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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

Effects of Vibration Stress and Temperature on the Characteristics of Piezoelectric Ceramics under High Vibration Amplitude Levels Measured by Electrical Transient Responses  

Microsoft Academic Search

This paper presents a characteristic evaluation of piezoelectric ceramics at high vibration amplitude levels of resonance, based on the electrical transient response technique. Low-Q and high-Q materials are measured, and the effect of vibration stress is obtained without affecting temperature. It is revealed that for low-Q materials an increase of loss is caused mainly by the vibration stress, while for

Mikio Umeda; Kentaro Nakamura; Sadayuki Ueha

1999-01-01

3

Response characteristics of rain-wind induced vibration of stay-cables of cable-stayed bridges  

Microsoft Academic Search

This paper aims to investigate the various response characteristics of “rain-wind induced vibration” of cables and its fundamental mechanism. A series of wind tunnel tests has indicated that rain-wind induced vibration of cables can be classified into three types, that is a “galloping” type, which includes both divergent galloping and velocity restricted galloping, related to a negative slope of the

Masaru Matsumoto; Tohru Saitoh; Masahiko Kitazawa; Hiromichi Shirato; Takayuki Nishizaki

1995-01-01

4

Vibration Characteristics of Thermoplastic Composite  

NASA Astrophysics Data System (ADS)

Unreinforced, Long fiber and Short fiber polypropylene composites are being used in many antivibration applications, due to their time and temperature dependent specific mechanical properties. Their good damping behavior accounts for many engineering applications. For utilization of these materials in specific engineering applications, there is a need to understand the damping behavior of composites under dynamic load. For this work, unreinforced and 20% long and short reinforced glass fiber polypropylene composite materials were tested for forced transverse vibration damping characteristics under static as well as fatigue loading conditions. The damping characteristics are quantified by forced frequency response of the test material. Presence of reinforced fibers increases the damping capacity. Among reinforcements, short fiber reinforced polypropylene shows increased damping capacity then long glass fiber reinforced.

Haldar, Amit Kumar; Singh, Satnam; Prince, Prince

2011-12-01

5

Vibration, performance, flutter and forced response characteristics of a large-scale propfan and its aeroelastic model  

NASA Technical Reports Server (NTRS)

An investigation of the vibration, performance, flutter, and forced response of the large-scale propfan, SR7L, and its aeroelastic model, SR7A, has been performed by applying available structural and aeroelastic analytical codes and then correlating measured and calculated results. Finite element models of the blades were used to obtain modal frequencies, displacements, stresses and strains. These values were then used in conjunction with a 3-D, unsteady, lifting surface aerodynamic theory for the subsequent aeroelastic analyses of the blades. The agreement between measured and calculated frequencies and mode shapes for both models is very good. Calculated power coefficients correlate well with those measured for low advance ratios. Flutter results show that both propfans are stable at their respective design points. There is also good agreement between calculated and measured blade vibratory strains due to excitation resulting from yawed flow for the SR7A propfan. The similarity of structural and aeroelastic results show that the SR7A propfan simulates the SR7L characteristics.

August, Richard; Kaza, Krishna Rao V.

1988-01-01

6

Vibration characteristics of electrorheological elastomer sandwich beams  

NASA Astrophysics Data System (ADS)

The vibration characteristics and control capabilities of a cantilever sandwich beam with electrorheological (ER) elastomers subjected to different electric fields are investigated in this study. Considering ER elastomers as viscoelastic damping materials with electrically controllable properties, a finite element model of a sandwich beam with an ER elastomer core is developed to predict the vibration responses of the proposed beam. An experimental analysis was also conducted to illustrate and evaluate the effects of an electric field on the frequency responses and natural frequencies of the sandwich beam. The results show that natural frequencies of the ER elastomer sandwich beam increase and vibration amplitudes at natural frequencies of the ER elastomer beam decrease, as the strength of the applied electric field increases. It is demonstrated that the vibration characteristics of ER elastomer beams are similar to those of ER fluid beams, which could be controlled by changing the strength of the applied electric field. This controllable characteristic of ER elastomer beams is useful for applications in engineering structures where variable performance is desired.

Wei, Kexiang; Bai, Quan; Meng, Guang; Ye, Lin

2011-05-01

7

Investigation of vibration characteristics of electric motors  

NASA Technical Reports Server (NTRS)

The vibration characteristics of electric motors were analyzed using mathematical statistics methods. The equipment used and the method of conducting the test are described. Curves are developed to show the visualization of the electric motor vibrations in the vertical direction. Additional curves are included to show the amplitude-phase frequency characteristic of dynamic rotor-housing vibrations at the first lug and the same data for the second lug of the electric motor. Mathematical models were created to show the transmission function of the dynamic rotor housing system.

Bakshis, A. K.; Tamoshyunas, Y. K.

1973-01-01

8

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

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 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

11

Experimental Study of the Vibration Characteristics of Railroad Ties  

NASA Astrophysics Data System (ADS)

Vibration characteristics of railroad ties are investigated by the method of shock excitation. The feasibility of estimating the quality of railroad tracks from the harmonic analysis of these vibrations is demonstrated.

Vasil'Ev, N. A.; Dvornikov, S. I.

2000-05-01

12

Vibration characteristics about thermal variation of BFP in power plant  

NASA Astrophysics Data System (ADS)

BFPs(Boiler Feedwater Pump) in power plants are used for pumping high pressure and high temperature water. The pressure pulsation of high pressure pumps is the vibration caused by fluid forces. If the frequency of the exciting source is adjacent to one of the natural frequencies of the pump, it can cause high vibration by resonance. The natural vibration characteristics of pump depend on thermal variation. This paper examines vibration characteristics due to thermal variation experimentally and analytically.

Song, A. H.; Song, J. D.; Kim, H. S.; Jung, G. C.

2012-11-01

13

Natural vibration characteristics of gravity structures  

Microsoft Academic Search

A forced vibration procedure is presented to estimate fundamental and higher frequencies of vibrations and associated mode shapes of gravity structures. The gravity structures considered are retaining walls and gravity dams. The validity of the proposed procedure is tested on three test problems of varying complexity for which the natural vibration frequencies and mode shapes either have known analytical solutions

Ashok K. Chugh

2007-01-01

14

Free Vibration Characteristics of Hybrid SPR Beams  

NASA Astrophysics Data System (ADS)

This paper deals with torsional free vibration analysis of single lap-jointed encastre hybrid SPR beams. The finite element analyses are carried out using the commercially-available ANSYS FEA program. The focus of the analysis is to reveal the influence on the natural frequencies, natural frequency ratios and mode shapes of single lap-jointed encastre hybrid SPR beams caused by variations in the material properties of the adhesives. Numerical examples show that the torsional natural frequencies of single lap jointed encastre hybrid SPR beams increase significantly as the Young's modulus of the adhesive increase, but only slight change with an increase in Poisson's ratio. The mode shapes show that there are different deformations in the jointed section of the odd and even modes. These different deformations may result different dynamic response and different stress distributions.

He, Xiaocong; Dong, Biao; Zhu, Xunzhi

2010-05-01

15

Free Vibration Characteristics of Thermally Loaded Cylindrical Shell  

Microsoft Academic Search

\\u000a The variations of the structural vibration characteristics such as the natural frequency, damping, and mode shape can be observed\\u000a under thermal loading conditions. Therefore, the free vibration characteristic of a thermally loaded cylindrical shell was\\u000a analyzed in this study. ABAQUS was used for the analysis and a thermo-elastic experimental modal test was conducted. Configuration\\u000a of the shell is 5 m

Byung-Hee Jeon; Hui-Won Kang; Young-Shin Lee

16

Mounting method improves electrical and vibrational characteristics of screen electrodes  

NASA Technical Reports Server (NTRS)

Electrical characteristics of the mesh or screen electrodes used in electron tubes are improved by decreasing the shunt capacitance of the tube while retaining the close spacing needed for the required resolution. Vibrational characteristics are enhanced by raising the natural resonant frequency.

Nelson, R. E.

1969-01-01

17

Scale-model characterization of flow-induced vibrational response of FFTF reactor internals  

SciTech Connect

Fast Test Reactor core internal and peripheral components were assessed for flow-induced vibrational characteristics under scaled and simulated prototype flow conditions in the Hydraulic Core Mockup as an integral part of the Fast Test Reactor Vibration Program. The Hydraulic Core Mockup was an 0.285 geometric scale model of the Fast Test Reactor internals designed to simulate prototype vibrational and hydraulic characteristics. Using water to simulate sodium coolant, vibrational characteristics were measured and determined for selected model components over the scaled flow range of 36 to 110%. Additionally, in-situ shaker tests were conducted on selected Hydraulic Core Mockup outlet plenum components to establish modal characteristics. Most components exhibited resonant response at all test flow rates; however, the measured dynamic response was neither abnormal nor anomalously flow-rate dependent, and the predicted prototype components' response were deemed acceptable.

Ryan, J. A.; Mahoney, J. J.

1980-10-01

18

Vertical Vibration Characteristics of a High-Temperature Superconducting Maglev Vehicle System  

NASA Astrophysics Data System (ADS)

The vertical vibration characteristics of a high-temperature superconducting maglev vehicle system are investigated experimentally. The displacement variations of the maglev vehicle system are measured with different external excitation frequency, in the case of a certain levitation gap. When the external vibration frequency is low, the amplitude variations of the response curve are small. With the increase of the vibration frequency, chaos status can be found. The resonance frequencies with difference levitation gap are also investigated, while the external excitation frequency range is 0-100 Hz. Along with the different levitation gap, resonance frequency is also different. There almost is a linear relationship between the levitation gap and the resonance frequency.

Jiang, Jing; Li, Ke Cai; Zhao, Li Feng; Ma, Jia Qing; Zhang, Yong; Zhao, Yong

2013-06-01

19

Mechanical characteristics of strained vibrating strings and a vibration-induced electric field  

NASA Astrophysics Data System (ADS)

The mechanical characteristics of vibrating strings strained between rigid supports and a vibration-induced electric field are studied. Experiments are conducted with nylon, rubber, and metallic strings. Vibrations are excited by a pinch at different sites along the string. The motion of the string is filmed, and the attendant electric field is detected. Experimental data are analyzed under the assumption that the field is induced by unlike charges generated by the moving string. It is found that the field allows one to determine the time characteristics of the motion of the string and discriminate the types of its deformations. Young moduli observed under the static extension of thin nylon strings are compared with those calculated from the natural frequencies of vibration measured for differently strained strings. The mathematical pattern of the motion of the string is compared with the real situation.

Bivin, Yu. K.

2012-11-01

20

Vibrational characteristic features and band intensities in solving two-dimensional inverse vibrational problems  

NASA Astrophysics Data System (ADS)

An iterative approach to solving the inverse vibrational problem is used for two-dimensional molecular force field species and all their multiple solutions are obtained. Two methods, one of isotopic molecular force constant invariance and another of differential increments of the force constants, are applied to methane, silane, germane, stannane, ammonia, phosphine, arsine, stibine and their deuterium isotopes, as well as to tetrafluoromethane and its carbon-13 isotope, Criteria for physical significance of each solution based on the characteristic features of the normal vibrations are utilized in discriminating between the multiple solutions. The vibrational intensities are used in an attempt to determine the sign combination for the dipole moment derivatives with respect to the normal coordinates. The force constant results agree very well with those obtained by the parametric approach to the two-dimensional inverse vibrational problem solved for the same molecules [B.M. Nikolova, J. Mol. Struct., 291 (1993) 123].

Nikolova, B. M.

1993-10-01

21

Vibration characteristics of brass instrument bells  

NASA Astrophysics Data System (ADS)

Finite element techniques are used to study the mode frequencies and shapes of trombone bells. The responses of the modes to acoustic excitation are calculated and general response levels presented. Quantitative experimental determinations of acoustically excited modes are rare but a comparison is made with one set of measurements with general agreement.

Watkinson, P. S.; Bowsher, J. M.

1982-11-01

22

Vibration characteristics of ultrasonic scalers assessed with scanning laser vibrometry  

Microsoft Academic Search

Objectives. Scanning laser vibrometry is a non-invasive method of accurately measuring the vibratory characteristics of oscillating objects. The aim of this study was to observe, using a scanning laser vibrometer (SLV), the vibration patterns of dental ultrasonic scaler tips and to assess the effects of water flow rate and power setting on these patterns whilst operating the tips in an

S. C Lea; G Landini; A. D Walmsley

2002-01-01

23

Vibration damping characteristics of laminated steel sheet  

NASA Astrophysics Data System (ADS)

The use of laminated steel sheets as vibration damping materials was studied. The laminate consisted of a viscoelastic layer which was sandwiched between two steel sheets. The study sought to identify parameters affecting the damping efficiency of the laminate. Two viscoelastic materials, a copolymer based on ethylene and acrylic acid (PEAA) and polyvinyl butyral (PVB), were used. A frequency analyzer was used to measure the loss factor of the laminates. A theoretical analysis of damping efficiency based on a model described by Ungar[2] was also carried out. The results showed that the loss factor of the PEAA-based laminates increased monotonically with increasing thickness of the viscoelastic layer and leveled off at 25.9 pct of total thickness. Ungar’s theory predicted a higher loss factor than the experimental data. This might have resulted from interfacial adhesive bonding, a nonuniform viscoelastic layer thickness, and the extrapolation of the rheological data from low to high frequencies. The loss factor of the laminate increased with increasing temperature, reached a maximum value, and then decreased. An optimum temperature for maximum damping was found for each laminate configuration. The PEAA-based laminates possessed higher damping efficiency than the PVB-based laminates at room temperature. The symmetric laminate (with the same steel sheet thickness) possessed a better damping efficiency than asymmetric laminates. The maximum damping peak of the laminates using a polymer blend, when compared to the laminates using unblended resin, exhibited a lower loss factor value, became broader, and occurred at a temperature between the T g’s of the individual components of the polymer blend.

Chen, Y. S.; Hsu, T. J.; Chen, S. I.

1991-03-01

24

Vibration characteristics on a wind turbine rotor using modal and harmonic analysis of FEM  

Microsoft Academic Search

A wind turbine rotor system containing blades has its own characteristics. The vibration characteristics of blades with special airfoil can influence the vibration characteristics of the rotor system. This paper analyzed the vibration characteristics of a wind turbine rotor including blades with two-dimensional airfoil. The Finite Element Method (FEM) is applied to establish the rotor model, with the purpose that

Chao Liu; Dongxiang Jiang; Jie Chen

2010-01-01

25

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

26

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

27

Vibration and noise characteristics of flap type olive harvesters.  

PubMed

The object of this study was to measure and evaluate the vibration and noise characteristics of five flap type portable harvesters using for olive harvesting and their effect on operator health during harvesting time. The vibration and sound pressure levels of different harvesters were measured at both idling and full load conditions. The vibration values of harvesters were measured and analyzed for both right and left hands and the sound pressure level was measured at ear level of the operator. The vibration total value was expressed as the root-mean-squares (rms) of three component values. The results indicated that in 10% of the exposed population traumatic vasospastic disease (TVD) appeared after 0.7-7.1 years for the left hand, 1.0-4.7 years for the right hand of the operator in continuous use of these harvesters, under usual working conditions. The sound pressure values at operator's ear level of harvesters were found below risk levels when compared with ILO standards. PMID:20869693

Cakmak, Bülent; Saraço?lu, Türker; Alayunt, Fazilet N; Ozarslan, Cengiz

2011-03-01

28

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

PubMed Central

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 (r 2=0.91) and between the resonant frequency and stiffness factor (r 2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested.

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

2005-01-01

29

Electrical Response to Vibration of a Lipid Bilayer Membrane  

PubMed Central

The discovery and characterization of a vibration response in a black lipid bilayer membrane is the topic of this paper. An electrical vibration response is obtained when the membrane is under voltage clamp and a weaker, but significant, response is obtained under current clamp. The effect arises from an induced variation in the membrane capacitance. It is further shown that the capacitance variation arises from a change in the membrane area as the membrane undergoes drumhead vibration. Possible physiological significance in mechanoreception is discussed. ImagesFIGURE 1

Ochs, Alfred L.; Burton, Robert M.

1974-01-01

30

Responses of motor cortical cells to short trains of vibration.  

PubMed

The response discharges of precentral motor cortical cells to brief trains of vibration applied to the tendon of biceps brachii were analyzed in two alert but passive monkeys. The activity of 20 phasic-tonic and 6 tonic cells was analyzed. All had functional linkages with flexor muscles during a preceding flexion task and responded to passive movement of the elbow. Taking as a reference the stereotyped reflex response in the stretched muscle, the effect of changes in the amplitude of a constant frequency vibration (4 vibrations at 58 Hz) was quantified statistically in peristimulus histograms of the cortical cell discharges. All cells were transiently influenced by low vibration amplitudes. Most responses (71%) were excitatory and occurred at a mean latency of 24 ms, which is consistent with cells activated by input from stretch receptors. Excitatory, reproducible responses to the lowest vibration amplitudes were more frequent in phasic-tonic than in pure tonic cells. Large-amplitude vibrations always excited the motor cortical cells. The sign of the responses to vibration matched that to passive elbow movements for most cells. These findings show that elbow-related motor cortical cells are very sensitive to proprioceptive input from primary spindle afferents. PMID:8891651

Fourment, A; Chennevelle, J M; Belhaj-Saïf, A; Maton, B

1996-09-01

31

Antagonist motor responses correlate with kinesthetic illusions induced by tendon vibration.  

PubMed

In humans, vibration applied to muscle tendons evokes illusory sensations of movement that are usually associated with an excitatory tonic response in muscles antagonistic to those vibrated (antagonist vibratory response or AVR). The aim of the present study was to investigate the neurophysiological mechanisms underlying such a motor response. For that purpose, we analyzed the relationships between the parameters of the tendon vibration (anatomical site and frequency) and those of the illusory movement perceived (direction and velocity), as well as the temporal, spatial, and quantitative characteristics of the corresponding AVRs (i.e., surface EMG, motor unit firing rates and activation latencies). Analogies were supposed between the characteristics of AVRs and voluntary contractions. The parameters of the AVR were thus compared with those of a voluntary contraction with similar temporal and mechanical characteristics, involving the same muscle groups as those activated by vibration. Wrist flexor muscles were vibrated either separately or simultaneously with wrist extensor muscles at frequencies between 30 and 80 Hz. The illusory movement sensations were quantified through contralateral hand-tracking movements. Electromyographic activity from the extensor carpi radialis muscles was recorded with surface and intramuscular microelectrodes. The results showed that vibration of the wrist flexor muscle group induced both a kinesthetic illusion of wrist extension and a motor response in the extensor carpi radialis muscles. Combined vibration of the two antagonistic muscle groups at the same frequency evoked neither kinesthetic illusion nor motor activity. In addition, vibrating the same two antagonistic muscle groups at different frequencies induced both a kinesthetic illusion and a motor response in the muscle vibrated at the lowest frequency. The surface EMG amplitude of the extensor carpi radialis as well as the motor unit activation latency and discharge frequency were clearly correlated to the parameters of the illusory movement evoked by the vibration. Indeed, the faster the illusory sensation of movement, the greater the surface EMG in these muscles during the AVRs and the sooner and the more intense the activation of the motor units of the wrist extensor muscles. Moreover, comparison of the AVR with voluntary contraction showed that all parameters were highly similar. Mainly slow motor units were recruited during the AVR and during its voluntary reproduction. That the AVR is observed only when a kinesthetic illusion is evoked, together with the similarities between voluntary contractions and AVRs, suggests that this vibration-induced motor response may result from a perceptual-to-motor transformation of proprioceptive information, rather than from spinal reflex mechanisms. PMID:9989440

Calvin-Figuière, S; Romaiguère, P; Gilhodes, J C; Roll, J P

1999-02-01

32

Flow-induced vibration characteristics of BWR/6 jet pumps  

SciTech Connect

Two General Electric boiling water reactor jet pumps, a BWR/6 and a BWR/6-218, were tested for flow-induced vibration (FIV) characteristics in the Large Steam Water Test Facility at Moss Landing, CA, during February and March 1978. Tests were conducted at normal reactor operating conditions (532/sup 0/F, 1046 psia and prototypical flow rates) and a variety of off-design conditions. Both jet pumps exhibited acceptable, low level, random FIV characteristics at normal reactor operating conditions. Both jet pumps exhibited similar high level, periodic FIV characteristics at off-design operating conditions. For both jet pumps, the transition from low to high-level FIV was a monotonic, reversible, function of the slip-joint differential pressure (SJDP). Both jet pumps sustained damage due to operation at high-level FIV.

LaCroix, L.V.

1982-09-01

33

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.

34

Vibration characteristics of a rotating flexible arm with ACLD treatment  

NASA Astrophysics Data System (ADS)

In this paper, the vibration behavior and control of a clamped-free rotating flexible cantilever arm with fully covered active constrained layer damping (ACLD) treatment are investigated. The arm is rotating in a horizontal plane in which the gravitational effect and rotary inertia are neglected. The stress-strain relationship for the viscoelastic material (VEM) is described by a complex shear modulus while the shear deformations in the two piezoelectric layers are neglected. Hamilton's principle in conjunction with finite element method (FEM) is used to derive the non-linear coupled differential equations of motion and the associated boundary conditions that describe the rigid hub angle rotation, the arm transverse displacement and the axial deformations of the three-layer composite. This refined model takes into account the effects of centrifugal stiffening due to the rotation of the beam and the potential energies of the VEM due to extension and bending. Active controllers are designed with PD for the piezosensor and actuator. The vibration frequencies and damping factors of the closed-loop beam/ACLD system are obtained after solving the characteristic complex eigenvalue problem numerically. The effects of different rotating speed, thickness ratio and loss factor of the VEM as well as different controller gain on the damped frequency and damping ratio are presented. The results of this study will be useful in the design of adaptive and smart structures for vibration suppression and control in rotating structures such as rotorcraft blades or robotic arms.

Fung, E. H. K.; Yau, D. T. W.

2004-01-01

35

Vibration transmissibility characteristics of the human hand-arm system under different postures, hand forces and excitation levels  

NASA Astrophysics Data System (ADS)

Biodynamic responses of the hand-arm system have been mostly characterized in terms of driving-point force-motion relationships, which have also served as the primary basis for developing the mechanical-equivalent models. The knowledge of localized vibration responses of the hand-arm segments could help derive more effective biodynamic models. In this study, the transmission of z h-axis handle vibration to the wrist, elbow and the shoulder of the human hand and arm are characterized in the laboratory for the bent-arm and extended arm postures. The experiments involved six subjects grasping a handle subject to two different magnitudes of broad-band random vibration, and nine different combinations of hand grip and push forces. The vibration transmissibility data were acquired in the z h- and y h-axis at the wrist and shoulder, and along all the three axes around the elbow joint. The results show that the human hand-arm system in an extended arm posture amplifies the vibration transmitted to the upper-arm and the whole-body at frequencies below 25 Hz, but attenuates the vibration above 25 Hz more effectively than the bent-arm posture, except at the shoulder. The magnitudes of transmitted vibration under an extended arm posture along the y h-axis were observed to be nearly twice those for the bent-arm posture in the low frequency region. The results further showed that variations in the grip force mostly affect vibration transmissibility and characteristic frequencies of the forearm, while changes in the push force influenced the dynamic characteristics of the entire hand-arm system. The magnitudes of transmitted vibration in the vicinity of the characteristic frequencies were influenced by the handle vibration magnitude.

Adewusi, S. A.; Rakheja, S.; Marcotte, P.; Boutin, J.

2010-07-01

36

Synthesis of a system with active vibration isolation, considering the vibroacoustical characteristics of the source and of the isolated object  

NASA Technical Reports Server (NTRS)

The efficiency and resistance of an active vibration isolation system (AVI) are analyzed for the case of unidirectional vibrations of a mass on a spring, with a damper, resting on a rigid base. The effect of certain vibroacoustical characteristics of real objects on AVI resistance and synthesis of AVI, which are effective over a wide frequency band are considered. A numerical analysis of the response of a mechanical system with AVI features is presented.

Genkin, M. D.; Yelezov, V. G.; Yablonskiy, V. V.

1973-01-01

37

Response of the seated human body to whole-body vertical vibration: biodynamic responses to sinusoidal and random vibration.  

PubMed

The dependence of biodynamic responses of the seated human body on the frequency, magnitude and waveform of vertical vibration has been studied in 20 males and 20 females. With sinusoidal vibration (13 frequencies from 1 to 16 Hz) at five magnitudes (0.1-1.6 ms(-2) r.m.s.) and with random vibration (1-16 Hz) at the same magnitudes, the apparent mass of the body was similar with random and sinusoidal vibration of the same overall magnitude. With increasing magnitude of vibration, the stiffness and damping of a model fitted to the apparent mass reduced and the resonance frequency decreased (from 6.5 to 4.5 Hz). Male and female subjects had similar apparent mass (after adjusting for subject weight) and a similar principal resonance frequency with both random and sinusoidal vibration. The change in biodynamic response with increasing vibration magnitude depends on the frequency of the vibration excitation, but is similar with sinusoidal and random excitation. PMID:24730687

Zhou, Zhen; Griffin, Michael J

2014-01-01

38

Effects of sitting postures on biodynamic response of seated occupants under vertical vibration  

Microsoft Academic Search

The biodynamic response characteristics of 13 male and 14 female seated subjects, exposed to vertical vibration, are characterized under different postural conditions. The measurements are performed for a total of 36 different sitting postural configurations realized through variations in hands position (in lap and on steering wheel), three seat heights (510, 460 and 410mm), and seat design factors involving two

W. Wang; S. Rakheja; P.-É. Boileau

2004-01-01

39

Thermoregulatory responses to heat and vibration in men  

NASA Technical Reports Server (NTRS)

The effect of vibration on thermoregulatory responses was studied in heat-acclimated men exposed suddenly to simultaneous heat and whole body vibrations (WBVs) at two intensity levels, each at graded frequencies between 5 and 80 Hz. The mean rectal temperature (Tre) became elevated more quickly in the WBV exposures than in the controls (heat exposure alone). Both intensity- and frequency-dependent WBV relationships were recorded in localized blood flows and in sweat rates. Thus, vibration appears to reduce the efficiency of the cooling mechanisms during a heat exposure.

Spaul, W. A.; Spear, R. C.; Greenleaf, J. E.

1986-01-01

40

Characteristics of large capacity ultrasonic complex vibration sources with stepped complex transverse vibration rods  

Microsoft Academic Search

Configurations of large capacity ultrasonic complex vibration sources with multiple longitudinal transducers are proposed and studied. The ultrasonic complex vibration systems are effective and essential for new applications in various industries. The complex vibration source of 27 kHz consists of a complex transverse rod with a welding tip (aluminum alloy, stainless steel and titanium alloy), a complex vibration rod with

J. Tsujino; T. Ueoka

2004-01-01

41

Characteristics of coated copper wire specimens using high frequency ultrasonic complex vibration welding equipments.  

PubMed

Welding characteristic of thin coated copper wires were studied using 40, 60, 100 kHz ultrasonic complex vibration welding equipments with elliptical to circular vibration locus. The complex vibration systems consisted of a longitudinal-torsional vibration converter and a driving longitudinal vibration system. Polyurethane coated copper wires of 0.036 mm outer diameter and copper plates of 0.3 mm thickness and the other dimension wires were used as welding specimens. The copper wire part is completely welded on the copper substrate and the insulated coating material is driven from welded area to outsides of the wire specimens by high frequency complex vibration. PMID:15047272

Tsujino, J; Ihara, S; Harada, Y; Kasahara, K; Sakamaki, N

2004-04-01

42

Experimental Investigations on Effect of Damage on Vibration Characteristics of a Reinforced Concrete Beam  

NASA Astrophysics Data System (ADS)

Need for developing efficient non-destructive damage assessment procedures for civil engineering structures is growing rapidly towards structural health assessment and management of existing structures. Damage assessment of structures by monitoring changes in the dynamic properties or response of the structure has received considerable attention in recent years. In the present study, damage assessment studies have been carried out on a reinforced concrete beam by evaluating the changes in vibration characteristics with the changes in damage levels. Structural damage is introduced by static load applied through a hydraulic jack. After each stage of damage, vibration testing is performed and system parameters were evaluated from the measured acceleration and displacement responses. Reduction in fundamental frequencies in first three modes is observed for different levels of damage. It is found that a consistent decrease in fundamental frequency with increase in damage magnitude is noted. The beam is numerically simulated and found that the vibration characteristics obtained from the measured data are in close agreement with the numerical data.

Srinivas, V.; Jeyasehar, C. Antony; Ramanjaneyulu, K.; Sasmal, Saptarshi

2012-02-01

43

Bridge Condition Assessment based on Vibration Responses of Passenger Vehicle  

NASA Astrophysics Data System (ADS)

In this paper, we propose a new method of assessing the condition of existing short- and medium-span reinforced/prestressed concrete bridges based on vibration monitoring data obtained from a public bus. This paper not only describes details of a prototype monitoring system that uses information technology and sensors capable of providing more accurate knowledge of bridge performance than conventional ways but also shows a few specific examples of bridge condition assessment based on vehicle vibrations measured by using an in-service public bus equipped with vibration measurement instrumentation. This paper also describes a sensitivity analysis of deteriorating bridges based on simulation of the acceleration response of buses conducted by the "substructure method" employing a finite element model to verify the above bridge performance results. The main conclusions obtained in this study can be summarized as follows: (1) Because the vibration responses of passenger vehicles, such as buses, have a good linear relationship with the vibration responses of the target bridges, the proposed system can be used as a practical monitoring system for bridge condition assessment. (2) The results of sensitivity analysis performed by the substructure method show that bus vibration responses are useful for evaluating target bridge performance. (3) The proposed method was applied to a network of real bridges in a local area to evaluate its effectiveness. The results indicate that the proposed method can be used to prioritize the repair/strengthening works of existing bridges based on various vibration information in order to help bridge administrators establish rational maintenance strategies.

Miyamoto, Ayaho; Yabe, Akito

2011-07-01

44

Sensitivity analysis of torsional vibration characteristics of helicopter rotor blades. Part 2: Aerodynamics and sensitivity analysis  

NASA Technical Reports Server (NTRS)

A theoretical investigation of dynamic response characteristics of rotor blades was carried out with special emphasis on torsional degrees-of-freedom. Coupled equations of motion for flapwise bending and torsion were formulated at varying azimuth positions for rotor blades with noncollinear aerodynamic, elastic and mass axes. Both structural and aerodynamic mass, damping and stiffness coefficients were included. The variations of a sample blade at different flight conditions were investigated from these equations. The obtained numerical results were illustrated. The sensitivity of overall blade vibration characteristics to torsional oscillations was also investigated from the equations of motion for the sample blade. The illustrated results show the importance of torsional degrees-of-freedom in rotor blade analysis. Various possibilities of improving the overall response by tuning blade geometric, structural and aerodynamic characteristics are discussed.

Bratanow, T.; Ecer, A.

1974-01-01

45

Investigation of the Vibration Characteristics of the Eurocopter AS35OB Main Rotor Gearbox Under Different Operating Conditions.  

National Technical Information Service (NTIS)

Different flight conditions can introduce complex changes to the vibration of helicopter transmissions, which may cause a vibration-based in- flight transmission diagnostic system to produce false alarms. An investigation into the vibration characteristic...

W. Wang

2001-01-01

46

An optimized semiclassical approximation for vibrational response functions  

NASA Astrophysics Data System (ADS)

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.

Gerace, Mallory; Loring, Roger F.

2013-03-01

47

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.

Gerace, Mallory; Loring, Roger F.

2013-01-01

48

Basic characteristics of the linear synchronous generator using mechanical vibration  

Microsoft Academic Search

The liner synchronous generator system is developed. In most of vehicles, vibration occurs. Mechanical vibration of the vehicle is absorbed by mechanical dampers and other facilities, so this energy is consumed wastefully. Using the linear generator, energy of vibration is converted to electrical energy. Also, this generator works as an active damper. The experimental device has been developed. The method

Shunsuke Ohashi; Tatsuro Matsuzuka

2005-01-01

49

Vibration Testing Based on Impulse Response Excited by Pulsed-Laser Ablation: Measurement of Frequency Response Function with Detection-Free Input  

Microsoft Academic Search

We have developed a non-contact vibration-measurement system that is based on impulse excitation by laser ablation (i.e. laser excitation) to measure the high-frequency-vibration characteristics of objects. The proposed method makes it possible to analyse the frequency response function just by measuring the output (acceleration response) of a test object excited by pulsed-laser ablation. This technique does not require detection of

Naoki Hosoya; Itsuro Kajiwara; Takahiko Hosokawa

50

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

51

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

52

Characteristics of Hole Machining of Brittle Material by Ultrasonic Complex Vibration  

NASA Astrophysics Data System (ADS)

A new method using a polishing slurry together with ultrasonic longitudinal and torsional vibrations from a source with a diagonal slit vibration converter is developed for the hole machining of brittle materials. We predict that removal rate and machining accuracy will be improved using ultrasonic longitudinal--torsional vibration when compared with using conventional longitudinal vibration machining. In experiments, soda-lime glass is used as the processing material, and hole roundness error and machining time are measured to assess the hole machining characteristics. We find that machining accuracy is improved using ultrasonic longitudinal--torsional vibration.

Asami, Takuya; Miura, Hikaru

2012-07-01

53

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

54

Vibration characteristics of a discal piezoelectric transducer with spiral interdigitated electrodes  

NASA Astrophysics Data System (ADS)

Torsional vibrations of circular tubes, rods, rings, and disks are widely used as operation modes of acoustic wave transducers in various piezoelectric devices. In this paper, a piezoelectric disk with spiral interdigitated electrodes is proposed to generate in-plane torsion in a simple and effective manner. Design and working principle of the torsional transducer are introduced. Vibration characteristics of the transducer with a constant spiral angle are studied. A simplified model is established to investigate the basic dynamic characteristics of torsional vibration accompanying with radial vibration. Electric admittance, resonant frequencies, and mode shapes with different boundary conditions are calculated. Resonant frequencies as functions of several structural parameters are discussed.

Pan, Chengliang; Liao, Wei-Hsin; Liu, Yongbin; Feng, Zhihua

2014-03-01

55

Measuring vibration characteristics at large amplitude region of materials for high power ultrasonic vibration system  

PubMed

This study proposes a method of estimating the mechanical quality factor of materials for high-power ultrasonic vibration systems under large vibration amplitude conditions. The quality factors of several metals as well as some polymers are measured by this method. In this method, the quality factor is calculated as the ratio of the reactive energy stored in a specimen to the dissipated energy. The dissipated energy is estimated from the input/output mechanical energy to the specimen by measurement of the vibration intensity, while the reactive energy is measured as the kinetic energy of the vibration. Then, the quality factor for the specified part can be extracted using this method. In this report, quality factors for torsional vibration were measured at about 30 kHz as functions of the vibration strain. PMID:10829642

Nakamura; Kakihara; Kawakami; Ueha

2000-03-01

56

Vibration characteristic analysis method for the quartz microgyroscope based on the admittance circle  

NASA Astrophysics Data System (ADS)

The vibration characteristic analysis method for a quartz microgyroscope based on the admittance circle is reported in this paper. Admittance theory is introduced and the admittance circle principle is analysed to study the vibration characteristics of the quartz microgyroscope. The prototype gyroscope was fabricated by micro-electromechanical systems (MEMS) technology. The admittance and phase diagram of the work mode were obtained by vibration mode test systems. Then the admittance circle of the work mode was drawn, and the parameter identification of the transfer function between the voltage and current was completed to analyse the vibration characteristics. Therefore, the vibration characteristic analysis method based on the admittance circle can be used to build the transfer function of the quartz microgyroscope, which is helpful for the design of a high performance quartz microgyroscope.

Wang, Haoxu; Dong, Peitao; Xie, Liqiang; Wu, Xuezhong

2014-03-01

57

Semiclassical nonlinear response functions for coupled anharmonic vibrations  

SciTech Connect

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.

