Journal articles on the topic 'Amplitude'
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Paunzen, Ernst, Klaus Bernhard, Stefan Hümmerich, Franz-Josef Hambsch, Christopher Lloyd, and Sebastián Otero. "High-amplitude γ Doradus variables." Monthly Notices of the Royal Astronomical Society 499, no. 3 (September 23, 2020): 3976–91. http://dx.doi.org/10.1093/mnras/staa2905.
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ABSTRACT According to most literature sources, the amplitude of the pulsational variability observed in γ Doradus stars does not exceed 0.1 mag in Johnson V. We have analysed fifteen high-amplitude γ Doradus stars with photometric peak-to-peak amplitudes well beyond this limit, with the aim of unraveling the mechanisms behind the observed high amplitudes and investigating whether these objects are in any way physically distinct from their low-amplitude counterparts. We have calculated astrophysical parameters and investigated the location of the high-amplitude γ Doradus stars and a control sample of fifteen low-amplitude objects in the log Teff versus log L/L⊙ diagram. Employing survey data and our own observations, we analysed the photometric variability of our target stars using discrete Fourier transform. Correlations between the observed primary frequencies, amplitudes and other parameters like effective temperature and luminosity were investigated. The unusually high amplitudes of the high-amplitude γ Doradus stars can be explained by the superposition of several base frequencies in interaction with their combination and overtone frequencies. Although the maximum amplitude of the primary frequencies does not exceed an amplitude of 0.1 mag, total light variability amplitudes of over 0.3 mag (V) can be attained in this way. Low- and high-amplitude γ Doradus stars do not appear to be physically distinct in any other respect than their total variability amplitudes but merely represent two ends of the same, uniform group of variables.
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Gerasyuta, S. M., and V. I. Kochkin. "Hadronic Molecular Contribution to Cryptoexotic Meson Amplitude." International Journal of Modern Physics E 12, no. 04 (August 2003): 519–31. http://dx.doi.org/10.1142/s0218301303001429.
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The solutions of four-quark equations using the method of extracting leading singularities of the amplitudes are obtained. The calculations of cryptoexotic meson amplitudes provide the estimates of four-quark amplitude, glueball amplitude and hadronic molecule amplitudes. We find that the main contributions to the cryptoexotic meson amplitude are given by the four-quark state and the glueball.
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Spijkers, Will, and Herbert Heuer. "Structural Constraints on the Performance of Symmetrical Bimanual Movements with Different Amplitudes." Quarterly Journal of Experimental Psychology Section A 48, no. 3 (August 1995): 716–40. http://dx.doi.org/10.1080/14640749508401412.
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In bimanual movements the amplitude of each hand's movement often depends on the concurrent amplitude of the other hand's movement such that both amplitudes become similar (amplitude coupling). We tested the hypothesis that the strength of amplitude coupling depends on the tempo of performance of a movement sequence, a hypothesis based on a model of bimanual coordination that holds that cross-talk occurs at the execution level as well as at the programming level. Subjects performed bimanual periodic arm movements on two digitizers. In nine conditions constant small, constant large, and alternating small and large amplitudes of each arm were orthogonally combined. Overall tempo was varied by instructing subjects to increase the tempo progressively by 10%. Clear tempo-dependent modulations of the amplitude were observed in movements with instructed constant amplitude when the other hand performed alternating amplitudes. The effect of the size of constant-amplitude movements on the mean amplitude of the other hand indicated cross-talk at the execution level. Cross-talk at the programming level was revealed by the dependence of the current amplitude on the change in the amplitude of the other hand in the preceding cycle. Finally, asymmetric cross-manual effects were observed.
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Uhríčik, Milan, Zuzana Dresslerová, Peter Palček, Mária Chalupová, Zuzanka Trojanová, and Patrícia Hanusová. "Amplitude Dependent Internal Friction in Strained Magnesium Alloys of AZ Series." Crystals 10, no. 7 (July 13, 2020): 608. http://dx.doi.org/10.3390/cryst10070608.
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Amplitude dependent internal friction (ADIF) was measured in three AZ magnesium alloys. Two types of experiments were performed: ADIF was measured step by step with the increasing strain amplitude and ADIF was measured after predeformation of samples in torsion. All experiments were done at room temperature. The quality factor was used as a measure of internal friction (IF). The quality factor decreased in the region of smaller amplitudes, and approaching some critical amplitude, εcr, rapidly increased. This critical amplitude increased with increasing maximum strain amplitude and predeformation of samples up to ~6%. Such behavior can be explained by considering mobile solute atoms, which may migrate along the dislocation line in the region of smaller amplitudes and perpendicular to the dislocation line in the region of higher amplitudes. A competition between dragging and depinning of solute atoms with dislocation lines may very well explain the measured dependencies.
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Sivaramakrishnan, Allic. "Color-kinematic duality in ABJM theory without amplitude relations." International Journal of Modern Physics A 32, no. 02n03 (January 25, 2017): 1750002. http://dx.doi.org/10.1142/s0217751x17500026.
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We explicitly show that the Bern–Carrasco–Johansson color-kinematic duality holds at tree level through at least eight points in Aharony–Bergman–Jafferis–Maldacena theory with gauge group [Formula: see text]. At six points we give the explicit form of numerators in terms of amplitudes, displaying the generalized gauge freedom that leads to amplitude relations. However, at eight points no amplitude relations follow from the duality, so the diagram numerators are fixed unique functions of partial amplitudes. We provide the explicit amplitude-numerator decomposition and the numerator relations for eight-point amplitudes.
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Zhao, Mei Yun, Zheng Lin Liu, Xin Ze Zhao, and Rui Feng Wang. "Simulation Study on Amplitude of the Overhead Line Based on Simulink." Applied Mechanics and Materials 316-317 (April 2013): 161–66. http://dx.doi.org/10.4028/www.scientific.net/amm.316-317.161.
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Aeolian vibration often occurs in the high-voltage transmission overhead lines, and the amplitude of conductors has close relationship with conductors fretting wear. It is very difficult to measure actual amplitude of working conductor, so obtaining the amplitude of the conductor by the means of simulation is of practical significant to research quantitatively the relationship of the amplitude and the fretting wear. In this paper an imitation test-bed was built. The maximum amplitudes in the different location of a conductor in a test condition were obtained by Simulink software simulating, and the results were compared with the maximum amplitudes obtained by experimental test. The result of this comparison showed that between of them were of good similarity, and the locations of vibration nodes and maximum amplitudes were basically same. It was proved to be feasible that the aeolian vibration amplitude of the overhead conductor in kinds of conditions could be obtained by Simulink software simulating.
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Tavel, Adam. "Amplitude." Pleiades: Literature in Context 38, no. 2 (2018): 13–14. http://dx.doi.org/10.1353/plc.2018.0106.
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Rolain, Y., R. Pintelon, and J. Schoukens. "Amplitude-only versus amplitude-phase estimation." IEEE Transactions on Instrumentation and Measurement 39, no. 6 (1990): 818–23. http://dx.doi.org/10.1109/19.65776.
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Ahmadiniaz, Naser, Olindo Corradini, José Manuel Dávila, and Christian Schubert. "Gravitational Compton Scattering from the Worldline Formalism." International Journal of Modern Physics: Conference Series 43 (January 2016): 1660201. http://dx.doi.org/10.1142/s2010194516602015.
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We report on an ongoing study of photon amplitudes, graviton amplitudes and mixed photon-graviton amplitudes at tree-level using the worldline formalism. We explicitly recalculate the amplitude with one photon and one graviton coupled to a scalar propagator, relevant for graviton photoproduction. We comment on the factorization properties of this amplitude, and outline a generalization to similar processes involving more gravitons.
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Vivas, Flor A., and Reynam C. Pestana. "True-amplitude one-way wave equation migration in the mixed domain." GEOPHYSICS 75, no. 5 (September 2010): S199—S209. http://dx.doi.org/10.1190/1.3478574.
