (NTRS)

Vibration characteristics for overhauled T53 engines, including rejection rate, principal sources of vibration, and normal procedures taken by the overhaul center to reduce engine vibration are summarized. Analytical and experimental data were compared to determine the engine's dynamic response to unbalance forces with results showing that the engine operates through bending critical speeds. Present rigid rotor balancing techniques are incapable of compensating for the flexible rotor unbalance. A comparison of typical test cell and aircraft vibration levels disclosed significant differences in the engine's dynamic response. A probable spline shift phenomenon was uncovered and investigated. Action items to control costs and reduce vibration levels were identified from analytical and experimental studies.

Walter, T. J.

1978-01-01

105

Vibration reduction in helicopters using active control of structural response (ACSR) with improved aerodynamic modeling  

NASA Astrophysics Data System (ADS)

This dissertation describes the development of a coupled rotor/flexible fuselage aeroelastic response model including rotor/fuselage aerodynamic interactions. This model is used to investigate fuselage vibrations and their suppression using active control of structural response (ACSR). The fuselage, modeled by a three dimensional structural dynamic finite element model, is combined with a flexible, four-bladed, hingeless rotor. Each rotor blade is structurally modeled as an isotropic Euler-Bernoulli beam with coupled flap-lag-torsional dynamics assuming moderate deflections. A free wake model is incorporated into the aeroelastic response model and is validated against previous studies. Two and three dimensional sources model the fuselage aerodynamics. Direct aerodynamic influences of the rotor and wake on the fuselage are calculated by integrating pressures over the surface of the fuselage. The fuselage distorts the wake and influences the air velocities at the rotor which alters the aerodynamic loading. This produces fully coupled rotor/fuselage aerodynamic interactions. The influence of the aerodynamic refinements on vibrations is studied in detail. Results indicate that a free wake model and the inclusion of fuselage aerodynamic effects on the rotor and wake are necessary for vibration prediction at all forward speeds. The direct influence of rotor and wake aerodynamics on the fuselage plays a minor role in vibrations. Accelerations with the improved aerodynamic model are significantly greater than uniform inflow results. The influence of vertical separation between the rotor and fuselage on vibrations is also studied. An ACSR control algorithm is developed that preferentially reduces accelerations at selected airframe locations of importance. Vibration reduction studies are carried out using this improved control algorithm and a basic algorithm studied previously at UCLA. Both ACSR methods markedly reduce acceleration amplitudes with no impact on the rotor system or airworthiness of the vehicle. The improved control algorithm performs significantly better than the basic control method with equivalent power requirements.

Cribbs, Richard Clay

106

Coupled vibration response of a shaft with a breathing crack  

NASA Astrophysics Data System (ADS)

The accurate and detailed knowledge of the local flexibility which is introduced by a crack into a structure may be used in damage diagnosis. This paper investigates the variation of the local flexibility of cracked shafts under harmonic type of loadings causing tensional as well as compressional stresses around the crack faces in a periodic manner which inevitably lead to the opening and closure of the crack, i.e. the breathing mechanism. Time-dependent nonlinear finite element method (FEM) is adopted to analyze various crack sizes as well as time-dependent axial, bending and torsional types of loading. Special boundary conditions are adopted between crack faces to avoid penetration along the contact area and simultaneously permit the existence of stick or slip contact zones according to Coulomb's law. Deflection differences at the loaded edge between uncracked and cracked shaft are used for the computation of the local flexibilities. Apart from the computation of the diagonal terms of local flexibility matrix intensive emphasis is given to its off-diagonal coefficients which cause the coupling of motion between different degrees of freedom and thus may affect considerably the overall vibrational behavior of the shaft.

Giannopoulos, G. I.; Georgantzinos, S. K.; Anifantis, N. K.

2015-02-01

107

Vibration characteristics of walls and a plate glass window representative of those of a wood-frame house  

NASA Technical Reports Server (NTRS)

Mechanical excitation was used, and measurements of acceleration response, natural frequencies, and nodal patterns were performed. Results indicate that the wall sections and the complete wall did not act as a unit in responding to sinusoidal vibration inputs. Calculated frequencies of the components that account for this independent behavior of the studs and face sheets agreed resonably well with experimental frequencies. Experimental vibrations of the plate glass window agreed with the calculated behavior, and responses of the window exposed to airplane flyover noise were readily correlated with the test results.

Carden, H. D.

1979-01-01

108

Optimal placement of trailing-edge flaps for helicopter vibration reduction using response surface methods  

NASA Astrophysics Data System (ADS)

This study aims to determine optimal locations of dual trailing-edge flaps to achieve minimum hub vibration levels in a helicopter, while incurring low penalty in terms of required trailing-edge flap control power. An aeroelastic analysis based on finite elements in space and time is used in conjunction with an optimal control algorithm to determine the flap time history for vibration minimization. The reduced hub vibration levels and required flap control power (due to flap motion) are the two objectives considered in this study and the flap locations along the blade are the design variables. It is found that second order polynomial response surfaces based on the central composite design of the theory of design of experiments describe both objectives adequately. Numerical studies for a four-bladed hingeless rotor show that both objectives are more sensitive to outboard flap location compared to the inboard flap location by an order of magnitude. Optimization results show a disjoint Pareto surface between the two objectives. Two interesting design points are obtained. The first design gives 77 percent vibration reduction from baseline conditions (no flap motion) with a 7 percent increase in flap power compared to the initial design. The second design yields 70 percent reduction in hub vibration with a 27 percent reduction in flap power from the initial design.

Viswamurthy, S. R.; Ganguli, Ranjan

2007-03-01

109

White Noise Responsiveness of an AlN Piezoelectric MEMS Cantilever Vibration Energy Harvester  

NASA Astrophysics Data System (ADS)

This paper reports the design, analysis and experimental characterisation of a piezoelectric MEMS cantilever vibration energy harvester, the enhancement of its power output by adding various values of end mass, as well as assessing the responsiveness towards white noise. Devices are fabricated using a 0.5 ?m AlN on 10 ?m doped Si process. Cantilevers with 5 mm length and 2 mm width were tested at either unloaded condition (MC0: fn 577 Hz) or subjected to estimated end masses of 2 mg (MC2: fn 129 Hz) and 5 mg (MC5: fn 80 Hz). While MC0 was able to tolerate a higher drive acceleration prior to saturation (7 g with 0.7 ?W), MC5 exhibited higher peak power attainable at a lower input vibration (2.56 ?W at 3 ms?2). MC5 was also subjected to band-limited (10 Hz to 2 kHz) white noise vibration, where the power response was only a fraction of its resonant counterpart for the same input: peak instantaneous power >1 ?W was only attainable beyond 2 g of white noise, whereas single frequency resonant response only required 2.5 ms?2. Both the first resonant response and the band-limited white noise response were also compared to a numerical model, showing close agreements.

Jia, Y.; Seshia, A. A.

2014-11-01

110

The Effect of Surface Wave Propagation on Neural Responses to Vibration in Primate Glabrous Skin  

PubMed Central

Because tactile perception relies on the response of large populations of receptors distributed across the skin, we seek to characterize how a mechanical deformation of the skin at one location affects the skin at another. To this end, we introduce a novel non-contact method to characterize the surface waves produced in the skin under a variety of stimulation conditions. Specifically, we deliver vibrations to the fingertip using a vibratory actuator and measure, using a laser Doppler vibrometer, the surface waves at different distances from the locus of stimulation. First, we show that a vibration applied to the fingertip travels at least the length of the finger and that the rate at which it decays is dependent on stimulus frequency. Furthermore, the resonant frequency of the skin matches the frequency at which a subpopulation of afferents, namely Pacinian afferents, is most sensitive. We show that this skin resonance can lead to a two-fold increase in the strength of the response of a simulated afferent population. Second, the rate at which vibrations propagate across the skin is dependent on the stimulus frequency and plateaus at 7 m/s. The resulting delay in neural activation across locations does not substantially blur the temporal patterning in simulated populations of afferents for frequencies less than 200 Hz, which has important implications about how vibratory frequency is encoded in the responses of somatosensory neurons. Third, we show that, despite the dependence of decay rate and propagation speed on frequency, the waveform of a complex vibration is well preserved as it travels across the skin. Our results suggest, then, that the propagation of surface waves promotes the encoding of spectrally complex vibrations as the entire neural population is exposed to essentially the same stimulus. We also discuss the implications of our results for biomechanical models of the skin. PMID:22348055

Manfredi, Louise R.; Baker, Andrew T.; Elias, Damian O.; Dammann, John F.; Zielinski, Mark C.; Polashock, Vicky S.; Bensmaia, Sliman J.

2012-01-01

111

Multipulse polarisation selective spectroscopy of rotational and vibrational responses of molecules in a liquid  

SciTech Connect

The amplitude control of time-resolved optical responses in a liquid is theoretically analysed under nonresonant irradiation of the system by a train of femtosecond pulses with parallel and orthogonal polarisations. The control parameters, specifying the excitation scenarios, are the duration of pulses, their relative intensities, polarisation, and the delays between the pulses. It is shown that the choice of specific excitation scenarios transfers the system into a state in which only one response is detected from a set of responses of coherent intramolecular Raman active vibrational modes, coherent molecular librations and orientational rotations. (laser spectroscopy)

Nikiforov, V G [E.K.Zavoisky Physical-Technical Institute, Kazan Scientific Center, Russian Academy of Sciences, Kazan (Russian Federation)

2013-02-28

112

Damage identification and health monitoring of structural and mechanical systems from changes in their vibration characteristics: A literature review  

Microsoft Academic Search

This report contains a review of the technical literature concerning the detection, location, and characterization of structural damage via techniques that examine changes in measured structural vibration response. The report first categorizes the methods according to required measured data and analysis technique. The analysis categories include changes in modal frequencies, changes in measured mode shapes (and their derivatives), and changes

S. W. Doebling; C. R. Farrar; M. B. Prime; D. W. Shevitz

1996-01-01

113

A study of structural analysis and dynamic characteristics of a sleeve spring torsional vibration damper  

Microsoft Academic Search

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore,\\u000a it is necessary to establish preventive measures to diminish the torsional vibration. A sleeve spring damper is one such measure\\u000a to reduce the torsional vibration. In this study, the closed form equations to predict the spring constant of a sleeve spring

Beom Cheol Hwang; Chung Hwan Jeon; Won Byong Bae; Chul Kim

2010-01-01

114

Minimization of the mean square velocity response of dynamic structures using an active-passive dynamic vibration absorber.  

PubMed

An optimal design of a hybrid vibration absorber (HVA) with a displacement and a velocity feedback for minimizing the velocity response of the structure based on the H(2) optimization criterion is proposed. The objective of the optimal design is to reduce the total vibration energy of the vibrating structure under wideband excitation, i.e., the total area under the velocity response spectrum is minimized in this criterion. One of the inherent limitations of the traditional passive vibration absorber is that its vibration suppression is low if the mass ratio between the absorber mass and the mass of the primary structure is low. The active element of the proposed HVA helps further reduce the vibration of the controlled structure, and it can provide very good vibration absorption performance even at a low mass ratio. Both the passive and active elements are optimized together for the minimization of the mean square velocity of the primary system as well as the active force required in the HVA. The proposed HVA was tested on single degree-of-freedom (SDOF) and continuous vibrating structures and compared to the traditional passive vibration absorber. PMID:22779469

Cheung, Y L; Wong, W O; Cheng, L

2012-07-01

115

Psychophysical relationships characterizing human response to whole-body sinusoidal vertical vibration  

NASA Technical Reports Server (NTRS)

An experimental investigation determined that the psychophysical relationships between subjective discomfort evaluations to vibratory stimuli and subjective evaluations of the intensity of vibratory stimuli can be expressed in a linear fashion. Furthermore, significant differences were found to exist between discomfort and intensity subjective response for several but not all discrete frequencies investigated. The implication of these results is that ride quality criteria based upon subjective evaluation of vibration intensity should be applied cautiously in the development of criteria for human comfort.

Leatherwood, J. D.; Dempsey, T. K.

1976-01-01

116

Direct damage diagnosis of structural component using vibration response  

NASA Astrophysics Data System (ADS)

This study proposes a semi-model-based method for detecting, locating and quantifying damages that may exist in a structure after a seismic event. The basic concept of the proposed method is to design a monitor for each structural component that needs to be monitored. The monitor is designed based on a residual generator technique and is sensitive only to the damage of the targeted component. The input signals to this monitor are the structural dynamic responses and the excitation. The monitor produces zero or close to zero output when there is no damage in the corresponding component. It produces an obvious nonzero output when the condition of that component has changed. The occurrence and the location of the structural damage can be determined by the display of nonzero output. Furthermore, the severity of the damage can be assessed by using a time-domain system identification technique on the input-output data of the monitor. The proposed method requires some prior knowledge about the structure being monitored. However, as the method can be used to assess and update the structural property of the components, precise modeling of the structure prior to the implementation of the technique is not necessary. A three-story lumped mass shear beam model under a seismic excitation was chosen as a numerical example. Results show that the proposed method can accurately detect, locate and quantify structural damages.

Ma, Tian-Wei; Yang, Henry T.; Chang, Chih-Chen

2004-07-01

117

Numerical study on the vibration characteristics of automobile brake disk and pad  

Microsoft Academic Search

Based on the review of researches on the vibration and noise related to automobile brake, a four degrees of freedom nonlinear dynamics model of brake disk and pads is established, the stability of vibration system at the equilibrium points is analyzed. Finally the numerical method is taken to study the impacts of brake pressure, shape parameter and the brake disk's

Xianjie Meng; Guangqiang Wu; Lin He

2009-01-01

118

The identification of the inertial characteristics of an internal combustion engine through steady state vibration measurements  

Microsoft Academic Search

Recent product design and development efforts have been focused on improving engine-mounting technology to achieve better vibration isolation, smooth vehicle movement, and noise reduction. Understanding the origins and parametric dependencies of the vehicle engine noise and vibration is the first step in any abatement or reduction strategy. ^ The decoupling and coupling of engine modes from the engine's reciprocating inertia

Rod G Hadi

2002-01-01

119

Vibration and Operational Characteristics of a Composite-Steel (Hybrid) Gear  

NASA Technical Reports Server (NTRS)

Hybrid gears have been tested consisting of metallic gear teeth and shafting connected by composite web. Both free vibration and dynamic operation tests were completed at the NASA Glenn Spur Gear Fatigue Test Facility, comparing these hybrid gears to their steel counterparts. The free vibration tests indicated that the natural frequency of the hybrid gear was approximately 800 Hz lower than the steel test gear. The dynamic vibration tests were conducted at five different rotational speeds and three levels of torque in a four square test configuration. The hybrid gears were tested both as fabricated (machined, composite layup, then composite cure) and after regrinding the gear teeth to the required aerospace tolerance. The dynamic vibration tests indicated that the level of vibration for either type of gearing was sensitive to the level of load and rotational speed.

Handschuh, Robert F.; LaBerge, Kelsen E.; DeLuca, Samuel; Pelagalli, Ryan

2014-01-01

120

Hormonal and Neuromuscular Responses to Mechanical Vibration Applied to Upper Extremity Muscles  

PubMed Central

Objective To investigate the acute residual hormonal and neuromuscular responses exhibited following a single session of mechanical vibration applied to the upper extremities among different acceleration loads. Methods Thirty male students were randomly assigned to a high vibration group (HVG), a low vibration group (LVG), or a control group (CG). A randomized double-blind, controlled-parallel study design was employed. The measurements and interventions were performed at the Laboratory of Biomechanics of the University of L'Aquila. The HVG and LVG participants were exposed to a series of 20 trials ×10 s of synchronous whole-body vibration (WBV) with a 10-s pause between each trial and a 4-min pause after the first 10 trials. The CG participants assumed an isometric push-up position without WBV. The outcome measures were growth hormone (GH), testosterone, maximal voluntary isometric contraction during bench-press, maximal voluntary isometric contraction during handgrip, and electromyography root-mean-square (EMGrms) muscle activity (pectoralis major [PM], triceps brachii [TB], anterior deltoid [DE], and flexor carpi radialis [FCR]). Results The GH increased significantly over time only in the HVG (P?=?0.003). Additionally, the testosterone levels changed significantly over time in the LVG (P?=?0.011) and the HVG (P?=?0.001). MVC during bench press decreased significantly in the LVG (P?=?0.001) and the HVG (P?=?0.002). In the HVG, the EMGrms decreased significantly in the TB (P?=?0.006) muscle. In the LVG, the EMGrms decreased significantly in the DE (P?=?0.009) and FCR (P?=?0.006) muscles. Conclusion Synchronous WBV acutely increased GH and testosterone serum concentrations and decreased the MVC and their respective maximal EMGrms activities, which indicated a possible central fatigue effect. Interestingly, only the GH response was dependent on the acceleration with respect to the subjects' responsiveness. PMID:25368995

Di Giminiani, Riccardo; Fabiani, Leila; Baldini, Giuliano; Cardelli, Giovanni; Giovannelli, Aldo; Tihanyi, Jozsef

2014-01-01

121

2-D differential quadrature solution for vibration characteristics of two-dimensional functionally graded metal\\/ceramic open cylindrical shells  

Microsoft Academic Search

In this paper, Semi-analytical 3-D elasticity solutions are presented to study the vibration characteristics of two-dimensional functionally graded (2-D FGM) metal\\/ceramic open cylindrical shells under various boundary conditions. In the present formulation, the shell has a smooth variation of volume fractions of metal and ceramic in the radial and axial directions with power law functions. The study is carried out

H. Hedayati; M. Hedayati; B. Sobhani Aragh; E. Borzabadi Farahani

2012-01-01

122

Analyses of contact forces and vibration response for a defective rolling element bearing using an explicit dynamics finite element model  

NASA Astrophysics Data System (ADS)

This paper provides insights into the physical mechanism by which defect-related impulsive forces, and consequently, vibrations are generated in defective rolling element bearings. A dynamic nonlinear finite element model of a rolling element bearing with an outer raceway defect was numerically solved using the explicit dynamics finite element software package, LS-DYNA. A hypothesis was developed to explain the numerical noise observed in the predicted vibrations and contact forces, and the noise frequencies were analytically estimated. In-depth analyses of the numerically estimated dynamic contact forces between the rolling elements and the raceways of a bearing, which are not measured in practice, and have not been reported previously, are presented in this paper. Several events associated with the traverse of the rolling elements through the outer raceway defect are elaborated, and the impulsive force generating mechanism is explained. It was found that the re-stressing of the rolling elements that occurs near the end of a raceway defect generates a burst of multiple short-duration force impulses. The modelling results also highlight that much higher contact forces and accelerations are generated on the exit of the rolling elements out of defect compared to when they strike the defective surface. A bearing with a machined outer raceway defect was tested in a controlled experiment; the measured acceleration response compared favourably with the numerically modelled acceleration results, thereby, validating the low- and high-frequency characteristics of the de-stressing and re-stressing of the rolling elements, respectively.

Singh, Sarabjeet; Köpke, Uwe G.; Howard, Carl Q.; Petersen, Dick

2014-10-01

123

Response characteristics of visual altitude control system in Bombus terrestris.  

PubMed

Frequency response characteristics of bumblebees to vertical visual oscillations were measured and analyzed. We measured the vertical force of the bees at four oscillation frequencies (0.9, 1.8, 3.6 and 7.4 Hz), and summarized their response characteristics in terms of amplitude and phase differences. The amplitude was almost constant throughout the examined frequency domain, whereas the phase gradually lagged with increasing frequency. In order to view the relationship between the input (visual oscillation) and output (response of the bee) more clearly as a control system, we compared them in the same dimension; we calculated hypothetical positions of the tethered bees on the basis of the measured variation in the vertical force, and compared them with the visual stripe positions. The resultant gain and phase data were plotted on a Bode plot. A transfer function was identified from the Bode plot, revealing that the response characteristics of the measured system could be represented as a simple expression. The dynamic control characteristics of the bumblebees were analyzed on the basis of the frequency response data. First, we showed that the measured system possesses a substantial stability margin. This means that the control system has substantial damping characteristics, and was suitable for stable flight control. In addition, our results showed that the measured bumblebee system possesses superior steady state and quick-response characteristics in comparison with a human pilot-vehicle system. Such excellence in both the steady state and transient characteristics (i.e. damping and quick response characteristics) provide the evidence that bumblebees can effectively control their flight with stability and maneuverability. PMID:17079723

Tanaka, Kensaku; Kawachi, Keiji

2006-11-01

124

Free vibration of Euler and Timoshenko nanobeams using boundary characteristic orthogonal polynomials  

NASA Astrophysics Data System (ADS)

Vibration analysis of nonlocal nanobeams based on Euler-Bernoulli and Timoshenko beam theories is considered. Nonlocal nanobeams are important in the bending, buckling and vibration analyses of beam-like elements in microelectromechanical or nanoelectromechanical devices. Expressions for free vibration of Euler-Bernoulli and Timoshenko nanobeams are established within the framework of Eringen's nonlocal elasticity theory. The problem has been solved previously using finite element method, Chebyshev polynomials in Rayleigh-Ritz method and using other numerical methods. In this study, numerical results for free vibration of nanobeams have been presented using simple polynomials and orthonormal polynomials in the Rayleigh-Ritz method. The advantage of the method is that one can easily handle the specified boundary conditions at the edges. To validate the present analysis, a comparison study is carried out with the results of the existing literature. The proposed method is also validated by convergence studies. Frequency parameters are found for different scaling effect parameters and boundary conditions. The study highlights that small scale effects considerably influence the free vibration of nanobeams. Nonlocal frequency parameters of nanobeams are smaller when compared to the corresponding local ones. Deflection shapes of nonlocal clamped Euler-Bernoulli nanobeams are also incorporated for different scaling effect parameters, which are affected by the small scale effect. Obtained numerical solutions provide a better representation of the vibration behavior of short and stubby micro/nanobeams where the effects of small scale, transverse shear deformation and rotary inertia are significant.

Behera, Laxmi; Chakraverty, S.

2014-03-01

125

Nonlinear dual-axis biodynamic response of the semi-supine human body during vertical whole-body vibration  

NASA Astrophysics Data System (ADS)

Nonlinear biodynamic responses are evident in many studies of the apparent masses of sitting and standing subjects in static postures that require muscle activity for postural control. In the present study, 12 male subjects adopted a relaxed semi-supine posture assumed to involve less muscle activity than during static sitting and standing. The supine subjects were exposed to two types of vertical vibration (in the x-axis of the semi-supine body): (i) continuous random vibration (0.25-20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75, and 1.0 m s -2 rms); (ii) intermittent random vibration (0.25-20 Hz) alternately at 0.25 and 1.0 m s -2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 10.35 to 7.32 Hz as the vibration magnitude increased from 0.125 to 1.0 m s -2 rms. This nonlinear response was apparent in both the vertical ( x-axis) apparent mass and in the horizontal ( z-axis) cross-axis apparent mass. As the vibration magnitude increased from 0.25 to 1.0 m s -2 rms, the median resonance frequency of the apparent mass with intermittent random vibration decreased from 9.28 to 8.06 Hz whereas, over the same range of magnitudes with continuous random vibration, the resonance frequency decreased from 9.62 to 7.81 Hz. The median change in the resonance frequency (between 0.25 and 1.0 m s -2 rms) was 1.37 Hz with the intermittent random vibration and 1.71 with the continuous random vibration. With the intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration of the same magnitudes. The response was typical of thixotropy that may be a primary cause of the nonlinear biodynamic responses to whole-body vibration.

Huang, Ya; Griffin, Michael J.

2008-04-01

126

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

PubMed Central

Background The superficial vein of the resting limb constricts sympathetically during exercise. Central command is the one of the neural mechanisms that controls the cardiovascular response to exercise. However, it is not clear whether central command contributes to venous vessel response during exercise. Tendon vibration during static elbow flexion causes primary muscle spindle afferents, such that a lower central command is required to achieve a given force without altering muscle force. The purpose of this study was therefore to investigate whether a reduction in central command during static exercise with tendon vibration influences the superficial venous vessel response in the resting limb. Methods Eleven subjects performed static elbow flexion at 35% of maximal voluntary contraction with (EX + VIB) and without (EX) vibration of the biceps brachii tendon. The heart rate, mean arterial pressure, and rating of perceived exertion (RPE) in overall and exercising muscle were measured. The cross-sectional area (CSAvein) and blood velocity of the basilic vein in the resting upper arm were assessed by ultrasound, and blood flow (BFvein) was calculated using both variables. Results Muscle tension during exercise was similar between EX and EX + VIB. However, RPEs at EX + VIB were lower than those at EX (P <0.05). Increases in heart rate and mean arterial pressure during exercise at EX + VIB were also lower than those at EX (P <0.05). CSAvein in the resting limb at EX decreased during exercise from baseline (P <0.05), but CSAvein at EX + VIB did not change during exercise. CSAvein during exercise at EX was smaller than that at EX + VIB (P <0.05). However, BFvein did not change during the protocol under either condition. The decreases in circulatory response and RPEs during EX + VIB, despite identical muscle tension, showed that activation of central command was less during EX + VIB than during EX. Abolishment of the decrease in CSAvein during exercise at EX + VIB may thus have been caused by a lower level of central command at EX + VIB rather than EX. Conclusion Diminished central command induced by tendon vibration may attenuate the superficial venous vessel response of the resting limb during sustained static arm exercise. PMID:23134654

2012-01-01

127

Nonlinear dual-axis biodynamic response of the semi-supine human body during longitudinal horizontal whole-body vibration  

NASA Astrophysics Data System (ADS)

The resonance frequencies in frequency response functions of the human body (e.g. apparent mass and transmissibility) decrease with increasing vibration magnitude. This nonlinear biodynamic response is found with various sitting and standing postures requiring postural control. The present study measured the apparent mass of the body in a relaxed semi-supine posture with two types of longitudinal horizontal vibration (in the z-axis of the semi-supine body): (i) continuous random excitation (0.25-20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75 and 1.0 ms -2 rms); (ii) intermittent random excitation (0.25-20 Hz) alternately at 0.25 and 1.0 ms -2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 3.7 to 2.4 Hz as the vibration magnitude increased from 0.125 to 1.0 ms -2 rms. A nonlinear response was apparent in both the horizontal ( z-axis) apparent mass and the vertical ( x-axis) cross-axis apparent mass. With intermittent random vibration, as the vibration magnitude increased from 0.25 to 1.0 ms -2 rms, the median resonance frequency of the apparent mass decreased from 3.2 to 2.5 Hz whereas, with continuous random vibration over the same range of magnitudes, the resonance frequency decreased from 3.4 to 2.4 Hz. The median change in the resonance frequency (between 0.25 and 1.0 ms -2 rms) was 0.6 Hz with the intermittent random vibration and 0.9 Hz with the continuous random vibration. With intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration at the same magnitudes. The responses were consistent with passive thixotropy being a primary cause of nonlinear biodynamic responses to whole-body vibration, although reflex activity of the muscles may also have an influence.

Huang, Ya; Griffin, Michael J.

2008-04-01

128

Myoelectric Response of Back Muscles to Vertical Random Whole-Body Vibration with Different Magnitudes at Different Postures  

NASA Astrophysics Data System (ADS)

Back muscle forces contribute essentially to the whole-body vibration-induced spinal load. The electromyogram (EMG) can help to estimate these forces during whole-body vibration (WBV). Thirty-eight subjects were exposed to identical random low-frequency WBV (0·7, 1·0 and 1·4 m/s-2 r.m.s. weighted acceleration) at a relaxed, erect and bent forward postures. The acceleration of the seat and the force between the seat and the buttocks were measured. Six EMGs were derived from the right side of the m. trapezius pars descendens, m. ileocostalis lumborum pars thoracis, m. ileocostalis lumborum pars lumborum; m. longissimus thoracis pars thoracis, m. longissimus thoracis pars lumborum, and lumbar multifidus muscle. All data were filtered for anti-aliasing and sampled with 1000 Hz. Artefacts caused by the ECG in the EMG were identified and eliminated in the time domain using wavelets. The individually rectified and normalized EMGs were averaged across subjects. The EMGs without WBV exhibited characteristic patterns for the three postures examined. The coherence and transfer functions indicated characteristic myoelectric responses to random WBV with several effects of posture and WBV magnitude. A comprehensive set of transfer functions from the seat acceleration or the mean normalized input force to the mean processed EMG was presented.The results can be used for the development of more sophisticated models with a separate control of various back muscle groups. However, the EMG-force relationship under dynamic conditions needs to be examined in more detail before the results can be implemented. Since different reflex mechanisms depending on the frequency of WBV are linked with different types of active muscle fibres, various time delays between the EMG and muscle force may be necessary.

BLÜTHNER, R.; SEIDEL, H.; HINZ, B.

2002-05-01

129

Effects of excitation area of longitudinal transducer on the flexural vibration characteristics of a rectangular plate in stripe mode.  

PubMed

The flexural vibration characteristics of a rectangular plate in stripe mode, driven at its center by a different longitudinal vibration ultrasonic transducer (LVUT) with different excitation area are investigated. The variation in the nodal lines and corresponding resonant frequency of the rectangular plate under different excitation area are calculated by using finite element method (FEM). The results show that the resonant frequency increases with the excitation area of the LVUT increasing, and the nodal lines bend obviously when the radius r of excitation area is greater than a certain value. The experimental tests are carried out by the aid of Polytec PSV-400 Scanning laser Vibrometer, and the results agree well those of numerically calculated. It indicates that the larger excitation area of longitudinal transducer may affect the ultrasonic field radiated by the rectangular plate. PMID:25616374

He, Xiping; Yao, Jing; Zhang, Haidao; Liu, Doudou; Li, Jiaxing

2015-04-01

130

Dynamic response of electronic systems to shocks and vibrations: Application of analytical (mathematical) modeling  

NASA Astrophysics Data System (ADS)

Some basic problems of the dynamic response of electronic and photonic (E&P) systems to shocks and vibrations are addressed and discussed. The emphasis is on analytical (mathematical) modeling, the reliability physics behind the addressed phenomena, and design-for-reliability (DfR) issues and challenges. The addressed problems include 1) linear response: effect of viscous damping, shock tests vs. drop tests, role of compliant interfaces, and maximum acceleration and maximum dynamic stress as a suitable reliability criterion; 2) nonlinear response: printed circuit board (PCB) experiencing an impact load applied to its support contour and ball-grid-array (BGA) testing on the board level; 3) shock protection of portable electronics, including the possible use of nano-wires as a suitable protective "cushion". The fruitfulness of the probabilistic DfR (PDfR) concept to quantify and assure the field (operational) reliability of E&P devices and systems is also indicated.

Suhir, E.

2012-08-01

131

Physiological response to whole-body vibration in athletes and sedentary subjects.  

PubMed

Whole-body vibration (WBV) is a new exercise method, with good acceptance among sedentary subjects. The metabolic response to WBV has not been well documented. Three groups of male subjects, inactive (SED), endurance (END) and strength trained (SPRINT) underwent a session of side-alternating WBV composed of three 3-min exercises (isometric half-squat, dynamic squat, dynamic squat with added load), and repeated at three frequencies (20, 26 and 32 Hz). VO(2), heart rate and Borg scale were monitored. Twenty-seven healthy young subjects (10 SED, 8 SPRINT and 9 END) were included. When expressed in % of their maximal value recorded in a treadmill test, both the peak oxygen consumption (VO(2)) and heart rate (HR) attained during WBV were greatest in the SED, compared to the other two groups (VO(2): 59.3 % in SED vs 50.8 % in SPRINT and 48.0 % in END, p<0.01; HR 82.7 % in SED vs 80.4 % in SPRINT and 72.4 % in END, p<0.05). In conclusions, the heart rate and metabolic response to WBV differs according to fitness level and type, exercise type and vibration frequency. In SED, WBV can elicit sufficient cardiovascular response to benefit overall fitness and thus be a potentially useful modality for the reduction of cardiovascular risk. PMID:25157652

Gojanovic, B; Feihl, F; Gremion, G; Waeber, B

2014-12-23

132

Distributed vibration/acoustic sensing with high frequency response and spatial resolution based on time-division multiplexing  

NASA Astrophysics Data System (ADS)

A novel time-division multiplexing scheme is proposed and demonstrated for distributed vibration/acoustic sensing with broad frequency response range and high spatial resolution. By setting the time delay between a narrow pulse and a quasi-continuous wave properly, conventional phase optical time-domain reflectometry and polarization diversity scheme can be combined without crosstalk to determine position and frequency of vibration event, respectively. Detections of high vibration frequency of 0.6 MHz and low frequency of 1 Hz are presented with 1 m spatial resolution over 680 m single-mode sensing fiber.

Qin, Zengguang; Chen, Liang; Bao, Xiaoyi

2014-11-01

133

Effects of an elastic mass on frequency response characteristics of an ultra-thin piezoelectric micro-acoustic actuator.  

PubMed

This paper presents an optimized method to improve the sound quality of ultra-thin piezoelectric micro-acoustic actuators. To achieve flat and smooth frequency response characteristics of the piezoelectric acoustic actuators, we have proposed an elastic mass attached to the acoustic diaphragm. The effects of the elastic mass on frequency response characteristics of the piezoelectric acoustic actuator were investigated by finite element analysis simulation and laser scanning vibrometer measurement. Based on the modal and vibrational characteristics, it was found that the fabricated piezoelectric acoustic actuator has a significant dip of 1.32 kHz and peak of 2.24 kHz, which correspond respectively to the (1,3) and (3,1) resonant modes of the acoustic diaphragm. However, by attaching an elastic mass to the acoustic diaphragm with a shape similar to the (3,1) mode, the resonant frequencies corresponding to the (1,3) and (3,1) modes shifted to higher frequencies and the vibrational displacements at each mode were dramatically reduced by about 40%. As a result, the dip at (1,3) mode was greatly improved by 13 dB and total harmonic distortion was dramatically reduced from 80.83% to 8.71%. This paper shows that the optimized elastic mass can allow flat and smooth frequency response characteristics by improving the significant peak and dip. PMID:25004529

Kim, Hye Jin; Yang, Woo Seok; No, Kwangsoo

2013-08-01

134

Test-Anchored Vibration Response Predictions for an Acoustically Energized Curved Orthogrid Panel with Mounted Components  

NASA Technical Reports Server (NTRS)

rich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for component-loaded curved orthogrid panels typical of launch vehicle skin structures. The test data were used to anchor computational predictions of a variety of spatially distributed responses including acceleration, strain and component interface force. Transfer functions relating the responses to the input pressure field were generated from finite element based modal solutions and test-derived damping estimates. A diffuse acoustic field model was applied to correlate the measured input sound pressures across the energized panel. This application quantifies the ability to quickly and accurately predict a variety of responses to acoustically energized skin panels with mounted components. Favorable comparisons between the measured and predicted responses were established. The validated models were used to examine vibration response sensitivities to relevant modeling parameters such as pressure patch density, mesh density, weight of the mounted component and model form. Convergence metrics include spectral densities and cumulative root-mean squared (RMS) functions for acceleration, velocity, displacement, strain and interface force. Minimum frequencies for response convergence were established as well as recommendations for modeling techniques, particularly in the early stages of a component design when accurate structural vibration requirements are needed relatively quickly. The results were compared with long-established guidelines for modeling accuracy of component-loaded panels. A theoretical basis for the Response/Pressure Transfer Function (RPTF) approach provides insight into trends observed in the response predictions and confirmed in the test data. The software developed for the RPTF method allows easy replacement of the diffuse acoustic field with other pressure fields such as a turbulent boundary layer (TBL) model suitable for vehicle ascent. Structural responses using a TBL model were demonstrated, and wind tunnel tests have been proposed to anchor the predictions and provide new insight into modeling approaches for this environment. Finally, design load factors were developed from the measured and predicted responses and compared with those derived from traditional techniques such as historical Mass Acceleration Curves and Barrett scaling methods for acreage and component-loaded panels.

Frady, Gregory P.; Duvall, Lowery D.; Fulcher, Clay W. G.; Laverde, Bruce T.; Hunt, Ronald A.

2011-01-01

135

Analytical and experimental comparisons of electromechanical vibration response of a piezoelectric bimorph beam for power harvesting  

NASA Astrophysics Data System (ADS)

Power harvesters that extract energy from vibrating systems via piezoelectric transduction show strong potential for powering smart wireless sensor devices in applications of health condition monitoring of rotating machinery and structures. This paper presents an analytical method for modelling an electromechanical piezoelectric bimorph beam with tip mass under two input base transverse and longitudinal excitations. The Euler-Bernoulli beam equations were used to model the piezoelectric bimorph beam. The polarity-electric field of the piezoelectric element is excited by the strain field caused by base input excitation, resulting in electrical charge. The governing electromechanical dynamic equations were derived analytically using the weak form of the Hamiltonian principle to obtain the constitutive equations. Three constitutive electromechanical dynamic equations based on independent coefficients of virtual displacement vectors were formulated and then further modelled using the normalised Ritz eigenfunction series. The electromechanical formulations include both the series and parallel connections of the piezoelectric bimorph. The multi-mode frequency response functions (FRFs) under varying electrical load resistance were formulated using Laplace transformation for the multi-input mechanical vibrations to provide the multi-output dynamic displacement, velocity, voltage, current and power. The experimental and theoretical validations reduced for the single mode system were shown to provide reasonable predictions. The model results from polar base excitation for off-axis input motions were validated with experimental results showing the change to the electrical power frequency response amplitude as a function of excitation angle, with relevance for practical implementation.

Lumentut, M. F.; Howard, I. M.