Gruenbaum, Scott M.; Loring, Roger F. [Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853 (United States)

2009-11-28

58

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

59

The response of rotating machinery to external random vibration  

NASA Technical Reports Server (NTRS)

A high-speed turbogenerator employing gas-lubricated hydrodynamic journal and thrust bearings was subjected to external random vibrations for the purpose of assessing bearing performance in a dynamic environment. The pivoted-pad type journal bearings and the step-sector thrust bearing supported a turbine-driven rotor weighing approximately twenty-one pounds at a nominal operating speed of 36,000 rpm. The response amplitudes of both the rigid-supported and flexible-supported bearing pads, the gimballed thrust bearing, and the rotor relative to the machine casing were measured with capacitance type displacement probes. Random vibrations were applied by means of a large electrodynamic shaker at input levels ranging between 0.5 g (rms) and 1.5 g (rms). Vibrations were applied both along and perpendicular to the rotor axis. Response measurements were analyzed for amplitude distribution and power spectral density. Experimental results compare well with calculations of amplitude power spectral density made for the case where the vibrations were applied along the rotor axis. In this case, the rotor-bearing system was treated as a linear, three-mass model.

Tessarzik, J. M.; Chiang, T.; Badgley, R. H.

1974-01-01

60

Studies on vibration characteristics of a pear using finite element method  

Microsoft Academic Search

The variation of the vibration characteristics of a Huanghua pear was investigated using finite element simulations. A new\\u000a image processing technique was used to obtain the unsymmetrical and un-spherical geometrical model of a pear. The vibration\\u000a characteristics of this type of pear with the correlation of its behavior with geometrical configurations and material characteristics\\u000a were investigated using numerical modal analysis.

Hui-zhi Song; Jun Wang; Yong-hui Li

2006-01-01

61

Experimental measurements of the Space Shuttle main engine fuel and oxygen turbopump vibration characteristics  

NASA Technical Reports Server (NTRS)

The vibration characteristics of the SSME (Space Shuttle main engine) are dealt with. The Space Shuttle engine consists of a main rocket nozzle and attached to it are high pressure fuel and oxygen pumps. Various vibration problems have been encountered with both the hydrogen and oxygen pumps. The vibration spectrum of the hydrogen and oxygen pumps has been analyzed by various techniques using synchronous tracking filters and FFT analyzers. The experimental data has been correlated to theoretical predictions of resonance frequencies.

Gunter, E. J.; Flack, R. D.

1981-01-01

62

Vibration characteristics of grafts for the tympanic membrane.  

PubMed

Perforation of the tympanic membrane occurs frequently as a result of infection, external trauma, and high-level impulsive sound pressure, such as that associated with an explosion. Many different surgical techniques can be used to repair the tympanic membrane and ossicles. Clinical operations such as tympanoplasty are undertaken to repair the damaged tympanic membrane and ossicles, thus improving hearing and reducing the chance of infection. The membrane is repaired or replaced with the use of graft materials, either from the patient's body or from artificial sources. The selection of graft material is very important because, as much as possible, it must exhibit the same dynamic behavior as the natural membrane. To compare various allograft materials, investigators developed a model of the ear on which different graft materials can be replaced. Three different membrane materials - irradiated allograft dura (Tutoplast Dura; IOP Inc., Costa Mesa, Calif), irradiated allograft fascia lata (Tutoplast Fascia Lata; IOP Inc.), and irradiated allograft fascia temporalis (Tutoplast Fascia Temporalis; IOP Inc.) - were used. Vibration responses of these membrane materials produced by defined sound signals with different frequencies were recorded by a small strain gauge; the spectra of sound for various corresponding input signals were recorded, and the results were compared with those of the sample graft material. Tutoplast Fascia Lata accomplished the best dynamic performance in vitro. Additional clinical and experimental data are needed, however, to determine which of these materials provides the best audiological and clinical performance. PMID:17526464

Oktem, Fatih; Toprak, Murat; Yener, Murat; Bozdag, Ergun; Sunbuloglu, Emin; Toprak, Tuncer

2007-01-01

63

Research on the low-frequency vibration characteristics of the adaptive isolator based on MR damper  

Microsoft Academic Search

Based on the idea that combining traditional vibration-reduction components parallel with intelligent components, a new approach to the design of isolator which acts as vibration isolator and impact buffer is presented in this paper. With the application of magnetorheological damper (MR damper) and wire rope spring, an adaptive isolator is designed, whose dynamic characteristics is adaptive and controllable. By using

Dongyan Shi; Xianjie Shi

2010-01-01

64

Measurement of the Resonant Characteristics of a Single Bubble Vibration by Using a Laser Doppler Vibrometer  

Microsoft Academic Search

We constructed the experimental system with a laser Doppler vibrometer (LDV) for measuring the vibration of a single microbubble. It was demonstrated that the system enabled the capture of the vibration with an amplitude of nanometer order. We attempted to experimentally measure the resonant characteristics of a bubble attached to a wall by using the system. As a result, we

Taisuke Yoshikawa; Hironori Kotera; Kenji Yoshida; Daisuke Koyama; Kentaro Nakamura; Yoshiaki Watanabe

2011-01-01

65

Vibration characteristics of hexagonal radial rib and hoop platforms  

NASA Technical Reports Server (NTRS)

Experiment and analysis have been used to characterize the modes of vibration of planar radial rib and hoop hexagonal platforms. Finite element analysis correlated very well with experimental results. The sensitivity of mode shapes and frequencies to cable stiffness and initial tension is presented. Threshold values have been identified, above which changes in cable stiffness do not affect the first few platform vibration modes. Primary vibration modes of the radial rib platform involve beam bending. Vibration modes of the hoop platform exhibit both beam bending and frame bending and torsion. Results indicate for low order polygonal structures, the radial rib concept produced a higher fundamental frequency. For high order polygonal structures, the hoop concept has the potential to achieve a higher fundamental frequency than the radial rib concept.

Belvin, W. K.

1983-01-01

66

Vibration analysis of shell-and-tube heat exchangers: an overview-Part 2: vibration response, fretting-wear, guidelines  

NASA Astrophysics Data System (ADS)

Design guidelines were developed to prevent tube failures due to excessive flow-induced vibration in shell-and-tube heat exchangers. An overview of vibration analysis procedures and recommended design guidelines is presented in this paper. This paper pertains to liquid, gas and two-phase heat exchangers such as nuclear steam generators, reboilers, coolers, service water heat exchangers, condensers, and moisture-separator-reheaters. Part 2 of this paper covers forced vibration excitation mechanisms, vibration response prediction, resulting damage assessment, and acceptance criteria.

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

2003-11-01

67

Seated Occupant Apparent Mass Characteristics Under Automotive Postures and Vertical Vibration  

NASA Astrophysics Data System (ADS)

The biodynamic apparent mass response characteristics of 24 human subjects (12 males and 12 females) seated under representative automotive postures with hands-in-lap (passengers) and hands-on-steering wheel (drivers) are reported. The measurements were carried out under white noise vertical excitations of 0·25, 0·5 and 1·0m/s2r.m.s. acceleration magnitudes in the 0·5-40Hz frequency range and a track measured input (1·07m/s2). The measured data have been analyzed to study the effects of hands position, body mass, magnitude and type of vibration excitation, and feet position, on the biodynamic response expressed in terms of apparent mass. A comparison of the measured response of subjects assuming typical automotive postures involving inclined cushion, inclined backrest and full use of backrest support with data determined under different postural conditions and excitation levels revealed considerable differences. The biodynamic response of automobile occupants seated with hands in lap, peaks in the 6·5-8·6Hz frequency range, which is considerably higher than the reported range of fundamental frequencies (4·5-5Hz) in most other studies involving different experimental conditions. The peak magnitude tends to decrease considerably for the driving posture with hands-on-steering wheel, while a second peak in the 8-12 Hz range becomes more apparent for this posture. The results suggest that biodynamic response of occupants seated in automotive seats and subject to vertical vibration need to be characterized, as a minimum, by two distinct functions for passenger and driving postures. A higher body mass, in general, yields higher peak magnitude response and lower corresponding frequency for both postures. The strong dependence of the response on the body mass is further demonstrated by grouping the measured data into four different mass ranges: less than 60 kg, between 60·5 and 70 kg, between 70·5 and 80 kg, and above 80 kg. From the results, it is concluded that hands position and body mass have the most significant influence on the apparent mass response under automotive posture and vibration.

RAKHEJA, S.; HARU, I.; BOILEAU, P.-É.

2002-05-01

68

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

69

Vibrations  

NASA Astrophysics Data System (ADS)

Low frequent vibrations may cause from disturbing up to damaging effects. There is no precise distinction between structure-borne sound and vibrations. However - depending on the frequency range - measurements and predictions require different techniques. In a wide frequency range, the generation, transmission and propagation of vibrations can be investigated similar to structure-borne sound (see Chap. 9).

Guggenberger, Johannes; Müller, Gerhard

70

Flow-induced vibration characteristics of BWR/6-238 jet pumps  

SciTech Connect

Four prototype BWR/6-238 jet pumps (two jet pump pairs) were tested to determine their flow-induced vibration (FIV) characteristics in the High Flow Hydraulic Facility, (HF)/sup 2/, over the period June to September 1978. Tests consisted of operating the jet pumps, which were heavily instrumented with accelerometers, pressure transducers and strain gages, at the design operating condition, as well as at numerous off-design drive flows and M-ratios, and at temperatures between 70/sup 0/F and 180/sup 0/F and at 455 psig. Results were combined with those from past jet pump tests to predict the response at reactor temperature (533/sup 0/F). Major conclusions reached related to the BWR/6-238 jet pump are presented.

Schardt, J.F.

1982-09-01

71

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

72

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

73

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

74

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

75

Analysis of generator vibration characteristic on rotor winding interturn short circuit fault  

Microsoft Academic Search

Rotor winding interturn short circuit fault is one of the common faults in generator, and analyzing fault mechanism and diagnosis method is very necessary. This paper analyzes generator rotor and stator vibration characteristic caused by the fault. Firstly calculates air-gap magnetomotive force distribution, air-gap magnetic field energy and magnetic flux density on the fault. Then analyzes the frequency characteristic of

Wan Shuting; Xu Zhaofeng; Li Yonggang; Hou Zili; Li Heming

2003-01-01

76

Training Data Optimized and Conditioned to Learn Characteristic Patterns of Vibrating Blisks and Fan Blades  

NASA Technical Reports Server (NTRS)

At the NASA Glenn Research Center, we have been training artificial neural networks to interpret the characteristic patterns (see the leftmost image) generated from electronic holograms of vibrating structures. These patterns not only visualize the vibration properties of structures, but small changes in the patterns can indicate structural changes, cracking, or damage. Neural networks detect these small changes well. Our objective has been to adapt the neural-network, electronic-holography combination for inspecting components in Glenn's Spin Rig.

Decker, Arthur J.

2001-01-01

77

Vibration and Damping Characteristics of a Beam with a Partially Sandwiched Viscoelastic Layer  

Microsoft Academic Search

The purpose of this study is to verify the vibration and damping characteristics of a partially-layered elastic-viscoelastic-elastic structure both theoretically and experimentally.The fourth-order differential equations of motion are derived for the transverse vibration of a three-layered sandwich beam with a viscoelastic (or adhesive) core layer. The transverse displacements of the constraining layer and the base beam are assumed to have

Tae-Hak Park

1997-01-01

78

Subjective and biomechanical responses to complex whole-body vibration stimuli  

Microsoft Academic Search

When an individual is exposed to whole-body vibration they are almost always exposed to vibration that occurs in the fore-and-aft, lateral and vertical directions simultaneously. In many cases there can also be significant components of roll, pitch and yaw. Despite the nature of vibration exposure being complex, almost all laboratory studies of the subjective and biomechanical responses to vibration have

Neil J Mansfield; Setsuo Maeda

79

Vibration and Noise Characteristics of Elliptical Gears due to Non-Uniform Rotation  

NASA Astrophysics Data System (ADS)

Elliptical gear is a typical non-circular gear, which transmits a variable-ratio rotation and power simultaneously. Due to the non-uniform rotation, the vibration and noise of elliptical gears demonstrate particular characteristics which should be paid attention to in practical application. In this paper, two elliptical gears, which are a single elliptical gear and a double elliptical gear, have been investigated to analyze the vibration and noise characteristics of elliptical gears. The corresponding circular gears for comparison are also investigated. General factors including the torque, the rotation speed, the gear vibration acceleration and the gear noise of the four test gears are measured by running test. The root mean square of the Circumferential Vibration Acceleration (CVA) and the sound pressure level of the noise of elliptical gears are obtained from the measured results and compared with those of circular gears to clarify the vibration and noise characteristics of elliptical gears. Furthermore, the frequency analysis of the CVA of elliptical gears is conducted by Fast Fourier Transform Algorithm (FFT) and compared with that of circular gears. The main vibration component of elliptical gear is uncovered according to the obtained frequency spectra. In addition, the Critical Rotation Speeds of Tooth Separation (CRSTS) of elliptical gear is obtained and its relation with load torque is unveiled.

Liu, Xing; Nagamura, Kazuteru; Ikejo, Kiyotaka

80

An analytical and experimental study of the vibration response of a clamped ribbed plate  

NASA Astrophysics Data System (ADS)

An analytical solution is presented in this paper for the vibration response of a ribbed plate clamped on all its boundary edges by employing a traveling wave solution. A clamped ribbed plate test rig is also assembled in this study for the experimental investigation of the ribbed plate response and to provide verification results to the analytical solution. The dynamic characteristics and mode shapes of the ribbed plate are measured and compared to those obtained from the analytical solution and from finite element analysis (FEA). General good agreements are found between the results. Discrepancies between the computational and experimental results at low and high frequencies are also discussed. Explanations are offered in the study to disclose the mechanism causing the discrepancies. The dependency of the dynamic response of the ribbed plate on the distance between the excitation force and the rib is also investigated experimentally. It confirms the findings disclosed in a previous analytical study [T.R. Lin, J. Pan, A closed form solution for the dynamic response of finite ribbed plates, Journal of the Acoustical Society of America 119 (2006) 917-925] that the vibration response of a clamped ribbed plate due to a point force excitation is controlled by the plate stiffness when the source is more than a quarter plate bending wavelength away from the rib and from the plate boundary. The response is largely affected by the rib stiffness when the source location is less than a quarter bending wavelength away from the rib.

Lin, Tian Ran

2012-02-01

81

Vibration and dynamic response of functionally graded plates with piezoelectric actuators in thermal environments  

NASA Astrophysics Data System (ADS)

This paper deals with the nonlinear vibration and dynamic response of a functionally graded material (FGM) plate with surface-bonded piezoelectric layers in thermal environments. Heat conduction and temperature-dependent material properties are both taken into account. The temperature field considered is assumed to be a uniform distribution over the plate surface and varied in the thickness direction of the plate, and the electric field is assumed to be the transverse component Ez only. Material properties of the substrate FGM layer are assumed to be temperature-dependent, and graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents, whereas the material properties of piezoelectric layers are assumed to be independent of the temperature and the electric field. The nonlinear formulations are based on the higher-order shear deformation plate theory and general von Kármán-type equation, which includes thermo-piezoelectric effects. The numerical illustrations concern nonlinear vibration characteristics of functional graded plates with fully covered piezoelectric actuators under different sets of thermal and electric loading conditions. The effects of temperature change, control voltage and volume fraction distribution on the nonlinear vibration and dynamic response are examined in detail.

Huang, Xiao-Lin; Shen, Hui-Shen

2006-01-01

82

Vibration of Rectangular Plates Using Plate Characteristic Functions as Shape Functions in the RAYLEIGH RITZ Method  

NASA Astrophysics Data System (ADS)

The plate characteristic functions are used to express the deflection shapes in the Rayleigh-Ritz method to study rectangular plate vibrations. Since the plate characteristic functions are reasonable approximations to the vibration modes, they are found to improve the convergence of vibration frequencies. These plate frequencies are used to check the accuracy of the Rayleigh frequencies associated with the plate characteristic function modes. Computations are carried out for each of the four mode categories of a clamped square plate. In each mode category, the first 30 natural frequencies are tabulated and the first nine mode diagrams are drawn. The results show that the choice of specific shape functions enhances the effectiveness of the Rayleigh-Ritz method.

Rajalingham, C.; Bhat, R. B.; Xistris, G. D.

1996-06-01

83

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

84

Experimental-theoretical investigation of the vibration characteristics of rotating composite box beams  

NASA Astrophysics Data System (ADS)

The objective of the study was to predict the effect of elastic couplings on the free vibration characteristics of thin-walled composite box beams and to correlate the results with experimental data. The free vibration characteristics of coupled thin-walled composite beams under rotation were determined using the Galerkin method. The theoretical results were found to be in satisfactory agreement with experimental data obtained for graphite/epoxy, kevlar/epoxy, and glass/epoxy composite beams in an in-vacuo test facility at different rotational speeds.

Chandra, Ramesh; Chopra, Inderjit

1992-08-01

85

Sensitivity analysis of torsional vibration characteristics of helicopter rotor blades. Part 1: Structural dynamics analysis  

NASA Technical Reports Server (NTRS)

A theoretical investigation of structural vibration characteristics of rotor blades was carried out. Coupled equations of motion for flapwise bending and torsion were formulated for rotor blades with noncollinear elastic and mass axes. The finite element method was applied for a detailed representation of blade structural properties. Coupled structural mass and stiffness coefficients were evaluated. The range of validity of a set of coupled equations of motion linearized with respect to eccentricity between elastic and mass axes was investigated. The sensitivity of blade vibration characteristics to torsion were evaluated by varying blade geometric properties, boundary conditions, and eccentricities between mass and elastic axes.

Bratanow, T.; Ecer, A.

1974-01-01

86

[Cellular responses to vibration during dental drilling with belt drive motor engine (in vitro) (author's transl)].  

PubMed

There have been many reports on the pulpal reaction caused by vibration during high speed dental drilling with air turbine hand-piece. It is, however, not clear pulpal responses to vibration of low speed drilling with 7 000 rpm of belt drive motor engine which produces a fundamental vibration of about 170 cps having most unpleasant sensation at vestibular apparatus. Here, cellular responses of L strain cells to vibration derived from 7 000 rpm and 15 000 rpm of belt drive motor engine were observed in vitro system. There is no difference between the both cellular responses to the vibration of 7 000 rpm and 15 000 rpm. Suspended free cells were easily influenced and degenerated by the vibration, and remarkably checked in their cell-multiplication. On the contrary, in the cells adhered to the substratum of glassware, no degeneration and no inhibitory effect were observed. And the cells showed reversible response of cytoplasmic shrinkage only. PMID:1100737

Yamanaka, K

1975-05-01

87

Characteristics of vibrational temperature of hydrogen molecules in detached plasma  

NASA Astrophysics Data System (ADS)

The ground-state vibrational temperature of hydrogen molecules, Tvib, is observed in detached plasma using a VUV spectrometer on a linear plasma device, TPD-SheetIV. Tvib was deduced by applying the corona equilibrium model by using the electron impact excitation rate and the spontaneous emission coefficient, taking into account the cascade contribution of E,F1?g+ and the radiation trapping. Tvib can be found which results in a fit to the observed relative intensities of VUV spectrum in the range from 90 to 150 nm. With increasing gas pressure P, Tvib gradually decreases from 5000 to 3000 K and remains nearly constant at around 1000 K in detached plasma at discharge current of 50 A.

Nakanowatari, A.; Tonegawa, A.; Shibuya, T.; Kawamura, K.

2009-06-01

88

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

89

Crack Detection In Cantilever Beam Using Vibration Response  

NASA Astrophysics Data System (ADS)

In the present work, a methodology for predicting crack parameters (crack depth and its location) in a thin cantilever beam using vibration response has been developed. Parametric studies have been carried out using ANSYS Software to evaluate modal parameters (natural frequencies and mode shapes) for different crack parameters. From the analysis, it has been observed that both crack location and crack depth have noticeable effects on the modal parameters of the cracked beam. Also, a certain frequency may correspond to different crack depths and its locations. Based on this, the contour lines of the cracked beam frequencies have been plotted having crack location and crack depth as its axis. The location and depth corresponding to any point on this curve becomes a possible crack location and depth. The identification procedure presented in this study is believed to provide a useful tool for detection of medium size crack in a beam.

Batabyal, A. K.; Sankar, P.; Paul, T. K.

90

Non-linear dual-axis biodynamic response to vertical whole-body vibration  

Microsoft Academic Search

Seated human subjects have been exposed to vertical whole-body vibration so as to investigate the non-linearity in their biodynamic responses and quantify the response in directions other than the direction of excitation. Twelve males were exposed to random vertical vibration in the frequency range 0.25–25Hz at four vibration magnitudes (0.125, 0.25, 0.625, and 1.25ms?2r.m.s.). The subjects sat in four sitting

N. Nawayseh; M. J Griffin

2003-01-01

91

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

92

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

93

Acceleration response spectrum for predicting floor vibration due to occupant walking  

NASA Astrophysics Data System (ADS)

Annoying vibrations caused by occupant walking is an important serviceability problem for long-span floors. At the design stage the floor?s structural arrangement may frequently change to cater for the owner?s varying requirements. An efficient and accurate approach for predicting a floor?s acceleration response is thus of great significance. This paper presents a design-oriented acceleration response spectrum for calculating a floor?s response given the floor?s modal characteristics and a specified confidence level. 2204 measured footfall traces from 61 test subjects were used to generate 10 s peak root-mean-square acceleration response spectra, on which a piecewise mathematical representation is based. The proposed response spectrum consists of three main parts: the first harmonic plateau ranging from 1.5 to 2.5 Hz, the second harmonic plateau ranging from 3.0 to 5.0 Hz and the descending part going with frequencies from 5.0 to 10.0 Hz. The representative value of each plateau and the mathematical representation for the descending curve were determined statistically for different confidence levels. Furthermore, the effects of factors, such as floor span, occupant stride length, higher modes of vibration, boundary conditions and peak acceleration response, on the proposed spectrum have been investigated and a modification measure for each factor is suggested. A detailed application procedure for the proposed spectrum approach is presented and has been applied to four existing floors to predict their acceleration responses. Comparison between predicted and field measured responses shows that the measured accelerations of the four floors are generally close to or slightly higher than the predicted values for the 75 percent confidence level, but are all lower than the predicted values for the 95 percent confidence level. Therefore the suggested spectrum-based approach can be used for predicting a floor?s response subject to a single person walking.

Chen, Jun; Xu, Ruotian; Zhang, Mengshi

2014-07-01

94

Bone cell responses to high-frequency vibration stress: does the nucleus oscillate within the cytoplasm?  

Microsoft Academic Search

Mechanosensing by cells directs changes in bone mass and structure in response to the chal- lenges of mechanical loading. Low-amplitude, high- frequency loading stimulates bone growth by enhancing bone formation and inhibiting disuse osteoporosis. However, how bone cells sense vibration stress is unknown. Hence, we investigated bone cell responses to vibration stress at a wide frequency range (5-100 Hz). We

Rommel G. Bacabac; Theo H. Smit; Jack J. W. A. Van Loon; Behrouz Zandieh Doulabi; Marco Helder; Jenneke Klein-Nulend

2006-01-01

95

Estimations of the smoothing operator response characteristics  

NASA Technical Reports Server (NTRS)

The mean response characteristic of the graphical smoothing method is discussed. The method is illustrated by analysis of latitude observations at Washington from 1915.9 to 1941.0. Spectral density, frequency distribution, and distribution functions are also discussed.

Yatskiv, Y. S.

1974-01-01

96

Characteristic fringe function for time-average holography of periodic nonsinusoidal vibrations  

Microsoft Academic Search

In this paper the characteristic fringe function of hologram interferometry has been evaluated for the case of periodic, nonsinusoidal vibrations represented by a Jacobian elliptic function. To consider the reconstructed holographic image of an object, use has been made of an equation derived from considerations of the effect of motion on coherence. Graphical representation of the fringe irradiance distribution in

P. C. Gupta; K. Singh

1975-01-01

97

Research on the Mechanics Characteristics of Ship Vibration Reduction and Impact Resistance Isolator Based on MR  

Microsoft Academic Search

In this paper, a new-style isolator system in ship is presented, which is composed of wire rope and MR damper in parallel. By taking advantages of the high damping and damping variability of MR damper, it is possible to make the mechanics characteristics of isolator controllable and then solve the problem of vibration reduction in low frequency and impact resistance

Xiong-liang Yao; Zheng-dong Tian; Zhong-chao Deng; Zhi-hua Shen

2007-01-01

98

Some constructions and characteristics of rod-type piezoelectric ultrasonic motors using longitudinal and torsional vibrations  

Microsoft Academic Search

Ultrasonic motors using longitudinal and torsional motions of rod vibrators have previously been proposed. Several motor constructions, whose forms are different from the previous ones, are proposed and their characteristics are experimentally examined in order to develop the ultrasonic motors of this type; that is, they are expected to have much different uses, according to how their forms are modified.

Yoshiro Tomikawa; Kazunari Adachi; Manabu Aoyagi; Tadaatsu Sagae; Takehiro Takano

1992-01-01

99

Vibration Characteristics of Ultrasonic Transducer in Thermosonic Flip Chip Bonding  

Microsoft Academic Search

Thermosonic flip chip bonding has been widely used in fine pitch IC packaging for its unique features. By using thermosonic flip chip bonding at an aluminum wire bonder, 1 mm*1 mm chip with 8 gold bumps is bonded successfully to Ag substrate, and the bonding strength reaches as high as about 30gf\\/bump. Dynamical characteristics of ultrasonic transducer are investigated by

Zhili Long; Yunxin Wu; Lei Han; Jue Zhong

2007-01-01

100

Analyses of vibration responses on nanoscale processing in a liquid using tapping-mode atomic force microscopy  

NASA Astrophysics Data System (ADS)

An analytical solution of the vibration responses of biological specimens using atomic force microscopy (AFM), which often requires operation in a liquid, is developed. In this study, the modal superposition method is employed to analyze the vibration responses of AFM cantilevers in tapping mode (TM) operated in a liquid and in air. The hydrodynamic force exerted by the fluid on AFM cantilevers is approximated by additional mass and hydrodynamic damping. The tip-sample interaction forces were transformed into axial, distributed transversal, and bending loading, and then applied to the end region of the AFM through the tip holder. The effects of transverse stress and bending stress were adopted to solve the dynamic model. With this model, a number of simulations were carried out to investigate the relationship between the transient responses of the cantilever in a liquid and the parameters considered in nanoscale processing. The simulations show that the vibration of AFM cantilevers in a liquid has dramatically different dynamic characteristics from these of that in air. The liquid reduces the magnitude of the transversal response and reduces the cantilever resonances. Moreover, the magnitudes of response become larger with increasing intermolecular distances and smaller with decreasing tip length. The cantilever vibration amplitudes significantly depend on the damping constant and the mass proportionality constant.

Horng, Thin-Lin

2009-10-01

101

Performance and flow-induced vibration characteristics for conical-ring turbulators  

Microsoft Academic Search

In the present study, the performance characteristics of the conical-ring turbulators are determined by means of the entropy-generation minimization method based on the second law and enhancement efficiency based on the first law of thermodynamics. The relations between these performance and flow-induced vibration characteristics have been examined. The maximum entropy generation, at the same Reynolds number, occurs in sequence by

Kenan Yakut; Bayram Sahin; Suat Canbazoglu

2004-01-01

102

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

103

Optimization of Training Sets For Neural-Net Processing of Characteristic Patterns From Vibrating Solids  

NASA Technical Reports Server (NTRS)

An artificial neural network is disclosed that processes holography generated characteristic pattern of vibrating structures along with finite-element models. The present invention provides for a folding operation for conditioning training sets for optimally training forward-neural networks to process characteristic fringe pattern. The folding pattern increases the sensitivity of the feed-forward network for detecting changes in the characteristic pattern The folding routine manipulates input pixels so as to be scaled according to the location in an intensity range rather than the position in the characteristic pattern.

Decker, Arthur J. (Inventor)

2006-01-01

104

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

105

Dynamic characteristics of a base isolated building from ambient vibration measurements and low level earthquake shaking  

Microsoft Academic Search

Ambient vibration tests were conducted on a base-isolated apartment building in Takamatsu, Japan, to determine the mode shapes and the associated natural frequencies and damping ratios at very low levels of excitation. The latest developments in signal analysis for modal decomposition are used to analyze the ambient response data. A finite element model of the building and isolators was calibrated

C. E Ventura; W. D Liam Finn; J.-F Lord; N Fujita

2003-01-01

106

The transmission of vertical vibration through seats: Influence of the characteristics of the human body  

NASA Astrophysics Data System (ADS)

The transmission of vibration through a seat depends on the impedance of the seat and the apparent mass of the seat occupant. This study was designed to determine how factors affecting the apparent mass of the body (age, gender, physical characteristics, backrest contact, and magnitude of vibration) affect seat transmissibility. The transmission of vertical vibration through a car seat was measured with 80 adults (41 males and 39 females aged 18-65) at frequencies between 0.6 and 20 Hz with two backrest conditions (no backrest and backrest), and with three magnitudes of random vibration (0.5, 1.0, and 1.5 m s -2 rms). Linear regression models were used to study the effects of subject physical characteristics (age, gender, and anthropometry) and features of their apparent mass (resonance frequency, apparent mass at resonance and at 12 Hz) on the measured seat transmissibility. The strongest predictor of both the frequency of the principal resonance in seat transmissibility and the seat transmissibility at resonance was subject age, with other factors having only marginal effects. The transmissibility of the seat at 12 Hz depended on subject age, body mass index, and gender. Although subject weight was strongly associated with apparent mass, weight was not strongly associated with seat transmissibility. The resonance frequency of the seat decreased with increases in the magnitude of the vibration excitation and increased when subjects made contact with the backrest. Inter-subject variability in the resonance frequency and transmissibility at resonance was less with greater vibration excitation, but was largely unaffected by backrest contact. A lumped parameter seat-person model showed that changes in seat transmissibility with age can be predicted from changes in apparent mass with age, and that the dynamic stiffness of the seat appeared to increase with increased loading so as to compensate for increases in subject apparent mass associated with increased sitting weight.

Toward, Martin G. R.; Griffin, Michael J.

2011-12-01

107

Modal vibration response measurements for characterization of composite materials and structures  

Microsoft Academic Search

This paper summarizes recent research by the author, his colleagues and graduate students on the use of modal vibration response measurements to characterize, quickly and accurately the mechanical properties of fiber-reinforced composite materials and structures. It is shown that modal testing in either a single mode or multiple modes of vibration can be used to determine elastic moduli and damping

Ronald F. Gibson

2000-01-01

108

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

109

Insulation of nonlinear and random vibrations in the mining industry. [elastodynamic response of rubber insulator  

NASA Technical Reports Server (NTRS)

The insulation of nonlinear and random vibrations is considered for some ore preparing and sorting implements: rotary crushers, resonance screens, hammer mills, etc. The appearance of subharmonic vibrations is analyzed, and the conditions for their appearance are determined. A method is given for calculating the insulation of these vibrations by means of elastic elements made of rubber. The insulation of the random vibrations produced by Symons crushers is calculated by determining the transmissability and deformation of the insulation system for a narrow band random response.

Zeveleanu, C.

1974-01-01

110

A comparative study: polishing characteristics and its mechanisms of three vibration modes in vibration-assisted magnetic abrasive polishing  

Microsoft Academic Search

The automatic precision polishing technique of three-dimensional complicated micro-curved surfaces of components in extremely low surface roughness and high efficiency is greatly demanded by advanced industrial fields. The existing polishing methods have great difficulty in satisfying these demands. Therefore, three modes (horizontal vibration, vertical vibration and compound vibration) of vibration-assisted magnetic abrasive polishing processes have been developed. Previous research focused

Shaohui Yin; Takeo Shinmura

2004-01-01

111

Electrically induced large-amplitude vibration and resonance characteristics on ionic polymeric membrane-metal composites artificial muscles  

NASA Astrophysics Data System (ADS)

This research identifies key parameters involving the vibrational characteristics of actuators made of ion-exchange- membrane-metal composites. These actuators are made from commercially available ion-exchange membranes chemically treated with platinum to produce composite actuators that are highly deformable in the presence of low amplitude electrical field. They show remarkable bending displacement that follow input signal very closely. When the applied signal frequency is varied, so does the displacement up to a point where large deformations are observed at a critical frequency called resonant frequency where maximum deformation is observed. Beyond which the actuator response is diminished. In this research paper, several samples of the actuators were made and tested with various dimensions to compare the vibrational behavior of the actuators. A data acquisition system was used to measure the parameters involved and record the results in real time basis. This research was in support of active vibration suppression research for flexible structures using ionic polymers as active dampers. It also supported other applications in biomimetics research such as bird flight motion, artificial coral reefs and marine propulsion.

Shahinpoor, Mohsen; Mojarrad, Mehran; Salehpoor, Karim

1997-06-01

112

High Frequency Rogowski Coil Response Characteristics  

Microsoft Academic Search

The high frequency response characteristics of differentiating and self-integrating Rogowski coils have been calculated for arbitrary values of the coil terminating resistance assuming Ampere's law to be valid. Effects due to a reactive terminating impedance are also discussed. When the displacement current is taken into account in the measurement of the current of a charged particle beam, it is found

W. Stygar; G. Gerdin

1982-01-01

113

Vibration characteristics of composite piezoceramic plates at resonant frequencies: experiments and numerical calculations  

Microsoft Academic Search

The experimental measurement of the resonant frequencies for the piezoceramic material is generally performed by impedance analysis. In this paper, we employ an optical interferometry method called the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) to investigate the vibration characteristics of piezoceramic\\/aluminum laminated plates. The AF-ESPI is a powerful tool for the full-field, noncontact, and real-time measurement method of surface displacement

Chi-Hung Huang; Chien-Ching Ma

2001-01-01

114

Assessing the Influence of Antivibration Glove on Digital Vascular Responses to Acute Handarm Vibration  

Microsoft Academic Search

Abstract: Assessing the Influence of Antivibration Glove on Digital Vascular Responses to Acute Hand-arm Vibration: Md H. M AHBUB , et al. Department of Hygiene, Yamaguchi University School of Medicine—This study was,designed,to assess the influence of an antivibration glove on digital vascular responses,in healthy,subjects exposed,to short-term grasping of a vibrating handle. T o measure finger blood flow (FBF) and finger

Kenjiro Yokoyama; Masaiwa Inoue; Yukio Takahashi; Shinji Yamamoto; Noriaki Harada

2007-01-01

115

Synchronisation of motor firing by vibration during stretch evoked responses of the human wrist flexors.  

PubMed

The wrist was rapidly dorsiflexed while the flexor muscles were being vibrated at 120 Hz. During both the M1 and the M2 responses the EMG showed a series of waves at the vibration frequency. When the vibration was turned off after overlapping with the stretch for only three to four cycles these EMG waves ceased about 30 ms later. Spinal reflexes are thus shown to continue to influence the discharging motoneurones throughout the human M2 "long-latency" response. PMID:7056335

Matthews, P B; Bawa, P; Matthews, H R

1982-01-01

116

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.

Griffin, M; Bovenzi, M; Nelson, C

2003-01-01

117

The new diagnosis method of rotor winding inter-turn short circuit fault and imbalance fault based on stator and rotor vibration characteristics  

Microsoft Academic Search

Stator and rotor vibration characteristics of generator are analyzed when the rotor winding inter-turn short circuit fault and the imbalance fault occur. The rotor vibration of fundamental frequency increases and the stator vibration of second frequency decreases when the rotor winding inter-turn short circuit fault occurs. But when the imbalance fault occurs, the rotor vibration of fundamental frequency increases and

Wan Shuting; Li Yonggang; Li Heming; Tang Guiji

2005-01-01

118

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

119

Vibration responses of h-BN sheet to charge doping and external strain  

SciTech Connect

Based on density functional theory and density functional perturbation theory calculations, we systematically investigate the vibration responses of h-BN sheet to charge doping and external strains. It is found that under hole doping, the phonon frequencies of the ZO and TO branches at different wave vector q shift linearly with different slopes. Under electron doping, although the phonon frequencies shift irregularly, the shifting values are different at different phonon wave vectors. Interestingly, we find that external strain can restrain the irregular vibration responses of h-BN sheet to electron doping. The critical factor is revealed to be the relative position of the nearly free electron and boron p{sub z} states of h-BN sheet. Under external strains, the vibration responses of h-BN sheet are also found to be highly dependent on the phonon branches. Different vibration modes at different q points are revealed to be responsible for the vibration responses of h-BN sheet to charge doping and external strain. Our results point out a new way to detect the doping or strain status of h-BN sheet by measuring the vibration frequencies at different wave vector.