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One-way wave equation migration is a powerful imaging tool for locating accurately reflectors in complex geologic structures; however, the classical formulation of one-way wave equations does not provide accurate amplitudes for the reflectors. When dynamic information is required after migration, such as studies for amplitude variation with angle or when the correct amplitudes of the reflectors in the zero-offset images are needed, some modifications to the one-way wave equations are required. The new equations, which are called “true-amplitude one-way wave equations,” provide amplitudes that are equivalent to those provided by the leading order of the ray-theoretical approximation through the modification of the transverse Laplacian operator with dependence of lateral velocity variations, the introduction of a new term associated with the amplitudes, and the modification of the source representation. In a smoothly varying vertical medium,the extrapolation of the wavefields with the true-amplitude one-way wave equations simplifies to the product of two separable and commutative factors: one associated with the phase and equal to the phase-shift migration conventional and the other associated with the amplitude. To take advantage of this true-amplitude phase-shift migration, we developed the extension of conventional migration algorithms in a mixed domain, such as phase shift plus interpolation, split step, and Fourier finite difference. Two-dimensional numerical experiments that used a single-shot data set showed that the proposed mixed-domain true-amplitude algorithms combined with a deconvolution-type imaging condition recover the amplitudes of the reflectors better than conventional mixed-domain algorithms. Numerical experiments with multiple-shot Marmousi data showed improvement in the amplitudes of the deepest structures and preservation of higher frequency content in the migrated images.
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Arrowsmith, M. D., S. R. Taylor, and T. C. Wallace. "Using Interstation Amplitude Correction Factors to Predict Regional Phase Amplitudes." Bulletin of the Seismological Society of America 98, no. 6 (December 1, 2008): 2590–614. http://dx.doi.org/10.1785/0120070098.
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Burnett, R. C. "Seismic amplitude anomalies and AVO analyses at Mestena Grande Field, Jim Hogg Co., Texas." GEOPHYSICS 55, no. 8 (August 1990): 1015–25. http://dx.doi.org/10.1190/1.1442914.
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Mestena Grande field is located in northeast Jim Hogg Co., Texas. It produces gas and condensate, primarily from the middle member of the Middle Eocene Queen City formation. The producing zone is a deep, thin, high impedance sandstone which generates amplitude anomalies on the stacked data. AVO (amplitude versus offset) analyses were performed to investigate those anomalies and determine if they could aid in field development or exploration along the trend. Modeling the AVO response of a productive well has predicted an amplitude decrease with offset from a high impedance sandstone. However, amplitudes increase with offset on the crest of the field. At Mestena Grande field, three categories of seismic amplitudes correspond with production with only one exception. The first category exhibits strong amplitudes on the stacked data and amplitudes increase with offset. This amplitude category is seen around the best wells in the field. Second are the moderate amplitudes which do not increase with offset that surround the wells producing at moderate rates. The third category is characterized by very weak amplitudes which decrease with offset, occurring near all but one of the dry holes. The disagreement between the results of the modelling and the real data is attributed to the lack of accurate shear wave velocities and the presence of very thin beds.
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Eri, Qitai, Wenhao Ding, and Bo Kong. "Numerical Investigation of Jet Control Using Two Pulsed Jets under Different Amplitudes." Energies 15, no. 2 (January 17, 2022): 640. http://dx.doi.org/10.3390/en15020640.
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A turbulent jet with a Reynolds number of 71,000, controlled by a pair of pulsed jets operating 180° out of phase, is investigated by large-eddy simulation. The effect of the forcing amplitude on jet development and generated coherent structures is investigated through six cases: an unforced case and five cases at different amplitudes. With this forcing mode, the jet bifurcates in the far field that promotes the spread of the shear layer. It was found that the jet yields the largest bifurcation angle at medium amplitude, while the bifurcation is restrained at lower or higher amplitudes. As the amplitude increases, the streamwise vortex pair generated by the control jet is stronger and penetrates deeper into primary jet. This phenomenon reduces the inclination of vortex ring when mutual interaction between vortex ring and streamwise vortex pair occurs. Meanwhile, at higher amplitudes, the inclined vortex ring is stronger and unevenly distributed, prompting the jet bifurcation. In order to investigate the coupling effect of amplitude and frequency, different forcing frequencies were also simulated. The results demonstrated that the optimal frequency based on centerline velocity decay rate decreases with increasing amplitude; however, it eventually saturates around StD = 0.1.
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Karparvarfard, Seyyed Mohamad Hasan, Seyed Behzad Behravesh, Sugrib Kumar Shaha, and Hamid Jahed. "On the phase angle role in the shear response of ZK60 Mg alloys under multiaxial fatigue." MATEC Web of Conferences 300 (2019): 08005. http://dx.doi.org/10.1051/matecconf/201930008005.
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Proportional and non-proportional multiaxial fatigue tests are conducted on the closed-die forged ZK60 extrusion. The shear strain amplitude was kept constant at 0.5% for all the tests, while two different axial strain amplitudes of 0.4% and 0.7% were considered. At the higher strain amplitude (0.7%) significant difference was observed between the torque amplitudes of proportional and non-proportional tests, whereas the axial load amplitude responses remained the same regardless of the phase angle shifts. It is likely that as the phase angle changes from 0-90, the twin volume fraction at the peak shear strain decreases resulting in higher torque responses. On the other hand, at the lower strain amplitude, i.e. 0.4%, where twinning is not active, phase angle does not show any effect on the shear response. An energy-based fatigue model is employed that effectively explains the different damage contributions by the axial and torsional loadings at different strain amplitudes, and accurately predicts the proportional and non-proportional multiaxial fatigue lives.
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Cox, Rebecca, Sophie Haller, Zofia Martinez-Lisowska, Abhignya Kuppa, Kate Sprecher, Dana Withrow, Declan Barry, et al. "0677 Blunted daily light rhythm amplitude in adults with opioid use disorder (OUD)." SLEEP 46, Supplement_1 (May 1, 2023): A297—A298. http://dx.doi.org/10.1093/sleep/zsad077.0677.
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Abstract Introduction Accumulating evidence implicates sleep and circadian rhythm disruption in substance use disorders, including opioid use disorder (OUD). Blunted amplitude in daily rhythms of circadian-relevant variables (e.g., activity, light) may be a marker of psychopathology, as depressed adults demonstrate a smaller activity amplitude compared with healthy controls. The present study compared the light and activity amplitudes of adults with OUD with healthy controls. Methods Light and activity data were collected from adults with OUD who were recently stabilized on medication-assisted treatment (N=27; Mage=44.25±13.21). Participants wore an Actiwatch for an average of 14.5 (SD=4.14) days. Light and activity data collected from healthy adults (N=15; Mage=22.88±2.76) who wore an Actiwatch an average of 11.59 (SD=1.07) days in a separate study were included as a comparison group. Light and activity amplitudes for each day and a composite amplitude for the sampling period were calculated using non-orthogonal spectral analysis. Results Results of mixed model ANOVA with subject as a random factor and group and day as fixed factors revealed a significant main effect of group on daily light amplitude (p<.01), such that the OUD group exhibited lower daily light amplitudes compared to healthy controls, and a trend-level main effect of group on daily activity amplitude (p=.09), such that the OUD group exhibited lower daily activity amplitudes compared to healthy controls. With age included as a covariate in the model, the main effect of group on light remained significant, whereas the trend-level effect on activity became non-significant. Results of between-subjects t-tests indicated significantly lower composite light and activity amplitudes during the entire sampling period in the OUD group compared to healthy controls (p’s<.05). Conclusion These findings indicate that OUD is characterized by blunted light amplitude, which could both reflect and contribute to disruptions in circadian physiology in OUD. Light amplitude may be a novel target for behavioral OUD interventions. Future research is needed to determine whether blunted light amplitude is associated with OUD treatment outcomes and to further examine activity amplitude in OUD with larger sample sizes. Support (if any) U01 HL150596; T32 HL149646; CTSA Grant UL1 TR002535; Office of Naval Research MURI N00014-15-1-2809
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Maderich, Vladimir, Kyung Tae Jung, Kateryna Terletska, and Kyeong Ok Kim. "Head-on collision of internal waves with trapped cores." Nonlinear Processes in Geophysics 24, no. 4 (December 22, 2017): 751–62. http://dx.doi.org/10.5194/npg-24-751-2017.
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Abstract. The dynamics and energetics of a head-on collision of internal solitary waves (ISWs) with trapped cores propagating in a thin pycnocline were studied numerically within the framework of the Navier–Stokes equations for a stratified fluid. The peculiarity of this collision is that it involves trapped masses of a fluid. The interaction of ISWs differs for three classes of ISWs: (i) weakly non-linear waves without trapped cores, (ii) stable strongly non-linear waves with trapped cores, and (iii) shear unstable strongly non-linear waves. The wave phase shift of the colliding waves with equal amplitude grows as the amplitudes increase for colliding waves of classes (i) and (ii) and remains almost constant for those of class (iii). The excess of the maximum run-up amplitude, normalized by the amplitude of the waves, over the sum of the amplitudes of the equal colliding waves increases almost linearly with increasing amplitude of the interacting waves belonging to classes (i) and (ii); however, it decreases somewhat for those of class (iii). The colliding waves of class (ii) lose fluid trapped by the wave cores when amplitudes normalized by the thickness of the pycnocline are in the range of approximately between 1 and 1.75. The interacting stable waves of higher amplitude capture cores and carry trapped fluid in opposite directions with little mass loss. The collision of locally shear unstable waves of class (iii) is accompanied by the development of instability. The dependence of loss of energy on the wave amplitude is not monotonic. Initially, the energy loss due to the interaction increases as the wave amplitude increases. Then, the energy losses reach a maximum due to the loss of potential energy of the cores upon collision and then start to decrease. With further amplitude growth, collision is accompanied by the development of instability and an increase in the loss of energy. The collision process is modified for waves of different amplitudes because of the exchange of trapped fluid between colliding waves due to the conservation of momentum.
