Maximum amplification band of a CRM twistron

1977 ◽  
Vol 20 (8) ◽  
pp. 846-849 ◽  
Author(s):  
M. A. Moiseev
Keyword(s):  
Amplification Band ◽  
Maximum Amplification

A Numerical Study on the Seismic Site Response of Rocky Valleys with Irregular Topographic Conditions

2019 ◽  
Vol 10 (04) ◽  
pp. 1850011 ◽  
Author(s):  
Mohammad Katebi ◽  
Behrouz Gatmiri ◽  
Pooneh Maghoul
Keyword(s):  
Seismic Analysis ◽  
Numerical Study ◽  
Site Response ◽  
Slope Angle ◽  
Response Spectra ◽  
Topographic Effects ◽  
Combined Effects ◽  
Acceleration Response ◽  
Vertically Propagating ◽  
Maximum Amplification

This paper investigates topographic effects of rocky valleys with irregular topographic conditions subjected to vertically propagating SV waves of Ricker type using a boundary element code. Valleys with two intersecting slopes, [Formula: see text] and [Formula: see text], are modelled in order to study their combined effects on ground motion. Presented in the form of pseudo-acceleration response spectra, results of this work can be extended to similar topographies. The main findings are: (i) [Formula: see text] (the first slope angle) and [Formula: see text] (L is the half width of the valley and [Formula: see text] is its corresponding height) have amplifying effects, and [Formula: see text] (the second slope angle) has de-amplifying effects on the site response. (ii) [Formula: see text] has a straight effect on intensifying the effects of both [Formula: see text] and [Formula: see text]. (iii) The combined effects of slope angles have been found to be important in modifying the response so more than a single slope should be considered for seismic analysis. (iv) Engineers should use the maximum amplification of 2.4 in case of valleys with the first and second slope angles below [Formula: see text].

The Meniscus Instability of a Thin Liquid Film

1988 ◽  
Vol 55 (4) ◽  
pp. 975-980 ◽  
Author(s):  
H. Koguchi ◽  
M. Okada ◽  
K. Tamura
Keyword(s):  
Thin Film ◽  
Analytical Solution ◽  
Liquid Film ◽  
Tilt Angle ◽  
Stability Criterion ◽  
Thin Liquid Film ◽  
Normal Direction ◽  
Wave Number ◽  
The Stability ◽  
Maximum Amplification

This paper reports on the instability for the meniscus of a thin film of a very viscous liquid between two tilted plates, which are separated at a constant speed with a tilt angle in the normal direction of the plates. The disturbances on the meniscus moving with movement of the plates are examined experimentally and theoretically. The disturbances are started when the velocity of movement of the plates exceeds a critical one. The wavelength of the disturbances is measured by using a VTR. The instability of the meniscus is studied theoretically using the linearized perturbation method. A simple and complete analytical solution yields both a stability criterion and the wave number for a linear thickness geometry. These results compared with experiments for the instability show the validity of the stability criterion and the best agreement is obtained with the wave number of maximum amplification.

Feasibility of the use of Microtremors in Estimating Site Response during Earthquakes: Some Test Cases in Italy

1991 ◽  
Vol 7 (4) ◽  
pp. 551-561 ◽  
Author(s):  
Antonio Rovelli ◽  
Shri K. Singh ◽  
Luca Malagnini ◽  
Alessandro Amato ◽  
Massimo Cocco
Keyword(s):  
Ground Motion ◽  
Seismic Waves ◽  
Site Response ◽  
Spectral Ratio ◽  
Test Cases ◽  
Spectral Ratios ◽  
Cultural Noise ◽  
Maximum Amplification

We explore the feasibility of the use of microtremors in estimating the amplification of seismic waves at soft sites in Italy. Microtremors were measured at three soft sites and nearby hard sites at night when the cultural noise was minimum. These soft sites were selected as those showing the largest amplifications of ground motion during earthquakes as compared to the records on the hard sites or with respect to the predicted spectra. We compare the soft-to-hard site microtremor spectral ratios with the corresponding acceleration spectral ratios. A rough estimate of the shape and level of spectral amplification is obtained from the microtremor data in all three cases. However, the details of the soft-to-hard site spectral ratio are not reproduced and some differences appear in (a) the frequency at which the maximum amplification occurs, and (b) the bandwidth of the significant amplification. More testing of the method is needed before its wider use for microzonation in Italy can be recommended.