Yang, Wei; Yang, Yu; Zheng, Fawei [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)] [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Zhang, Ping, E-mail: zhang-ping@iapcm.ac.cn [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China) [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Beijing Computational Science Research Center, Beijing 100084 (China)

2013-12-07

120

Vibration response imaging: protocol for a systematic review  

PubMed Central

Background The concept of lung sounds conveying information regarding lung physiology has been used extensively in clinical practice, particularly with physical auscultation using a stethoscope. Advances in computer technology have facilitated the construction of dynamic visual images derived from recorded lung sounds. Arguably, the most significant progress in this field was the development of the commercially available vibration response imaging (VRI) (Deep Breeze Ltd, Or-Akiva, Israel). This device provides a non-invasive, dynamic image of both lungs constructed from sounds detected from the lungs using surface sensors. In the literature, VRI has been utilized in a multitude of clinical and research settings. This systematic review aims to address three study questions relating to whether VRI can be used as an evaluative device, whether the images generated can be characterized, and which tools and measures have been used to assess these images. Methods/Design This systematic review will involve implementing search strategies in five online journal databases in order to extract articles relating to the application of VRI. Appropriate articles will be identified against a set of pre-determined eligibility criteria and assessed for methodological quality using a standardized scale. Included articles will have data extracted by the reviewers using a standardized evidence table. A narrative synthesis based on a standardized framework will be conducted, clustering evidence into three main groups; one for each of the study questions. A meta-analysis will be conducted if two or more research articles meet pre-determined criteria that allow quantitative synthesis to take place. Discussion This systematic review aims to provide a complete overview of the scope of VRI in the clinical and research settings, as well as to discuss methods to interpret the data obtained from VRI. The systematic review intends to help clinicians to make informed decisions on the clinical applicability of the device, to allow researchers to identify further potential avenues of investigation, and to provide methods for the evaluation and interpretation of dynamic and static images. The publication and registration of this review with PROSPERO provides transparency and accountability, and facilitates the appraisal of the proposed systematic review against the original design. Trial registration PROSPERO registration number: CRD42013003751

2013-01-01

121

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

122

Vibration Response as an Indicator of Ground Fall Hazards in Mining: An Investigation Using Laser Doppler Vibrometry  

NASA Astrophysics Data System (ADS)

Unexpected falls of ground are one of the leading sources of injuries and fatalities in U. S. underground mines. A primary means of assessing mine-roof integrity is the age-old method of roof sounding where a miner taps on the roof and listens to the resulting seismically coupled acoustic response. Impacts to loose, hazardous blocks of rock generally produce a hollow drummy sound that is anomalously low in frequency and long in duration compared to sounds from competent rock. In this study, a noncontact laser Doppler vibrometry (LDV) method is used to record vibrations on rock surfaces to (i) evaluate the feasibility of remotely detecting hazardous ground from safe positions and (ii) delineate the fundamental, and little-studied, mechanical processes attending such gravity-driven failures. During the technique development stage, measurements were obtained on various rock outcrops and other structures with known defects; these included single-point and two-dimensional array recordings. Excitation sources included local and remote impacts, and ambient and forced vibrations. Consistent with predictions from simple models of elastic blocks coupled to solid ground through low-stiffness interfaces, loose rocks were effectively delineated with simple broadband RMS measures of elevated particle velocity. Other narrow-band spectral measures were also investigated and observed to be sensitive to block geometry, interface boundary conditions, and excitation source characteristics. In most of the experiments, loose blocks could be identified, in a comparative sense, even without compensating for the attendant vibration of the LDV. To deliver useful vibration response information to miners and others exposed to these hazards, two options are being explored: (i) development of 2-D maps of vibration response superimposed on target images and (ii) conversion of single-point LDV output into audible signals for use in a qualitative comparative mode.

Swanson, P. L.; Rettkowski, J. D.; Caley, A. B.

2003-12-01

123

Response characteristics of a fractional oscillator  

NASA Astrophysics Data System (ADS)

The integral equation of motion of a driven fractional oscillator is obtained by generalizing the corresponding equation of motion of a driven harmonic oscillator to include integrals of arbitrary order according to the methods of fractional calculus. The Green's function solution for the fractional oscillator is obtained in terms of Mittag-Leffler functions using Laplace transforms. The response and resonance characteristics of the fractional oscillator are studied for several cases of forcing function.

Narahari Achar, B. N.; Hanneken, John W.; Clarke, T.

2002-06-01

124

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

125

Vibration-Induced Motor Responses of Infants With and Without Myelomeningocele  

PubMed Central

Background The severity of myelomeningocele (MMC) stems both from a loss of neurons due to neural tube defect and a loss of function in viable neurons due to reduced movement experience during the first year after birth. In young infants with MMC, the challenge is to reinforce excitability and voluntary control of all available neurons. Muscle vibration paired with voluntary movement may increase motoneuron excitability and contribute to improvements in neural organization, responsiveness, and control. Objectives This study examined whether infants with or without MMC respond to vibration by altering their step or stance behavior when supported upright on a treadmill. Design This was a cross-sectional study. Methods Twenty-four 2- to 10-month-old infants, 12 with typical development (TD) and 12 with MMC (lumbar and sacral lesions), were tested. Infants were supported upright with their feet in contact with a stationary or moving treadmill during 30-second trials. Rhythmic alternating vibrations were applied to the right and left rectus femoris muscles, the lateral gastrocnemius muscle, or the sole of the foot. Two cameras and behavior coding were used to determine step count, step type, and motor response to vibration onset. Results Step count decreased and swing duration increased in infants with TD during vibration of the sole of the foot on a moving treadmill (FT-M trials). Across all groups the percentage of single steps increased during vibration of the lateral gastrocnemius muscle on a moving treadmill. Infants with MMC and younger infants with TD responded to onset of vibration with leg straightening during rectus femoris muscle stimulation and by stepping during FT-M trials more often than older infants with TD. Conclusions Vibration seems a viable option for increasing motor responsiveness in infants with MMC. Follow-up studies are needed to identify optimal methods of administering vibration to maximize step and stance behavior in infants.

Teulier, Caroline; Smith, Beth A.; Kim, Byungji; Beutler, Benjamin D.; Martin, Bernard J.; Ulrich, Beverly D.

2012-01-01

126

Model-based dynamic compensation of load cell response in weighing machines affected by environmental vibrations  

NASA Astrophysics Data System (ADS)

This work proposes and validates experimentally a model-based scheme for the compensation of environmental vibrations affecting load cell measurements in automatic weighing machines. Weighing machines are often adversely affected by low frequency vibrations which may arise from the coupled effects of machine frame flexibility and the excitation induced by internal (inertial) or external (impact) vibration sources. These vibrations are generally named "environmental vibrations", since they seem to arise from the environment around the machine. Environmental vibrations have a detrimental effect on load cell responses and can in turn deteriorate machine performances. It is usually ineffective to try overcoming this problem by low-pass filtering load cell measurements: low cut-off frequencies usually downgrade machine speed by both introducing delay and increasing filtered signal rise time. Since automatic weighing machines need to operate at ever increasing speed, alternative approaches must be investigated. In this work it is suggested to make use of the mechanical models of the weighing machine and the load cells to process supplementary accelerometer measurements and compute an effective compensation of the effect of environmental vibrations on load cell response. The technique is here applied to a multi-head weighing machine in order to prove its effectiveness and implementability in industrial devices with real-time controllers.

Boschetti, Giovanni; Caracciolo, Roberto; Richiedei, Dario; Trevisani, Alberto

2013-01-01

127

Nonlinear response of vibrational excitons: Simulating the two-dimensional infrared spectrum of liquid water  

PubMed Central

A simulation formalism for the nonlinear response of vibrational excitons is presented and applied to the OH stretching vibrations of neat liquid H2O. The method employs numerical integration of the Schrödinger equation and allows explicit treatment of fluctuating transition frequencies, vibrational couplings, dipole moments, and the anharmonicities of all these quantities, as well as nonadiabatic effects. The split operator technique greatly increases computational feasibility and performance. The electrostatic map for the OH stretching vibrations in liquid water employed in our previous study [A. Paarmann et al., J. Chem. Phys. 128, 191103 (2008)] is presented. The two-dimensional spectra are in close agreement with experiment. The fast 100 fs dynamics are primarily attributed to intramolecular mixing between states in the two-dimensional OH stretching potential. Small intermolecular couplings are sufficient to reproduce the experimental energy transfer time scales. Interference effects between Liouville pathways in excitonic systems and their impact on the analysis of the nonlinear response are discussed.

Paarmann, A.; Hayashi, T.; Mukamel, S.; Miller, R. J. D.

2009-01-01

128

Dynamic Response of the Standing Human Body Exposed to Vertical Vibration: Influence of Posture and Vibration Magnitude  

NASA Astrophysics Data System (ADS)

The influence of the posture of the legs and the vibration magnitude on the dynamic response of the standing human body exposed to vertical whole-body vibration has been investigated. Motions were measured on the body surface at the first and eighth thoracic and fourth lumbar vertebrae (T1, T8 and L4), at the right and left iliac crests and at the knee. Twelve subjects took part in the experiment with three leg postures (normal, legs bent and one leg), and five magnitudes of random vibration (0·125-2·0 ms-2r.m.s.) in the frequency range from 0[msde]5-30 Hz. The main resonance frequencies of the apparent masses at 1·0 ms-2r.m.s. differed between postures: 5·5 Hz in the normal posture, 2·75 Hz in the legs bent posture and 3·75 Hz in the one leg posture. In the normal posture, the transmissibilities to L4 and the iliac crests showed a similar trend to the apparent mass at low frequencies. With the legs straight, no resonance was observed in the legs at frequencies below 15 Hz. In the legs bent posture, a bending motion of the legs at the knee and a pitching or bending motion of the upper-body appeared to contribute to the resonance of the whole body as observed in the apparent mass, with attenuation of vibration transmission to the upper body at high frequencies. In the one leg posture, coupled rotational motion of the whole upper-body about the hip joint may have contributed to the resonance observed in the apparent mass at low frequencies and the attenuation of vertical vibration transmission at high frequencies. The resonance frequency of the apparent mass in the normal posture decreased from 6·75-5·25 Hz with increasing vibration magnitude from 0·125 to 2·0 ms-2r.m.s. This “softening” effect was also found in the transmissibilities to many parts of the body that showed resonances.

Matsumoto, Y.; Griffin, M. J.

1998-04-01

129

Evaluation of human response to structural vibration induced by sonic boom  

NASA Technical Reports Server (NTRS)

This paper addresses the topic of building vibration response to sonic boom and the evaluation of the associated human response to this vibration. The paper reexamines some of the issues addressed in the previous extensive coverage of the topic, primarily by NASA, and attempts to offer a fresh viewpoint for some of the problems that may assist in reassessing the potential impact of sonic boom over populated areas. The topics addressed are: (1) human response to vibration; (2) criteria for, and acoustic signature of rattle; (3) structural response to shaped booms, including definition of two new descriptors for assessing the structural response to sonic boom; and (4) a detailed review of the previous NASA/FAA Sonic Boom Test Program involving structural response measurements at Edwards AFB and an initial estimate of structural response to sonic booms from possible high speed civil transport configurations. Finally, these estimated vibration responses are shown to be substantially greater than the human response and rattle criteria developed earlier.

Sutherland, L. C.; Czech, J.

1992-01-01

130

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

131

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

132

On the response and wake modes of a cylinder undergoing streamwise vortex-induced vibration  

NASA Astrophysics Data System (ADS)

This brief communication elaborates on aspects of the free response and wake modes of a flexibly-supported cylinder undergoing vortex-induced vibration in the streamwise direction only in view of some recent studies in the literature. It discusses the meaning of the term 'lock-in' employed in the context of forced excitation and free response studies, the influence of added mass on the response frequency, the competition between alternating and symmetrical modes and associated excitation mechanisms, and the drop in amplitude in the range separating the two response branches. A few similarities between single-degree-of-freedom streamwise and transverse vibrations are brought to light. Finally, attention is drawn to some discrepancies between published results which call for further understanding of the complicated nature of vortex-induced vibration.

Konstantinidis, Efstathios

2014-02-01

133

The Influence of Ethanol–Gasoline Blends on Spark Ignition Engine Vibration Characteristics and Noise Emissions  

Microsoft Academic Search

Engine vibration characteristics and noise emission of a two stroke spark ignition engine were investigated by using blends of ethanol–gasoline–oil (25% E–70% G–5% O and 50% E–45% G–5% O) and pure gasoline. Engine test conditions were 0.86 kW (5.5 Nm) at 1,500 rpm, 1.25 kW (6.0 Nm) at 2,000 rpm, and 1.83 kW (7.0 Nm) at 2,500 rpm. A high

A. Keskin

2010-01-01

134

Characteristics of ultrasonic vibration-assisted ductile mode cutting of tungsten carbide  

Microsoft Academic Search

In this study, investigations were carried out to evaluate the characteristics of ultrasonic vibration-assisted cutting of\\u000a tungsten carbide material using a CNC lathe with CBN tool inserts. The cutting forces were measured using a three-component\\u000a dynamometer, and the machined workpiece surfaces and chip formation were examined using a SEM. The experimental results showed\\u000a that the radial force F\\u000a \\u000a x\\u000a was

K. Liu; X. P. Li; M. Rahman

2008-01-01

135

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

136

Measurements of an ARS DE204S Cryocooler's Thermal and Vibration Characteristics  

SciTech Connect

This document describes measurements that characterize an Advanced Research Systems DE204S cryocooler system. The data is relevant to the thermal performance and vibration characteristics of the cold-head. The thermal measurements include heat load mapping of the 1st and 2nd stage, and temperature fluctuation measurement of the 2nd stage heat station. A comparison of fluctuation measurements by four different sensors is also included to support the 2nd stage fluctuation results. Finally, optical measurement of the cyclic 2nd stage heat station deflection is described.

Haid, B

2004-08-24

137

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

138

Visual Stimulation Facilitates Penile Responses to Vibration in Men with and without Erectile Disorder.  

ERIC Educational Resources Information Center

Compared reflexogenic and psychogenic penile responses in men with and without erectile disorder. Hypothesized that men with psychogenic dysfunction respond minimally to vibrotactile stimulation. As predicted, responses were different in the vibration condition. Interpretations are provided in terms of attention and appraisal. (BF)

Janssen, Erick; And Others

1994-01-01

139

Vibrational response prediction of a pneumatic tyre using an orthotropic two-plate wave model  

Microsoft Academic Search

A wave model to predict the vibrational response of a pneumatic tyre subject to line force excitation is presented. The tread and sidewalls are each modelled as thin, flat orthotropic plates with in-plane tension, which are joined together by a translational stiffness, and to a rigid rim. The dynamic response of the tyre to harmonic excitation is decomposed into spatial

J. M. Muggleton; B. R. Mace; M. J. Brennan

2003-01-01

140

Biodynamic response of the hand-arm system to vibration from an impact hammer and a grinder  

Microsoft Academic Search

The dynamic response of the hand\\/arm system due to exposure of two types of vibrations, one from an impact hammer and one from a grinder, were studied. The aim of the investigation was to study whether the dynamic response was dependent of the type of exposure and\\/or the frequency of the vibration. The dynamic responses studied were driving point impedance,

Steve Kihlberg

1995-01-01

141

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

PubMed Central

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 vibration were interviewed with health and workplace assessment questionnaires. The diagnosis of vibration induced white finger (VWF) was made on the basis of subjective symptoms of finger blanching and the results of a cold test with plethysmographic measurement of systolic blood pressure of the finger. Vibration was measured on a representative sample of AV and non-AV chain saws. Daily vibration exposure was assessed as eight hour energy equivalent frequency weighted acceleration (A(8)). A lifetime vibration dose was estimated for each of the forestry workers. RESULTS--The overall prevalence of VWF among the forestry workers was 23.4%. The diagnosis of VWF was made in 13.4% of the forestry workers who handled only AV chain saws and in 51.7% of those who had also operated non-AV chain saws in the past. Raynaud's phenomenon was found in 2.6% of the controls. In the forestry workers, the risk for VWF showed positive increments with each increment of vibration dose, suggesting a monotonic dose-response relation. The responsiveness to cold in the digital arteries of the forestry workers was also found to increase with increasing vibration dose and severity of VWF. The estimated relation between VWF and vibration exposure showed that the expected prevalence of VWF increased almost linearly to either A(8) (with exposure duration unchanged) or the number of years of exposure (with equivalent acceleration unchanged). CONCLUSIONS--In this study of VWF among forestry workers, the estimated dose-response relation showed that if the magnitude of vibration acceleration is doubled, the total duration of exposure should be halved to produce an equivalent effect. On the basis of the assessment of vibration exposure, the estimated risk for VWF in the study population was found to be lower than that predicted by the international standard ISO 5349. These findings suggest a revision of the risk estimates for VWF currently provided by ISO 5349.

Bovenzi, M; Franzinelli, A; Mancini, R; Cannava, M G; Maiorano, M; Ceccarelli, F

1995-01-01

142

High Efficiency of Optimization of Response Surface Method for Structure Dynamic Characteristics by Using Perturbation Method with Complementary Term  

NASA Astrophysics Data System (ADS)

In this paper, a new perturbation method is proposed, and is shown that the correction vector can be calculated shorter than ever. And, the computing efficiency of the response surface optimization method could improve greatly by applying perturbation method with complementary term to example analysis in the optimization of vibration characteristics by the response surface methodology and by finishing eigenvalue analysis which takes most computing time just once. Moreover, the validity and effectiveness is examined by examples by inducing approximately estimated formula of the vibration response value based on orthogonal polynomial. Lastly, it is shown that the computing time is shorten greatly compared with former method by applying this method to analysis of optimization problem of vibration characteristics.

Zhao, Xilu; Terane, Teppei; Shin, Hyunjin; Hagiwara, Ichiro

143

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

144

Vibrational bone characteristics versus bone density for the assessment of osteoporosis in ovariectomized rats.  

PubMed

Our previous research findings suggested this integrated study in order to monitor changes of bone properties and assess bone integrity using vibrational characteristics in osteoporosis. The method is based on measurement of the bone dynamic characteristic modal damping factor (MDF). The experimental animal model is ovariectomized rat followed by alendronate treatment. According to the experimental design, adult female Wistar rats are ovariectomized and 60 days later, with confirmed osteoporosis, the population is divided into two groups. One is administered alendronate and the second is given no treatment. Furthermore, established techniques such as pQCT and histomorphometry are applied at all time points, in order to compare and correlate to MDF. The results indicate induction of osteoporosis due to ovariectomy and render MDF capable of monitoring changes in bone material properties and architecture, with high sensitivity and repeatability. PMID:19995148

Anastassopoulos, G; Panteliou, S; Christopoulou, G; Stavropoulou, A; Panagiotopoulos, E; Lyritis, G; Khaldi, Lubna; Varakis, J; Karamanos, N

2010-01-01

145

EVALUATION ON ARCH DAMS CONSIDERING NONLINEAR BEHAVIOR OF TRANSVERSE JOINTS ON VIBRATION CHARACTERISTICS AND STATIC BEHAVIOR  

NASA Astrophysics Data System (ADS)

Thin structures of the arch dams are influenced by the interaction of foundational rock and reservoir. In this research, transverse joints have been confirmed to open and slip. In each dam site, a dam body shape has wide variety shape, however that dam body shape effect on static behavior has not been clarified. In this paper, an analytical model considering the nonlinear characteristics of the transverse joints is built, and a symmetric and asymmetric model is modeled as the three dimensional models which have a dam body - foundational rock - reservoir system. In order to find out a vibration characteristics and resistance mechanism, each model is analyzed by the eigenvalue analysis and static behavior analysis.

Mazda, Taiji; Okuma, Nobuyuki; Endo, Yohei; Kandemir, Elif Cargda

146

Nonlinear finite element analysis of the vibration characteristics of the maxillary central incisor related to periodontal attachment  

Microsoft Academic Search

The vibration characteristics of a maxillary central incisor were investigated by using the finite element method (FEM) according\\u000a to nonlinear behavior of the human periodontal ligament (PDL). The effect of alveolar bone loss was also studied to obtain\\u000a the relationship between the vibration property of the tooth in the periodontal system and the level of periodontal attachment\\u000a for assessing the

Haitao Xin; Yulong Li; Lingcheng Zhao; Weiguo Guo

2009-01-01

147

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

148

Multidimensional Decomposition of Time-Varying Vibration Response Signals in Rotating Machinery  

NASA Astrophysics Data System (ADS)

A new method for decomposition of speed-dependent vibration signals measured on rotating machinery is presented. The method uses a number of measured signals from an array of sensors to decompose the vibration response into: (1) the direction of the progression of motion; (2) its frequency content; (3) the various wavelengths; and (4) speed of rotation (or time). For the simple case of shaft vibration, two sensors spaced at 90° are required to separate the vibration pattern into forward- and backward-travelling components. For the case of a rotating disc, more sensors are required to decompose the response further into different spatial wavelengths and their directions of progression. This decomposition of the response allows monitoring and identification of potentially dangerous vibration patterns which exhibit large backward- or forward-progressing components. The new method is shown to provide better resolution in the time-frequency (speed-frequency) representation where usually overlapping patterns are separated. Several analytical and experimental results that demonstrate the usefulness of the proposed method are shown.

Bucher, I.; Ewins, D. J.

1997-07-01

149

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.

150

Measurement of high solidity vertical axis wind turbine aerodynamic loads under high vibration response conditions  

NASA Astrophysics Data System (ADS)

A series of full-scale experimental wind tunnel tests were performed to determine the aerodynamic loading behaviour on the airfoils of a high solidity, H-type, vertical axis wind turbine. During the course of this investigation, high amplitude vibration of the turbine was observed over a wide range of test conditions. The primary vibration excitation mechanism was resonance of the dominant whirling mode of the turbine with the operating blade pass frequency. In addition, for a significant number of test cases, resonance of the airfoil support struts at higher frequencies was also observed. This large vibration response resulted in conditions that made it difficult or impossible to measure the underlying aerodynamic loading. As a result, in order to gain a greater understanding of the aerodynamic loading, a vibration isolation methodology was developed to remove the effect of vibration from the measured aerodynamic forces on the blades. This included tests with two different support shaft end conditions over a range of flow velocities from 8 to 11 m/s, and the use of band-stop filtering to remove residual small amplitude vibrations. In this way, an accurate and complete measurement of the aerodynamic loading on the turbine blades could be obtained to better understand the effects of dynamic stall and validate the results of numerical model predictions.

McLaren, K.; Tullis, S.; Ziada, S.

2012-07-01

151

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

152

Suppression of Subsynchronous Vibrations Due to Aerodynamic Response to Surge in a Two-Stage Centrifugal Compressor with Air Foil Bearings  

Microsoft Academic Search

An investigation was conducted on the suppression of subsynchronous vibrations due to aerodynamic response to surge in a two-stage centrifugal compressor with air foil bearings. Unsteady aerodynamic response to surge caused excessive subsynchronous shaft vibration which might result in reduced bearing life. Notably, subsynchronous vibrations associated with rigid mode frequencies were more severe than any other subsynchronous vibrations. The objective

Y. B. Lee; T. H. Kim; C. H. Kim; N. S. Lee

2003-01-01

153

Design and Operation of a Vibration-Acoustic-Thermal Apparatus for Identifying Variations in Free and Forced Response of Sandwich Panels Due to Combined Loading  

NASA Astrophysics Data System (ADS)

Combined vibration, thermal, and acoustic environments cause significant changes in the free and forced response characteristics of spacecraft metallic, ceramic, and carbon thermal protection systems, exhaust wash structures in fixed wing aircraft, and ground vehicle components exposed to blast loading. When structural components become damaged, the effects of combined loads are even more apparent on the structural response. A new combined vibration-acoustic-thermal apparatus designed to simultaneously expose specimens up to 4' by 4' with 10 g vibration up to either 100 Hz or 1 inch displacement vibrations, 140 dB acoustic pressures, and >400 °F temperatures will first be described in this paper. Then observations from experiments conducted on a sandwich metallic panel exposed to thermal loads will be described. Modal impact and active sensor data will be utilized to extract frequency response function models that change as a function of the loading. These frequency response models indicate significant changes in the free response properties of the panel. For example, it will be shown that temperature changes cause the resonant frequencies of the panel to decrease resulting in higher response amplitudes. Likewise, acoustic pressure loads distributed across the panel will be shown to change as a function of temperature.

Ellmer, Claudia; Adams, Douglas E.; White, Jonathan R.; Jata, Kumar

2008-02-01

154

Vibration suppression of a hard disk driver actuator arm using piezoelectric shunt damping with a topology-optimized PZT transducer  

Microsoft Academic Search

The actuator system of a hard disk drive (HDD) is very sensitive to vibration circumstances. It is of great importance to study the dynamic characteristics of the actuator system and to control its vibration response. Piezoelectric shunt damping is an emerging vibration suppression technique used to control structural vibration. In this paper, two methods are proposed to improve vibration damping

Hao Sun; Zhichun Yang; Kai Xiang Li; Bin Li; Jiang Xie; Dan Wu; Ling Ling Zhang

2009-01-01

155

Thermally induced vibrations of piezo-thermo-viscoelastic composite beam with relaxation times and system response  

Microsoft Academic Search

Purpose – The purpose of this paper is to present numerical studies on thermally induced vibrations of piezo-thermo-viscoelastic composite beam subjected to a transient thermal load using coupled finite element method. Design\\/methodology\\/approach – The thermal relaxation and viscoelastic relaxations are taken into consideration to obtain the system response. The concept of “memory load” along with the thermal relaxation is accounted

Sharnappa; N. Ganesan; Raju Sethuraman

2010-01-01

156

Free Vibration Response Comparison of Composite Beams with Fluid Structure Interaction.  

National Technical Information Service (NTIS)

The analysis of the dynamic response of a vibrating structure in contact with a fluid medium can be interpreted as an added mass effect known as the Fluid Structure Interaction (FSI) problem. This effect is critical in the study of composites for marine a...

E. M. Priest

2012-01-01

157

Biodynamic Response at the Palm of the Human Hand Subjected to a Random Vibration  

Microsoft Academic Search

This study investigated the biodynamic response (BR) distributed at the palm of the hand subjected to a random vibration. Twelve male subjects were used in the experiment. Each subject applied three coupling actions (grip-only, push-only, and combined grip and push) on a simulated tool handle at three different levels (50, 75, and 100 N) of palm force. This study found

Ren G. DONG; Thomas W. McDOWELL; Daniel E. WELCOME

2005-01-01

158

A Scaling Law for Vibration Response of Laminated Doubly Curved Shallow Shells by Energy Approach  

Microsoft Academic Search

This research paper derives the scaling law for physical modeling of generally laminated doubly curved shallow shells for free vibration response by applying the similitude transformation to the governing total energy of the system. Validity of the scaling law is verified by numerical experiments on laminated doubly curved shallow shells. This is accomplished by calculating theoretically the natural frequencies for

Variddhi Ungbhakorn; Pairod Singhatanadgid

2009-01-01

159

Vibration and dynamic response control of adaptive cantilevers carrying externally mounted stores  

NASA Astrophysics Data System (ADS)

The vibrational and dynamic response control of cantilevers carrying externally mounted stores is investigated. The cantilevered structure is modeled as a thin-walled beam of arbitrary cross-section and incorporates a number of non- classical effects such as transverse shear, secondary warping, anisotropy of constituent materials and heterogeneity of the construction. The control is carried out via a dynamic bending moment applied at the tip of the structure. A feedback control law relating the boundary moment with one of the kinematical variables characterizing the response of the beam is implemented, and its results upon the closed-loop eigenfrequencies and dynamic response are highlighted. The obtained numerical results emphasize the efficiency of this control methodology to enhance, without weight penalties, vibrational and dynamic response behavior and inhibit and even suppress the occurrence of the resonance phenomenon.

Librescu, Liviu I.; Na, Sungsoo

1997-06-01

160

Minimizing vibration response of cylindrical shells through layout optimization of passive constrained layer damping treatments  

Microsoft Academic Search

A layout optimization of passive constrained layer damping (PCLD) treatment for minimizing the vibration response of cylindrical shells is presented with consideration of broadband transverse force excitation. The equations governing the displacement responses, relating the integrated out-of-plane displacement over the whole structural volume, i.e., the structural volume displacement (SVD), of a cylindrical shell to structural parameters of base structure and

H. Zheng; C. Cai; G. S. H. Pau; G. R. Liu

2005-01-01

161

Study on the Vibrational Characteristics of a Tube Array Caused by Two-Phase Flow. Part I: Random Vibration  

Microsoft Academic Search

There are few published papers on the subject of flow-induced vibrations caused by two-phase flow. Experimental data at the high pressure and temperature conditions which would correspond to practical operating conditions are extremely few. Furthermore, the mechanism of the two-phase flow-induced load acting on a tube in a tube array has not yet been explained. This paper presents the experimental

T. Nakamura; K. Fujita; K. Kawanishi; N. Yamaguchi; A. Tsuge

1995-01-01

162

Study on the Vibrational Characteristics of a Tube Array Caused by Two-Phase Flow. Part II: Fluidelastic Vibration  

Microsoft Academic Search

Fluidelastic vibration of tube arrays caused by two-phase flow has been studied before. The critical flow velocity is usually estimated with a simple Connors-type criterion which is based on an average flow velocity, an average fluid mass density and damping in two-phase flow. However, there is no explanation of why this simple criterion is applicable or how fluidelastic instability occurs

T. Nakamura; K. Fujita; K. Kawanishi; N. Yamaguchi; A. Tsuge

1995-01-01

163

Experimental studies for determining human discomfort response to vertical sinusoidal vibration  

NASA Technical Reports Server (NTRS)

A study was conducted to investigate several problems related to methodology and design of experiments to obtain human comfort response to vertical sinusoidal vibration. Specifically, the studies were directed to the determination of (1) the adequacy of frequency averaging of vibration data to obtain discomfort predictors, (2) the effect of practice on subject ratings, (3) the effect of the demographic factors of age, sex, and weight, and (4) the relative importance of seat and floor vibrations in the determination of measurement and criteria specification location. Results indicate that accurate prediction of discomfort requires knowledge of both the acceleration level and frequency content of the vibration stimuli. More importantly, the prediction of discomfort was shown to be equally good based upon either floor accelerations or seat accelerations. Furthermore, it was demonstrated that the discomfort levels in different seats resulting from similar vibratory imputs were equal. Therefore, it was recommended that criteria specifications and acceleration measurements be made at the floor location. The results also indicated that practice did not systematically influence discomfort responses nor did the demographic factors of age, weight, and sex contribute to the discomfort response variation.

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

1975-01-01

164

Improvement of transient response of vibrating secondary mirror of Infrared Astronomy Telescope (IRAT)  

NASA Astrophysics Data System (ADS)

In this work, the problem of improving the transient response of a vibrating secondary mirror of IRAT with square input is considered. The secondary mirror held at the focus of the cassegrainian primary mirror of the telescope is vibrated at different frequencies so as to separate the signal from the background noise and other disturbances. However classical transient response problems put a limitation to the frequency with which the secondary mirror can be vibrated. Conventional PID tuning controllers are designed to minimize system transient errors, but it is not implemented due to the space limitation in the vicinity of the secondary mirror. Hence, another scheme, called Posicast control, which involves only modification of the input signal, is designed and implemented. The transient response is found to improve drastically allowing the output to reach steady-state in a much shorter time. The control has been designed and presented in a look-up table for all frequencies of vibration and for all amplitude levels, thereby effective tracking of distant celestial objects is made possible.

Sethupathi, Raja V.

1994-06-01

165

Effect of temporal area bone vibrator placement on auditory brain stem response in newborn infants.  

PubMed

The effect of bone conduction vibratory placement on the temporal area, revealed by the auditory brain stem response (ABR), in newborn infants, was investigated. Twenty-five full term neonates were tested at 48 to 72 hours postparturition. ABR wave V latencies were obtained from three different temporal area postauricular vibrator placements at 15 and 30 dB nHL stimulus intensity levels. Results showed that significant ABR wave V latency shifts were observed with changes in the three vibrator placements (p less than 0.05). It is suggested that, with ABR testing in newborn infants using bone conducted stimuli, bone vibrator placement on the temporal area remain consistent. PMID:2262086

Stuart, A; Yang, E Y; Stenstrom, R

1990-10-01

166

Short term response of insulin, glucose, growth hormone and corticosterone to acute vibration in rats.  

NASA Technical Reports Server (NTRS)

Study carried out to obtain some notion of the initial phasing and interactive effects among some hormones known to be responsive to vibration stress. Sprague-Dawley derived rats were exposed to the acute effects of confinement and confinement with lateral (plus or minus G sub y) vibration. The coincident monitoring of glucose, insulin, growth hormone, and corticosterone plasma levels, during and immediately subsequent to exposure to brief low level vibration, exhibits the effects of inhibition of insulin release by epinephrine. The ability of insulin (IRI) to return rapidly to basal levels, from appreciably depressed levels during vibration, in the face of elevated levels of glucose is also shown. Corticosterone responds with almost equal rapidity, but in opposite phase to the IRI. The immuno-assayable growth hormone (IGH) dropped from a basal level of 32 ng/ml to 7.3 ng/ml immediately subsequent to vibration and remained at essentially that level throughout the experiment (60 min). Whether these levels represent a real fall in the rat or whether they merely follow the immuno-logically deficient form is still in question.

Dolkas, C. B.; Leon, H. A.; Chackerian, M.

1971-01-01

167

Theoretical relationship between vibration transmissibility and driving-point response functions of the human body  

NASA Astrophysics Data System (ADS)

The relationship between the vibration transmissibility and driving-point response functions (DPRFs) of the human body is important for understanding vibration exposures of the system and for developing valid models. This study identified their theoretical relationship and demonstrated that the sum of the DPRFs can be expressed as a linear combination of the transmissibility functions of the individual mass elements distributed throughout the system. The relationship is verified using several human vibration models. This study also clarified the requirements for reliably quantifying transmissibility values used as references for calibrating the system models. As an example application, this study used the developed theory to perform a preliminary analysis of the method for calibrating models using both vibration transmissibility and DPRFs. The results of the analysis show that the combined method can theoretically result in a unique and valid solution of the model parameters, at least for linear systems. However, the validation of the method itself does not guarantee the validation of the calibrated model, because the validation of the calibration also depends on the model structure and the reliability and appropriate representation of the reference functions. The basic theory developed in this study is also applicable to the vibration analyses of other structures.

Dong, Ren G.; Welcome, Daniel E.; McDowell, Thomas W.; Wu, John Z.

2013-11-01

168

Effects of leg muscle tendon vibration on group Ia and group II reflex responses to stance perturbation in humans  

PubMed Central

Stretching the soleus (Sol) muscle during sudden toe-up rotations of the supporting platform in a standing subject evokes a short-latency response (SLR) and a medium-latency response (MLR). The aim of the present investigation was to further explore the afferent and spinal pathways mediating the SLR and MLR in lower limb muscles by means of tendon vibration. In seven subjects, toe-up or toe-down rotations were performed under: (1) control, (2) continuous bilateral vibration at 90 Hz of Achilles' tendon or tibialis anterior (TA) tendon, and (3) post-vibration conditions. Sol and TA background EMG activity and reflex responses were bilaterally recorded and analysed. Toe-up rotations induced SLRs and MLRs in Sol at average latencies of 40 and 66 ms, respectively. During vibration, the latency of both responses increased by about 2 ms. The area of the SLR significantly decreased during vibration, regardless of the underlying background activity, and almost returned to control value post-vibration. The area of Sol MLR was less influenced by vibration than SLR, the reduction being negligible with relatively high background activity. However, contrary to SLR, MLR was even more reduced post-vibration. Toe-down rotations induced no SLR in the TA, while a MLR was evoked at about 81 ms. The area of TA MLR decreased slightly during vibration but much more post-vibration. SLRs and MLRs were differently affected by changing the vibration frequency to 30 Hz: vibration had a negligible effect on the SLR, but still produced a significant effect on the MLR. The independence from the background EMG of the inhibitory effect of vibration upon the SLR suggests that vibration removes a constant amount of the Ia afferent input. This can be accounted for by either presynaptic inhibition of group Ia fibres or a ‘busy-line' phenomenon. The differential effect of vibration on SLRs and MLRs is compatible with the notions that spindle primaries have a higher sensitivity to vibration than secondaries, and that group II afferent fibres are responsible for the production of the MLR. The decrease of MLRs but not SLRs after vibration is discussed in terms of an interaction between peripheral and central drive on group II interneurones in order to produce sufficient EMG activity to maintain a given postural set.