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Wrobel, Maciej J., and Bogdan F. Bogacz. "Rinne Test Results: How Badly Can We Be Mistaken?" OTO Open 5, no. 1 (January 2021): 2473974X2199699. http://dx.doi.org/10.1177/2473974x21996998.
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Objective To establish the extent to which sound amplitudes delivered by a vibrating tuning fork change around its long axis and to evaluate whether such differences in amplitude might change the results of the Rinne test. Study Design Experimental measurements. Setting Laboratory setting. Methods Setup I: a vibrating tuning fork was handheld and manually rotated around its long axis next to a sound recording device (the simulated ear) in order to record sound amplitude data at a full range of angles relative to the device; files were split into segments in which sound amplitude changed: A (from a maximum to a minimum) and B (from a minimum to a maximum). Setup II: a vibrating tuning fork was machine-rotated, and the angle of rotation, along with the sound amplitude, was automatically recorded through a single full rotation. Results The angles of 0° and 180° (which equate to the established best practice in Rinne testing) were associated with the highest sound amplitudes. All other angles decreased sound amplitude. The greatest decrease in amplitude was recorded at 51° and 130°. This difference ranged from 9.8 to 34.7 dB, depending on the initial amplitude. Conclusion The outcome of a Rinne test can be affected if attention is not paid to the precise angle at which the tuning fork is held relative to the ear. The potential of this effect will be greater when high background noise or patient hearing loss requires that the tuning fork be vigorously excited to obtain high sound amplitudes.
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Yu, Gary. "Offset‐amplitude variation and controlled‐amplitude processing." GEOPHYSICS 50, no. 12 (December 1985): 2697–708. http://dx.doi.org/10.1190/1.1441890.
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The partition of plane seismic waves at plane interfaces introduces changes in seismic amplitude which vary with angle of incidence. These amplitude variations are a function of the elastic parameters of rocks on either side of the interface. Controlled‐amplitude processing is designed to obtain the true amplitude information which is geologic in origin. The offset‐amplitude information may be successfully used to predict the fluid type in reservoir sands. Various tests were carried out on a seismic profile from the Gulf Coast. The processing comparison emphasized the effects and pitfalls of trace equalization, coherent noise, offset, and surface‐related problems. Two wells drilled at amplitude anomaly locations confirmed the prediction of hydrocarbons from offset‐amplitude analysis. Furthermore, controlled‐amplitude processing provided clues in evaluating reservoir quality, which was not evident on the conventional relative amplitude data.
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Rodheim, Katrina, Christoper Jung, and Kenneth Wright. "016 Associations between Circadian Melatonin and Temperature Amplitudes during Constant Routine." Sleep 44, Supplement_2 (May 1, 2021): A8. http://dx.doi.org/10.1093/sleep/zsab072.015.
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Abstract Introduction Circadian amplitude measures the strength or robustness of a rhythm and changes in amplitude may have implications for health. Large individual differences in melatonin amplitude are recognized. Here we aimed to determine the strength of relationships between melatonin and the core body (CBT) and distal-proximal skin temperature gradient (DPG) amplitudes during a constant routine protocol. Additionally, we determined the best fitting harmonic model for the DPG circadian rhythm. Methods 17 young healthy adults [13 males (22.3±3.9yr;mean±SD)] completed a 28-hr constant routine protocol after maintaining 8h habitual sleep schedules for one week at home. Endogenous circadian amplitudes of melatonin and CBT were fit with standard three- and dual-harmonic linear regression models, respectively. The DPG amplitude was analyzed with both dual and three-harmonic regression models to determine which model produced the best fit. Results The DPG was best fit by a three-harmonic regression model with significantly lower standard deviation and higher signal-to-noise ratio compared to the 2-harmonic model (both p<0.05) as well as by visualization of the fitted curves. Melatonin, CBT and DPG amplitudes were not found to be associated with each other during constant routine (all r<0.37; all p>0.10). Conclusion While it is common for melatonin and body temperature circadian phase estimates to be used interchangeably, non-significant findings for associations between circadian amplitudes of melatonin, CBT and DPG indicate that these markers may not provide similar information about circadian amplitude. Further, research is needed to explore possible associations between individual differences in melatonin, CBT and DPG amplitudes with other physiological and behavioral outcomes to determine which measure(s) of circadian amplitude may be functionally relevant. Support (if any) NIH R01 HL081761
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Waldvogel, Daniel, Peter van Gelderen, Kenji Ishii, and Mark Hallett. "The Effect of Movement Amplitude on Activation in Functional Magnetic Resonance Imaging Studies." Journal of Cerebral Blood Flow & Metabolism 19, no. 11 (November 1999): 1209–12. http://dx.doi.org/10.1097/00004647-199911000-00004.
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To evaluate the effect of movement amplitude on the “blood oxygen level-dependent effect,” the authors studied six normal subjects while they extended their index finger with two different amplitudes, Images were analyzed using SPM96, In five subjects, the signal intensity increase in the primary sensorimotor area was significantly greater with the larger amplitude movement. In other areas of interest (supplementary motor area, premotor cortex, insula, postcentral area, cerebellum), the large-amplitude movement often showed significant activation when the small-amplitude movement did not. The authors conclude that, in studies of the motor system, movement amplitude needs to be controlled.
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Meng, Fan Chao, Xiao Ming Yuan, and Hui Xue. "Effect of Loading Amplitude on Soil Deformation under Irregular Waves and Fixed-Number Waves." Applied Mechanics and Materials 256-259 (December 2012): 2015–18. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.2015.
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Through series of dynamic triaxial tests, the relationships of soil deformations under irregular seismic loading and fixed-number constant amplitude loading are analyzed. The effect of loading amplitudes on the relationships is presented. The results shows: (1) soil deformation under irregular seismic loading obviously differs from that under constant amplitude sinusoidal loading, and the strain history is mainly controlled by the performance of ground motion; (2) if 20 cycles of constant amplitude loading is employed instead of irregular seismic loading to correct residual deformation under real seismic loading, loading amplitudes have no effect on soil deformation under irregular waves and fix-number waves.
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Lu, Ming-Chi, Hsing-Chung Ho, Chen-An Chan, Chia-Ju Liu, Jiann-Shing Lih, and Ming-Chung Ho. "Phase Synchronization Is the Amplified Result by the Hilbert Transform." Mathematical Problems in Engineering 2015 (2015): 1–3. http://dx.doi.org/10.1155/2015/640107.
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We investigate the interplay between phase synchronization and amplitude synchronization in nonlinear dynamical systems. It is numerically found that phase synchronization intends to be established earlier than amplitude synchronization. Nevertheless, amplitude synchronization (or the state with large correlation between the amplitudes) is crucial for the maintenance of a high correlation between two time series. A breakdown of high correlation in amplitudes will lead to a desynchronization of two time series. It is shown that these unique features are caused essentially by the Hilbert transform. This leads to a deep concern and criticism on the current usage of phase synchronization.
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Niu, Ying, Feng Jiao, Jie Li, and Jia Fei Zhang. "Study on the Effect of Vibration Amplitude in Two-Dimension Ultrasonic Vibration Cutting." Advanced Materials Research 1027 (October 2014): 131–35. http://dx.doi.org/10.4028/www.scientific.net/amr.1027.131.
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Longitudinal-bending complex vibration can be realized by opening chute on the amplitude amplifier pole. Different longitudinal and bending amplitudes can be obtained under different angles and the number of the chutes. Based on the theory of two-dimensional ultrasonic cutting, the effects of the two dimensional amplitude on the cutting characteristics were analyzed experimentally in the paper. Research results show that the amplitudes of longitudinal and bending vibration have a great effect on cutting force and machining quality in two-dimensional ultrasonic vibration cutting of hard and brittle materials. When keeping constant longitudinal amplitude and increasing bending amplitude in a certain extent, the cutting force could be reduced and the machining quality of workpiece could be improved effectively. The research provides relevant basis for designing two-dimensional longitudinal bending vibration cutting system.