2013-03-01

136

A Study of the Temperature Characteristics of Vibration Mode Axes for Vibratory Cylinder Gyroscopes  

PubMed Central

The zero bias stability, which is an important performance parameter for vibratory cylinder gyroscopes, is high sensitive to temperature change. It is considered that the varying temperature makes the vibration mode axes unstable, which has significant influence on the zero bias stability. This paper will investigate this problem in detail. First, the relationships between the angular positions of vibration mode axes and the zero bias are analyzed. Secondly, the thermal-modal model of the cylinder resonator with several defects such as mass imbalance, frequency split (FS), and geometry errors are developed by ANSYS. Simulation results show that with the increase of temperature, angular positions of the vibration mode axes obviously change, which leads to a dramatic zero bias drift. Finally, several major influence factors on the angular position stability of vibration mode axes, including frequency split, geometry errors, thermal elastic modulus coefficient (TEMC) and thermal expansion coefficient (TEC) are analyzed in detail. Simulation results in this paper will be helpful for deep understanding of the drift principle of zero bias induced by temperature for vibratory cylinder gyroscopes and also be helpful for further temperature compensation or control. PMID:22164038

Wu, Yulie; Xi, Xiang; Tao, Yi; Wu, Xiaomei; Wu, Xuezhong

2011-01-01

137

Vibration Response Predictions for Heavy Panel Mounted Components from Panel Acreage Environment Specifications  

NASA Technical Reports Server (NTRS)

The development of new launch vehicles in the Aerospace industry often relies on response measurements taken from previously developed vehicles during various stages of liftoff and ascent, and from wind tunnel models. These measurements include sound pressure levels, dynamic pressures in turbulent boundary layers and accelerations. Rigorous statistical scaling methods are applied to the data to derive new environments and estimate the performance of new skin panel structures. Scaling methods have proven to be reliable, particularly for designs similar to the vehicles used as the basis for scaling, and especially in regions of smooth acreage without exterior protuberances or heavy components mounted to the panel. To account for response attenuation of a panel-mounted component due to its apparent mass at higher frequencies, the vibroacoustics engineer often reduces the acreage vibration according to a weight ratio first suggested by Barrett. The accuracy of the reduction is reduced with increased weight of the panel-mounted component, and does not account for low-frequency amplification of the component/panel response as a system. A method is proposed that combines acreage vibration from scaling methods with finite element analysis to account for the frequency-dependent dynamics of heavy panel-mounted components. Since the acreage and mass-loaded skins respond to the same dynamic input pressure, such pressure may be eliminated in favor of a frequency-dependent scaling function applied to the acreage vibration to predict the mass-loaded panel response. The scaling function replaces the Barrett weight ratio, and contains all of the dynamic character of the loaded and unloaded skin panels. The solution simplifies for spatially uncorrelated and fully correlated input pressures. Since the prediction uses finite element models of the loaded and unloaded skins, a rich suite of response data are available to the design engineer, including interface forces, stress and strain, as well as acceleration and displacement. An extension of the method is also developed to incorporate the effect of a local protuberance near a heavy component. Acreage environments from traditional scaling methods with and without protuberance effects serve as the basis for the extension. Authors:

Harrison, Phillip; Frady, Greg; Duvall, Lowery; Fulcher, Clay; LaVerde, Bruce

2010-01-01

138

Semi-analytical study of free vibration characteristics of shear deformable filament wound anisotropic shells of revolution  

NASA Astrophysics Data System (ADS)

Free vibration characteristics of filament wound anisotropic shells of revolution are investigated by using multisegment numerical integration technique in combination with a modified frequency trial method. The applicability of multisegment numerical integration technique is extended to the solution of free vibration problem of anisotropic composite shells of revolution through the use of finite exponential Fourier transform of the fundamental shell equations. The governing shell equations comprise the full anisotropic form of the constitutive relations, including first-order transverse shear deformation, and all components of translatory and rotary inertia. The variation of the stiffness coefficients along the axis of the shell is also incorporated into the solution method. Filaments are assumed to be placed along the geodesic fiber path on the shell of revolution resulting in the variation of the stiffness coefficients along the axis of the composite shell of revolution with general meridional curvature. Sample solutions have been performed on the effect of the variation of the stiffness coefficients on the free vibration behavior of filament wound truncated conical and spherical shells of revolution.

Kayran, Altan; Yavuzbalkan, Erdem

2009-01-01

139

Method for Vibration Response Simulation and Sensor Placement Optimization of a Machine Tool Spindle System with a Bearing Defect  

PubMed Central

Bearing defects are one of the most important mechanical sources for vibration and noise generation in machine tool spindles. In this study, an integrated finite element (FE) model is proposed to predict the vibration responses of a spindle bearing system with localized bearing defects and then the sensor placement for better detection of bearing faults is optimized. A nonlinear bearing model is developed based on Jones' bearing theory, while the drawbar, shaft and housing are modeled as Timoshenko's beam. The bearing model is then integrated into the FE model of drawbar/shaft/housing by assembling equations of motion. The Newmark time integration method is used to solve the vibration responses numerically. The FE model of the spindle-bearing system was verified by conducting dynamic tests. Then, the localized bearing defects were modeled and vibration responses generated by the outer ring defect were simulated as an illustration. The optimization scheme of the sensor placement was carried out on the test spindle. The results proved that, the optimal sensor placement depends on the vibration modes under different boundary conditions and the transfer path between the excitation and the response. PMID:23012514

Cao, Hongrui; Niu, Linkai; He, Zhengjia

2012-01-01

140

Necessary research for standardization of subjective scaling of whole-body vibration.  

PubMed

Researches into the relationship between the physical quantity of vibration and the subjectively perceived quantity become important in designs for the vibration environment. Subjective experimental methods to obtain the relationship between the physical quantity of vibration and the subjectively perceived quantity are different depending on the design objectives which consider the human sense of vibration characteristic. In this review, the following are outlined: (i) fundamental methods for obtaining the design objectives for vibration environments; (ii) reported findings on the physical quantity of vibration environments and the human characteristics of sense vibration; and (iii) problems with and limits of the ISO 2631-1 standard, which defines the subjective response of the ride comfort in public transportation. Finally, the directions of research into the subjective experimental methods for obtaining design objectives in the vibration environment considering of the human characteristics of sense vibration are described. PMID:16100916

Maeda, Setsuo

2005-07-01

141

DFT study of conformational and vibrational characteristics of 2-(2-hydroxyphenyl)benzothiazole molecule  

NASA Astrophysics Data System (ADS)

The conformational and IR and Raman spectral studies of 2-(2-hydroxyphenyl)benzothiazole have been carried out by using the DFT method at the B3LYP/6-311++G** level. The detailed vibrational assignments have been done on the basis of calculated potential energy distributions. Comparative studies of molecular geometries, atomic charges and vibrational fundamentals of all the conformers have been made. There are four possible conformers for this molecule. The optimized geometrical parameters obtained by B3LYP/6-311++G** method showed good agreement with the experimental X-ray data. The atomic polar tensor (APT) charges, Mulliken atomic charges, natural bond orbital (NBO) analysis and HOMO-LUMO energy gap of HBT and its conformers were also computed.

Pandey, Urmila; Srivastava, Mayuri; Singh, R. P.; Yadav, R. A.

2014-08-01

142

DFT study of conformational and vibrational characteristics of 2-(2-hydroxyphenyl)benzothiazole molecule.  

PubMed

The conformational and IR and Raman spectral studies of 2-(2-hydroxyphenyl)benzothiazole have been carried out by using the DFT method at the B3LYP/6-311++G(**) level. The detailed vibrational assignments have been done on the basis of calculated potential energy distributions. Comparative studies of molecular geometries, atomic charges and vibrational fundamentals of all the conformers have been made. There are four possible conformers for this molecule. The optimized geometrical parameters obtained by B3LYP/6-311++G(**) method showed good agreement with the experimental X-ray data. The atomic polar tensor (APT) charges, Mulliken atomic charges, natural bond orbital (NBO) analysis and HOMO-LUMO energy gap of HBT and its conformers were also computed. PMID:24727164

Pandey, Urmila; Srivastava, Mayuri; Singh, R P; Yadav, R A

2014-08-14

143

Acute Bone Marker Responses to Whole-Body Vibration and Resistance Exercise in Young Women  

PubMed Central

Whole-body vibration (WBV) augments the musculoskeletal effects of resistance exercise (RE). However, its acute effects on bone turnover markers (BTM) have not been determined. This study examined BTM responses to acute high intensity RE and high intensity RE with WBV (WBV+RE) in young women (n=10) taking oral contraceptives in a randomized, cross-over repeated measures design. WBV+RE exposed subjects to 5 one-minute bouts of vibration (20 Hz, 3.38 peak–peak displacement, separated by 1 minute of rest) prior to RE. Fasting blood samples were obtained before (Pre), immediately post WBV (PostVib), immediately post RE (IP), and 30 minutes post RE (P30). Bone ALP did not change at any time point. TRAP5b significantly (p<0.05) increased from the Pre to PostVib, then decreased from IP to P30 for both conditions. CTX significantly decreased (p<0.05) from Pre to PostVib and from Pre to P30 only for WBV+RE. WBV+RE showed a greater decrease in CTX than RE (-12.6 ± 4.7% vs. -1.13 ± 3.5%). In conclusion, WBV was associated with acute decreases in CTX levels not elicited with resistance exercise alone in young women. PMID:22902255

Sherk, Vanessa D.; Chrisman, Carmen; Smith, Jessica; Young, Kaelin C.; Singh, Harshvardhan; Bemben, Michael G.; Bemben, Debra A.

2014-01-01

144

Flexoelectric effect on the electroelastic responses and vibrational behaviors of a piezoelectric nanoplate  

NASA Astrophysics Data System (ADS)

Flexoelectricity, referring to the coupling between electric polarization and strain gradients, is a universal effect in all dielectrics and may become manifest at the nano-scale. The current work aims to investigate the flexoelectric effect on the electroelastic responses and the free vibrational behaviors of a piezoelectric nanoplate (PNP). Based on the conventional Kirchhoff plate theory and the extended linear piezoelectricity theory, the governing equation and the boundary conditions of a clamped PNP with the consideration of the static bulk flexoelectricity are derived. Ritz approximate solutions of the electroelastic fields and the resonant frequencies demonstrate the size-dependency of the flexoelectric effect, which is more prominent for thinner plates with smaller thickness as expected. Simulation results also indicate that the influence of the flexoelectricity upon the electroelastic fields of a bending PNP and the transverse vibration of the PNP is sensitive to the plate in-plane dimensions as well as the applied electric voltage. Moreover, it is suggested that the possible frequency tuning of a PNP resonator by adjusting applied electrical load warrants the consideration of the flexoelectricity. This study is claimed to provide a theoretical predicition on the trend of the flexoelectric effect upon the static and dynamic behaviors of a bending PNP, thus sheding light on understanding the underlying physics of electromechanical coupling at the nano-scale to some extent.

Zhang, Zhengrong; Yan, Zhi; Jiang, Liying

2014-07-01

145

Acute bone marker responses to whole-body vibration and resistance exercise in young women.  

PubMed

Whole-body vibration (WBV) augments the musculoskeletal effects of resistance exercise (RE). However, its acute effects on bone turnover markers (BTM) have not been determined. This study examined BTM responses to acute high-intensity RE and high-intensity RE with WBV (WBV+RE) in young women (n=10) taking oral contraceptives in a randomized, crossover repeated measures design. WBV+RE exposed subjects to 5 one-minute bouts of vibration (20 Hz, 3.38 peak-peak displacement, separated by 1 min of rest) before RE. Fasting blood samples were obtained before (Pre), immediately after WBV (PostVib), immediately after RE (IP), and 30-min after RE (P30). Bone alkaline phosphatase did not change at any time point. Tartrate-resistant acid phosphatase 5b significantly increased (p<0.05) from the Pre to PostVib, then decreased from IP to P30 for both conditions. C-terminal telopeptide of type I collagen (CTX) significantly decreased (p<0.05) from Pre to PostVib and from Pre to P30 only for WBV+RE. WBV+RE showed a greater decrease in CTX than RE (-12.6% ± 4.7% vs -1.13% ± 3.5%). In conclusion, WBV was associated with acute decreases in CTX levels not elicited with RE alone in young women. PMID:22902255

Sherk, Vanessa D; Chrisman, Carmen; Smith, Jessica; Young, Kaelin C; Singh, Harshvardhan; Bemben, Michael G; Bemben, Debra A

2013-01-01

146

Neural basis of new clinical vestibular tests: otolithic neural responses to sound and vibration.  

PubMed

Extracellular single neuron recording and labelling studies of primary vestibular afferents in Scarpa's ganglion have shown that guinea-pig otolithic afferents with irregular resting discharge are preferentially activated by 500 Hz bone-conducted vibration (BCV) and many also by 500 Hz air-conducted sound (ACS) at low threshold and high sensitivity. Very few afferent neurons from any semicircular canal are activated by these stimuli and then only at high intensity. Tracing the origin of the activated neurons shows that these sensitive otolithic afferents originate mainly from a specialized region, the striola, of both the utricular and saccular maculae. This same 500 Hz BCV elicits vestibular-dependent eye movements in alert guinea-pigs and in healthy humans. These stimuli evoke myogenic potentials, vestibular-evoked myogenic potentials (VEMPs), which are used to test the function of the utricular and saccular maculae in human patients. Although utricular and saccular afferents can both be activated by BCV and ACS, the differential projection of utricular and saccular afferents to different muscle groups allows for differentiation of the function of these two sensory regions. The basic neural data support the conclusion that in human patients in response to brief 500 Hz BCV delivered to Fz (the midline of the forehead at the hairline), the cervical VEMP indicates predominantly saccular function and the ocular VEMP indicates predominantly utricular function. The neural, anatomical and behavioural evidence underpins clinical tests of otolith function in humans using sound and vibration. PMID:24754528

Curthoys, Ian S; Vulovic, Vedran; Burgess, Ann M; Manzari, Leonardo; Sokolic, Ljiljana; Pogson, Jacob; Robins, Mike; Mezey, Laura E; Goonetilleke, Samanthi; Cornell, Elaine D; MacDougall, Hamish G

2014-05-01

147

Tensor decomposition techniques in the solution of vibrational coupled cluster response theory eigenvalue equations.  

PubMed

We show how the eigenvalue equations of vibrational coupled cluster response theory can be solved using a subspace projection method with Davidson update, where basis vectors are stacked tensors decomposed into canonical (CP, Candecomp/Parafac) form. In each update step, new vectors are first orthogonalized to old vectors, followed by a tensor decomposition to a prescribed threshold TCP. The algorithm can provide excitation energies and eigenvectors of similar accuracy as a full vector approach and with only a very modest increase in the number of vectors required for convergence. The algorithm is illustrated with sample calculations for formaldehyde, 1,2,5-thiadiazole, and water. Analysis of the formaldehyde and thiadiazole calculations illustrate a number of interesting features of the algorithm. For example, the tensor decomposition threshold is optimally put to rather loose values, such as TCP = 10(-2). With such thresholds for the tensor decompositions, the original eigenvalue equations can still be solved accurately. It is thus possible to directly calculate vibrational wave functions in tensor decomposed format. PMID:25591336

Godtliebsen, Ian H; Hansen, Mads Bøttger; Christiansen, Ove

2015-01-14

148

Tensor decomposition techniques in the solution of vibrational coupled cluster response theory eigenvalue equations  

NASA Astrophysics Data System (ADS)

We show how the eigenvalue equations of vibrational coupled cluster response theory can be solved using a subspace projection method with Davidson update, where basis vectors are stacked tensors decomposed into canonical (CP, Candecomp/Parafac) form. In each update step, new vectors are first orthogonalized to old vectors, followed by a tensor decomposition to a prescribed threshold TCP. The algorithm can provide excitation energies and eigenvectors of similar accuracy as a full vector approach and with only a very modest increase in the number of vectors required for convergence. The algorithm is illustrated with sample calculations for formaldehyde, 1,2,5-thiadiazole, and water. Analysis of the formaldehyde and thiadiazole calculations illustrate a number of interesting features of the algorithm. For example, the tensor decomposition threshold is optimally put to rather loose values, such as TCP = 10-2. With such thresholds for the tensor decompositions, the original eigenvalue equations can still be solved accurately. It is thus possible to directly calculate vibrational wave functions in tensor decomposed format.

Godtliebsen, Ian H.; Hansen, Mads Bøttger; Christiansen, Ove

2015-01-01

149

Frequency response characteristics and response spectra of base-isolated and un-isolated structures  

SciTech Connect

The transmissibility of seismic loads through a linear base-isolation system is analyzed using an impedance method. The results show that the system acts like a {open_quotes}low-pass{close_quotes} filter. It attenuates high-frequency loads but passes through low-frequency ones. The filtering effect depends on the vibration frequencies and damping of the isolated structure and the isolation system. This paper demonstrates the benefits and design principles of base isolation by comparing the transmissibilities and response spectra of isolated and un-isolated structures. Parameters of typical isolated buildings and ground motions of the 1994 Northridge earthquake are used for the demonstration.

Mok, G.C. [Lawrence Livermore National Lab., CA (United States); Namba, H. [Shimizu Corporation, Tokyo (Japan)

1995-07-06

150

Temperature-dependent fiber optic hydrogen gas sensor response characteristics  

NASA Astrophysics Data System (ADS)

Dynamic response characteristics of silica fiber long-period grating with a modified cladding, composed of ~10-100 nm nanoparticle palladium oxides thin film material prepared by a magnetron sputtering technique, have been investigated at several elevated temperatures with a 2%H2/98%N II mixing gas concentration. The fiber cladding modified grating, without cladding chemical etching process, demonstrates 540 pm per 1% H II sensitivity, a better than 1sec response times at 160 °C, respectively. The thermal responses of the prototype have demonstrated increased dynamic wavelength shift while reducing response time simultaneously. The observed thermal dependence of the prototype could be attributed to a combined effect of thermal dependent hydrogen atoms diffusion rate and hydrogen atoms solubility.

Xia, Hua; Deng, Kung-Li; Bousman, Ken; Wu, Juntao; Lee, Boon; Guida, Renato; McCarthy, Kevin

2006-08-01

151

Method for determining the frequency-response characteristics of an element or system from the system transient output response to a known input function  

NASA Technical Reports Server (NTRS)

A method is presented for the determination of the frequency-response characteristics of an element or system by utilizing the transient output response to a known but arbitrary input to the system. Since the application of special inputs, such as step functions or sinusoids, is often imperfect or impractical, a method for utilizing arbitrary inputs is desirable. Simple flight-test data may be reduced by this method to give the frequency response of an aircraft. Examples are given as determinations of aircraft frequency responses; however, the method can be applied to any type of dynamic system, such as automatic-control components, vibration-absorption equipment, and many types of instruments. The method requires that the arbitrary input function tend to a finite value after a finite time and that the system or element output be measured as a representative quantity having a static sensitivity. (author)

Curfman, Howard J; Gardiner, Robert A

1950-01-01

152

Separating Fluid Shear Stress from Acceleration during Vibrations in Vitro: Identification of Mechanical Signals Modulating the Cellular Response  

PubMed Central

The identification of the physical mechanism(s) by which cells can sense vibrations requires the determination of the cellular mechanical environment. Here, we quantified vibration-induced fluid shear stresses in vitro and tested whether this system allows for the separation of two mechanical parameters previously proposed to drive the cellular response to vibration – fluid shear and peak accelerations. When peak accelerations of the oscillatory horizontal motions were set at 1g and 60Hz, peak fluid shear stresses acting on the cell layer reached 0.5Pa. A 3.5-fold increase in fluid viscosity increased peak fluid shear stresses 2.6-fold while doubling fluid volume in the well caused a 2-fold decrease in fluid shear. Fluid shear was positively related to peak acceleration magnitude and inversely related to vibration frequency. These data demonstrated that peak shear stress can be effectively separated from peak acceleration by controlling specific levels of vibration frequency, acceleration, and/or fluid viscosity. As an example for exploiting these relations, we tested the relevance of shear stress in promoting COX-2 expression in osteoblast like cells. Across different vibration frequencies and fluid viscosities, neither the level of generated fluid shear nor the frequency of the signal were able to consistently account for differences in the relative increase in COX-2 expression between groups, emphasizing that the eventual identification of the physical mechanism(s) requires a detailed quantification of the cellular mechanical environment. PMID:23074384

Uzer, Gunes; Manske, Sarah L; Chan, M Ete; Chiang, Fu-Pen; Rubin, Clinton T; Frame, Mary D; Judex, Stefan

2012-01-01

153

Motion characteristics and output voltage analysis of micro-vibration energy harvester based on diamagnetic levitation  

NASA Astrophysics Data System (ADS)

In this paper, the force analysis and output performance of the micro-vibration energy harvester are elaborated. The force of the floating magnet in the magnetic field of the lifting magnet is firstly analyzed. Using COMSOL™, the change of magnetic force exerted on the floating magnet versus the vertical distance and the horizontal eccentric distance is obtained for different lifting magnets of a cylinder, a ring and an inner cylinder plus an outer ring, respectively. When the distance between the lifting and floating magnets ranges from 7.3 to 8.1 mm, the change rate of the magnetic force versus the vertical distance for the inner cylinder plus outer ring structure is the smallest, whose value is 619 µN/mm. In other words, if the inner cylinder plus outer ring structure is used as the lifting magnet, the vibration space of the floating magnet is the largest, which is 8 and 7.6 % larger than the cylinder and ring lifting magnets, respectively. The horizontal restoring forces of the three structures are substantially equal to each other at the horizontal eccentric distance of 4 mm, which is around 860 µN. Then the equilibrium position change of the floating magnet is discussed when the energy harvester is in an inclined position. Finally, by the analysis of the vibration model, the output performances of the energy harvester are comparatively calculated under the vertical and inclined positions. At the natural frequency of 6.93 Hz, the maximum power of 66.7 µW is generated.

Ye, Zhitong; Duan, Zhiyong; Takahata, Kenichi; Su, Yufeng

2014-08-01

154

Motion characteristics and output voltage analysis of micro-vibration energy harvester based on diamagnetic levitation  

NASA Astrophysics Data System (ADS)

In this paper, the force analysis and output performance of the micro-vibration energy harvester are elaborated. The force of the floating magnet in the magnetic field of the lifting magnet is firstly analyzed. Using COMSOL™, the change of magnetic force exerted on the floating magnet versus the vertical distance and the horizontal eccentric distance is obtained for different lifting magnets of a cylinder, a ring and an inner cylinder plus an outer ring, respectively. When the distance between the lifting and floating magnets ranges from 7.3 to 8.1 mm, the change rate of the magnetic force versus the vertical distance for the inner cylinder plus outer ring structure is the smallest, whose value is 619 µN/mm. In other words, if the inner cylinder plus outer ring structure is used as the lifting magnet, the vibration space of the floating magnet is the largest, which is 8 and 7.6 % larger than the cylinder and ring lifting magnets, respectively. The horizontal restoring forces of the three structures are substantially equal to each other at the horizontal eccentric distance of 4 mm, which is around 860 µN. Then the equilibrium position change of the floating magnet is discussed when the energy harvester is in an inclined position. Finally, by the analysis of the vibration model, the output performances of the energy harvester are comparatively calculated under the vertical and inclined positions. At the natural frequency of 6.93 Hz, the maximum power of 66.7 µW is generated.

Ye, Zhitong; Duan, Zhiyong; Takahata, Kenichi; Su, Yufeng

2015-01-01

155

Calibration characteristics of IRAD GAGE vibrating wire stressmeter at normal and high temperature. Volume 1  

SciTech Connect

This report describes calibration studies of the IRAD GAGE Vibrating Wire Stressmeter. The work has been performed for the University of California, Lawrence Livermore Laboratory, to understand and interpret the behavior and performance of the stressmeter in Climax granite. To help interpret the results obtained in Climax granite, the study also included calibration tests of the gage in other materials: Barre granite, aluminum, and Lucite. Stressmeter calibrations were carried out in thin rock slabs by determining the relation between the stressmeter readings and uniaxial plane stresses. Calibrations were also conducted under biaxial and triaxial stress fields.

Dutta, P. K.; Hatfield, R. W.; Runstadler, Jr., P. W.

1981-10-01

156

Analysis of lateral and torsional vibration characteristics of beams and shafts with end located rotational masses  

NASA Technical Reports Server (NTRS)

Partial differential equations are derived for free lateral and torsional vibration of a uniform free-free beam with a rotational mass attached to each extremity. For appropriate boundary conditions, nonlinear algebraic equations are obtained using a symbolic manipulation computer program, the solutions of which enable the computation of the neutral frequencies and mode-shapes. The mode-shapes are linear combinations of trigonometric and hyperbolic sine and cosine functions. A computer program is written for the numerical solution of the algebraic equations mentioned above, which can compute the natural frequencies, mode-shapes, and node points for any given set of parameters, for any given number of modes.

Robertson, D. K.

1984-01-01

157

Optimum Design of a Helicopter Rotor for Low Vibration Using Aeroelastic Analysis and Response Surface Methods  

NASA Astrophysics Data System (ADS)

An aeroelastic analysis based on finite elements in space and time is used to model the helicopter rotor in forward flight. The rotor blade is represented as an elastic cantilever beam undergoing flap and lag bending, elastic torsion and axial deformations. The objective of the improved design is to reduce vibratory loads at the rotor hub that are the main source of helicopter vibration. Constraints are imposed on aeroelastic stability, and move limits are imposed on the blade elastic stiffness design variables. Using the aeroelastic analysis, response surface approximations are constructed for the objective function (vibratory hub loads). It is found that second order polynomial response surfaces constructed using the central composite design of the theory of design of experiments adequately represents the aeroelastic model in the vicinity of the baseline design. Optimization results show a reduction in the objective function of about 30 per cent. A key accomplishment of this paper is the decoupling of the analysis problem and the optimization problems using response surface methods, which should encourage the use of optimization methods by the helicopter industry.

Ganguli, R.

2002-11-01

158

Effect of Phase on Human Responses to Vertical Whole-Body Vibration and SHOCK—ANALYTICAL Investigation  

NASA Astrophysics Data System (ADS)

The effect of the “phase” on human responses to vertical whole-body vibration and shock has been investigated analytically using alternative methods of predicting subjective responses (using r.m.s., VDV and various frequency weightings). Two types of phase have been investigated: the effect of the relative phase between two frequency components in the input stimulus, and the phase response of the human body. Continuous vibrations and shocks, based on half-sine and one-and-a-half-sine accelerations, each of which had two frequency components, were used as input stimuli. For the continuous vibrations, an effect of relative phase was found for the vibration dose value (VDV) when the ratio between two frequency components was three: about 12% variation in the VDV of the unweighted acceleration was possible by changing the relative phase. The effect of the phase response of the body represented by frequency weightings was most significant when the frequencies of two sinusoidal components were about 3 and 9 Hz. With shocks, the effect of relative phase was observed for all stimuli used. The variation in the r.m.s. acceleration and in the VDV caused by variations in the relative phase varied between 3 and 100%, depending on the nature of stimulus and the frequency weighting. The phase of the frequency weightings had a different effect on the r.m.s. and the VDV.

MATSUMOTO, Y.; GRIFFIN, M. J.

2002-03-01

159

Low back pain in drivers exposed to whole body vibration: analysis of a dose-response pattern  

Microsoft Academic Search

Objective: Analysis of a dose-response pattern between exposure to whole body vibration (WBV) and low back pain (LBP) in a group of drivers. Methods: This study assessed individual factors, work- related risk factors, various LBP outcome measures and LBP disability in a group of drivers (n = 571) approached at baseline (T0), as well as the WBV magnitude of a

I J H Tiemessen; C T J Hulshof; M H W Frings-Dresen

2008-01-01

160

Two-dimensional vibrational spectroscopy. I. Theoretical calculation of the nonlinear Raman response function of CHCl3  

NASA Astrophysics Data System (ADS)

The two-dimensional Raman response function of CHCl3 is theoretically considered with interpretations of each peak in terms of the associated vibrational transition pathways. In order to numerically calculate the 2D Raman spectrum, ab initio calculations of necessary quantities, such as the first- and second-order derivatives of the molecular polarizability with respect to vibrational coordinates and cubic potential anharmonic coefficients, were carried out by using the basis set 6-311++G(2df,2pd) at the Hartree-Fock level. Quantitative comparison between the two nonlinear response functions associated with the mechanical and electronic anharmonicities shows that the 2D Raman response from the high-frequency intramolecular vibrational modes of CHCl3 is mainly determined by the mechanical (potential) anharmonicity contributions. On the other hand, it is found that the two distinctive contributions originating from the mechanical and electronic anharmonicities interfere in the low-frequency region of the 2D spectrum. Overall, it is suggested that the high-frequency 2D Raman spectrum could provide a map of the mechanical anharmonic mode couplings. We briefly discuss how the 2D Raman spectrum can be used to elucidate the potential energy hypersurface and in turn to study the intramolecular vibrational energy redistribution process.

Hahn, Sangjoon; Park, Kisam; Cho, Minhaeng

1999-09-01

161

Dynamics of the head-neck complex in response to the trunk horizontal vibration: modeling and identification.  

PubMed

Although many studies exist concerning the influence of seat vibration on the head in the seated human body, the dynamic response of the head-neck complex (HNC) to the trunk vibration has not been well investigated. Little quantitative knowledge exists about viscoelastic parameters of the neck. In this study, the dynamics of the HNC is identified when it is exposed to the trunk horizontal (fore-and-aft) vibration. The frequency response functions between the HNC angular velocity and the trunk horizontal acceleration, corresponding to four volunteers, are obtained in the frequency range of 0.5 Hz to 10 Hz. A fourth-order mathematical model, derived by considering a double-inverted-pendulum model for the HNC, is designed to simulate the dynamic response of the HNC to the trunk horizontal vibration. The frequency domain identification method is used to determine the coefficients of the mathematical model of the HNC. Good agreement has been obtained between experimental and simulation results. This indicates that the system, similar to the designed fourth-order model, has mainly two resonance frequencies. The viscoelastic parameters of the neck, including the spring and damping coefficients, are then obtained by use of the optimization method. PMID:12968578

Fard, Mohammad A; Ishihara, Tadashi; Inooka, Hikaru

2003-08-01

162

FLUIDELASTIC ANALYSIS OF TUBE BUNDLE VIBRATION IN CROSS-FLOW  

Microsoft Academic Search

Tube bundles in cross-flow vibrate in response to motion-induced fluid-dynamic forces; hence, the resultant motions are considered to be a fluidelastic vibration. The characteristics of the vibration depend greatly on the features of the fluid-dynamic forces and the structure of the tube bundle. Therefore, in this study, the equations of motion of the tube bundle are derived. From the viewpoint

H. Tanaka; K. Tanaka; F. Shimizu; S. Takahara

2002-01-01

163

Effects of eccentricity and order of vibration modes on the inelastic seismic response of 3D steel structures  

NASA Astrophysics Data System (ADS)

In torsionally coupled buildings, the total response of the structure is the result of the translational displacement of the story's center of stiffness and the displacement due to the roof's rotation. In structures with high eccentricity, the effect of the floor's rotation in the total response is considerable. The order of vibration modes is another important parameter that changes the contribution of the different translational and rotational modes in the total response. To explore the effects of eccentricity and the order of vibration modes on the total response, a number of 3-D steel moment-resistant frames with 4, 8, and 12 stories, with different eccentricities and plans, were considered. The structures were subjected to bidirectional seismic inputs so that their peak ground accelerations were scaled to 0.4g, 0.6g, and 0.8g. Increasing the eccentricity of the structure increases the participation of rotation in the total response. Furthermore, in torsionally flexible structures, where the first or second mode of vibration is a torsional mode, the contribution of the floor's rotation can be even greater. In some cases, the displacement of exterior columns is primarily the result of the floor's rotation. This suggests that to efficiently dampen the seismic displacement of such structures, the rotational mode of the building should be controlled.

P. Sharifi, Naser; Sakulich, Aaron R.

2014-04-01

164

Model Order Reduction for Prediction of Turbine Engine Rotor Vibration Response in Presence of Parametric Uncertainties  

NASA Astrophysics Data System (ADS)

Statistical inhomogeneity of material properties, variations in nominal geometry, manufacturing tolerances, operational wear lead to uncertainties in the parameters associated with FE models of turbine engine rotors and consequently to uncertainties in their vibration response. Reliable assessment of the rotor system behavior cannot be made unless the effects of such uncertainties are understood and quantified. In practical situations the parametric probabilistic approach is the first choice to employ in that context yielding efficient algorithms with feasible implementations. A set of measured or estimated experimentally random parameters is repeatedly propagated through rotor models in Monte-Carlo simulations, which would pose a formidable computational task if the full order high-fidelity finite element (FE) models were utilized. The objective of this dissertation is to decrease the expense of analyzing systems modified in the parametric space by developing accurate model reduction computational techniques suitable for repeated analysis, in particular addressing the problem of large variations in nominal geometry. The first part of the dissertation is concerned with the structural blade mistuning problem. The existing projection based model order reduction techniques capable to numerically characterize variations in nominal geometry of periodic structures are examined, a method generating very compact reduced order models (ROM) based on correction, as opposed to expansion, of the modal subspace is selected and its limitations are analyzed. A new algorithm drawing on optimal preconditioned iterative methods for generalized eigenvalue problem is introduced to address its deficiencies. Both techniques are combined in a stochastic simulation framework to analyze the effect of random mistuning on geometrically modified bladed disks, where random parameter variation in blade properties is introduced in modal space at component level. A family of benchmark problems on an industrial scale bladed disk model are utilized in a comparative study assessing the amount of computational effort and storage, scalability and accuracy as well as providing insight on underlying physical phenomena. In the second part of dissertation a new computational technique is proposed focusing on prediction of the effects of uncertainty in rotor assembly inter-stage geometry on global vibration response. The algorithm stands apart from the traditional modal projection based framework employing harmonic truncation only. It is shown that decent performance can be achieved due to reliance on sparse matrix linear algebra and sampling of small parametric space. Particular emphasis is given to the computational efficiency of ROM update. Accuracy and performance of the technique is illustrated with representative simulation examples over a practical range of geometrical parameter variations and operational conditions.

Ganine, Vladislav

165

Atomic lattice structure and continuum plate theories for the vibrational characteristics of graphenes  

NASA Astrophysics Data System (ADS)

This paper is concerned with the equivalent extensional and flexural rigidities of a single layer graphene sheet by treating it as a plane lattice structure made of tightly packed carbon atoms into an array of honeycomb-shaped cells. Each carbon atom is modeled as a node with concentrated atomic mass and prescribed six degrees of freedom. The covalent bond between adjacent carbon atoms provides axial, bending, and torsional stiffness. Using the Poisson's ratio of 0.16 and thickness of 3.4 Å, the equivalent Young's moduli are found to be approximately 0.112 TPa for bending and in the range of 1.03-1.04 TPa for in-plane modes. Subsequently, the graphene structure is simulated by a classical plate with prescribed geometric and mechanical properties. The in-plane and out-of-plane free vibration analyses of the rectangular plate provide the natural frequencies and associated mode shapes. Results are compared with eigen analyses of the lattice structure model for different sizes of graphene. Examples are considered to show close agreement in the results from these two methods. Mode shapes reveal that the lattice structure model shows symmetry about the horizontal and vertical axes and also about the diagonals.

Arghavan, S.; Singh, A. V.

2011-10-01

166

Influence of Resistance Load on Electromyography Response to Vibration Training with Sub-maximal Isometric Contractions  

Microsoft Academic Search

The purpose of this study was to assess the effect of direct vibration during two sub-maximal isometric loading conditions on electromyographic output. Sixteen participants performed isometric knee extensions, at an angle of 150°, under four conditions in random order: 1) a load of 10% one repetition maximum (1 RM) with no vibration (10%+NV); 2) a load of 30% 1RM with

Jin Luo; Brian P. McNamara; Kieran Moran

2007-01-01

167

Towards higher accuracy for ECM hybridized with low-frequency vibrations using the response surface methodology  

Microsoft Academic Search

The present work addresses the improvement of machining accuracy in ECM by hybridizing the process by low-frequency vibrations. The study highlights the development of mathematical models for correlating the inter relationships of various machining parameters such as applied voltage, feed rate, back pressure and vibration amplitude on overcut and conicity for achieving high controlled accuracy. This work is based on

S. J. Ebeid; M. S. Hewidy; T. A. El-Taweel; A. H. Youssef

2004-01-01

168

Modeling and Analysis of Composite Wing Sections for Improved Aeroelastic and Vibration Characteristics Using Smart Materials  

NASA Technical Reports Server (NTRS)

The objective of this research is to develop analysis procedures to investigate the coupling of composite and smart materials to improve aeroelastic and vibratory response of aerospace structures. The structural modeling must account for arbitrarily thick geometries, embedded and surface bonded sensors and actuators and imperfections, such as delamination. Changes in the dynamic response due to the presence of smart materials and delaminations is investigated. Experiments are to be performed to validate the proposed mathematical model.

Chattopadhyay, Aditi

1996-01-01

169

Influence of resonators on the acoustic and propulsion performance characteristics of a ramjet ejector chamber under conditions with vibration hydrogen combustion  

NASA Astrophysics Data System (ADS)

The influence of acoustic resonators on the acoustic and propulsion performance characteristics of a ramjet ejector chamber under conditions with vibration hydrogen combustion was experimentally examined. In the study, resonators having identical throats and different cavity diameters were used. For fixed-volume resonators the best propulsion performance characteristics were achieved in the case in which the cavity diameter differed little from the resonator throat diameter.

Potapkin, A. V.; Moskvichev, D. Yu.

2008-09-01

170

Relationship between measured apparent mass and seat-to-head transmissibility responses of seated occupants exposed to vertical vibration  

NASA Astrophysics Data System (ADS)

The "to-the-body" and "through-the-body" biodynamic response functions of the seated human body exposed to vertical vibration are measured and analyzed in an attempt to identify relationships between the apparent mass and seat-to-head transmissibility measures. The experiments involved 12 male subjects exposed to three magnitudes of whole-body vertical random vibration (0.25,0.5,1.0 m/s 2 rms acceleration) in the 0.5-15 Hz frequency range, and seated with three back support conditions (none, vertical and inclined), and two different hands positions (hands in lap and hands on the steering wheel). The vertical apparent mass and seat-to-head transmissibility responses were acquired during the experiments, where the head acceleration was measured using a light and adjustable helmet-strap mounted accelerometer. The results showed that both the measured responses show good agreements in the primary resonances, irrespective of the back support condition, while considerable differences between the normalized apparent mass and seat-to-head transmissibility could be seen in the secondary resonance range for the two back supported postures. The seat-to-head transmissibility responses are further shown to be relatively sensitive to back supported postures compared with that of apparent mass responses. Relatively stronger effects of hands position were observed on the seat-to-head transmissibility responses compared with the apparent mass responses under back supported conditions. From the results, it is further concluded that seat-to-head transmissibility emphasizes the biodynamic response in the vicinity of the secondary resonance compared to the apparent mass. The seat-to-head transmissibility measure is thus considered to be more appropriate for describing seated body response to higher frequency vibration.

Wang, W.; Rakheja, S.; Boileau, P.-É.

2008-07-01

171

Energy harvesting and vibration control using piezoelectric elements and a nonlinear approach  

Microsoft Academic Search

The piezoelectric materials, as the most widely used functional materials in smart structures, have many outstanding advantages for sensors and actuators, especially in vibration control and energy harvesting, because of their excellent mechanical-electrical coupling characteristics and frequency response characteristics. Semi-active vibration control based on state switching and pulse switching, have been receiving much attention over the past decade because of

J. H. Qiu; H. L. Ji; H. Shen

2009-01-01

172

Active Inertial Vibration Isolators And Dampers  

NASA Technical Reports Server (NTRS)

Report describes development of active inertial vibration isolators and dampers in which actuators electromagnet coils moving linearly within permanent magnetic fields in housings, somewhat as though massive, low-frequency voice coils in loudspeakers. Discusses principle of operation, electrical and mechanical considerations in design of actuators, characteristics of accelerometers, and frequency responses of control systems. Describes design and performance of one- and three-degree-of-freedom vibration-suppressing system based on concept.