Bove, Marco; Nardone, Antonio; Schieppati, Marco

2003-01-01

169

Numerical determination of the transmissibility characteristics of a squeeze film damped forced vibration system  

NASA Technical Reports Server (NTRS)

Numerical solutions of the governing equations of motion of a liquid squeeze film damped forced vibration system were carried out to examine the feasibility of using a liquid squeeze film to cushion and protect large structures, such as buildings, located in areas of high seismic activity. The mathematical model used was that for a single degree of freedom squeeze film damped spring mass system. The input disturbance was simulated by curve fitting actual seismic data with an eleventh order Lagranging polynomial technique. Only the normal component of the seismic input was considered. The nonlinear, nonhomogeneous governing differential equation of motion was solved numerically to determine the transmissibility over a wide range of physical parameters using a fourth-order Runge-Kutta technique. It is determined that a liquid squeeze film used as a damping agent in a spring-mass system can significantly reduce the response amplitude for a seismic input disturbance.

Sutton, M. A.; Davis, P. K.

1976-01-01

170

Free-Vibration Characteristics of a Large Split-Blanket Solar Array in a 1-G Field.  

National Technical Information Service (NTIS)

Two methods for studying the free vibration characteristics of a large split blanket solar array in both a 0-g and a 1-g cantilevered configuration are presented. The 0-g configuration corresponds to an in-orbit configuration of the array; the 1-g configu...

F. J. Shaker

1976-01-01

171

Non-linear dual-axis biodynamic response to fore-and-aft whole-body vibration  

Microsoft Academic Search

Seated subjects have participated in two experiments with fore-and-aft whole-body vibration to investigate dynamic responses at the seat and footrest in the direction of vibration and in other directions. In the first experiment, 12 males were exposed to fore-and-aft random vibration (0.25–20Hz) at four magnitudes (0.125, 0.25, 0.625, and 1.25ms?2 rms) while sitting on a seat with no backrest in

N. Nawayseh; M. J. Griffin

2005-01-01

172

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

173

DEFINITION OF A RANGE OF IDEALIZED VALUES TO CHARACTERIZE SEATED BODY BIODYNAMIC RESPONSE UNDER VERTICAL VIBRATION  

Microsoft Academic Search

While a considerable quantity of data has been published on driving-point mechanical impedance, apparent mass and seat-to-head transmissibility magnitude and phase characteristics of seated subjects under vertical whole-body vibration, significant variation is known to exist between various data sets. Such variations may be partly attributed to differences associated with the methodology, experimental conditions or subject population used by various investigators

P.-É. Boileau; X. Wu; S. Rakheja

1998-01-01

174

Free vibration characteristics of multiple load path blades by the transfer matrix method  

NASA Technical Reports Server (NTRS)

The determination of free vibrational characteristics is basic to any dynamic design, and these characteristics can form the basis for aeroelastic stability analyses. Conventional helicopter blades are typically idealized as single-load-path blades, and the transfer matrix method is well suited to analyze such blades. Several current helicopter dynamic programs employ transfer matrices to analyze the rotor blades. In this paper, however, the transfer matrix method is extended to treat multiple-load-path blades, without resorting to an equivalent single-load-path approximation. With such an extension, these current rotor dynamic programs which employ the transfer matrix method can be modified with relative ease to account for the multiple load paths. Unlike the conventional blades, the multiple-load-path blades require the introduction of the axial degree-of-freedom into the solution process to account for the differential axial displacements of the different load paths. The transfer matrix formulation is validated through comparison with the finite-element solutions.

Murthy, V. R.; Joshi, Arun M.

1986-01-01

175

Motor and perceptual responses to horizontal and vertical eye vibration in humans.  

PubMed

Previous studies have shown that low amplitude/high frequency mechanical vibration applied to the human eye muscles results in the illusory movement of a luminous spot fixated in total darkness. The aim of the present study was to investigate whether a vibration-induced motor response also occurs in eye muscles, and to check whether the visual illusions actually result from the proprioceptors being activated by the vibration, or whether they are simply due to the retinal slip induced by the reflex eye movement. The effects of the vibratory stimuli on the inferior rectus (IR) and lateral rectus (LR) muscles were evaluated by recording subjects' eye position changes. When applied to the IR muscle, vibration effectively elicited an upward visual illusion accompanied by a small downward ocular rotation, whereas when applied to the LR muscle, it also induced horizontal visual illusion, which was less frequent and weaker than the vertical one, but no ocular rotation. We concluded that visual illusions of this kind cannot be attributable to the retinal motion of the image of the fixated point. The difference between the vertical and horizontal vibratory motor responses is discussed as regards the particular role that oculo-muscular proprioception may play in the vertical muscles. PMID:9373693

Velay, J L; Allin, F; Bouquerel, A

1997-09-01

176

The effect of surface wave propagation on neural responses to vibration in primate glabrous skin.  

PubMed

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

177

Analyses of biodynamic responses of seated occupants to uncorrelated fore-aft and vertical whole-body vibration  

Microsoft Academic Search

The apparent mass and seat-to-head-transmissibility response functions of the seated human body were investigated under exposures to fore-aft (x), vertical (z), and combined fore-aft and vertical (x and z) axis whole-body vibration. The coupling effects of dual-axis vibration were investigated using two different frequency response function estimators based upon the cross- and auto-spectral densities of the response and excitation signals,

Santosh Mandapuram; Subhash Rakheja; Pierre Marcotte; Paul-Émile Boileau

2011-01-01

178

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

179

Dielectric response and vibrational energy relaxation in photoactive yellow protein: A molecular dynamics simulation study  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations of the dielectric response and vibrational energy relaxation (VER) from the chromophore to the protein and solvent environment following photoexcitation of photoactive yellow protein are presented. The computed protein response to photoexcitation appears prominently between times of 0.1 and 0.3 ps. Contributions from individual residues to this response are analyzed. The frequency-dependent VER rate also reveals dynamic coupling between the chromophore and residues that hydrogen bond to it. Resonances in the VER rate appear at frequencies comparable to the oscillations observed in recent fluorescence decay studies.

Gnanasekaran, Ramachandran; Leitner, David M.

2011-11-01

180

Vibration and dynamic response control of elastically tailored smart cantilevers of nonuniform cross-section  

NASA Astrophysics Data System (ADS)

The main purpose of this paper is to assess the implications of a number of effects of geometric and physical nature on the vibration control of adaptive cantilevers modeled as composite thin-walled beams and simulating an aircraft wing. It is considered that the cantilevered beam is exposed to a pressure pulse generated, among others, by a blast or sonic-boom. The features on which preponderance will be given in this study are related with the non-uniformity of the beam cross section in the spanwise direction, anisotropy of constituent materials, transverse shear and warping inhibition. In order to control the dynamic response, a dual approach based on structural tailoring and adaptive materials technology will be implemented. The numerical simulations provide a comprehensive picture of the synergistic implications of the application of both the tailoring technique and feedback control upon the vibration response of nonuniform cantilevers exposed to time- dependent external excitations.

Librescu, Liviu I.; Na, Sungsoo

2000-06-01

181

Influence of Ultrasonic Vibrations on the Static Friction Characteristics of a Rubber/Aluminum Couple  

NASA Astrophysics Data System (ADS)

A novel ultrasonic vibration approach is introduced into a chloroprene rubber/aluminum friction couple for improving the static friction properties between rubber and metal. Compared to the test results without vibrations, the static friction force of a chloroprene rubber/aluminum couple decreases observably, leading to the ultimate displacement of rubber. The values of the static friction force and ultimate displacement can be ultimately reduced to 23.1% and 50% of those without ultrasonic vibrations, respectively.

Cheng, Ting-Hai; Gao, Han; Bao, Gang

2011-12-01

182

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

183

Dynamic characteristics of the output light from a vibrating hole assisted fiber curl cord and its application to intrusion location  

NASA Astrophysics Data System (ADS)

When a hole assisted fiber (HAF) curl cord expands and contracts, the polarization direction of the light emitted from it rotates. A curl cord is divided into several sections by fixing it at several points. When the curl cord is flipped at a point within one of these sections, then vibration is observed with the characteristic frequency to the flipped section. The vibration period of a HAF curl cord can be detected by monitoring the light power emitted from the curl cord after passing through a polarizer. We confirmed theoretically and experimentally that the vibration period of the polarization change is proportional to the length of the section including the flipped point, which can be applied to intrusion location.

Tateda, Mitsuhiro; Mizushima, Akihiro

2014-05-01

184

Modeling and design strategies for the vibration response of turbine engine rotors  

Microsoft Academic Search

Efficient, novel design and analysis methods are presented for improving the structural performance of turbine engine rotors with respect to blade vibration response. For a bladed disk, the blades are intended to be identical; however, blade-to-blade structural irregularities, known as blade mistuning, in practice are unavoidable due to manufacturing tolerances and in-service wear. Even small levels of blade mistuning may

Sanghum Baik

2005-01-01

185

Seated occupant interactions with seat backrest and pan, and biodynamic responses under vertical vibration  

Microsoft Academic Search

The relative interactions of the seated occupants with an inclined backrest were investigated in terms of apparent mass (APMS) responses at the two driving-points formed by the buttock–seat pan and the upper body-backrest under exposure to broad-band and road-measured vertical vibration. The measurements were performed using 24 adult subjects seated with full contact with the back support and two different

S. Rakheja; I. Stiharu; H. Zhang; P.-É. Boileau

2006-01-01

186

SCUC With Hourly Demand Response Considering Intertemporal Load Characteristics  

Microsoft Academic Search

In this paper, the hourly demand response (DR) is incorporated into security-constrained unit commitment (SCUC) for economic and security purposes. SCUC considers fixed and responsive loads. Unlike fixed hourly loads, responsive loads are modeled with their intertemporal characteristics. The responsive loads linked to hourly market prices can be curtailed or shifted to other operating hours. The study results show that

Amin Khodaei; Mohammad Shahidehpour; Shaghayegh Bahramirad

2011-01-01

187

Dynamic characteristics of a cable-stayed bridge measured from traffic-induced vibrations  

NASA Astrophysics Data System (ADS)

This paper studies the dynamic characteristics of the Kao-Ping-Hsi cable-stayed bridge under daily traffic conditions. Experimental data were measured from a structural monitoring system, and system-identification techniques, such as the random decrement (RD) technique and Ibrahim time-domain (ITD) method, were adopted. The first five modes of the bridge were identified for their natural frequencies and damping ratios under different traffic loading conditions, in terms of root-mean-square (RMS) deck velocities. The magnitude of the torsion mode of the Kao-Ping-Hsi cable-stayed bridge is found to be one order-of-magnitude less than the transfer mode, and two orders-of-magnitude less than the vertical modes. Out results indicated that vibrations induced by traffic flow can be used as an indicator to monitor the health of the bridge due to their insensitivity to the natural frequencies of the cable-stayed bridge. Furthermore, the damping ratios may be used as a more sensitive indicator to describe the condition of the bridge.

Wang, Yun-Che; Chen, Chern-Hwa

2012-09-01

188

Influence of permanent magnets on vibration characteristics of a partially covered sandwich cantilever beam  

NASA Astrophysics Data System (ADS)

The shear strains of viscoelastic damping layers resulting from the attraction arrangement magnets on the constraining layers root are higher than those of the conventional passive constrained layer damping treatment (PCLD). Therefore, significant improvement of damping characteristics can be achieved by using the new class of magnetic constrained layer damping treatment (MCLD). This paper presents an analytical modelling to elucidate vibration attenuation mechanism of the MCLD. It is shown that the variation amplitude of viscoelastic damping layers shear angle at the root where permanent magnets are fitted is relatively high, producing relatively high dynamic magnetic force compared to the maximal force on the constraining layers. The dynamic magnetic force is strong enough to reduce the elastic potential energy of the constraining layers and the primary layer and enhances the dissipation energy of the damping layers. The rise in the ratio of the dissipation energy to the total system energy per cycle suppresses the resonance peak. Furthermore, influences of permanent magnets on resonance peaks for the first several modes under different physical and geometrical properties are evaluated. Such evaluations are used to determine the merits and limitations of the MCLD treatment and develop design guidelines.

Zheng, Huiming; Zeng, He

2004-07-01

189

Electrorheological vibration system  

NASA Astrophysics Data System (ADS)

The present paper is devoted to de3velopment and testing of an active vibration system. The system is intended for providing efficient motion of a piston in a hydraulic channel for creation of shocks and periodic vibrations in a low frequency range by means of the ER-valves based on an electrosensitive working me dium, i.e. electrorheological fluids. The latter manifests the electrorheological (ER) effect, i.e. a reversible change in the rheological characteristics of weak-conducting disperse compositions in the presence of constant and alternating electric fields. As a result of the experimental study of the dependence of viscoelastic properties of the ER-fluid on the magnitude and type of an electric field, the optimum dimensions of the vibrator and the its valves characteristics of the optimal electrical signal are determined. For control of an ER- vibrator having several valves we have designed a special type of a high-voltage two-channel impulse generator. Experiments were conducted at the frequencies ranged from 1- 10 Hz. It has been shown, that a peak force made 70% of the static force exercised by the vibrator rod. A phase shift between the input voltage and the load acceleration was less than 45 degree(s)C which allowed servocontrol and use of the vibrator for attendant operations. It was noted that a response of the vibrator to a stepwise signal has a delay only of several milliseconds.

Korobko, Evguenia V.; Shulman, Zinovy P.; Korobko, Yulia O.

2001-07-01

190

Modeling and design strategies for the vibration response of turbine engine rotors  

NASA Astrophysics Data System (ADS)

Efficient, novel design and analysis methods are presented for improving the structural performance of turbine engine rotors with respect to blade vibration response. For a bladed disk, the blades are intended to be identical; however, blade-to-blade structural irregularities, known as blade mistuning, in practice are unavoidable due to manufacturing tolerances and in-service wear. Even small levels of blade mistuning may cause severe increases in blade vibration amplitudes relative to those computed for the ideal, tuned rotor. Thus, the sensitivity of bladed disks to mistuning is a serious safety, readiness, and maintenance concern for turbine engines. Hereby, the effects of blade mistuning are systematically accounted for in searching for a reliable, robust rotor design; that is, a bladed disk less sensitive to mistuning. To this end, design analysis tools are developed for bladed disks. First, as an efficient tool for accurately predicting the vibration response of mistuned rotors, a previously developed reduced-order vibration modeling technique is extended to handle the case of mass mistuning. Even when mass mistuning occurs in small geometric regions of the blades, the enhanced technique can precisely capture free and forced vibration response of the mistuned rotors. Second, as a fast tool for approximately assessing mistuning sensitivity of rotors, a power flow analysis method is proposed. This approach enables the systematic estimation of vibration energy flow within a nominal rotor for excitation cases of interest. This dynamic information is then used to evaluate the robustness of the rotor design with respect to blade mistuning. These tools are incorporated into the design problem of finding an optimal disk geometry to achieve minimum weight while ensuring that blade stress levels of mistuned rotors are kept below a specified safety limit. In doing so, an optimum candidate satisfying the design constraints in an approximate sense is calculated quickly using the new power flow analysis method, and a more accurate optimization is then done running a Monte Carlo simulation using the reduced-order model. For representative bladed disk assemblies, the proposed design methodology is demonstrated to yield designs less sensitive to blade mistuning while having a reduced weight relative to the original design.

Baik, Sanghum

191

Analysis of Transformer Core Vibration Characteristics Using Modified Empirical Mode Decomposition  

Microsoft Academic Search

The empirical mode decomposition method can separate the transformer core vibration signal into finite modes, then disclose the running status of transformer, whereas, the decomposing results of core vibration are disturbed by the end distorting. To optimize the empirical mode decomposition, the time series modeling and predicting were introduced to extend the signal, and non-uniform B-spline curve was provided for

Weihua Xiong; Haipeng Pan

2009-01-01

192

Dynamic modal characteristics of transverse vibrations of cantilevers of parabolic thickness  

Microsoft Academic Search

This paper deals with free transverse vibrations of nonuniform homogeneous beams. Cantilevers of rectangular (or elliptical) cross-section with parabolic thickness variation, and cantilevers of circular cross-section with parabolic radius variation, are considered. Factoring their fourth order differential equations of transverse vibrations into a pair of second order differential equations leads to general solutions in terms of hypergeometric functions. Exact natural

Dumitru I. Caruntu

2009-01-01

193

Development of Tracking Error Frequency Response Function and Aircraft Ride Quality Design Criteria for Vertical and Lateral Vibration.  

National Technical Information Service (NTIS)

The report presents the results of a study of available experimental literature in order to more clearly define the shape of frequency response functions for human psychomotor performance under vertical and lateral vibration conditions. The performance fr...

J. W. Rustenburg

1971-01-01

194

A longitudinal study of vibration white finger, cold response of digital arteries, and measures of daily vibration exposure  

Microsoft Academic Search

Purpose  To investigate prospectively the relation between vibration-induced vascular disorders and measures of daily exposure to hand-transmitted\\u000a vibration (HTV).\\u000a \\u000a \\u000a \\u000a Methods  Two hundred and forty-nine HTV workers and 138 control men of the same companies participated in a 3-year follow-up study.\\u000a The diagnosis of vibration induced white finger (VWF) in the HTV workers and that of Raynaud’s phenomenon in the controls\\u000a was based

Massimo Bovenzi

2010-01-01

195

Multiple-vibrational-mode model for fiber-optic Raman gain spectrum and response function  

NASA Astrophysics Data System (ADS)

We describe a model for the stimulated Raman gain spectrum and the Raman response function in silica fiber using multiple vibrational modes. We base the model on previous spectroscopic data [J. Opt. Soc. Am. B 1, 652 (1984) and J. Opt. Soc. Am. B 6, 1159 (1989)] and extend an earlier proposed model [Appl. Opt. 21, 359 (1982)] by making use of an inhomogeneous distribution of damped oscillators. The model provides a simple analytical expression for the Raman response function and an expression for the Raman gain spectrum that is easy to evaluate numerically.

Hollenbeck, Dawn; Cantrell, Cyrus D.

2002-12-01

196

Parametric identification of a time-varying structure based on vector vibration response measurements  

NASA Astrophysics Data System (ADS)

The problem of parametric output-only identification of a time-varying structure based on vector random vibration signal measurements is considered. A functional series vector time-dependent autoregressive moving average (FS-VTARMA) method is introduced and employed for the identification of a "bridge-like" laboratory structure consisting of a beam and a moving mass. The identification is based on three simultaneously measured vibration response signals obtained during a single experiment. The method is judged against baseline modelling based on multiple "frozen-configuration" stationary experiments, and is shown to be effective and capable of accurately tracking the dynamics. Additional comparisons with a recursive pseudo-linear regression VTARMA (PLR-VTARMA) method and a short time canonical variate analysis (ST-CVA) subspace method are made and demonstrate the method's superior achievable accuracy and model parsimony.

Spiridonakos, M. D.; Fassois, S. D.

2009-08-01

197

Modeling “unilateral” response in the cross-ties of a cable network: Deterministic vibration  

NASA Astrophysics Data System (ADS)

Cross-ties are employed as passive devices for the mitigation of stay-cable vibrations, exhibited on cable-stayed bridges under wind and wind-rain excitation. Large-amplitude oscillation can result in damage to the cables or perceived discomfort to bridge users. The “cable-cross-ties system” derived by connecting two or more stays by transverse cross-ties is often referred to as an “in-plane cable network”. Linear modeling of network dynamics has been available for some time. This framework, however, cannot be used to detect incipient failure in the restrainers due to slackening or snapping. A new model is proposed in this paper to analyze the effects of a complete loss in the pre-tensioning force imparted to the cross-ties, which leads to the “unilateral” free-vibration response of the network (i.e., a cross-tie with linear-elastic internal force in tension and partially inactive in compression). Deterministic free vibrations of a three-cable network are investigated by using the “equivalent linearization method”. A performance coefficient is introduced to monitor the relative reduction in the average (apparent) stiffness of the connector during free vibration response (“mode by mode”), exhibiting unilateral behavior. A reduction of fifty percent in the apparent stiffness was observed in the cross-tie when the pre-tensioning force is small in comparison with the tension force in the stay. This coefficient may be used as a damage indicator for the selection of the initial pre-tensioning force in the cross-ties needed to avoid slackening.

Giaccu, Gian Felice; Caracoglia, Luca; Barbiellini, Bernardo

2014-09-01

198

Analyses of biodynamic responses of seated occupants to uncorrelated fore-aft and vertical whole-body vibration  

NASA Astrophysics Data System (ADS)

The apparent mass and seat-to-head-transmissibility response functions of the seated human body were investigated under exposures to fore-aft ( x), vertical ( z), and combined fore-aft and vertical ( x and z) axis whole-body vibration. The coupling effects of dual-axis vibration were investigated using two different frequency response function estimators based upon the cross- and auto-spectral densities of the response and excitation signals, denoted as H1 and Hv estimators, respectively. The experiments were performed to measure the biodynamic responses to single and uncorrelated dual-axis vibration, and to study the effects of hands support, back support and vibration magnitude on the body interactions with the seatpan and the backrest, characterized in terms of apparent masses and the vibration transmitted to the head. The data were acquired with 9 subjects exposed to two different magnitudes of vibration applied along the individual x- and z-axis (0.25 and 0.4 m/s 2 rms), and along both the axis (0.28 and 0.4 m/s 2 rms along each axis) in the 0.5-20 Hz frequency range. The two methods resulted in identical single-axis responses but considerably different dual-axis responses. The dual-axis responses derived from the Hv estimator revealed notable effects of dual-axis vibration, as they comprised both the direct and cross-axis responses observed under single axis vibration. Such effect, termed as the coupling effect, was not evident in the dual-axis responses derived using the commonly used H1 estimator. The results also revealed significant effects of hands and back support conditions on the coupling effects and the measured responses. The back support constrained the upper body movements and thus showed relatively weaker coupling compared to that observed in the responses without the back support. The effect of hand support was also pronounced under the fore-aft vibration. The results suggest that a better understanding of the seated human body responses to uncorrelated multi-axis whole-body vibration could be developed using the power-spectral-density based Hv estimator.

Mandapuram, Santosh; Rakheja, Subhash; Marcotte, Pierre; Boileau, Paul-Émile

2011-08-01

199

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

200

Vibration characteristics in a smart bridge model using shape-memory alloy fiber reinforced composite  

Microsoft Academic Search

A smart bridge model was proposed for active control on strength and vibration by changing material properties of shape memory alloy embedded in the bridge structure using TiNi\\/acrylic composite. A systemic experimental study was carried out to investigate the self-strengthening effect by shape recovery of pre-strained TiNi wires as well as vibration control by stiffness changing with direct electric heating

A. Shimamoto; H. Zhao; H. Abe

2005-01-01

201

[Clinico-functional and morphological characteristics of the stomach in patients with vibration disease].  

PubMed

The contributors provide research data on the clinical manifestations, secretory and pepsinogenous function, morphological and histologic structures of stomach diseases caused by local vibration induced vibration disease. A correlation was established depending on the duration of work. As a result of clinico-functional and morphologic techniques used, no full correlation was traced between the stomach structure and function in VD patients, which seem to be of practical value for medical examination of workers engaged in unfavorable working conditions. PMID:2210422

Fidurov, Ia N; Chumachenko, P A; Ladneva, G A; Bakhovkina, O V

1990-01-01

202

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

NASA Technical Reports Server (NTRS)

A rich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for a curved orthogrid panel typical of launch vehicle skin structures. Several test article configurations were produced by adding component equipment of differing weights to the flight-like vehicle panel. 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 employed to describe the assumed correlation of phased input sound pressures across the energized panel. This application demonstrates 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 modules developed for the RPTF method can be easily adapted for quick replacement of the diffuse acoustic field with other pressure field models; for example a turbulent boundary layer (TBL) model suitable for vehicle ascent. Wind tunnel tests have been proposed to anchor the predictions and provide new insight into modeling approaches for this type of environment. Finally, component vibration environments for design were developed from the measured and predicted responses and compared with those derived from traditional techniques such as Barrett scaling methods for unloaded and component-loaded panels.

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

2011-01-01

203

The effect of vibration on postural response of Down syndrome individuals on the seesaw.  

PubMed

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 seesaws of different heights. The individuals with DS adopted a pattern of co-contraction and were not able to modulate the magnitude of postural response with the seesaw's height. The vibration affected neither the ability of individuals with DS to maintain balance nor the pattern of muscle contraction. On the other hand the control group changed the strategy with vibration, adopting one similar to that used by individuals with DS. Collectively, our findings suggest that proprioceptive information is essential for the motor control system to select the appropriate motor strategy of reciprocal activation among the agonist and antagonist to efficiently balance. Also, these findings suggest that a proprioceptive deficit could explain the atypical motor strategy observed in individuals with DS during balance on seesaw. PMID:19394195

Carvalho, Regiane Luz; Almeida, Gil Lúcio

2009-01-01

204

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

205

Seated occupant interactions with seat backrest and pan, and biodynamic responses under vertical vibration  

NASA Astrophysics Data System (ADS)

The relative interactions of the seated occupants with an inclined backrest were investigated in terms of apparent mass (APMS) responses at the two driving-points formed by the buttock-seat pan and the upper body-backrest under exposure to broad-band and road-measured vertical vibration. The measurements were performed using 24 adult subjects seated with full contact with the back support and two different positions of the hands (in lap and on steering wheel), while exposed to three different levels of broad band (0.25, 0.5 and 1.0 m/s 2 rms acceleration) vibration in the 0.5-40 Hz frequency range, and a track-measured vibration spectrum (1.07 m/s 2 rms acceleration). The forces developed on the seat pan and the backrest in directions normal to the supporting surfaces were measured to derive the APMS responses at both the driving-points. The results showed significant interactions of the upper body with the back support in a direction normal to the backrest, even though the vibration is applied along the vertical axis. At low frequencies, the backrest APMS magnitude was smaller than that measured at the seat pan, but it either exceeded or approached that of the seat pan APMS in the vicinity of the primary resonant frequencies. The results also suggested considerable effect of the hands position on the APMS magnitudes measured at both the driving-points. The effects of variations in the excitation type and magnitude, considered in this study, were observed to be small compared to those caused by the hands position and individual body masses. Owing to the strong effects of the body mass on the measured APMS responses at both driving-points, a total of 8 target data sets were identified corresponding to four mass groups (<60, 60.6-70, 70.5-80 and >80 kg) and two hands positions for formulating mechanical equivalent models. The model parameters identified for the target functions suggested that the models mass, stiffness and damping parameters increase with increasing body mass. The observed variations in the identified parameters could be applied for predicting the APMS responses reflected on the pan as well as backrest of the human occupants with specific body mass.

Rakheja, S.; Stiharu, I.; Zhang, H.; Boileau, P.-É.

2006-12-01

206

Experimental and numerical investigations of vibration characteristics for parallel-type and series-type triple-layered piezoceramic bimorphs.  

PubMed

The dynamic characteristics of parallel-type and series-type piezoelectric bimorphs are analyzed in this study. The transverse (out-of-plane) and planar (in-plane) vibrations for piezoceramic bimorphs in normal and abnormal connections are investigated experimentally by 2 noncontact optical techniques and impedance analyzer. Electronic speckle pattern interferometry (ESPI) is the major experimental technique for measuring the resonant frequency and corresponding vibration mode shape. Out-of-plane and in-plane vibrations of piezoelectric bimorphs at resonance are obtained by a self-arranged ESPI optical setup. The laser Doppler vibrometer (LDV) is a point-wise measurement technique for out-of-plane displacement and is used to determine the out-of-plane resonant frequencies. The impedance analyzer is used to measure the resonant frequencies for in-plane motions. It is noted from the experimental results that the out-of-plane modes are the dominant motion for the normal connection and only symmetric vibration mode shapes can be excited. The in-plane motions are large enough to be measured using the ESPI method for normal connections. The in-plane resonant modes are observed for parallel-type piezoelectric bimorph in parallel connections; however, the in-plane mode shapes are similar to the out-of-plane mode shapes for the series-type piezoelectric bimorph in series connection. Hence, the particle motions of the piezoelectric bimorph at resonance are essentially 3-D for the normal connection. It is interesting to note that both symmetric and asymmetric out-of-plane vibration mode shapes can be excited with large applied voltage but no in-plane motion is observed for the abnormal connection. In addition to experimental methods, numerical computations based on the finite element method are used to verify the experimental results. Good agreements of the resonant frequencies and mode shapes are obtained for experimental and numerical results. PMID:20040397

Huang, Yu-Hsi; Ma, Chien-Ching

2009-12-01

207

Stationary transducer response to planetary-gear vibration excitation II: Effects of torque modulations  

NASA Astrophysics Data System (ADS)

The frequency spectra of the outputs of transducers fixed to the ring gears of planetary-gear systems contain useful information pertaining to the health of such systems. The effects on such frequency spectra arising from non-uniform loading carried by the M planets in such systems was derived and illustrated in “Stationary transducer response to planetary-gear vibration excitation with non-uniform planet loading,” by Mark and Hines [W.D. Mark, J.A. Hines, Stationary transducer response to planetary-gear vibration excitation with non-uniform planet loading, Mechanical Systems and Signal Processing 23 (2009) 1366-1381]. The present paper extends this earlier analysis by predicting the added effects on such frequency spectra caused by planet-carrier torque modulations. It is shown that such torque modulations produce “sideband” harmonics on the harmonic contributions arising from uniform loading carried by the planets, and additional “sideband” harmonics on the harmonic contributions arising from the lack of uniformity of loading carried by the planets. An example is discussed for torque modulations with a period of 1/B times the planet-carrier rotation period. This example illustrates the effects of torque modulations on the transducer output spectra of a UH-60A rotorcraft with a B=4 blade rotor and M=5 planets.

Mark, W. D.

2009-10-01

208

Vibration responses of the organ of Corti and the tectorial membrane to electrical stimulation.  

PubMed

Coupling of somatic electromechanical force from the outer hair cells (OHCs) into the organ of Corti is investigated by measuring transverse vibration patterns of the organ of Cori and tectorial membrane (TM) in response to intracochlear electrical stimulation. Measurement places at the organ of Corti extend from the inner sulcus cells to Hensen's cells and at the lower (and upper) surface of the TM from the inner sulcus to the OHC region. These locations are in the neighborhood of where electromechanical force is coupled into (1) the mechanoelectrical transducers of the stereocilia and (2) fluids of the organ of Corti. Experiments are conducted in the first, second, and third cochlear turns of an in vitro preparation of the adult guinea pig cochlea. Vibration measurements are made at functionally relevant stimulus frequencies (0.48-68 kHz) and response amplitudes (<15 nm). The experiments provide phase relations between the different structures, which, dependent on frequency range and longitudinal cochlear position, include in-phase transverse motions of the TM, counterphasic transverse motions between the inner hair cell and OHCs, as well as traveling-wave motion of Hensen's cells in the radial direction. Mechanics of sound processing in the cochlea are discussed based on these phase relationships. PMID:22225042

Nowotny, Manuela; Gummer, Anthony W

2011-12-01

209

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

210

Dynamic response characteristics of two transport models tested in the National Transonic Facility  

NASA Technical Reports Server (NTRS)

This paper documents recent experiences with measuring the dynamic response characteristics of a commercial transport and a military transport model during full scale Reynolds number tests in the National Transonic Facility. Both models were limited in angle of attack while testing at full scale Reynolds number and cruise Mach number due to pitch or stall buffet response. Roll buffet (wing buzz) was observed for both models at certain Mach numbers while testing at high Reynolds number. Roll buffet was more severe and more repeatable for the military transport model at cruise Mach number. Miniature strain-gage type accelerometers were used for the first time for obtaining dynamic data as a part of the continuing development of miniature dynamic measurements instrumentation for cryogenic applications. This paper presents the results of vibration measurements obtained for both the commercial and military transport models and documents the experience gained in the use of miniature strain gage type accelerometers.

Young, Clarence P., Jr.

1993-01-01

211

Characteristics of a vibration membrane in water recovery from fine carbon-loaded wastewater  

Microsoft Academic Search

A conventional coagulation and settlement method was used for the treatment of fine carbon-loaded wastewater from TV picture tube plants. The method is generally costly and a large amount of solid waste was created. The application of a vibration membrane to deal with this kind of wastewater has proven to be cost effective. The recovered water can be reused and

S. C. Low; H. J. Han; W. X. Jin

2004-01-01

212

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.

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

2011-01-01

213

Temperature modulation of the vibrational responses of a flexible fluid-conveying pipe  

NASA Astrophysics Data System (ADS)

In this study, the nonlinear transverse vibration of a flexible pipe conveying hot, pressurized fluid is investigated. The pipe which is subjected to a pinned-pinned end condition extends as a result of several operating variables such as internal fluid temperature variation, pre-stress and internal pressurization. The equation of motion is solved analytically by hybrid Fourier-Laplace transforms, and the effects of inlet temperature, temperature gradient, and coefficient of area deformation are investigated on the natural frequencies and transverse dynamic response of the pipeline. While the inlet temperature and temperature gradient are found to be inversely proportional to the natural frequencies and amplitude of the dynamic response, increase in the coefficient of area deformation has little effect on the natural frequencies for the particular case considered.

Adelaja, Adekunle O.

2013-12-01

214

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.

Cao, Hongrui; Niu, Linkai; He, Zhengjia

2012-01-01

215

Vibrational response prediction of a pneumatic tyre using an orthotropic two-plate wave model  

NASA Astrophysics Data System (ADS)

A wave model to predict the vibrational response of a pneumatic tyre subject to line force excitation is presented. The tread and sidewalls are each modelled as thin, flat orthotropic plates with in-plane tension, which are joined together by a translational stiffness, and to a rigid rim. The dynamic response of the tyre to harmonic excitation is decomposed into spatial harmonics around the circumference, and waves in the meridional direction. At low frequencies (<100 Hz), the response is stiffness-like, and is controlled by the sidewall properties and tension effects resulting from the tyre pressure. In the mid-frequency range (100-500 Hz), a resonant response is observed, associated with modes both across and around the tyre. At high frequencies (>500 Hz), the response tends towards that of an infinite orthotropic plate. Experiments have been conducted on an inflated tyre fitted to a wheel rim to confirm the theoretical findings. The results show reasonable agreement with the predictions, the model accurately reflecting the phenomenological behaviour.

Muggleton, J. M.; Mace, B. R.; Brennan, M. J.

2003-07-01

216

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

217

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

218

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.

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

2014-01-01

219

Display of response characteristics of seismic source arrays  

SciTech Connect

In seismic exploration wherein an array of seismic sources is moved along a line of exploration on the earth's surface and the reflections and/or refractions of seismic energy from the sources are recorded as seismograms, a method of displaying the response characteristics of the array is described which consists of: determining the amplitude response of the array at a plurality of locations at different azimuth angles and at different dip angles from the array; selecting equal values of determined amplitude response; and displaying contours of the equal values of amplitude response as a function of azimuth and dip angle in a stereoscopic polar projection.

Bowman, B.F.; Pann, K.; Pedeker, M.S.

1986-05-20

220

[Hand-arm vibration syndrome: diagnostic aspects, dose-response relationship and exposure limits].  