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Julian, Bruce R., and G. R. Foulger. "Earthquake mechanisms from linear-programming inversion of seismic-wave amplitude ratios." Bulletin of the Seismological Society of America 86, no. 4 (August 1, 1996): 972–80. http://dx.doi.org/10.1785/bssa0860040972.
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Abstract The amplitudes of radiated seismic waves contain far more information about earthquake source mechanisms than do first-motion polarities, but amplitudes are severely distorted by the effects of heterogeneity in the Earth. This distortion can be reduced greatly by using the ratios of amplitudes of appropriately chosen seismic phases, rather than simple amplitudes, but existing methods for inverting amplitude ratios are severely nonlinear and require computationally intensive searching methods to ensure that solutions are globally optimal. Searching methods are particularly costly if general (moment tensor) mechanisms are allowed. Efficient linear-programming methods, which do not suffer from these problems, have previously been applied to inverting polarities and wave amplitudes. We extend these methods to amplitude ratios, in which formulation on inequality constraint for an amplitude ratio takes the same mathematical form as a polarity observation. Three-component digital data for an earthquake at the Hengill-Grensdalur geothermal area in southwestern Iceland illustrate the power of the method. Polarities of P, SH, and SV waves, unusually well distributed on the focal sphere, cannot distinguish between diverse mechanisms, including a double couple. Amplitude ratios, on the other hand, clearly rule out the double-couple solution and require a large explosive isotropic component.
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Lin, Feng, Shao-Qiang Cheng, Dong-Qing Qi, Yu-Er Jiang, Qian-Qian Lyu, Li-Juan Zhong, and Zhong-Li Jiang. "Brain hothubs and dark functional networks: correlation analysis between amplitude and connectivity for Broca’s aphasia." PeerJ 8 (October 1, 2020): e10057. http://dx.doi.org/10.7717/peerj.10057.
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Source localization and functional brain network modeling are methods of identifying critical regions during cognitive tasks. The first activity estimates the relative differences of the signal amplitudes in regions of interest (ROI) and the second activity measures the statistical dependence among signal fluctuations. We hypothesized that the source amplitude–functional connectivity relationship decouples or reverses in persons having brain impairments. Five Broca’s aphasics with five matched cognitively healthy controls underwent overt picture-naming magnetoencephalography scans. The gamma-band (30–45 Hz) phase-locking values were calculated as connections among the ROIs. We calculated the partial correlation coefficients between the amplitudes and network measures and detected four node types, including hothubs with high amplitude and high connectivity, coldhubs with high connectivity but lower amplitude, non-hub hotspots, and non-hub coldspots. The results indicate that the high-amplitude regions are not necessarily highly connected hubs. Furthermore, the Broca aphasics utilized different hothub sets for the naming task. Both groups had dark functional networks composed of coldhubs. Thus, source amplitude–functional connectivity relationships could help reveal functional reorganizations in patients. The amplitude–connectivity combination provides a new perspective for pathological studies of the brain’s dark functional networks.
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Noij, Kimberley S., Barbara S. Herrmann, Steven D. Rauch, and John J. Guinan Jr. "Toward Optimizing Vestibular Evoked Myogenic Potentials: Normalization Reduces the Need for Strong Neck Muscle Contraction." Audiology and Neurotology 22, no. 4-5 (2017): 282–91. http://dx.doi.org/10.1159/000485022.
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Background: The cervical vestibular evoked myogenic potential (cVEMP) represents an inhibitory reflex of the saccule measured in the ipsilateral sternocleidomastoid muscle (SCM) in response to acoustic or vibrational stimulation. Since the cVEMP is a modulation of SCM electromyographic (EMG) activity, cVEMP amplitude is proportional to muscle EMG amplitude. We sought to evaluate muscle contraction influences on cVEMP peak-to-peak amplitudes (VEMPpp), normalized cVEMP amplitudes (VEMPn), and inhibition depth (VEMPid). Methods: cVEMPs at 500 Hz were measured in 25 healthy subjects for 3 SCM EMG contraction ranges: 45-65, 65-105, and 105-500 μV root mean square (r.m.s.). For each range, we measured cVEMP sound level functions (93-123 dB peSPL) and sound off, meaning that muscle contraction was measured without acoustic stimulation. The effect of muscle contraction amplitude on VEMPpp, VEMPn, and VEMPid and the ability to distinguish cVEMP presence/absence were evaluated. Results: VEMPpp amplitudes were significantly greater at higher muscle contractions. In contrast, VEMPn and VEMPid showed no significant effect of muscle contraction. Cohen's d indicated that for all 3 cVEMP metrics contraction amplitude variations produced little change in the ability to distinguish cVEMP presence/absence. VEMPid more clearly indicated saccular output because when no acoustic stimulus was presented the saccular inhibition estimated by VEMPid was zero, unlike those by VEMPpp and VEMPn. Conclusion: Muscle contraction amplitude strongly affects VEMPpp amplitude, but contractions 45-300 μV r.m.s. produce stable VEMPn and VEMPid values. Clinically, there may be no need for subjects to exert high contraction effort. This is especially beneficial in patients for whom maintaining high SCM contraction amplitudes is challenging.
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Li, Ya Lan, Wei Peng Guo, Wen Tao Jiang, Qing Yuan Wang, and Yu Bo Fan. "Biomechanical Study on the Influence of Shaping Amplitude on Material Strenght of Titanium Implant." Applied Mechanics and Materials 275-277 (January 2013): 23–27. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.23.
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The effect of shaping amplitude on the residual material strength of titanium implants was studied. A purposely built to and fro three point bending apparatus was developed for different amplitudes on the implant material. The strength of the material after different levels of amplitude was investigated thorough uniaxial tensile testing. The effect of stress concentration due to amplitude was investigated by finite element analysis. It was concluded that plastic deformation due to shaping amplitude produced different effect on the residual strength of the material.
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Chernoyarov, O. V., A. N. Glushkov, V. P. Litvinenko, V. A. Mironov, and A. V. Salnikova. "Coherent demodulation of the two-level APSK signals with the symbol amplitude estimation." Journal of Physics: Conference Series 2094, no. 2 (November 1, 2021): 022050. http://dx.doi.org/10.1088/1742-6596/2094/2/022050.
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Abstract The study focuses on the algorithms for the coherent demodulation of the two-level amplitude phase-shift keyed signals with an estimate of the received symbol amplitude carried out by its relative comparison with the preceding symbol amplitude. Determining calibrated values of the symbol amplitudes in order to compare them with the preset threshold values is considered unnecessary in this case. Phase demodulation is implemented based on the phase detector of the multi-level phase-shift keyed signals. Symbol amplitudes are determined by the quadrature channels responses. Both analog and digital demodulation algorithms are considered. Simulation of the demodulation algorithm is carried out.
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Lalehzarian, Hamo. "Mental Workload and P300 Component of Event-Related Brain Potentials in a Visual Monitoring Task." Proceedings of the Human Factors Society Annual Meeting 32, no. 19 (October 1988): 1404–8. http://dx.doi.org/10.1177/154193128803201921.
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The attributes of event-related brain potentials (ERPs) when combined with the information gained from the study of apparent human behavior, can provide valuable information about central nervous system processes. This study illustrates the manner in which these attributes, specifically P300 amplitude, can be used to study human information processing. This research investigated the effects of a systematic increase in mental workload, and the position of the stimulus on the P300 amplitude. The task chosen was a visual monitoring task with four levels of increased task difficulty. A slight increase in the P300 amplitude was observed from level 1 to level 2. At level 3, a significant increase in the amplitude of P300 component was observed from level 2. At level four, no major increase in the P300 amplitude was observed from level 3. At any task difficulty level, the P300 amplitudes were not affected by the position of the monitored cell. Infrequent large changes in the readout value of the monitored cells elicited larger P300 amplitudes than frequent small changes.
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Nayfeh, All H. "On the Undesirable Roll Characteristics of Ships in Regular Seas." Journal of Ship Research 32, no. 02 (June 1, 1988): 92–100. http://dx.doi.org/10.5957/jsr.1988.32.2.92.