An experiment on the stability of hypersonic laminar boundary layers

1960 ◽  
Vol 7 (3) ◽  
pp. 385-396 ◽  
Author(s):  
Anthony Demetriades
Keyword(s):  
Boundary Layer ◽  
Flat Surface ◽  
Hypersonic Boundary Layer ◽  
Natural Disturbances ◽  
Hot Wire ◽  
Amplitude Variation ◽  
Laminar Boundary Layers ◽  
Boundary Layer Instability ◽  
The Stability ◽  
Maximum Amplification

An experimental investigation of the hydrodynamic stability of the laminar hypersonic boundary layer was carried out with the aid of a hot-wire anemometer. The case investigated was that of a flat surface at zero angle of attack and no heat transfer.The streamwise amplitude variation of both natural disturbances and of disturbances artifically excited with a siren mechanism was studied. In both cases it was found that such small fluctuations amplify for certain ranges of frequency and Reynolds number Rθ, and damp for others. The demarcation boundaries for the amplification (instability) zone were found to resemble the corresponding limits of boundary-layer instability at lower speeds. A ‘line of maximum amplification’ of disturbances was also found. The amplification rates and hence the degree of selectivity of the hypersonic layer were found, however, to be considerably lower than those at the lower speeds. The disturbances selected by the layer for maximum amplifications have a wavelength which was estimated to be about twenty times the boundary-layer thickness δ.

scholarly journals Performance Evaluation of a Resonant-integrated Pumping System

2018 ◽  
Vol 202 ◽  
pp. 02009
Author(s):  
Vincent Chieng-Chen Lee
Keyword(s):  
Performance Evaluation ◽  
Excitation Frequency ◽  
Pressure Head ◽  
Low Noise ◽  
Integrated System ◽  
Positive Outcomes ◽  
Pumping System ◽  
At Resonance ◽  
Impedance Pump ◽  
Maximum Amplification

Impedance pump is a simple valve-less pumping mechanism; it offers a low energy, low noise alternative at both macro- and micro-scale devices. It is also demonstrated to be a promising new technique for producing and amplifying net flow. There have been research studying the effects of series-connected impedance pump, where an increase in net flow is exhibited. In this study, an integrated system of conventional pump and impedance pump is introduced. This paper describes the performance evaluation of this integrated pumping system, with emphasis on the amount of amplification induced as a function of Womersley number (normalized excitation frequency) and normalized pressure head. Due to the nature of the resonant valve-less impedance pump, the integrated pumping system exhibits similar behaviour and characteristics as an impedance pump, such as the pulsatile nature of net flow. Results show positive outcomes where maximum amplification of 91.7% is demonstrated at resonance.

Reflex Organization in the Swimmeret System of the Lobster

1969 ◽  
Vol 51 (3) ◽  
pp. 565-573
Author(s):  
W. J. DAVIS
Keyword(s):  
Dynamic Properties ◽  
Motor Command ◽  
Homarus Americanus ◽  
Reflex Response ◽  
Limb Position ◽  
Cycle Basis ◽  
Sinusoidal Movement ◽  
Wide Range ◽  
Motor Neurones ◽  
Maximum Amplification

1. The dynamic properties of the intrasegmental swimmeret reflexes of the lobster Homarus americanus were studied by recording the discharge of the motor neurones while the swimmeret was moved sinusoidally in its natural arc over a wide range of frequencies. 2. The reflex responses of the excitor neurones of both powerstroke (retractor) and returnstroke (protractor) muscles display hysteresis. In both cases the efferent response corresponding to a given limb position is usually greater during imposed retraction than during protraction. 3. The cyclic efferent reflex response follows the sinusoidal movement stimulus at movement frequencies up to and beyond those which occur naturally during swimmeret beating, with no change in the position of maximum reflex activity in the cycle. The reflexes are therefore capable of influencing the motor output on a cycle-by-cycle basis. 4. The strength of the reflex response is maximum between 1 and 3 Hz. of imposed movement, and declines to either side of this range. The dynamic properties of the reflexes are therefore adjusted so that the maximum amplification of the rhythmic central motor command occurs at the natural frequency of swimmeret beating.