PubMed

This paper reviews the clinical aspects and laboratory methods to diagnose the vascular, sensorial and neural components of the hand-arm vibration syndrome. The resolutions adopted by the experts of the Stockholm Workshop 94 are reported. The methods of measurement and assessment of both daily and cumulative vibration exposure are discussed with respect to the risk for vibration-induced disorders of the upper extremities. An update of the relationship between vibration exposure and the occurrence of vibration-induced white finger (VWF) is given, as well as the results of epidemiologic studies of the reversibility of VWF after cessation of vibration exposure or introduction of vibration isolation systems in forest work. Regarding occupational exposure to hand-transmitted vibrations, this review considers the guidelines and provisions contained in the European Communities (EC) Directive for machinery (89/393/EC) and the proposal for an EC Directive for physical agents (94/C 230/03). PMID:7731405

Bovenzi, M

1994-01-01

221

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

222

The RAYLEIGH-RITZ Solution to Estimate Vibration Characteristics of Building Floors  

NASA Astrophysics Data System (ADS)

An approximate solution for floor vibration is proposed as an aid to structural design. The building floor is approximated as a thin rectangular plate in order to use the Rayleigh-Ritz method in the analysis. To represent various structural types of building floors, the plate may be simultaneously subjected to many different factors, including orthotropy of the plate material, the presence of in-plane forces, uniform elastic edge supports, elastic point supports, reinforcement by flexural and torsional beams and vibration control by tuned mass dampers (TMDs). Beam functions, for which free edge conditions of the plate are generally difficult to represent, are used in practice as admissible functions in the Rayleigh-Ritz method under various boundary conditions, in consideration of the approximate approach for only free edge conditions of the plate. The accuracy and applicability of the approximate solution are confirmed in comparison with the results obtained by earlier studies and the finite element method (FEM).

Kato, Y.; Honma, T.

1998-03-01

223

Normal-mode characteristics of chlorophyll models. Vibrational analysis of metallooctaethylchlorins and their selectively deuterated analogues  

Microsoft Academic Search

The resonance Raman (RR) and infrared (IR) spectra of the Zn, Cu, and Ni complexes of trans-octaethylchlorin (OEC) reveal significant differences in the vibrational-mode properties of metallochlorins and metalloporphyrins. Modes with a contribution from the C{sub a}C{sub m} stretching coordinate are distinguished by their sensitivity to metal substitution and to selective dâ and dâ methine deuteration. Comparison of the resonance

Harold N. Fonda; W. Anthony Oertling; Asaad Salehi; Chi K. Chang; Gerald T. Babcock

1990-01-01

224

Verification test and evaluation of vibration characteristics for the ASTER cryocoolers  

NASA Astrophysics Data System (ADS)

The advanced spaceborne thermal emission and reflection radiometer (ASTER) is an instrument which was selected by NASA to fly on the EOS-AM1 platform in 1998. Two cryocoolers are required to cool infrared detectors for the short-wave infrared radiometer (SWIR) and thermal infrared radiometer (TIR). The mission lifetime of the EOS-AM1 platform is expected to be 5 years, and accordingly, an operation lifetime more than 5 years is required for ASTER cryocoolers. The goals in the development of the ASTER cryocoolers are realization of a operation lifetime of over 50,000 hours and mechanical vibration forces below 0.1 N in the frequency range from 40 Hz to 135 Hz in the driection of all three axes. A split- Stirling cycle cryocoolers with clearance seals and linear motors is employed for this purpose. The compressor design adopts a piston driving mechanism which has a twin-opposed piston configuration in one compression space. The mechanical vibration caused by a displacer in the expander unit is reduced by an active balancer. Cryocoolers for SWIR and TIR have cooling capacity of 1.2 W at 70 K with power consumption lower than 55 W without control electronics. Several engineering models (EM) have been fabricated and are presently undergoing performance and life tests. Results of cryocooler verification tests and effects of jitter of mechanical vibration on the ASTER instrument are described.

Kawada, Masakuni; Fujisada, Hiroyuki; Kobayashi, Minoru; Akao, Hiroshi; Nishihara, Osamu; Nishimoto, Atsushi

1995-09-01

225

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

Hye Jin Kim; Woo Seok Yang; Kwangsoo No

2013-08-01

226

Experimental-numerical investigation of the dynamic stability of flexural-torsional vibrations of compressor blades under conditions of attached and separated flow. Part 2. Cross aerodynamic characteristics  

Microsoft Academic Search

We consider the results of investigation of cross aerodynamic characteristics of compressor blades and their dynamic stability\\u000a under flexural-torsional vibrations for the cases of attached and separated flows in broad ranges of variations of the phase\\u000a shift, the ratio of amplitudes of the translational and angular components of displacements, the angle of attack, the reduced\\u000a frequency of vibrations, and the

A. L. Stel’makh; A. P. Zinkovskii; Ya. A. Stel’makh

2009-01-01

227

Vibrational response of free standing single copper nanowire through transient reflectivity microscopy  

NASA Astrophysics Data System (ADS)

We report on the ultrafast vibrational response of single copper nanowires investigated by femtosecond transient reflectivity measurements. The oscillations of the sample reflectivity are correlated with individual modes of resonance for wires with a diameter ranging from 100 to 500 nm and are compared with 2D finite element simulation. Fluctuation of the sample-substrate coupling is illustrated through its effect on the damping rate. We demonstrate elastic confinement in free standing wires which allowed the detection of up to the third harmonic of the breathing mode. By removing the energy relaxation channel towards the substrate, we obtained nano-oscillators with quality factors up to 130. Finally, taking advantage of the very high spectral resolution achieved on free standing wires, we could observe the elastic coupling between two close wires via their polymer cladding.

Belliard, Laurent; Cornelius, Thomas W.; Perrin, Bernard; Kacemi, Nazim; Becerra, Loïc; Thomas, Olivier; Eugenia Toimil-Molares, Maria; Cassinelli, Marco

2013-11-01

228

Chirping characteristic and frequency response of MQW optical intensity modulator  

Microsoft Academic Search

The spectral linewidth enhancement factor and frequency responses of electro-absorption-type optical-intensity modulators, especially InGaAs\\/InAlAs MQW modulators, are described. A method of exactly estimating the value of the ? factor is presented under the nonlinearity of extinction-ratio characteristics. For measuring the frequency response of modulators, the sideband strength of the modulated output light with an optical spectrum analyzer, is analytically compared

Osamu Mitomi; Shunji Nojima; Isamu Kotaka; Koichi Wakita; Kenji Kawano; Mitsuru Naganuma

1992-01-01

229

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.

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

2012-01-01

230

Gender differences in knee stability in response to whole-body vibration.  

PubMed

The purpose of this study was to determine whether there are kinematic and electromyographic (EMG) differences between men and women in how the knee is controlled during a single-legged drop landing in response to whole-body vibration (WBV). Forty-five healthy volunteers, 30 men (age 22 ± 3 years; weight 76.8 ± 8.8 kg; height 179.0 ± 6.8 cm) and 15 women (age 22 ± 3 years; weight 61.0 ± 7.7 kg; height 161.9 ± 7.2 cm) were recruited for this study. Knee angles, vertical ground reaction forces, and the time to stabilize the knee were assessed after single-legged drop landings from a 30-cm platform. Surface EMG data in rectus femoris (RF) and hamstrings (H) and knee and ankle accelerometry signals were also acquired. The participants performed 3 pretest landings, followed by a 3-minute recovery and then completed 1 minute of WBV (30 Hz to 4 mm). Before vibration, the female subjects had a significantly higher peak vertical force value, knee flexion angles, and greater H preactivity (EMG(RMS) 50 milliseconds before activation) than did the male subjects. In addition, although not significant, the medial-lateral (ML) acceleration in both knee and ankle was also higher in women. After WBV, no significant differences were found for any of the other variables. However, there was a decrease in the RF to H activation ratio during the precontact phase and an increase in the ratio during the postcontact phase just in women, which leads to a decrement in ML acceleration. The gender differences reported in knee stability in response to WBV underline the necessity to perform specific neuromuscular training programs based on WBV together with instruction of the proper technique, which can assist the clinician in the knee injury prevention. PMID:21997457

Sañudo, Borja; Feria, Adrian; Carrasco, Luis; de Hoyo, Moisés; Santos, Rui; Gamboa, Hugo

2012-08-01

231

Poststimulus response characteristics of the human cone flicker electroretinogram.  

PubMed

At certain temporal frequencies, the human cone flicker electroretinogram (ERG) contains multiple additional responses following the termination of a flicker train. The purpose of this study was to determine whether these poststimulus responses are a continuing response to the terminated flicker train or represent the oscillation of a resonant system. ERGs were recorded from 10 visually normal adults in response to full-field sinusoidally modulated flicker trains presented against a short-wavelength rod-saturating adapting field. The amplitude and timing properties of the poststimulus responses were evaluated within the context of a model of a second-order resonant system. At stimulus frequencies between 41.7 and 71.4 Hz, the majority of subjects showed at least three additional ERG responses following the termination of the flicker train. The interval between the poststimulus responses was approximately constant across stimulus frequency, with a mean of 14.4 ms, corresponding to a frequency of 69.4 Hz. The amplitude and timing characteristics of the poststimulus ERG responses were well described by an underdamped second-order system with a resonance frequency of 70.3 Hz. The observed poststimulus ERG responses may represent resonant oscillations of retinal ON bipolar cells, as has been proposed for electrophysiological recordings of poststimulus responses from retinal ganglion cells. However, further investigation is required to determine the types of retinal neurons involved in the generation of the poststimulus responses of the human flicker ERG. PMID:24016531

Gowrisankaran, Sowjanya; McAnany, J Jason; Alexander, Kenneth R

2013-07-01

232

RESPONSE CHARACTERISTICS OF A DEAD-CELL BOD SENSOR  

Microsoft Academic Search

Bacillus subtilis cells, thermally killed by exposing dried cells to 280°C for 2.5mins, were used for fabricating the biofilm attached to a dissolved oxygen probe. The dead cell biosensor showed good sensing characteristics for the BOD of aqueous organic solutions and wastewaters in regard to its response and recovery times, reproducibility and stability. It has a significantly long life span

Zhenrong Qian; T. C Tan

1998-01-01

233

Sensitivity of atmospheric response to modeled snow anomaly characteristics  

Microsoft Academic Search

The presence of snow over broad land surface regions has been shown to not only suppress local surface temperatures, but also influence various remote climate phenomena. However, the specific mechanisms and snow anomaly characteristics which produce this response are still not well understood. In this study, large-ensemble general circulation model (GCM) experiments are performed to investigate the sensitivity of the

Gavin Gong; Dara Entekhabi; Judah Cohen; David Robinson

2004-01-01

234

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

235

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

236

Static strain and vibration characteristics of a metal semimonocoque helicopter tail cone of moderate size  

NASA Technical Reports Server (NTRS)

The results are presented of an analytic and experimental research program involving a Sikorsky S-55 helicopter tail cone directed ultimately to the improved structural analysis of airframe substructures typical of moderate sized helicopters of metal semimonocoque construction. Experimental static strain and dynamic shake-testing measurements are presented. Correlation studies of each of these tests with a PC-based finite element analysis (COSMOS/M) are described. The tests included static loadings at the end of the tail cone supported in the cantilever configuration as well as vibrational shake-testing in both the cantilever and free-free configurations.

Bielawa, Richard L.; Hefner, Rachel E.; Castagna, Andre

1991-01-01

237

Smart vibration control analysis of seismic response using MR dampers in the elevated highway bridge structures  

NASA Astrophysics Data System (ADS)

The magnetorheological (MR) damper is on of the smart controllers used widely in civil engineering structures. These kinds of dampers are applied in the paper in the elevated highway bridge (EHB) with rubber bearing support piers to mitigate damages of the bridge during the severe earthquake ground motion. The dynamic calculating model and equation of motion for the EHB system are set up theoretically and the LQR semi-active control algorithm of seismic response for the EHB system is developed to reduce effectively the responses of the structure. The non-linear calculation model of the piers that rigid degradation is considered and numerical simulative calculation are carried out by Matlab program. The number and location as well as the maximum control forces of the MR dampers, which are the most important parameters for the controlled system, are determined and the rubber bearing and connection forms of the damper play also important rule in the control efficiency. A real EHB structure that is located in Anshan city, Liaoning province in China is used as an example to be calculated under different earthquake records. The results of the calculation show that it is effective to reduce seismic responses of the EHB system by combining the rubber bearing isolation with semi-active MR control technique under the earthquake ground motion. The locations of MR dampers and structural parameters will influence seriously to the effects of structural vibration control.

Yan, Shi; Zhang, Hai

2005-05-01

238

Influence of hand–arm posture on biodynamic response of the human hand–arm exposed to z h-axis vibration  

Microsoft Academic Search

The influence of hand–arm posture on the biodynamic responses under zh-axis vibration is investigated in terms of driving point mechanical impedance and absorbed power under various combinations of hand grip and push forces, handle sizes and excitation levels. Laboratory measurements of the biodynamic responses were performed on seven healthy male subjects exposed to two levels of broadband random vibration in

Y. Aldien; P. Marcotte; S. Rakheja; P.-E. Boileau

2006-01-01

239

Micro-vibration response of a stochastically excited sandwich beam with a magnetorheological elastomer core and mass  

NASA Astrophysics Data System (ADS)

Magnetorheological (MR) elastomers are used to construct a smart sandwich beam for micro-vibration control. The micro-vibration response of a clamped-free sandwich beam with an MR elastomer core and a supplemental mass under stochastic support micro-motion excitation is studied. The dynamic behavior of MR elastomer as a smart viscoelastic material is described by a complex modulus which is controllable by external magnetic field. The sixth-order partial differential equation of motion of the sandwich beam is derived from the dynamic equilibrium, constitutive and geometric relations. A frequency-domain solution method for the stochastic micro-vibration response of the sandwich beam is developed by using the frequency-response function, power spectral density function and spatial eigensolution. The root-mean-square velocity response in terms of the one-third octave frequency band is calculated, and then the response reduction capacity through optimizing the complex modulus of the core is analyzed. Numerical results illustrate the influences of the MR elastomer core parameters on the root-mean-square velocity response and the high response reduction capacity of the sandwich beam. The developed analysis method is applicable to sandwich beams with arbitrary cores described by complex shear moduli under arbitrary stochastic excitations described by power spectral density functions.

Ying, Z. G.; Ni, Y. Q.

2009-09-01

240

Vibrational diagnostics of rotating machinery malfunctions  

NASA Astrophysics Data System (ADS)

The diagnostics of rotating machinery malfunction, using vibration data in correlation with operational process data is outlined. The advantages of vibration monitoring systems as a part of preventive/predictive maintenance programs are emphasized. The basic principles of machinery diagnostics, and several specific malfunction symptoms supported by simple mathematical models are given. These malfunctions include unbalance, excessive radial preload, rotor to stator rubbing, fluid induced vibrations, loose stationary and rotating parts, coupled torsional/lateral vibration excitation, and rotor cracking. The experimental results and actual field data illustrate the rotor vibration responses for individual malfunctions. Application of synchronous and nonsynchronous perturbation testing used for identification of basic dynamic characteristics of machinery is presented. Future advancements in vibration monitoring and diagnostics of rotating machinery health are discussed. The basic instrumentation for machine monitoring is outlined.

Muszynska, A.

241

Vibration signature analysis of multistage gear transmission  

NASA Technical Reports Server (NTRS)

An analysis is presented for multistage multimesh gear transmission systems. The analysis predicts the overall system dynamics and the transmissibility to the gear box or the enclosed structure. The modal synthesis approach of the analysis treats the uncoupled lateral/torsional model characteristics of each stage or component independently. The vibration signature analysis evaluates the global dynamics coupling in the system. The method synthesizes the interaction of each modal component or stage with the nonlinear gear mesh dynamics and the modal support geometry characteristics. The analysis simulates transient and steady state vibration events to determine the resulting torque variations, speeds, changes, rotor imbalances, and support gear box motion excitations. A vibration signature analysis examines the overall dynamic characteristics of the system, and the individual model component responses. The gear box vibration analysis also examines the spectral characteristics of the support system.

Choy, F. K.; Tu, Y. K.; Savage, M.; Townsend, D. P.

1989-01-01

242

Effects of surface finish and treatment on the fatigue behaviour of vibrating cylinder block using frequency response approach  

Microsoft Academic Search

This paper presents the effects of surface finish and treatment on the high cycle fatigue behaviour of vibrating cylinder block of a new two-stroke free piston engine at complex variable amplitude loading conditions using frequency response approach. Finite element modelling and frequency response analysis was conducted using finite element analysis software Package MSC.PATRAN\\/MSC.NASTRAN and fatigue life prediction was carried out

243

Effects of surface finish and treatment on the fatigue behaviour of vibrating cylinder block using frequency response approach  

Microsoft Academic Search

This paper presents the effects of surface finish and treatment on the high cycle fatigue behaviour of vibrating cylinder\\u000a block of a new two-stroke free piston engine at complex variable amplitude loading conditions using frequency response approach.\\u000a Finite element modelling and frequency response analysis was conducted using finite element analysis software Package MSC.PATRAN\\/MSC.NASTRAN\\u000a and fatigue life prediction was carried out

M. M. Rahman; A. K. Ariffin

2006-01-01

244

COMPARISON OF SUBJECTIVE RESPONSES TO VIBRATION AND SHOCK WITH STANDARD ANALYSIS METHODS AND ABSORBED POWER  

Microsoft Academic Search

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

N. J. MANSFIELD; P. Holmlund; R. Lundström

2000-01-01

245

The nonlinear forced response characteristics of contained fluids in microgravity  

NASA Astrophysics Data System (ADS)

An experimental study of the change in the lateral slosh behavior of contained fluids between earth and space is presented. The experimental apparatus used to determine the slosh characteristics is described and a nonlinear analytic model of a coupled fluid/spacecraft system is outlined. The forced response characteristics of silicon oil and distilled water in cylinder tanks with either a flat or spherical bottom are reported and discussed. A comparison of the measured earth and space results identifies and highlights the effects of gravity on the linear and nonlinear slosh behavior of these fluids.

Vanschoor, M. C.; Crawley, E. F.

246

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

247

Minimizing vibration response of cylindrical shells through layout optimization of passive constrained layer damping treatments  

NASA Astrophysics Data System (ADS)

A layout optimization of passive constrained layer damping (PCLD) treatment for minimizing the vibration response of cylindrical shells is presented with consideration of broadband transverse force excitation. The equations governing the displacement responses, relating the integrated out-of-plane displacement over the whole structural volume, i.e., the structural volume displacement (SVD), of a cylindrical shell to structural parameters of base structure and multiple PCLD patches, are derived using the energy approach and assumed-mode method. Genetic algorithm (GA) based penalty function method is employed to find the optimal layout of rectangular PCLD patches with aim to minimize the SVD of the PCLD-treated cylindrical shell. Optimization solutions of the locations of patches for PCLD treatment are obtained under the constraint of total amount of PCLD materials in terms of percentage added weight to the base structure. Effects due to number of patches, their aspect ratios, and total amount of added PCLD weight are also studied. Examination of the optimal layouts reveals that the patches tend to increase their coverage in the axial direction and distribute over the whole surface of the cylindrical shell for optimal SVD reduction.

Zheng, H.; Cai, C.; Pau, G. S. H.; Liu, G. R.

2005-01-01

248

Normal-mode characteristics of chlorophyll models. Vibrational analysis of metallooctaethylchlorins and their selectively deuterated analogues  

SciTech Connect

The resonance Raman (RR) and infrared (IR) spectra of the Zn, Cu, and Ni complexes of trans-octaethylchlorin (OEC) reveal significant differences in the vibrational-mode properties of metallochlorins and metalloporphyrins. Modes with a contribution from the C{sub a}C{sub m} stretching coordinate are distinguished by their sensitivity to metal substitution and to selective d{sub 2} and d{sub 4} methine deuteration. Comparison of the resonance Raman spectrum of CuOEC with that of CuECI (ECI = etiochlorin I) identifies those modes with a contribution from C{sub b}C{sub b} and C{sub b}C{sub s} stretching and C{sub b}C{sub s} bending coordinates. The results obtained show that there is substantial mixing of C{sub a}C{sub m} and C{sub b}C{sub b} stretching character in the high-frequency modes of MOEC. The suggestion that the symmetry reduction that occurs in metallochlorins relative to metalloporphyrins produces vibrational-mode localization to specific hemispheres or quadrants of the macrocycle has been tested and confirmed by specific d{sub 2} deuteration at the methine carbons. Resonance Raman spectra of CuOEP-d{sub 2} (OEP = octaethylporphyrin) and CuOEP-d{sub 4} establish that, for a delocalized mode, methine d{sub 2} deuteration can be expected to produce half the d{sub 4} shift. For CuOEC, selective deuteration at the {alpha}{beta} and {gamma},{delta} methine positions causes different patterns of frequency shifts that indicate the extent of mode localization.

Fonda, H.N.; Oertling, W.A.; Salehi, A.; Chang, C.K.; Babcock, G.T. (Michigan State Univ., East Lansing (United States))

1990-12-19

249

Multi-frequency periodic vibration suppressing in active magnetic bearing-rotor systems via response matching in frequency domain  

NASA Astrophysics Data System (ADS)

A method for multi-frequency periodic vibration suppressing in active magnetic bearing (AMB)-rotor systems is proposed, which is based on an adaptive finite-duration impulse response (FIR) filter in time domain. Firstly, the theoretic feasibility of the method is proved. However, two problems would be unavoidable, if the conventional adaptive FIR filter is adopted in practical application. One is that the convergence rate of the different frequency components may be highly disparate in multi-frequency vibration control. The other is that the computational complexity is significantly increased because the long memory FIR filter is required to match the transient response time of the AMB-rotor system. To overcome the problems above, the Fast Block Least Mean Square (FBLMS) algorithm is adopted to efficiently implement the computation in frequency domain at a computational cost far less than that of the conventional FIR filter. By the FBLMS algorithm, regardless of the number of the considered frequency components in vibration disturbance, the computational complexity would be invariable. Moreover, filter's weights in the FBLMS algorithm have the intuitional relation with signal's frequency. As a result, the convergence rate of each frequency component can be adjusted by assigning the individual step size parameter for each weight. Experiments with the reciprocating simulating disturbance test and the rotating harmonic vibration test were carried out on an AMB-rigid rotor test rig with a vertical shaft. The experiment results indicate that the proposed method with the FBLMS algorithm can achieve the good effectiveness for suppressing the multi-frequency vibration. The convergence property of each frequency component can be adjusted conveniently. Each harmonic component of the vibration can be addressed, respectively, by reconfiguring the frequency components of the reference input signal.

Jiang, Kejian; Zhu, Changsheng

2011-05-01

250

Free-vibration characteristics of a large split-blanket solar array in a 1-g field  

NASA Technical Reports Server (NTRS)

Two methods for studying the free vibration characteristics of a large split blanket solar array in both a 0-g and a 1-g cantilevered configuration are presented. The 0-g configuration corresponds to an in-orbit configuration of the array; the 1-g configuration is a typical ground test configuration. The first method applies the equations of continuum mechanics to determine the mode shapes and frequencies of the array; the second method uses the Rayleigh-Ritz approach. In the Rayleigh-Ritz method the array displacements are represented by string modes and cantilevered beam modes. The results of this investigation are summarized by a series of graphs illustrating the effects of various array parameters on the mode shapes and frequencies of the system. The results of the two methods are also compared in tabular form.

Shaker, F. J.

1976-01-01

251

Characteristic Timescales of Shoreface Response to Sea-Level Rise  

NASA Astrophysics Data System (ADS)

On open ocean, wave-dominated, sandy coasts, the response of the shore to sea-level rise is dominated not by inundation, but rather by the dynamic response of sediment transport processes to perturbations of the sea level. In a regime of sea level change, the predominant response of the wave-dominated shoreface depends upon the time-dependent response of the shoreface itself to changes in sea level as well as the potential changes to the shoreline. On a barrier coast, persistent, long-term changes to the shoreline are caused by storm overwash, which transports marine sediment landward, moving the shoreline boundary. Raised sea levels increase the impact and frequency of this overwash as relative barrier elevation is reduced. Overall, sediment transport processes on the shoreface remain poorly understood, complicating predictions of equilibrium shoreface shapes and even net sediment transport directions. However, presuming an equilibrium geometry, energetics-based, time-averaged relationships for cross-shore sediment transport provide a framework to understand the characteristic rates and types of shoreface response to perturbations to either the sea level or the shoreline boundary. In the case of a sea-level rise, we find that the dominant perturbation for a barrier system is not the sea-level rise itself, but rather the movement of the shoreline by overwash. The characteristic response time of the shoreface itself increases significantly at depth, suggesting that the lower shoreface response to a sea level change can be significantly delayed. We estimate the importance of extreme events on shoreface evolution by analyzing decade-long data series of wave characteristics along different open ocean coasts with barriers (Florida Gulf Coast, North Carolina, Marthas Vineyard). Analogous to the effect of floods in fluvial systems, although storm events can move significant sediment, the infrequency of the larger events limits their effect on the shoreface-the morphologically significant event for shoreface evolution has a return interval of less than two years. However, numerical simulations of tens of thousands of synthetic storm strikes at the same locations suggest that the return interval of storm events expected to cause significant overwash is longer, on the order of at least 50 years. To study the interactions between the characteristic timescales of shoreface evolution and barrier overwash, we apply a numerical model of barrier profile evolution that couples shoreface evolution with barrier overwash. This integrated model provides a tool to understand the response of barrier systems to changes in sea level over the late Holocene to the modern. The model also investigates the potential behavior of barrier systems as they (and their human occupants) respond to predicted increased rates of sea-level rise over the coming centuries.

Ashton, A. D.; Ortiz, A.; Lane, P.; Donnelly, J. P.

2011-12-01

252

Probabilistic analysis of mean-response along-wind induced vibrations on wind turbine towers using wireless network data sensors  

NASA Astrophysics Data System (ADS)

Wind turbine systems are attracting considerable attention due to concerns regarding global energy consumption as well as sustainability. Advances in wind turbine technology promote the tendency to improve efficiency in the structure that support and produce this renewable power source, tending toward more slender and larger towers, larger gear boxes, and larger, lighter blades. The structural design optimization process must account for uncertainties and nonlinear effects (such as wind-induced vibrations, unmeasured disturbances, and material and geometric variabilities). In this study, a probabilistic monitoring approach is developed that measures the response of the turbine tower to stochastic loading, estimates peak demand, and structural resistance (in terms of serviceability). The proposed monitoring system can provide a real-time estimate of the probability of exceedance of design serviceability conditions based on data collected in-situ. Special attention is paid to wind and aerodynamic characteristics that are intrinsically present (although sometimes neglected in health monitoring analysis) and derived from observations or experiments. In particular, little attention has been devoted to buffeting, usually non-catastrophic but directly impacting the serviceability of the operating wind turbine. As a result, modal-based analysis methods for the study and derivation of flutter instability, and buffeting response, have been successfully applied to the assessment of the susceptibility of high-rise slender structures, including wind turbine towers. A detailed finite element model has been developed to generate data (calibrated to published experimental and analytical results). Risk assessment is performed for the effects of along wind forces in a framework of quantitative risk analysis. Both structural resistance and wind load demands were considered probabilistic with the latter assessed by dynamic analyses.

Velazquez, Antonio; Swartz, Raymond A.

2011-03-01

253

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

254

The response of an elastically supported infinite Timoshenko beam to a moving vibrating mass  

SciTech Connect

An analysis is made of the problem of vibrations of an infinite beam on elastic foundation excited by a moving and vibrating mass. The solution is presented within the framework of a beam theory which includes the effects of shear deformation and rotatory inertia. An example is provided where the displacement is calculated. {copyright} {ital 1997 Acoustical Society of America.}

Mackertich, S. [Pennsylvania State University---Harrisburg, Middletown, Pennsylvania 17057-4898 (United States)] [Pennsylvania State University---Harrisburg, Middletown, Pennsylvania 17057-4898 (United States)

1997-01-01

255

Combined Effects of Noise and Vibration on Human Tracking Performance and Response Time.  

National Technical Information Service (NTIS)

Vibration has been shown to be the primary cause of performance impairment in studies of the combined effects of noise and vibration on human tracking performance. Noise has had little consistent effect when presented alone, and has added little or not at...

C. S. Harris H. C. Sommer

1973-01-01

256

Method to characterize the vibrational response of a beetle type scanning tunneling microscope  

Microsoft Academic Search

We describe a method for analyzing the external vibrations and intrinsic mechanical resonances affecting scanning probe microscopes by using the microscope as an accelerometer. We show that clear correlations can be established between the frequencies of mechanical vibrational modes and the frequencies of peaks in the tunnel current noise power spectrum. When this method is applied to our “beetle” type

Stefan Behler; Mark K. Rose; D. Frank Ogletree; Miquel Salmeron

1997-01-01

257

Biodynamic response of the human body in the sitting position when subjected to vertical vibration  

Microsoft Academic Search

Previous studies of the location of those areas in which the sensation of vibration is perceived under whole body vertical vibration have underlined the predominance of the relative movement between thorax and pelvis. Experiments were designed to explore systematically the transmissibility between the pelvis and thorax. These were supplemented by measurements of mechanical impedance of the body and absorbed power.

P. M. Donati; C. Bonthoux

1983-01-01

258

The effect of ultrasonic vibration on the compaction characteristics of paracetamol.  

PubMed

An ultrasonic (US) compaction rig has been developed that is capable of providing compaction pressure together with high-power ultrasonic vibrations of 20 kHz to a powder or granular material in a die. The rig has been used to investigate the effect of US on the compaction properties of paracetamol, a drug that produces tablets that are weak and frequently exhibit capping. It was found that coherent paracetamol tablets could be prepared by US-assisted compaction at pressures as low as 20 to 30 MPa. Application of US before and after compaction was not found to be as effective as US applied during compaction. The breaking forces of the tablets produced with US applied during compaction were found to be consistently significantly higher than when compaction was performed conventionally or with US applied before or after compaction. The application of US during compaction made it possible to increase tablet breaking force, typically by a factor of 2 to 5. It was concluded that pressure should be applied together with US to achieve a better acoustical contact, which is required to transmit vibrations from the horn to the material and also to bond the surfaces of the particles. US application during compaction also resulted in an increase in apparent density, in relation to the apparent density of conventionally prepared paracetamol tablets, of up to 12.8%. US appears to improve particle rearrangement and provide energy for partial melting of particle asperities and subsequent fusion of particle surfaces, thus increasing interparticulate bonding. Development of solid bridges between the particles during US-assisted compaction was observed on scanning electron photomicrographs. Solid bridge formation was thought to result in a reduction of void space, which in turn reduced the rate of water penetration into the compacts and consequently increased tablet disintegration and drug dissolution times. It was found that the results of US-assisted compaction are influenced by formulation and US time. An increase in binder (polyvinylpyrrolidone) concentration and/or US time resulted in a significant increase in the breaking forces of paracetamol tablets produced with US. When paracetamol was mixed with a second material, such as dicalcium phosphate dihydrate and microcrystalline cellulose, stronger compacts were prepared by US-assisted compaction compared with the tablets containing no filler. Positive interactions were considered to have occurred as a result of US-induced bonding between the two materials. Overall, the application of US was found to significantly improve the compaction properties of paracetamol. PMID:10824129

Levina, M; Rubinstein, M H

2000-06-01

259

Frequency response functions of shape features from full-field vibration measurements using digital image correlation  

NASA Astrophysics Data System (ADS)

The availability of high speed digital cameras has enabled three-dimensional (3D) vibration measurement by stereography and digital image correlation (DIC). The 3D DIC technique provides non-contact full-field measurements on complex surfaces whereas conventional modal testing methods employ point-wise frequency response functions. It is proposed to identify the modal properties by utilising the domain-wise responses captured by a DIC system. This idea will be illustrated by a case study in the form a car bonnet of 3D irregular shape typical of many engineering structures. The full-field measured data are highly redundant, but the application of image processing using functional transformation enables the extraction of a small number of shape features without any significant loss of information from the raw DIC data. The complex bonnet surface on which the displacement responses are measured is essentially a 2-manifold. It is possible to apply surface parameterisation to 'flatten' the 3D surface to form a 2D planar domain. Well-developed image processing techniques are defined on planar domains and used to extract features from the displacement patterns on the surface of a specimen. An adaptive geometric moment descriptor (AGMD), defined on surface parametric space, is able to extract shape features from a series of full-field transient responses under random excitation. Results show the effectiveness of the AGMD and the obtained shape features are demonstrated to be succinct and efficient. Approximately 14 thousand data points of raw DIC measurement are represented by 20 shape feature terms at each time step. Shape-descriptor frequency response functions (SD-FRFs) of the response field and the loading field are derived in the shape feature space. It is seen that the SD-FRF has a similar format to the conventional receptance FRF. The usual modal identification procedure is applied to determine the natural frequencies, damping factors and eigen-shape-feature vectors from the SD-FRF. Natural frequencies and mode shapes from a finite element (FE) model are correlated with the experimental data using the cosine distance between the shape feature vectors with 20 terms. There are numerous benefits of using image decomposition to analyse 3D DIC measured data, including (1) representation of the raw measurement data with efficiency and succinctness; (2) determination of the FRF of any point on the specimen by the use of the full-field shape features; and (3) elimination of DIC measurement noise. Also, the SD-FRF is potentially ideal for cases of field excitation of structures.

Wang, Weizhuo; Mottershead, John E.; Siebert, Thorsten; Pipino, Andrea

2012-04-01

260

Musculoskeletal Response to Whole-Body Vibration During Fracture Healing in Intact and Ovariectomized Rats  

PubMed Central

This study investigated the effect of vibration on bone healing and muscle in intact and ovariectomized rats. Thirty ovariectomized (at 3 months of age) and 30 intact 5-month old female Sprague-Dawley rats underwent bilateral metaphyseal osteotomy of tibia. Five days later, half of the ovariectomized and of the intact rats were exposed to whole-body vertical vibration (90 Hz, 0.5 mm, 4 × g acceleration) for 15 min twice a day during 30 days. The other animals did not undergo vibration. After decapitation of rats, one tibia was used for computed tomographic, biomechanical, and histological analyses; the other was used for gene expression analyses of alkaline phosphatase (Alp), osteocalcin (Oc), tartrate-resistant acid phosphatase 1, and insulinlike growth factor 1. Serum Alp and Oc were measured. Mitochondrial activity, fiber area and distribution, and capillary densities were analyzed in M. gastrocnemius and M. longissimus. We found that vibration had no effect on body weight and food intake, but it improved cortical and callus densities (97 vs. 99%, 72 vs. 81%), trabecular structure (9 vs. 14 trabecular nodes), blood supply (1.7 vs. 2.1 capillaries/fiber), and oxidative metabolism (17 vs. 23 pmol O2/s/mg) in ovariectomized rats. Vibration generally increased muscle fiber size. Tibia biomechanical properties were diminished after vibration. Oc gene expression was higher in vibrated rats. Serum Alp was increased in ovariectomized rats. In ovariectomized rats, vibration resulted in an earlier bridging; in intact rats, callus bridging occurred later after vibration. The chosen vibration regimen (90 Hz, 0.5 mm, 4 × g acceleration, 15 min twice a day) was effective in improving musculoskeletal tissues in ovariectomized rats but was not optimal for fracture healing.

Stuermer, Ewa K.; Werner, Carsten; Wicke, Michael; Kolios, Leila; Sehmisch, Stephan; Tezval, Mohammad; Utesch, Clara; Mangal, Orzala; Zimmer, Sebastian; Dullin, Christian; Stuermer, Klaus M.

2010-01-01

261

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

262

Density response of a trapped Fermi gas: A crossover from the pair vibration mode to the Goldstone mode  

NASA Astrophysics Data System (ADS)

We consider the density response of a trapped two-component Fermi gas. Combining the Bogoliubov-deGennes method with the random phase approximation allows the study of both collective and single-particle excitations. Calculating the density response across a wide range of interactions, we observe a crossover from a weakly interacting pair vibration mode to a strongly interacting Goldstone mode. The crossover is associated with a depressed collective mode frequency and an increased damping rate, in agreement with density response experiments performed in strongly interacting atomic gases.

Korolyuk, A.; Kinnunen, J. J.; Törmä, P.