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In 1863 Froude observed that a ship whose frequency in pitch (heave) is twice its frequency in roll has undesirable roll characteristics. To explain this phenomenon, Paulling and Rosenberg as well as Kinney assumed the pitch (heave) motion to be a simple harmonic independent of the roll motion. Substituting the pitch (heave) expression into the roll equation, they obtained a Mathieu equation. They found that exponentially growing instabilities can occur for certain pitch amplitudes and frequency ratios. The exponential growth is unrealistic, the result of their neglecting the influence of the roll motion on the pitch (heave) motion. To improve their results, the present author offers an analysis for the nonlinear coupling of the pitch and roll modes of ship motions in regular seas. When the encounter frequency is near the pitch frequency, only the pitch mode is excited if the encountered wave amplitude (excitation amplitude) is small. As the excitation amplitude increases, the amplitude of the pitch mode increases in accordance with linear theory until it reaches a critical small value. As the excitation amplitude increases further, the pitch amplitude does not change from the critical value (that is, the pitch mode is saturated), and all the extra energy is transferred to the roll mode. Consequently, for large excitation amplitudes, the response is a combined roll and pitch motion, with the amplitude of the roll mode being very much larger than that of the pitch mode. More dangerously, the nonlinear theory predicts instabilities in regions where the linear theory predicts stability. Moreover, the nonlinear theory predicts conditions for the nonexistence of steady-state periodic responses. Instead, the responses can be amplitude- and phase-modulated roll and pitch motions or even chaotic. When the encounter frequency is near the roll frequency, there is no saturation phenomenon and, at close to perfect resonance, there are no steady-state periodic responses in some cases. The present results indicate that large roll amplitudes are likely in this case also. Further, the results predict the possibility of large amplitudes in the roll motion even when the ship is moving through a head or following sea.
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Khobkhun, Fuengfa, Mark Hollands, and Jim Richards. "A Comparison of Turning Kinematics at Different Amplitudes during Standing Turns between Older and Younger Adults." Applied Sciences 12, no. 11 (May 28, 2022): 5474. http://dx.doi.org/10.3390/app12115474.
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It is well-established that processes involving changing direction or turning in which either or both standing and walking turns are utilized involve coordination of the whole-body and stepping characteristics. However, the turn context and whole-body coordination have not been fully explored during different turning amplitudes. For these reasons, this present study aimed to determine the effects of turning amplitude on whole-body coordination. The findings from this study can be utilized to inform the rationale behind fall prevention factors and to help design an exercise strategy to address issues related to amplitude of turning in older adults. Twenty healthy older and twenty healthy younger adults were asked to complete standing turns on level ground using three randomly selected amplitudes, 90°, 135° and 180°, at their self-selected turn speed. Turning kinematics and stepping variables were recorded using Inertial Measurement Units. Analysis of the data was carried out using Mixed Model Analysis of Variance with two factors (2 groups × 3 turning amplitudes) and further post hoc pairwise analysis to examine differences between factors. There were significant interaction effects (p < 0.05) between the groups and turning amplitudes for step duration and turn speed. Further analysis using Repeated Measure Analysis of Variance tests determined a main effect of amplitude on step duration and turn speed within each group. Furthermore, post hoc pairwise comparisons revealed that the step duration and turn speed increased significantly (p < 0.001) with all increases in turning amplitude in both groups. In addition, significant main effects for group and amplitudes were seen for onset latency of movement for the head, thorax, pelvis, and feet, and for peak head–thorax and peak head–pelvis angular separations and stepping characteristics, which all increased with turn amplitude and showed differences between groups. These results suggest that large amplitude turns result in a change in turning and stepping kinematics. Therefore, when assessing the turning characteristics of older adults or those in frail populations, the turning amplitude should be taken into account during turning, and could be gradually increased to challenge motor control as part of exercise falls prevention strategies.
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Elkommos, Samia, David Martin-Lopez, Akihiro Koreki, Claire Jolliffe, Marco Mula, Hugo Critchley, Mark Edwards, Sarah Garfinkel, Mark P. Richardson, and Mahinda Yogarajah. "15 Attenuated heart-brain integration predicts functional non-epileptic seizures." Journal of Neurology, Neurosurgery & Psychiatry 93, no. 12 (November 14, 2022): e3.7. http://dx.doi.org/10.1136/jnnp-2022-bnpa.15.
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Objectives/AimsPatients with functional seizures (FS) can experience dissociation (depersonalisation) before their seizures. Depersonalisation encompasses a feeling of disembodiment, putatively caused by reduced afferent visceral mapping, that is, changes in interoceptive processing. The heartbeat-evoked potential (HEP) is an electroencephalographic (EEG) index of synchronised neural responses to individual heartbeats, and a marker interoceptive representation. HEP amplitude is reported to be reduced in patients with depersonalisation-derealisation disorder. The objective of this study was to assess whether alterations in interoceptive processing indexed by the HEP occur prior to FSs, and compare this with epileptic seizures (ES).MethodsHEP amplitudes were calculated from EEG during video-EEG monitoring in 25 patients with FS and 19 patients with ES, and compared between interictal and preictal states. HEP amplitudes were calculated at frontal and central EEG electrodes. HEP amplitude difference was calculated as a composite measure of preictal HEP amplitude minus interictal HEP amplitude. A Receiver Operating Characteristic (ROC) curve analysis was later used to evaluate the diagnostic performance of the HEP amplitude difference measure in discriminating functional cases from epilepsy cases.ResultsThe FS group demonstrated a significant reduction in HEP amplitude between interictal and preictal states at F8 (effect size rB=0.612, p=0.006) and C4 (rB=0.600, p=0.007). No differences in HEP amplitude were found between interictal and preictal states in the ES group. Between diagnostic groups, HEP amplitude difference was significantly different between the FS and ES group at C4 (rB=0.457, p=0.009) and F8 (rB=0.423, p=0.017). These findings were not related to heart rate, mean ECG or QRS amplitudes, which did not differ between interictal/preictal states, or groups. There was no difference in age between FS and ES groups, however there were a greater proportion of females compared to males in the FS group as compared to the ES group. Using HEP amplitude difference at frontal and central electrodes plus sex as variables, the ROC curve demonstrated an area under the curve (AUC) of 0.893, with sensitivity=0.840 and specificity=0.842 (p=0.000).ConclusionsOur data support the notion that aberrant interoception underpins disembodiment prior to dissociative FS. Changes in HEP amplitude may therefore reflect a neurophysiological biomarker of FS. HEP amplitude difference between interictal and preictal states may have diagnostic utility in differentiating FS and ES.
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Wolter, Tilman. "Spinal Cord Stimulation Inhibits Cortical Somatosensory Evoked Potentials Significantly Stronger than Transcutaneous Electrical Nerve Stimulation." Pain Physician 4;16, no. 4;7 (July 14, 2013): 405–14. http://dx.doi.org/10.36076/ppj.2013/16/405.
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Background: Despite the good clinical results elicited by spinal cord stimulation (SCS), the physiological basis of action of SCS is widely unknown. Inhibition of somatosensory evoked potential (SEP) amplitudes by SCS has been described, but it is unclear whether this displays dose dependency. Moreover, it is unknown whether the pain-relieving effect elicited by SCS correlates with the inhibition of SEPs. Finally, this study aimed to answer the question whether there is a difference in the effect on SEPs between SCS and transcutaneous electrical nerve stimulation (TENS), thus between central nervous system stimulation and peripheral nervous system stimulation. Methods: Ten patients (4 men and 6 women, age range 40-77 years) with neuropathic lower limb pain were included in the study. All patients had implanted SCS systems with percutaneous type electrodes. Cortical SEPs under SCS and TENS were measured without stimulation, under stimulation at perception threshold (PT), and at maximal threshold (MT) in a crossover design. Results: Cortical SEP amplitudes were significantly inhibited by SCS. Stimulation at PT and at MT both led to a statistically significant inhibition of the SEP amplitude. The difference between amplitude reduction at PT and MT showed a tendency towards significance. The degree of SEP amplitude inhibition did not correlate with pain relief. Inhibition of SEP amplitudes by TENS was weaker than that elicited by SCS. The average percentage of amplitude reduction at MT was twice as high under SCS as it was under TENS. No effects on SEP latencies were seen. Conclusions: SCS exerts a significantly stronger inhibition of SEP amplitudes than TENS. The data hint at a dose dependency of SCS-induced SEP amplitude inhibition. No correlation between SEP amplitude inhibition and pain relief was found. Key words: spinal cord stimulation, SCS, transcutaneous electrical nerve stimulation, TENS, neuropathic pain, somatosensory evoked potentials, SEP
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Pevzner, Roman, Olivia Collet, Stanislav Glubokovskikh, Konstantin Tertyshnikov, and Boris Gurevich. "Detection of a CO2 plume by time-lapse analysis of Rayleigh-wave amplitudes extracted from downhole DAS recordings of ocean microseisms." Leading Edge 42, no. 11 (November 2023): 763–72. http://dx.doi.org/10.1190/tle42110763.1.