Laughlin, Darren; Blackburn, John; Smith, Dennis

1994-01-01

173

Vibration analysis of a new polymer quartz piezoelectric crystal sensor for detecting characteristic materials of volatility liquid  

NASA Astrophysics Data System (ADS)

We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance (QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 ?m. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fsp of 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fsp was found and subsequently became one of the most important parameters in the new sensor design.

Gu, Yu; Li, Qiang; Xu, Bao-Jun; Zhao, Zhe

2014-01-01

174

Quasi-Static and Dynamic Response Characteristics of F-4 Bias-Ply and Radial-Belted Main Gear Tires  

NASA Technical Reports Server (NTRS)

An investigation was conducted at Langley Research Center to determine the quasi-static and dynamic response characteristics of F-4 military fighter 30x11.5-14.5/26PR bias-ply and radial-belted main gear tires. Tire properties were measured by the application of vertical, lateral, and fore-and-aft loads. Mass moment-of-inertia data were also obtained. The results of the study include quasi-static load-deflection curves, free-vibration time-history plots, energy loss associated with hysteresis, stiffness and damping characteristics, footprint geometry, and inertia properties of each type of tire. The difference between bias-ply and radial-belted tire construction is given, as well as the advantages and disadvantages of each tire design. Three simple damping models representing viscous, structural, and Coulomb friction are presented and compared with the experimental data. The conclusions discussed contain a summary of test observations.

Davis, Pamela A.

1997-01-01

175

Damage identification and health monitoring of structural and mechanical systems from changes in their vibration characteristics: A literature review  

SciTech Connect

This report contains a review of the technical literature concerning the detection, location, and characterization of structural damage via techniques that examine changes in measured structural vibration response. The report first categorizes the methods according to required measured data and analysis technique. The analysis categories include changes in modal frequencies, changes in measured mode shapes (and their derivatives), and changes in measured flexibility coefficients. Methods that use property (stiffness, mass, damping) matrix updating, detection of nonlinear response, and damage detection via neural networks are also summarized. The applications of the various methods to different types of engineering problems are categorized by type of structure and are summarized. The types of structures include beams, trusses, plates, shells, bridges, offshore platforms, other large civil structures, aerospace structures, and composite structures. The report describes the development of the damage-identification methods and applications and summarizes the current state-of-the-art of the technology. The critical issues for future research in the area of damage identification are also discussed.

Doebling, S.W.; Farrar, C.R.; Prime, M.B.; Shevitz, D.W.

1996-05-01

176

Bonding, vibrational, and electrical characteristics of CdS nanostructures embedded in polyvinyl alcohol matrix  

SciTech Connect

CdS nanocomposites have been grown in polyvinyl alcohol matrix by a chemical synthesis process. The transmission electron micrographs of nanocomposites synthesized at 70-90 deg. C temperature showed the growth of needlelike and junctionlike nanostructures. X-ray photoelectron spectroscopy analysis revealed the growth of stoichiometric CdS without the formation of any intermediate phases at the CdS-polyvinyl alcohol interface. Raman spectra of first order longitudinal optical phonon peak has been analyzed using phonon dispersion model to detect the surface phonon modes in CdS nanoneedles and wires. The origin of negative differential resistance behavior in current-voltage characteristics for junctionlike CdS nanocomposites has been discussed.

Mondal, S. P.; Dhar, A.; Ray, S. K. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur-721 302 (India); Chakraborty, A. K. [Laboratory for Mechanical Systems Engineering EMPA, Duebendorf, Zurich, CH-8600 (Switzerland)

2009-04-15

177

Bending, Vibration and Buckling Response of Conventional and Modified Euler-Bernoulli and Timoshenko Beam Theories Accounting for the von Karman Geometric Nonlinearity  

E-print Network

Hamilton’s principle. These equations form the basis of investigations to determine certain microstructural length scales on the bending, vibration and buckling response of beams used in micro- and nano-devices. (2) Analytical solutions of the conventional...

Mahaffey, Patrick Brian

2013-08-07

178

Isotope effects in hydrogen-bonded complexes. Calculation of geometrical and vibrational characteristics of asymmetric isotopologues of [F(HF)2]-.  

PubMed

The geometrical and vibrational characteristics of isolated H-bonded anionic complexes [FHFDF](-), [FHFTF](-), and [FDFTF](-) are calculated quantum-mechanically. The four-dimensional anharmonic vibrational problems are solved by the variational method using the potential energy and dipole moment surfaces calculated in the MP2/6-311++G(3df,3pd) approximation with the basis set superposition error taken into account. Changes in the bond lengths of molecular fragments LF (L = H, D, T) and in the distances between the F(-) anion and the centers of mass of LF are used as the vibrational coordinates. For each isotopologue, the vibrational energy levels, the transition frequencies and absolute intensities for the H-bond and L-F stretching vibrations are determined. To study the isotope effects on the geometrical parameters, the values of internuclear separations and the asymmetry parameter of the F(-)···L-F bridges, averaged over the ground state and several excited vibrational states, are calculated, as well as their standard deviations. The calculations revealed an extremely strong influence of anharmonic coupling between different vibrations on the absorption intensities and a significant mass-dependence of spectroscopic and structural parameters. The geometry and harmonic frequencies of KH(2)F(3), KD(2)F(3), and KHDF(3) are also calculated at a lower ab initio level. The results obtained for [FHFDF](-), [FHFTF](-), and [FDFTF](-) are compared with the available experimental data and the results of earlier calculations of the symmetric complexes [F(HF)(2)](-), [F(DF)(2)](-), and [F(TF)(2)](-) and complexes containing a positive K-meson. PMID:21695326

Bulychev, V P; Buturlimova, M V; Tokhadze, K G

2011-08-21

179

Vibration characteristics of Z-ring-stiffened 60 deg conical shell models of a planetary entry spacecraft  

NASA Technical Reports Server (NTRS)

An experimental investigation of the vibration characteristics of a 60 deg conical shell model of a planetary entry vehicle is described and the results presented. Model configurations include the shell with or without one or two Z-ring stiffeners and with or without a simulated payload. Tests were conducted with the model clamped at the small diameter and with the model suspended at the simulated payload. Additionally, calculated results obtained from application of several analytical procedures reported in the literature are presented together with comparisons between experimental and calculated frequencies and meridional mode shapes. Generally, very good frequency agreement between experimental and calculated results was obtained for all model configurations. For small values of circumferential mode number, however, the frequency agreement decreased as the number of ring stiffeners increased. Overall agreement between experimental and calculated mode shapes was generally good. The calculated modes usually showed much larger curvatures in the vicinity of the rings than were observed in the experimentally measured mode shapes. Dual resonances associated with modal preference were noted for the shell without Z-ring stiffeners, whereas the addition of stiffeners produced resonances for which the model responded in two or more modes over different sections of the shell length.

Naumann, E. C.; Mixon, J. S.

1971-01-01

180

Investigation of Dynamic Force/Vibration Transmission Characteristics of Four-Square Type Gear Durability Test Machines  

NASA Technical Reports Server (NTRS)

In this study, design requirements for a dynamically viable, four-square type gear test machine are investigated. Variations of four-square type gear test machines have been in use for durability and dynamics testing of both parallel- and cross-axis gear set. The basic layout of these machines is illustrated. The test rig is formed by two gear pairs, of the same reduction ratio, a test gear pair and a reaction gear pair, connected to each other through shafts of certain torsional flexibility to form an efficient, closed-loop system. A desired level of constant torque is input to the circuit through mechanical (a split coupling with a torque arm) or hydraulic (a hydraulic actuator) means. The system is then driven at any desired speed by a small DC motor. The main task in hand is the isolation of the test gear pair from the reaction gear pair under dynamic conditions. Any disturbances originated at the reaction gear mesh might potentially travel to the test gearbox, altering the dynamic loading conditions of the test gear mesh, and hence, influencing the outcome of the durability or dynamics test. Therefore, a proper design of connecting structures becomes a major priority. Also, equally important is the issue of how close the operating speed of the machine is to the resonant frequencies of the gear meshes. This study focuses on a detailed analysis of the current NASA Glenn Research Center gear pitting test machine for evaluation of its resonance and vibration isolation characteristics. A number of these machines as the one illustrated has been used over last 30 years to establish an extensive database regarding the influence of the gear materials, processes surface treatments and lubricants on gear durability. This study is intended to guide an optimum design of next generation test machines for the most desirable dynamic characteristics.

Kahraman, Ahmet

2002-01-01

181

The negative and positive electrorheological behavior and vibration damping characteristics of colemanite and polyindene/colemanite conducting composite  

NASA Astrophysics Data System (ADS)

In this study, the electrorheological (ER) properties of colemanite and polyindene (94.8% PIn)/colemanite (5.2%) conducting composite were investigated by dispersion in silicone oil (SO). The zeta (?)-potentials and antisedimentation ratios of the materials were determined. Some parameters which affect the ER properties of all the dispersions such as the volume fraction, electric field strength (E), shear rate, frequency and temperature were investigated. The rather unusual behavior known as the negative ER effect was observed for colemanite/SO above E = 1.5 kV mm-1 and for PIn/colemanite/SO under all values of the electric field strength even at high volume fraction. This negative ER response was converted to a positive one by the addition of non-ionic surfactant. Furthermore, glycerol was used as a polar promoter and observed to enhance the ER activity of the colemanite/SO system. Creep-recovery tests were applied to all the dispersions studied to investigate their behavior under sustained shear stress. Finally, 28% and 30% vibration damping capacities were achieved using an automobile shock absorber for the glycerol/colemanite/SO and non-ionic surfactant/PIn/colemanite/SO systems under the E = 0.17 kV mm-1 condition, respectively.

Cetin, B.; Unal, H. I.; Erol, O.

2012-12-01

182

Development of a chaotic nonlinear tuned mass damper for optimal vibration response  

NASA Astrophysics Data System (ADS)

In this article an efficient method is developed for optimal design of a nonlinear tuned mass damper (N-TMD) system. Using several horizontal linear springs coming into action sequentially, system nonlinearity can be achieved with ease as a novel method. Friction force between tuned mass and the structure is variably produced by a vertical linear spring that follows a specified controlling curved path allowing reduction of the desired tuned mass. Chaotic behavior of the introduced tuned mass is investigated in terms of the existing parameters in the system. Lyapunov characteristic exponents are determined to demonstrate the chaotic behavior of the system. It is confirmed by comparison that the proposed scheme is able to retrofit structures in a superior way than some other devices such as multiple tuned mass damper systems. The optimization procedure is performed by sequential Simplex algorithm, while Newmark's beta method for step by step integration is used to find the dynamic response of the structure.

Farshi, Behrooz; Assadi, Abbas

2011-11-01

183

Static and free-vibrational response of semi-circular graphite-epoxy frames with thin-walled open sections  

NASA Technical Reports Server (NTRS)

Experiments were conducted to measure the three-dimensional static and free vibrational response of two graphite-epoxy, thin-walled, open section frames. The frames are semi-circular with a radius of three feet, and one specimen has an I cross section and the other has a channel cross section. The flexibility influence coefficients were measured in static tests for loads applied at midspan with the ends of the specimens clamped. Natural frequencies and modes were determined from vibrational tests for free and clamped end conditions. The experimental data is used to evaluate a new finite element which was developed specifically for the analysis of curved, thin-walled structures. The formulation of the element is based on a Vlasov-type, thin-walled, curved beam theory. The predictions from the finite element program generally correlated well with the experimental data for the symmetric I-specimen. Discrepancies in some of the data were found to be due to flexibility in the clamped end conditions. With respect to the data for the channel specimen, the correlation was less satisfactory. The finite element analysis predicted the out-of-plane response of the channel specimen reasonably well, but large discrepancies occurred between the predicted in-plane response and the experimental data. The analysis predicted a much more compliant in-plane response than was observed in the experiments.

Collins, J. Scott; Johnson, Eric R.

1989-01-01

184

Vibration analysis to improve reliability and reduce failure; Proceedings of the Design Automation Conference, Cincinnati, OH, September 10-13, 1985  

Microsoft Academic Search

Among the topics discussed are: turbomachinery tip rubs and interactive casting resonances; the transverse vibrational characteristics of an externally damaged pipe and performance of vibration monitoring for the prevention of gas turbine airfoil failures. Consideration is also given to: velocity response analysis of a spherical roller bearing; vibration monitoring of large pumps via a remote satellite stations; dynamic edge strain

P. M. Niskode; P. E. Doepker

1985-01-01

185

Experimental damage detection of cracked beams by using nonlinear characteristics of forced response  

NASA Astrophysics Data System (ADS)

Experimental evaluation of the flexural forced vibrations of a steel cantilever beam having a transverse surface crack extending uniformly along the width of the beam was performed, where an actual fatigue crack was introduced instead - as usual - of a narrow slot. The nonlinear aspects of the dynamic response of the beam under harmonic excitation were considered and the relevant quantitative parameters were evaluated, in order to relate the nonlinear resonances to the presence and size of the crack. To this end, the existence of sub- and super-harmonic components in the Fourier spectra of the acceleration signals was evidenced, and their amplitudes were quantified. In particular, the acceleration signals were measured in different positions along the beam axis and under different forcing levels at the beam tip. The remarkable relevance of the above mentioned nonlinear characteristics, and their substantial independence on force magnitude and measurement point were worthily noted in comparison with the behavior of the intact beam. Thus, a reliable method of damage detection was proposed which was based on simple tests requiring only harmonically forcing and acceleration measuring in any point non-necessarily near the crack. Then, the time-history of the acceleration recorded at the beam tip was numerically processed in order to obtain the time-histories of velocity and displacement. The nonlinear features of the forced response were described and given a physical interpretation in order to define parameters suitable for damage detection. The efficiency of such parameters was discussed with respect to the their capability of detecting damage and a procedure for damage detection was proposed which was able to detect even small cracks by using simple instruments. A finite element model of the cantilever beam was finally assembled and tuned in order to numerically simulate the results of the experimental tests.

Andreaus, U.; Baragatti, P.

2012-08-01

186

Influence of supplemental magnesium, tryptophan, vitamin C, and vitamin E on stress responses of pigs to vibration.  

PubMed

Our objectives were to investigate and compare the effects of supplemental Mg, Trp, vitamin E (vit E), and vitamin C (vit C) on stress responses of pigs undergoing transport simulation. In this study, 126 pigs (25.1 +/- 4.4 kg BW) were allocated to one of the six following treatments: 1) negative control (no supplementation); 2) positive control (i.m. injection with 0.5 mg of carazolol/20 kg BW 12 h before vibration, beta-blocker); 3) Trp (additional amount of 6 g/kg of feed for 5 d, as-fed basis); 4) Mg (3 g/L drinking water for 2 d); 5) vit E (additional amount of 150 mg/kg of feed for 21 d, as-fed basis); 6) or vit C (additional amount of 300 mg/kg of feed for 21 d, as-fed basis). Pigs were treated in groups of three, and each treatment was replicated seven times. Feed and water intake were not different among treatments. Heart rate variables (mean, peak, and minimum heart rate, ventricular ectopic beats, and ST elevation of Channels A and B) and heart rate variability were registered from the night before vibration. Pigs were subjected to vibration in a transport simulator (8 Hz, 3 m/s) for 2 h and allowed to recover for 2 h. Generally, the positive control pigs had the lowest heart rate values (mean, peak, minimum heart rate, ST elevation of Channel A; P < 0.05), whereas Mg and Trp decreased ventricular ectopic beats and ST elevation of Channel B, respectively. The effect of vit C and E as vagal stimulators was clearly visible, whereas carazolol and Mg clearly blocked the sympathetic pathways of the autonomic nervous system. During vibration, the negative control pigs lay the least, and Mg pigs the most (P < 0.05). Salivary cortisol concentrations (taken before and after vibration and after recovery) showed that vit E pigs produced the least cortisol during stress periods. Intermediary metabolites (glucose, lactate, creatine kinase, and NEFA) were analyzed in plasma from blood taken before and after vibration. At the two sampling points, the vit E and Mg pigs had the lowest NEFA concentrations (P < 0.05), and the vit E pigs also had the lowest lactate concentrations before vibration. Urine samples were collected before and after vibration to determine catecholamine concentrations; only negative control pigs had an increase (P = 0.04) in epinephrine concentration, despite large individual variation. In general, these results indicate that the supplementation of Trp, Mg, vit E, or vit C improved coping ability of pigs during vibration comparison with the negative control treatment. A muscular injection of carazolol influenced only the heart rate variables. PMID:15956466

Peeters, E; Neyt, A; Beckers, F; De Smet, S; Aubert, A E; Geers, R

2005-07-01

187

The Effect of Vibration on Postural Response of Down Syndrome Individuals on the Seesaw  

ERIC Educational Resources Information Center

In order to better understand the role of proprioception in postural adjustments on unstable surfaces, we analyzed the effect of vibration on the pattern of muscle activity and joint displacements (ankle, knee and hip) of eight intellectually normal participants (control group-CG) and eight individuals with Down syndrome (DS) while balancing on…

Carvalho, Regiane Luz; Almeida, Gil Lucio

2009-01-01

188

EMG and Heart Rate Responses Decline within 5 Days of Daily Whole-Body Vibration Training with Squatting  

PubMed Central

In this study, we examined the acute effects of a 5-day daily whole-body vibration (WBV) training on electromyography (EMG) responses of the m. rectus femoris and m. gastrocnemius lateralis, heart rate (HR, continuously recorded), and blood lactate levels. The purpose of the study was to investigate the adaptation of muscle activity, heart rate and blood lactate levels during 5 days of daily training. Two groups of healthy male subjects performed either squat exercises with vibration at 20 Hz on a side alternating platform (SE+V, n?=?20, age ?=?31.9±7.5 yrs., height ?=?178.8±6.2 cm, body mass ?=?79.2±11.4 kg) or squat exercises alone (SE, n?=?21, age ?=?28.4±7.3 years, height ?=?178.9±7.4 cm, body mass ?=?77.2±9.7 kg). On training day 1, EMG amplitudes of the m. rectus femoris were significantly higher (P<0.05) during SE+V than during SE. However, this difference was no longer statistically significant on training days 3 and 5. The heart rate (HR) response was significantly higher (P<0.05) during SE+V than during SE on all training days, but showed a constant decline throughout the training days. On training day 1, blood lactate increased significantly more after SE+V than after SE (P<0.05). On the following training days, this difference became much smaller but remained significantly different. The specific physiological responses to WBV were largest on the initial training day and most of them declined during subsequent training days, showing a rapid neuromuscular and cardiovascular adaptation to the vibration stimulus. PMID:24905721

Rosenberger, André; Liphardt, Anna-Maria; Bargmann, Arne; Müller, Klaus; Beck, Luis; Mester, Joachim; Zange, Jochen

2014-01-01

189

Random vibration of mechanical and structural systems  

NASA Astrophysics Data System (ADS)

This book addresses random vibration of mechanical and structural systems commonly encountered in aerospace, mechanical, and civil engineering. Techniques are examined for determining probabilistic characteristics of the response of dynamic systems subjected to random loads or inputs and for calculating probabilities related to system performance or reliability. Emphasis is given to applications.

Soong, T. T.; Grigoriu, Mircea

190

Random vibration of mechanical and structural systems  

Microsoft Academic Search

This book addresses random vibration of mechanical and structural systems commonly encountered in aerospace, mechanical, and civil engineering. Techniques are examined for determining probabilistic characteristics of the response of dynamic systems subjected to random loads or inputs and for calculating probabilities related to system performance or reliability. Emphasis is given to applications.

T. T. Soong; Mircea Grigoriu

1993-01-01

191

Acceptance and control of aircraft interior noise and vibration  

NASA Technical Reports Server (NTRS)

Ride quality criteria for noise, vibration, and their combination in the helicopter cabin environment are discussed. Results are presented of laboratory and field studies of passenger responses to interior noise and vibration during the performance of a listening task and during reverie, as well as to the interaction of noise with multi-frequency and multi-axis vibration. A study of means for reducing helicopter interior noise based on analytical, experimental and flight studies of the near-field noise source characteristics of the aircraft, the transmission of noise through aircraft structures and the attenuation of noise by various noise control treatments is then presented which has resulted in a reduction of 3 dB in helicopter cabin noise. Finally, a model under development to evaluate passenger acceptance of a helicopter noise and vibration environment is indicated which incorporates the observed noise and vibration effects on comfort and is expected to provide insights for more effective noise and vibration control.

Stephens, D. G.; Leatherwood, J. D.

1980-01-01

192

Dose-response relation for vascular disorders induced by vibration in the fingers of forestry workers  

Microsoft Academic Search

OBJECTIVES--To study the relation between the prevalence of vascular disorders (white finger) and vibration exposure in a group of 222 forestry workers, of whom 164 (73.9%) had work experience limited to antivibration (AV) chain saws only and 58 (26.1%) had operated both non-AV and AV chain saws. METHODS--The chain saw operators and 195 control workers never exposed to hand transmitted

M Bovenzi; A Franzinelli; R Mancini; M G Cannavà; M Maiorano; F Ceccarelli

1995-01-01

193

Dynamic responses and vibration control of the transmission tower-line system: a state-of-the-art review.  

PubMed

This paper presented an overview on the dynamic analysis and control of the transmission tower-line system in the past forty years. The challenges and future developing trends in the dynamic analysis and mitigation of the transmission tower-line system under dynamic excitations are also put forward. It also reviews the analytical models and approaches of the transmission tower, transmission lines, and transmission tower-line systems, respectively, which contain the theoretical model, finite element (FE) model and the equivalent model; shows the advances in wind responses of the transmission tower-line system, which contains the dynamic effects under common wind loading, tornado, downburst, and typhoon; and discusses the dynamic responses under earthquake and ice loads, respectively. The vibration control of the transmission tower-line system is also reviewed, which includes the magnetorheological dampers, friction dampers, tuned mass dampers, and pounding tuned mass dampers. PMID:25105161

Chen, Bo; Guo, Wei-hua; Li, Peng-yun; Xie, Wen-ping

2014-01-01

194

Correlation of finite-element structural dynamic analysis with measured free vibration characteristics for a full-scale helicopter fuselage  

NASA Technical Reports Server (NTRS)

The correlation achieved with each program provides the material for a discussion of modeling techniques developed for general application to finite-element dynamic analyses of helicopter airframes. Included are the selection of static and dynamic degrees of freedom, cockpit structural modeling, and the extent of flexible-frame modeling in the transmission support region and in the vicinity of large cut-outs. The sensitivity of predicted results to these modeling assumptions are discussed. Both the Sikorsky Finite-Element Airframe Vibration analysis Program (FRAN/Vibration Analysis) and the NASA Structural Analysis Program (NASTRAN) have been correlated with data taken in full-scale vibration tests of a modified CH-53A helicopter.

Kenigsberg, I. J.; Dean, M. W.; Malatino, R.

1974-01-01

195

Multicomponent stimulus interactions observed in basilar-membrane vibration in the basal region  

E-print Network

Multicomponent stimulus interactions observed in basilar-membrane vibration in the basal region-membrane vibration at the 3­4-mm region of the chinchilla cochlea with a characteristic frequency between 6.5 and 8- sion effects are studied here. Although the response of the auditory nerve AN to various stimuli

Czajkowski, Cynthia

196

Responsibility attitudes and interpretations are characteristic of obsessive compulsive disorder  

Microsoft Academic Search

The cognitive–behavioural theory of Obsessive Compulsive Disorder (OCD) proposes that a key factor influencing obsessional behaviour is the way in which the intrusive cognitions are interpreted. The present paper reports an investigation of links between clinical symptoms (of anxiety, depression and obsessionality) and responsibility beliefs. These beliefs include not only measures of general responsibility attitudes (assumptions) but also more specific

P. M. Salkovskis; A. L. Wroe; A. Gledhill; N. Morrison; E. Forrester; C. Richards; M Reynolds; S Thorpe

2000-01-01

197

LINKING WITHIN-FIELD CROP RESPONSE WITH SOIL CHARACTERISTICS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Management zones for precision farming can be determined by identifying areas where soil, water, and management factors result in similar crop responses. Given the spatial distribution of LAI of a field, factors determining response patterns may be obtained via inversion of a model linking environme...

198

Estimates of site response based on spectral ratio between horizontal and vertical components of ambient vibrations in the source zone of 2001 Bhuj earthquake  

NASA Astrophysics Data System (ADS)

We investigated the site response characteristics of Kachchh rift basin over the meizoseismal area of the 2001, Mw 7.6, Bhuj (NW India) earthquake using the spectral ratio of the horizontal and vertical components of ambient vibrations. Using the available knowledge on the regional geology of Kachchh and well documented ground responses from the earthquake, we evaluated the H/V curves pattern across sediment filled valleys and uplifted areas generally characterized by weathered sandstones. Although our H/V curves showed a largely fuzzy nature, we found that the hierarchical clustering method was useful for comparing large numbers of response curves and identifying the areas with similar responses. Broad and plateau shaped peaks of a cluster of curves within the valley region suggests the possibility of basin effects within valley. Fundamental resonance frequencies (f0) are found in the narrow range of 0.1-2.3 Hz and their spatial distribution demarcated the uplifted regions from the valleys. In contrary, low H/V peak amplitudes (A0 = 2-4) were observed on the uplifted areas and varying values (2-9) were found within valleys. Compared to the amplification factors, the liquefaction indices (kg) were able to effectively indicate the areas which experienced severe liquefaction. The amplification ranges obtained in the current study were found to be comparable to those obtained from earthquake data for a limited number of seismic stations located on uplifted areas; however the values on the valley region may not reflect their true amplification potential due to basin effects. Our study highlights the practical usefulness as well as limitations of the H/V method to study complex geological settings as Kachchh.

Natarajan, Thulasiraman; Rajendran, Kusala

2015-02-01

199

Study of start-up vibration response for oil whirl, oil whip and dry whip  

NASA Astrophysics Data System (ADS)

Oil whip induces self-excited vibration in fluid-handling machines and causes self-excited reverse precessional full annular rub, known as "dry whip", which is a secondary phenomenon resulting from a primary cause, that is, "coexistence of oil whip and dry whip". For predicting these instabilities, the clues are hidden in start-up vibration signals of these kinds of machines. This paper presents a method for predicting these kinds of instabilities. First, a Hilbert spectrum combining a full spectrum, which is named the "full Hilbert spectrum", is developed to reveal the whole process. Next, the transient position of a shaft centerline combining an acceptance region is introduced to predict instability at an early stage. The results presented in this study amply demonstrate the transition from stability to instability and the behavior of fluid-induced instability and rub in rotor systems. By this finding, bearing designers can completely understand these instability phenomena existing in fluid-handling machines. As a result, the control parameter for designing controllable bearings can be obtained and the instability problems can be resolved. Consequently, these findings are worth noting.

Fan, Chen-Chao; Syu, Jhe-Wei; Pan, Min-Chun; Tsao, Wen-Chang

2011-11-01

200

Characteristics of near response cells projecting to the oculomotor nucleus.  

PubMed

1. Previous work has shown neurons just dorsal and lateral to the oculomotor nucleus that increase their firing rate with increases in the angle of ocular convergence. It has been suggested that the output of these midbrain near response cells might provide the vergence command needed by the medial rectus motoneurons. However, lens accommodation ordinarily accompanies convergence, and a subsequent study showed that only about one-half of these midbrain near response cells carried a signal related exclusively to vergence. One hypothesis suggested by this finding is that this subgroup of neurons might have a unique role in providing a "pure" vergence signal to the medial rectus motoneurons. 2. In the present study extracellular recordings were made from midbrain near response cells in monkeys while eye position and lens accommodation were measured. The monkeys viewed targets through an optical system that allowed the accommodative and ocular vergence demands to be manipulated independently. This approach was used to produce a partial dissociation of accommodative and vergence responses, so that an accommodative and vergence coefficient could be determined for each cell, by the use of the following equation FR = R0 + kda x AR + kdv x CR where FR is the firing rate of the near response cell, R0 is the predicted firing rate for a distant target, kda is the (dissociated) accommodation coefficient, AR is the accommodative response, kdv is the (dissociated) vergence coefficient, and CR is the convergence response. 3. The vergence and accommodation coefficients were determined for a large number of midbrain near response cells, including a subset that could be antidromically activated from the medial rectus subdivisions of the oculomotor nucleus. Some near response neurons were found with signals related exclusively to convergence (i.e., kdv greater than 0 and kda = 0), whereas several others had signals related exclusively to lens accommodation (i.e., kda greater than 0 and kdv = 0). The majority of the near response cells had signals related to both responses (i.e., kda not equal to 0 and kdv not equal to 0). Furthermore, the vergence and accommodation coefficients of near response cells appeared to be continuously distributed. Some cells had negative accommodation or vergence coefficients. 4. The 17 near response cells that could be antidromically activated from the oculomotor nucleus presumably provide vergence signals to the medial rectus motoneurons. Although all had positive vergence coefficients, only four of these cells carried signals that were related exclusively to vergence.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1588393

Zhang, Y; Mays, L E; Gamlin, P D

1992-04-01

201

Experimental IR and Raman spectra and quantum chemical studies of molecular structures, conformers and vibrational characteristics of L-ascorbic acid and its anion and cation  

NASA Astrophysics Data System (ADS)

IR and spectra of the L-ascorbic acid ( L-AA) also known as vitamin C have been recorded in the region 4000-50 cm -1. In order to make vibrational assignments of the observed IR and Raman bands computations were carried out by employing the RHF and DFT methods to calculate the molecular geometries and harmonic vibrational frequencies along with other related parameters for the neutral L-AA and its singly charged anionic ( L-AA -) and cationic ( L-AA +) species. Significant changes have been found for different characteristics of a number of vibrational modes. The four ?(O-H) modes of the L-AA molecule are found in the order ?(O 9-H 10) > ?(O 19-H 20) > ?(O 7-H 8) > ?(O 14-H 15) which could be due to complexity of hydrogen bonding in the lactone ring and the side chain. The C dbnd O stretching wavenumber ( ?46) decreases by 151 cm -1 in going from the neutral to the anionic species whereas it increases by 151 cm -1 in going from the anionic to the cationic species. The anionic radicals have less kinetic stabilities and high chemical reactivity as compared to the neutral molecule. It is found that the cationic radical of L-AA is kinetically least stable and chemically most reactive as compared to its neutral and anionic species.

Yadav, R. A.; Rani, P.; Kumar, M.; Singh, R.; Singh, Priyanka; Singh, N. P.

2011-12-01

202

Nonlinear terahertz spectroscopy of electronic and vibrational responses in condensed matter systems  

E-print Network

In this work, I describe experiments utilizing high-field terahertz (THz) pulses to initiate nonlinear responses in several classes of materials. We have developed several methods for interrogating the nonlinear THz response ...

Hwang, Harold Young

2012-01-01

203

Vibration analyzer  

NASA Technical Reports Server (NTRS)

The invention relates to monitoring circuitry for the real time detection of vibrations of a predetermined frequency and which are greater than a predetermined magnitude. The circuitry produces an instability signal in response to such detection. The circuitry is particularly adapted for detecting instabilities in rocket thrusters, but may find application with other machines such as expensive rotating machinery, or turbines. The monitoring circuitry identifies when vibration signals are present having a predetermined frequency of a multi-frequency vibration signal which has an RMS energy level greater than a predetermined magnitude. It generates an instability signal only if such a vibration signal is identified. The circuitry includes a delay circuit which responds with an alarm signal only if the instability signal continues for a predetermined time period. When used with a rocket thruster, the alarm signal may be used to cut off the thruster if such thruster is being used in flight. If the circuitry is monitoring tests of the thruster, it generates signals to change the thruster operation, for example, from pulse mode to continuous firing to determine if the instability of the thruster is sustained once it is detected.

Bozeman, Richard J., Jr. (inventor)

1990-01-01

204

The Impact of Item Format and Examinee Characteristics on Response Times  

ERIC Educational Resources Information Center

Current research on examination response time has focused on tests comprised of traditional multiple-choice items. Consequently, the impact of other innovative or complex item formats on examinee response time is not understood. The present study used multilevel growth modeling to investigate examinee characteristics associated with response time…

Hess, Brian J.; Johnston, Mary M.; Lipner, Rebecca S.

2013-01-01

205

Good Vibrations  

NASA Technical Reports Server (NTRS)

A Small Business Innovation Research (SBIR) sponsorship from NASA's Dryden Flight Research Center, assisted MetroLaser, of Irvine, California, in the development of a self-aligned laser vibrometer system. VibroMet, capable of measuring surface vibrations in a variety of industries, provides information on the structural integrity and acoustical characteristics of manufactured products. This low-cost, easy-to-use sensor performs vibration measurement from distances of up to three meters without the need for adjustment. The laser beam is simply pointed at the target and the system then uses a compact laser diode to illuminate the surface and to subsequently analyze the reflected light. The motion of the surface results in a Doppler shift that is measured with very high precision. VibroMet is considered one of the many behind-the-scenes tools that can be relied on to assure the quality, reliability and safety of everything from airplane panels to disk brakes

2001-01-01

206

A band Lanczos approach for calculation of vibrational coupled cluster response functions: simultaneous calculation of IR and Raman anharmonic spectra for the complex of pyridine and a silver cation.  

PubMed

We describe new methods for the calculation of IR and Raman spectra using vibrational response theory. Using damped linear response functions that incorporate a Lorentzian line-shape function from the outset, it is shown how the calculation of Raman spectra can be carried out through the calculation of a set of vibrational response functions in the same manner as described previously for IR spectra. The necessary set of response functions can be calculated for both vibrational coupled cluster (VCC) and vibrational configuration interaction (VCI) anharmonic vibrational wave-functions. For the efficient and simultaneous calculation of the full set of necessary response functions, a non-hermitian band Lanczos algorithm is implemented for VCC, and a hermitian band Lanczos algorithm is implemented for VCI. It is shown that the simultaneous calculation of several response functions is often advantageous. Sample calculations are presented for pyridine and the complex between pyridine and the silver cation. PMID:23609967

Godtliebsen, Ian H; Christiansen, Ove

2013-07-01

207

Polymerization Parameters Influencing the QCM Response Characteristics of BSA MIP  

PubMed Central

Designing Molecularly Imprinted Polymers for sensing proteins is still a somewhat empirical process due to the inherent complexity of protein imprinting. Based on Bovine Serum Albumin as a model analyte, we explored the influence of a range of experimental parameters on the final sensor responses. The optimized polymer contains 70% cross linker. Lower amounts lead to higher sensitivity, but also sensor response times substantially increase (to up to 10 h) at constant imprinting effect (signal ratio MIP/NIP on quartz crystal microbalance—QCM). However, by shifting the polymer properties to more hydrophilic by replacing methacrylic acid by acrylic acid, part of the decreased sensitivity can be recovered leading to appreciable sensor responses. Changing polymer morphology by bulk imprinting and nanoparticle approaches has much lower influence on sensitivity. PMID:25587416

Phan, Nam V. H.; Sussitz, Hermann F.; Lieberzeit, Peter A.

2014-01-01

208

Ulcerated hemangiomas: Clinical characteristics and response to therapy  

Microsoft Academic Search

Background: Hemangiomas represent the most common benign tumor of infancy, with ulceration its most frequent complication. Objective: Our purpose was to review our experience with this challenging problem by evaluating the clinical features, management, and therapeutic responses of ulcerated hemangiomas. Methods: A retrospective analysis of ulcerated hemangiomas at the University of California, San Francisco outpatient pediatric dermatology clinics and Oakland

Ho Jin Kim; Mary Colombo; Ilona J. Frieden

2001-01-01

209

Inductor flyback characteristic gives voltage regulator fast response  

NASA Technical Reports Server (NTRS)

Voltage regulator alternately connects an inductor in parallel and in series with the input voltage source. This flyback voltage regulator provides a regulated dc voltage to varying loads from a varying dc supply and gives fast response to load and supply changes.

Smith, G. D.

1965-01-01

210

Thermal response and ablation characteristics of light weight ceramic ablators  

NASA Technical Reports Server (NTRS)

An account is given of the thermal performance and ablation characteristics of the NASA-Ames Lightweight Ceramic Ablators (LCAs) in supersonic, high-enthalpy convective environments, which use low density ceramic or carbon fiber matrices as substrates for main structural support, with organic resin fillers. LCA densities are in the 0.224-1.282 g/cu cm range. In-depth temperature data have been obtained to determine thermal penetration depths and conductivity. The addition of SiC and PPMA is noted to significantly improve the ablation performance of LCAs with silica substrates. Carbon-based LCAs are the most mass-efficient at high flux levels.

Tran, Huy K.; Rasky, Daniel J.; Esfahani, Lili

1993-01-01

211

Flow-induced vibration and instability of some nuclear-reactor-system components. [PWR  

SciTech Connect

The high-velocity coolant flowing through a reactor system component is a source of energy that can induce component vibration and instability. In fact, many reactor components have suffered from excessive vibration and/or dynamic instability. The potential for detrimental flow-induced vibration makes it necessary that design engineers give detailed considerations to the flow-induced vibration problems. Flow-induced-vibration studies have been performed in many countries. Significant progress has been made in understanding the different phenomena and development of design guidelines to avoid damaging vibration. The purpose of this paper is to present an overview of the recent progress in several selected areas, to discuss some new results and to indentify future research needs. Specifically, the following areas will be presented: examples of flow-induced-vibration problems in reactor components; excitation mechanisms and component response characteristics; instability mechanisms and stability criteria; design considerations; and future research needs.

Chen, S.S.

1983-01-01

212

Experimental investigation of the vibrational and thermal response of a laser spark plug  

NASA Astrophysics Data System (ADS)

A study was conducted in order to evaluate the external thermal and vibrational effects on the operation of a laser ignition system for internal combustion (IC) engine applications. West Virginia University (WVU) in conjunction with the National Energy Technology Laboratory (NETL) have constructed a prototype laser spark plug which has been designed to mount directly onto the head of a natural gas engine for the purpose of igniting an air/fuel (A/F) mixture in the engine's combustion chamber. To be considered as a viable replacement for the conventional electrode-based ignition system, integrity, durability and reliability must be justified. Thermal and oscillatory perturbations induced upon the ignition system are major influences that affect laser spark plug (LSP) operation and, therefore, quantifying these effects is necessary to further the advancement and development of this technology. The passively q-switched Nd:YAG laser was mounted on Bruel & Kjaer (B&K) Vibration Exciter Type 4808 Shaker in conjunction with at B&K Power Amplifier Type 2719, which was oscillated in 10 Hz intervals from 0 to 60 Hz using a sine wave to mimic natural gas engine operation. The input signal simulated the rotational velocity of the engine operating from 0 to 3600 RPM with the laser mounted in three different axial orientations. The laser assembly was wrapped with medium-temperature heat tape, outfitted with thermocouples and heated from room temperature to 140 ºF to simulate the temperatures that the LSP may experience when installed on an engine. The acceleration of the payload was varied between 50% and 100% of the oscillator's maximum allowable acceleration in each mounting orientation resulting in a total of 294 total setpoints. For each setpoint, pulse width, pulse width variation, q-switch delay, jitter and output energy were measured and recorded. Each of these dependent variables plays a critical role in multi photon ionization and precise control is necessary to limit the variability of these key parameters. Under the influence of thermal and oscillatory perturbations, the q-switch delay of the laser was found to vary significantly. For application on an IC engine, such variation in qswitch delay would result in an ignition timing variation by as much as +/-4.6 crank angle (CA) degrees in the most extreme setpoint on a cycle-to-cycle basis. Every setpoint tested was calculated to be capable of generating a plasma spark in air (>100 GW/cm2), however the resulting focal intensity was found to vary by as much as +/-13 GW/cm2.