2011-09-01

263

Design and Characteristics of Mode-Coupling LiNbO3 Ultrasonic Motor Depended on Width-to-Length Ratio of the Stator Vibrator  

NASA Astrophysics Data System (ADS)

A miniature ultrasonic motor fabricated from a LiNbO3 rectangular plate was studied to improve its rotation characteristics. In this motor, the coupling modes of in-plane longitudinal and flexural modes caused by crystal anisotropy are used to realize a single-phase drive motor. The mode coupling vibrator is designed to have crystal cut angles and the width-to-length ratio W/L of the vibrator shape. In this study, we noted the new coupling condition of W/L? 0.84 compared with the conventional ratio of W/L=0.255. We considered the mechanism of the mode coupling and the design of the stator vibrator by finite element method analysis and experiments. From the results, we fabricated and investigated prototype motors of the vibrator with dimensions of 10× 2.55× 0.5 and 4.10× 3.48× 0.5 mm3. The newly designed motor with the vibrator of W/L=0.849 improved the motor characteristics for the equalization of rotation in both directions.

Hideki Tamura,; Takanori Morooka,; Yasuhiro Yamayoshi,; Manabu Aoyagi,; Takehiro Takano,; Seiji Hirose,

2010-07-01

264

Study of passenger subjective response to ideal and real-vehicle vibration environments  

NASA Technical Reports Server (NTRS)

The stimulus received by subjects tested on the passenger ride quality apparatus (PRQA) is defined. Additional analyses on the data collected from field tests using buses, were conducted to assess the relation between subjective ratings of ride quality and vibrations measured on the buses, and to better define the vibration stimulus measured in the field. The relation of subjective evaluation of simulations of bus rides produced by the DRQA to subjective evaluations of the actual bus rides is discussed. The relative contribution of the seat and floor vibration to human comfort in a simulated aircraft ride environment is discussed along with the determination of equal comfort curves through magnitude estimation.

Kirby, R. H.; Mikulka, P. J.

1975-01-01

265

Enhancement of eye motor response and electrical brain activity during noise and vibration in rabbits.  

PubMed

The relationship between electroencephalogram (EEG) and eye movements was studied in rabbits during optokinetic, vestibular, and optovestibular tests. EEG was recorded through permanently implanted electrodes. Exposure to noise and vibration increased the frequency and the velocity of optokinetic nystagmus (OKN). The increase was greater during vibration but greatest during combined noise and vibration. EEG activity was closely linked to changes in OKN and was particularly evident with the appearance of theta waves in the dorsal hippocampus. Also, rotation of the rabbit produced considerable activation in the EEG. PMID:6806747

Pyykkö, I; Matsuoka, I; Ito, S; Hinoki, M

1982-01-01

266

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

267

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

268

Terahertz Dielectric Response of Photoactive Yellow Protein (PYP): Influence of Conformational-Vibrational State during Photocycle and Hydration Effects  

NASA Astrophysics Data System (ADS)

Protein conformational change alters flexibility and conformational-vibrational modes that occur on a picosecond or sub-picosecond time scale. Terahertz dielectric measurements are sensitive to protein flexibility as they directly probe the density of states of these vibrational modes. Using terahertz time-domain spectroscopy, we measured the dielectric response of PYP thin films as a function of resting and photointermediate state. The absorbance increases smoothly as a function of frequency while the index of refraction exhibits no frequency dependence. A sharp transition in the dielectric response of the ground state is observed at 86% relative humidity (r.h.), corresponding to the point where the protein film has lost ˜50 water molecules relative to a 100% r.h. environment. Similar transitions observed for hen egg white lysozyme and cytochrome c correspond to the filling point of the first hydration shell.

Knab, Joseph; Chen, Jing-Yin; Hoff, Wouter; Markelz, Andrea

2006-03-01

269

Dynamic responses of the in-plane and out-of-plane vibrations for an axially moving membrane  

Microsoft Academic Search

The dynamic responses of both the in-plane and out-of-plane vibrations are investigated for an axially moving membrane. Using the extended Hamilton principle, equations of motion are derived for the moving membrane with no-slip boundary conditions at rollers. The equations of motion are discretized by using the Galerkin method and then the generalized-? time integration method is applied to compute the

Changho Shin; Jintai Chung; Hong Hee Yoo

2006-01-01

270

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

271

Effects of Vibration and G-Loading on Heart Rate, Breathing Rate, and Response Time  

NASA Technical Reports Server (NTRS)

Aerospace and applied environments commonly expose pilots and astronauts to G-loading and vibration, alone and in combination, with well-known sensorimotor (Cohen, 1970) and performance consequences (Adelstein et al., 2008). Physiological variables such as heart rate (HR) and breathing rate (BR) have been shown to increase with G-loading (Yajima et al., 1994) and vibration (e.g. Guignard, 1965, 1985) alone. To examine the effects of G-loading and vibration, alone and in combination, we measured heart rate and breathing rate under aerospace-relevant conditions (G-loads of 1 Gx and 3.8 Gx; vibration of 0.5 gx at 8, 12, and 16 Hz).

Godinez, Angelica; Ayzenberg, Ruthie; Liston, Dorian B.; Stone, Leland S.

2013-01-01

272

Rigid mode and harmonic response analysis of three-body vibrating screen  

Microsoft Academic Search

By using the ADAMS, the dynamic parameters of three-body vibrating screen are extracted, and the simple finite element model is established on the basis of parameters in ANSYS. The amplitude-frequency curve and phase-frequency curve is obtained by using the harmonic analysis. According to the error between the simulated amplitude of the vibrating screen and the actual magnitude, the correctness of

Chuanguang Ding; Fangzhen Song; Bo Song

2011-01-01

273

Method to characterize the vibrational response of a beetle type scanning tunneling microscope  

Microsoft Academic Search

We describe a method for analyzing the external vibrations and intrinsic mechanical resonances affecting scanning probe microscopes by using the microscope as an accelerometer. We show that clear correlations can be established between the frequencies of mechanical vibrational modes and the frequencies of peaks in the tunnel current noise power spectrum. When this method is applied to our {open_quotes}beetle{close_quotes} type

Stefan Behler; Mark K. Rose; D. Frank Ogletree; Miquel Salmeron

1997-01-01

274

Fretting wear damage of heat exchanger tubes: A proposed damage criterion based on tube vibration response  

SciTech Connect

A simple criterion is proposed to estimate fretting wear damage in heat exchanger tubes with clearance supports. The criterion is based on parameters such as vibration frequency, midspan vibration amplitude, span length, tube mass, and an empirical wear coefficient. It is generally accepted that fretting wear damage is proportional to a parameter called work rate. Work rate is a measure of the dynamic interaction between a vibrating tube and its supports. Due to the complexity of the impact-sliding behavior at the clearance supports, work rate calculations for heat exchanger tubes require specialized nonlinear finite element codes. These codes include contact models for various clearance support geometries. Such nonlinear finite element analyses are complex, expensive and time consuming. The proposed criterion uses the results of linear vibration analysis (i.e., vibration frequency and mid-span vibration amplitude due to turbulence) and does not require a nonlinear analysis. It can be used by nonspecialists for a quick evaluation of the expected work rate, and hence, the fretting wear damage of heat exchanger tubes. The proposed criterion was obtained from an extensive parametric study that was conducted using a nonlinear finite element program. It is shown that, by using the proposed work rate criteria, work rate can be estimated within a factor of two. This result, however, requires further testing with more complicated flow patterns.

Yetisir, M.; McKerrow, E.; Pettigrew, M.J. [Atomic Energy of Canada Ltd., Chalk River, Ontario (Canada). Chalk River Labs.

1998-08-01

275

The use of a digital computer for investigation of the dynamic characteristics of a man while pressing vertically downward with the straight arm on the handle of a vibrator (instrument)  

NASA Technical Reports Server (NTRS)

The dynamic characteristics of a man were investigated by the resonance method, by means of recordings of the amplitude-frequency characteristics of a vibrator straight arm human body system on a standard automatic recorder. Experiments were carried out with a specially constructed vibrator, the moving system of which was fastened to a bronze suspension with small losses. Vibrations of the handle, fastened to the moving system, were recorded with an accelerometer. The mass of the moving system m, rigidity of the suspension k and friction coefficient r of the vibrator (calibration) were determined by exact formulas.

Zazhivikhina, A. I.; Rosin, G. S.; Ryzhov, Y. I.

1973-01-01

276

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

277

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

NASA Astrophysics Data System (ADS)

CdS nanocomposites have been grown in polyvinyl alcohol matrix by a chemical synthesis process. The transmission electron micrographs of nanocomposites synthesized at 70-90 °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.; Chakraborty, A. K.

2009-04-01

278

EXPERIMENTAL STUDY ON BEHAVIOR OF KENCHI BLOCK MASONRY WALL WITH THE SHAKING TABLE TEST DURING BY VIBRATION CHARACTERISTICS AND FAILURE MECHANISM  

NASA Astrophysics Data System (ADS)

There are many earthquake damages of kenchi block masonry wall. So, we carried out experimental studies on the collapse mechanism of kenchi block masonry wall during earthquake. From these experimental data, i.e. acceleration response magnification, displacement and soil pressure were found to destroy the central wall vibrations caused by the subsidence of the embankment.

Ikemoto, Toshikazu; Mori, Masashi; Miyajima, Masakatsu; Hashimoto, Takao; Murata, Akira

279

Energy conservation in the transient response of nonlinear beam vibration problems subjected to pulse loading - A numerical approach  

NASA Technical Reports Server (NTRS)

The nonlinear vibration response of a double cantilevered beam subjected to pulse loading over a central sector is studied. The initial response is generated in detail to ascertain the energetics of the response. The total energy is used as a gauge of the stability and accuracy of the solution. It is shown that to obtain accurate and stable initial solutions an extremely high spatial and time resolution is required. This requirement was only evident through an examination of the energy of the system. It is proposed, therefore, to use the total energy of the system as a necessary stability and accuracy criterion for the nonlinear response of conservative systems. The results also demonstrate that even for moderate nonlinearities, the effects of membrane forces have a significant influence on the system. It is also shown that while the fundamental response is contained in a first mode envelope, the fluctuations caused by the higher order modes must be resolved.

Moyer, E. T., Jr.

1984-01-01

280

Characteristics of Late Negative ERG Responses Elicited By Sawtooth Flicker  

PubMed Central

Background This study aimed to determine whether the properties of the late negative responses (LNRs) of the electroretinogram (ERG) elicited by sawtooth flicker are consistent with the characteristics of the photopic negative response generated by a light pulse (PhNRpulse). Methods ERG recordings were obtained from 10 visually normal individuals and from 6 patients with optic atrophy (OA) in response to 8-Hz rapid-on and rapid-off sawtooth flicker and to brief (4 ms) light pulses. All stimuli were either long-wavelength (R), middle-wavelength (G), or a combination of equal luminances of long and middle-wavelengths (Y) presented on a short-wavelength, rod-saturating adapting field. Amplitudes of LNRs were obtained in response to rapid-on (LNRon) and rapid-off (LNRoff) sawtooth flicker, and were also derived from the sum of the ERG waveforms to the two sawtooth phases (LNRadd). Results For the control subjects, PhNRpulse amplitude varied with stimulus wavelength, being largest in response to a long-wavelength pulse, as expected. However, the amplitudes of LNRon, LNRoff, and LNRadd were not significantly different for R, Y, and G sawtooth flicker. Despite the absence of a chromatic effect, LNRoff and LNRadd amplitudes were significantly smaller in the OA patients than in the controls, similar to the results for the PhNRpulse, implying an inner retinal origin for the LNRoff and LNRadd. However, LNRon amplitudes did not differ significantly between the OA patients and controls, although there was a significant correlation between the LNRon and PhNRpulse for R stimuli. Conclusion We conclude that LNRoff and LNRadd but not LNRon can be useful measures to assess the integrity of the inner retina that can complement the PhNRpulse.

Gowrisankaran, Sowjanya; Genead, Mohamed A.; Anastasakis, Anastasios; Alexander, Kenneth R.

2012-01-01

281

Sound Field Characteristics in Air Gaps of Noncontact Ultrasonic Motor Driven by Two Flexural Standing Wave Vibration Disks  

NASA Astrophysics Data System (ADS)

The sound field characteristics in the air gaps of the noncontact ultrasonic motor driven by two flexural standing wave vibration disks were analyzed by finite element method (FEM). Standing wave sound fields with an opposite phase were generated in the two air gaps by a single driving stator. Traveling wave sound fields in the two air gaps are formed as the superposition of the standing wave sound fields generated by two stators whose temporal phases and spatial positions are different from each other. The traveling direction of the calculated sound fields coincided with the rotating direction of the rotor observed in the experiments. The intensity of the sound field generated in the air gap by the single driving stator was measured by detecting the voltage induced in another stator. A gap distance wider than 0.5 mm is required for a high revolution speed because the sound field generated in the gap on the opposite side of the rotor is weak in an air gap narrower than 0.3 mm.

Yasuhiro Yamayoshi,; Jun Shiina,; Hideki Tamura,; Seiji Hirose,

2010-07-01

282

Effect of vibrator to head coupling force on the auditory brain stem response to bone conducted clicks in newborn infants.  

PubMed

The effect of vibrator to head coupling force on the auditory brain stem response (ABR) to bone conducted clicks in newborn infants was investigated. Twenty full term newborn infants were tested. ABRs to bone conducted clicks were obtained with four different coupling forces (225, 325, 425, and 525 g) at stimulus intensities of 15 and 30 dB nHL. ABRs to air conducted clicks were also obtained at 30 dB nHL. The results of this study indicated that ABR wave V latencies to bone conducted clicks in newborn infants were affected significantly when the vibrator to head coupling force shift exceeded 200 g. It is recommended that the coupling force be controlled and remain consistent when implementing ABR to bone conducted stimuli in newborn infants. PMID:2026289

Yang, E Y; Stuart, A; Stenstrom, R; Hollett, S

1991-02-01

283

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

284

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

285

An experimental study for determining human discomfort response to roll vibration  

NASA Technical Reports Server (NTRS)

An experimental study using a passenger ride quality apparatus (PRQA) was conducted to determine the subjective reactions of passengers to roll vibrations. The data obtained illustrate the effect upon human comfort of several roll-vibration parameters: namely, roll acceleration level, roll frequency, and seat location (i.e., distance from axis of rotation). Results of an analysis of variance indicated that seat location had no effect on discomfort ratings of roll vibrations. The effect of roll acceleration level was significant, and discomfort ratings increased markedly with increasing roll acceleration level at all roll frequencies investigated. Of particular interest, is the fact that the relationship between discomfort ratings and roll acceleration level was linear in nature. The effect of roll frequency also was significant as was the interaction between roll acceleration level and roll frequency.

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

1976-01-01

286

Dynamic Response of a Stack/cable System Subjected to Vortex Induced Vibration  

NASA Astrophysics Data System (ADS)

In this study, a coupled model wind-induced vibration of a stack, based on an unsteady-flow theory and non-linear dynamics of the stack's heavy elastic suspended cables. Numerical analysis was performed to identify excitation mechanisms. The stack was found to be excited by vortex shedding. Once lock-in resonance occurred, the cables were excited by the transverse motion of the stack. Large-amplitude oscillations of the cables were due to parametric resonance. Appropriate techniques have been proposed to alleviate the vibration problem.

Cai, Y.; Chen, S. S.

1996-09-01

287

Picosecond time response characteristics of microchannel plate PMT detectors  

NASA Astrophysics Data System (ADS)

The output pulse width in the time response of photo-multiplier tubes (PMT) is much faster in micro-channel plate (MCP) models compared to more standard dynode chain PMTs due to a vastly reduced variation in the path length of the electrons through the amplifying system. Typically the pulse widths can be in the region of 200ps compared to the nanosecond domain occupied by the best conventional PMTs. Photek manufacture PMTs with one, two or three MCPs depending on the gain required, and also use the same structure without any MCPs to work as simple photodiodes. We demonstrate the variation of output pulse characteristics due to the number and design of MCPs in a range of PMT models and illustrate the importance of having a properly designed 50ohm transmission line to deliver the pulse from the detector.

Milnes, James S.; Howorth, J.

2005-03-01

288

A numerical study of the flow-induced vibration characteristics of a voice-producing element for laryngectomized patients  

PubMed Central

A computational model for exploring the design of a voice-producing voice prosthesis, or voice-producing element (VPE), is presented. The VPE is intended for use by laryngectomized patients who cannot benefit from current speech rehabilitation techniques. Previous experiments have focused on the design of a double-membrane voice generator as a VPE. For optimization studies, a numerical model has been developed. The numerical model introduced incorporates the finite element (FE) method to solve for the flow-induced vibrations of the VPE system, including airflow coupled with a mass-loaded membrane. The FE model includes distinct but coupled fluid and solid domains. The flow solver is governed by the incompressible, laminar, unsteady Navier–Stokes equations. The solid solver allows for large deformation, large strain, and collision. It is first shown that the model satisfactorily represents previously published experimental results in terms of frequency and flow rate, enabling the model for use as a design tool. The model is then used to study the influence of geometric scaling, membrane thickness, membrane stiffness, and slightly convergent or divergent channel geometry on the model response. It is shown that physiological allowable changes in the latter three device parameters alone will not be sufficient to generate the desired reduction in fundamental frequency. However, their effects are quantified and it is shown that membrane stiffness and included angle should be considered in future designs.

Thomson, S.L.; Tack, J.W.; Verkerke, G.J.

2014-01-01

289

A numerical study of the flow-induced vibration characteristics of a voice-producing element for laryngectomized patients.  

PubMed

A computational model for exploring the design of a voice-producing voice prosthesis, or voice-producing element (VPE), is presented. The VPE is intended for use by laryngectomized patients who cannot benefit from current speech rehabilitation techniques. Previous experiments have focused on the design of a double-membrane voice generator as a VPE. For optimization studies, a numerical model has been developed. The numerical model introduced incorporates the finite element (FE) method to solve for the flow-induced vibrations of the VPE system, including airflow coupled with a mass-loaded membrane. The FE model includes distinct but coupled fluid and solid domains. The flow solver is governed by the incompressible, laminar, unsteady Navier-Stokes equations. The solid solver allows for large deformation, large strain, and collision. It is first shown that the model satisfactorily represents previously published experimental results in terms of frequency and flow rate, enabling the model for use as a design tool. The model is then used to study the influence of geometric scaling, membrane thickness, membrane stiffness, and slightly convergent or divergent channel geometry on the model response. It is shown that physiological allowable changes in the latter three device parameters alone will not be sufficient to generate the desired reduction in fundamental frequency. However, their effects are quantified and it is shown that membrane stiffness and included angle should be considered in future designs. PMID:17662296

Thomson, S L; Tack, J W; Verkerke, G J

2007-01-01

290

Molecular dynamics simulation studies of dielectric response and vibrational energy relaxation in photoactive yellow protein and green fluorescent protein  

NASA Astrophysics Data System (ADS)

The first step in the photocycle of many proteins involves conformational change of a chromophore or a charge transfer reaction following photoexcitation. To explore the response of the protein and solvent environment to photoexcitation of the chromophore in photoactive yellow protein (PYP) and green fluorescent protein (GFP) we carried out molecular dynamics simulations of the dielectric response and vibrational energy relaxation (VER) from the chromophore to the protein and solvent. In PYP the time scale of the protein response, mainly contributed by Tyr42 and Glu46, to photoexcitation appears prominently between 0.1 and 0.3 picoseconds. The frequency-dependent VER rate also reveals dynamic coupling between the chromophore and residues that hydrogen bond to it. Resonances in the VER rate appear at frequencies comparable to the oscillations observed in recent fluorescence decay studies. In GFP, which undergoes excited state proton transfer about 10 ps following photoexcitation that may be assisted by specific chromophore vibrations, both the protein and water molecules inside the ?-barrel surrounding the chromophore mediate the dielectric response.

Xu, Yao; Gnanasekaran, Ramachandran; Leitner, David

2012-02-01

291

The influence of mechanical vibrations on human response in tall buildings with reference to Geomagnetic effects  

Microsoft Academic Search

It is stated that the indoor climate in high-rise buildings cannot be regarded as satisfactory in spite of the fact that it fulfils criteria of thermal, acoustic and light standards. Probably one of the factors which should not be omitted is the Geomagnetic field which affects (under specific conditions such as vibrations of a building) the persons occupying the inner

J. R. Kotleba; P. Sobotka

1986-01-01

292

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

293

Vibration response of printed circuit board in wide range of temperature. Characterization of PCB materials  

Microsoft Academic Search

Stiffness of printed circuit boards (PCB) has a great impact on reliability of solder joints. Vibrations or external stress loading lead to stress accumulation within solder joint area. Depending on intensity, inducted stress can be relieved by creep or fractures of solder joint. Intensity of inducted stress depends on loading conditions as well as properties of joined materials (specially stiffness

Przemyslaw Matkowski; Rafal Zawierta; Jan Felba

2009-01-01

294

Nonlinear Vibrations and Frequency Response Analysis of a Cantilever Beam Under Periodically Varying Magnetic Field  

Microsoft Academic Search

In this paper, nonlinear vibration of a cantilever beam with tip mass subjected to periodically varying axial load and magnetic field has been studied. The temporal equation of motion of the system containing linear and nonlinear parametric excitation terms along with nonlinear damping, geometric and inertial types of nonlinear terms has been derived and solved using method of multiple scales.

Barun Pratiher; Santosha K. Dwivedy

2011-01-01

295

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

Microsoft Academic Search

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

M. F. Lumentut; I. M. Howard

296

Use of scaled-down models for predicting vibration response of laminated plates  

Microsoft Academic Search

An analytical investigation was undertaken to show how and to what extent similitude theory can be applied in the design of scaled-down models. Through similitude the necessary similarity conditions, referred to herein as scaling laws, pertaining to free vibrations of laminated plates are derived. Establishment of scaling laws, based on the direct use of the governing equations is discussed and

J. Rezaeepazhand; G. J. Simitses

1995-01-01

297

Noise and vibration  

NASA Technical Reports Server (NTRS)

The characteristics of acoustic energy and protection of humans from noise during space flight are described. Vibration characteristic factors are also discussed, including the variety of vibration, systems and resonance, spacecraft operations, biodynamics, physiological and psychological effects, and subjective reactions. The criteria and limits for human exposure are cited.

Vongierke, H. E.; Nixon, C. W.; Guignard, J. C.

1975-01-01

298

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.

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

2014-01-01

299

Correlations between biodynamic characteristics of human hand–arm system and the isolation effectiveness of anti-vibration gloves  

Microsoft Academic Search

The objective of this study was to identify major individual factors that are directly associated with the effectiveness of anti-vibration gloves. Two series of experiments were performed. The first experiment measured the apparent mass of hand–arm system. The second one measured the transmissibility of a typical anti-vibration glove using a palm adapter method recommended in ISO 10819 (International Organisation for

R. G. Dong; T. W. McDowell; D. E. Welcome; W. P. Smutz

2005-01-01

300

The influence of mechanical vibrations on human response in tall buildings with reference to Geomagnetic effects  

NASA Astrophysics Data System (ADS)

It is stated that the indoor climate in high-rise buildings cannot be regarded as satisfactory in spite of the fact that it fulfils criteria of thermal, acoustic and light standards. Probably one of the factors which should not be omitted is the Geomagnetic field which affects (under specific conditions such as vibrations of a building) the persons occupying the inner space. Interim measurements to verify this idea were made in which the EEG of a man and the mechanical vibrations on the top of a 76.4 m. high building were sensed and recorded. Application of Fourier analysis resulted in spectral densities and a correlation was found between records of MV and EEG on the double frequency as fundamental frequency of MV of a building, confirming the suggested hypothesis. Amplitudes were not measured and only one measurement was undertaken which prevented any statistical evaluation of the significance of the phenomenon.

Kotleba, J. R.; Sobotka, P.

1986-12-01

301

Study of T53 Engine Vibration.  

National Technical Information Service (NTIS)

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...

T. J. Walter

1978-01-01

302

Free vibration response of two-dimensional magneto-electro-elastic laminated plates  

Microsoft Academic Search

An approximate solution for the free vibration problem of two-dimensional magneto-electro-elastic laminates is presented to determine their fundamental behavior. The laminates are composed of linear homogeneous elastic, piezoelectric, or magnetostrictive layers with perfect bonding between each interface. The solution for the elastic displacements, electric potential, and magnetic potential is obtained by combining a discrete layer approach with the Ritz method.

Fernando Ramirez; Paul R. Heyliger; Ernian Pan

2006-01-01

303

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

304

Linear Response Properties Required to Simulate Vibrational Spectra of Biomolecules in Various Media  

NASA Astrophysics Data System (ADS)

We here present a combined VA, VCD, Raman and ROA vibrational study of phenyloxirane. We have simulated the vibrational absorption (VA), also called IR, vibrational circular dichroism (VCD), Raman scattering and Raman optical activity (ROA) intensities utilizing the density functional theory (DFT) B3LYP hybrid exchange correlation functional and other exchange-correlation functionals (PBE, PW91, PBE1) with the 6-31G(d,p), 6-31++G(d,p), cc-pVDZ, aug-cc-pVDZ, cc-pVTZ and augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis sets. Previously authors have focused on either the VA and VCD spectra or the Raman and ROA spectra of molecules, since the experimental and theoretical instruments and methods for calculating these quantities are quite distinct. Here we show that the combined analysis gives more information, especially with respect to the electric dipole, magnetic dipole, electric dipole - electric dipole polarizability, electric dipole - electric quadrupole polarizability and electric dipole - magnetic dipole polarizability changes during the various induced transitions. The coupling of vibrational and electronic excitations may be used to aid in understanding the photo induced chemical reactivity observed in many systems. This work is a continuation of our goal to interpret the results of experimental studies on the basis of theoretical results, which can help to understand the structure and function of proteins, other biomolecules and ligands in their native environments. As the physical tools used to observe and study biological processes have evolved, so have the theoretical methods and models to interpret, understand and completely utilize the results of these new measurements. The work on developing methods for modeling amino acids, peptides, proteins and ligands in both the non aqueous (lipid) and aqueous environments has involved, of course, many groups. A review of our contributions to this field has recently been presented. In addition to interpreting existing and new experimental results, we will discuss structural, energetic, conformational, and vibrational studies on a variety of systems that have been used to test and validate levels of theory, and in addition to suggest modifications to existing levels of theory, which can make them even more useful than they currently are.

Jalkanen, K. J.; Würtz Jürgensen, V.; Degtyarenko, I. M.

305

Particle characteristics responsible for effects on human lung epithelial cells.  

PubMed

Some recent epidemiologic investigations have shown an association between increased incidence of respiratory symptoms and exposure to low levels of particulate matter (PM*) less than 10 microm or less than 2.5 microm in aerodynamic diameter (PM10 and PM2.5, respectively). If particulates are causally involved with respiratory symptoms, it is important to understand which components may be responsible. However, increasing evidence suggests that transition metals present in particles, especially iron, generate reactive oxygen species (ROS) that may be involved in producing some of the observed respiratory symptoms. The hypothesis for this study is twofold: bioavailable transition metals from inhaled airborne particulates catalyze redox reactions in human lung epithelial cells, leading to oxidative stress and increased production of mediators of pulmonary inflammation: and the size, transition metal content, and mineral speciation of particulates affect their ability to cause these effects. This work focused on the relation between physical characteristics of particles (eg, size, bioavailable transition metal content, and mineral speciation) and their ability to generate hydroxyl radicals in cell-free systems and to cause oxidative stress, which results in the synthesis of mediators of pulmonary inflammation in cultured human lung epithelial cells. These relations were studied by comparing size-fractionated, chemically characterized coal fly ash (CFA) produced by combustion of three different coals to obtain milligram quantities of ash. One transition metal, iron, was studied specifically because it is by far the predominant transition metal in CFA. In addition, smaller quantities of particles from gasoline engines, diesel engines, and ambient air were studied. Phosphate buffer soluble fractions from particles from all sources were capable of generating ROS, as measured by production of malondialdehyde (MDA) from 2-deoxyribose. This activity was inhibited over 90% for all particles by the metal chelator N-[5-[3-[(5-aminopentyl)hydroxycarbamoyl]propionamidol-pentyl]-3-[[5-(N-hydroxyacetamido)pentyl]carbamoyl]propionohydroxamic acid (desferrioxamine B, or DF), strongly suggesting that transition metal(s), probably iron, were responsible. Particles from coal or gasoline combustion had greater ability to produce ROS than particles from diesel combustion. Iron was mobilized by citrate (at pH 7.5) from particles of all sources tested; gasoline combustion particles were the only particles not analyzed for iron mobilization because there were not enough particles for the iron mobilization assay. CFA particles were size-fractioned; the amount of iron mobilized by citrate was inversely related to the size of particles and also depended on the source of coal. Iron from the CFA particles was responsible for inducing the iron-storage protein ferritin in cultured human lung epithelial cells (A549 cells). The amount of iron mobilized by citrate was directly proportional to the amount of ferritin induced in the A549 cells. Iron from the CFA was also responsible for inducing the inflammatory mediator interleukin (IL) 8 in A549 cells. Iron existed in several species in the fly ash, but the bioavailable iron was associated with the glassy aluminosilicate fraction, which caused ferritin and IL-8 to be induced in the A549 cells. In crustal dust, another component of urban particulates, iron was associated with oxides and clay but not with aluminosilicates. The crustal dust contained almost no iron that could be mobilized by citrate. Iron could be mobilized from diesel combustion particulates, but at a much lower level than for all other combustion particles. Samples of ambient PM2.5 collected in Salt Lake City over 5-day periods during one month varied widely in the amount of iron that could be mobilized. If bioavailable transition metals (eg, iron) are related to the specific biological responses outlined here, then the potential exists to develop in vitro assays to determine whether particulates of unknown composition and origin can cause ef

Aust, Ann E; Ball, James C; Hu, Autumn A; Lighty, JoAnn S; Smith, Kevin R; Straccia, Ann M; Veranth, John M; Young, Willie C

2002-12-01

306

Whole-body vertical biodynamic response characteristics of the seated vehicle driver  

Microsoft Academic Search

The vertical driving-point mechanical impedance characteristics applicable to seated vehicle drivers are measured in the 0.625–10Hz frequency range with excitation amplitudes ranging from 1.0 to 2.0ms?2 using a whole-body vehicular vibration simulator. The measurements are performed for seated subjects with feet supported and hands held in a driving position. Variations in the seated posture, backrest angle, and nature and amplitude

P.-É. Boileau; S. Rakheja

1998-01-01

307

Experimental IR and Raman spectra and quantum chemical studies of molecular structures, conformers and vibrational characteristics of nicotinic acid and its N-oxide  

NASA Astrophysics Data System (ADS)

FTIR and Raman spectra of nicotinic acid and its N-oxide have been recorded and analyzed. The stabilities, optimized molecular geometries, APT charges and vibrational characteristics for the two possible conformers of nicotinic acid and its N-oxide have been computed using DFT method. The E (trans) conformers of both the molecules are found to be more stable and less polar than their respective Z (cis) conformers. Due to addition of an O atom at the N 1 site in nicotinic acid the magnitudes of atomic charges on all the H atomic sites of the nicotinic acid N-oxide molecule are found to increase. Most of the vibrational frequencies have nearly the same magnitude for the two conformers of both the molecules. However, significant changes are noticed in their IR intensities, Raman activities and depolarization ratios of the Raman bands. The calculated frequencies have been correlated with the experimental frequencies.

Kumar, M.; Yadav, R. A.

2011-09-01

308

Vibrational characteristics of the double oxygen bridge in the NaIn(WO 4) 2 and NaSc(WO 4) 2 tungstates with wolframite structure  

NASA Astrophysics Data System (ADS)

The normal coordinate analysis of the tungsten-oxygen core in NaIn(WO 4) 2 and NaSc(WO 4) 2 crystals was performed. The Urey-Bradley force field and potential energy distribution (PED) were applied in the internal and external phonon calculations for the W 4O 22Na 2In 2 molecular system. The dynamics of the asymmetric WO 2W oxygen bridge as well as terminal W?O bonds were analyzed and discussed. The vibrational characteristics of the oxygen double bridge bond, i.e. vibration energy, symmetry, force constants, PED, atomic displacements, direction of the transition dipole moments and mean square amplitudes were obtained and discussed. The theoretical considerations were based on the polarized IR and Raman spectra of the materials studied.

Hanuza, J.; Macalik, L.; M?czka, M.; Lutz, E. T. G.; van der Maas, J. H.

1999-11-01

309

Epidemiological study of vibration syndrome in response to total hand-tool operating time.  

PubMed Central

The correlation between the severity of vibration syndrome and hand-tool operating time in chain saw workers has been studied. The total chain saw operating time was calculated by using the equation: chain saw operating hours/day X days/year X years, and 266 chain saw operators were classified into four groups (0-2000 h, 2000-5000 h, 5000-8000 h, over 8000 h). Forty-six forestry workers not using chain saws were used as controls. The prevalence rates of symptoms were checked and statistically compared in each group. In the group with under 2000 hours' experience, symptoms were generally confined to tingling, numbness, or pain; with 2000-5000 hours peripheral nerve and circulatory disturbances, including Raynaud's phenomenon, and muscle and general body conditions were influenced to some degree; with 5000-8000 hours' functional changes were noted; while with over 8000 hours about half the operators suffered severely from functional or organic changes due to vibration.

Miyashita, K; Shiomi, S; Itoh, N; Kasamatsu, T; Iwata, H

1983-01-01

310

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

311

Seasonal variations in vibrational spectra of the sea surface nanolayer and their relation to characteristic parameters for phytoplankton activity  

NASA Astrophysics Data System (ADS)

The sea surface nanolayer is a very thin organic substance layer, down to monomolecular thickness. It is found on top of the sea surface microlayer, which in turn comprises roughly the uppermost millimeter of the water column. The nanolayer constitutes the actual interface between ocean and atmosphere and plays an important role in all exchange processes of matter and energy between ocean and atmosphere. Nevertheless, knowledge about formation and development of the sea surface nanolayer in the course of the year is very limited. In this study we present surface-specific observations of the sea surface nanolayer development over a period of three and a half years. Samples of the sea surface have been taken monthly at Boknis Eck Time Series Station (Eckernförde Bay, southwestern Baltic Sea) by screen sampling. From surface-sensitive vibrational spectra obtained by nonlinear sum frequency generation spectroscopy (SFG), information on amount, structure and composition of the organic nanolayer material was extracted. SFG has been introduced by us as a new method to study the ocean nanolayer quite recently [1,2]. The abundance of nanolayer material was found to follow a pronounced yearly periodicity, with larger amounts of material present from mid to end of summer. A substantial time lag of about 2.5 months between spring algal bloom maxima and abundance maxima of nanolayer material has been observed. In contrast to common perception, this shows that high phytoplankton abundance and pronounced nanolayers are not directly related to each other. Variations in the appearance of the spectra serve as indicators for changes in structure and chemical composition of the nanolayer. The accumulation of carbohydrate-rich material in late summer provides a possible explanation for the observed spectral changes. We propose that sloppy feeding of zooplankton as well as photochemical and/or microbial processing of organic material present in the microlayer is responsible for the periodicity of nanolayer intensity and its temporal shift with respect to other influential factors. References [1] K. Laß, G. Friedrichs, J. Geophys. Res. 116 (2011) C08042/1-15 [2] K. Laß, J. Kleber, G. Friedrichs, Limnol. Oceanogr.: Methods 8 (2010) 216-228

Laß, Kristian; Bange, Hermann W.; Friedrichs, Gernot

2013-04-01

312

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

313

Vibration characteristics of the HPOTP (High-Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)  

NASA Technical Reports Server (NTRS)

Attention is given to rotor dynamic problems that have been encountered and eliminated in the course of Space Shuttle Main Engine (SSME) development, as well as continuing, subsynchronous problems which are being encountered in the development of a 109-percent power level engine. The basic model for the SSME's High Pressure Oxygen Turbopump (HPOTP) encompasses a structural dynamic model for the rotor and housing, and component models for the liquid and gas seals, turbine clearance excitation forces, and impeller diffuser forces. Linear model results are used to examine the synchronous response and stability characteristics of the HPOTP, with attention to bearing load and stability problems associated with the second critical speed. Differences between linear and nonlinear model results are discussed and explained in terms of simple models. Simulation results indicate that while synchronous bearing loads can be reduced, subsynchronous motion is not eliminated by seal modifications.

