Theoretical model and dynamic wave-amplification effect of the high intensity Helmholtz sound source

2021 ◽  
pp. 107754632110429
Author(s):  
Zhenghui Qiao ◽  
Mei Cheng ◽  
Yawei Jin
Keyword(s):  
Theoretical Model ◽  
Sound Source ◽  
High Intensity ◽  
Maximum Amplitude ◽  
Helmholtz Resonator ◽  
Pressure Amplitude ◽  
Wave Amplification ◽  
Amplification Effect ◽  
Impedance Parameters ◽  
Dynamic Amplification

Helmholtz sound source consists of Helmholtz resonator and speaker and belongs to a new type of high-intensity sound source. It has potential industrial advantage in the aerodynamic acoustic application for the large amplitude wave. Based on the lumped parameter principle of acoustic impedance, an acoustic theoretical model is suggested. The model reveals the amplification regulation of the sound source on the acoustic wave. Through the acoustic theoretical computation, a dynamic amplification and an amplification limitation are analyzed. The wave-amplification effect attributes to the parameter regulation of the macro, micro, and dynamic-varied sizes of the sound source. The repetitive motion of the vibrating membrane of speaker causes three working states of balance, squeeze, and stretch. The three states act as specific boundary conditions and demonstrate as three different theoretical curves. The theoretical boundary curves codetermine an experimental curve, which essentially limits the practical amplification effect. Nevertheless, the amplification gain of sound pressure amplitude reaches up to 1.8 times, and the potential maximum amplitude reaches up to 3600 Pa (164 dB). The two quantitative characteristics indicate the maximum capability of the sound source on wave-amplification effect. The control sensitivity of the complicated impedance parameters on wave amplification is 0.26 Pa/Hz. The acoustic theoretical model is valuable in the series aspects of the industrial design, manufacture, and application of the sound source. Especially, the theoretical innovation lays the foundation of solid to these aspects.

scholarly journals Professional activists? Party activism among political staffers in parliamentary democracies

2021 ◽  
pp. 135406882110273
Author(s):  
Pieter Moens
Keyword(s):  
Theoretical Model ◽  
Survey Data ◽  
High Intensity ◽  
Supply And Demand ◽  
Parliamentary Democracies ◽  
Coalition Governments ◽  
Depth Analysis ◽  
Strong Commitment ◽  
Staff Recruitment

Although the position of the party on the ground has been weakened by cartelization, grassroots activists remain an important recruitment pool for political professionals. Based on unique survey data collected among the staff of 14 Belgian and Dutch parties (N = 1009), this article offers an in-depth analysis of party activism among this under-researched population. Introducing a new supply and demand framework, I argue that staff recruitment is shaped by candidate preferences (supply) and party preferences (demand). The findings demonstrate that most political staffers are high-intensity activists with a strong commitment to their party. Moreover, the theoretical model accurately predicts that non-activists are more common among policy and communication experts, ministerial staff, and those working for ideologically moderate parties. These findings show that paid staffers do not necessarily widen the gap between parties and activists. They also raise normative questions about internal congruence within parties in coalition governments.

THE ELECTROACOUSTIC HORN—A New High‐Intensity Sound Source

1969 ◽  
Vol 46 (6A) ◽  
pp. 1406-1409
Author(s):  
R. M. G. Boucher ◽  
J. Kreuter
Keyword(s):  
Sound Source ◽  
High Intensity

Nonlinear Derating of High-Intensity Therapeutic Ultrasound Beams Using Gaussian Modal Sums

2013 ◽  
Author(s):  
Seyed Ahmad Reza Dibaji ◽  
Matthew R. Myers ◽  
Joshua E. Soneson ◽  
Rupak K. Banerjee
Keyword(s):  
High Intensity ◽  
Focused Ultrasound ◽  
High Intensity Focused Ultrasound ◽  
Nonlinear Propagation ◽  
Tissue Temperature ◽  
Medical Procedure ◽  
Pressure Amplitude ◽  
Pressure Trace ◽  
The Difference ◽  
Semi Empirical

High intensity focused ultrasound (HIFU) is a noninvasive medical procedure during which a large amount of energy is deposited in a short duration which causes sudden localized rise in tissue temperature, and ultimately, cell necrosis. In assessing the influence of HIFU on biological tissue, semi-empirical mathematical models can be useful for predicting thermal effects. These models require values of the pressure amplitude in the tissue of interest, which can be difficult to obtain experimentally. One common method for estimating the pressure amplitude in tissue is to operate the HIFU transducer in water, measure the pressure amplitude, then multiply by a scaling factor that accounts for the difference in attenuation between water and tissue. This procedure can be accurate when the ultrasound amplitude is low, and the pressure trace in tissue is proportional to that in water. Because of this proportionality, the procedure for reducing the amplitude from water to tissue is called linear derating. At higher intensities, however, harmonics of the fundamental frequency are generated due to nonlinear propagation effects. Higher harmonics are attenuated differently in water and tissue (Hamilton and Blackstock [1]), and the pressure waves in water and tissue are no longer proportional to one another. Techniques for nonlinearly transforming pressure amplitudes measured in water to values appropriate for tissue are therefore desirable when bioeffects of higher intensity procedures are being studied. These techniques are labeled “nonlinear derating”.

