نتایج جستجو برای: baryonic acoustic waves

تعداد نتایج: 194964  

2012
J. R. Heinrich S.-H. Kim J. K. Meyer R. L. Merlino M. Rosenberg

Secondary dust density waves were observed in conjunction with high amplitude ðnd=nd0 > 2Þ dust acoustic waves (DAW) that were spontaneously excited in a dc glow discharge dusty plasma in the moderately coupled, C 1; state. The high amplitude dust acoustic waves produced large dust particle oscillations, displacements, and trapping. Secondary dust density waves were excited in the wave troughs ...

2015
Usama Kadri

The propagation of wave disturbances in water of uniform depth is discussed, accounting for both gravity and compressibility effects. In the linear theory, free-surface (gravity) waves are virtually decoupled from acoustic (compression) waves, as the sound speed in water far exceeds the maximum gravity wave phase speed. However, these two types of wave motion could exchange energy via resonant ...

2009
Robert L. Merlino

A historical overview of some of the early theoretical and experimental work on dust acoustic waves is given. The basic physics of the dust acoustic wave and some of the theoretical refinements that have been made, including the effects of collisions, plasma absorption, dust charge fluctuations, particle drifts and strong coupling effects are discussed. Some recent experimental findings and out...

1998
DAVID COLTON

This paper is a survey of the inverse scattering problem for time-harmonic acoustic and electromagnetic waves at fixed frequency. We begin by a discussion of “weak scattering” and Newton-type methods for solving the inverse scattering problem for acoustic waves, including a brief discussion of Tikhonov’s method for the numerical solution of ill-posed problems. We then proceed to prove a uniquen...

2009
Edward Thomas

In dc glow discharge dusty plasmas, the formation of dust acoustic waves is a commonly observed phenomenon. Experiments in the dusty plasma experiment device produce naturally occurring dust acoustic waves with frequencies f N 5 to 25 Hz and phase velocities of Vph N 0.5 to 10 cm/s. Through the use of particle image velocimetry techniques, particle motion in the vicinity of the wavefronts is id...

2013
Martin Schmitt Sergei Olfert Jens Rautenberg Gerhard Lindner Bernd Henning Leonhard M. Reindl

Recently, an acoustic waveguide sensor based on multiple mode conversion of surface acoustic waves at the solid-liquid interfaces has been introduced for the concentration measurement of binary and ternary mixtures, liquid level sensing, investigation of spatial inhomogenities or bubble detection. In this contribution the sound wave propagation within this acoustic waveguide sensor is visualize...

2007
R. Skartlien

The excitation of acoustic waves is studied using 3D numerical simulations of the non-magnetic solar atmosphere and the upper convection zone. Transient acoustic waves in the atmosphere are excited at the top of the convective zone (the cooling layer) and immediately above in the convective overshoot zone, by small granules that undergo a rapid collapse, in the sense that upflow reverses to dow...

2005
Hee-Jong Seo Daniel J. Eisenstein

Baryonic acoustic oscillations imprinted in the galaxy power spectrum provide a promising tool for probing the cosmological distance scale and dark energy. We present results from a suite of cosmological N-body simulations aimed at investigating possible systematic errors in the recovery of cosmological distances. We show the robustness of baryonic peaks against nonlinearity, redshift distortio...

2001
Sjoerd W. Rienstra

For the relatively high frequencies relevant in a turbofan engine duct, the modes of a lined section may be classified in two categories: genuine acoustic 3D duct modes resulting from the finiteness of the duct geometry, and 2D surface waves that exist only near the wall surface in a way essentially independent of the rest of the duct. Per frequency and circumferential order there are at most f...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه صنعتی امیرکبیر(پلی تکنیک تهران) - دانشکده مهندسی مکانیک 1384

آکوستیک امیشن می تواند به عنوان یک روش تست غیر مخرب در شناسایی نشت سیال مورد استفاده قرار گیرد. در این تحقیق تاثیر پارامترهای نشت بر روی سیگنال های اکوستیک امیشن با طراحی و بکارگیری سیستم آزمایشگاهی که توانایی ایجاد نشت کنترل شده در یک خط لوله را دارا می باشد بررسی گردید. خط لوله ای که امکان نصب نازل های مختلف نشت بر روی آن فراهم گردیده است توسط کمپرسور، تحت فشارهای مختلف قرار می گرفت و در هر ف...

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