Childs, D. W.; Moyer, D. S.

1984-01-01

314

A theoretical study on the influence of the track on train-induced ground vibration  

Microsoft Academic Search

An investigation is presented on the nature of train-induced ground vibration propagation. It is based on a theoretical model for the track and a layered ground. Results are given of the responses of the ground and track to a moving harmonic or quasi-static load on the rails. The dispersion characteristics of the propagating modes of vibration in the track and

X. Sheng; C. J. C. Jones; D. J. Thompson

2004-01-01

315

Serotonergic characteristics of rainbow trout divergent in stress responsiveness  

Microsoft Academic Search

Juvenile rainbow trout divergent in their cortisol response to confinement stress (HR: high responsive or LR: low responsive fish) were exposed to either 1 or 3 h of confinement stress. Untreated fish served as control. After the exposure blood and brain samples were collected. From the blood samples, the levels of cortisol and catecholamines were determined, while the brain serotonergic and

J. Schjolden; K. G. T. Pulman; T. G. Pottinger; O. Tottmar; S. Winberg

2006-01-01

316

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

317

Re-evaluation of the absolute threshold and response mode of the most sensitive known "vibration" detector, the cockroach's subgenual organ: a cochlea-like displacement threshold and a direct response to sound.  

PubMed

Earlier accounts claim from indirect measurements that the subgenual organ (SGO) in the proximal tibia of the cockroach leg can detect vibrational displacements down to 0.002 nm, two orders of magnitude below the threshold for vertebrate hair cells in the cochlea. The SGO vibration threshold is redetermined here more directly by a new method on a cantilever beam, while controlling for particular acoustic and vibrational artifacts that might have compromised earlier efforts. The threshold is revised upwards to about 0.2 nm in the most sensitive preparation, about the same as the cochlea. Recently, it has been determined that the cockroach SGO also has an auditory response, and the data here on subthreshold summation and response-intensity relationships provide further evidence that sound and contact vibration are both sensed by the same receptor neurons. Direct measurements rule out the prevailing hypothesis that sound is detected indirectly as induced vibration of the ground, and also weigh strongly against any significant involvement of generalized leg resonance in acoustic pick-up. The results fit with a recent proposal that the auditory response is direct, and that acoustic fluctuations inside the tracheae may be the primary response mode in the transduction of both vibration and sound. PMID:7815071

Shaw, S R

1994-09-01

318

Vibrational characteristics of the double oxygen bridge in the NaIn(WO 4) 2 and NaSc(WO 4) 2 tungstates with wolframite structure  

Microsoft Academic Search

The normal coordinate analysis of the tungsten–oxygen core in NaIn(WO4)2 and NaSc(WO4)2 crystals was performed. The Urey–Bradley force field and potential energy distribution (PED) were applied in the internal and external phonon calculations for the W4O22Na2In2 molecular system. The dynamics of the asymmetric WO2W oxygen bridge as well as terminal W?O bonds were analyzed and discussed. The vibrational characteristics of

J. Hanuza; L Macalik; M M?czka; E. T. G Lutz; J. H van der Maas

1999-01-01

319

Characteristics and the Mechanism of Bacteriorhodopsin Photoelectric Response.  

PubMed

Oriented bacteriorhodopsin films were prepared on ITO conductive glass by using electrophoretic or Langmuir-Blodgett methods to construct photocells. Pulse response photovoltages under stimulation of pulsed laser and differentialresponse signals under irradiation of discontinued light were respectively measured, and the origins of the two responses and their correlation are analyzed. The pulse response photovoltage initiated from the ultrafast charge separation of the retinal and the proton translocation, followed by the deprotonation and reprotonation of the Schiff base and its surrounding amino acids. This was a quick response and was the preceding reaction of the differential response. The differential response was caused by the charging and discharging of the continuous proton current of the BR light-driven proton pump at the light-on and light-off, as well as the coupling mode of the measuring circuit, which was a slow process. PMID:12040420

Yao, Bao-Li; Wang, Ying-Li; Hu, Kun-Sheng; Chen, De-Liang; Zheng, Yuan; Lei, Ming

2001-01-01

320

Cosine response characteristics of some radiometric and photometric sensors  

Microsoft Academic Search

Global and diffuse irradiance and illuminance are measured with instruments that are assumed to have true cosine responses. From one refereed paper, some institutional reports, and by word-of-mouth, it is generally known that no instrument is perfect in this regard. This paper reports on measurements of cosine responses for several commercial instruments and on the cosine response of a multi-filter

J. J. Michalsky; L. C. Harrison; W. E. Berkheiser

1995-01-01

321

A stochastic averaging approach for printed circuit boards with nonlinear damping characteristics subjected to random vibration loads  

Microsoft Academic Search

Today many electronic devices consist of plate-like printed circuit boards carrying electric and electronic components mounted in some sort of housing. Depending on the application, these electronic devices may be subjected to severe random vibration loads over their lifetime, e.g. in automotive or aerospace environments. The present work shows that although state-of-the-art printed circuit boards are typically structurally linear with

N. Hoffmann; L. Gaul

2006-01-01

322

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.

323

Transition Response Characteristics of Heat-Assisted Magnetic Recording and Their Performance With MTR Codes  

Microsoft Academic Search

The response of a heat-assisted magnetic recording (HAMR) system is very sensitive to the laser spot position. The response is determined by transition characteristics like the center, curvature, and length. In this paper, by using the thermal Williams-Comstock model and the microtrack model, the effects of laser spot position on transition characteristics are investigated for both longitudinal and perpendicular recording

Rathnakumar Radhakrishnan; M. Fatih Erden; Ching He; Bane Vasic

2007-01-01

324

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

325

Cosine response characteristics of radiometric and photometric sensors  

SciTech Connect

Global and diffuse irradiance and illuminance are measured with instruments that are assumed to have true cosine responses. It is known, largely from reports with a limited distribution or by word of mouth, that no instrument is perfect in this regard. This paper reports on measurements of cosine responses for several instrument types and manufacture familiar to the solar radiation measurement community. The measurements were made with an automated cosine response test bench using the same protocol for each instrument. The cosine bench measures with variable angular resolution as fine as 0.25 degrees. The automated rotation is in one plane. A manual rotation allows measurements for other azimuths. 6 refs.

Michalsky, J.J.; Harrison, L.C.; Berkheiser, W.E. III

1992-05-01

326

Cosine response characteristics of radiometric and photometric sensors  

SciTech Connect

Global and diffuse irradiance and illuminance are measured with instruments that are assumed to have true cosine responses. It is known, largely from reports with a limited distribution or by word of mouth, that no instrument is perfect in this regard. This paper reports on measurements of cosine responses for several instrument types and manufacture familiar to the solar radiation measurement community. The measurements were made with an automated cosine response test bench using the same protocol for each instrument. The cosine bench measures with variable angular resolution as fine as 0.25 degrees. The automated rotation is in one plane. A manual rotation allows measurements for other azimuths. 6 refs.

Michalsky, J.J.; Harrison, L.C.; Berkheiser, W.E. III.

1992-01-01

327

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

328

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

329

Adaptation and temporal characteristics of the insect visual response  

Microsoft Academic Search

The effects of light adaptation on temporal characteristics of the electroretinogram were studied in two species of diurnal insects. Latency and time to reach peak amplitude (Tm) of the initial deflection of the ERG were the temporal measures used. The experimental regime consisted of repeatedly light-adapting the eye with a conditioning stimulus (S1 and determining the effects of eachS1 on

F. Edward Dudek; Harold Koopowitz

1973-01-01

330

Analytical and experimental study of vibrations in a gear transmission  

NASA Technical Reports Server (NTRS)

An analytical simulation of the dynamics of a gear transmission system is presented and compared to experimental results from a gear noise test rig at NASA Lewis. The analytical procedure developed couples the dynamic behaviors of the rotor-bearing-gear system with the response of the gearbox structure. Transient and steady-state vibrations of the gearbox system are presented in the time and frequency domains. The vibration characteristics of a simple single-mesh-gear noise test rig are modeled. The numerical simulations are compared to experimental data measured under typical operating conditions. The system natural frequencies, peak vibration amplitudes, and gear mesh frequencies are generally in good agreement.

Choy, F. K.; Ruan, Y. F.; Zakrajsek, J. J.; Oswald, F. B.; Coy, J. J.

1991-01-01

331

Application of a photonic crystal fiber LPG for vibration monitoring  

NASA Astrophysics Data System (ADS)

A fiber optic sensor based on a long-period grating (LPG) inscribed in a photonic crystal fiber is investigated for vibration sensing for structural monitoring applications. In this paper, preliminary results are shown demonstrating the sensor ability to detect vibration induced in a test structure. The sensor frequency response when attached to a loudspeaker-acrylic plate stimulation system (tested in the range from 40 Hz to 2.5 kHz) is analyzed using an intensity based scheme with a tunable laser. An alternative interrogation scheme, where the vibration signal is retrieved from a spectral scan, is also demonstrated and analyzed showing promising characteristics for structural health monitoring.

Nascimento, I. M.; Chesini, G.; Sousa, Marco; Osório, Jonas H.; Baptista, J. M.; Cordeiro, Cristiano M. B.; Jorge, Pedro A. S.

2013-05-01

332

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

333

Exposure-response relationship in the hand-arm vibration syndrome: an overview of current epidemiology research  

Microsoft Academic Search

The complex of vascular, neurologic, and osteoarticular disorders occurring in the upper limbs of vibration-exposed workers\\u000a is called hand-arm vibration syndrome. There is epidemiologic evidence for an increased occurrence of peripheral sensorineural\\u000a disorders in occupational groups working with vibrating tools. An excess risk for wrist osteoarthrosis and for elbow arthrosis\\u000a and osteophytosis has been reported in workers exposed to shocks

Massimo Bovenzi

1998-01-01

334

Attitudes towards corporate social responsibility and perceived importance of social responsibility information characteristics in a decision context  

Microsoft Academic Search

This study addressed the questions of perceived importance of social responsibility information (SRI) characteristics in a decision context, as well as the attitudes of institutional investors toward social responsibility involvement. The results showed that SRI presently disclosed in company annual reports did not have any significant impact on institutional investors' decisions. However, if SRI were presented in quantified, financial form,

Hai Yap Teoh; Godwin Y Shiu

1990-01-01

335

School Refusal Behavior: Prevalence, Characteristics, and the Schools' Response.  

ERIC Educational Resources Information Center

A survey of 288 elementary and secondary North Dakota schools found 75% had a school refusal behavior (SRB) identification system in place, 57% had a school psychologist available, principals were most frequently responsible for identifying school refusers, 2.3% of students were identified as school refusers of which 49% falsely claimed illness,…

Stickney, Marcella I.; Miltenberger, Raymond G.

1998-01-01

336

Organizational characteristics and employer responses to employee substance abuse  

Microsoft Academic Search

Working within an integrative framework of human resource management (HRM) in context (Jackson & Schuler, 1995), and theorizing from an integrated institutional and resource dependence perspective (Oliver, 1991), this study investigated whether factors in the internal and external organizational environments are associated with the presence of a counseling\\/rehabilitative response by employers to identified employee substance abuse. Data were collected at

Stuart H. Milne; Terry C. Blum

1998-01-01

337

Organizational Characteristics and Employer Responses to Employee Substance Abuse  

Microsoft Academic Search

Working within an integrative framework of human resource management (HRM) in context (Jackson & Schuler, 1995), and theorizing from an integrated institutional and resource dependence perspective (Oliver, 1991), this study investigated whether factors in the internal and external organizational environments are associated with the presence of a counseling\\/rehabilitative response by employers to identified employee substance abuse. Data were collected at

Stuart H. Milne; Terry C. Blum

1998-01-01

338

Measuring the vibrational response of the mouse ear using coherently interleaved optical coherence tomography  

NASA Astrophysics Data System (ADS)

Optical coherence tomography (OCT) is becoming a popular tool for imaging morphology in the middle and inner ear. Vibratory measurements of the structures of the ear facilitate better understanding of the function and limitations of the ear. We have developed an algorithm that enables a standard spectrometer based OCT system to measure the full spectrum (90 kHz) frequency response of the mouse ear by incorporating coherently interleaved sampling, increasing the effective Nyquist rate of the system by a factor of 5+. The algorithm is evaluated by measuring the frequency response of a mouse tympanic membrane to a pure tone stimulus.

Shelton, Ryan; Gao, Simon; Oghalai, John S.; Applegate, Brian E.

2012-02-01

339

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

340

[Pathogenesis of motor disorders in patients with vibration disease caused by local vibration (clinico-electroneuromyographic study].  

PubMed

The author provides the data on clinical, neurophysiological examinations of 195 patients suffering from vibration disease, stages I and II, due to local vibration. Three types of axonal injuries were established: axonal degeneration, demyelinization of the distal part of axon and demyelinization of its proximal part. All the three types of neural disorders were attended by synaptic alterations with a decrement of the M-response and the syndrome of "working in". The initial manifestations of neurophysiological pathology were axonal degenerative disorders with changes in neuromuscular transmission; on longer exposure to vibration there appeared the signs of demyelination. The length of service with vibrating tools is given fr the occupational groups with above-indicated neural disorders. The patterns of motor disorders did not depend on the type of vibrating tools, whereas the localization of the pathological alterations was related to the characteristic features of an industry. PMID:1962991

Liubimova, R P

1990-01-01

341

Noninvasive determination of bone mechanical properties using vibration response: A refined model and validation in vivo  

Microsoft Academic Search

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

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

1996-01-01

342

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

343

Picosecond time response characteristics of microchannel plate PMT detectors  

Microsoft Academic Search

The output pulse width in the time response of photo-multiplier tubes (PMT) is much faster in micro-channel plate (MCP) models compared to more standard dynode chain PMTs due to a vastly reduced variation in the path length of the electrons through the amplifying system. Typically the pulse widths can be in the region of 200ps compared to the nanosecond domain

James S. Milnes; J. Howorth

2005-01-01

344

Vibration response of spalled rolling element bearings: Observations, simulations and signal processing techniques to track the spall size  

NASA Astrophysics Data System (ADS)

Fatigue in rolling element bearings, resulting in spalling of the races and/or rolling elements, is the most common cause of bearing failure. The useful life of the bearing may extend considerably beyond the appearance of the first spall and a premature removal of the bearing from service can be very expensive, but on the other hand chances cannot be taken with safety of machines or personnel. Previous studies indicated that there might be two parts to the defect vibration signal of a spalled bearing, the first part being originating from the entry of the rolling element into the fault (de-stress) and the second part being due to the departure of the rolling element from the fault (re-stress). This is investigated in this paper using vibration signatures of seeded faults at different speeds. The acceleration signals resulting from the entry of the rolling element into the spall and exit from it were found to be of different natures. The entry into the fault can be described as a step response, with mainly low frequency content, while the impact excites a much broader frequency impulse response. The latter is the most noticeable and prominent event, especially when examining the high pass filtered response or the enveloped signal. In order to enable a clear separation of the two events, and produce an averaged estimate of the size of the fault, two approaches are proposed to enhance the entry event while keeping the impulse response. The first approach (joint treatment) utilizes pre-whitening to balance the low and high frequency energy, then octave band wavelet analysis to allow selection of the best band (or scale) to balance the two pulses with similar frequency content. In the second approach, a separate treatment is applied to the step and the impulse responses, so that they can be equally represented in the signal. Cepstrum analysis can be used to give an average estimate of the spacing between the entry and impact events, but the latter can also be assessed by an arithmetic estimation of the mean and standard deviation of the event separation for a number of realizations, in particular for the second approach. In order to determine the effects of various simulations and signal processing parameters on the estimated delay times, the entry and exit events were simulated as modified step and impulse responses with precisely known starting times. The simulation was also found useful in pointing to artefacts associated with the cepstrum calculation, which affect even the simulated signals, and have thus prompted modifications of the processing of real signals. The results presented for the two approaches give a reasonable approximation of the measured fault widths (double the spacing between the entry and impact events) under different speed conditions, but the method of separate treatment is somewhat better and is thus recommended.

Sawalhi, N.; Randall, R. B.

2011-04-01

345

Effect of granular media on the vibrational response of a resonant structure: theory and experiment.  

PubMed

The acoustic response of a structure that contains a cavity filled with a loose granular material is analyzed. The inputs to the theory are the effective masses of each subsystem: that of the empty-cavity resonating structure and that of the granular medium within the cavity. This theory accurately predicts the frequencies, widths, and relative amplitudes of the various flexural mode resonances observed with rectangular bars, each having a cavity filled with loose tungsten granules. Inasmuch as the dominant mechanism for damping is due to adsorbed water at the grain-grain contacts, the significant effects of humidity on both the effective mass of the granular medium as well as on the response of the grain-loaded bars are monitored. Here, depending upon the humidity and the preparation protocol, it is possible to observe one, two, or three distinct resonances in a wide frequency range (1-5 kHz) over which the empty bar has but one resonance. These effects are understood in terms of the theoretical framework, which may simplify in terms of perturbation theories. PMID:21110572

Valenza, John J; Hsu, Chaur-Jian; Johnson, David Linton

2010-11-01

346

Effect of lead rubber bearing characteristics on the response of seismic-isolated bridges  

Microsoft Academic Search

A parametric study is conducted to investigate the effect of lead rubber bearing (LRB) isolator and ground motion characteristics\\u000a on the response of seismic isolated bridges. The purpose was to investigate the most favorable parameters of the LRB for minimum\\u000a earthquake response of the isolated bridge system for different ground motions. The important parameters included are: ground\\u000a motion characteristic by

Asif Hameed; Min-Se Koo; Thang Dai Do; Jin-Hoon Jeong

2008-01-01

347

DOSE-RESPONSE Relationships Between Whole-Body Vibration and Lumbar Disk DISEASE—A Field Study on 388 Drivers of Different Vehicles  

NASA Astrophysics Data System (ADS)

In a longitudinal study, the dose-response relationships between long term occupational exposure to whole-body vibration and degenerative processes in the lumbar spine caused by the lumbar disks were examined. From 1990 to 1992, 388 vibration-exposed workers from different driving jobs were examined medically and by lumbar X-ray. For each individual, a history of all exposure conditions was recorded, and a cumulative vibration dose was calculated allowing comparisons between groups of low, middle, and high intensity of exposure. 310 subjects were selected for a follow-up four years later, of whom 90·6% (n=281) agreed to participate. In comparing the exposure groups, the results indicate that the limit value ofazw(8h)=0·8 m/s2should be reviewed. The best fit between the lifelong vibration dose and the occurrence of a lumbar syndrome was obtained by applying a daily reference ofazw(8h)=0·6 ms2as a limit value. The results became more distinct still when only those subjects were included in the statistical analysis who had had no lumbar symptoms up to the end of the first year of exposure. The prevalence of lumbar syndrome is 1·55 times higher in the highly exposed group when compared to the reference group with low exposure (CI95%=1·24/1·95). Calculating the cumulative incidence of new cases of lumbar syndrome in the follow-up period yields a relative risk ofRRMH=1·37 (CI95%=0·86/2·17) for the highly exposed group. It is concluded that the limit value for the calculation of an individual lifelong vibration dose should be based on a daily reference exposure ofazw(8h)=0·6 m/s2. With increasing dose it is more and more probable that cases of lumbar syndrome are caused by exposure to vibration.

Schwarze, S.; Notbohm, G.; Dupuis, H.; Hartung, E.

1998-08-01

348

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

349

Giant magnetostrictive actuators for active vibration control  

Microsoft Academic Search

Giant magnetostrictive actuators are designed and fabricated with home-made TbDyFe magnetostrictive rods. The corresponding static and dynamic characteristics are tested. The total output displacement can be obtained up to 100 µm and the output force up to 1500 N. The dynamic responses of input and output are accordant and have a small hysteresis. Experiments on active vibration control are implemented

Tianli Zhang; Chengbao Jiang; Hu Zhang; Huibin Xu

2004-01-01

350

Ground vibration model studies for APS storage ring.  

National Technical Information Service (NTIS)

An analytical ground vibration model is developed for study of the vibration effects on the beam motion in the Advanced Photon Source (APS) storage ring. The different physical parameters associated with the wave characteristics and the vibration modes ne...

R. K. Koul

1994-01-01

351

Ab initio determination of geometries and vibrational characteristics of building blocks of organic super-conductors: TTF and its derivatives.  

PubMed

Molecular behavior of the building block {[2-(1,3-dithiole-2-ylidene)-1,3-dithiole] ? tetrathiafulvalene (TTF)} of organic superconductors have been investigated along with its three derivatives, namely, {[2-(1,3-dioxole-2-ylidene)-1,3-dioxole] ? tetraoxafulvalene (TOF)}; [2,2]-bi -[[1,3] oxathiolylidene] ? Der I and 2-(3H-Furan-2-ylidene)-[1,3] oxathiole ? Der II. The properties of the molecules such as molecular geometries, frontier MOs and vibrational spectra have been investigated by using DFT method at the B3LYP level employing 6-311++G(d,p) basis set. The geometrical parameters and atomic charges on various atomic sites of the TTF, TOF, Ders I and II suggest extended conjugation in these systems. The present calculations lead to the reassignments for of some of the fundamentals and new interpretations for some of the observed IR and Raman frequencies. One of the two modes involved in the Fermi resonance giving rise to the doublet 1555 and 1564 cm(-1) needed to be revised and another doublet 3083 and 3108 cm(-1) could be interpreted as a Fermi resonance doublet. Out of the two ?(C = C) modes under the a(1) species, the lower frequency mode is assigned to the ?(C = C) of the ring and the higher one to the ?(C = C) of the central C = C bond contrary to the assignment reported in literature. The conducting properties of these molecules depend mainly on this mode. PMID:23040970

Rani, P; Yadav, R A

2012-12-01

352

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

353

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

354

Effect of handle size and hand–handle contact force on the biodynamic response of the hand–arm system under z h -axis vibration  

Microsoft Academic Search

The influences of the handle size and of the hand forces exerted on a vibrating tool handle on the driving-point mechanical impedance (DPMI) response of the human hand–arm system have been investigated through laboratory measurements performed on seven adult male subjects. Measurements were performed with three instrumented cylindrical handles with different diameters (30, 40 and 50mm) exposed to two different

P. Marcotte; Y. Aldien; P.-É. Boileau; S. Rakheja; J. Boutin

2005-01-01

355

A comparative analysis of machining characteristics in ultrasonic assisted EDM by the response surface methodology  

Microsoft Academic Search

This paper comprehensively evaluates the influence of ultrasonic irradiation of spark gap on EDM characteristics for both planing and drilling operations. A set of comparative experiments were carried out and the analysis of the results was based on standard statistical techniques. The response surfaces and the corresponding response functions were determined for major performance indices, such as machining rate, tool

V. S. R. MURTI; P. K. PHILIP

1987-01-01

356

The Influence of Learning Characteristics on Evaluation of Audience Response Technology  

ERIC Educational Resources Information Center

Audience Response Technology (ART) has been widely adopted on college campuses, and prior research indicates that, on average, it receives positive evaluations from students. However, research has not yet examined how characteristics of students as learners influence their responses to ART. The current study examined aptitude for learning,…

MacGeorge, Erina L.; Homan, Scott R.; Dunning, John B.; Elmore, David; Bodie, Graham D.; Evans, Ed; Khichadia, Sangeetha; Lichti, Steven M.

2008-01-01

357

Plant growth in controlled environments in response to characteristics of nutrient solutions  

NASA Technical Reports Server (NTRS)

Plant growth in controlled environments in response to characteristics of nutrient solutions is discussed. Descriptions of experimental results concerning root acclimation to temperature, root and shoot acclimation to nitrogen stress, and growth response to NH4(+) and NO3(-) nutrition are included. A preliminary model validation to changing temperatures is presented.

Raper, C. D., Jr.

1982-01-01

358

Damping phenomena in a wire rope vibration isolation system  

Microsoft Academic Search

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

Michael L. Tinker; Malcolm A. Cutchins

1990-01-01

359

Damping phenomena in a wire rope vibration isolation system  

Microsoft Academic Search

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,

M. L. Tinker; M. A. Cutchins

1992-01-01

360

Damping and Forced Vibration Analyses of Viscoelastic Shells  

Microsoft Academic Search

The forced vibration response curves and damping characteristics of viscoelastic and sandwich viscoelastic shells are studied by a combination of the finite element and perturbation methods. The mathematical formulation is developed in a general form in order to take into account various viscoelastic models in the frequency domain. Frequency dependent Young modulus based on various Maxwell's model is used for

F. Abdoun; L. Azrar; E. M. Daya

2010-01-01

361

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

362

Investigation of a new vortex-induced vibration suppression device in laboratory experiments  

NASA Astrophysics Data System (ADS)

In order to mitigate vortex-induced vibration (VIV) of marine risers, especially to eliminate the phenomenon of frequency slock-in', a new suppression device of crescent-shaped flow spoiler was designed with seven different layout schemes. VIV model tests with six flow levels were conducted in a large wind-wave-current flume. In all cases, vibration responses in both in-line and cross-flow cases were measured. With the installation of suppression devices vibration frequency evolution of a riser was analyzed by Morlet wavelet transform. The principle of VIV suppression was interpreted through vibration characteristics. Fatigue life of the riser was calculated by the Palmgren-Miner rule. Compared with a bare riser, vibration of an outfitted riser with suppression devices disturbed the steady flow, the vibration amplitudes in the two flow directions were reduced, and the riser fatigue life was improved.

Zhang, Yongbo; Guo, Haiyan; Liu, Xiaochun; Li, Xiaomin

2012-06-01

363

The effect of the contact model on the impact-vibration response of continuous and discrete systems  

NASA Astrophysics Data System (ADS)

Impact is a phenomenon that is ubiquitous in mechanical design; however, the modeling of impacts in complex systems is often a simplified, imprecise process. In many high fidelity finite element simulations, an impractically large number of elements are required to model the constitutive properties of an impact event accurately. As a result, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, an artificially large penalty stiffness, or a single degree of freedom constitutive model for the impact dynamics that is specific to the type of materials involved (elastic, plastic, viscoelastic, etc.). In this paper, the effect of the contact model on the prediction of a system's dynamics is analyzed. In order to understand the effect of the impact model on the system's dynamics, simulations are conducted to investigate a single degree of freedom system, a two degrees of freedom system, and a continuous system, each with rigid stops limiting the amplitude of vibration. Five different contact models are considered: a coefficient of restitution method, a penalty stiffness method, two similar elastic-plastic constitutive models, and a dissimilar elastic-plastic constitutive model. Frequency sweeps and parametric studies show that simplified contact models can lead to incorrect assessments of the system's dynamics. In the worst case, periodic behavior can be predicted in a chaotic regime. Additionally, the choice of contact model can significantly affect the prediction of wear and damage in the system, as is evidenced by the prominence of chatter and high amplitude responses.

Brake, M. R.

2013-07-01

364

Impact of an acute bout of vibration on muscle contractile properties, creatine kinase and lactate dehydrogenase response.  

PubMed

The aim of this study was to assess the effects of a bout of whole body vibration (WBV) on muscle response and to determine whether this stimulus leads to muscle damage. Thirty healthy and physically active participants (mean ± SD; age: 21.8 ± 2.0 years; height: 176.7 ± 5.8 cm; body mass: 76 ± 6.8 kg and BMI: 23.1 ± 3.7 kg·m(-2)) participated in this study. Participants were randomly allocated in one of two groups, one of them performed a bout of 360 s WBV (frequency: 30 Hz; peak-to-peak displacement: 4 mm) (VIB) and the other one adopted a sham position (CON). Muscle contractile properties were analysed in the rectus femoris (RF) by using tensiomyography (TMG) 2 min before the warm-up and 2 min after intervention. Muscle damage was assessed by determining plasma creatine kinase (CK) and lactate dehydrogenase (LDH) levels at three time points; 5 min before warm-up and 1 h and 48 h after the intervention. TMG results showed a significant decrease in maximal displacement (p<0.05) and delay time (p<0.05) in VIB and in delay time (p<0.05) and relaxation time (p<0.05) in CON. Muscle damage markers showed significant group differences (p<0.05) for CK 1 h after the intervention. In addition, differences for CK 1 h after the intervention from baseline (p<0.05) were also observed in VIB. In conclusion, a 6-min bout of WBV results in an increase of muscle stiffness in RF and increased CK levels 1 h after intervention (returning to baseline within 48 h). PMID:24251744

de Hoyo, Moisés; Carrasco, Luis; Da Silva-Grigoletto, Marzo E; Sañudo, Borja; Caballero-Villarraso, Javier; Arriaza, Eva; Escobar, Maria Del Carmen

2013-01-01

365

String Vibrations  

NSDL National Science Digital Library

This site, by Andrew Davidhazy at the Rochester Institute of Technology, describes how to make interesting and artistic photographs of a vibrating string. Davidhazy explains how the string is vibrated, how the string is lit, and even the exposure time and the effect it has on the resulting image. Four images of the vibrating string are included.

2006-12-29

366

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

367

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

PubMed Central

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.

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

2013-01-01

368

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

369

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

370

Temperature-dependent dynamic response to flash heating of molecular monolayers on metal surfaces: vibrational energy exchange.  

PubMed

An ultrafast nonlinear coherent laser spectroscopy termed vibrational sum-frequency generation (SFG) was used to monitor vibrational transitions of a self-assembled monolayer (SAM) of 4-nitrobenzenethiolate (NBT) on Au after Au flash heating. Ultrafast thermoreflectance measurements showed the surface temperature jumps ?T were in the 35-250 K range. The NBT symmetric and antisymmetric nitro stretches ?sNO2 and ?asNO2 and a phenyl ring stretch ?CC were probed. Flash heating caused these transitions to lose intensity, shift, and broaden. The time dependences all had overshoot-decay-plateau structures. In the long-lived plateau, the SAM was in thermal equilibrium with the hot Au surface. The SFG plateau intensity losses of ?sNO2 and ?CC, two vibrations with parallel transition moments, were identical, indicating that the SFG intensity loss was caused by thermally induced SAM orientational disorder. The T-jump-induced frequency shifts of ?sNO2 and ?asNO2 were identical and opposite in sign. The rise times of the shifts were identical and equal to the ?3.5 ps time constant for the rise of Au surface temperature, which indicates that both shifts were caused by anharmonic coupling to the same lower-energy vibration. The temperature dependence of the ?sNO2 shift and width indicated that this vibration was the ?480 cm(-1) nitro bend. The ?sNO2 temperature dependence was interpreted using a vibrational energy exchange mechanism between the nitro stretch and bend. PMID:25031101

Berg, Christopher M; Sun, Yuxiao; Dlott, Dana D

2014-07-17

371

Current Response Characteristics of Microchannel Plates for Detection Vacuum-Ultraviolet Radiation  

Microsoft Academic Search

The current response characteristics of microchannel plates (MCPs) for detection of x-rays have been investigated using synchrotron radiation in the vacuum-ultraviolet (VUV) band (the wavelength range 20-80 nm). Calculation from a simple model to account the detection current of MCP are compared with the measured incident angle dependence of MCP response. The result indicates the effect of x-ray reflection within

Naohiro Yamaguchi; Yuuji Okamoto; Tamio Hara; Sadao Aoki

2004-01-01

372

A Patch Density Recommendation based on Convergence Studies for Vehicle Panel Vibration Response resulting from Excitation by a Diffuse Acoustic Field  

NASA Technical Reports Server (NTRS)

Fluid structural interaction problems that estimate panel vibration from an applied pressure field excitation are quite dependent on the spatial correlation of the pressure field. There is a danger of either over estimating a low frequency response or under predicting broad band panel response in the more modally dense bands if the pressure field spatial correlation is not accounted for adequately. Even when the analyst elects to use a fitted function for the spatial correlation an error may be introduced if the choice of patch density is not fine enough to represent the more continuous spatial correlation function throughout the intended frequency range of interest. Both qualitative and quantitative illustrations evaluating the adequacy of different patch density assumptions to approximate the fitted spatial correlation function are provided. The actual response of a typical vehicle panel system is then evaluated in a convergence study where the patch density assumptions are varied over the same finite element model. The convergence study results are presented illustrating the impact resulting from a poor choice of patch density. The fitted correlation function used in this study represents a Diffuse Acoustic Field (DAF) excitation of the panel to produce vibration response.

Smith, Andrew; LaVerde, Bruce; Jones, Douglas; Towner, Robert; Hunt, Ron

2013-01-01

373

Limit-Cycle Vibrations In Turbomachinery  

NASA Technical Reports Server (NTRS)

Paper presents theoretical study of vibrations in high-speed turbomachinery. Addresses relationship between two classes of vibrational phenomena previously studied separately: dynamic instabilities, including both those subject to linear analysis and limit-cycle instabilities in cases of nonlinear vibrational response, and subharmonic response to excitation caused by unbalance of rotor.

Ryan, S. G.

1994-01-01

374

Postural response to vibration of triceps surae, but not quadriceps muscles, differs between people with and without knee osteoarthritis.  

PubMed

Although proprioceptive impairments are reported in knee osteoarthritis (OA), there has been little investigation of the underlying causes. Muscle spindles make an important contribution to proprioception. This study investigated whether function of quadriceps, triceps surae, and tibialis anterior muscle spindles is altered in individuals with knee OA. Thirty individuals with knee OA (17 females, 66?±?7 [mean?±?SD] years) and 30 healthy asymptomatic controls (17 females, 65?±?8 years) stood comfortably and blindfolded on a force plate. Mechanical vibration (60?Hz) was applied bilaterally over the quadriceps, triceps surae, or tibialis anterior muscles for the middle 15?s (Vibration) of a 45?s trial (preceded and followed by 15?s Baseline and Recovery periods). Two trials were recorded for each muscle site. Mean anterior-posterior displacement of centre of pressure was analysed. Although there were no differences between groups for trials with vibration applied to the quandriceps or tibialis anterior, participants with knee OA were initially perturbed more by triceps surae vibration and accommodated less to repeated exposure than controls. This indicates that people with knee OA have less potential to detect or compensate for disturbed input to triceps surae, possibly due to an inability to compensate using muscles spindles in the quadriceps muscle. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:989-996, 2014. PMID:24797419

Shanahan, Camille J; Wrigley, Tim V; Farrell, Michael J; Bennell, Kim L; Hodges, Paul W

2014-08-01

375

Development of a numerical model for bridge–vehicle interaction and human response to traffic-induced vibration  

Microsoft Academic Search

The perceptible vibration of composite steel girder bridges under live loads is an important design consideration in today’s bridges, which have longer spans and lighter decks than older bridges, and have with limited damping. Although, in accordance with the bridge design codes, the strength design and the deflection control of these bridges are covered fairly well, vehicle movement on the

Hassan Moghimi; Hamid R. Ronagh

2008-01-01

376

PREFACE: Vibrations at surfaces Vibrations at surfaces  

NASA Astrophysics Data System (ADS)

This special issue is dedicated to the phenomenon of vibrations at surfaces—a topic that was indispensible a couple of decades ago, since it was one of the few phenomena capable of revealing the nature of binding at solid surfaces. For clean surfaces, the frequencies of modes with characteristic displacement patterns revealed how surface geometry, as well as the nature of binding between atoms in the surface layers, could be different from that in the bulk solid. Dispersion of the surface phonons provided further measures of interatomic interactions. For chemisorbed molecules on surfaces, frequencies and dispersion of the vibrational modes were also critical for determining adsorption sites. In other words, vibrations at surfaces served as a reliable means of extracting information about surface structure, chemisorption and overlayer formation. Experimental techniques, such as electron energy loss spectroscopy and helium-atom-surface scattering, coupled with infra-red spectroscopy, were continually refined and their resolutions enhanced to capture subtleties in the dynamics of atoms and molecules at surfaces. Theoretical methods, whether based on empirical and semi-empirical interatomic potential or on ab initio electronic structure calculations, helped decipher experimental observations and provide deeper insights into the nature of the bond between atoms and molecules in regions of reduced symmetry, as encountered on solid surfaces. Vibrations at surfaces were thus an integral part of the set of phenomena that characterized surface science. Dedicated workshops and conferences were held to explore the variety of interesting and puzzling features revealed in experimental and theoretical investigations of surface vibrational modes and their dispersion. One such conference, Vibrations at Surfaces, first organized by Harald Ibach in Juelich in 1980, continues to this day. The 13th International Conference on Vibrations at Surfaces was held at the University of Central Florida, Orlando, in March 2010. Several speakers at this meeting were invited to contribute to the special section in this issue. As is clear from the articles in this special section, the phenomenon of vibrations at surfaces continues to be a dynamic field of investigation. In fact, there is a resurgence of effort because the insights provided by surface dynamics are still fundamental to the development of an understanding of the microscopic factors that control surface structure formation, diffusion, reaction and structural stability. Examination of dynamics at surfaces thus complements and supplements the wealth of information that is obtained from real-space techniques such as scanning tunneling microscopy. Vibrational dynamics is, of course, not limited to surfaces. Surfaces are important since they provide immediate deviation from the bulk. They display how lack of symmetry can lead to new structures, new local atomic environments and new types of dynamical modes. Nanoparticles, large molecules and nanostructures of all types, in all kinds of local environments, provide further examples of regions of reduced symmetry and coordination, and hence display characteristic vibrational modes. Given the tremendous advance in the synthesis of a variety of nanostructures whose functionalization would pave the way for nanotechnology, there is even greater need to engage in experimental and theoretical techniques that help extract their vibrational dynamics. Such knowledge would enable a more complete understanding and characterization of these nanoscale systems than would otherwise be the case. The papers presented here provide excellent examples of the kind of information that is revealed by vibrations at surfaces. Vibrations at surface contents Poisoning and non-poisoning oxygen on Cu(410)L Vattuone, V Venugopal, T Kravchuk, M Smerieri, L Savio and M Rocca Modifying protein adsorption by layers of glutathione pre-adsorbed on Au(111)Anne Vallée, Vincent Humblot, Christophe Méthivier, Paul Dumas and Claire-Marie Pradier Relating temperature dependence of atom

Rahman, Talat S.