Yoder, Gregory S.

213

Wind response characteristics of horizontal axis wind turbines  

NASA Technical Reports Server (NTRS)

It was the objective of the work reported here, and in the companion paper 1 . A broader examination of wind turbine dynamic response to turbulence, and attempts to ascertain the features of turbulence that wind turbines are most sensitive to were made. A statistical description of the wind input including all three wind components and allowing linear wind gradients across the rotor disk, was used together with quasi-static aerodynamic theory and an elementary structural model involving only a few degrees of freedom. The idea was to keep the turbine model simple and show the benefits of this type of statistical wind representation before attempting to use a more complex turbine model. As far as possible, the analysis was kept in the simplest form, while still preserving key physical responses.

Thresher, R. W.; Holley, W. E.; Jafarey, N.

1981-01-01

214

Review of bubble detector response characteristics and results from space.  

PubMed

A passive neutron-bubble dosemeter (BD), developed by Bubble Technology Industries, has been used for space applications. Both the bubble detector-personal neutron dosemeter and bubble detector spectrometer have been studied at ground-based facilities in order to characterise their response due to neutrons, heavy ion particles and protons. This technology was first used during the Canadian-Russian collaboration aboard the Russian satellite BION-9, and subsequently on other space missions, including later BION satellites, the space transportation system, Russian MIR space station and International Space Station. This paper provides an overview of the experiments that have been performed for both ground-based and space studies in an effort to characterise the response of these detectors to various particle types in low earth orbit and presents results from the various space investigations. PMID:21890528

Lewis, B J; Smith, M B; Ing, H; Andrews, H R; Machrafi, R; Tomi, L; Matthews, T J; Veloce, L; Shurshakov, V; Tchernykh, I; Khoshooniy, N

2012-06-01

215

Responses to Mild Cold Stress Are Predicted by Different Individual Characteristics in Young and Older Subjects  

NSDL National Science Digital Library

Journal article "Responses to Mild Cold Stress Are Predicted by Different Individual Characteristics in Young and Older Subjects", from the Journal of Applied Physiology, by David W. Degroot, W. Larry Kenny, and George Havenith.

David W DeGroot (Pennsylvania State University Kinesiology); Larry W. Kenny (Pennsylvania State University Kinesiology); George Havenith (Loughborough University Human Sciences)

2006-12-01

216

Research on relation between bending stress and characteristic frequency of H-shaped beam by free vibration deflection  

NASA Astrophysics Data System (ADS)

In order to investigate a relation between a bending stress and a characteristic frequency of a beam, 4-point loading which had constant moment region was conducted to a beam with H shape configuration experimentally and numerically. H-shaped beam has many characteristic deformation modes. Axial tensile stress in the beam made its characteristic frequency higher, and compressive stress lower. In the experiment, some characteristic frequencies got higher by a bending stress, and the others stayed in a small frequency fluctuation. The distinction is anticipated as a capability to measure a bending stress of a beam by its characteristic frequencies.

Yoshida, Tsutomu; Watanabe, Takeshi

2014-05-01

217

NIST torsion oscillator viscometer response: Performance on the LeRC active vibration isolation platform  

NASA Technical Reports Server (NTRS)

Critical point viscosity measurements are limited to their reduced temperature approach to T(sub c) in an Earth bound system, because of density gradients imposed by gravity. Therefore, these classes of experiments have been proposed as good candidates for 'microgravity' science experiments where this limitation is not present. The nature of these viscosity measurements dictate hardware that is sensitive to low frequency excitations. Because of the vibratory acceleration sensitivity of a torsion oscillator viscometer, used to acquire such measurements, a vibration isolation sensitivity test was performed on candidate 'microgravity' hardware to study the possibility of meeting the stringent oscillatory sensitivity requirements of a National Institute of Standards and Technology (NIST) torsion oscillator viscometer. A prototype six degree of freedom active magnetic isolation system, developed at NASA Lewis Research Center, was used as the isolation system. The ambient acceleration levels of the platform were reduced to the noise floor levels of its control sensors, about one microgravity in the 0.1 to 10 Hz bandwidth.

Berg, Robert F.; Grodsinsky, Carlos M.

1992-01-01

218

Vibration of Shells  

NASA Technical Reports Server (NTRS)

The vibrational characteristics and mechanical properties of shell structures are discussed. The subjects presented are: (1) fundamental equations of thin shell theory, (2) characteristics of thin circular cylindrical shells, (3) complicating effects in circular cylindrical shells, (4) noncircular cylindrical shell properties, (5) characteristics of spherical shells, and (6) solution of three-dimensional equations of motion for cylinders.

Leissa, A. W.

1973-01-01

219

Characteristic neurobiological patterns differentiate paternal responsiveness in two Peromyscus species.  

PubMed

Rodent paternal models provide unique opportunities to investigate the emergence of affiliative social behavior in mammals. Using biparental and uniparental Peromyscus species (californicus and maniculatus, respectively) we assessed paternal responsiveness by exposing males to biological offspring, unrelated conspecific pups, or familiar brothers following a 24-hour separation. The putative paternal circuit we investigated included brain areas involved in fear/anxiety [cingulate cortex (Cg), medial amygdala (MeA), paraventricular nucleus of the hypothalamus (PVN), and lateral septum (LS)], parental motivation [medial preoptic area (MPOA)], learning/behavioral plasticity (hippocampus), olfaction [pyriform cortex (PC)], and social rewards (nucleus accumbens). Paternal experience in californicus males reduced fos immunoreactivity (ir) in several fear/anxiety areas; additionally, all californicus groups exhibited decreased fos-ir in the PC. Enhanced arginine vasopressin (AVP) and oxytocin (OT)-ir cell bodies and fibers, as well as increased neuronal restructuring in the hippocampus, were also observed in californicus mice. Multidimensional scaling analyses revealed distinct brain activation profiles differentiating californicus biological fathers, pup-exposed virgins, and pup-naïve virgins. Specifically, associations among MPOA fos, CA1 fos, dentate gyrus GFAP, CA2 nestin-, and PVN OT-ir characterized biological fathers; LS fos-, Cg fos-, and AVP-ir characterized pup-exposed virgins, and PC-, PVN-, and MeA fos-ir characterized pup-naïve virgins. Thus, whereas fear/anxiety areas characterized pup-naïve males, neurobiological factors involved in more diverse functions such as learning, motivation, and nurturing responses characterized fatherhood in biparental californicus mice. Less distinct paternal-dependent activation patterns were observed in uniparental maniculatus mice. These data suggest that dual neurobiological circuits, leading to the inhibition of social-dependent anxiety as well as the activation of affiliative responses, characterize the transition from nonpaternal to paternal status in californicus mice. PMID:21546770

Lambert, Kelly G; Franssen, Catherine L; Bardi, Massimo; Hampton, Joseph E; Hainley, Leslie; Karsner, Stephanie; Tu, Eddie B; Hyer, Molly M; Crockett, Ashly; Baranova, Anya; Ferguson, Tajh; Ferguson, Tenaj; Kinsley, Craig H

2011-01-01

220

Inelastic Response of Reinforced Concrete Frames to Seismic Ground Motions Having Different Characteristics  

Microsoft Academic Search

Observations of structural damage following recent major earthquakes have indicated that ground motion characteristics have a significant effect on the damage of building structures. An analytical study is undertaken to investigate the effect of ground motion characteristics on the inelastic response of multistorey reinforced concrete frame structures and to evaluate the seismic performance of reinforced concrete frame structures designed in

Tian-Jian Zhu

1989-01-01

221

VIBRA: An interactive computer program for steady-state vibration response analysis of linear damped structures  

NASA Technical Reports Server (NTRS)

An interactive steady state frequency response computer program with graphics is documented. Single or multiple forces may be applied to the structure using a modal superposition approach to calculate response. The method can be reapplied to linear, proportionally damped structures in which the damping may be viscous or structural. The theoretical approach and program organization are described. Example problems, user instructions, and a sample interactive session are given to demonstate the program's capability in solving a variety of problems.

Bowman, L. M.

1984-01-01

222

Characteristics of wind forces and responses of rectangular tall buildings  

NASA Astrophysics Data System (ADS)

This paper presents the results of wind tunnel tests on rectangular building models having the same plan area and height but different side ratios of 1, 1.56, 2.25, 3.06 and 4. The models were made from perspex sheet at a geometrical scale of 1:300. The wind pressure coefficients on all the models were evaluated from pressure records measured in a closed circuit wind tunnel under boundary layer flow for wind directions of 0° to 90° at an interval of 15°. The mean responses of rectangular tall buildings having different side ratios were also evaluated from the experimentally obtained wind loads. Effectiveness of side ratio of buildings in changing the surface pressure distribution and mean responses of prototype buildings is assessed for wind directions of 0° to 90° at an interval of 15°. It is observed that the side ratio of buildings significantly affects the wind pressures on leeward and sidewalls, whereas wind pressure on windward wall is almost independent of side ratio. Further, the wind incidence angles and side ratio of the buildings significantly affect its mean displacements as well as torque.

Amin, J. A.; Ahuja, A. K.

2014-09-01

223

Characteristics of antibody responses in Pigeon Fanciers' Lung.  

PubMed

The aetiology of Pigeon Fanciers' Lung (PFL) is believed to include immune complex formation between inhaled pigeon antigens and antibodies generated against them. However it is unclear why some fanciers are asymptomatic despite the presence of high levels of anti-avian antigen antibodies in their serum. In this study we investigated whether qualitative differences in specific antibodies might contribute to disease. IgG responses among pigeon fanciers were determined by ELISA and the functional affinity of IgG1 and IgG2 against a range of pigeon antigens was determined by inhibition ELISA and Isothermal Titration Calorimetry (ITC). The median titres of IgG1 and IgG2 against all the pigeon antigens tested was higher in asymptomatic than symptomatic fanciers and these differences were significant for anti-pigeon serum IgG1 (P=0.04), anti-fresh pigeon droppings (PDF) IgG2 (P=0.028), anti-old pigeon droppings (PDO) IgG2 (P=0.04) and anti-pigeon intestinal scrapings IgG2 (P=0.03). The functional affinity of IgG1 and IgG2 against PDO was higher in symptomatic individuals (P=0.006 and P=0.002, respectively) whilst the functional affinity of anti-PDF IgG2 was also significantly higher in these patients (P?0.001). Symptomatic fanciers were also significantly more likely to have a high reaction enthalphy (?H) as measured by ITC and thus had higher affinity antibodies against PDO (P=0.044). This data confirms previous studies showing that the magnitude alone of the antibody response to pigeon antigens cannot determine the presence of PFL, but that antibody affinity may be important. ITC is a rapid method of measuring antibody affinity and has diagnostic potential in PFL, and may be of use in other situations where antibody affinity is important. PMID:23291145

Nademi, Zohreh; Todryk, Stephen; Baldwin, Christopher

2013-06-01

224

Output frequency response function based design of additional nonlinear viscous dampers for vibration control of multi-degree-of-freedom systems  

NASA Astrophysics Data System (ADS)

This paper is concerned with the development of a new technique for the optimal placement and design of additional nonlinear viscous dampers for vibration control of Multi-Degree-Of-Freedom (MDOF) systems. The MDOF systems described by a multi-storey shear building model and subjected to harmonic loadings are first considered in the present study; then, the basic ideas of the design are extended to the cases of earthquake loadings. The studies are based on the concept of Output Frequency Response Function (OFRF) and associated methods proposed recently by the authors in control engineering and extend, for the first time, the well-established linear viscous damper optimal placement and design techniques for MDOF system vibration control to the nonlinear case. The design examples verify the effectiveness of the new technique, and demonstrate the beneficial effects of the designed additional nonlinear dampers on the MDOF system vibration control and the advantages of nonlinear viscous dampers over linear dampers in such applications.

Lang, Z. Q.; Guo, P. F.; Takewaki, I.

2013-09-01

225

Social responsibility disclosure and corporate characteristics: the case of Jordanian industrial companies  

Microsoft Academic Search

The main objectives of this paper are to evaluate social responsibility disclosure practices in the annual reports of Jordanian industrial companies and to determine the effect of certain company characteristics in explaining variation in social responsibility information found in companies' annual reports. To accomplish these objectives, a disclosure index including 37 items was applied to the annual reports of 65

Mishiel Said Suwaidan; Ahmad Moh'd Al-omari; Ruwaidah Hanna Haddad

2004-01-01

226

Operating Characteristics of Six Response Distortion Indicators for the Personality Assessment Inventory.  

ERIC Educational Resources Information Center

Characteristics of six different indicators of response distortion on the Personality Assessment Inventory (PAI) (L. Morey, 1991) were evaluated by having 134 college students complete the PAI under positive impression management, malingering, and honest responding conditions. All six indicators could distinguish actual and feigned responses. (SLD)

Morey, Leslie C.; Lanier, V. Whitson

1998-01-01

227

Stress response effects on growth, carcass characteristics, and tenderness in Bonsmara-influenced steers  

E-print Network

behavioral stress responses at different stages in the U.S. beef production system with growth, carcass characteristics and tenderness. The first experiment evaluated stress responses at both time of weaning and at the beginning of the feedlot period on half...

Falkenberg, Shollie Marie

2006-08-16

228

Effects of heterospecific and conspecific vibrational signal overlap and signal-to-noise ratio on male responsiveness in Nezara viridula (L.).  

PubMed

Animals often communicate in environments with high levels of biotic noise that arises from the signals of other individuals. Although effects of background biotic noise on mate recognition and discrimination have been widely studied in air-born sound communication, little is known about incidental interference between signallers that use substrate-borne vibrational signals. In this study we investigated the ability of males of the southern green stink bug Nezara viridula (L.) (Heteroptera: Pentatomidae) to recognize conspecific female song in the presence of biotic noise originating from conspecific and heterospecific vibrational signals. We tested male responsiveness on a bean plant in playback experiments. One leaf was vibrated with conspecific female song, while to the other one we simultaneously applied either heterospecific female signal or various altered conspecific signals with different temporal parameters. We tested males in three levels of biotic noise, ranging from +6 dB to -6 dB and we compared male responsiveness in each treatment with response obtained in unilateral treatment with unaltered conspecific female calling song. Male responsiveness was reduced in the presence of heterospecific signals or when background noise from conspecific signals obscured the species-specific temporal pattern of conspecific female song. By contrast, the presence of two sources of conspecific female songs had a positive effect on male responsiveness, for as long as the signal repetition rate of perceived song did not differ from the species-specific value. In the presence of interfering background signals, searching activity was less affected than male signalling. Increased signal-to-noise ratio restored male responsiveness to the level expressed in unilateral stimulation with conspecific female song. The results are discussed with regard to male behavioural strategies for vibrational communication in a noisy environment. PMID:20802124

de Groot, Maarten; Cokl, Andrej; Virant-Doberlet, Meta

2010-09-15

229

Impulse technique for structural frequency response testing  

Microsoft Academic Search

Knowledge of the dynamic characteristics of structural elements often means the difference between success and failure in the solution of complex noise and vibration problems. The effects of structural resonances-conditions of relatively low dynamic stiffness-can lead to seriously reduced effectiveness of isolation elements and result in significantly increased dynamic response of sound radiating or vibration exposure elements. Quantitative knowledge of

William G. Halvorsen; David L. Brown

1978-01-01

230

Experimental Analysis of a Piezoelectric Energy Harvesting System for Harmonic, Random, and Sine on Random Vibration  

SciTech Connect

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 requirements by increasing harvested power, shifting optimal conditioning impedance, inducing significant voltage supply fluctuations and ultimately rendering idealized sinusoidal and random analyses insufficient.

Cryns, Jackson W.; Hatchell, Brian K.; Santiago-Rojas, Emiliano; Silvers, Kurt L.

2013-07-01

231

Vibration analysis methods for piping  

NASA Astrophysics Data System (ADS)

Attention is given to flow vibrations in pipe flow induced by singularity points in the piping system. The types of pressure fluctuations induced by flow singularities are examined, including the intense wideband fluctuations immediately downstream of the singularity and the acoustic fluctuations encountered in the remainder of the circuit, and a theory of noise generation by unsteady flow in internal acoustics is developed. The response of the piping systems to the pressure fluctuations thus generated is considered, and the calculation of the modal characteristics of piping containing a dense fluid in order to obtain the system transfer function is discussed. The TEDEL program, which calculates the vibratory response of a structure composed of straight and curved pipes with variable mechanical characteristics forming a three-dimensional network by a finite element method, is then presented, and calculations of fluid-structural coupling in tubular networks are illustrated.

Gibert, R. J.

1981-09-01

232

Vibration isolation of automotive vehicle engine using periodic mounting systems  

NASA Astrophysics Data System (ADS)

Customer awareness and sensitivity to noise and vibration levels have been raised through increasing television advertisement, in which the vehicle noise and vibration performance is used as the main market differentiation. This awareness has caused the transportation industry to regard noise and vibration as important criteria for improving market shares. One industry that tends to be in the forefront of the technology to reduce the levels of noise and vibration is the automobile industry. Hence, it is of practical interest to reduce the vibrations induced structural responses. The automotive vehicle engine is the main source of mechanical vibrations of automobiles. The engine is vulnerable to the dynamic action caused by engine disturbance force in various speed ranges. The vibrations of the automotive vehicle engines may cause structural failure, malfunction of other parts, or discomfort to passengers because of high level noise and vibrations. The mounts of the engines act as the transmission paths of the vibrations transmitted from the excitation sources to the body of the vehicle and passengers. Therefore, proper design and control of these mounts are essential to the attenuation of the vibration of platform structures. To improve vibration resistant capacities of engine mounting systems, vibration control techniques may be used. For instance, some passive and semi-active dissipation devices may be installed at mounts to enhance vibration energy absorbing capacity. In the proposed study, a radically different concept is presented whereby periodic mounts are considered because these mounts exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic mounts only within specific frequency bands called the "Pass Bands" and wave propagation is completely blocked within other frequency bands called the "Stop Bands". The experimental arrangements, including the design of mounting systems with plain and periodic mounts will be studied first. The dynamic characteristics of such systems will be obtained experimentally in both cases. The tests will be then carried out to study the performance characteristics of periodic mounts with geometrical and/or material periodicity. The effectiveness of the periodicity on the vibration levels of mounting systems will be demonstrated theoretically and experimentally. Finally, the experimental results will be compared with the theoretical predictions.

Asiri, S.

2005-05-01

233

Vibrational signaling in the agonistic interactions of red-eyed treefrogs.  

PubMed

Sensitivity to substrate-borne vibrations is widespread in animals and evolutionarily precedes hearing but, compared with other sensory modalities, we know little about vibrational communication, particularly in vertebrates. For plant-dwelling arthropods, vibrations are likely as important as sound. Arboreal vertebrates excite plant vibrations with most movements, but the behavioral relevance of these vibrations has not been tested experimentally. In playback experiments using a robotic model frog and an electrodynamic shaker, we demonstrate that plant-borne vibrations generated by the shaking (tremulation) display of male red-eyed treefrogs (Agalychnis callidryas) are a vibrational signal, necessary and sufficient to elicit tremulations in response. A trend toward increased aggression during visual playbacks suggests that the visual component of tremulations may also convey information. In male-male contests, tremulations were the most frequent aggressive display, and their use and vibrational characteristics varied with male size and conflict context. Nearly all of A. callidryas' signaling behaviors, including tremulations and acoustic calls, excite strong, stereotyped vibrations that travel through plants and could be informative to receivers. Our results demonstrate that vibrational signals serve a key role in the biology of one well-known arboreal frog and suggest that consideration of the vibrational modality may significantly broaden our appreciation of the behavior and evolution of arboreal vertebrates. PMID:20493702

Caldwell, Michael S; Johnston, Gregory R; McDaniel, J Gregory; Warkentin, Karen M

2010-06-01

234

Vibration Response Models of a Stiffened Aluminum Plate Excited by a Shaker  

NASA Technical Reports Server (NTRS)

Numerical models of structural-acoustic interactions are of interest to aircraft designers and the space program. This paper describes a comparison between two energy finite element codes, a statistical energy analysis code, a structural finite element code, and the experimentally measured response of a stiffened aluminum plate excited by a shaker. Different methods for modeling the stiffeners and the power input from the shaker are discussed. The results show that the energy codes (energy finite element and statistical energy analysis) accurately predicted the measured mean square velocity of the plate. In addition, predictions from an energy finite element code had the best spatial correlation with measured velocities. However, predictions from a considerably simpler, single subsystem, statistical energy analysis model also correlated well with the spatial velocity distribution. The results highlight a need for further work to understand the relationship between modeling assumptions and the prediction results.

Cabell, Randolph H.

2008-01-01

235

Demonstrating the Effect of Particle Impact Dampers on the Random Vibration Response and Fatigue Life of Printed Wiring Assemblies  

NASA Technical Reports Server (NTRS)

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.

Knight, Brent; Montgomery, Randall; Geist, David; Hunt, Ron; LaVerde, Bruce; Towner, Robert

2013-01-01

236

Flapping response characteristics of hingeless rotor blades by a gereralized harmonic balance method  

NASA Technical Reports Server (NTRS)

Linearized equations of motion for the flapping response of flexible rotor blades in forward flight are derived in terms of generalized coordinates. The equations are solved using a matrix form of the method of linear harmonic balance, yielding response derivatives for each harmonic of the blade deformations and of the hub forces and moments. Numerical results and approximate closed-form expressions for rotor derivatives are used to illustrate the relationships between rotor parameters, modeling assumptions, and rotor response characteristics. Finally, basic hingeless rotor response derivatives are presented in tabular and graphical form for a wide range of configuration parameters and operating conditions.

Peters, D. A.; Ormiston, R. A.

1975-01-01

237

[Defining characteristics of the Dysfunctional Ventilatory Weaning Response as indicators of accuracy of ventilatory weaning].  

PubMed

The study aimed to analyze the defining characteristics of the Dysfunctional Ventilatory Weaning Response as an indicator of the accuracy of ventilatory weaning. Observational study of 38 events of ventilatory weaning in adult patients admitted to intensive care. For the defining characteristics, it was calculated: sensitivity, specificity, positive and negative predictive values, accuracy or efficiency, likelihood ratio positive and negative, and diagnostic odds ratio. It was also considered the median number of defining characteristics in the event of success and failure. It was considered accurate: agitation, deterioration in arterial blood gases from baseline parameters, moderate use of accessory muscles of respiration, increased respiratory rate from baseline parameters and respiratory rate increases significantly with respect to baseline parameters. There was statistical difference in the median number of defining characteristics observed. It was concluded that the defining characteristic and the number of them would influence the success of the weaning decision. PMID:25517667

Brandão, Marcos Antônio Gomes; Cerqueira, Fernanda Avellar; Matos, Ligia Neres; Campos, Juliana Faria; Peixoto, Mauricio Abreu Pinto; Primo, Cândida Caniçali

2014-10-01

238

Noninvasive Determination of Bone Mechanical Properties using Vibration Response: A Refined Model and Validation in vivo  

NASA Technical Reports Server (NTRS)

Accurate non-invasive mechanical measurement of long bones is made difficult by the masking effect of surrounding soft tissues. Mechanical Response Tissue Analysis (MRTA) offers a method for separating the effects of the soft tissue and bone; however, a direct validation has been lacking. A theoretical analysis of wave propagation through the compressed tissue revealed a strong mass effect dependent on the relative accelerations of the probe and bone. The previous mathematical model of the bone and overlying tissue system was reconfigured to incorporate the theoretical finding. This newer model (six-parameter) was used to interpret results using MRTA to determine bone cross-sectional bending stiffness, EI(sub MRTA). The relationship between EI(MRTA) and theoretical EI values for padded aluminum rods was R(exp 2) = 0.999. A biological validation followed using monkey tibias. Each bone was tested in vivo with the MRTA instrument. Postmortem, the same tibias were excised and tested to failure in three-point bending to determine EI(sub 3-PT) and maximum load. Diaphyseal Bone Mineral Density (BMD) measurements were also made. The relationship between E(sub 3-PT) and in vivo EI(sub MRTA) using the six-parameter model is strong (R(exp 2) = 0.947) and better than that using the older model (R(exp 2) = 0.645). EI(MRTA) and BMD are also highly correlated (R(exp 2) = 0.853). MRTA measurements in vivo and BMD ex vivo are both good predictors of scaled maximum strength (R(exp 2) = 0.915 and R(exp 2) = 0.894, respectively). This is the first biological validation of a non-invasive mechanical measurement of bone by comparison to actual values. The MRTA technique has potential clinical value for assessing long-bone mechanical properties.

Roberts, S. G.; Hutchinson, T. M.; Arnaud, S. B.; Steele, C. R.; Kiratli, B. J.; Martin, R. B.

1996-01-01

239

Noninvasive Determination of Bone Mechanical Properties Using Vibration Response: A Refined Model and Validation in vivo  

NASA Technical Reports Server (NTRS)

Accurate non-invasive mechanical measurement of long bones is made difficult by the masking effect of surrounding soft tissues. Mechanical response tissue analysis (MRTA) offers a method for separating the effects of the soft tissue and bone; however, a direct validation has been lacking. A theoretical analysis of wave propagation through the compressed tissue revealed a strong mass effect dependent on the relative accelerations of the probe and bone. The previous mathematical model of the bone and overlying tissue system was reconfigured to incorporate the theoretical finding. This newer model (six-parameter) was used to interpret results using MRTA to determine bone cross-sectional bending stiffness, EI(sub MRTA). The relationship between EI(sub MRTA) and theoretical EI values for padded aluminum rods was R(sup 2) = 0.999. A biological validation followed using monkey tibias. Each bone was tested in vivo with the MRTA instrument. Postmortem, the same tibias were excised and tested to failure in three-point bending to determine EI(sub 3-PT) and maximum load. Diaphyseal bone mineral density (BMD) measurements were also made. The relationship between EI(sub 3-PT) and in vivo EI(sub MRTA) using the six-parameter model is strong (R(sup 2) = 0.947) and better than that using the older model (R(sup 2) = 0.645). EI(sub MRTA) and BMD are also highly correlated (R(sup 2) = 0.853). MRTA measurements in vivo and BMD ex vivo are both good predictors of scaled maximum strength (R(sup 2) = 0.915 and R(sup 2) = 0.894, respectively). This is the first biological validation of a non- invasive mechanical measurement of bone by comparison to actual values. The MRTA technique has potential clinical value for assessing long-bone mechanical properties.

Roberts, S. G.; Hutchinson, T. M.; Arnaud, S. B.; Kiratli, B. J; Steele, C. R.

1996-01-01

240

A Study of the Characteristics of Human-Pilot Control Response to Simulated Aircraft Lateral Motions  

NASA Technical Reports Server (NTRS)

Report presents the results of studies made in an attempt to provide information on the control operations of the human pilot. These studies included an investigation of the ability of pilots to control simulated unstable yawing oscillations, a study of the basic characteristics of human-pilot control response, and a study to determine whether and to what extent pilot control response can be represented in an analytical form.

Cheatham, Donald C

1954-01-01

241

14 CFR 33.83 - Vibration test.  

Code of Federal Regulations, 2010 CFR

... (e) The effects on vibration...each specific installation configuration...characteristics of the engine. If these vibration effects cannot be fully...investigated during engine certification...defined in the installation instructions...

2010-01-01

242

Female gray treefrogs, Hyla versicolor, are responsive to visual stimuli but unselective of stimulus characteristics.  

PubMed

The visual ecology of nocturnal anurans is poorly understood, but there is growing evidence that vision plays a role in important behaviors such as mate choice. While several recent studies have demonstrated that females are responsive to visual cues when selecting mates, the forces responsible for these preferences are unknown. We investigated the responsiveness of female gray treefrogs, Hyla versicolor, to video playbacks of calling conspecific males in which we varied attributes of the vocal sac, a conspicuous visual characteristic of calling males and a target of female choice in other species. Females responded surprisingly strongly to the video playbacks, but did so indiscriminately with respect to variation in vocal sac characteristics. We followed up on these results with a series of additional tests that examined female responses to abstract stimuli. Females continued to respond to such stimuli, leading us to conclude that their behavior was related to a generalized phototactic response. Because of this, we were unable to make conclusions regarding female preferences for vocal sac characteristics. Nonetheless, our results are significant in two respects. First, we illustrate that despite much effort into improving video playback methodologies, challenges remain, and we offer our experimental design as a method to ensure that appropriate conclusions can be drawn from such studies. Second, we argue that the female phototactic response has potentially significant behavioral implications and in general the consequences of anuran visual preferences deserve further investigation. PMID:25013111

Reichert, Michael S; Galante, Holland; Höbel, Gerlinde

2014-09-15

243

The effects of acceleration on the mechanical impedance response of a primate model exposed to sinusoidal vibration  

Microsoft Academic Search

Criteria for developing active and passive isolation mechanisms for reducing the effects of whole-body vibration exposure\\u000a rely on a thorough understanding of the stiffness, damping, and resonance behaviors of the human or human surrogate body.\\u000a Three Rhesus monkeys were exposed to seated whole-body sinusoidal vibration between 3 and 20 Hz at 0.69 and 3.47 msec?2 rms (0.1 and 0.5 g

Suzanne D. Smith; Leon E. Kazarian

1994-01-01

244

A Branched Beam-Based Vibration Energy Harvester  

NASA Astrophysics Data System (ADS)

In this paper, a strategy to utilize a branched beam system to improve the frequency response characteristic of vibration energy harvesting is demonstrated. A basic unit of the device consists of several branch beams with proof mass at their ends and one main cantilever beam with a piezoelectric component at its root and proof mass at its end. The device can utilize the resonance of the branch beams and main beam to generate multiple output voltage peaks, providing a better frequency response characteristic than that of the conventional piezoelectric vibration energy harvester. Multiple branch structure and multiple basic units with similar structures can be connected to generate more output voltage peaks in the frequency response characteristic. Only one piezoelectric component is needed in the device, which makes it competitive in the management of harvested electric energy.

Zhang, Guangcheng; Hu, Junhui

2014-09-01

245

A Branched Beam-Based Vibration Energy Harvester  

NASA Astrophysics Data System (ADS)

In this paper, a strategy to utilize a branched beam system to improve the frequency response characteristic of vibration energy harvesting is demonstrated. A basic unit of the device consists of several branch beams with proof mass at their ends and one main cantilever beam with a piezoelectric component at its root and proof mass at its end. The device can utilize the resonance of the branch beams and main beam to generate multiple output voltage peaks, providing a better frequency response characteristic than that of the conventional piezoelectric vibration energy harvester. Multiple branch structure and multiple basic units with similar structures can be connected to generate more output voltage peaks in the frequency response characteristic. Only one piezoelectric component is needed in the device, which makes it competitive in the management of harvested electric energy.

Zhang, Guangcheng; Hu, Junhui

2014-11-01

246

Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design  

NASA Technical Reports Server (NTRS)

The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful operating range. Operating a blade at or near the resonance frequencies leads to high-cycle fatigue, which ultimately limits the blade's durability and life. So the aim of this study is to determine the variation of the resonance frequencies for an idealized sandwich blade as a function of its face-sheet thickness, core thickness, and foam density. The finite element method is used to determine the natural frequencies for an idealized rectangular sandwich blade. The proven Lanczos method (ref. 7) is used in the study to extract the natural frequency.

Ghosn, Louis J.; Min, James B.; Raj, Sai V.; Lerch, Bradley A.; Holland, Frederic A., Jr.

2004-01-01

247

Relationships of Examinee Pair Characteristics and Item Response Similarity. ACT Research Report Series, 2012 (8)  

ERIC Educational Resources Information Center

Detecting unusual similarity in the item responses of a pair of examinees usually conditions on the pair's overall test performance (e.g., raw scores). Doing this, however, often requires assumptions about the invariance of other examinee pair characteristics. In this study, we examined the appropriateness of such assumptions about selected…

Allen, Jeff

2012-01-01

248

Preference for Anonymous Classroom Participation: Linking Student Characteristics and Reactions to Electronic Response Systems  

ERIC Educational Resources Information Center

Electronic response systems (ERS) are a means to foster class participation by students who are reluctant to participate in class. In this study, we identify individual characteristics that relate to students' preference for anonymous classroom participation, and we also examine the extent to which preference for anonymity is related to their…

Latham, Alyson; Hill, N. Sharon

2014-01-01

249

Utility of MMPI-2 Indicators of Response Distortion: Receiver Operating Characteristic Analysis.  

ERIC Educational Resources Information Center

Receiver operating characteristic (ROC) analysis was used to evaluate 11 Minnesota Multiphasic Personality Inventory-2 (MMPI-2) indicators of response distortion using 343 college students, some of whom simulated malingering or defensive responding, 181 forensic psychiatric patients, and 95 other psychiatric patients. Results show the usefulness…

Nicholson, Robert A.; Mouton, Glenn J.; Bagby, R. Michael; Buis, Tom; Peterson, Stephanie A.; Buigas, Rudy A.

1997-01-01

250

Response Time of Broiler Chickens to Cimaterol: Meat Tenderness, Muscle Composition, Fiber Size, and Carcass Characteristics  

Microsoft Academic Search

The response time to cimaterol (CIM), a P-adrenergic agonist, by broiler chickens for carcass characteristics, muscle composition, muscle fiber size, catheptic enzyme activity, and tenderness was determined. Two trials were con- ducted in which chickens were fed a control diet (CON) containing 0 ppm of CIM or a diet contain- ing 1 ppm of CIM. Trial 1 consisted of 55,

B. L. Gwartney; S. J. Jones; C. R. Calkins

2010-01-01

251

The Association between SAT Prompt Characteristics, Response Features, and Essay Scores  

ERIC Educational Resources Information Center

This study investigated the relationship of prompt characteristics and response features with essay scores on the SAT Reasoning Test. A sample of essays was coded on a variety of features regarding their length and content. Analyses included descriptive statistics and computation of effect sizes, correlations between essay features and scores, and…

Kobrin, Jennifer L.; Deng, Hui; Shaw, Emily J.

2011-01-01

252

Numerical electromagnetic field analysis of unit step response characteristics of impulse voltage measuring systems  

Microsoft Academic Search

Unit step response characteristics of impulse voltage measuring systems are studied with the help of numerical electromagnetics code (NEC-2). Prior to this analysis, the accuracy of a transient analysis by this method is investigated for a simple structure. An impulse voltage measuring system, under application of step voltage, behaves like an antenna until a traveling wave makes several roundtrips in

Yoshihiro Baba; Masaru Ishii

2004-01-01

253

Response Characteristics of Single Cells in the Monkey Superior Colliculus Following Ablation or  

E-print Network

Response Characteristics of Single Cells in the Monkey Superior Colliculus Following Ablation the contribution of visual cortex to collicular function in the rhesus monkey (Macaca mulatta), a species whose that in the monkey, as in the cat, retina and visual cortex project densely on the superior colliculus (8

Stryker, Michael

254

Surface characteristics and osteoblastic cell response to titanium-8tantalum-3neobium alloy  

NASA Astrophysics Data System (ADS)

In the present study, the surface properties and osteblastic responses to a titanium-8%tantalum-3%niobium (Ti-8Ta-3Nb) alloy were investigated in vitro. The surface roughness and morphology of all samples appeared similar. The surface of the Ti-8Ta-3Nb alloy was more hydrophilic than those of commercially pure titanium (Tisbnd S) and Ti-6Al-4V alloy. The Ti-8Ta-3Nb alloy had a better cellular response with regard to proliferation and ALP activity. The present study showed improved surface characteristics and osteoblastic response to the Ti-8Ta-3Nb alloy compared to Tisbnd S and Ti-6Al-4V alloy.

Cui, De-zhe; Park, Ki-Deog; Lee, Kyung-Ku; Jung, Young-Suk; Lee, Bo-Ah; Lee, Yang-Jin; Kim, Ok-Su; Chung, Hyun-Ju; Kim, Young-Joon

2012-12-01

255

Effects of a Dynamic Warm-Up, Static Stretching or Static Stretching with Tendon Vibration on Vertical Jump Performance and EMG Responses.  

PubMed

The purpose of this study was to investigate the short-term effects of static stretching, with vibration given directly over Achilles tendon, on electro-myographic (EMG) responses and vertical jump (VJ) performances. Fifteen male, college athletes voluntarily participated in this study (n=15; age: 22±4 years old; body height: 181±10 cm; body mass: 74±11 kg). All stages were completed within 90 minutes for each participant. Tendon vibration bouts lasted 30 seconds at 50 Hz for each volunteer. EMG analysis for peripheral silent period, H-reflex, H-reflex threshold, T-reflex and H/M ratio were completed for each experimental phases. EMG data were obtained from the soleus muscle in response to electro stimulation on the popliteal post tibial nerve. As expected, the dynamic warm-up (DW) increased VJ performances (p=0.004). Increased VJ performances after the DW were not statistically substantiated by the EMG findings. In addition, EMG results did not indicate that either static stretching (SS) or tendon vibration combined with static stretching (TVSS) had any detrimental or facilitation effect on vertical jump performances. In conclusion, using TVSS does not seem to facilitate warm-up effects before explosive performance. PMID:24511340

Yapicioglu, Bulent; Colakoglu, Muzaffer; Colakoglu, Zafer; Gulluoglu, Halil; Bademkiran, Fikret; Ozkaya, Ozgur

2013-12-18

256

Response surface methodology for predicting quality characteristics of beef patties added with flaxseed and tomato paste.  