Design and Simulation of a Polarization-Independent Active Metamaterial Terahertz Modulator

2013 ◽  
Vol 455 ◽  
pp. 167-172 ◽  
Author(s):  
Li Shuang Feng ◽  
Bo Hao Yin ◽  
Zhen Zhou ◽  
Jia Wei Sui ◽  
Chen Long Li
Keyword(s):  
Theoretical Model ◽  
Resonance Frequency ◽  
Amplitude Modulation ◽  
Modulation Depth ◽  
Maximum Amplitude ◽  
High Modulation ◽  
Terahertz Communication ◽  
Modulation Rate ◽  
Polarization Independent ◽  
Modulation Speed

The design and simulation of a polarization-independent active metamaterial terahertz modulator is presented in this work. The device incorporates an array of gold triple SRRs on an n-doped gallium arsenide layer to create an active metamaterial terahertz modulator with a high modulation depth, a high modulation speed and an especial polarization-independent performance for use in terahertz communication, imaging and sense.We established the theoretical model and simulatedthe key performances of the device with Ansoft HFSS.The results showed that the device exhibits a polarization-insensitivebehavior with a maximum amplitude modulation depth of 71% and a modulation rate of3.2Mbps at the resonance frequency of0.86 THz.

scholarly journals Planetary wave activity in the Arctic and Antarctic lower stratospheres during 2007 and 2008

2009 ◽  
Vol 9 (4) ◽  
pp. 14601-14643
Author(s):  
S. P. Alexander ◽  
M. G. Shepherd
Keyword(s):  
Northern Hemisphere ◽  
Planetary Wave ◽  
Travelling Waves ◽  
Maximum Amplitude ◽  
Wave Activity ◽  
Planetary Waves ◽  
The Arctic ◽  
Stationary Waves ◽  
Wave Amplification ◽  
Zonal Wavenumber

Abstract. Temperature data from the COSMIC GPS-RO satellite constellation are used to study planetary wave activity in both polar stratospheres from September 2006 until November 2008. One major and several minor sudden stratospheric warmings (SSWs) were recorded during the boreal winters of 2006/2007 and 2007/2008. Planetary wave morphology is studied using space-time spectral analysis while individual waves are extracted using a linear least squares fitting technique. Results show the planetary wave frequency and zonal wavenumber distribution varying between hemisphere and altitude. Most of the large Northern Hemisphere wave activity is associated with the winter SSWs, while the largest amplitude waves in the Southern Hemisphere occur during spring. Planetary wave activity during the 2006/2007 and 2007/2008 Arctic SSWs is due largely to travelling waves with zonal wavenumbers |s|=1 and |s|=2 having periods of 12, 16 and 23 days and stationary waves with |s|=1 and |s|=2. The latitudinal variation of wave amplification during the two Northern Hemisphere winters is studied. Most planetary waves show different structure and behaviour during each winter. Abrupt changes in the latitude of maximum amplitude of some planetary waves is observed co-incident in time with some of the SSWs.

Air Clearing Oscillation Produced by APR1400 Prototype Sparger

2002 ◽  
Author(s):  
Seok Cho ◽  
Choon-Kyung Park ◽  
Hwan-Yeol Kim ◽  
Se-Young Chun ◽  
Chul-Hwa Song ◽  
...  
Keyword(s):  
Maximum Amplitude ◽  
Considerable Effect ◽  
Operating Conditions ◽  
Positive Pressure ◽  
Pressure Amplitude ◽  
Tank Wall ◽  
Air Mass ◽  
Test Conditions ◽  
Valve Opening ◽  
Series Of Experiments

KAERI has performed a series of experiments to investigate the performance of APR1400 prototype sparger in view of the dynamic load oscillation with the variation of test conditions such as discharged air mass, submergence of the sparger, valve opening time, and pool temperature during the air-clearing phase. The air mass and pool temperature are in the range of 0.8 ∼ 1.5 kg and 20 ∼ 90°C, respectively. The valve opening time can be adjusted in the range of 0.6 ∼ 1.7 sec according to the POSRV operating conditions. The maximum positive pressure amplitude, which is observed at the bottom of the quench tank, is increased with the submergence depth and maximum header pressure of sparger. The valve opening time has a considerable effect on the maximum amplitude. As the opening time decreases, the maximum amplitudes at the tank wall are increased. Air mass and pool temperature, however, have a weak effect on the maximum amplitude. Oscillation frequency is decreased with air mass in the range of 2.5 ∼ 4.5Hz.

Impact Response Spectrum for Design of Ship-Bridge Collisions

2014 ◽  
Vol 587-589 ◽  
pp. 1547-1553 ◽  
Author(s):  
Jun Jie Wang ◽  
Zhi Ran Yu
Keyword(s):  
Impact Force ◽  
Response Spectrum ◽  
Degree Of Freedom ◽  
Impact Response ◽  
Amplification Effect ◽  
Spectrum Method ◽  
Time Histories ◽  
Dynamic Amplification ◽  
Force Time ◽  
The Impact

Due to the complexity involved and limited study on the topic, the equivalent static method, adopted in the current codes for structural design of bridges under ship collisions, does not take into account the dynamic amplification effect correctly. An accurate assessment of impact force based on refined numerical simulation is time consuming and is normally too complex for ordinary design procedure. Herein, with reference to the earthquake response spectrum method, an impact response spectrum method, which considers the dynamic amplification effect and is efficient for design, is proposed. Through refined numerical simulations of ship-rigid wall collisions, 81 impact force time histories associated with 9 typical ships under 9 velocities are obtained. The dynamic magnification factor (DMF) of single-degree-of-freedom (SDOF) systems with different periods and damping ratios experiencing the 81 impact force time histories are then studied. The relationship of DMF and period under different damping ratios, i.e. the DMF spectrum, is yielded by statistical analysis, based on which the impact response spectrum is obtained. Finally, the design combination method for multi-degree-of-freedom based on the impact response spectrum of SDOF is discussed for a continuous beam bridge.

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