2011-12-01

377

Vibration and sound radiation of viscoelastically supported Mindlin plates  

NASA Astrophysics Data System (ADS)

Models based on the Mindlin plate theory were developed and used to investigate the vibro-acoustic characteristics of sandwich panels with viscoelastic supports. The Rayleigh-Ritz method was used to predict the vibration response of the plate subjected to distributed random forces with imposed spectral characteristics. Sound radiation efficiency was calculated for each mode, which allowed the radiated sound power spectra to be determined. Timoshenko beam functions were used as the trial functions. This approach ensured a fast convergence rate, which is advantageous for vibration and sound radiation analysis of high-order modes. The optimal support properties for minimum vibration amplitude were determined. Vibration energy dissipation at the edges was found, as expected, to regulate the vibration amplitude. The effects of the plate mechanical properties on the vibration amplitude and sound radiation were investigated. Sound was found to be predominantly radiated by bending deformation of the face materials at low frequencies, and shear deformations of the honeycomb core at higher frequencies.

Park, Junhong; Mongeau, Luc

2008-12-01

378

TECHNICAL NOTE: A piezostack-based active mount for broadband frequency vibration control: experimental validation  

NASA Astrophysics Data System (ADS)

This paper presents an experimental investigation on vibration control using an active mount activated by piezostack actuators. After describing the schematic configuration and operational principle of the proposed active mount, dynamic characteristics of the rubber element and the piezostack are experimentally identified. An active mount is then manufactured using a rubber element and two piezostack elements. Prior to validating vibration control of the proposed active mount, fundamental characteristics such as resonant frequency, deflection at rated load, strength, shock and fatigue characteristics are experimentally investigated. A two-degree-of-freedom control system in which an active mount is installed with a supported mass of 100 kg is established for evaluating vibration control performance. In order to actively attenuate the vibration transmitted from the base excitation (50-1000 Hz), a negative velocity feedback controller is experimentally realized. Control responses such as mass acceleration are evaluated in both frequency and time domains.

Choi, Seung-Bok; Sohn, Jung Woo; Choi, Sang-Min; Nguyen, Vien Quoc; Moon, Seok-Jun

2009-09-01

379

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

380

State-space spectral estimation of characteristic electromagnetic responses in wideband data  

Microsoft Academic Search

This letter utilizes a robust spectral estimation method, based on state-space control theory, to coherently process wideband frequency domain field data of any object and extract specific modal (or characteristic) responses associated with wave propagation along the object. The estimation problem is formulated in terms of well-known range processing used in radar imaging. Thus, the data is modeled in terms

Krishna Naishadham; Jean E. Piou

2005-01-01

381

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

382

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

383

[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

384

Intracellular characteristics and responses of taste bud and lingual cells of the mudpuppy  

PubMed Central

Intracellular recordings of membrane potentials of mudpuppy lingual cells were made with micropipette electrodes. Three types of cells were distinguished by their responses to chemical stimulation. Surface epithelial (SE) cells outside of taste buds responded with large membrane potential and resistance changes to a variety of stimuli representing the four taste qualities. Salts and acids evoked particularly large potential changes, and MgCl2, acids, and quinine greatly increased the membrane resistance. One type of taste bud cell (TB-1) was characterized by large depolarizations to K salts, and the other type of taste bud cell (TB-2) characteristically hyperpolarized to MgCl2, acid, and sugar solutions. Membrane resistance changes accompanying TB-1 and TB-2 cell responses were relatively small compared to those of SE cells. Electrotonic coupling was observed between pairs of SE and TB-2 cells but not for pairs of TB-1 cells nor cells of different types. After recording cell responses, dye-marking allowed verification of results in situ and histologically. From the identification of cells in section, it is hypothesized the TB-1 and TB- 2 cells correspond to light and dark cells, respectively. Responses of TB-1 cells imply a taste receptive function; wheras TB 2-cell responses suggest secretory, supportive, and (or) receptive functions. Factors affecting cellular characteristics, non-taste bud cell responsiveness, response mechanisms, and function of electrotonic coupling are discussed in relation to taste reception.

1978-01-01

385

Vibrations at surfaces  

Microsoft Academic Search

This special issue is dedicated to the phenomenon of vibrations at surfaces—a topic that was indispensible a couple of decades ago, since it was one of the few phenomena capable of revealing the nature of binding at solid surfaces. For clean surfaces, the frequencies of modes with characteristic displacement patterns revealed how surface geometry, as well as the nature of

Talat S Rahman

2011-01-01

386

Time-domain parameter identification of aeroelastic loads by forced-vibration method for response of flexible structures subject to transient wind  

NASA Astrophysics Data System (ADS)

Slender structures representing civil, mechanical and aerospace systems such as long-span bridges, high-rise buildings, stay cables, power-line cables, high light mast poles, crane-booms and aircraft wings could experience vortex-induced and buffeting excitations below their design wind speeds and divergent self-excited oscillations (flutter) beyond a critical wind speed because these are flexible. Traditional linear aerodynamic theories that are routinely applied for their response prediction are not valid in the galloping, or near-flutter regime, where large-amplitude vibrations could occur and during non-stationary and transient wind excitations that occur, for example, during hurricanes, thunderstorms and gust fronts. The linear aerodynamic load formulation for lift, drag and moment are expressed in terms of aerodynamic functions in frequency domain that are valid for straight-line winds which are stationary or weakly-stationary. Application of the frequency domain formulation is restricted from use in the nonlinear and transient domain because these are valid for linear models and stationary wind. The time-domain aerodynamic force formulations are suitable for finite element modeling, feedback-dependent structural control mechanism, fatigue-life prediction, and above all modeling of transient structural behavior during non-stationary wind phenomena. This has motivated the developing of time-domain models of aerodynamic loads that are in parallel to the existing frequency-dependent models. Parameters defining these time-domain models can be now extracted from wind tunnel tests, for example, the Rational Function Coefficients defining the self-excited wind loads can be extracted using section model tests using the free vibration technique. However, the free vibration method has some limitations because it is difficult to apply at high wind speeds, in turbulent wind environment, or on unstable cross sections with negative aerodynamic damping. In the current research, new algorithms were developed based on forced vibration technique for direct extraction of the Rational Functions. The first of the two algorithms developed uses the two angular phase lag values between the measured vertical or torsional displacement and the measured aerodynamic lift and moment produced on the section model subject to forced vibration to identify the Rational Functions. This algorithm uses two separate one-degree-of-freedom tests (vertical or torsional) to identify all the four Rational Functions or corresponding Rational Function Coefficients for a two degrees-of-freedom (DOF) vertical-torsional vibration model. It was applied to a streamlined section model and the results compared well with those obtained from earlier free vibration experiment. The second algorithm that was developed is based on direct least squares method. It uses all the data points of displacements and aerodynamic lift and moment instead of phase lag values for more accurate estimates. This algorithm can be used for one-, two- and three-degree-of-freedom motions. A two-degree-of-freedom forced vibration system was developed and the algorithm was shown to work well for both streamlined and bluff section models. The uniqueness of the second algorithms lies in the fact that it requires testing the model at only two wind speeds for extraction of all four Rational Functions. The Rational Function Coefficients that were extracted for a streamlined section model using the two-DOF Least Squares algorithm were validated in a separate wind tunnel by testing a larger scaled model subject to straight-line, gusty and boundary-layer wind.

Cao, Bochao

387

Health Systems' Responsiveness and Its Characteristics: A Cross-Country Comparative Analysis  

PubMed Central

Objectives Responsiveness has been identified as one of the intrinsic goals of health care systems. Little is known, however, about its determinants. Our objective is to investigate the potential country-level drivers of health system responsiveness. Data Source Data on responsiveness are taken from the World Health Survey. Information on country-level characteristics is obtained from a variety of sources including the United Nations Development Program (UNDP). Study Design A two-step procedure. First, using survey data we derive a country-level measure of system responsiveness purged of differences in individual reporting behavior. Secondly, we run cross-sectional country-level regressions of responsiveness on potential drivers. Principal Findings Health care expenditures per capita are positively associated with responsiveness, after controlling for the influence of potential confounding factors. Aspects of responsiveness are also associated with public sector spending (negatively) and educational development (positively). Conclusions From a policy perspective, improvements in responsiveness may require higher spending levels. The expansion of nonpublic sector provision, perhaps in the form of increased patient choice, may also serve to improve responsiveness. However, these inferences are tentative and require further study.

Robone, Silvana; Rice, Nigel; Smith, Peter C

2011-01-01

388

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

389

Detection of structural damage by ambient vibration measurement using laser Doppler vibrometer  

Microsoft Academic Search

In order to rationalize structural maintenance, this paper focuses on vibration characteristics as indices to detect damage, and addresses advanced vibration measurement system and damage detection method based on changes in vibration characteristics. First of all, vibration measurement system using Laser Doppler Vibrometer, which can scan the objective structural surface, is developed and an identification method from laser ambient vibration

Yozo Fujino; Kiyoyuki Kaito; Masato Abe

2001-01-01

390

Frequency Response Characteristics of a Birefringent Lens with Off-Axis Aberrations  

NASA Astrophysics Data System (ADS)

We report the frequency response characteristics of an optical system consisting of a lens made of a uniaxial birefringent crystal sandwiched between two linear polarizers; the lens has prespecified off-axis aberrations such as primary astigmatism and primary coma. An analytical expression is obtained for the optical transfer function of the proposed system by use of the autocorrelation of the pupil function over the lens aperture. Some specific cases are computed and illustrated graphically. It has been shown that the proposed system has imaging characteristics distinctly different from those of an ordinary glass lens, and these may be advantageous for better balancing of aberrations in conventional imaging systems.

Sanyal, Sucharita; Kawata, Yoshimasa; Ghosh, Ajay; Mandal, Surajit

2004-07-01

391

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

392

Vibration isolation  

NASA Technical Reports Server (NTRS)

Viewgraphs on vibration isolation are presented. Techniques to control and isolate centrifuge disturbances were identified. Topics covered include: disturbance sources in the microgravity environment; microgravity assessment criteria; life sciences centrifuge; flight support equipment for launch; active vibration isolation system; active balancing system; and fuzzy logic control.

Bastin, Paul

1990-01-01

393

Force Limited Vibration Testing  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the concept and applications of Force Limited Vibration Testing. The goal of vibration testing of aerospace hardware is to identify problems that would result in flight failures. The commonly used aerospace vibration tests uses artificially high shaker forces and responses at the resonance frequencies of the test item. It has become common to limit the acceleration responses in the test to those predicted for the flight. This requires an analysis of the acceleration response, and requires placing accelerometers on the test item. With the advent of piezoelectric gages it has become possible to improve vibration testing. The basic equations have are reviewed. Force limits are analogous and complementary to the acceleration specifications used in conventional vibration testing. Just as the acceleration specification is the frequency spectrum envelope of the in-flight acceleration at the interface between the test item and flight mounting structure, the force limit is the envelope of the in-flight force at the interface . In force limited vibration tests, both the acceleration and force specifications are needed, and the force specification is generally based on and proportional to the acceleration specification. Therefore, force limiting does not compensate for errors in the development of the acceleration specification, e.g., too much conservatism or the lack thereof. These errors will carry over into the force specification. Since in-flight vibratory force data are scarce, force limits are often derived from coupled system analyses and impedance information obtained from measurements or finite element models (FEM). Fortunately, data on the interface forces between systems and components are now available from system acoustic and vibration tests of development test models and from a few flight experiments. Semi-empirical methods of predicting force limits are currently being developed on the basis of the limited flight and system test data. A simple two degree of freedom system is shown and the governing equations for basic force limiting results for this system are reviewed. The design and results of the shuttle vibration forces (SVF) experiments are reviewed. The Advanced Composition Explorer (ACE) also was used to validate force limiting. Test instrumentation and supporting equipment are reviewed including piezo-electric force transducers, signal processing and conditioning systems, test fixtures, and vibration controller systems. Several examples of force limited vibration testing are presented with some results.

Scharton, Terry; Chang, Kurng Y.

2005-01-01

394

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

395

Damping phenomena in a wire rope vibration isolation system  

NASA Astrophysics Data System (ADS)

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.

1992-08-01

396

Specified Step Settling Control Based Initial Value Compensation for Slow Settling Response Considering Rolling Friction Characteristic  

NASA Astrophysics Data System (ADS)

This paper presents a novel initial value compensation (IVC) method based on rolling friction characteristics for the precise positioning of linear motor-driven table systems. Rolling friction in mechanism behaves as a nonlinear elastic element in the micro displacement region, and deteriorates the positioning performance with a slow settling response. In order to improve the positioning performance, the overshoot response, which results in the slow settling response, should be suppressed during the positioning. In this study, therefore, IVC based on the specified step settling control framework is employed to achieve the required settling performance without the slow settling response. The effectiveness of the proposed IVC has been verified by experiments performed using a prototype of an industrial positioning device.

Maeda, Yoshihiro; Iwasaki, Makoto

397

[Alexithymia in vibration disease patients].  

PubMed

Neuro-psychologic studies demonstrated that alexithymia manifestations are more frequent in vibration disease patients than in the reference group. With the disease progress alexithymia increases. Alexithymic traits are combined with neurologic disorders, increased anxiety, inclination to depressive response to stress situation. Using nootropics increases efficiency of rehabilitation in vibration disease patients having alexithymia symptoms. PMID:19877439

Kir'iakov, V A; Sukhova, A V

2009-01-01

398

Seismic vibration analysis of fluid-structure interaction in LMFBR piping systems  

SciTech Connect

This paper is a basic study on the vibrational characteristics of an LMFBR piping system containing liquid sodium under one-dimensional seismic excitation. Using Z-shaped piping, the authors formulate coupled equations for the pipe's bending vibration and pressure wave, and transform them into two-degree-of-freedom vibration equations for the first modes of the piping vibration and pressure wave. A numerical study using the vibration model shows that: 1) the coupling effect appears between piping acceleration and liquid pressure for a piping configuration having a natural frequency ratio ..nu.. = about 0.5 to 2.0; 2) the magnitude of seismically induced pressure reaches 0.7 kPa to 1 kPa per gal; and 3) the dead-mass model of liquid gives a nonconservative response depending on the pipe's geometrical configuration, compared to that from the pressure-wave-piping-interaction model.

Hara, F.

1988-05-01

399

Two-dimensional vibrational spectroscopy. II. Ab initio calculation of the coherent 2D infrared response function of CHCl3 and comparison with the 2D Raman response function  

NASA Astrophysics Data System (ADS)

The two-dimensional vibrational spectroscopy involving two infrared (IR) pulses and a single optical pulse, which was theoretically proposed recently [J. Chem. Phys. 109, 10559 (1998)], is studied by using the ab initio calculation method for CHCl3. By obtaining the first- and second-order derivatives of the molecular dipole moment as well as the polarizability, the coherent 2D IR response function and its spectrum are calculated with an assumption that the vibrational dynamics can be described by the Brownian oscillator model. The origin of each peak in the entire coherent 2D IR spectrum is discussed in detail, and is directly compared with the coherent 2D Raman scattering spectrum of CHCl3. This comparison demonstrates the complementary nature between the coherent 2D IR and Raman spectroscopies. A brief discussion on the coupling patterns is also presented.

Park, Kisam; Cho, Minhaeng; Hahn, Sangjoon; Kim, Dongho

1999-09-01

400

Striatal dopamine D2/D3 receptor availability correlates with individual response characteristics to pain.  

PubMed

We studied in healthy humans the contribution of cerebral dopamine D2/D3 receptors to individual differences in response characteristics to painful stimulation. Positron emission tomography was used to measure the dopamine D2/D3 binding potential (D2/D3 BP) with [(11)C]raclopride in the striatum (n = 8) and with [(11)C]FLB 457 in the extrastriatal regions (n = 11). Sensitivity to cutaneous heat pain was assessed by a traditional threshold method and by an analysis based on the signal detection theory which allows the separation of an individual subject's discriminative capacity from the response criterion, i.e. the area under the receiver operating characteristic curve provides a measure of the sensory discriminability (sensory factor) and the response criterion gives an estimate of the subject's response bias or attitude (nonsensory factor). The pain threshold and response criterion were inversely correlated with the D2/D3 BP in the right putamen, whereas the discriminative capacity was not significantly correlated with the D2/D3 BP in any brain region. The correlation of the D2/D3 BP in the putamen with the pain threshold and the subject's response criterion may rather be explained by a dopaminergic effect on nonsensory factors determining the subject's attitude towards pain than by a dopaminergic effect on the subject's discriminative capacity. Alternatively, striatal dopamine D2/D3 receptors could control a modulatory pathway producing a parallel shift in the stimulus-response function for sensory signals, mimicking a change in the subject's response criterion. PMID:15355325

Pertovaara, Antti; Martikainen, Ilkka K; Hagelberg, Nora; Mansikka, Heikki; Någren, Kjell; Hietala, Jarmo; Scheinin, Harry

2004-09-01

401

[Characteristics of postural corrective responses before and after long-term spaceflight].  

PubMed

Balance function is dramatically deteriorated after exposure to microgravity. The purpose of the present study was to investigate the role and the contribution of different gravity sensory systems to the development of balance impairment after long-term spaceflights. Postural perturbations (pushes to the chest) of the threshold, medium, and sub-maximal intensities were produced in eight cosmonauts before, and on the day 3, 7, and 11 following spaceflight. Postural corrective responses were analyzed by anterior-posterior body sway fluctuation and electromyographic activity of leg muscles. The characteristics of the postural corrective responses changed significantly on the day 3 following spaceflight: the amplitude of posterior sway caused by perturbation of threshold intensity was increased reaching 135% ofpreflight value; the corrective responses lasted more than 6 s in 50% of all trials, while it did not last more than 4 s in 96% before spaceflight. The EMG responses were characterized by increased contribution of medium- and long-latency reactions. On the day 11 following spaceflight, most of the characteristics of postural corrective responses were close to preflight values. We assumed that the balance alterations after spaceflight are caused by changes in weightlessness of functions of two main gravity sensory systems, namely, weight-bearing and vestibular one. The deficit of weight-bearing afferentation triggers a decline of the extensors' muscle tone, while changes of vestibular function cause a decline of accuracy of postural corrections. PMID:22117463

Saenko, D G; Artamonov, A A; Kozlovskaia, I B

2011-01-01

402

Response surface optimization and characteristics of rambutan ( Nephelium lappaceum L.) kernel fat by hexane extraction  

Microsoft Academic Search

Response surface methodology (RSM) was used to study the effect of moisture content (1.59–18.41 g\\/100 g), extraction time (2.3–10.7 h) and particle size (0.09–2.11 mm) on the fat yield from rambutan kernels using hexane extraction. The physical and chemical characteristics of rambutan fat were also determined. The optimum conditions obtained from response surface analysis was 4.99 g\\/100 g moisture, 1.05 mm particle size and 9.2 h extraction time.

Wanrada Sirisompong; Wannee Jirapakkul; Utai Klinkesorn

2011-01-01

403

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

404

Efficient computation for dynamic responses of systems with time-varying characteristics  

Microsoft Academic Search

Based on Neumman series and epsilon-algorithm, an efficient computation for dynamic responses of systems with arbitrary time-varying\\u000a characteristics is investigated. Avoiding the calculation for the inverses of the equivalent stiffness matrices in each time\\u000a step, the computation effort of the proposed method is reduced compared with the full analysis of Newmark method. The validity\\u000a and applications of the proposed method

Liang Ma; Yudong Chen; Suhuan Chen; Guangwei Meng

2009-01-01

405

Vibration analysis and control system dynamics  

NASA Astrophysics Data System (ADS)

Systems having one degree of freedom are examined, including cases of free, undamped vibration, free, damped vibration, and forced vibration. Attention is also given to systems with more than one degree of freedom, comprising two or more degrees of freedom, the Lagrange equation, and receptances. Vibrations in systems with distributed mass and elasticity are explored, specifically for wave motion, transverse vibration, the analysis of continuous systems by Rayleigh's method, and the stability of vibrating systems. Automatic control systems are detailed, and the simple hydraulic servo, modifications to it, the electric position servo, applications of the Laplace transformation, system transfer functions, the root locus, and the control system frequency response are discussed.

Beards, C. F.

406

Individual differences in responsiveness to single and repeated amphetamine administration: behavioral characteristics and neurochemical correlates.  

PubMed

The administration of amphetamine to rats results in a relatively wide range of individual differences in responsiveness, both in the initial behavioral patterns as well as in the augmentation response to repeated administration. Therefore we examined the possibility that such differences might reflect intrinsic variation in neurochemical mechanisms regulating responsiveness to amphetamine. Animals were administered a transitional dose (1.75 mg/kg) of amphetamine with regard to the induction of locomotion and continuous stereotypy. On the basis of individual response profiles animals could be separated into two markedly different subgroups, one displaying continuous locomotion (S1), characteristic of lower amphetamine doses, and the other exhibiting a multiphasic pattern, including a prolonged focused stereotypy phase (S2), typically associated with higher amphetamine doses. Examination of regional brain monoamine and metabolite levels revealed distinguishing patterns between the subgroups only in the mesolimbic and mesocortical dopamine systems. With repeated amphetamine administration, the two prominent factors of the augmentation, the emergence of stereotypy and the enhancement of locomotion during the last half of the response, were dissociable between the subgroups. The emergence of stereotypy was confined to S1 animals, whereas only the S2 subgroup displayed the progressive increase in locomotion. Differences in the responsiveness of neurochemical systems to amphetamine rather than pharmacokinetic factors appear to underly the distinct behavioral profiles associated with the two subgroups. The results indicate that characterization of individual responses may be required to determine accurately the neurochemical mechanisms involved in the behavioral effects of amphetamine. PMID:3656119

Segal, D S; Kuczenski, R

1987-09-01

407

Teacher Characteristics Influence Responsiveness to a Course and a Consultancy Focused on Effective Teacher-Child Interactions  

ERIC Educational Resources Information Center

In the current study characteristics of the teacher and classroom that influence teacher responsiveness to the course or consultancy are explored. If classroom quality or characteristics of teachers, such as anxiety levels or efficacy in teaching prior to intervention participation are predictive of responsiveness, then future programs will be…

Hatfield, Bridget; Hamre, Bridget; LoCasale-Crouch, Jennifer; Pianta, Robert; Downer, Jason; Burchinal, Margaret; Howes, Carollee

2012-01-01

408

Ride quality criteria. [transportation system interior and passenger response to environment  

NASA Technical Reports Server (NTRS)

Ride quality refers to the interior or passenger environment of a transportation system as well as the passenger response to the environment. Ride quality factors are illustrated with the aid of a diagram presenting inputs to vehicle, the vehicle transfer function, the ride environment, the passenger response function, and the passenger ride response. The reported investigation considers the ride environment as measured on a variety of air and surface vehicles, the passenger response to the environment as determined from laboratory and field surveys, and criteria/standards for vibration, noise, and combined stimuli. Attention is given to the vertical vibration characteristics in cruise for aircraft and automobile, the aircraft vibration levels for various operating regimes, comparative noise levels during cruise, the discomfort level for a 9 Hz sinusoidal vibration, equal discomfort contours for vertical vibration, subjective response to noise in a speech situation, and noise and vibration levels for constant discomfort contours.

Stephens, D. G.

1977-01-01

409

A Method for Determination of Damping for Edgewise Blade Vibrations  

NASA Astrophysics Data System (ADS)

Violent edgewise blade vibrations have in recent years been a large problem for some stall-regulated wind turbines. Owing to the complexity of the phenomenon, it has been difficult to predict the risk of these vibrations with aeroelastic load prediction tools. One problem is the choice of parameters in the aeroelastic model, e.g. structural damping and aerodynamic aerofoil characteristics. In many cases a high degree of uncertainty in the predicted response exists and the need for experimental verification methods is obvious. In this work a new method to identify the effective damping for the edgewise blade mode shape for wind turbines has been developed. The method consists of an exciter mechanism which makes it possible to excite the edgewise blade mode shapes from the wind turbine nacelle. Furthermore, the method consists of an analysis method which enables a straightforward determination of the damping. The analysis method is based on a local blade whirl description of the edgewise blade vibrations. The method is verified on a Bonus wind turbine, and for this specific turbine the effective damping for edgewise blade vibrations has been determined. The results support the further development of aeroelastic models and show potential for fine-tuning of parameters of importance for the edgewise blade vibration problem. Furthermore, the method can be used for experimental investigation of the risk of edgewise blade vibrations for a specific turbine. Copyright

Thomsen, K.; Petersen, J. T.; Nim, E.; Øye, S.; Petersen, B.

2000-10-01

410

Vibration modal analysis using all-optical photorefractive processing  

SciTech Connect

A new experimental method for vibration modal analysis based on all- optical photorefractive processing is presented. The method utilizes an optical lock-in approach to measure phase variations in light scattered from optically rough, continuously vibrating surfaces. In this four-wave mixing technique, all-optical processing refers to mixing the object beam containing the frequency modulation due to vibration with a single frequency modulated pump beam in the photorefractive medium that processes the modulated signals. This allows for simple detection of the conjugate wavefront image at a CCD. The conjugate intensity is shown to be a function of the first-order ordinary Bessel function and linearly dependent on the vibration displacement induced phase. Furthermore, the results demonstrate the unique capabilities of the optical lock-in vibration detection technique to measure vibration signals with very narrow bandwidth (< 1 Hz) and high displacement sensitivity (sub-Angstrom). This narrow bandwidth detection can be achieved over a wide frequency range from the photorefractive response limit to the reciprocal of the photoinduced carrier recombination time. The technique is applied to determine the modal characteristics of a rigidly clamped circular disc from 10 kHz to 100 kHz.

Hale, T.; Telschow, K.

1996-12-31

411

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

412

Improved active vibration isolator  

NASA Technical Reports Server (NTRS)

Active vibration isolator simultaneously isolates a flexible structure or payload from disturbances, attenuates the response of a flexible structure to transient disturbances, and maintains the equilibrium position of the payload within predetermined limits over a wide range of steady loads and accelerators.

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

1968-01-01

413

Vibration generators  

SciTech Connect

Apparatus for generating vibrations in a medium, such as the ground, comprises a first member which contacts the medium, means , preferably electromagnetic, which includes two relatively movable members for generating vibrations in the apparatus and means operatively connecting the said two members to said first member such that the relatively amplitudes of the movements of said three members can be adjusted to match the impedances of the apparatus and the medium.

Lerwill, W.E.

1980-09-16

414

Vibration sensors  

NASA Astrophysics Data System (ADS)

Today, vibration sensors with low and medium sensitivities are in great demand. Their applications include robotics, navigation, machine vibration monitoring, isolation of precision equipment & activation of safety systems e.g. airbags in automobiles. Vibration sensors have been developed at SSPL, using silicon micromachining to sense vibrations in a system in the 30 - 200 Hz frequency band. The sensing element in the silicon vibration sensor is a seismic mass suspended by thin silicon hinges mounted on a metallized glass plate forming a parallel plate capacitor. The movement of the seismic mass along the vertical axis is monitored to sense vibrations. This is obtained by measuring the change in capacitance. The movable plate of the parallel plate capacitor is formed by a block connected to a surrounding frame by four cantilever beams located on sides or corners of the seismic mass. This element is fabricated by silicon micromachining. Several sensors in the chip sizes 1.6 cm x 1.6 cm, 1 cm x 1 cm and 0.7 cm x 0.7 cm have been fabricated. Work done on these sensors, techniques used in processing and silicon to glass bonding are presented in the paper. Performance evaluation of these sensors is also discussed.

Gupta, Amita; Singh, Ranvir; Ahmad, Amir; Kumar, Mahesh

2003-10-01

415

Granular metamaterials for vibration mitigation  

NASA Astrophysics Data System (ADS)

Acoustic metamaterials that allow low-frequency band gaps are interesting for many practical engineering applications, where vibration control and sound insulation are necessary. In most prior studies, the mechanical response of these structures has been described using linear continuum approximations. In this work, we experimentally and theoretically address the formation of low-frequency band gaps in locally resonant granular crystals, where the dynamics of the system is governed by discrete equations. We investigate the quasi-linear behavior of such structures. The analysis shows that a stopband can be introduced at about one octave lower frequency than in materials without local resonances. Broadband and multi-frequency stopband characteristics can also be achieved by strategically tailoring the non-uniform local resonance parameters.

Gantzounis, G.; Serra-Garcia, M.; Homma, K.; Mendoza, J. M.; Daraio, C.

2013-09-01

416

Resonance Characteristics of Micro Cantilever in Liquid  

Microsoft Academic Search

The resonance characteristics of a micro cantilever are experimentally and theoretically studied. The micro cantilever is vibrated by thermal excitation using laser exposure and the frequency responses of the micro cantilever in air, acetone and water are experimentally evaluated based on an optical measurement technique. It is demonstrated that the resonance frequencies in water decrease to about one-tenth of the

Yoshihiko Hirai; Ryosuke Mori; Hisao Kikuta; Nobuhiro Kato; Koji Inoue; Yoshio Tanaka

1998-01-01

417

Vibrations at surfaces.  

PubMed

This special issue is dedicated to the phenomenon of vibrations at surfaces-a topic that was indispensible a couple of decades ago, since it was one of the few phenomena capable of revealing the nature of binding at solid surfaces. For clean surfaces, the frequencies of modes with characteristic displacement patterns revealed how surface geometry, as well as the nature of binding between atoms in the surface layers, could be different from that in the bulk solid. Dispersion of the surface phonons provided further measures of interatomic interactions. For chemisorbed molecules on surfaces, frequencies and dispersion of the vibrational modes were also critical for determining adsorption sites. In other words, vibrations at surfaces served as a reliable means of extracting information about surface structure, chemisorption and overlayer formation. Experimental techniques, such as electron energy loss spectroscopy and helium-atom-surface scattering, coupled with infra-red spectroscopy, were continually refined and their resolutions enhanced to capture subtleties in the dynamics of atoms and molecules at surfaces. Theoretical methods, whether based on empirical and semi-empirical interatomic potential or on ab initio electronic structure calculations, helped decipher experimental observations and provide deeper insights into the nature of the bond between atoms and molecules in regions of reduced symmetry, as encountered on solid surfaces. Vibrations at surfaces were thus an integral part of the set of phenomena that characterized surface science. Dedicated workshops and conferences were held to explore the variety of interesting and puzzling features revealed in experimental and theoretical investigations of surface vibrational modes and their dispersion. One such conference, Vibrations at Surfaces, first organized by Harald Ibach in Juelich in 1980, continues to this day. The 13th International Conference on Vibrations at Surfaces was held at the University of Central Florida, Orlando, in March 2010. Several speakers at this meeting were invited to contribute to the special section in this issue. As is clear from the articles in this special section, the phenomenon of vibrations at surfaces continues to be a dynamic field of investigation. In fact, there is a resurgence of effort because the insights provided by surface dynamics are still fundamental to the development of an understanding of the microscopic factors that control surface structure formation, diffusion, reaction and structural stability. Examination of dynamics at surfaces thus complements and supplements the wealth of information that is obtained from real-space techniques such as scanning tunneling microscopy. Vibrational dynamics is, of course, not limited to surfaces. Surfaces are important since they provide immediate deviation from the bulk. They display how lack of symmetry can lead to new structures, new local atomic environments and new types of dynamical modes. Nanoparticles, large molecules and nanostructures of all types, in all kinds of local environments, provide further examples of regions of reduced symmetry and coordination, and hence display characteristic vibrational modes. Given the tremendous advance in the synthesis of a variety of nanostructures whose functionalization would pave the way for nanotechnology, there is even greater need to engage in experimental and theoretical techniques that help extract their vibrational dynamics. Such knowledge would enable a more complete understanding and characterization of these nanoscale systems than would otherwise be the case. The papers presented here provide excellent examples of the kind of information that is revealed by vibrations at surfaces. Vibrations at surface contents Poisoning and non-poisoning oxygen on Cu(410)L Vattuone, V Venugopal, T Kravchuk, M Smerieri, L Savio and M Rocca Modifying protein adsorption by layers of glutathione pre-adsorbed on Au(111)Anne Vallée, Vincent Humblot, Christophe Méthivier, Paul Dumas and Claire-Marie Pradier Relating temperature dependence of atom sc

Rahman, Talat S

2011-11-15

418

Active Vibration Isolation and Active Vehicle Suspension.  

National Technical Information Service (NTIS)

The feasibility of using 'active' elements in suspension systems for high speed ground vehicles to improve vibration isolation characteristics is considered. The characteristics of vehicle excitations (to the suspensions and to the vehicle body) are discu...

I. L. Paul E. K. Bender

1966-01-01

419

Vibrational energy prediction of the response of the vulcain rocket engine using a mixed FET/SEA analysis  

NASA Astrophysics Data System (ADS)

The VULCAIN engine of the central core of Ariane 5, the Europe's launch vehicle of the next generation, is submitted to a high external acoustic pressure field, produced by the two solid propellant boosters during the lift-off phase. To investigate the distribution of the resulting vibrational energy throughout the different components, a predictive Statistical Energy Analysis (SEA) model was carried out, due to the high frequency signature of the lift-off noise. The first phase of the work was an experimental analysis of the VULCAIN's dynamical behavior under external sound field excitation, using energy techniques (reverse SEA). The main conclusion was an effective weak coupling between components which was encouraging for going on through the next phase the development of the theoretical SEA model.

Borello, G.

420

Ultrasonic Rotary Motors Using Complex Transverse and Torsional Vibration Rods and Multiple Longitudinal Vibration Transducers  

NASA Astrophysics Data System (ADS)

The vibration and load characteristics of ultrasonic motors having (a) a torsional vibration cylinder with three bolt-clamped Langevin piezoelectric ceramic (PZT) longitudinal vibration transducers (BLTs) installed in the tangential direction and (b) a longitudinal vibration disk with three BLT transducers installed around a circular disk were studied. The center rod vibrates longitudinally and affects the load characteristics of the ultrasonic motor. Vibration distributions along a center rod were measured using a laser Doppler vibrometer. Revolution, electric input power, mechanical output power and efficiency were measured under various rotating torques. Maximum torque, revolution and efficiency of the ultrasonic motor with (a) a torsional vibration cylinder (a) were 0.75 Nm, 205 rpm and 1.68%, respectively, and (b) 0.32 Nm, 84 rpm and 1.68%, respectively, with a circular longitudinal vibration<