PubMed

Response surface methodology was used to study the effect of flaxseed flour (FS) and tomato paste (TP) addition, from 0 to 10% and 0 to 20% respectively, on beef patty quality characteristics. The assessed quality characteristics were color (L, a, and b), pH and texture profile analysis (TPA). Also, sensory analysis was performed for the assessment of color, juiciness, firmness, and general acceptance. FS addition reduced L and a values and decreased weight loss of cooked products (P<0.05). An opposite effect was observed when TP was added (P<0.05). All TPA parameters decreased when percentages of FS and TP were increased in the formulation of beef patties. Furthermore, FS and TP addition adversely affected the sensory characteristics of the cooked product (P<0.05); nevertheless, all sensory characteristics evaluated had an acceptable score (>5.6). Thus FS and TP are ingredients that can be used in beef patty preparation. PMID:24509360

Valenzuela Melendres, M; Camou, J P; Torrentera Olivera, N G; Alvarez Almora, E; González Mendoza, D; Avendaño Reyes, L; González Ríos, H

2014-05-01

257

Using Surface Electromyography To Assess Sex Differences in Neuromuscular Response Characteristics  

PubMed Central

Objective: To provide an overview of the continuum of muscular responses that typically occur with joint perturbation. The applications and limitations of surface electromyography (sEMG) in evaluating these responses are also addressed. Research applications assessing sex differences in these neuromuscular response characteristics are discussed along with suggestions for future research. Data Sources: MEDLINE was searched from 1969 through 1998. Sport DISCUS was searched from 1975 through 1998. Terms searched included “anterior cruciate ligament,” “epidemiology,” “neuromuscular control,” “neuromuscular performance,” “electromyography,” “latency,” “reflex,” “electromechanical delay,” “dynamic stability,” “intrinsic stiffness,” “short-range stiffness,” “muscle,” “mechanoreceptors,” and “reaction time.” Data Synthesis: It is widely accepted that efficient neuromuscular control is essential to dynamic joint stability and protection. Many studies have established the significant role of the muscles, and particularly the hamstrings, in providing knee stability. By observing the timing, phasing, and recruitment of reflexive muscular activation after a loading stress to the knee, we can better understand the coordinative mechanisms necessary to protect the joint and prevent ligament injury. A number of research models have employed the use of sEMG to evaluate neuromuscular responses at the knee after joint loading or perturbation. However, very few studies have specifically addressed potential sex differences in these response characteristics. Conclusions/Recommendations: From the limited research available, it appears that a sex difference may exist in some aspects of neuromuscular responses. However, further research is needed to explore these differences at the knee and their potential role as predisposing factors to the higher incidence of anterior cruciate ligament injuries in females. Future studies should examine sex differences in neuromuscular response characteristics at the knee under functional, weight-bearing conditions while controlling for training and other confounding variables. The limitations of sEMG should be considered when interpreting neuromuscular response studies. PMID:16558560

Shultz, Sandra J.; Perrin, David H.

1999-01-01

258

Flow-induced vibrations-1987  

SciTech Connect

This book contains 20 selections. Some of the titles are: Acoustic resonance in heat exchanger tube bundles--Part 1. Physical nature of the phenomenon; Theoretical and experimental studies on heat exchanger U-bend tube bundle vibration characteristics; Experimental model analysis of metallic pipeline conveying fluid; Leakage flow-induced vibration of an eccentric tube-in-tube slip joint; and A study on the vibrations of pipelines caused by internal pulsating flows.

Au-Yang, M.K.; Chen, S.S.

1987-01-01

259

Torsional vibration reduction using passive nonlinear absorbers  

NASA Astrophysics Data System (ADS)

This paper considers the dynamic performance of systems of centrifugal pendulum vibration absorbers that are used to attenuate torsional vibrations in rotating systems. These absorbers, which can be found in certain IC engines and helicopter rotors, consist of movable masses whose centers of mass are kinematically restricted to move along prescribed paths relative to the rotor of interest. The most common choice for absorber paths are simple circles that are slightly mistuned from the desired order, so that undesirable nonlinear behaviors are avoided when the absorbers undergo large amplitude motions. In this work we consider a range of different path types and tunings, with the goal of optimizing performance over a wide operating range. This analytical study relies on a mathematical model of a rotor fitted with N identical, general-path absorbers, and utilizes perturbation techniques to obtain analytical estimates for the response of the rotor and the absorbers. The results are used to select path parameters based on selected performance measures, and the results are verified via simulation studies. It is shown that slightly overtuned cycloidal paths provide excellent vibration reduction characteristics and prevent the occurrence of nonlinear instabilities and vibration localization in the response of the absorbers.

Shaw, Steven W.; Alsuwaiyan, Abdallah

2000-04-01

260

Vibration therapy.  

PubMed

Whole-body vibration training is a method for muscle strengthening that is increasingly used in a variety of clinical situations. Key descriptors of vibration devices include the frequency, the amplitude, and the direction of the vibration movement. In a typical vibration session, the user stands on the device in a static position or performs dynamic movements. Most authors hypothesize that vibrations stimulate muscle spindles and alpha-motoneurons, which initiate a muscle contraction. An immediate effect of a non-exhausting vibration session is an increase in muscle power. Most studies of the longer term use of vibration treatment in various disorders have pursued three therapeutic aims: increasing muscle strength, improving balance, and increasing bone mass. In a small pilot trial in children we noted improvements in standing function, lumbar spine bone mineral density, tibial bone mass, and calf muscle cross-sectional area. PMID:19740225

Rauch, Frank

2009-10-01

261

[The effect of whole-body vibration: an unrecognized medical problem].  

PubMed

Exposure to whole-body vibration is a growing concern in industry, traffic and in other branches of the economy. This harmful physical factor endangers work efficiency and human health not only at work but also in everyday life, in public transportation and even at home. In spite of increasing exposure to vibrations, our medical practice does not pay adequate attention to the health effects of whole-body vibration. The paper deals with the basic characteristics of vibration (frequency, amplitude, velocity and acceleration), its adequate evaluation (effective or weighted average value, peak values, rating and weighting procedure of vibration measurement) and exposure (vibration direction, exposure time, transmission and dissipation). In industry and traffic, vibrations present complex oscillatory motions, characterized by a wide frequency spectrum, variable amplitude and acceleration, and different directions. To assess the harmful effects of vibration, the International Organization for Standardization (ISO) has proposed three standards for acceptable human exposure to whole-body vibration: fatigue-decreased proficiency boundary, exposure limit and reduced comfort boundary. Quantitative parameters of vibration for some vehicles, and for constructional, industrial and agricultural machinery are also given. The most pronounced long-term effect of whole-body vibration is damage to the spine. The spinal region most frequently affected is the lumbar part, where spinal deformation, lumbago and sciatica can develop. The possible cause of spinal damage could be mechanical overload and metabolic changes of the intervertebral disc. Other organ systems, such as peripheral and autonomic nervous, vestibular, vascular, digestive and female reproductive systems are also liable to become affected. Risk assessment of chronic health effects is based on the appropriate evaluation of whole-body vibration exposure and individual response. Health risk increases with the intensity and duration of vibration exposure. The concomitant factors are forced sitting posture and heavy physical work. Human response to whole-body vibration depends on factors promoting the development of degenerative changes such as constitution, previous spine disease and young age. The main problems in diagnosing whole-body vibration syndrome are differentiation of vibration induced disorders from age dependent changes of the spine and lack of a specific diagnostic method for assessing those changes. Therefore, only permanent medical surveillance can guarantee proper assessment of the damage induced by whole-body vibration. For vibration exposed workers preplacement and periodic examinations are recommended. Those should include a basic medical examination and an X-ray of the spine, or at least of its lumbar part. PMID:8311700

Bogadi-Sare, A

1993-09-01

262

Characteristics of identifying linear dynamic models from impulse response data using Prony analysis  

SciTech Connect

The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general rules-of-thumb'' for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

Trudnowski, D.J.

1992-12-01

263

Characteristics of invertebrates consumed by mallards and prey response to wetland flooding schedules  

Microsoft Academic Search

We examined characteristics of the invertebrates consumed by mallards (Anas platyrhynchos) and green-winged teals (Anas crecca) and responses of these invertebrates to manipulations of flooding date in Suisun Marsh, Solano County, CA. Numbers ofChironomus stigmaterus midge larvae (Chironomidae) andEogammarus confervicolus amphipods (Gammaridae) in mallard esophageal samples were positively correlated with abundance of these invertebrates in\\u000a wetlands. Mallards primarily consumed large

Darold P. Batzer; Monica McGee; Vincent H. Resh; R. Robert Smith

1993-01-01

264

Characteristics of identifying linear dynamic models from impulse response data using Prony analysis  

SciTech Connect

The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general ``rules-of-thumb`` for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

Trudnowski, D.J.

1992-12-01

265

Experimental implementation of switching and sweeping tuneable vibration absorbers for broadband vibration control  

NASA Astrophysics Data System (ADS)

This paper describes the laboratory implementation of two semi-active tuned vibration absorbers (TVAs): a switching TVA and a sweeping TVA. The two absorbers are designed to control the low frequency total flexural response of a cylindrical duct excited by a stationary broadband random force. The two TVAs are composed by a seismic mass mounted on a axial spring. Both TVAs are equipped with a relative displacement and relative velocity feedback control system, which is used to vary the characteristic stiffness and damping, that is the characteristic natural frequency and damping ratio, of the TVA. The switching TVA cyclically tunes its characteristic natural frequency and damping ratio to iteratively control the resonant responses due to three targeted flexural natural modes of the duct. Alternatively the sweeping TVA continuously varies its characteristic natural frequency and damping ratio within given ranges to blindly control the resonant responses due to the same three flexural natural modes of the duct. The paper presents both simulation and experimental results regarding the feedback loop used to iteratively or continuously tune the TVAs and about the reduction of vibration produced by the two semi-active TVAs. The simulation and the experimental results show that both TVAs effectively control the flexural response of the duct in the low frequency band, which is characterised by the resonances of the three targeted flexural natural modes of the duct.

Zilletti, Michele; Gardonio, Paolo

2015-01-01

266

A global statistical model based approach for vibration response-only damage detection under various temperatures: A proof-of-concept study  

NASA Astrophysics Data System (ADS)

The statistical damage detection in a composite beam structure operating under different temperatures is considered based on vibration response-only signals. For this purpose a novel stochastic global model approach is introduced based upon statistical hypothesis testing and identified Functionally Pooled models capable of describing the temperature-dependent dynamics. Two versions of the approach that use either modal or discrete-time model parameters are postulated. This is a proof-of-concept study in which the effectiveness of the approach is confirmed via laboratory experiments. Comparisons with alternative methods attempting removal of the temperature effects from the damage-sensitive features are also made.

Hios, J. D.; Fassois, S. D.

2014-12-01

267

Application of magnetorheological elastomer to vibration absorber  

Microsoft Academic Search

Traditional dynamic vibration absorber (DVA) is widely used in industries as a vibration absorption equipment. However, it is only effective at narrow working frequency range. This shortcoming has limited its stability and application. This paper develops an adaptive tuned vibration absorber (ATVA) based on unique characteristics of magnetorheological elastomers (MREs), whose modulus can be controlled by an applied magnetic field.

Hua-Xia Deng; Xing-Long Gong

2008-01-01

268

Response Characteristics Of Laser Diffraction Particle Size Analyzers: Optical Sample Volume Extent And Lens Effects  

NASA Astrophysics Data System (ADS)

The response characteristics of laser diffraction particle sizing instruments were studied theoretically and experimentally. In particular, the extent of optical sample volume and the effects of receiving lens properties were investigated in detail. The experimental work was performed with a Malvern Instruments Ltd. Model 2200 particle size analyzer using a calibration reticle containing a two-dimensional array of opaque circular disks on a glass substrate. The calibration slide simulated the forward-scattering characteristics of a Rosin-Rammler droplet size dis-tribution. The reticle was analyzed with collection lenses of 63 mm, 100 mm, and 300 mm focal lengths using scattering inversion software that determined best-fit Rosin-Rammler size distribution parameters. The Malvern 2200 data differed from the predicted response for the reticle by about 10%. The discrepancies are attributed to nonideal effects in the detector elements and the lenses. A set of calibration factors for the detector elements was determined here that corrected for the nonideal response of the instrument. The response of the instrument was also measured as a function of reticle position, and the results confirmed a theoretical optical sample volume model presented here.

Hirleman, E. D.; Oechsle, V.; Chigier, N. A.

1984-10-01

269

Response characteristics of laser diffraction particle size analyzers - Optical sample volume extent and lens effects  

NASA Technical Reports Server (NTRS)

The response characteristics of laser diffraction particle sizing instruments were studied theoretically and experimentally. In particular, the extent of optical sample volume and the effects of receiving lens properties were investigated in detail. The experimental work was performed with a particle size analyzer using a calibration reticle containing a two-dimensional array of opaque circular disks on a glass substrate. The calibration slide simulated the forward-scattering characteristics of a Rosin-Rammler droplet size distribution. The reticle was analyzed with collection lenses of 63 mm, 100 mm, and 300 mm focal lengths using scattering inversion software that determined best-fit Rosin-Rammler size distribution parameters. The data differed from the predicted response for the reticle by about 10 percent. A set of calibration factor for the detector elements was determined that corrected for the nonideal response of the instrument. The response of the instrument was also measured as a function of reticle position, and the results confirmed a theoretical optical sample volume model presented here.

Hirleman, E. D.; Oechsle, V.; Chigier, N. A.

1984-01-01

270

Damping phenomena in a wire rope vibration isolation system  

NASA Technical Reports Server (NTRS)

A study is presented of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators, with emphasis placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase plane trajectories, and frequency response curves are obtained. A semiempirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed, and the results are compared to experimental data. Several observations and conclusions are made about the dynamic phenomena in a typical wire rope vibration isolation system based on the experimental and semiempirical results.

Tinker, M. L.; Cutchins, M. A.

1992-01-01

271

Variational study on the vibrational level structure and IVR behavior of highly vibrationally excited S0 formaldehyde.  

PubMed

We perform large scale converged variational vibrational calculations on S(0) formaldehyde up to very high excess vibrational energies (E(v)), E(v)?17,000cm(-1), using our vibrational method, consisting of a specific search/selection/Lanczos iteration procedure. Using the same method we investigate the vibrational level structure and intramolecular vibrational redistribution (IVR) characteristics for various vibrational levels in this energy range in order to assess the onset of IVR. PMID:22185953

Rashev, Svetoslav; Moule, David C

2012-02-15

272

Good Vibrations  

NSDL National Science Digital Library

This lesson (on pages 15-24 of PDF) explores how sound is caused by vibrating objects. It explains that we hear by feeling vibrations passing through the air. Learners take part in several demonstrations, making those vibrations visible. They put a tuning fork in a shallow pan of water and use it to bounce a ping-pong ball, showing the fact that the tuning fork is vibrating when it's making a sound. There are extensions described involving comb kazoos, rubber band guitars, and putting rice or cereal on top of a drum.

2012-06-26

273

Experimental Investigation of the Vibration Characteristics of Four Designs of Turbine Blades and of the Effect Produced by Varying the Axial Spacing Between Nozzle Blades and Turbine Blades.  

NASA Technical Reports Server (NTRS)

An investigation was made to determine the effects of varying the spacing between the nozzle blades and the turbine blades of a turbo-jet engine on turbine-blade vibration for four turbine-blade designs of different degrees of stiffness. In general, there was a tendency toward increase in occurrence of vibration with decrease in spacing. The effect was most evident in the case of the turbine blades that had greater stiffness.

Morgan, W C; Morse, C R

1952-01-01

274

A numerical analysis of the influence of tram characteristics and rail profile on railway traffic ground-borne noise and vibration in the Brussels Region.  

PubMed

Nowadays, damage potentially caused by passing train in dense cities is of increasing concern and restricts improvement to the interconnection of various public transport offers. Although experimental studies are common to quantify the effects of noise and vibration on buildings and on people, their reach is limited since the causes of vibrations can rarely be deduced from data records. This paper presents the numerical calculations that allow evaluating the main contributions of railway-induced ground vibrations in the vicinity of buildings. The reference case is the Brussels Region and, more particularly, the T2000 tram circulating in Brussels city. Based on a pertinent selection of the vibration assessment indicators and a numerical prediction approach, various results are presented and show that the free-field analysis is often improperly used in this kind of analysis as the interaction of soil and structure is required. Calculated high ground vibrations stem from singular rail surface defects. The use of resilient wheels is recommended in order to reduce the ground-borne noise and vibration to permissible values. PMID:23786851

Kouroussis, G; Pauwels, N; Brux, P; Conti, C; Verlinden, O

2014-06-01

275

Dynamic response characteristics of dual flow-path integrally bladed rotors  

NASA Astrophysics Data System (ADS)

New turbine engine designs requiring secondary flow compression often look to dual flow-path integrally bladed rotors (DFIBRs) since these stages have the ability to perform work on the secondary, or bypassed, flow-field. While analogous to traditional integrally bladed rotor stages, DFIBR designs have many differences that result in unique dynamic response characteristics that must be understood to avoid fatigue. This work investigates these characteristics using reduced-order models (ROMs) that incorporate mistuning through perturbations to blade frequencies. This work provides an alternative to computationally intensive geometric-mistuning approaches for DFIBRs by utilizing tuned blade mode reductions and substructure coupling in cyclic coordinates. Free and forced response results are compared to full finite element model (FEM) solutions to determine if any errors are related to the reduced-order model formulation reduction methods. It is shown that DFIBRs have many more frequency veering regions than their single flow-path integrally blade rotor (IBR) counterparts. Modal families are shown to transition between system, inner-blade, and outer-blade motion. Furthermore, findings illustrate that while mode localization of traditional IBRs is limited to a single or small subset of blades, DFIBRs can have modal energy localized to either an inner- or outer-blade set resulting in many blades responding above tuned levels. Lastly, ROM forced response predictions compare well to full FEM predictions for the two test cases shown.

Beck, Joseph A.; Brown, Jeffrey M.; Scott-Emuakpor, Onome E.; Cross, Charles J.; Slater, Joseph C.

2015-02-01

276

Research on the response characteristics of solenoid valve of the air-jet loom by simulation  

NASA Astrophysics Data System (ADS)

Solenoid valve is one of the executive parts of weft insertion control system. According to the response characteristics of the solenoid valve, an improved design becomes a necessity. Firstly, the numerical model was established after analyzing the solenoid valve during its start-up and shut-down. Comparing the simulation data with the practical data, it is verified that the numerical simulation model has a high feasibility. Secondly, excitation voltage and spring pre-compression were adjusted respectively, and the response rules after adjusting were investigated. The research of the study shows: the response time tends to be inverse proportional to the excitation voltage during start-up, and it becomes a constant value with the increase of the excitation voltage; the response time is proportional to the spring pre-compression when the solenoid valve starts up, it is inverse proportional to spring pre-compression when the solenoid valve shuts down. And the total response time is a constant value with the increase of the spring pre-compression. Therefore, the value of the excitation voltage and the spring pre-compression should be selected when the curve is becoming flatten. The results of the research can provide the reference to the further development of the solenoid valve.

Jin, Yuzhen; Deng, Ruoyu; Jin, Yingzi; Hu, Xudong

2013-12-01

277

Research and optimization of the ESD response characteristic in a ps-LDMOS transistor  

NASA Astrophysics Data System (ADS)

The ESD response characteristic in a p-type symmetric lateral DMOS (ps-LDMOS) has been investigated. The experimental results show that the ps-LDMOS has weak ESD robustness due to an absence of the “snapback" characteristic. In addition, the location of the hot spot changes little for the special device. The method for reducing the lattice temperature of the hot spot can be used to enhance the ESD capacity of the ps-LDMOS, thereby, a novel and easily-achievable ps-LDMOS structure with a p-type lightly doped drain (p-LDD) has been proposed. The special region p-LDD lowers the electric field at the edge of the poly gate, making the whole distribution of the surface electric field more uniform. Therefore, the ESD robustness is improved two times and no obvious change of other electric parameters is introduced.

Hao, Wang; Siyang, Liu; Weifeng, Sun; Tingting, Huang

2014-01-01

278

Parametric Optimization of Ares I Propellant Slosh Characteristics Using Frequency Response Criteria  

NASA Technical Reports Server (NTRS)

A novel technique for developing propellant slosh damping requirements with respect to the stability characteristics of large flexible launch vehicles is presented. A numerical algorithm is devised which allows an automated software program to rapidly converge to pseudo-optimal solutions that minimize required propellant slosh damping for multiple tanks while maintaining constraints on the frequency response characteristics of a particular open-loop plant transfer function. An implementation of the algorithm using a high-order linear model of the Ares I plant dynamics considers all relevant dynamic interactions of flexible body modes, propellant slosh, and nozzle inertia effects. A high-resolution propellant damping requirements table is produced that can be used for baffle design. The method is demonstrated to provide exceptional speed and accuracy when compared with the alternative human-in-the-loop approach.

Orr, Jeb S.; Hall, Charles E.

2009-01-01

279

Role of growth temperature on the frequency response characteristics of pentacene-based organic devices  

NASA Astrophysics Data System (ADS)

The ac frequency response characteristics (FRC) of organic thin film transistors and metal-insulator semiconductor diodes were highly improved by controlling the morphology and electrical characteristics of semiconducting pentacene films. The devices with films grown at 50 °C show much higher cutoff frequency and better frequency stability of flat-band voltage, as compared to those with films grown at other temperatures below or above. The improvement mainly originates from the maximum field effect carrier mobility of 0.78 cm2 V?1 s?1 and a small metal/organic contact resistance (Rc) obtained in the optimum thin film transistors. Our results indicate growth temperature precisely tunes the film microstructure and metal/semiconductor interface, which together determine the FRC of pentacene-based organic devices.

Shao, Yayun; Zhang, Yang; He, Wenqiang; Liu, Chuan; Minari, Takeo; Wu, Sujuan; Zeng, Min; Zhang, Zhang; Gao, Xingsen; Lu, Xubing; Liu, J.-M.

2015-03-01

280

Good Vibrations  

NSDL National Science Digital Library

In this activity, learners experiment with their voices and noisemakers to understand the connections between vibrations and the sounds created by those vibrations. This resource includes three quick demonstration activities that can be used independently or as a group to introduce learners to the basic elements of sound.

OMSI

2004-01-01

281

Vibrational Coupling  

SciTech Connect

By homing in on the distribution patterns of electrons around an atom, a team of scientists team with Berkeley Lab's Molecular Foundry showed how certain vibrations from benzene thiol cause electrical charge to "slosh" onto a gold surface (left), while others do not (right). The vibrations that cause this "sloshing" behavior yield a stronger SERS signal.

None

2011-01-01

282

Localised Muscle Tissue Oxygenation During Dynamic Exercise With Whole Body Vibration  

PubMed Central

Despite increasing use of whole body vibration during exercise an understanding of the exact role of vibration and the supporting physiological mechanisms is still limited. An important aspect of exercise analysis is the utilisation of oxygen, however, there have been limited studies considering tissue oxygenation parameters, particularly during dynamic whole body vibration (WBV) exercise. The aim of this study was to determine the effect of adding WBV during heel raise exercises and assessing changes in tissue oxygenation parameters of the lateral gastrocnemius using Near Infra Red Spectroscopy (NIRS). Twenty healthy subjects completed ten alternating sets of 15 heel raises (vibration vs. no vibration). Synchronous oxygenation and motion data were captured prior to exercise to determine baseline levels, for the duration of the exercise and 20 sec post exercise for the recovery period. Both vibration and no vibration conditions elicited a characteristic increase in deoxyhaemoglobin and decreases in oxyhaemoglobin, total haemoglobin, tissue oxygenation index and normalised tissue haemoglobin index which are indicative of local tissue hypoxia. However, the addition of vibration elicited significantly lower (p < 0. 001) depletions in oxyhaemoglobin, total haemoglobin, normalised tissue haemoglobin index but no significant differences in deoxyhaemoglobin. These findings suggest that addition of vibration to exercise does not increase the cost of the exercise for the lateral gastrocnemius muscle, but does decrease the reduction in local muscle oxygenation parameters, potentially resulting from increased blood flow to the calf or a vasospastic response in the feet. However, further studies are needed to establish the mechanisms underlying these findings. Key pointsWhole body vibration affects tissue oxygenation of the lateral gastrocnemius.The underlying mechanism could be either increased blood flow or a vasospastic response in the feet.The local metabolic cost of heel raise activity on the lateral gastrocnemius does not appear to be increased by whole body vibration. PMID:24149209

Robbins, Daniel; Elwell, Clare; Jimenez, Alfonso; Goss-Sampson, Mark

2012-01-01

283

Transient and frequency response characteristics of two-phase condensing flows - with and without compressibility  

NASA Astrophysics Data System (ADS)

In a tube-type condenser, involving complete condensation, small changes in the inlet vapor flowrate momentarily cause very large transient surges in the outlet liquid flowrate. Experimental data are presented which indicate that compressibility effects tend to attenuate the amplitude of these flow surges. The system mean void fraction model was extended to include compressibility effects and its predictions are shown to agree well with experimental data. The model is further extended to predict the response characteristics to an oscillatory inlet flowrate and compared with predictions based upon the drift-flux model.

Bhatt, B. L.; Wedekind, G. L.

1980-08-01

284

Performance of some coupling methods for blast vibration monitoring  

NASA Astrophysics Data System (ADS)

Field guidelines and recommendations for blasting vibration monitoring on a hard surface, suggest that the geophone mount should be coupled to the ground in a way that depends on the anticipated vibration level. However, the quantitative performance of the coupling method is basically unknown. In order to investigate this, the ground-to-mount coupling transmissibility (i.e. ratio of the response of the geophones mount to the rock motion, as a function of frequency) was measured between 16 and 200 Hz in 43 tests using a vibration exciter. The geophone mounts were freely placed, hold with a sandbag and anchored on granite. Free placed mounts applied outside the suggested range of vibrations (i.e. frequencies above 50-70 Hz at 5 mm/s) lead to the largest expected errors (up to 7.5 dB). Distortion is still significant (1.02 dB), though to a minor degree, at lower levels where this method is recommended. Sandbagging limits the maximum expected error to 1.6 dB, but it is ranked as the worst method irrespective of the vibration level and the sandbag planting at frequencies below 40 Hz. Anchoring appears as the only analyzed method that achieves a stiff rock-to-mount coupling, ensuring consistent measurements for the frequencies commonly found in blasting independently of the vibration level and the mount characteristics.

Segarra, P.; Sanchidrián, J. A.; Castedo, R.; López, L. M.; del Castillo, I.

2015-01-01

285

Dose response characteristics of polymethacrylic acid gel (PMAAG) for a polymerization-based dosimeter using NMR.  

PubMed

The radiation-response characteristics of polymetharylic acid gel dosimeter prepared with different concentrations of monomer and cross-linker is described in these studies. The dosimeters were prepared under the hypoxic condition in a glove box and were then irradiated with gamma-rays produced by Co-60 radionuclide that was generated at 1.25MeV energy. The irradiation took place at different doses ranged from 0Gy to 19Gy. Due to the radiation activities, chain-reaction polymerisation processes had taken place in the formation of polymethacrylic acid (PMAA) gel, which cause the dose response mechanism increased in the NMR relaxation rates of protons. It has been observed that for higher concentration of monomer and cross-linker, the polymerization rate was increased. PMID:15468893

Iskandar, S M; Elias, S; Jumiah, H; Asri, M T M; Masrianis, A; Ab Rahman, M Z; Taiman, K; Abdul Rashid, M Y

2004-05-01

286

Dynamic response of active twist rotor blades  

Microsoft Academic Search

Dynamic characteristics of active twist rotor (ATR) blades are investigated analytically and experimentally in this paper. The ATR system is intended for vibration and potentially for noise reductions in helicopters through individual blade control. An aeroelastic model is developed to identify frequency response characteristics of the ATR blade with integral, generally anisotropic, strain actuators embedded in its composite construction. An

Carlos E. S. Cesnik; Sang Joon Shin; Matthew L. Wilbur

2001-01-01

287

Fourier Analysis Of Vibrations Of Round Structures  

NASA Technical Reports Server (NTRS)

Fourier-series representation developed for analysis of vibrations in complicated, round structures like turbopump impellers. Method eliminates guesswork involved in characterization of shapes of vibrational modes. Easy way to characterize complicated modes, leading to determination of responsiveness of given mode to various forcing functions. Used in conjunction with finite-element numerical simulation of vibrational modes of structure.

Davis, Gary A.

1990-01-01

288

ROCView: prototype software for data collection in jackknife alternative free-response receiver operating characteristic analysis  

PubMed Central

ROCView has been developed as an image display and response capture (IDRC) solution to image display and consistent recording of reader responses in relation to the free-response receiver operating characteristic paradigm. A web-based solution to IDRC for observer response studies allows observations to be completed from any location, assuming that display performance and viewing conditions are consistent with the study being completed. The simplistic functionality of the software allows observations to be completed without supervision. ROCView can display images from multiple modalities, in a randomised order if required. Following registration, observers are prompted to begin their image evaluation. All data are recorded via mouse clicks, one to localise (mark) and one to score confidence (rate) using either an ordinal or continuous rating scale. Up to nine “mark-rating” pairs can be made per image. Unmarked images are given a default score of zero. Upon completion of the study, both true-positive and false-positive reports can be downloaded and adapted for analysis. ROCView has the potential to be a useful tool in the assessment of modality performance difference for a range of imaging methods. PMID:22573294

Thompson, J; Hogg, P; Thompson, S; Manning, D; Szczepura, K

2012-01-01

289

Comprehensive studies of response characteristics of organic photodetectors based on rubrene and C60  

NASA Astrophysics Data System (ADS)

We studied the transient response characteristics of organic photodetectors composing of high mobility materials of rubrene and C60, respectively, as donor and acceptor. It was found that the response speed was limited by the delay time of both exciton diffusion and transit, and an anomalous phenomenon that the bandwidth decreases as the reverse bias increases was found for the first time. The investigation of frequency dependence at different device structures and light excitations demonstrated that the light absorption of rubrene prevents the photodetector from obtaining a fast response. With the help of magnetic field effect study, it was clearly elucidated that the slow diffusion time of the long lifetime triplet excitons generated from singlet fission in rubrene limited the bandwidth of the device. Moreover, the simulation of the response of photodetector under transient and steady state by exciton transport-diffusion equation showed that the exciton dissociation efficiency in rubrene increases more quickly than that in C60, which should account for the negative dependence of bandwidth on the reverse bias in rubrene-based device.

Yang, Dezhi; Xu, Kai; Zhou, Xiaokang; Wang, Yanping; Ma, Dongge

2014-06-01

290

Comprehensive studies of response characteristics of organic photodetectors based on rubrene and C{sub 60}  

SciTech Connect

We studied the transient response characteristics of organic photodetectors composing of high mobility materials of rubrene and C{sub 60}, respectively, as donor and acceptor. It was found that the response speed was limited by the delay time of both exciton diffusion and transit, and an anomalous phenomenon that the bandwidth decreases as the reverse bias increases was found for the first time. The investigation of frequency dependence at different device structures and light excitations demonstrated that the light absorption of rubrene prevents the photodetector from obtaining a fast response. With the help of magnetic field effect study, it was clearly elucidated that the slow diffusion time of the long lifetime triplet excitons generated from singlet fission in rubrene limited the bandwidth of the device. Moreover, the simulation of the response of photodetector under transient and steady state by exciton transport-diffusion equation showed that the exciton dissociation efficiency in rubrene increases more quickly than that in C{sub 60}, which should account for the negative dependence of bandwidth on the reverse bias in rubrene-based device.

Yang, Dezhi; Xu, Kai; Zhou, Xiaokang; Wang, Yanping; Ma, Dongge, E-mail: mdg1014@ciac.ac.cn [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

2014-06-28

291

Poroelastic response of articular cartilage by nanoindentation creep tests at different characteristic lengths.  

PubMed

Nanoindentation is an experimental technique which is attracting increasing interests for the mechanical characterization of articular cartilage. In particular, time dependent mechanical responses due to fluid flow through the porous matrix can be quantitatively investigated by nanoindentation experiments at different penetration depths and/or by using different probe sizes. The aim of this paper is to provide a framework for the quantitative interpretation of the poroelastic response of articular cartilage subjected to creep nanoindentation tests. To this purpose, multiload creep tests using spherical indenters have been carried out on saturated samples of mature bovine articular cartilage achieving two main quantitative results. First, the dependence of indentation modulus in the drained state (at equilibrium) on the tip radius: a value of 500 kPa has been found using the large tip (400 ?m radius) and of 1.7 MPa using the smaller one (25 ?m). Secon, the permeability at microscopic scale was estimated at values ranging from 4.5×10(-16) m(4)/N s to 0.1×10(-16) m(4)/N s, from low to high equivalent deformation. Consistently with a poroelastic behavior, the size-dependent response of the indenter displacement disappears when characteristic size and permeability are accounted for. For comparison purposes, the same protocol was applied to intrinsically viscoelastic homogeneous samples of polydimethylsiloxane (PDMS): both indentation modulus and time response have been found size-independent. PMID:24814573

Taffetani, M; Gottardi, R; Gastaldi, D; Raiteri, R; Vena, P

2014-07-01

292

Comparison of aortic and carotid baroreflex stimulus-response characteristics in humans  

NASA Technical Reports Server (NTRS)

In order to characterize the stimulus-response relationships of the arterial, aortic, and carotid baroreflexes in mediating cardiac chronotropic function, we measured heart rate (HR) responses elicited by acute changes in mean arterial pressure (MAP) and carotid sinus pressure (CSP) in 11 healthy individuals. Arterial (aortic + carotid) baroreflex control of HR was quantified using ramped changes in MAP induced by bolus injection of phenylephrine (PE) and sodium nitroprusside (SN). To assess aortic-cardiac responses, neck pressure (NP) and suction (NS) were applied during PE and SN administration, respectively, to counter alterations in CSP thereby isolating the aortic baroreflex. Graded levels of NP and NS were delivered to the carotid sinus using a customized neck collar device to assess the carotid-cardiac baroreflex, independent of drug infusion. The operating characteristics of each reflex were determined from the logistic function of the elicited HR response to the induced change in MAP. The arterial pressures at which the threshold was located on the stimulus-response curves determined for the arterial, aortic and carotid baroreflexes were not significantly different (72+/-4, 67+/-3, and 72+/-4 mm Hg, respectively, P > 0.05). Similarly, the MAP at which the saturation of the reflex responses were elicited did not differ among the baroreflex arcs examined (98+/-3, 99+/-2, and 102+/-3 mm Hg, respectively). These data suggest that the baroreceptor populations studied operate over the same range of arterial pressures. This finding indicates each baroreflex functions as both an important anti-hypotensive and anti-hypertensive mechanism. In addition, this investigation describes a model of aortic baroreflex function in normal healthy humans, which may prove useful in identifying the origin of baroreflex dysfunction in disease- and training-induced conditions.

Smith, S. A.; Querry, R. G.; Fadel, P. J.; Weiss, M. W.; Olivencia-Yurvati, A.; Shi, X.; Raven, P. B.

2001-01-01

293

Random vibrations of swings  

NASA Astrophysics Data System (ADS)

The paper considers a problem of random vibrations of swings—a pendulum with variable length. The goal of the paper is to estimate mean response energy of the system, subjected to external Gaussian white noise. The Energy Balance method is used to derive analytical results.

Iourtchenko, Daniil V.

2006-05-01

294

Evaluation of space shuttle main engine fluid dynamic frequency response characteristics  

NASA Technical Reports Server (NTRS)

In order to determine the POGO stability characteristics of the space shuttle main engine liquid oxygen (LOX) system, the fluid dynamic frequency response functions between elements in the SSME LOX system was evaluated, both analytically and experimentally. For the experimental data evaluation, a software package was written for the Hewlett-Packard 5451C Fourier analyzer. The POGO analysis software is documented and consists of five separate segments. Each segment is stored on the 5451C disc as an individual program and performs its own unique function. Two separate data reduction methods, a signal calibration, coherence or pulser signal based frequency response function blanking, and automatic plotting features are included in the program. The 5451C allows variable parameter transfer from program to program. This feature is used to advantage and requires only minimal user interface during the data reduction process. Experimental results are included and compared with the analytical predictions in order to adjust the general model and arrive at a realistic simulation of the POGO characteristics.

Gardner, T. G.

1980-01-01

295

Characteristic-Wave Approach Complements Modal Analysis  

NASA Technical Reports Server (NTRS)

Aspects of estimation of unmodeled dynamics discussed. Report discusses solution of nonhomogeneous governing matrix equation for dynamics of short vibrational pulses propagating as characteristic waves in large structure. Applied to analyze response, to repeated pulses, of beam clamped at one end and free at other. Shows all qualitative characteristics occuring under arbitrary periodic excitations of beam and those of quasi-periodic excitations, in as much as such excitations obtained by linear superpositions of periodic excitations.

Zak, Michail

1990-01-01

296

Enhanced dielectric polarization and electro-responsive characteristic of graphene oxide-wrapped titania microspheres.  

PubMed

Electric field-induced particle polarization is essential to the electro-responsive electrorheological (ER) effect of particle suspensions. In this work, we use graphene oxide (GO) as a soft and polar coating shell to prepare GO-wrapped titania dielectric microspheres for use as the dispersal phase of an ER suspension. Under a DC electric field, the ER characteristic of GO-wrapped titania microspheres dispersed in silicone oil is investigated by rheological tests, and then compared with that of a suspension of bare titania microspheres. The results show that the suspension of GO-wrapped titania microspheres possesses an enhanced ER characteristic. Its field-induced shear yield stress and storage modulus are much higher than those of the suspension of bare titania microspheres. The soft and polar GO shell is regarded as the origin of the ER enhancement. Dielectric analysis indicates that wrapping GO can enhance the interfacial polarization and thus improve the ER characteristics of titania microspheres. Wrapping GO onto the surface of titania microspheres can also reduce the particle sedimentation velocity of the suspension. PMID:24394540

Yin, Jianbo; Shui, Yongjun; Dong, Yuezhen; Zhao, Xiaopeng

2014-01-31

297

An experimental investigation of dual-resonant and non-resonant responses for vortex-induced vibration of a long slender cylinder  

NASA Astrophysics Data System (ADS)

Experimental results of the dual-resonant and non-resonant responses are presented for vortex-induced vibrations (VIV) of a long slender cylinder. The cylinder has a diameter of 10mm and a length of 3.31 m, giving an aspect ratio of 331. The cylinder was towed by a carriage with the velocity up to 1.5 m/s, with the Reynolds number varying from 2500 to 38000. Three different weights were used to provide the initial tension. Dual resonance means that resonance occurs simultaneously in both the cross-flow (CF) and in-line (IL) directions. The experiments were conducted in two stages. At the first stage, dual-resonant dynamic features of the cylinder subjected to vortex-induced excitation were investigated. The features of CF and IL vibration amplitude, motion orbits, phase angle differences, dominant frequencies and mode order numbers are presented. At the second stage of the experiments, particular emphasis was placed on non-resonant dynamic features. The variation of multi-mode modal displacement amplitudes was investigated in detail.