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Amplitudes of Rayleigh waves are known to decrease exponentially away from the surface. If elastic properties of the solid are stratified on a scale much smaller than the wavelength, the Rayleigh-wave amplitude at a given depth should also be affected by the formation properties at that depth: the softer the medium, the larger the amplitude. An increasingly widespread deployment of fiber-optic cables in wells makes it possible to record this depth variation of Rayleigh-wave strain amplitudes and their variations over time (due to changes of formation properties) using distributed acoustic sensing (DAS). To investigate this opportunity, we have explored temporal variations of downhole DAS amplitudes of ocean-generated Rayleigh waves during injection of CO2 into a water-saturated thin porous layer. Analysis of these data clearly shows changes of these amplitudes related to the CO2 injection. To understand these amplitude variations, we perform a theoretical analysis and numerical simulations, which explain our field observations. In particular, analysis of downhole DAS data and theoretical modeling show that Rayleigh-wave amplitudes measured with vertical fiber-optic cables can be used to detect thin layers in the subsurface. Furthermore, time-lapse analysis of these amplitudes indicates temporal changes of stiffness of these layers, such as changes in saturation or pressure of the fluid in a porous layer in the vicinity of the borehole. In particular, Rayleigh-wave amplitudes are sensitive to the presence in the vicinity of the wellbore of a CO2 plume created as a result of a small injection into a thin porous reservoir layer. Our analysis also shows that the effect of a thin layer on Rayleigh-wave amplitudes strongly depends on frequency so that at different frequencies the amplitude is affected by different combinations of elastic properties. This opens an opportunity to use amplitude variations with depth at different frequencies to separately estimate changes in bulk and shear moduli.
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Bulut, Menekşe. "The effect of ultrasound times and amplitudes on the solubility and turbidity of whey protein concentrate." Food and Health 8, no. 4 (2022): 284–89. http://dx.doi.org/10.3153/fh22026.
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The current work was conducted to explore the influence of ultrasound times and amplitudes on the solubility and turbidity of whey protein concentrate (WPC). Ultrasound (US) application was employed using VC-750 ultrasonic power equipment with the frequency of 20 kHz at various times (10, 20, and 30 minutes at 50% amplitude) and amplitudes (60%, 80%, and 100% for 5 min). The outcomes exhibited that the US process have a significant impact on both solubility and turbidity (p<0.05). The highest protein recovery was obtained for the samples exposed to 30 min the US at 100% amplitude (65.56%). WPC samples treated at 100% amplitude showed higher solubility compared to the other samples at 60% and 80% amplitudes. While the solubility of WPC samples treated with 10 min showed the lowest solubility (9.13%), samples treated with 30 min showed the highest solubility (38.14%). There is a negative relationship between solubility and turbidity. All US-treated samples showed less turbidity and higher solubility where the control WPC samples showed the most turbid structure (0.88 NTU) with the lowest solubility (4.15%). Overall, US treatment with 30-minutes at 100 % amplitude showed the highest solubility (65.56%) and least turbidity (0.26 NTU) compared to the other sonication times and amplitudes.
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Dao, Duc Long. "Experimental evaluation of damping models for a nonlinear pendulum system." Physics Education 58, no. 5 (July 17, 2023): 055003. http://dx.doi.org/10.1088/1361-6552/ace1ca.
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Abstract Popular damping models for a single pendulum system were experimentally evaluated in this study. The comparison between the numerical and experimental responses showed that neither linear viscous damping model nor squared velocity proportional viscous damping model was able to well capture the free vibration amplitudes of the pendulum in both large and small amplitude ranges. Specifically, the amplitudes of the numerical model with linear viscous damping decreased slower at the large amplitude vibration but faster at the small amplitude vibration than the experimental amplitudes did. The trend was reverse in the numerical model with the squared velocity proportional viscous damping model. Based on the experimental data and a numerical method combined with a fitting approach, a complete quadratic viscous damping model for the pendulum was derived. The model was able to confidently predict the free vibration amplitudes of the pendulum in both large and small amplitude ranges. This study provides analysts with the sense of the accuracy of some popular damping models for a nonlinear pendulum system. It also demonstrates the use of a fitting approach to retrieve physical properties of a system from experimental data. The contents of this paper are suitable for gifted high school students and undergraduate students.
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Tryba, Andrew K., Fernando Peña, Steven P. Lieske, Jean-Charles Viemari, Muriel Thoby-Brisson, and Jan-Marino Ramirez. "Differential Modulation of Neural Network and Pacemaker Activity Underlying Eupnea and Sigh-Breathing Activities." Journal of Neurophysiology 99, no. 5 (May 2008): 2114–25. http://dx.doi.org/10.1152/jn.01192.2007.
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Many networks generate distinct rhythms with multiple frequency and amplitude characteristics. The respiratory network in the pre-Bötzinger complex (pre-Böt) generates both the low-frequency, large-amplitude sigh rhythm and a faster, smaller-amplitude eupneic rhythm. Could the same set of pacemakers generate both rhythms? Here we used an in vitro respiratory brainslice preparation. We describe a subset of synaptically isolated pacemakers that spontaneously generate two distinct bursting patterns. These two patterns resemble network activity including sigh-like bursts that occur at low frequencies and have large amplitudes and eupneic-like bursts with higher frequency and smaller amplitudes. Cholinergic neuromodulation altered the network and pacemaker bursting: fictive sigh frequency is increased dramatically, whereas fictive eupneic frequency is drastically lowered. The data suggest that timing and amplitude characteristics of fictive eupneic and sigh rhythms are set by the same set of pacemakers that are tuned by changes in the neuromodulatory state.
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Rumbarger, John H. "Simplification of Dynamic Capacity and Fatigue Life Estimations for Oscillating Rolling Bearings." Journal of Tribology 125, no. 4 (September 25, 2003): 868–70. http://dx.doi.org/10.1115/1.1576424.
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A Dynamic capacity for oscillating rolling bearings was published in 1968 and correlated with available laboratory fatigue life data. That development of the Dynamic Capacity extended the classic fatigue life theory of Lundberg and Palmgren (1947 and 1952) to oscillating rolling bearings. The calculation of the Dynamic Capacity is simplified as a modification of present ABMA and ISO load rating and life standards for continuously rotating rolling bearings. The simplified formulas agree with the Harris, 1991, text book formulation for oscillation amplitudes (greater than the critical amplitude) which cause an overlapping of stressed contact areas by adjacent rolling elements. Oscillation amplitudes less than the critical amplitude result in separate, discrete contact areas on each raceway. Use of the Harris equations will lead to overestimation of the fatigue for oscillation amplitudes which are less than the critical amplitude.
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Xin, K., B. Hung, S. Birdus, and J. Sun. "3D tomographic amplitude inversion for compensating amplitude attenuation." ASEG Extended Abstracts 2009, no. 1 (2009): 1. http://dx.doi.org/10.1071/aseg2009ab034.
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Davis, R. N., J. Du, A. K. Smith, W. E. Ward, and N. J. Mitchell. "The diurnal and semidiurnal tides over Ascension Island (° S, 14° W) and their interaction with the stratospheric quasi-biennial oscillation: studies with meteor radar, eCMAM and WACCM." Atmospheric Chemistry and Physics 13, no. 18 (September 27, 2013): 9543–64. http://dx.doi.org/10.5194/acp-13-9543-2013.
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Abstract. Horizontal winds in the mesosphere have been measured over Ascension Island (8° S, 14° W) in the tropical mid-Atlantic region throughout the years 2002–2011. The observations were made by a very high frequency (VHF) meteor radar. The observations reveal the presence of atmospheric tides of large amplitude. The observations are analysed to characterise the seasonal and interannual variability of the diurnal and semidiurnal tides. Monthly-mean diurnal tidal amplitudes are found to reach values as large as 48 m s−1 in the meridional component and 41 m s−1 in the zonal. A semiannual seasonal variation is found in diurnal tidal amplitudes with amplitude maxima at the equinoxes and amplitude minima at the solstices. Diurnal tidal meridional vertical wavelengths are generally in the range 24–30 km. The diurnal zonal vertical wavelengths are similar to the meridional, except for the winter months when the zonal vertical wavelengths are much longer, occasionally exceeding 100 km. Semidiurnal amplitudes are observed to be significantly smaller than diurnal amplitudes. Semidiurnal vertical wavelengths range from 20 to more than 100 km. Our observations of tidal amplitudes and phases are compared with the predictions of the extended Canadian Middle Atmosphere Model (eCMAM) and the Whole Atmosphere Community Climate Model (WACCM). Both eCMAM and WACCM reproduce the trend for greater diurnal amplitudes in the meridional component than the zonal. However, eCMAM tends to overestimate meridional amplitudes, while WACCM underestimates both zonal and meridional amplitudes. Vertical wavelength predictions are generally good for both models; however, eCMAM predicts shorter diurnal zonal vertical wavelengths than are observed in winter, while WACCM predicts longer zonal vertical wavelengths than observed for the semidiurnal tide for most months. Semidiurnal amplitude predictions are generally good for both models. It is found that larger-than-average diurnal and semidiurnal tidal amplitudes occur when the stratospheric quasi-biennial oscillation (QBO) at 10 hPa is eastwards, and smaller-than-average amplitudes occur when it is westwards. Correlations between the amplitude perturbations and the El Niño Southern Oscillation are also found. The precise mechanism for these correlations remains unclear.
