scholarly journals Variability of the low-frequency acoustic response along leaf blades and between species of seagrass (Posidonia oceanica and Cymodocea nodosa)

2021 ◽  
Vol 1 (8) ◽  
pp. 080801
Author(s):  
Jay R. Johnson ◽  
Preston S. Wilson ◽  
Jean-Pierre Hermand
Keyword(s):  
Low Frequency ◽  
Posidonia Oceanica ◽  
Cymodocea Nodosa ◽  
Acoustic Response

On the Use of Transfer Approaches to Predict the Vibroacoustic Response of Poroelastic Media

2016 ◽  
Vol 24 (02) ◽  
pp. 1550020 ◽  
Author(s):  
Q. Serra ◽  
M. N. Ichchou ◽  
J.-F. Deü
Keyword(s):  
Transfer Matrix ◽  
High Frequency ◽  
Plane Waves ◽  
Finite Size ◽  
Low Frequency ◽  
Acoustic Response ◽  
Frequency Range ◽  
Finite Size Effects ◽  
Poroelastic Media ◽  
Lateral Boundary Conditions

The transfer matrix method (TMM) is a famous analytic method in the vibroacoustic community. It is classically considered as a high frequency approach, because of the hypothesis of acoustic plane waves impinging on a flat infinite panel. Thus, it cannot take into account directly finite-size effects or lateral boundary conditions (BCs), and it needs specific algorithms to correct its results in the low frequency range. Within the transfer matrix framework, the use of finite elements makes it possible to generalize the range of applications of transfer approaches. Thus, the study of wave propagation in poroelastic media, in presence of lateral BCs can be carried out. The links between theses waves and the acoustic response of a sample are investigated. Finally, it shows that transfer approaches are not limited in the low frequency range, as usually stated. In fact, the validity of analytic transfer approaches depends more on the material and on the geometry than on the frequency range.

scholarly journals A Comparison of Abundance and Diversity of Epiphytic Microalgal Assemblages on the Leaves of the SeagrassesPosidonia oceanica(L.) andCymodocea nodosa(Ucria) Asch in Eastern Tunisia

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Lotfi Mabrouk ◽  
Mounir Ben Brahim ◽  
Asma Hamza ◽  
Mabrouka Mahfoudhi ◽  
Med Najmeddine Bradai
Keyword(s):  
Growth Rate ◽  
Species Composition ◽  
Posidonia Oceanica ◽  
Cymodocea Nodosa ◽  
Seagrass Species ◽  
Light Penetration ◽  
Grazing Effect ◽  
Abundance And Diversity ◽  
Fast Growing Species ◽  
Host Characteristics

We studied spatial patterns in assemblages of epiphytic microalgae on the leaves of two seagrass species with different morphologies and longevity,Cymodocea nodosaandPosidonia oceanica, which cooccur in Chebba in Eastern Tunisia. Epiphyte assemblages were described for each species in summer. Epiphyte microalgal assemblages were more abundant on the leaves ofC. nodosabut more diversified on the leaves ofP. oceanica. We suggest that the differences in species composition and abundance between those seagrass species may reflect an interaction of timescales of seagrass longevity with timescales of algal reproductive biology. Short-livedC. nodosawas dominated by fast growing species such as the cyanobacteria speciesOscillatoriasp., whileP. oceanicaleaves were colonized by more mature and diversified species such as Prorocentrales. Local environmental conditions (hydrodynamics, light penetration), host characteristics (meadow type, shapes forms of leaves, life span, and growth rate), and grazing effect seem also to be responsible for these dissimilarities in epiphytic microalgae communities.

scholarly journals Two-dimensional resonators with small openings

1982 ◽  
Vol 24 (1) ◽  
pp. 2-27 ◽  
Author(s):  
G. R. Bigg ◽  
E. O. Tuck
Keyword(s):  
Natural Frequency ◽  
Asymptotic Expansions ◽  
Velocity Potential ◽  
Low Frequency ◽  
Matched Asymptotic Expansions ◽  
Two Dimensional ◽  
Acoustic Response ◽  
Closed Cavity ◽  
Small Opening

AbstractThe acoustic response of a two-dimensional nearly-closed cavity to an excitation through a small opening is examined, using the method of matched asymptotic expansions. The Helmholtz mode of vibration is discussed using a low-frequency expansion of the velocity potential in the cavity interior. The variation in frequency and magnitude of the resonator response is explored, both for the Helmholtz and the natural-frequency modes.

LOW FREQUENCY ACOUSTIC RESPONSE OF SURFACE CRACKS BY ATOM FORCE ACOUSTIC MICROSCOPY

2009 ◽  
Vol 16 (03) ◽  
pp. 449-453 ◽  
Author(s):  
WEI-TAO SU ◽  
BIN LI ◽  
DING-QUAN LIU ◽  
FENG-SHAN ZHANG
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Thermal Stress ◽  
Elastic Properties ◽  
Surface Crack ◽  
Low Frequency ◽  
Acoustic Microscopy ◽  
Surface Cracks ◽  
Acoustic Response ◽  
Scanning Electron

Surface crack of CeF 3 films generated by thermal stress were characterized by scanning electron microscopy and atom force acoustic microscopy (AFAM). Low frequency (8–18 kHz) acoustic response of films and cracks was measured by AFAM. The low frequency acoustic response is similar to what had been got at several MHz or even higher frequency. It was found that surface elastic properties of CeF 3 films can be easily qualitatively measured by low frequency AFAM.

Sign in / Sign up

Export Citation Format

Share Document