Wu, XiaoDong; Ge, Fei; Hong, YouShi

2014-01-01

298

Discomfort criteria for single-axis vibrations  

NASA Technical Reports Server (NTRS)

Experimental investigations were conducted to determine the fundamental relationships governing human subjective discomfort response to single-axis vibrations. The axes investigated were vertical, lateral, longitudinal, roll, and pitch, and the vibrations used were both sinusoidal and random in nature. Results of these investigations provided the basis for: (1) development of a scale of passenger discomfort that is common to all axes of vibration; and (2) generation of discomfort criteria for each axis of each axis and for both types of vibration. Furthermore, empirical equations describing discomfort responses within each axis of vibration are included.

Dempsey, T. K.; Leatherwood, J. D.; Clevenson, S. A.

1979-01-01

299

Vibration Labs to Help Achieve a Resonance in Learning  

NSDL National Science Digital Library

A sequence of laboratories has been designed and implemented in an undergraduate course in mechanical vibrations to introduce students to experimental aspects of vibrations and experimental modal analysis. Unfortunately, undergraduate vibration courses, especially if they do not have a lab associated with them, are often perceived by many students to be courses in differential equations. By exposing students to vibration measurement instrumentation such as accelerometers and dynamic signal analyzers, and by allowing them to take experimental data, calculate frequency response functions, and identify system parameters and mode shapes, student learning and motivation is enhanced. One characteristic of the labs described in this paper, in contrast to other vibrations labs discussed in the literature, is the way each lab builds upon the previous one and the fact students test real engineering structures. The initial labs in the course use Electronic Control Products (ECP) hardware and introduce the idea of frequency response functions (FRFs) and system identification. After students are familiar with these ideas, they progress to using PHOTON IIs (a 32 bit, 4 channel data acquisition system), RT Pro for data acquisition and signal processing, and DIAMOND for system identification and mode shape animation. In this paper the labs will be described and assessment results presented as to their efficacy.

Cornwell, Philip

2011-06-22

300

Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod  

USGS Publications Warehouse

We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding (flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately. In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both years. Assimilation-light response curves indicated that the different hydroperiods had little effect on leaf gas exchange characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation, and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod shifts in many settings. ?? 2006 Heron Publishing.

Krauss, K.W.; Twilley, R.R.; Doyle, T.W.; Gardiner, E.S.

2006-01-01

301

Vibration of a large space beam under gravity effect  

NASA Technical Reports Server (NTRS)

Future space structures will have a low mass density and high flexibility, with ground test dynamic behavior differing significantly from that in zero-G orbit. Attention is presently given to the vibration behavior of a beam deformed by its own weight; the results obtained by the differential equations for both the static and dynamic responses of a large, simply supported beam, which are derived and solved analytically, allow ground test experiment measurements to be used for orbital dynamic characteristics verification efforts.

Shih, C.-F.; Chen, J. C.; Garba, J.

1986-01-01

302

The vibrations of texture  

PubMed Central

The Pacinian channel has been implicated in the perception of fine textures (Hollins et al., Somatosens Mot Res 18: 253–262, 2001a). In the present study, we investigate candidate codes for Pacinian-mediated roughness perception. We use a Hall effect transducer to record the vibrations elicited in the skin when a set of textured surfaces is passively presented to the index finger. The peak frequency of the vibrations is found to decrease systematically as spatial period increases. The power of the vibrations—weighted according to the spectral sensitivity of the Pacinian system—increases with spatial period for all but the coarsest surfaces. By varying the scanning velocity, we manipulate the temporal and intensive characteristics of the texture-induced vibrations and assess the effect of the manipulation on perceived roughness. We find that doubling the scanning velocity does not result in the substantial decrease in roughness predicted by a frequency theory of vibrotactile roughness perception. On the other hand, the effects of speed on roughness match those of speed on power. We propose that the roughness of a fine surface (spatial period<200 ?m) is a function of the Pacinian-weighted power of the vibrations it elicits. PMID:12745443

Bensmaïa, Sliman J.; Hollins, Mark

2007-01-01

303

Vibrational anharmonicity and multilevel vibrational dephasing from vibrational echo beats  

E-print Network

Vibrational anharmonicity and multilevel vibrational dephasing from vibrational echo beats K. D 94305 Received 22 January 1997; accepted 21 March 1997 Vibrational echo experiments were performed the vibrational anharmonicities, leading to the excitation and dephasing of a multilevel coherence. From the beat

Fayer, Michael D.

304

On the analytic representation of the correlation function of linear random vibration systems  

E-print Network

characteristics of the response of discrete vibration systems with a random external excitation. The excitation generator shafts excited by random fluctuations of the generator torque) results in a system of ordinary irregularities at multiple points of the vehicle suspension (spring and damper combinations). This can be done

305

A Canonical Response in Rainfall Characteristics to Global Warming: Projections by IPCC CMIP5 Models  

NASA Technical Reports Server (NTRS)

Changes in rainfall characteristics induced by global warming are examined based on probability distribution function (PDF) analysis, from outputs of 14 IPCC (Intergovernmental Panel on Climate Change), CMIP (5th Coupled Model Intercomparison Project) models under various scenarios of increased CO2 emissions. Results show that collectively CMIP5 models project a robust and consistent global and regional rainfall response to CO2 warming. Globally, the models show a 1-3% increase in rainfall per degree rise in temperature, with a canonical response featuring large increase (100-250 %) in frequency of occurrence of very heavy rain, a reduction (5-10%) of moderate rain, and an increase (10-15%) of light rain events. Regionally, even though details vary among models, a majority of the models (>10 out of 14) project a consistent large scale response with more heavy rain events in climatologically wet regions, most pronounced in the Pacific ITCZ and the Asian monsoon. Moderate rain events are found to decrease over extensive regions of the subtropical and extratropical oceans, but increases over the extratropical land regions, and the Southern Oceans. The spatial distribution of light rain resembles that of moderate rain, but mostly with opposite polarity. The majority of the models also show increase in the number of dry events (absence or only trace amount of rain) over subtropical and tropical land regions in both hemispheres. These results suggest that rainfall characteristics are changing and that increased extreme rainfall events and droughts occurrences are connected, as a consequent of a global adjustment of the large scale circulation to global warming.

Lau, William K. M.; Wu, H. T.; Kim, K. M.

2012-01-01

306

Prediction of linear cationic antimicrobial peptides based on characteristics responsible for their interaction with the membranes.  

PubMed

Most available antimicrobial peptides (AMP) prediction methods use common approach for different classes of AMP. Contrary to available approaches, we suggest that a strategy of prediction should be based on the fact that there are several kinds of AMP that vary in mechanisms of action, structure, mode of interaction with membrane, etc. According to our suggestion for each kind of AMP, a particular approach has to be developed in order to get high efficacy. Consequently, in this paper, a particular but the biggest class of AMP, linear cationic antimicrobial peptides (LCAP), has been considered and a newly developed simple method of LCAP prediction described. The aim of this study is the development of a simple method of discrimination of AMP from non-AMP, the efficiency of which will be determined by efficiencies of selected descriptors only and comparison the results of the discrimination procedure with the results obtained by more complicated discriminative methods. As descriptors the physicochemical characteristics responsible for capability of the peptide to interact with an anionic membrane were considered. The following characteristics such as hydrophobicity, amphiphaticity, location of the peptide in relation to membrane, charge density, propensities to disordered structure and aggregation were studied. On the basis of these characteristics, a new simple algorithm of prediction is developed and evaluation of efficacies of the characteristics as descriptors performed. The results show that three descriptors, hydrophobic moment, charge density and location of the peptide along the membranes, can be used as discriminators of LCAPs. For the training set, our method gives the same level of accuracy as more complicated machine learning approaches offered as CAMP database service tools. For the test set accuracy obtained by our method gives even higher value than the one obtained by CAMP prediction tools. The AMP prediction tool based on the considered method is available at http://www.biomedicine.org.ge/dbaasp/. PMID:24730612

Vishnepolsky, Boris; Pirtskhalava, Malak

2014-05-27

307

Influence of vibration resistance training on knee extensor and plantar flexor size, strength, and contractile speed characteristics after 60 days of bed rest  

Microsoft Academic Search

Spaceflight and bed rest (BR) result in loss of muscle mass and strength. This study evaluated the effectiveness of resistance training and vibration-augmented resistance training to preserve thigh (quadriceps femoris) and calf (triceps surae) muscle cross-sectional area (CSA), isometric maximal voluntary contraction (MVC), isometric contractile speed, and neural activation (electromyogram) during 60 days of BR. Male subjects participating in the

E. R. Mulder; A. M. Horstman; D. F. Stegeman; A. de Haan; D. L. Belavy; T. Miokovic; G. Armbrecht; D. Felsenberg; K. H. Gerrits

2009-01-01

308

Consideration of nonlinear vibration characteristic of object for irradiating highintensity ultrasonic waves by a point-convergence-type aerial ultrasonic source  

NASA Astrophysics Data System (ADS)

We considered a noncontact method that can detect internal defects in materials by analyzing frequency information obtained from the vibration of an object excited with highintensity ultrasonic waves. From our result, it is found that this method is able to detect internal defects in materials.

Osumi, Ayumu; Ito, Youichi

2012-09-01

309

Fiber optic vibration sensor  

DOEpatents

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity.

Dooley, Joseph B. (Harriman, TN); Muhs, Jeffrey D. (Lenoir City, TN); Tobin, Kenneth W. (Harriman, TN)

1995-01-01

310

Fiber optic vibration sensor  

DOEpatents

A fiber optic vibration sensor utilizes two single mode optical fibers supported by a housing with one optical fiber fixedly secured to the housing and providing a reference signal and the other optical fiber having a free span length subject to vibrational displacement thereof with respect to the housing and the first optical fiber for providing a signal indicative of a measurement of any perturbation of the sensor. Damping or tailoring of the sensor to be responsive to selected levels of perturbation is provided by altering the diameter of optical fibers or by immersing at least a portion of the free span length of the vibration sensing optical fiber into a liquid of a selected viscosity. 2 figures.

Dooley, J.B.; Muhs, J.D.; Tobin, K.W.

1995-01-10

311

The Effects of Impact Vibration on Peripheral Blood Vessels and Nerves  

PubMed Central

Research regarding the risk of developing hand-arm vibration syndrome after exposure to impact vibration has produced conflicting results. This study used an established animal model of vibration-induced dysfunction to determine how exposure to impact vibration affects peripheral blood vessels and nerves. The tails of male rats were exposed to a single bout of impact vibration (15 min exposure, at a dominant frequency of 30?Hz and an unweighted acceleration of approximately 345 m/s2) generated by a riveting hammer. Responsiveness of the ventral tail artery to adrenoreceptor-mediated vasoconstriction and acetylcholine-mediated re-dilation was measured ex vivo. Ventral tail nerves and nerve endings in the skin were assessed using morphological and immunohistochemical techniques. Impact vibration did not alter vascular responsiveness to any factors or affect trunk nerves. However, 4 days following exposure there was an increase in protein-gene product (PGP) 9.5 staining around hair follicles. A single exposure to impact vibration, with the exposure characteristics described above, affects peripheral nerves but not blood vessels. PMID:24077447

KRAJNAK, Kristine M.; WAUGH, Stacey; JOHNSON, Claud; MILLER, G. Roger; XU, Xueyan; WARREN, Christopher; DONG, Ren G.

2013-01-01

312

Vibration analysis to improve reliability and reduce failure; Proceedings of the Design Automation Conference, Cincinnati, OH, September 10-13, 1985  

SciTech Connect

Among the topics discussed are: turbomachinery tip rubs and interactive casting resonances; the transverse vibrational characteristics of an externally damaged pipe and performance of vibration monitoring for the prevention of gas turbine airfoil failures. Consideration is also given to: velocity response analysis of a spherical roller bearing; vibration monitoring of large pumps via a remote satellite stations; dynamic edge strain prediction in stiffened honeycomb panels; and fault-diagnosis for turbo-machines by means of vibration monitoring. Additional topics discussed include: early detection and diagnosis of faults rolling element bearings; spectral analysis of damped vibration by means of a modified version of the Prony method and guidelines for forced vibration in machine tools for use in protective maintenance and analysis.

Niskode, P.M.; Doepker, P.E.

1985-01-01

313

Thermodynamic characteristics and responses to ENSO of dominant intraseasonal modes in the East Asian summer monsoon  

NASA Astrophysics Data System (ADS)

The moisture supply and El Niño Southern Oscillation (ENSO) characteristics are investigated for different intraseasonal modes of the East Asian summer monsoon (EASM) identified as the Meiyu-Baiu, Changma, post-Changma, and dry-spell modes. The investigation is conducted with a type of artificial neural network known as self-organizing map analysis. The major modes tend to be dominated by the moisture convergence of the moisture budget equation along the rain-band. The Meiyu-Baiu mode is strongly linked to both the anomalous low-level convergence and vertical wind shear, which is related to baroclinic instability with warm air rising and cold air sinking. The Changma mode has a strengthened tropic-subtropics connection along the western north Pacific subtropical high, which induces vertical destabilization and strong convective instability by the low-level warm advection of moisture-laden air and upper-level cold advection of dry air. In late summer, the post-Changma and dry-spell modes are characterized by anomalous southeasterly flow of warm and moist air from western north Pacific monsoon, and low-level easterly flow, respectively. In response to the preceding El Niño, the Meiyu-Baiu and Changma modes occur more frequently, while the post-Changma and dry-spell modes show the opposite. The response to the La Niña exhibits a relatively weak connection, indicating asymmetric response on the preceding ENSO. This prominent difference in response to the ENSO leads to different behaviors of the Indian Ocean and western Pacific thermal state, and consequently, the distinct moisture supply and instability variations for the EASM intraseasonal modes.

Oh, Hyoeun; Ha, Kyung-Ja

2014-08-01

314

CHARADE: A characteristic code for calculating rate-dependent shock-wave response  

SciTech Connect

In this report we apply spatially one-dimensional methods and simple shock-tracking techniques to the solution of rate-dependent material response under flat-plate-impact conditions. This method of solution eliminates potential confusion of material dissipation with artificial dissipative effects inherent in finite-difference codes, and thus lends itself to accurate calculation of elastic-plastic deformation, shock-to-detonation transition in solid explosives, and shock-induced structural phase transformation. Equations are presented for rate-dependent thermoelastic-plastic deformation for (100) planar shock-wave propagation in materials of cubic symmetry (or higher). Specific numerical calculations are presented for polycrystalline copper using the mechanical threshold stress model of Follansbee and Kocks with transition to dislocation drag. A listing of the CHARADE (for characteristic rate dependence) code and sample input deck are given. 26 refs., 11 figs.

Johnson, J.N.; Tonks, D.L.

1991-01-01

315

The sense of flutter-vibration evoked by stimulation of the hairy skin of primates: Comparison of human sensory capacity with the responses of mechanoreceptive afferents innervating the hairy skin of monkeys  

Microsoft Academic Search

We have studied the response properties of peripheral myelinated fibers ending in the hairy skin of the Rhesus monkey, activated by sinusoidal mechanical stimulation. In parallel experiments we measured thresholds of the sensations evoked in man by identical stimuli, delivered under similar conditions to corresponding areas of the hairy skin. We found that the sense of low frequency vibration (i.

Michael M. Merzenich; Thomas Harrington

1969-01-01

316

Frequency characteristic of response of surface air pressure to changes in flux of cosmic rays  

NASA Astrophysics Data System (ADS)

We compare the series of daily-average values of the surface air pressure for De Bilt and Lugano meteorological stations with subtracted linear trends and seasonal harmonics, as well as the series of the flux of galactic cosmic rays (GCRs) at Jungfraujoch station with subtracted moving average over 200 days. Using the method of superposed epochs, we show that the Forbush decreases at both stations are accompanied by increased pressure. Spectral analysis allows us to conclude that the analyzed series are characterized by nonzero coherence in almost the entire frequency range: from 0.02 day-1 day up to the Nyquist frequency of 0.5 day-1. Using changes in the GCR flux as a probing signal, we obtain amplitude-frequency characteristics of the pressure reaction. For both stations, these characteristics are in qualitative agreement with each other and indicate that the atmospheric response can be described by a second-order linear dynamic system that has wide resonance with a maximum at a frequency of 0.15 day-1.

Bogdanov, M. B.

2014-11-01

317

Influence of surface defects in ZnO thin films on its biosensing response characteristic  

SciTech Connect

Highly c-axis oriented zinc oxide (ZnO) thin films deposited by rf magnetron sputtering under varying processing pressure (20-50 mT) in a reactive gas mixture of argon and oxygen were studied for biosensing application. The as-deposited ZnO thin films were in a state of compressive stress having defects related to interstitial Zn and antisite oxygen. Glucose oxidase has been chosen as the model enzyme in the present study and was immobilized on the surface of ZnO thin films deposited on indium tin oxide coated Corning Glass substrate. The studies reveal a correlation between the biosensing characteristic and the presence of defects in the ZnO films. The ZnO films deposited under high pressure (50 mT) are found to be more sensitive for biosensing application due to availability of more surface area for effective immobilization of biomolecules and exhibits a suitable microenvironment with good electron transfer characteristic. The obtained results highlight the importance of desired microstate besides availability of suitable native defects in the ZnO thin film for exhibiting enhanced biosensing response.

Saha, Shibu; Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)

2011-09-15

318

Apparatus and method of preloading vibration-damping bellows  

DOEpatents

An improved vibration damping bellows mount or interconnection is disclosed. In one aspect, the bellows is compressively prestressed along its length to offset vacuum-generated tensile loads and thereby improve vibration damping characteristics.

Cutburth, Ronald W. (Tracy, CA)

1988-01-01

319

Microparticle Response to Two-Dimensional Streaming Flows in Rectangular Chambers Undergoing Low-Frequency Horizontal Vibrations  

NASA Astrophysics Data System (ADS)

Manipulation of submicron-sized particles using second-order acoustic radiation forces at ultrasonic frequencies is hindered by the time-independent streaming flows. A similar phenomenon occurs when open fluid volumes are vibrated at low frequencies in the range of 100 Hz. The streaming phenomenon, in this lower-frequency range, is studied here by using horizontally actuated liquid-filled rectangular chambers. The formation of capillary waves at the liquid-air interface generates spatially varying flow fields in the bulk fluid, which can be used to collect particles at stable locations. However, the same spatial variation is the source of the streaming fields, which, under some conditions, can drag particles away from these stable locations. The governing equations for the second-order flow are derived and simulated, after which a particle-tracing algorithm is executed in the obtained flow field. Critical particle parameters are determined in multiple simulated chambers of different dimensions, with the aim of reducing the effect of the streaming field on the particle's movement. The simulation results are then applied experimentally to demonstrate the ability of this system to collect particles as small as 50 nm in diameter.

Agrawal, Prashant; Gandhi, Prasanna S.; Neild, Adrian

2014-12-01

320

Boundary spanning by nurse managers: effects of managers' characteristics and scope of responsibility on teamwork.  

PubMed

Increasing role complexity has intensified the work of managers in supporting healthcare teams. This study examined the influence of front-line managers' characteristics and scope of responsibility on teamwork. Scope of responsibility considers the breadth of the manager's role. A descriptive, correlational design was used to collect cross-sectional survey and administrative data in four acute care hospitals. A convenience sample of 754 staff completed the Relational Coordination Scale as a measure of teamwork that focuses on the quality of communication and relationships. Nurses (73.9%), allied health professionals (14.7%) and unregulated staff (11.7%) worked in 54 clinical areas, clustered under 30 front-line managers. Data were analyzed using hierarchical linear modelling. Leadership practices, clinical support roles and compressed operational hours had positive effects on teamwork. Numbers of non-direct report staff and areas assigned had negative effects on teamwork. Teamwork did not vary by span, managerial experience, worked hours, occupational diversity or proportion of full-time employees. Large, acute care teaching hospitals can enable managers to foster teamwork by enhancing managers' leadership practices, redesigning the flow or reporting structure for non-direct reports, optimizing managerial hours relative to operational hours, allocating clinical support roles, reducing number of areas assigned and, potentially, introducing co-manager models. PMID:25073056

Meyer, Raquel M; O'Brien-Pallas, Linda; Doran, Diane; Streiner, David; Ferguson-Paré, Mary; Duffield, Christine

2014-06-01

321

Dynamic characteristics of otolith ocular response during counter rotation about dual yaw axes in mice.  

PubMed

The central vestibular system plays an important role in higher neural functions such as self-motion perception and spatial orientation. Its ability to store head angular velocity is called velocity storage mechanism (VSM), which has been thoroughly investigated across a wide range of species. However, little is known about the mouse VSM, because the mouse lacks typical ocular responses such as optokinetic after nystagmus or a dominant time constant of vestibulo-ocular reflex for which the VSM is critical. Experiments were conducted to examine the otolith-driven eye movements related to the VSM and verify its characteristics in mice. We used a novel approach to generate a similar rotating vector as a traditional off-vertical axis rotation (OVAR) but with a larger resultant gravito-inertial force (>1g) by using counter rotation centrifugation. Similar to results previously described in other animals during OVAR, two components of eye movements were induced, i.e. a sinusoidal modulatory eye movement (modulation component) on which a unidirectional nystagmus (bias component) was superimposed. Each response is considered to derive from different mechanisms; modulations arise predominantly through linear vestibulo-ocular reflex, whereas for the bias, the VSM is responsible. Data indicate that the mouse also has a well-developed vestibular system through otoliths inputs, showing its highly conserved nature across mammalian species. On the other hand, to reach a plateau state of bias, a higher frequency rotation or a larger gravito-inertial force was considered to be necessary than other larger animals. Compared with modulation, the bias had a more variable profile, suggesting an inherent complexity of higher-order neural processes in the brain. Our data provide the basis for further study of the central vestibular system in mice, however, the underlying individual variability should be taken into consideration. PMID:25446357

Shimizu, N; Wood, S; Kushiro, K; Yanai, S; Perachio, A; Makishima, T

2015-01-29

322

Study on Development of the Seated Human Body System Exposed to Vehicular Ride Vibration Environment  

Microsoft Academic Search

\\u000a This paper tries to find an appropriate structure of human model, which can better represent the characteristics of the real\\u000a human body, using the apparent mass (APMS) and head transmissibility (STHT) in vertical vibrations. The model parameters were\\u000a identified through minimizing an error function comprising the measured and model response in terms of magnitude and phase\\u000a characteristics of APMS and

S. Rodean; M. Arghir

323

Chaos via torus breakdown in the vibration response of a rigid rotor supported by active magnetic bearings  

Microsoft Academic Search

This work reports on a numerical study undertaken to investigate the response of an imbalanced rigid rotor supported by active magnetic bearings. The mathematical model of the rotor-bearing system used in this study incorporates nonlinearity arising from the electromagnetic force—coil current—air gap relationship, and the effects of geometrical cross-coupling. The response of the rotor is observed to exhibit a rich

Jawaid I. Inayat-Hussain

2007-01-01

324

Variational study on the vibrational level structure and vibrational level mixing of highly vibrationally excited S? D?CO.  

PubMed

We perform converged high precision variational calculations to determine the frequencies of a large number of vibrational levels in S(0) D(2)CO, extending from low to very high excess vibrational energies. For the calculations we use our specific vibrational method (recently employed for studies on H(2)CO), consisting of a combination of a search/selection algorithm and a Lanczos iteration procedure. Using the same method we perform large scale converged calculations on the vibrational level spectral structure and fragmentation at selected highly excited overtone states, up to excess vibrational energies of ?17,000 cm(-1), in order to study the characteristics of intramolecular vibrational redistribution (IVR), vibrational level density and mode selectivity. PMID:22750345

Rashev, Svetoslav; Moule, David C; Rashev, Vladimir

2012-11-01

325

The Power Generation Characteristics and Durability of a Vibration Power Generation Device using Piezoelectric Thick Film Formed Directly by Screen Printing on a Stainless Steel Substrate  

NASA Astrophysics Data System (ADS)

This paper presents a small, high-performance and novel device that generates power from vibrations, made using screen-printing to form a piezoelectric thick film directly on a stainless steel substrate. This simple and cheap method realizes a 20 – 40 ?m-thick piezoelectric film, otherwise difficult to achieve using thin-film techniques or ceramic sintering, on a stainless steel substrate. A maximum output power of 1.1 mW was recorded with acceleration of 0.1 G0p (0.98 ms?2) applied at a resonance frequency of 24 Hz. We also evaluated the durability of the device by repeatedly striking the tip of the element. Output power exceeding 100 mW under damped resonant vibration was generated at the instant of striking, with approximately 0.9 mJ of power measured per single damped vibration. No deterioration was seen in the integrity of the stainless steel substrate or the piezoelectric thick film after over 10 million strikes.

Oishi, A.; Okumura, H.; Katsumura, H.; Kagata, H.

2014-11-01

326

Chaotic vortex induced vibrations  

NASA Astrophysics Data System (ADS)

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

Zhao, J.; Leontini, J. S.; Lo Jacono, D.; Sheridan, J.

2014-12-01

327

Optimization of a hybrid vibration absorber for vibration control of structures under random force excitation  

NASA Astrophysics Data System (ADS)

A recently reported design of a hybrid vibration absorber (HVA) which is optimized to suppress resonant vibration of a single degree-of-freedom (SDOF) system is re-optimized for suppressing wide frequency band vibration of the SDOF system under stationary random force excitation. The proposed HVA makes use of the feedback signals from the displacement and velocity of the absorber mass for minimizing the vibration response of the dynamic structure based on the H2 optimization criterion. The objective of the optimal design is to minimize the mean square vibration amplitude of a dynamic structure under a wideband excitation, i.e., the total area under the vibration response spectrum is minimized in this criterion. One of the inherent limitations of the traditional passive vibration absorber is that its vibration suppression is low if the mass ratio between the absorber mass and the mass of the primary structure is low. The active element of the proposed HVA helps further reduce the vibration of the controlled structure and it can provide significant vibration absorption performance even at a low mass ratio. Both the passive and active elements are optimized together for the minimization of the mean square vibration amplitude of the primary system. The proposed HVA are tested on a SDOF system and continuous vibrating structures with comparisons to the traditional passive vibration absorber.

Cheung, Y. L.; Wong, W. O.; Cheng, L.

2013-02-01

328

Effects of train noise and vibration on human heart rate during sleep: an experimental study  

PubMed Central

Objectives Transportation of goods on railways is increasing and the majority of the increased numbers of freight trains run during the night. Transportation noise has adverse effects on sleep structure, affects the heart rate (HR) during sleep and may be linked to cardiovascular disease. Freight trains also generate vibration and little is known regarding the impact of vibration on human sleep. A laboratory study was conducted to examine how a realistic nocturnal railway traffic scenario influences HR during sleep. Design Case–control. Setting Healthy participants. Participants 24 healthy volunteers (11 men, 13 women, 19–28?years) spent six consecutive nights in the sleep laboratory. Interventions All participants slept during one habituation night, one control and four experimental nights in which train noise and vibration were reproduced. In the experimental nights, 20 or 36 trains with low-vibration or high-vibration characteristics were presented. Primary and secondary outcome measures Polysomnographical data and ECG were recorded. Results The train exposure led to a significant change of HR within 1?min of exposure onset (p=0.002), characterised by an initial and a delayed increase of HR. The high-vibration condition provoked an average increase of at least 3?bpm per train in 79% of the participants. Cardiac responses were in general higher in the high-vibration condition than in the low-vibration condition (p=0.006). No significant effect of noise sensitivity and gender was revealed, although there was a tendency for men to exhibit stronger HR acceleration than women. Conclusions Freight trains provoke HR accelerations during sleep, and the vibration characteristics of the trains are of special importance. In the long term, this may affect cardiovascular functioning of persons living close to railways. PMID:23793667

Croy, Ilona; Smith, Michael G; Waye, Kerstin Persson

2013-01-01

329

Helicopter rotor blade design for minimum vibration  

NASA Technical Reports Server (NTRS)

The importance of blade design parameters in rotor vibratory response and the design of a minimum vibration blade based upon this understanding are examined. Various design approaches are examined for a 4 bladed articulated rotor operating at a high speed flight condition. Blade modal shaping, frequency placement, structural and aerodynamic coupling, and intermodal cancellation are investigated to systematically identify and evaluate blade design parameters that influence blade airloads, blade modal response, hub loads, and fuselage vibration. The relative contributions of the various components of blade force excitation and response to the vibratory hub loads transmitted to the fuselage are determined in order to isolate primary candidates for vibration alleviation. A blade design is achieved which reduces the predicted fuselage vibration from the baseline blade by approximately one half. Blade designs are developed that offer significant reductions in vibration (and fatigue stresses) without resorting to special vibration alleviation devices, radical blade geometries, or weight penalties.

Taylor, R. B.

1984-01-01

330

A forced response analysis and application of impact dampers to rotordynamic vibration suppression in a cryogenic environment  

E-print Network

MANUAL FOR FORCED RESPONSE SIMULATION CODE . . 187 E FORCED RESPONSE NUMERICAL RESULTS F CRYOGENIC BALL BEARING ANALYSIS 207 G 2-X LARGE GAP, 6 IMPACTOR AMPLITUDE STUDY RESULTS . . 217 H 2-X LARGE GAP, 3 IMPACTOR AMPLITUDE STUDY RESULTS . . 224 I 3-Y... to be evaluated using initial conditions at the time of impact. 18 For the case of free decay (F. = 0), Eq. (2. 3) reduces to: x(t) = e ' x, cos(~~(t-s+) + ' " ' sin(v~(t-tQ (2. 4) 4 This expression was utilized in the numerical simulation for free decay...

Moore, James Jeffrey

2012-06-07

331

Food vibrations: Asian spice sets lips trembling  

PubMed Central

Szechuan pepper, a widely used ingredient in the cuisine of many Asian countries, is known for the tingling sensation it induces on the tongue and lips. While the molecular mechanism by which Szechuan pepper activates tactile afferent fibres has been clarified, the tingling sensation itself has been less studied, and it remains unclear which fibres are responsible. We investigated the somatosensory perception of tingling in humans to identify the characteristic temporal frequency and compare this to the established selectivity of tactile afferents. Szechuan pepper was applied to the lower lip of participants. Participants judged the frequency of the tingling sensation on the lips by comparing this with the frequencies of mechanical vibrations applied to their right index finger. The perceived frequency of the tingling was consistently at around 50 Hz, corresponding to the range of tactile RA1 afferent fibres. Furthermore, adaptation of the RA1 channel by prolonged mechanical vibration reliably reduced the tingling frequency induced by Szechuan pepper, confirming that the frequency-specific tactile channel is shared between Szechuan pepper and mechanical vibration. Combining information about molecular reactions at peripheral receptors with quantitative psychophysical measurement may provide a unique method for characterizing unusual experiences by decomposing them into identifiable minimal units of sensation. PMID:24026819

Hagura, Nobuhiro; Barber, Harry; Haggard, Patrick

2013-01-01

332

EVALUATION ON THE SEISMIC RESPONSE CHARACTERISTICS OF A ROAD EMBANKMENT BASED ON THE MODERATE EARTHQUAKE OBSERVATION AND THE MICROTREMOR MEASUREMENT  

NASA Astrophysics Data System (ADS)

Accurate evaluation on the seismic response characteristics of a road embankment is very important for the rational seismic assessment. However, in a lot of previous studies, the seismic response characteristics of an embankment were evaluated based on the results of shaking table test, centrifuge model test and dynamic FEM analysis. In this study, the transfer function and the shear wave velocity of a road embankment were evaluated based on the in-situ records of moderate earthquake observation and microtremor measurement. Test results show the possibility that the shear wave velocity of an embankment can be estimated by the earthquake observation or the microtremor measurement and the dynamic linear FEM analysis.

Hata, Yoshiya; Ichii, Koji; Yamada, Masayuki; Tokida, Ken-Ichi; Takezawa, Koichiro; Shibao, Susumu; Mitsushita, Junji; Murata, Akira; Furukawa, Aiko; Koizumi, Keigo

333

Influence of In doping on the structural, photo-luminescence and alcohol response characteristics of the SnO{sub 2} nanoparticles  

SciTech Connect

Graphical abstract: When the sample is exposed to air, the atmospheric oxygen O{sub 2} adsorbs on the sample surface in the form of ionic species O{sup ?} by capturing electrons from the conduction band. The adsorbed ionic species O{sup ?} react with the test alcohol molecules and are responsible for sensing mechanism. - Highlights: • In-doped SnO{sub 2} samples show smaller crystallinity with crystallite size: ?7–9 nm. • EDX analyses confirm the incorporation of indium ions in the SnO{sub 2} lattice. • Raman spectra are consistent with the results of XRD and SAED pattern. • Alcohol response has been found to increase with the indium dopant concentration. • 3 at% In-doped sample exhibits maximum response (96.5%) to propan-2-ol at 250 °C. - Abstract: Undoped and In-doped SnO{sub 2} nanoparticles were synthesized by the co-precipitation method. Upon In doping, the samples exhibit reduced crystallinity as compared to the undoped SnO{sub 2}. The Raman spectra of the undoped samples exhibit three fundamental peaks at 467.3, 633.4 and 774.6 cm{sup ?1} corresponding to E{sub g}, A{sub 1g} and B{sub 2g} vibration modes, respectively. The PL spectra show two strong emission bands at the wavelengths 417 nm and 479 nm, along with five weak emission peaks in the visible region. Alcohol response characteristics of the In-doped SnO{sub 2} samples were investigated for various concentrations (10–50 ppm) at different operating temperatures (150–250 °C). Among all the samples examined, the 3 at% In-doped SnO{sub 2} sample shows maximum response (96.5%) to propan-2-ol, followed by ethanol (92%) and methanol (90%) at the operating temperature of 250 °C for 50 ppm concentration. For each test alcohol, the response has been found to increase with the In dopant concentration.

Mishra, R.K. [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Pandey, Shiv K. [Department of Chemistry, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Nanotechnology Application Center, Science Faculty, University of Allahabad, Allahabad (India); Sahay, P.P., E-mail: dr_ppsahay@rediffmail.com [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad 211004 (India)

2013-10-15

334

Characteristics of the response of the iliac artery to wall shear stress in the anaesthetized pig  

PubMed Central

The functional significance of shear stress-induced vasodilatation in large conduit arteries is unclear since changes in the diameter have little effect on the resistance to blood flow. However, changes in diameter have a relatively large effect on wall shear stress which suggests that the function of flow-mediated dilatation is to reduce wall shear stress. The mean and pulsatile components of shear stress vary widely throughout the arterial system and areas of low mean and high amplitude of wall shear stress are prone to the development of atheroma. In this study, using an in vivo model with the ability to control flow rate and amplitude of flow independently, we investigated the characteristics of the response of the iliac artery to variations in both the mean and amplitude of wall shear stress. The results of this study confirm that increases in mean wall shear stress are an important stimulus for the release of nitric oxide by the endothelium as indicated by changes in arterial diameter and show for the first time, in vivo, that increases in the amplitude of the pulsatile component of shear stress have a small but significant inhibitory effect on this response. A negative feedback mechanism was identified whereby increases in shear stress brought about by increases in blood flow are reduced by the release of nitric oxide from the endothelium causing dilatation of the artery, thus decreasing the stimulus to cell adhesion and, through a direct action of nitric oxide, inhibiting the process of cell adhesion. The results also provide an explanation for the uneven distribution of atheroma throughout the arterial system, which is related to the ratio of pulsatile to mean shear stress and consequent variability in the production of NO. PMID:17412772

Kelly, R F; Snow, H M

2007-01-01

335

Experimental Studies on Dynamic Vibration Absorber using Shape Memory Alloy (NiTi) Springs  

NASA Astrophysics Data System (ADS)

Shape memory alloy (SMA) springs have been used as actuators in many applications although their use in the vibration control area is very recent. Since shape memory alloys differ from conventional alloy materials in many ways, the traditional design approach for springs is not completely suitable for designing SMA springs. Some vibration control concepts utilizing unique characteristics of SMA's will be presented in this paper. A dynamic vibration absorber (DVA) using shape memory alloy (SMA) actuator is developed for attenuation of vibration in a cantilever beam. The design procedure of the DVA is presented. The system consists of a cantilever beam which is considered to generate the real-time vibration using shaker. A SMA spring is used with a mass attached to its end. The stiffness of the SMA spring is dynamically varied in such a way to attenuate the vibration. Both simulation and experimentation are carried out using PID controller. The experiments were carried out by interfacing the experimental setup with a computer using LabVIEW software, Data acquisition and control are implemented using a PCI data acquisition card. Standard PID controllers have been used to control the vibration of the beam. Experimental results are used to demonstrate the effectiveness of the controllers designed and the usefulness of the proposed test platform by exciting the structure at resonance. In experimental setup, an accelerometer is used to measure the vibration which is fed to computer and correspondingly the SMA spring is actuated to change its stiffness to control the vibration. The results obtained illustrate that the developed DVA using SMA actuator is very effective in reducing structural response and have great potential to be an active vibration control medium.

Kumar, V. Raj; Kumar, M. B. Bharathi Raj; Kumar, M. Senthil

2011-10-01

336

Experimental Studies on Dynamic Vibration Absorber using Shape Memory Alloy (NiTi) Springs  

SciTech Connect

Shape memory alloy (SMA) springs have been used as actuators in many applications although their use in the vibration control area is very recent. Since shape memory alloys differ from conventional alloy materials in many ways, the traditional design approach for springs is not completely suitable for designing SMA springs. Some vibration control concepts utilizing unique characteristics of SMA's will be presented in this paper.A dynamic vibration absorber (DVA) using shape memory alloy (SMA) actuator is developed for attenuation of vibration in a cantilever beam. The design procedure of the DVA is presented. The system consists of a cantilever beam which is considered to generate the real-time vibration using shaker. A SMA spring is used with a mass attached to its end. The stiffness of the SMA spring is dynamically varied in such a way to attenuate the vibration. Both simulation and experimentation are carried out using PID controller. The experiments were carried out by interfacing the experimental setup with a computer using LabVIEW software, Data acquisition and control are implemented using a PCI data acquisition card. Standard PID controllers have been used to control the vibration of the beam. Experimental results are used to demonstrate the effectiveness of the controllers designed and the usefulness of the proposed test platform by exciting the structure at resonance. In experimental setup, an accelerometer is used to measure the vibration which is fed to computer and correspondingly the SMA spring is actuated to change its stiffness to control the vibration. The results obtained illustrate that the developed DVA using SMA actuator is very effective in reducing structural response and have great potential to be an active vibration control medium.

Kumar, V. Raj; Kumar, M. B. Bharathi Raj; Kumar, M. Senthil [Department of Mechanical Engineering, PSG College of Technology, Coimbatore (India)

2011-10-20

337

Flow patterns generated by vibrations in weightlessness in binary mixture with Soret effect.  