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Kaf, Wafaa A., and Ali A. Danesh. "Air-Conduction Auditory Steady-State Response: Comparison of Interchannel Recording Using Two Modulation Frequencies." Journal of the American Academy of Audiology 19, no. 09 (October 2008): 696–707. http://dx.doi.org/10.3766/jaaa.19.9.5.
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Background: Two-channel auditory steady-state response (ASSR) recording at high and low MF (modulation frequency) most likely provides an insight about the response amplitude and latency from different directions at the brainstem level and at the thalamus or cortical level. Little is known about the combined relationship between MF (39 and 79 Hz) and electrode montages (ipsilateral and contralateral) to single AM (amplitude modulation) tones on the ASSR amplitude and latency. Purpose: To determine if ipsilateral versus contralateral response asymmetries are present at the brainstem level (79 Hz ASSR) and at the thalamus or cortical levels (39 Hz ASSR). Research Design: Descriptive and inferential statistics for interchannel ipsilateral and contralateral ASSR amplitude and latency to 79 and 39 Hz. Study Sample: Twenty-five normal-hearing, right-handed young female adults participated in the study. All participants were right-handed, and their age ranged between 18 to 28 years (mean 24.5 ± 1.6 years). Data Collection and Analysis: Ipsilateral and contralateral ASSR to 39 and 79 Hz MF and 100% AM stimuli were recorded at 500, 2000, and 4000 Hz carrier frequencies at 65 dB SPL. The ASSR amplitudes and phases were determined for each MF across Fc (carrier frequency) for the two channels to the test (right) ear. ASSR amplitude and latency between recording montages for each MF and across carrier frequency were compared by computing two-way repeated measures ANOVA. Results: The mean ipsilateral ASSR amplitudes to 39 Hz across frequency were slightly larger (228.6 ± 61.6 µV) than the contralateral response amplitude (223.2 ± 78 µV) while the mean ipsilateral 79 Hz amplitudes were smaller (127.3 ± 114.8) compared to contralateral 79 Hz amplitude (154.6 ± 112.7 µV). For latency response, the mean ipsilateral/contralateral latency difference, on average, was 1 msec or less for both MFs. Results, in normal female adults, indicated no significant interchannel ASSR asymmetries for amplitude and latency (p > 0.05) at the brainstem (79 Hz ASSR) and at the thalamus or cortical levels (39 Hz ASSR). Conclusions: Interchannel ipsilateral and contralateral ASSR amplitude and latency to 79 and 39 Hz are not significantly different in normal, young female adults. Two-channel recording of ASSR to different MFs may be of clinical value in otoneurologic assessment.
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Hamdi, Mustapha, and Mohamed Belhaq. "Quasi-periodic vibrations in a delayed van der Pol oscillator with time-periodic delay amplitude." Journal of Vibration and Control 24, no. 24 (August 18, 2015): 5726–34. http://dx.doi.org/10.1177/1077546315597821.
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Quasi-periodic vibrations in a delayed van der Pol oscillator with time-periodic delay amplitude is investigated in this paper. The case where the delay amplitude in the position is modulated with a certain amplitude and a resonant frequency is considered. Application of the double perturbation method enables approximation of the amplitudes of quasi-periodic vibrations of the oscillator near a parametric resonance for which the frequency of the delay amplitude modulation is near twice the natural frequency of the oscillator. Analytical approximations supported by numerical simulations provide the regions in parameter space where quasi-periodic vibrations exist. Results show that the modulation of the delay amplitude in the position not only gives birth to quasi-periodic vibrations in a large range of parameters, but also with broadband large-amplitude covering a wide range of excitation frequency.
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Szabados, L. "New Ways of Revealing Cepheid Binaries." International Astronomical Union Colloquium 139 (1993): 406–7. http://dx.doi.org/10.1017/s0252921100118068.
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AbstractTwo methods involving the observed amplitudes of radial velocity and UBVR light variations for classical Cepheids have been analysed, both being implicitly known: their principle is trivial but these methods had not yet been used systematically as indicators of duplicity.The slope method is based on the alteration of the wavelength dependence of the light variation amplitude if either a blue or a red companion is added to the light of the Cepheid. The amplitude ratio (AR) method makes use of the fact that the companion reduces the amplitude of the light variation without observable effect on the pulsational radial velocity amplitude. This means that the ratio of these two amplitudes (Arad.vel./AB) has a larger value for binary Cepheids as compared with the single pulsators.Each method has been applied to more than 100 Cepheids, thus allowing to study how the uncontaminated parameters (amplitude ratio and slope) depend on the pulsation period. Binary Cepheids deviate from the regular pattern in these diagrams, and a number of new binaries can be discovered in this way. The effect of duplicity is revealed by both methods independently for VZ CMa, FM Cas, CR Cep, V402 Cyg, VI154 Cyg, V440 Per and DR Vel.
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Dellinger, Joe A., Samuel H. Gray, Gary E. Murphy, and John T. Etgen. "Efficient 2.5-D true‐amplitude migration." GEOPHYSICS 65, no. 3 (May 2000): 943–50. http://dx.doi.org/10.1190/1.1444790.
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Kirchhoff depth migration is a widely used algorithm for imaging seismic data in both two and three dimensions. To perform the summation at the heart of the algorithm, standard Kirchhoff migration requires a traveltime map for each source and receiver. True‐amplitude Kirchhoff migration in 2.5-D υ(x, z) media additionally requires maps of amplitudes, out‐of‐plane spreading factors, and takeoff angles; these quantities are necessary for calculating the true‐amplitude weight term in the summation. The increased input/output (I/O) and computational expense of including the true‐amplitude weight term is often not justified by significant improvement in the final muted and stacked image. For this reason, some authors advocate neglecting the weight term in the Kirchhoff summation entirely for most everyday imaging purposes. We demonstrate that for nearly the same expense as ignoring the weight term, a much better solution is possible. We first approximate the true‐amplitude weight term by the weight term for constant‐velocity media; this eliminates the need for additional source and receiver maps. With one small additional approximation, the weight term can then be moved entirely outside the innermost loop of the summation. The resulting Kirchhoff method produces images that are almost as good as for exact true‐amplitude Kirchhoff migration and at almost the same cost as standard methods that do not attempt to preserve amplitudes.
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Bogle, Jamie M., David A. Zapala, Robin Criter, and Robert Burkard. "The Effect of Muscle Contraction Level on the Cervical Vestibular Evoked Myogenic Potential (cVEMP): Usefulness of Amplitude Normalization." Journal of the American Academy of Audiology 24, no. 02 (February 2013): 077–88. http://dx.doi.org/10.3766/jaaa.24.2.2.