Maximum Amplification of Blade Response in Mistuned Multi Stage Assemblies

2010 ◽  
Author(s):  
Javier Avalos ◽  
Marc P. Mignolet
Keyword(s):  
Mass Matrix ◽  
Optimization Strategy ◽  
Single Degree Of Freedom ◽  
Reduced Order ◽  
Multi Stage ◽  
Maximum Amplification ◽  
Blade Model ◽  
Computational Validation ◽  
Theoretical Developments

This paper focuses on the determination of the maximum amplification of blade response due to mistuning in multi stage assemblies. The modal optimization strategy developed earlier in connection with single stage models is extended here to multi stage configurations. Theoretical developments are carried out first and lead to the new upper limit of (1+N1+N2(g2/g1)+…)/2, where Ni are the number of blades on the stages and gi = FiTMi−1Fi with Fi the force vector applied on a sector of stage i and Mi its mass matrix. For identical stages, this maximum equals the Whitehead limit observed with single stages but with the number of blades equal to sum of the numbers of blades of the coupled stages. A computational validation of the theoretical results is achieved next on both a single degree of freedom per blade model and a reduced order model of a blisk. These numerical optimization efforts confirm the theoretical developments and demonstrate that such high amplification factors can indeed be achieved with small levels of mistuning. The effects of the number of blades on the different stages, damping in the system, stage coupling strength, etc are discussed in details.

Fourfold amplification of solitary-wave Mach reflection at a vertical wall

2019 ◽  
Vol 861 ◽  
pp. 517-523 ◽  
Author(s):  
Jeffrey Knowles ◽  
Harry Yeh
Keyword(s):  
Solitary Wave ◽  
Mach Reflection ◽  
Vertical Wall ◽  
Higher Order ◽  
Obliquely Incident ◽  
Maximum Amplification

With the use of a higher-order Euler formulation, we numerically study the reflection of an obliquely incident solitary wave at a vertical wall and compare results with the higher-order Kadomtsev–Petviashvili theory. A maximum amplification of 3.91 is achieved along the wall, nearly realizing the fourfold prediction by Miles (J. Fluid Mech., vol. 79 (1), 1977, pp. 171–179).

scholarly journals Research on the enhancement of power-load of two-cell SBS system by choosing different media or mixture medium

2007 ◽  
Vol 25 (2) ◽  
pp. 207-210 ◽  
Author(s):  
W.L.J. Hasi ◽  
Z.W. Lu ◽  
Q. Li ◽  
W.M. He
Keyword(s):  
System Performance ◽  
Brillouin Scattering ◽  
Cell System ◽  
Amplification Efficiency ◽  
Mixing Ratio ◽  
Close Vicinity ◽  
Power Load ◽  
Mixed Medium ◽  
Stimulated Brillouin ◽  
Maximum Amplification

In order to enhance the power-load of two-cell stimulated Brillouin scattering (SBS) system, methods of using different media and mixed medium are proposed. In theory, the amplification function of two-cell system of different medium with close vicinity in the Brillouin frequency shift (BFS) is analyzed. Also the variation of BFS of the mixed medium with the mixing ratio is analyzed. In the two-cell SBS system pumped by Q-switched Nd:YAG laser, the SBS system performance characteristics are investigated with different media and mixed medium. The experimental results indicate that the Stokes can be sufficiently amplified by choosing different medium with close vicinity in the BFS; the power-load performance is enhanced as well as the maximum amplification efficiency the Stokes by choosing mixed medium.

scholarly journals Mismatch Between the Resting Membrane Potential and the Voltage at Maximum Amplification in Outer Hair Cells (OHCS) of Mammalian Cochlea

2014 ◽  
Vol 106 (2) ◽  
pp. 794a
Author(s):  
Varun K.A. Sreenivasan ◽  
Christian Corbitt ◽  
Federica Farinelli ◽  
William E. Brownell ◽  
Brenda Farrell
Keyword(s):  
Membrane Potential ◽  
Hair Cells ◽  
Outer Hair Cells ◽  
Resting Membrane Potential ◽  
Maximum Amplification
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