NASA Astrophysics Data System (ADS)

Vibrational convection refers to the specific flows that appear when a fluid with density gradient is subjected to external vibration. The density gradient may result from the inhomogeneity of temperature or composition. The study of vibrational impact on fluids has fundamental and applied importance. In weightlessness, vibrational convection is an additional way of transporting heat and matter similar to thermo- and solutocapillary convection. The response of the fluid to external forcing depends on the frequency of vibration. The case of small amplitude and high frequency vibration (when the period is much smaller than the characteristic viscous and heat (mass) diffusion times) is of special interest. In this case, the mean flow can be observed in the system, which describes the non-linear response of the fluid to a periodic excitation. The mean flow is most pronounced in the absence of other external forces (in particular, absence of static gravity). The experiment IVIDIL (Influence of Vibration on Diffusion in Liquids) has been conducted on the ISS during more than 3 months in 2009-2010. In the experimental liquids the density changes due to both the temperature and composition. 55 experimental runs of IVIDIL provided rich variety of valuable information about behavior of the liquid in weightlessness which is released with time, [1-3]. The current results provide experimental and numerical evidence of richness of flow patterns and their classification. References: 1. Shevtsova V., Mialdun A., Melnikov D., Ryzhkov I., Gaponenko Y., Saghir Z., Lyubimova T., Legros J.C., IVIDIL experiment onboard ISS: thermodiffusion in presence of controlled vibrations, Comptes Rendus Mecanique, 2011, 339, 310-317 2. Shevtsova V., Lyubimova T., Saghir Z. , Melnikov D., Gaponenko Y. , Sechenyh V. , Legros J.C. , Mialdun A., IVIDIL: on-board g-jitters and diffusion controlled phenomena; Journal of Physics: Conference Series, 2011, 327, 012031 3. Mazzoni S., Shevtsova V., Mialdun A., Melnikov D., Gaponenko Y., Lyubimova T., Saghir Z., Vibrating liquids in Space, Europhysics News, 2010, 41, 14.

Shevtsova, Valentina; Melnikov, Denis; Gaponenko, Yuri; Lyubimova, Tatyana; Mialdun, Aliaksandr; Sechenyh, Vitaliy

2012-07-01

338

Theoretical study of the distal-side steric and electrostatic effects on the vibrational characteristics of the FeCO unit of the carbonylheme proteins and their models.  

PubMed Central

The vibronic theory of activation and quantum chemical intermediate neglect of differential overlap (INDO) calculations are used to study the activation of carbon monoxide (change of the C-O bond index and force field constant) by the imidazole complex with heme in dependence on the distortion of the porphyrin ring, geometry of the CO coordination, iron-carbon and iron-imidazole distances, iron displacement out of the porphyrin plane, and presence of the charged groups in the heme environment. It is shown that the main contribution to the CO activation stems from the change in the sigma donation from the 5 sigma CO orbital to iron, and back-bonding from the iron to the 2 pi orbital of CO. It follows from the results that none of the studied distortions can explain, by itself, the wide variation of the C-O vibrational frequency in the experimentally studied model compounds and heme proteins. To study the dependence of the properties of the FeCO unit on the presence of charged groups in the heme environment, the latter are simulated by the homogeneous electric field and point charges of different magnitude and location. The results show that charged groups can strongly affect the strength of the C-O bond and its vibrational frequency. It is found that the charges located on the distal side of the heme plane can affect the Fe-C and C-O bond indexes (and, consequently, the Fe-C and C-O vibrational frequencies), both in the same and in opposite directions, depending on their position. The theoretical results allow us to understand the peculiarities of the effect of charged groups on the properties of the FeCO unit both in heme proteins and in their model compounds. Images FIGURE 2 PMID:8785279

Kushkuley, B; Stavrov, S S

1996-01-01

339

Dynamic and Thermodynamic Characteristics of Atmospheric Response to Anomalous Sea-Ice Extent in the Sea of Okhotsk  

Microsoft Academic Search

Influence of sea-ice extent anomalies within the Sea of Okhotsk on the large-scale atmospheric circulation is investigated through an analysis of the dynamic and thermodynamic characteristics of the response in an atmospheric general circulation model to specified anomalous sea-ice cover. Significant response appears not only around the Sea of Okhotsk, but also downstream over the Bering Sea, Alaska, and North

Meiji Honda; Koji Yamazaki; Hisashi Nakamura; Kensuke Takeuchi

1999-01-01

340

The derivation of species response curves with Gaussian logistic regression is sensitive to sampling intensity and curve characteristics  

Microsoft Academic Search

We investigated quantitatively the sensitivity of plant species response curves to sampling characteristics (number of plots, occurrence and frequency of species), along a simulated pH gradient. We defined 54 theoretical unimodal response curves, issued from combinations of six values for optimum (opt=3, 4, …, 8), three values for tolerance (tol=0.5, 1.0, and 1.5, sensu ter Braak and Looman [ter Braak,

Christophe Coudun; Jean-Claude Gégout

2006-01-01

341

Approximate inclusion of four-mode couplings in vibrational coupled-cluster theory.  

PubMed

The vibrational coupled cluster (VCC) equations are analyzed in terms of vibrational Mo?ller-Plesset perturbation theory aiming specifically at the importance of four-mode couplings. Based on this analysis, new VCC methods are derived for the calculation of anharmonic vibrational energies and vibrational spectra using vibrational coupled cluster response theory. It is shown how the effect of four-mode coupling and excitations can be efficiently and accurately described using approximations for their inclusion. Two closely related approaches are suggested. The computational scaling of the so-called VCC[3pt4F] method is not higher than the fifth power in the number of vibrational degrees of freedom when up to four-mode coupling terms are present in the Hamiltonian and only fourth order when only up to three-mode couplings are present. With a further approximation, one obtains the VCC[3pt4] model which is shown to scale with at most the fourth power in the number of vibrational degrees of freedom for Hamiltonians with both three- and four-mode coupling levels, while sharing the most important characteristics with VCC[3pt4F]. Sample calculations reported for selected tetra-atomic molecules as well as the larger dioxirane and ethylene oxide molecules support that the new models are accurate and useful. PMID:22667551

Zoccante, Alberto; Seidler, Peter; Hansen, Mikkel Bo; Christiansen, Ove

2012-05-28

342

Life-history traits and landscape characteristics predict macro-moth responses to forest fragmentation.  

PubMed

How best to manage forest patches, mitigate the consequences of forest fragmentation, and enable landscape permeability are key questions facing conservation scientists and managers. Many temperate forests have become increasingly fragmented, resulting in reduced interior forest habitat, increased edge habitats, and reduced connectivity. Using a citizen science landscape-scale mark-release-recapture study on 87 macro-moth species, we investigated how both life-history traits and landscape characteristics predicted macro-moth responses to forest fragmentation. Wingspan, wing shape, adult feeding, and larval feeding guild predicted macro-moth mobility, although the predictive power of wingspan and wing shape depended on the species' affinity to the forest. Solitary trees and small fragments functioned as "stepping stones," especially when their landscape connectivity was increased, by being positioned within hedgerows or within a favorable matrix. Mobile forest specialists were most affected by forest fragmentation: despite their high intrinsic dispersal capability, these species were confined mostly to the largest of the forest patches due to their strong affinity for the forest habitat, and were also heavily dependent on forest connectivity in order to cross the agricultural matrix. Forest fragments need to be larger than five hectares and to have interior forest more than 100 m from the edge in order to sustain populations of forest specialists. Our study provides new insights into the movement patterns of a functionally important insect group, with implications for the landscape-scale management of forest patches within agricultural landscapes. PMID:23951712

Slade, Eleanor M; Merckx, Thomas; Riutta, Terhi; Bebber, Daniel P; Redhead, David; Riordan, Philip; Macdonald, David W

2013-07-01

343

Estimates of auditory filter phase response at and below characteristic frequency (L)  

PubMed Central

Animal studies in basal cochlear regions have shown that basilar-membrane phase curvature (or rate of change of group delay with frequency) is negative around characteristic frequency (CF), but near zero well below CF. This study examined whether psychophysical masking experiments in humans show the same difference between on- and off-CF phase curvature. Masked thresholds were measured for a 2-kHz signal in the presence of harmonic tone complex maskers with a fundamental frequency of 100 Hz, band-limited between 200 and 1400 Hz (off-frequency masker) or between 1400 and 2600 Hz (on-frequency masker). The results from four normal-hearing listeners are consistent with predictions from animal physiological data: negative phase curvature is found for the on-frequency masker, whereas the phase curvature for the off-frequency masker is near zero. The method and results provide a strong test for the temporal response of computational models of human cochlear filtering. PMID:15898618

Oxenham, Andrew J.; Ewert, Stephan D.

2005-01-01

344

Vibrations transmitted to human subjects through passenger seats and considerations of passenger comfort  

NASA Technical Reports Server (NTRS)

An experimental study was conducted to determine the vertical and lateral vibration-transmission characteristics of several types of transport vehicle seats (two aircraft and one bus) to obtain preliminary estimates and comparisons of the ride acceptability of the various seat types. Results of this investigation indicate that from the standpoint of human comfort the seats exhibit undesirable dynamic response characteristics. Amplification of floor vibrations occurred at the frequencies known to be most critical for human comfort in both vertical and lateral axes. An average transmissibility function for aircraft seats was tabulated together with the associated variability for use by designers who incorporate similar types of seats in their vehicles. The acceptability of vibrations resulting from floor inputs of 0.10g and 0.15g was low over a broad range of frequencies for both axes and all seat types, and was especially low at frequencies where the input was being amplified.

Leatherwood, J. D.

1975-01-01

345

Electrical and acoustical resonances of vibrators  

NASA Technical Reports Server (NTRS)

The basic sources of vibration in electrical machines are identified as: (1) unbalanced masses of the rotor, (2) condition of the bearings, and (3) the electromagnetic field gap. Methods for improving the vibration characteristics of electrical machines are proposed. A mathematical model is developed for calculating the damping elements located between the bearings and the mounts.

Khvingiya, M. V.; Tatishvili, T. G.; Zilberg, A. G.

1973-01-01

346

Experimental investigation of the vibroacoustic response characteristics of rib-stiffened panels with simple and complex attachments  

Microsoft Academic Search

This work experimentally investigates the critical vibroacoustic response characteristics of a class of lightweight structures representative of those used in communications satellites. Parametric trends are identified and contrasted for the structures loaded with simple (non-resonant) mass attachments and for complex (resonant) equipment attachments. Unlike related previous works where the attachments' mass was typically on the order of ten percent of

Stephen Clarke Conlon

2003-01-01

347

Effects of the Resistivity and Crystal Orientation of the Silicon PIN Detector on the Dark Current and Radiation Response Characteristics  

Microsoft Academic Search

The effects of the resistivity and crystal orientation on the leakage current and radiation response characteristics have been studied. The detector with (111) oriented substrate shows higher leakage current than (100) orientation due to the higher interface trap density at the Si\\/SiO2 interface. And high resistive substrate shows larger leakage current than low resistive one because of its wider depletion

Kun-Sik Park; Jong-Moon Park; Yong-Sun Yoon; Jin-Gun Koo; Bo-Woo Kim; Chang-Joo Yoon; Kwang-Soo No

2006-01-01

348

Analysis on pseudo excitation of random vibration for structure of time flight counter  

NASA Astrophysics Data System (ADS)

Traditional computing method is inefficient for getting key dynamical parameters of complicated structure. Pseudo Excitation Method(PEM) is an effective method for calculation of random vibration. Due to complicated and coupling random vibration in rocket or shuttle launching, the new staging white noise mathematical model is deduced according to the practical launch environment. This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter(ToFC). The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level. Considering stiffness of fixture structure, the random vibration experiments are conducted in three directions to compare with the revised PEM. The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained. The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results. The maximum error is within 9%. The reasons of errors are analyzed to improve reliability of calculation. This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.

Wu, Qiong; Li, Dapeng

2014-12-01

349

Biocompatibility, Inflammatory Response, and Recannalization Characteristics of Nonradioactive Resin Microspheres: Histological Findings  

SciTech Connect

Intra-arterial radiotherapy with yttrium-90 microspheres (radioembolization) is a therapeutic procedure exclusively applied to the liver that allows the direct delivery of high-dose radiation to liver tumors, by means of endovascular catheters, selectively placed within the tumor vasculature. The aim of the study was to describe the distribution of spheres within the precapillaries, inflammatory response, and recannalization characteristics after embolization with nonradioactive resin microspheres in the kidney and liver. We performed a partial embolization of the liver and kidney vessels in nine white pigs. The left renal and left hepatic arteries were catheterized and filled with nonradioactive resin microspheres. Embolization was defined as the initiation of near-stasis of blood flow, rather than total occlusion of the vessels. The hepatic circulation was not isolated so that the effects of reflux of microspheres into stomach could be observed. Animals were sacrificed at 48 h, 4 weeks, and 8 weeks, and tissue samples from the kidney, liver, lung, and stomach evaluated. Microscopic evaluation revealed clusters of 10-30 microspheres (15-30 {mu}m in diameter) in the small vessels of the kidney (the arciform arteries, vasa recti, and glomerular afferent vessels) and liver. Aggregates were associated with focal ischemia and mild vascular wall damage. Occlusion of the small vessels was associated with a mild perivascular inflammatory reaction. After filling of the left hepatic artery with microspheres, there was some evidence of arteriovenous shunting into the lungs, and one case of cholecystitis and one case of marked gastritis and ulceration at the site of arterial occlusion due to the presence of clusters of microspheres. Beyond 48 h, microspheres were progressively integrated into the vascular wall by phagocytosis and the lumen recannalized. Eight-week evaluation found that the perivascular inflammatory reaction was mild. Liver cell damage, bile duct injury, and portal space fibrosis were not observed. In conclusion, resin microspheres (15-30 {mu}m diameter) trigger virtually no inflammatory response in target tissues (liver and kidney). Clusters rather than individual microspheres were associated with a mild to moderate perivascular inflammatory reaction. There was no evidence of either a prolonged inflammatory reaction or fibrosis in the liver parenchyma following recannalization.

Bilbao, Jose I., E-mail: Jibilbao@unav.e [Clinica Universitaria de Navarra, Universidad de Navarra, Department of Radiology (Spain); Martino, Alba de [Universidad de Zaragoza, Department of Histology, School of Veterinary (Spain); Luis, Esther de; Diaz-Dorronsoro, Lourdes; Alonso-Burgos, Alberto; Martinez de la Cuesta, Antonio [Clinica Universitaria de Navarra, Universidad de Navarra, Department of Radiology (Spain); Sangro, Bruno [Clinica Universitaria de Navarra, Universidad de Navarra, Department of Internal Medicine (Liver Unit) (Spain); Garcia de Jalon, Jose A. [Universidad de Zaragoza, Department of Histology, School of Veterinary (Spain)

2009-07-15

350

Effects of Rearing Systems on Performance, Egg Characteristics and Immune Response in Two Layer Hen Genotype  

PubMed Central

White (Lohmann LSL) and Brown (ATAK-S) laying hens, were reared under organic and conventional cage rearing systems, and the effects of the rearing system on performance parameters, egg production, egg characteristics, and immune response were investigated. For this purpose, a total of 832 laying hens of two commercial hybrids, i.e., 416 white (Lohmann LSL) and 416 Brown (ATAK-S) layers, were used. The experiment lasted between 23 and 70 wk of age. In this study, the white layers yielded more eggs as compared to the brown layers in both organic and conventional production systems. Egg weight exhibited a similar pattern to that of laying performance. However, the total hen-housed egg number for the white birds in the organic system was fewer than that of white birds in the conventional cage facility; conversely, a contradictory tendency was observed for the brown birds. Livability of the white layers in the organic system was remarkably lower (14%) than that of the brown line, whereas the white line survived better (3.42%) than their brown counterparts in conventional cages. The feed conversion ratio of the white hens was markedly inferior in the organic system as compared to that of the white hens in the conventional system, whereas relatively lower deterioration was reported in brown layers when reared in an organic system. The organic production system increased egg albumen height and the Haugh unit in eggs of the brown layers. The yolk color score of organic eggs was lower than that of conventional eggs for both brown and white hens. The egg yolk ratio of eggs from white layers was found to be higher in organic eggs as compared to those obtained in the conventional system. All organic eggs had heavier shells than those produced in the conventional system. Eggs from brown layers had more protein content than eggs from white layers. Neither housing systems nor genotype influenced egg yolk cholesterol concentration. When compared to conventional eggs, n-3 fatty acid content was lower in organic eggs, and the n-6:n-3 ratio was higher in organic eggs. In conclusion, two hen genotypes showed different responses in terms of performance and egg quality to two different rearing systems. A commercial white strain produced more eggs with higher egg quality as compared to a native brown strain. The brown strain was found to have adapted well to organic production conditions when survival and total egg number was taken into consideration. PMID:25049597

Küçüky?lmaz, Kamil; Bozkurt, Mehmet; Herken, Emine Nur; Ç?nar, Mustafa; Çatl?, Abdullah U?ur; Binta?, Erol; Çöven, Fethiye

2012-01-01

351

Influence of vibration resistance training on knee extensor and plantar flexor size, strength, and contractile speed characteristics after 60 days of bed rest.  

PubMed

Spaceflight and bed rest (BR) result in loss of muscle mass and strength. This study evaluated the effectiveness of resistance training and vibration-augmented resistance training to preserve thigh (quadriceps femoris) and calf (triceps surae) muscle cross-sectional area (CSA), isometric maximal voluntary contraction (MVC), isometric contractile speed, and neural activation (electromyogram) during 60 days of BR. Male subjects participating in the second Berlin Bed Rest Study underwent BR only [control (CTR), n = 9], BR with resistance training (RE; n = 7), or BR with vibration-augmented resistance training (RVE; n = 7). Training was performed three times per week. Thigh CSA and MVC torque decreased by 13.5 and 21.3%, respectively, for CTR (both P < 0.001), but were preserved for RE and RVE. Calf CSA declined for all groups, but more so (P < 0.001) for CTR (23.8%) than for RE (10.7%) and RVE (11.0%). Loss in calf MVC torque was greater (P < 0.05) for CTR (24.9%) than for RVE (12.3%), but not different from RE (14.8%). Neural activation at MVC remained unchanged in all groups. For indexes related to rate of torque development, countermeasure subjects were pooled into one resistance training group (RT, n = 14). Thigh maximal rate of torque development (MRTD) and contractile impulse remained unaltered for CTR, but MRTD decreased 16% for RT. Calf MRTD remained unaltered for both groups, whereas contractile impulse increased across groups (28.8%), despite suppression in peak electromyogram (12.1%). In conclusion, vibration exposure did not enhance the efficacy of resistance training to preserve thigh and calf neuromuscular function during BR, although sample size issues may have played a role. The exercise regimen maintained thigh size and MVC strength, but promoted a loss in contractile speed. Whereas contractile speed improved for the calf, the exercise regimen only partially preserved calf size and MVC strength. Modification of the exercise regimen seems warranted. PMID:19797694

Mulder, Edwin R; Horstman, Astrid M; Stegeman, Dick F; de Haan, Arnold; Belavý, Daniel L; Miokovic, Tanja; Armbrecht, Gabi; Felsenberg, Dieter; Gerrits, Karin H

2009-12-01

352

Vibration Responses of Test Structure No. 2 During the Edward Air Force Base Phase of the National Sonic Boom Program  

NASA Technical Reports Server (NTRS)

In order to evaluate reaction of people to sonic booms of varying overpressures and time durations, a series of closely controlled and systematic flight tests/studies were conducted from June 3 to June 23, 1966. The dynamic responses of several building structures were measured, with emphasis on a two-story residence structure. Sample acceleration and strain recordings from F-104, B-58, and XB-70 sonic boom exposures are included, along with tabulations of the maximum acceleration and strain values measured for each one of about 140 flight tests. These data are compared with similar measurements for engine noise exposures of the building during simulated landing approaches and takeoffs of KC-135 aircraft.

Findley, D. S.; Huckel, V.; Hubbard, H. H.

1975-01-01

353

An Inverse Method for Determining Source Characteristics for Emergency Response Applications  

NASA Astrophysics Data System (ADS)

Following a malicious or accidental atmospheric release in an outdoor environment it is essential for first responders to ensure safety by identifying areas where human life may be in danger. For this to happen quickly, reliable information is needed on the source strength and location, and the type of chemical agent released. We present here an inverse modelling technique that estimates the source strength and location of such a release, together with the uncertainty in those estimates, using a limited number of measurements of concentration from a network of chemical sensors considering a single, steady, ground-level source. The technique is evaluated using data from a set of dispersion experiments conducted in a meteorological wind tunnel, where simultaneous measurements of concentration time series were obtained in the plume from a ground-level point-source emission of a passive tracer. In particular, we analyze the response to the number of sensors deployed and their arrangement, and to sampling and model errors. We find that the inverse algorithm can generate acceptable estimates of the source characteristics with as few as four sensors, providing these are well-placed and that the sampling error is controlled. Configurations with at least three sensors in a profile across the plume were found to be superior to other arrangements examined. Analysis of the influence of sampling error due to the use of short averaging times showed that the uncertainty in the source estimates grew as the sampling time decreased. This demonstrated that averaging times greater than about 5min (full scale time) lead to acceptable accuracy.

Rudd, A. C.; Robins, A. G.; Lepley, J. J.; Belcher, S. E.

2012-07-01

354

Flow Analysis around the Suction Valve and the Vibration Characteristics of the Valve in a Compressor for Automotive Air-Conditioner  

NASA Astrophysics Data System (ADS)

The displacement of the suction valve in a compressor for automotive air-conditioning and the flow around the valve are investigated using a flow visualization technique. The visualization is conducted using the real compressor, which is improved to observe inside under the actual condition. Turbulent flow around the suction valve is solved using a computational fluid dynamics simulation. The flow is assumed to be an incompressible three-dimensional and viscous. The standard k-? turbulent model is used Furthermore the pressure pulsations, the flow velocity and the displacements of the suction valves are analyzed numerically using the system simulation program we developed. The calculated results using a computational fluid dynamics are compared with the flow visualization results and the vibrations of the valve are discussed.

Sato, Taizo; Tsukiji, Tetsuhiro

355

Effect of subway car design on vibration exposure  

Microsoft Academic Search

A field study was conducted to determine the vibration characteristics of subway train cars in terms of the whole-body vibration exposure levels transmitted to train operators. A total of five car types was tested and analyzed. To be able to compare different car types, vibration measurements were made under conditions for which all variables other than the car type were

Nihat Özkaya; David Goldsheyder; Bernardus Willems

1997-01-01

356

Free Vibration of the High Temperature Superconducting Maglev Vehicle Model  

Microsoft Academic Search

Free vibration of the high temperature superconducting (HTS) Maglev vehicle model has been investigated after an impulse force over the permanent magnet guideway. The impulse force was used to simulate the external disturbances on the HTS Maglev vehicle so as to study its vibration characteristics. In the experiments, the free vibration curves of time dependence of acceleration and frequency dependence

Zigang Deng; Jun Zheng; Honghai Song; Lu Liu; Lulin Wang; Ya Zhang; Suyu Wang; Jiasu Wang

2007-01-01

357

Six Axis Vehicle Vibration and its Effects on Comfort  

Microsoft Academic Search

The vibration in vehicles has been measured in three translational axes and three rotational axes at the passenger\\/seat interface and on the floor beneath the seat.The level, frequency and direction of vehicle vibration was shown to depend upon vehicle type, vehicle speed and road condition. Vibration associated with vehicle suspension, engine and seat characteristics can be identified. Comparison of vehicle

KENNETH C. PARSONS; ELERI M. WHITHAM; MICHAEL J. GRIFFIN

1979-01-01

358

Whiplash evokes descending muscle recruitment and sympathetic responses characteristic of startle  

PubMed Central

Whiplash injuries are the most common injuries following rear-end collisions. During a rear-end collision, the human muscle response consists of both a postural and a startle response that may exacerbate injury. However, most previous studies only assessed the presence of startle using data collected from the neck muscles and head/neck kinematics. The startle response also evokes a descending pattern of muscle recruitment and changes in autonomic activity. Here we examined the recruitment of axial and appendicular muscles along with autonomic responses to confirm whether these other features of a startle response were present during the first exposure to a whiplash perturbation. Ten subjects experienced a single whiplash perturbation while recording electromyography, electrocardiogram, and electrodermal responses. All subjects exhibited a descending pattern of muscle recruitment, and increasing heart rate and electrodermal responses following the collision. Our results provide further support that the startle response is a component of the response to whiplash collisions. PMID:24932015

Mang, Daniel WH; Siegmund, Gunter P; Blouin, Jean-Sébastien

2014-01-01

359

Vibrations of Euler's disk.  

PubMed

A model of a partially deformable Euler disk is presented that allows transverse vibrations to be treated with the techniques of classical analytical mechanics. The model clearly shows that the increasing audible frequency produced during motion can be directly related to the forcing effect of the reaction and the angular velocity of the contact point. The material of the disk seems to play a role in affecting the intensity and quality of the sound, but not its pitch. Moreover, the friction force grows rapidly with the decline of the disk, thus causing the slipping that is partially responsible for the abrupt end of the motion. The model also supports the conjecture [P. Kessler and O. M. O'Reilly, Regul. Chaotic Dyn. 7, 49 (2002)] that the vibrations themselves contribute to this phenomenon by causing a loss of contact with the surface at small angles of inclination. PMID:16089897

Villanueva, Roberto; Epstein, Marcelo

2005-06-01

360

Flow-induced vibration  

Microsoft Academic Search

This book reports on dimensional analysis; ideal fluid models; vortex-induced vibration; galloping and flutter; instability of tube and cylinder arrays; vibrations induced by oscillating flow; vibration induced by turbulence and sound; damping of structures; sound induced by vortex shedding; vibrations of a pipe containing a fluid flow; indices. It covers the analysis of the vibrations of structures exposed to fluid

1990-01-01

361

Coupled rotor/airframe vibration analysis  

NASA Technical Reports Server (NTRS)

A coupled rotor/airframe vibration analysis developed as a design tool for predicting helicopter vibrations and a research tool to quantify the effects of structural properties, aerodynamic interactions, and vibration reduction devices on vehicle vibration levels is described. The analysis consists of a base program utilizing an impedance matching technique to represent the coupled rotor/airframe dynamics of the system supported by inputs from several external programs supplying sophisticated rotor and airframe aerodynamic and structural dynamic representation. The theoretical background, computer program capabilities and limited correlation results are presented in this report. Correlation results using scale model wind tunnel results show that the analysis can adequately predict trends of vibration variations with airspeed and higher harmonic control effects. Predictions of absolute values of vibration levels were found to be very sensitive to modal characteristics and results were not representative of measured values.

Sopher, R.; Studwell, R. E.; Cassarino, S.; Kottapalli, S. B. R.

1982-01-01

362

Topographical representations of taste response characteristics in the rostral nucleus of the solitary tract in the rat.  

PubMed

The rostral nucleus of the solitary tract (rNST) is the first-order taste relay in rats. This study constructed topographical distributions of taste response characteristics (best-stimulus, response magnitude, and taste-tuning) from spike discharges of single neurons in the rNST. The rNST is divided into four subregions along the rostrocaudal (RC) axis, which include r1-r4. We explored single-neuron activity in r1-r3, using multibarreled glass microelectrodes. NaCl (N)-best neurons were localized to the rostral half of r1-r3, while HCl (H)-best and sucrose (S)-best neurons showed a tendency toward more caudal locations. NaCl and HCl (NH)-best neurons were distributed across r2-r3. The mean RC values and Mahalanobis distance indicated a significant difference between the distributions of N-best and NH-best neurons in which N-best neurons were located more rostrally. The region of large responses to NaCl (net response >5 spikes/s) overlapped with the distribution of N-best neurons. The region of large responses to HCl extended widely over r1-r3. The region of large responses to sucrose was in the medial part of r2. The excitatory region (>1 spike/s) for quinine overlapped with that for HCl. Neurons with sharp to moderate tuning were located primarily in r1-r2, while those with broad tuning were located in r2-r3. The robust responses to NaCl in r1-r2 primarily contributed to sharp to moderate taste-tuning. Neurons in r3 tended to have broad tuning, apparently due to small responses to both NaCl and HCl. Therefore, the rNST is spatially organized by neurons with distinct taste response characteristics, suggesting that these neurons serve different functional roles. PMID:24133228

Yokota, T; Eguchi, K; Hiraba, K

2014-01-01

363

Turbine blade vibration dampening  

DOEpatents

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.

Cornelius, Charles C. (San Diego, CA); Pytanowski, Gregory P. (San Diego, CA); Vendituoli, Jonathan S. (San Diego, CA)

1997-07-08

364

Turbine blade vibration dampening  

DOEpatents

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.

Cornelius, C.C.; Pytanowski, G.P.; Vendituoli, J.S.

1997-07-08

365

Personal characteristics in college students' evaluations of business ethics and corporate social responsibility  

Microsoft Academic Search

A survey of 138 college students reveals an undergraduate major has a greater influence on corporate social responsibility than business ethics. Business students are no less ethical than nonbusiness students. Females are more ethical and socially responsible than males. Age is negatively related to one's Machiavellian orientation and positively related to negative attitudes about corporate efforts at social responsibility. The

Peter Arlow

1991-01-01

366

Creating Filters with Arbitrary Response Characteristics for Use in Hearing and Speech Research.  

ERIC Educational Resources Information Center

This paper describes a computer software method for generating digital filters of any amplitude and phase response, for use in speech and hearing research. The method involves calculating the impulse response of the filter from a table that specifies the desired magnitude and phase response and then convolving the input signal with the impulse…

Hillenbrand, James; Houde, Robert A.

1996-01-01

367

Interpretation of DNA vibrational spectra by normal coordinate analysis.  

PubMed

1. In the following article we undertake a brief review of the most prominent DNA vibrational markers as observed experimentally by Raman and i.r. spectroscopies on polynucleotides and explain how a simplified valence force field can account for the evolution of the DNA vibrational spectra. 2. Our discussion made as a review of our previous investigations on the interpretation of DNA vibration modes, is based on some of the most characteristic and structure dependent DNA vibrational markers. PMID:2205520

Ghomi, M; Letellier, R; Liquier, J; Taillandier, E

1990-01-01

368

Dynamic response characteristics of thermoelectric generator predicted by a three-dimensional heat-electricity coupled model  

NASA Astrophysics Data System (ADS)

The practical application environments of thermoelectric generators (TEGs) always change, which make a requirement for studying the dynamic response characteristics of TEGs. This work develops a complete, three-dimensional and transient model to investigate this issue. The model couples the energy and electric potential equations. Seebeck effect, Peltier effect, Thomson effect, Joule heating and Fourier heat conduction are taken into account in this model. Dynamic output power and conversion efficiency of the TEG, which are caused by variations of the hot end temperature, cold end temperature and load current, are studied. The response hysteresis of the output power to the hot end and cold end temperatures, the overshoot or undershoot of the conversion efficiency are found and attributed to the delay of thermal diffusion. However, the output power is synchronous with the load current due to much faster electric response than thermal response.

Meng, Jing-Hui; Zhang, Xin-Xin; Wang, Xiao-Dong

2014-01-01

369

Sound and structural vibration - A review  

NASA Astrophysics Data System (ADS)

The fundamental principles of fluid-structure interaction are reviewed. Modern fields of application are discussed with attention given to sound radiation from vibrating structures, fluid loading of vibrating structures, airborne sound transmission through structural partitions, and acoustically induced response of structures. Theoretical and experimental techniques are outined with particular emphasis on recent developments.

Fahy, F. J.

370

Influence of chromium propionate on the carcass characteristics and immune response of commercial broiler birds under normal rearing conditions.  

PubMed

The study investigated the effect of supplementation of chromium propionate at different dosage levels (100 to 3,200 µg/kg of elemental chromium in feed) on the performance, carcass characteristics, and immune response of broiler birds. The study was conducted on male broiler chickens (Cobb 400) for a period of 42 d as per the completely randomized design. Seven hundred 1-d-old birds were randomly segregated into 7 treatment groups, each with 10 replicates, and each replicate having 10 birds. Weight gain, feed intake, carcass characteristics, immune response, and the serum biochemical parameters of birds were studied during the supplementation period. There was no significant response to chromium supplementation on weight gain, feed intake, FCR, and lymphoid organ weights for the overall study period of 42 d. With increased chromium dosage, the breast meat yield improved linearly (P = 0.045). Antibody response to Newcastle disease vaccination improved quadratically (P = 0.001) with increased dose of chromium in the diet. Improved cell-mediated immune response was indicated by the increase (quadratic, P = 0.00) in lymphocyte proliferation ratio with increased dose of chromium supplementation. Heterophil:lymphocyte ratio decreased (quadratic, P = 0.004) with chromium propionate dosage, suggestive of reduced stress levels. Chromium propionate supplementation also reduced serum glucose levels (quadratic, P = 0.008) and improved (quadratic, P = 0.016) the total protein levels. PMID:24604850

Rajalekshmi, M; Sugumar, C; Chirakkal, H; Ramarao, S V

2014-03-01

371

Investigation of crystal structure, vibrational characteristics and molecular conductivity of 2,3-dichloro-5,6-dicyno-p-benzoquinone  

NASA Astrophysics Data System (ADS)

Molecular geometries and vibrational spectra for the ground state of 2,3-dichloro-5,6-dicyno-p-benzoquinone (DDQ) and its anion (DDQ-) were computed using DFT method at the B3LYP level employing 6-311++G(d,p) basis set whereas for the first excited state (DDQ?), these were calculated using TD-DFT at the B3LYP level employing the 6-311++G(d,p) basis set available with the Gaussian 09 package. The spectra have been experimentally investigated and the observed IR and Raman bands have been assigned to different normal modes on the basis of the calculated potential energy distributions (PEDs). XRD of single crystal has been investigated to determine molecular and crystal structures of DDQ. In order to elucidate the transfer of electrons, electronic structure and electronic absorption have been calculated with the TD-DFT method. Vibronic interaction and its role in the appearance of superconductivity in the DDQ, DDQ- and DDQ? molecules have been investigated. The present XRD, molecular, electronic and vibronic studies indicate that mainly the ag Cdbnd O stretching and ring stretching modes participate in the charge transfer process.

Rani, Poonam; Rajput, Gunjan; Yadav, R. A.

2015-02-01

372

Investigation of crystal structure, vibrational characteristics and molecular conductivity of 2,3-dichloro-5,6-dicyno-p-benzoquinone.  

PubMed

Molecular geometries and vibrational spectra for the ground state of 2,3-dichloro-5,6-dicyno-p-benzoquinone (DDQ) and its anion (DDQ(-)) were computed using DFT method at the B3LYP level employing 6-311++G(d,p) basis set whereas for the first excited state (DDQ(?)), these were calculated using TD-DFT at the B3LYP level employing the 6-311++G(d,p) basis set available with the Gaussian 09 package. The spectra have been experimentally investigated and the observed IR and Raman bands have been assigned to different normal modes on the basis of the calculated potential energy distributions (PEDs). XRD of single crystal has been investigated to determine molecular and crystal structures of DDQ. In order to elucidate the transfer of electrons, electronic structure and electronic absorption have been calculated with the TD-DFT method. Vibronic interaction and its role in the appearance of superconductivity in the DDQ, DDQ(-) and DDQ(?) molecules have been investigated. The present XRD, molecular, electronic and vibronic studies indicate that mainly the ag CO stretching and ring stretching modes participate in the charge transfer process. PMID:25305626

Rani, Poonam; Rajput, Gunjan; Yadav, R A

2015-02-25

373

Vibrational echo spectroscopy: Spectral selectivity from vibrational coherence  

E-print Network

Vibrational echo spectroscopy: Spectral selectivity from vibrational coherence K. D. Rector, David a new method for performing two-dimensional vibrational spectroscopy using ultrafast pulsed infrared lasers, called vibrational echo spectroscopy VES . The VES technique can generate a vibrational spectrum

Fayer, Michael D.

374

Concorde noise-induced building vibrations, Sully Plantation - Report no. 2, Chantilly, Virginia  

NASA Technical Reports Server (NTRS)

Noise-induced building vibrations associated with Concorde operations were studied. The approach is to record the levels of induced vibrations and associated indoor/outdoor noise levels in selected homes, historic and other buildings near Dulles International Airport. Representative data are presented which were recorded at Sully Plantation, Chantilly, Virginia during the periods of May 20 through May 28, 1976, and June 14 through June 17, 1976. Recorded data provide relationships between the vibration levels of windows, walls, floors, and the noise associated with Concorde operations, other aircraft, and nonaircraft events. The results presented are drawn from the combined May-June data base which is considerably larger than the May data base covered. The levels of window, wall and floor vibratory response resulting from Concorde operations are higher than the vibratory levels associated with conventional aircraft. Furthermore, the vibratory responses of the windows are considerably higher than those of the walls and floors. The window response is higher for aircraft than recorded nonaircraft events and exhibits a linear response relationship with the overall sound pressure level. For a given sound pressure level, the Concorde may cause more vibration than a conventional aircraft due to spectral or other differences. However, the responses associated with Concorde appear to be much more dependent upon sound pressure level than spectral or other characteristics of the noise.

1976-01-01

375

Surface reactions responsible for atmosphere-sensitive characteristics of alternate-supply OMVPE growth of ZnSe  

NASA Astrophysics Data System (ADS)

An insight into surface chemical reactions responsible for organometallic vapor phase epitaxial growth of ZnSe under alternate supply of diethylzinc and dimethylselenium was provided by findings in laser-assisted free-radical doping experiments. Based on ab initio molecular orbital analyses, atmosphere-sensitive characteristics of the ZnSe growth were attributed to differences in the pathways and the corresponding adiabatic potential barriers between diethylzinc chemisorption onto hydrogen- and methyl-terminated Se-stabilized ZnSe surfaces.

Kanayama, Takuo; Omote, Noriyoshi; Kajimoto, Satoshi; Hayashi, Keiji

2004-10-01

376

[Studies on response characteristics of Cl, Br, I of microwave plasma torch atomic emission detector for gas chromatography].  

PubMed

The present paper deals with a microwave plasma torch atomic emission detector for gas chromatography. Argon is used as support gas, carrier gas and make-up gas. The effect of oxygen scavenger gas on the detection performance for chlorine, bromine and iodine is discussed. Detection limits, dynamic ranges, relative standard deviations and response characteristics of GC-MPT-AED for chlorine, bromine and iodine in organic compounds were studied. The results are favorable in comparing with GC-ICP-AED. PMID:12541563

Shi, Y H; Peng, Z H; Yang, W J; Cao, Y B; Yu, A M; Jin, Q H

2000-05-01

377

Downhole vibration sensing by vibration energy harvesting  

E-print Network

This thesis outlines the design of a prototype electromagnetic induction vibration energy harvesting device for use in a downhole environment. First order models of the necessary components for a generic vibration energy ...

Trimble, A. Zachary

2007-01-01

378

Black phosphorus nanoelectromechanical resonators vibrating at very high frequencies.  