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Background: The cervical vestibular evoked myogenic potential (cVEMP) is a reflexive change in sternocleidomastoid (SCM) muscle contraction activity thought to be mediated by a saccular vestibulo-collic reflex. CVEMP amplitude varies with the state of the afferent (vestibular) limb of the vestibulo-collic reflex pathway, as well as with the level of SCM muscle contraction. It follows that in order for cVEMP amplitude to reflect the status of the afferent portion of the reflex pathway, muscle contraction level must be controlled. Historically, this has been accomplished by volitionally controlling muscle contraction level either with the aid of a biofeedback method, or by an a posteriori method that normalizes cVEMP amplitude by the level of muscle contraction. A posteriori normalization methods make the implicit assumption that mathematical normalization precisely removes the influence of the efferent limb of the vestibulo-collic pathway. With the cVEMP, however, we are violating basic assumptions of signal averaging: specifically, the background noise and the response are not independent. The influence of this signal-averaging violation on our ability to normalize cVEMP amplitude using a posteriori methods is not well understood. Purpose: The aims of this investigation were to describe the effect of muscle contraction, as measured by a prestimulus electromyogenic estimate, on cVEMP amplitude and interaural amplitude asymmetry ratio, and to evaluate the benefit of using a commonly advocated a posteriori normalization method on cVEMP amplitude and asymmetry ratio variability. Research Design: Prospective, repeated-measures design using a convenience sample. Study Sample: Ten healthy adult participants between 25 and 61 yr of age. Intervention: cVEMP responses to 500 Hz tone bursts (120 dB pSPL) for three conditions describing maximum, moderate, and minimal muscle contraction. Data Collection and Analysis: Mean (standard deviation) cVEMP amplitude and asymmetry ratios were calculated for each muscle-contraction condition. Repeated measures analysis of variance and t-tests compared the variability in cVEMP amplitude between sides and conditions. Linear regression analyses compared asymmetry ratios. Polynomial regression analyses described the corrected and uncorrected cVEMP amplitude growth functions. Results: While cVEMP amplitude increased with increased muscle contraction, the relationship was not linear or even proportionate. In the majority of cases, once muscle contraction reached a certain “threshold” level, cVEMP amplitude increased rapidly and then saturated. Normalizing cVEMP amplitudes did not remove the relationship between cVEMP amplitude and muscle contraction level. As muscle contraction increased, the normalized amplitude increased, and then decreased, corresponding with the observed amplitude saturation. Abnormal asymmetry ratios (based on values reported in the literature) were noted for four instances of uncorrected amplitude asymmetry at less than maximum muscle contraction levels. Amplitude normalization did not substantially change the number of observed asymmetry ratios. Conclusions: Because cVEMP amplitude did not typically grow proportionally with muscle contraction level, amplitude normalization did not lead to stable cVEMP amplitudes or asymmetry ratios across varying muscle contraction levels. Until we better understand the relationships between muscle contraction level, surface electromyography (EMG) estimates of muscle contraction level, and cVEMP amplitude, the application of normalization methods to correct cVEMP amplitude appears unjustified.
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Singh, Ram Janma. "Exploration application of seismic amplitude analysis in the Krishna-Godavari Basin, east coast of India." Interpretation 2, no. 4 (November 1, 2014): SP5—SP20. http://dx.doi.org/10.1190/int-2013-0197.1.
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Seismic amplitude anomalies are attractive exploration targets in the Krishna-Godavari Basin offshore India. These bright spots mostly have very high amplitudes, so confident interpretations have been possible. We distinguished between hydrocarbon-bearing sands, water-bearing sands, and high-impedance nonreservoir bodies. Also, we mapped channel architecture and accurately predicted reservoir thickness. Strong amplitude anomalies, prospective seismic character based on an understanding of data phase and polarity, flat spots, and amplitude versus offset have all provided valuable evidence.
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Jin, O., H. Lee, and S. Mall. "Investigation Into Cumulative Damage Rules to Predict Fretting Fatigue Life of Ti-6Al-4V Under Two-Level Block Loading Condition1." Journal of Engineering Materials and Technology 125, no. 3 (July 1, 2003): 315–23. http://dx.doi.org/10.1115/1.1590998.
Full textAbstract:
The effects of variable amplitude loading on fretting fatigue behavior of titanium alloy, Ti-6Al-4V were examined. Fretting fatigue tests were carried out under constant stress amplitude and three different two-level block loading conditions: high-low (Hi-Lo), low-high (Lo-Hi), and repeated block of high and low stress amplitudes. The damage fractions and fretting fatigue lives were estimated by linear and non-linear cumulative damage rules. Damage curve analysis (DCA) and double linear damage rule (DLDR) were capable to account for the loading order effects in Hi-Lo and Lo-Hi loadings. In addition, the predictions by DCA and DLDR were better than that by linear damage rule (LDR). Besides its simplicity of implementation, LDR was also capable of estimating failure lives reasonably well. Repeated two-level block loading resulted in shorter lives and lower fretting fatigue limit compared to those under constant amplitude loading. The degree of reduction in fretting fatigue lives and fatigue strength depended on the ratio of cycles at lower stress amplitude to that at higher stress amplitude. Fracture surface of specimens subjected to Hi-Lo and repeated block loading showed the clear evidence of change in stress amplitude of applied load. Especially, the repeated two-level block loading resulted in characteristic markers which reflected change in crack growth rates corresponding to different stress amplitudes.
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Zheng, Yi, Shaoting Tang, Hongwei Zheng, Xin Wang, Longzhao Liu, Yaqian Yang, Yi Zhen, and Zhiming Zheng. "Noise improves the association between effects of local stimulation and structural degree of brain networks." PLOS Computational Biology 19, no. 5 (May 11, 2023): e1010866. http://dx.doi.org/10.1371/journal.pcbi.1010866.
Full textAbstract:
Stimulation to local areas remarkably affects brain activity patterns, which can be exploited to investigate neural bases of cognitive function and modify pathological brain statuses. There has been growing interest in exploring the fundamental action mechanisms of local stimulation. Nevertheless, how noise amplitude, an essential element in neural dynamics, influences stimulation-induced brain states remains unknown. Here, we systematically examine the effects of local stimulation by using a large-scale biophysical model under different combinations of noise amplitudes and stimulation sites. We demonstrate that noise amplitude nonlinearly and heterogeneously tunes the stimulation effects from both regional and network perspectives. Furthermore, by incorporating the role of the anatomical network, we show that the peak frequencies of unstimulated areas at different stimulation sites averaged across noise amplitudes are highly positively related to structural connectivity. Crucially, the association between the overall changes in functional connectivity as well as the alterations in the constraints imposed by structural connectivity with the structural degree of stimulation sites is nonmonotonically influenced by the noise amplitude, with the association increasing in specific noise amplitude ranges. Moreover, the impacts of local stimulation of cognitive systems depend on the complex interplay between the noise amplitude and average structural degree. Overall, this work provides theoretical insights into how noise amplitude and network structure jointly modulate brain dynamics during stimulation and introduces possibilities for better predicting and controlling stimulation outcomes.
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Zhou, Xiaoguo, Qingdian Jiang, Yan Wang, Linfeng Chen, Shuqi Wang, and Kunpeng Wang. "Numerical Simulation of Wave–Current Force Characteristics of Horizontal Floating Cylinder in Heave Motion." Journal of Marine Science and Engineering 10, no. 12 (December 4, 2022): 1884. http://dx.doi.org/10.3390/jmse10121884.
Full textAbstract:
This paper presents the characteristics of the heave motion responses and hydrodynamic forces of a horizontal floating circular cylinder during a wave–current interaction. A two-dimensional numerical model based on the CFD (Computational Fluid Dynamics) method for modeling wave flow is validated and verified. The hydrodynamic characteristics of the horizontal floating cylinder during heave motion were calculated and analyzed under the conditions of different k values (stiffness of spring), wave amplitudes, submerged depths, and flow rates. The results show that, with the increase in the k value, the vibration amplitude of the cylinder first increases and then decreases. The vibration amplitude peak is achieved, the vibration frequency is consistent with the wave frequency, and a resonant motion takes place. When the wave amplitude and flow rate are fixed, the maximum vibration amplitude decreases as the wave period increases. When the cylinder is half-submerged, the effect of the current on motion is significant; the vibration amplitude is less than the wave amplitude. When a quarter is submerged, the vibration amplitude is larger than that of the half-submerged cylinder at each k. The maximum amplitude is greater than the wave amplitude, and the vibration amplitude reaches the minimum at the moderate flow rate for each k.
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Tucker, Denise A., Susan Dietrich, Stacy Harris, and Sarah Pelletier. "Effects of Stimulus Rate and Gender on the Auditory Middle Latency Response." Journal of the American Academy of Audiology 13, no. 03 (March 2002): 146–53. http://dx.doi.org/10.1055/s-0040-1715956.
Full textAbstract:
The effects of stimulus rate and gender on the auditory middle latency response (AMLR) waveforms were examined in 20 young adult male and female subjects. Four different repetition rates were presented to subjects (1.1/sec, 4.1/sec, 7.7/sec, and 11.3/sec). Stimulus repetition rate had a significant effect on Pa latency, Pa amplitude, and Pb amplitude. Pa and Pb amplitudes decreased with increasing the stimulus rate, and Pa latency significantly increased with increasing the stimulus rate. No significant differences were seen on Pb latency or site of recording. Gender had a significant effect on Pa latency and Pa amplitude. Pa latencies were longer in male subjects, and Pa amplitudes were larger in female subjects. Gender did not have a significant effect on the Pb waveform.