PubMed

We report on the experimental demonstration of a new type of nanoelectromechanical resonator based on black phosphorus crystals. Facilitated by a highly efficient dry transfer technique, crystalline black phosphorus flakes are harnessed to enable drumhead resonators vibrating at high and very high frequencies (HF and VHF bands, up to ?100 MHz). We investigate the resonant vibrational responses from the black phosphorus crystals by devising both electrical and optical excitation schemes, in addition to measuring the undriven thermomechanical motions in these suspended nanostructures. Flakes with thicknesses from ?200 nm down to ?20 nm clearly exhibit elastic characteristics transitioning from the plate to the membrane regime. Both frequency- and time-domain measurements of the nanomechanical resonances show that very thin black phosphorus crystals hold interesting potential for moveable and vibratory devices and for semiconductor transducers where high-speed mechanical motions could be coupled to the attractive electronic and optoelectronic properties of black phosphorus. PMID:25385657

Wang, Zenghui; Jia, Hao; Zheng, Xuqian; Yang, Rui; Wang, Zefang; Ye, G J; Chen, X H; Shan, Jie; Feng, Philip X-L

2014-12-18

379

Surface Acoustic Wave (SAW) Vibration Sensors  

PubMed Central

In the paper a feasibility study on the use of surface acoustic wave (SAW) vibration sensors for electronic warning systems is presented. The system is assembled from concatenated SAW vibration sensors based on a SAW delay line manufactured on a surface of a piezoelectric plate. Vibrations of the plate are transformed into electric signals that allow identification of the sensor and localization of a threat. The theoretical study of sensor vibrations leads us to the simple isotropic model with one degree of freedom. This model allowed an explicit description of the sensor plate movement and identification of the vibrating sensor. Analysis of frequency response of the ST-cut quartz sensor plate and a damping speed of its impulse response has been conducted. The analysis above was the basis to determine the ranges of parameters for vibrating plates to be useful in electronic warning systems. Generally, operation of electronic warning systems with SAW vibration sensors is based on the analysis of signal phase changes at the working frequency of delay line after being transmitted via two circuits of concatenated four-terminal networks. Frequencies of phase changes are equal to resonance frequencies of vibrating plates of sensors. The amplitude of these phase changes is proportional to the amplitude of vibrations of a sensor plate. Both pieces of information may be sent and recorded jointly by a simple electrical unit. PMID:22247694

Filipiak, Jerzy; Solarz, Lech; Steczko, Grzegorz

2011-01-01

380

Actively controlled vibration welding system and method  

DOEpatents

A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

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

2013-04-02

381

Research of an Active Tunable Vibration Absorber for Helicopter Vibration Control  

Microsoft Academic Search

Significant structural vibration is an undesirable characteristic in helicopter flight that leads to structural fatigue, poor ride quality for passengers and high acoustic signature. Previous Individual Blade Control (IBC) techniques to reduce these effects have been hindered by electromechanical limitations of piezoelectric actuators. The Smart Spring is an active tunable vibration absorber using IBC approach to adaptively alter the “structural

Chen Yong; David G. Zimcik; Viresh K. Wickramasinghe; Fred Nitzsche

2003-01-01

382

Numerical investigation on flow-induced vibration of a triangular cylinder at a low Reynolds number  

NASA Astrophysics Data System (ADS)

Flow-induced vibration (FIV) of a triangular cylinder is numerically investigated at a Reynolds number of Re = 100. The four-step fractional finite element method is employed to solve the two-dimensional (2D) incompressible Navier–Stokes equations. The cylinder is endowed with a two-degree-of-freedom motion with the reduced mass ratio of Mr = 2. Three typical flow incidence angles, ? = 0°, 30° and 60°, are examined to identify the effect of incidence angle on the vibration characteristics of the cylinder. For each ?, computations are conducted in a wide range of reduced velocities 2 Ur ? 18. The numerical results show that at ? = 0° and 30°, the responses of the cylinder are dominated by vortex-induced vibration which resembles that of a circular cylinder. At ? = 0°, the peak amplitude of transverse vibration is the smallest among the three investigated ?, and most of the cylinder motions exhibit a regular figure-eight trajectory. Some single-loop trajectories are observed at ? = 30°, where the vibration frequency in the in-line direction is always identical to that in the transverse direction. At ? = 60°, the triangular cylinder undergoes a typical transverse galloping with large amplitude and low frequency, and the vibration trajectories appear to be regular or irregular figure-eight patterns, which are strongly affected by the reduced velocity.

Wang, Huakun; Zhao, Dongliang; Yang, Wenyu; Yu, Guoliang

2015-02-01

383

Estimating text legibility of a mobile display on the basis of translational vibration caused by walking  

E-print Network

by walking Maria Olkkonen Terhi Mustonen Abstract -- In this study, the effect of vibration on mobile elements depending on the characteristics and the source of vibration.4,5,8­10 Effects of vibrationEstimating text legibility of a mobile display on the basis of translational vibration caused

Olkkonen, Maria

384

Kinaesthetic role of muscle afferents in man, studied by tendon vibration and microneurography  

Microsoft Academic Search

The characteristics of vibration-induced illusory joint movements were studied in healthy human subjects. Unseen by the subject, constant frequency vibration trains applied to the distal tendon of the Triceps or Biceps induced an almost constant velocity illusory movement of the elbow whose direction corresponded to that of a joint rotation stretching the vibrated muscle. Vibration trains of the same duration

J. P. Roll; J. P. Vedel

1982-01-01

385

Vibration syndrome and vibration in pedestal grinding.  

PubMed

At one Finnish foundry all the workers had typical symptoms of vibration induced white finger (VWF) after they began using a new type of pedestal grinding machine. The objectives of this study were to establish the severity of the symptoms and the difference in vibration exposure between the new and the old machines. Vibration detection thresholds and grip forces were measured, as well as the vibration in the casting and in the wrist simultaneously. The mean latency for VWF among the grinders was 10.3 months after the change of pedestal grinding machines. All the grinders had numbness in their hands. The vibration detection threshold was significantly higher for the grinders than for their referents. At the same circle speed, the new wheels caused vibration levels up to 12 dB more than the old wheels. The circle speed had a slight influence on the vibration. The vibration levels of light (0.5 kg) casting were up to 25 dB higher than the heavy (5 kg) casting. The use of a pneumatic pressing device decreased the vibration levels in the wrist by 5-10 dB. The increase in vibration, which occurred when the new wheels were taken into use, was too small to explain such a dramatic outbreak of VWF. This led to the conclusion that some other feature such as the impulse character of the vibration also contributed to the effects of vibration. PMID:6626471

Starck, J; Färkkilä, M; Aatola, S; Pyykkö, I; Korhonen, O

1983-11-01

386

Corporate Responsiveness to Community StakeholdersEffects of Contextual and Organizational Characteristics  

Microsoft Academic Search

Corporate community responsiveness relates to business activities that are integral parts of a firm’s operations and are designed to benefit the firm through benefiting the local communities. Using data from commercial banks in the United States between 1997 and 2000, the authors measured banks’ corporate community responsiveness by their Community Reinvestment Act (CRA) lending activities and their performance ratings by

Nada Kobeissi; Fariborz Damanpour

2009-01-01

387

The influence of domain size on the response characteristics of a hurricane storm surge model  

Microsoft Academic Search

The influence of domain size on boundary condition specification and on computed storm surge response is investigated. Storm surge response along the Florida shelf in the Gulf of Mexico due to Hurricane Kate is examined over three domains using two different open ocean boundary forcing functions, a still water (or zero elevation) condition and an inverted barometer condition which accounts

C. A. Blain; J. J. Westerink; R. A. Luettich Jr

1994-01-01

388

Characteristics of indirect pharmacodynamic models and applications to clinical drug responses.  

PubMed

This review describes four basic physiologic indirect pharmacodynamic response (IDR) models which have been proposed to characterize the pharmacodynamics of drugs that act by indirect mechanisms such as inhibition or stimulation of the production or dissipation of factors controlling the measured effect. The principles underlying IDR models and their response patterns are described. The applicability of these basic IDR models to characterize pharmacodynamic responses of diverse drugs such as inhibition of gastric acid secretion by nizatidine and stimulation of MX protein synthesis by interferon alpha-2a is demonstrated. A list of other uses of these models is provided. These models can be readily extended to accommodate additional complexities such as nonstationary or circadian baselines, equilibration delay, depletion or accumulation of a precursor pool, sigmoidicity, or other mechanisms. Indirect response models which have a logical mechanistic basis account for time-delays in many responses and are widely applicable in clinical pharmacology. PMID:9517366

Sharma, A; Jusko, W J

1998-03-01

389

Response characteristics of pruriceptive and nociceptive trigeminoparabrachial tract neurons in the rat.  

PubMed

We tested the possibility that the trigeminoparabrachial tract (VcPbT), a projection thought to be importantly involved in nociception, might also contribute to sensation of itch. In anesthetized rats, 47 antidromically identified VcPbT neurons with receptive fields involving the cheek were characterized for their responses to graded mechanical and thermal stimuli and intradermal injections of pruritogens (serotonin, chloroquine, and ?-alanine), partial pruritogens (histamine and capsaicin), and an algogen (mustard oil). All pruriceptive VcPbT neurons were responsive to mechanical stimuli, and more than half were additionally responsive to thermal stimuli. The majority of VcPbT neurons were activated by injections of serotonin, histamine, capsaicin, and/or mustard oil. A subset of neurons were inhibited by injection of chloroquine. The large majority of VcPbT neurons projected to the ipsilateral and/or contralateral external lateral parabrachial and Kölliker-Fuse nuclei, as evidenced by antidromic mapping techniques. Analyses of mean responses and spike-timing dynamics of VcPbT neurons suggested clear differences in firing rates between responses to noxious and pruritic stimuli. Comparisons between the present data and those previously obtained from trigeminothalamic tract (VcTT) neurons demonstrated several differences in responses to some pruritogens. For example, responses of VcPbT neurons to injection of serotonin often endured for nearly an hour and showed a delayed peak in discharge rate. In contrast, responses of VcTT neurons endured for roughly 20 min and no delayed peak of firing was noted. Thus the longer duration responses to 5-HT and the delay in peak firing of VcPbT neurons better matched behavioral responses to stimulation in awake rats than did those of VcTT neurons. The results indicate that VcPbT neurons may have important roles in the signaling of itch as well as pain. PMID:25298386

Jansen, Nico A; Giesler, Glenn J

2015-01-01

390

LANDSAT 3 return beam vidicon response artifacts: A report on RBV photographic product characteristics and quality coding system  

NASA Technical Reports Server (NTRS)

Analysis of large volumes of LANDSAT 3 RBV digital data that were converted to photographic form led to the firm identification of several visible artifacts (objects or structures not normally present, but producted by an external agency or action) in the imagery. These artifacts were identified, categorized, and traced directly to specific sensor response characteristics. None of these artifacts is easily removed and all cases remain under active study of possible future enhancement. The seven generic categories of sensor response artifacts identified to date include: (1) shading and stairsteps; (2) corners out of focus; (3) missing reseaus; (4) reseau distortion and data distortion; (5) black vertical line; (6) grain effect; and (7) faceplate contamination. An additional category under study, but not yet determined to be caused by sensor response, is a geometric anomaly. Examples of affected imagery are presented to assist in distinguishing between image content and innate defects caused by the sensor system.

Clark, B. P.

1981-01-01

391

Damping phenomena in a wire rope vibration isolation system  

NASA Technical Reports Server (NTRS)

A study of the dynamic characteristics of a wire rope vibration isolation system constructed with helical isolators is presented. Emphasis is placed on the analytical modeling of damping mechanisms in the system. An experimental investigation is described in which the static stiffness curve, hysteresis curves, phase trajectories, and frequency response curves were obtained. A semi-empirical model having nonlinear stiffness, nth-power velocity damping, and variable Coulomb friction damping is developed and results are compared to experimental data. Conclusions about dynamic phenomena in the wire rope system are made based on the experimental and semi-empirical results.

Tinker, Michael L.; Cutchins, Malcolm A.

1990-01-01

392

Rotor vibration reduction using rotor balancing and command shaping  

Microsoft Academic Search

Mechanical vibrations are intrinsically characteristic of rotating machines. Apart from that, other turbomachine characteristics, such as rotor unbalance, non- linearity and shaft variable stiffness can introduce severe disturbances in the operation of the machine. In this paper two complementary methods to reduce rotor vibration, rotor balancing and command shaping, are applied to a flexible rotor machine. The results will show

G. Peláez; F. Oliveira; M. P. Donsión

393

Cancer breakthrough pain characteristics and responses to treatment at a VA medical center  

Microsoft Academic Search

The purpose of this study is to analyze cancer breakthrough pain (BP) characteristics and how BP responds to conventional cancer pain management. Seventy-four cancer pain patients with worst pain severity ?4 out of 10 completed the Brief Pain Inventory (BPI), Memorial Symptom Assessment Scale-Short Form, Functional Assessment Cancer Therapy and Breakthrough Pain Questionnaires (BPQ) at an initial interview. Agency for

Shirley S Hwang; Victor T Chang; Basil Kasimis

2003-01-01

394

Control and response characteristics of a magnetorheological fluid damper for passenger vehicles  

Microsoft Academic Search

This paper presents control characteristics of a semi-active magneto-rheological (MR) fluid damper for a passenger vehicle. A cylindrical MR damper is devised and its governing equation is derived. After verifying that the damping force of the MR damper can be continuously tuned by the intensity of the magnetic field, PID controller is employed to achieve the desired damping force. The

Seung-Bok Choi; HwanSoo Lee; SungRyong Hong; ChaeCheon Cheong

2000-01-01

395

Spatially variable response of native fish assemblages to discharge, predators and habitat characteristics in an  

E-print Network

characteristics in an arid-land river JEROME A. STEFFERUD*, KEITH B. GIDO AND DAVID L. PROPST *J.A. Stefferud, USDA Forest Service (retired), Phoenix, AZ, U.S.A. K.B. Gido, Kansas State University, Manhattan, KS assemblages and habitats were sampled annually at fixed sites in three tributaries of the Gila River catchment

Gido, Keith B.

396

REPRODUCTIVE RESPONSES AND CARCASS CHARACTERISTICS OF RAM LAMBS FED ENDOPHYTE-INFECTED TALL FESCUE  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to examine the influence of endophyte-infected tall fescue on reproductive development and function and carcass characteristics of ram lambs. Hampshire and Suffolk rams, 214 d of age, were fed individually a diet of endophyte-free (EF; n = 8) or infected (EI; n = 9) ...

397

Responses to different charity appeals: the impact of donor characteristics on the amount of donations  

Microsoft Academic Search

Posits that, at a time when demand for charity services is increasing and donations to charity are remaining static, careful administrative use of funds and accurate targeting of likely donors are vital for charities’ survival. Utilizes empirical data from a nationwide survey of donating behaviour to identify whether different characteristics of donors affect the levels of donation to various methods

Bodo B. Schlegelmilch; Alix Love; Adamantios Diamantopoulos

1997-01-01

398

Nonlinear dynamics of a stack/cable system subjected to vortex-induced vibration  

SciTech Connect

A model of a stack/wire system, wind-induced vibration of the stack based on an unsteady-flow theory, and nonlinear dynamics of the stack`s heavy elastic suspended cables was developed in this study. The response characteristics of the stack and cables are presented for different conditions. The dominant excitation mechanisms are lock-in resonance of the stack by vortex shedding and parametric resonance of suspended cables by stack motion at their support ends.

Cai, Y.; Chen, S.S. [Argonne National Lab., IL (United States). Energy Technology Div.

1997-08-01

399

Nonlinear dynamics of a stack/cable system subjected to vortex-induced vibration  

SciTech Connect

A model of a stack/wire system, wind-induced vibration of the stack based on an unsteady-flow theory, and nonlinear dynamics of the stack`s heavy elastic suspended cables was developed in this study. The response characteristics of the stack and cables are presented for different conditions. The dominant excitation mechanisms are lock-in resonance of the stack by vortex shedding and parametric resonance of suspended cables by stack motion at their support ends.

Cai, Y.; Chen, S.S. [Argonne National Lab., IL (United States). Energy Technology Div.

1995-12-31

400

Vibration analysis for a coupled beam-sdof system by using the recurrence equation method  

NASA Astrophysics Data System (ADS)

This paper presents the vibration analysis of a coupled system composed of a beam and a single-degree-of-freedom (sdof) system. The harmonic responses of this kind of system are formulated by means of the recurrence equation method. In addition, the natural characteristics of the system are also analyzed. Numerical examples of the undamped system are given and compared with the published results, and an excellent correlation shows that the study work in this paper is correct.

Tang, H. B.; Wu, C. J.; Huang, X. Q.

2008-04-01

401

Noncontact Electromagnetic Vibration Source  

NASA Technical Reports Server (NTRS)

Metal aircraft skins scanned rapidly in vibration tests. Relatively simple combination of permanent magnets and electromagnet serves as noncontact vibration source for nondestructive testing of metal aircraft skins. In test, source excites vibrations, and vibration waveforms measured, then analyzed for changes in resonances signifying cracks and other flaws.

Namkung, Min; Fulton, James P.; Wincheski, Buzz A.

1994-01-01

402

The European Vibration Directive  

Microsoft Academic Search

The European Union adopted a Directive in 2002 on minimum requirements for the health and safety of workers exposed to vibration. This is known as the Physical Agents (Vibration) Directive. It builds on existing general employers' duties to manage risks to health and safety, and introduces exposure action and limit values for both hand-arm vibration and whole-body vibration, setting minimum

Chris M. NELSON; Paul F. BRERETON

2005-01-01

403

Experimental Analysis of Steady-State Maneuvering Effects on Transmission Vibration Patterns Recorded in an AH-1 Cobra Helicopter  

NASA Technical Reports Server (NTRS)

Flight experiment was designed primarily to determine the extent to which steady-state maneuvers influence characteristic vibration patterns measured at the input pinion and output annulus gear locations of the main transmission. If results were to indicate that maneuvers systematically influence vibration patterns, more extensive studies would be planned to explore the response surface. It was also designed to collect baseline data for comparison with experimental data to be recorded at a later date from test stands at Glenn Research Center. Finally, because this was the first vibration flight study on the Cobra aircraft, considerable energy was invested in developing an in-flight recording apparatus, as well as exploring acceleration mounting methods, and generally learning about the overall vibratory characteristics of the aircraft itself.

Huff, Edward M.; Dzwonczyk, Mark; Norvig, Peter (Technical Monitor)

2000-01-01

404

Modular Wideband Active Vibration Absorber  

NASA Technical Reports Server (NTRS)

A comparison of space experiments with previous missions shows a common theme. Some of the recent experiments are based on the scientific fundamentals of instruments of prior years. However, the main distinguishing characteristic is the embodiment of advances in engineering and manufacturing in order to extract clearer and sharper images and extend the limits of measurement. One area of importance to future missions is providing vibration free observation platforms at acceptable costs. It has been shown by researchers that vibration problems cannot be eliminated by passive isolation techniques alone. Therefore, various organizations have conducted research in the area of combining active and passive vibration control techniques. The essence of this paper is to present progress in what is believed to be a new concept in this arena. It is based on the notion that if one active element in a vibration transmission path can provide a reasonable vibration attenuation, two active elements in series may provide more control options and better results. The paper presents the functions of a modular split shaft linear actuator developed by NASA's Goddard Space Flight Center and University of Massachusetts Lowell. It discusses some of the control possibilities facilitated by the device. Some preliminary findings and problems are also discussed.

Zewari, Wahid; Lee, Kenneth Y.; Smith, David R.

1999-01-01

405

Ambient Vibration Testing for Story Stiffness Estimation of a Heritage Timber Building  

PubMed Central

This paper investigates dynamic characteristics of a historic wooden structure by ambient vibration testing, presenting a novel estimation methodology of story stiffness for the purpose of vibration-based structural health monitoring. As for the ambient vibration testing, measured structural responses are analyzed by two output-only system identification methods (i.e., frequency domain decomposition and stochastic subspace identification) to estimate modal parameters. The proposed methodology of story stiffness is estimation based on an eigenvalue problem derived from a vibratory rigid body model. Using the identified natural frequencies, the eigenvalue problem is efficiently solved and uniquely yields story stiffness. It is noteworthy that application of the proposed methodology is not necessarily confined to the wooden structure exampled in the paper. PMID:24227999

Min, Kyung-Won; Kim, Junhee; Park, Sung-Ah; Park, Chan-Soo

2013-01-01

406

Flow-induced vibration  

SciTech Connect

This book reports on dimensional analysis; ideal fluid models; vortex-induced vibration; galloping and flutter; instability of tube and cylinder arrays; vibrations induced by oscillating flow; vibration induced by turbulence and sound; damping of structures; sound induced by vortex shedding; vibrations of a pipe containing a fluid flow; indices. It covers the analysis of the vibrations of structures exposed to fluid flows; explores applications for offshore platforms and piping; wind-induced vibration of buildings, bridges, and towers; and acoustic and mechanical vibration of heat exchangers, power lines, and process ducting.

Blevins, R.D.

1990-01-01

407

A comparison of power output from linear and nonlinear kinetic energy harvesters using real vibration data  

NASA Astrophysics Data System (ADS)

The design of vibration energy harvesters (VEHs) is highly dependent upon the characteristics of the environmental vibrations present in the intended application. VEHs can be linear resonant systems tuned to particular frequencies or nonlinear systems with either bistable operation or a Duffing-type response. This paper provides detailed vibration data from a range of applications, which has been made freely available for download through the Energy Harvesting Network’s online data repository. In particular, this research shows that simulation is essential in designing and selecting the most suitable vibration energy harvester for particular applications. This is illustrated through C-based simulations of different types of VEHs, using real vibration data from a diesel ferry engine, a combined heat and power pump, a petrol car engine and a helicopter. The analysis shows that a bistable energy harvester only has a higher output power than a linear or Duffing-type nonlinear energy harvester with the same Q-factor when it is subjected to white noise vibration. The analysis also indicates that piezoelectric transduction mechanisms are more suitable for bistable energy harvesters than electromagnetic transduction. Furthermore, the linear energy harvester has a higher output power compared to the Duffing-type nonlinear energy harvester with the same Q factor in most cases. The Duffing-type nonlinear energy harvester can generate more power than the linear energy harvester only when it is excited at vibrations with multiple peaks and the frequencies of these peaks are within its bandwidth. Through these new observations, this paper illustrates the importance of simulation in the design of energy harvesting systems, with particular emphasis on the need to incorporate real vibration data.

Beeby, Stephen P.; Wang, Leran; Zhu, Dibin; Weddell, Alex S.; Merrett, Geoff V.; Stark, Bernard; Szarka, Gyorgy; Al-Hashimi, Bashir M.

2013-07-01

408

Bone Response to Surface-Modified Titanium Implants: Studies on the Early Tissue Response to Implants with Different Surface Characteristics  

PubMed Central

In a series of experimental studies, the bone formation around systematically modified titanium implants is analyzed. In the present study, three different surface modifications were prepared and evaluated. Glow-discharge cleaning and oxidizing resulted in a highly stoichiometric TiO2 surface, while a glow-discharge treatment in nitrogen gas resulted in implants with essentially a surface of titanium nitride, covered with a very thin titanium oxide. Finally, hydrogen peroxide treatment of implants resulted in an almost stoichiometric TiO2, rich in hydroxyl groups on the surface. Machined commercially pure titanium implants served as controls. Scanning Auger Electron Spectroscopy, Scanning Electron Microscopy, and Atomic Force Microscopy revealed no significant differences in oxide thickness or surface roughness parameters, but differences in the surface chemical composition and apparent topography were observed. After surface preparation, the implants were inserted in cortical bone of rabbits and evaluated after 1, 3, and 6 weeks. Light microscopic evaluation of the tissue response showed that all implants were in contact with bone and had a large proportion of newly formed bone within the threads after 6 weeks. There were no morphological differences between the four groups. Our study shows that a high degree of bone contact and bone formation can be achieved with titanium implants of different surface composition and topography. PMID:24174936

Larsson Wexell, C.; Thomsen, P.; Aronsson, B.-O.; Tengvall, P.; Rodahl, M.; Lausmaa, J.; Kasemo, B.; Ericson, L. E.

2013-01-01

409

A simulation investigation of the effects of engine-and thrust-response characteristics on helicopter handling qualities  

NASA Technical Reports Server (NTRS)

A multi-phase program is being conducted to study, in a generic sense and through ground simulation, the effects of engine response, rotor inertia, rpm control, excess power, and vertical damping on specific maneuvers included in nap-of-the-Earth (NOE) operations. The helicopter configuration with an rpm-governed gas-turbine engine are considered. Handling-qualities-criteria data are considered in light of aspects peculiar to rotary-wing and NOE operations. The results of three moving-based piloted simulation studies are summarized and the frequency, characteristics of the helicopter thrust response which set it apart from other VTOL types are explained. Power-system response is affected by both the engine-governor response and the level of rotor inertia. However, results indicate that with unlimited power, variations in engine response can have a significant effect on pilot rating, whereas changes in rotor inertia, in general, do not. The results also show that any pilot interaction required to maintain proper control can significantly degrade handling qualities. Data for variations in vertical damping and collective sensitivity are compared with existing handling-qualities specifications, MIL-F-83300 and AGARD 577, and show a need for higher minimums for both damping and sensitivity for the bob-up task. Results for cases of limited power are also shown.

Corless, L. D.; Blanken, C. L.

1983-01-01

410

Spatiotemporal multifractal characteristics of electromagnetic radiation in response to deep coal rock bursts  

NASA Astrophysics Data System (ADS)

Dynamic collapses of deeply mined coal rocks are severe threats to miners, in order to predict the collapses more accurately using electromagnetic radiation (EMR), we investigate the spatiotemporal multifractal characteristics and formation mechanism of EMR induced by underground coal mining. Coal rock in the burst-prone zone often exchanges materials and energy with its environment and gradually transits from its original stable equilibrium structure to a non-equilibrium dissipative structure with implicit spatiotemporal complexity or multifractal structures, resulting in temporal variation in multifractal EMR. The inherent law of EMR time series during damage evolution was analyzed by using time-varying multifractal theory. Results show that the time-varying multifractal characteristics of EMR are determined by damage evolutions process, the dissipated energy caused by damage evolutions such as crack propagation, fractal sliding and shearing can be regarded as the fingerprint of various EMR micro-mechanics. Dynamic spatiotemporal multifractal spectrum of EMR considers both spatial (multiple fractures) and temporal (dynamic evolution) characteristics of coal rocks, and records the dynamic evolution processes of rock bursts. Thus, it can be used to evaluate the coal deformation and fracture process. The study is of significance for us to in-depth understand EMR mechanism and to increase the accuracy of applying the EMR method to forecast dynamic disasters.

Shaobin, H.; Enyuan, W.; Xiaofei, L.

2014-04-01

411

Surfactant effect on functionalized carbon nanotube coated snowman-like particles and their electro-responsive characteristics  

SciTech Connect

The core–shell structured snowman-like (SL) microparticles coated by functionalized multi-walled carbon nanotube (MWNT) were prepared in the presence of different surfactants including cationic surfactant-cetyl trimethylammonium bromide (CTAB) and anionic surfactant-sodium lauryl sulfate (SDS). The effect of surfactants on adsorption onto SL particles was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and conductivity. The cationic surfactant is found to be more effective than anionic surfactant for helping nanotube adsorbed onto microparticle due to the presence of electrostatic interaction between the functionalized MWNT and the surfactant. Furthermore, the MWNT/SL particles dispersed in silicone oil exhibited a typical fibril structure of the electrorheological characteristics under an applied electric field observed by an optical microscope (OM), in which the state of nanotubes wrapped on the particles strongly affects their electro-responsive characteristics.

Zhang, Ke; Liu, Ying Dan [Department of Polymer Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of)] [Department of Polymer Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of); Choi, Hyoung Jin, E-mail: hjchoi@inha.ac.kr [Department of Polymer Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of)

2012-10-15

412

Three-dimensional solutions for the free vibrations and buckling of thermally stressed multilayered angle-ply composite plates  

NASA Technical Reports Server (NTRS)

Analytic three-dimensional elasticity solutions are developed for the free vibration and buckling of thermally stressed rectangular multilayered angle-ply anisotropic plates which are assumed to have an antisymmetric lamination with respect to the middle plane. Sensitivity derivatives are evaluated and used to investigate the sensitivity of the vibration and buckling responses to variations in the different lamination and material parameters of the plate. A Duhamel-Neumann-type constitutive model is used, and the material properties are assumed to be independent of temperature. Numerical results are presented, showing the effects of variations in the material characteristics and fiber orientation of different layers, as well as the effect of initial thermal deformation on the vibrational and buckling responses of the plate.

Noor, Ahmed K.; Burton, W. S.

1992-01-01

413

Three-dimensional solutions for the free vibrations and buckling of thermally stressed multilayered angle-ply composite plates  

SciTech Connect

Analytic three-dimensional elasticity solutions are developed for the free vibration and buckling of thermally stressed rectangular multilayered angle-ply anisotropic plates which are assumed to have an antisymmetric lamination with respect to the middle plane. Sensitivity derivatives are evaluated and used to investigate the sensitivity of the vibration and buckling responses to variations in the different lamination and material parameters of the plate. A Duhamel-Neumann-type constitutive model is used, and the material properties are assumed to be independent of temperature. Numerical results are presented, showing the effects of variations in the material characteristics and fiber orientation of different layers, as well as the effect of initial thermal deformation on the vibrational and buckling responses of the plate. 20 refs.

Noor, A.K.; Burton, W.S. (NASA, Langley Research Center, Hampton, VA (United States))

1992-12-01

414

Plant Growth in Controlled Environments in Response to Characteristics of Nutrient Solutions  

NASA Technical Reports Server (NTRS)

Emphasis was given to environmental factors that alter the flux of carbohydrate from the shoot to the root system to support the absorption of nitrogen and the subsequent interaction between nitrogen uptake and whole plant growth. Only the nitrate form of nitrogen was utilized in order to establish base line responses for evaluation of future studies utilizing both ammonium and nitrate.

Raper, C. D., Jr.

1982-01-01

415

Response characteristics of primary auditory cortex neurons underlying perceptual asymmetry of ramped and damped sounds.  

PubMed

Sound envelope plays a crucial role in perception: ramped sounds (slow attack and quick decay) are louder in strength and longer in subjective duration than damped sounds (quick attack and slow decay) even if they are equal in intensity and physical duration. To explain the asymmetrical perception, the perceptual constancy hypothesis supposes that the listener eliminates the slow decay of damped sounds from the judgment of perception, while the persistence of perception hypothesis supposes asymmetrical neural responses after the source has stopped. To understand neural mechanisms underlying the perceptual asymmetry, we explored response properties of the primary auditory cortex (A1) neurons during ramped and damped stimuli in awake cats. We found two distinct types of cells tuned to specific features of the sound envelope: edge cells sensitive to the temporal edge, such as quick attack and decay, while slope cells sensitive to slow attack and decay. The former needs a short (<2.5 ms) period of stimulus duration for evoking maximal peak responses, while the latter needs a long (20 ms) period, suggesting that the timescale of processing underlies differential sensitivity between the cell types. The findings suggest that perceptual constancy is not yet be executed at A1 because the specific cells distinguishing the direction of amplitude change (attack or decay) are lacking in A1. On the other hand, there is evidence of persistence of perception: overall response duration during ramped sound reached 1.4 times longer than that during damped sound, originating mainly from the response asymmetry of the edge cell (sensitive to the quick decay of ramped sounds but not to the slow decay of damped sounds), and neuronal persistence of excitation after the termination of ramped sounds was substantially longer than that of damped sounds, corresponding to the psychological evidence of persistence of perception. PMID:24177068

Wang, J; Qin, L; Chimoto, S; Tazunoki, S; Sato, Y

2014-01-01

416

www.elsevier.com/locate/jsvi Journal of Sound and Vibration 262 (2003) 877888  

E-print Network

JOURNAL OF SOUND AND VIBRATION www.elsevier.com/locate/jsvi Journal of Sound and Vibration 262. Introduction Dynamic responses of the human body to vibration have been the subject of study for a long time, and the effect of whole-body vertical vibration on visual performance has also been studied [1­7]. In laboratory

Peli, Eli

417

Selected new developments in vibrational structure theory: potential construction and vibrational wave function calculations.  

PubMed

This perspective addresses selected recent developments in the theoretical calculation of vibrational spectra, energies, wave functions and properties. The theoretical foundation and recently developed computational protocols for constructing hierarchies of vibrational Hamiltonian operators are reviewed. A many-mode second quantization (SQ) formulation is discussed prior to the discussion of anharmonic wave functions. Emphasis is put on vibrational self-consistent field (VSCF) based methods and in particular vibrational coupled cluster (VCC) theory. Other issues are also reviewed briefly, such as inclusion of thermal effects, response theoretical calculation of spectra, and the difficulty in treating dense spectra. PMID:22491444

Christiansen, Ove

2012-04-10

418

Dynamic characteristics of launch vehicle and spacecraft connected by clamp band  

Microsoft Academic Search

Spacecraft is usually fastened to the launch vehicle by clamp band in the aerospace industry. The application of clamp band joint brings local stiffness variation to the launch vehicle and spacecraft (LV\\/SC) system and affects the dynamic characteristics of the system. In this paper, the dynamic responses of the LV\\/SC system to the vibration and impact excitations were studied, where

Zhao-Ye Qin; Shao-Ze Yan; Fu-Lei Chu

2011-01-01

419

Vibration modeling and supression in tennis racquets.  

SciTech Connect

The size of the 'sweet spot' is one measure of tennis racquet performance. In terms of vibration, the sweet spot is determined by the placement of nodal lines across the racquet head. In this studx the vibrational characteristics of a tennis racquet are explorod to discover the size and location of the sweet spot. A numerical model of the racquet is developed using finite element analysis and the model is verified using the results from an experimental modal analysis. The affects of string tension on the racquet's sweet spot and mode shapes are then quantified. An investigation is also carried out to determine how add-on vibrational datnpers affect the sweet spot.

Farrar, C. R. (Charles R.); Buechler, M. A. (Miles A.); Espino, Luis; Thompson, G. A. (Gordon A.)

2003-01-01

420

Energy harvesting vibration sources for microsystems applications  

Microsoft Academic Search

This paper reviews the state-of-the art in vibration energy harvesting for wireless, self-powered microsystems. Vibration-powered generators are typically, although not exclusively, inertial spring and mass systems. The characteristic equations for inertial-based generators are presented, along with the specific damping equations that relate to the three main transduction mechanisms employed to extract energy from the system. These transduction mechanisms are: piezoelectric,

S P Beeby; M J Tudor; N M White

2006-01-01

421

Molecular signatures of neoadjuvant endocrine therapy for breast cancer: characteristics of response or intrinsic resistance  

Microsoft Academic Search

Approximately 30% of patients with estrogen receptor (ER) positive breast cancers exhibit de novo or intrinsic resistance\\u000a to endocrine therapies. The purpose of this study was to define genes that distinguish ER+ resistant from ER+ responsive tumors,\\u000a prior to the start of hormone therapies. Previously untreated post-menopausal patients with ER+ breast cancers were treated\\u000a for 4 months in a neoadjuvant setting with

Djuana M. E. Harvell; Nicole S. Spoelstra; Meenakshi Singh; James L. McManaman; Christina Finlayson; Tzu Phang; Susan Trapp; Lawrence Hunter; Wendy W. Dye; Virginia F. Borges; Anthony Elias; Kathryn B. Horwitz; Jennifer K. Richer

2008-01-01

422

Effect of dietary selenium and vitamin E on ganders' response to semen collection and ejaculate characteristics.  

PubMed

Compared to other domestic bird species, geese exhibit the lowest reproductive efficiency (poor semen quality, low egg production, and poor fertility and hatchability rates). From an economic perspective, it is a necessity of improve these reproductive traits. Studies have demonstrated that the essential trace element-selenium-plays key roles in testicular development and the maintenance of spermatogenesis. The aim of the present study was to determine the effect of feed supplementation with organic selenium and vitamin E on ganders' response to manual semen collection and semen quality. Sixteen 3-year-old White Koluda ganders were randomly divided into two groups. The control group was provided commercial feed while the experimental group was provided with the same commercial feed supplemented with selenium (0.3 mg/kg) and vitamin E (100 mg/kg). The response of individual ganders from both groups to manual semen collection and the quality of the semen collected were evaluated. The supplements increased (P???0.05) the frequency and decreased the time interval of a complete ejaculatory response of the ganders to manual semen collections (82.7 % supplement vs. 73.5 % control). Males from the supplemented group had significantly higher (P???0.01; P???0.05) ejaculate volumes, sperm concentrations, and percentages of viable sperm and lower percentages of immature sperm (spermatids). Lipids peroxidation, expressed in terms of the malondialdehyde concentration, was lower (P???0.01) in semen of the supplemented group (0.172 nmol/50?×?10(6)) as compared to the controls (0.320 nmol/50?×?10(6)). Moreover, the duration of the reproductive period of the ganders in the experimental group was 1 week longer. The results show that supplemental dietary selenium and vitamin E improved both the ganders' response to manual semen collection and semen quality. We conclude that such feed supplementation could lead to greater economic benefits through increased reproductive efficiency within the goose production industry. PMID:23584843

Jerysz, Anna; Lukaszewicz, Ewa

2013-06-01

423

Characteristics of Haemophilus influenzae Type b Responsible for Meningitis in Poland from 1997 to 2004  

Microsoft Academic Search

Two hundred forty-five H. influenzae isolates responsible for meningitis in Poland from 1997 to 2004 were studied. Among these, 233 (95.1%) belonged to serotype b (Hib), 2 belonged to serotype f, and 10 were noncapsulated. The relatedness of all isolates was evaluated by pulsed-field gel electrophoresis (PFGE), and selected representatives were evaluated by multilocus sequence typing. Resistance to ampicillin was

Anna Skoczynska; Marcin Kadøubowski; Joanna Empel; Waleria Hryniewicz

424

Vibrational relaxation of anharmonic oscillators in expanding flows  

NASA Technical Reports Server (NTRS)

Although the Landau-Teller vibrational model accurately predicts vibrational excitation process in post-shock and compressing flows, it under-predicts the rate of de-excitation in cooling and expanding flows. In the present paper, detailed calculations of the vibrational relaxation process of N2 and CO in cooling flows are conducted. A coupled set of vibrational transition rate equations and quasi-one-dimensional fluid dynamic equations is solved. Multiple quantum level transition rates are computed using SSH theory. The SSH transition rate results are compared with available experimental data and other theoretical models. Vibration-vibration exchange collisions are responsible for some vibrational relaxation acceleration in situations of high vibrational temperature and low translational temperature. The present results support the relaxation mechanisms proposed by Bray and by Treanor Rich and Rehm.

Ruffin, Stephen M.; Park, Chul

1992-01-01

425