Thematische Bibliographien / Acoustic wave control in water

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Auswahl der wissenschaftlichen Literatur zum Thema „Acoustic wave control in water“

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Veröffentlicht am 1. Februar 2025

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Zeitschriftenartikel zum Thema "Acoustic wave control in water"

Norris, Andrew, Alexey S. Titovich und Michael Haberman. „Acoustic wave control with cylindrical metamaterial elements in water“. Journal of the Acoustical Society of America 138, Nr. 3 (September 2015): 1733. http://dx.doi.org/10.1121/1.4933459.

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SISOMBAT, Félix, Thibaut DEVAUX, Samuel CALLé und Lionel HAUMESSER. „Acoustic reflector remotely tunable by the acoustic radiation force“. INTER-NOISE and NOISE-CON Congress and Conference Proceedings 270, Nr. 4 (04.10.2024): 7893–98. http://dx.doi.org/10.3397/in_2024_4019.

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Specifically structured surface can be used to control acoustic waves reflection enabling wavefront shaping tailored for desired applications such as imaging or cloaking. With the development of metasurfaces, which enable changing the reflection of an incident acoustic wave at an interface using a sub-wavelength structure, it is possible to explore new frontiers of Snell-Descartes laws. However, the control over wave propagation is pre-established when using fixed structures, directing research towards metasurfaces reconfigurable in both time and space. This work proposes a metamaterial architecture using deformations of a fluid interface between two media through the acoustic radiation pressure (ARP). An analytical and numerical study is conducted to assess the phase shift on airborne acoustic wave induced by a unit cell featuring a Helmholtz resonator tuned by the water surface elevation induced by ARP. The possibility to program in real-time the phase shift is successfully tested experimentally for an incident wave of frequency 3400 Hz. The extension to a metasurface is introduced through the juxtaposition of 15 unit cell. A retroreflection effect is then numerically demonstrated, highlighting the effectiveness of the proposed approach. This concept of real-time and non-contact reconfigurable metasurface opens new possibilities for beam deflection, acoustic holography or information encoding.

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He, Jiahuan, Wei Zhang, Dan Zhao, Nong Li, Qiang Kang, Kunpeng Cai, Li Wang et al. „Numerical Simulation Analysis of Control Factors on Acoustic Velocity in Carbonate Reservoirs“. Minerals 14, Nr. 4 (19.04.2024): 421. http://dx.doi.org/10.3390/min14040421.

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The conventional Archie formula struggles with the interpretation of water saturation from resistivity well log data due to the increasing complexity of exploration targets. This challenge has prompted researchers to explore alternative physical parameters, such as acoustic characteristics, for breakthroughs. Clarifying the influencing factors of porous media acoustic characteristics is one of the most important approaches to help understanding the mechanism of acoustic characteristics of carbonate reservoirs. The article uses digital rock technology to characterize the pore structure, quantitatively identify fractures and pore structures in carbonate rocks, and establish digital models. Through conventional acoustic testing, the pressure wave (P-wave) and shear wave (S-wave) velocities of rock samples at different water saturations are obtained, and the dynamic elastic modulus is calculated. A finite element calculation model is established using the digital rock computational model to provide a basis for fluid saturation calculation methods. Based on real digital rock models, different combinations of virtual fractures are constructed, and factors affecting acoustic parameters are analyzed. The study finds that as porosity increases, the velocity difference between porous cores and fractured cores also increases. These findings provide important technical support and a theoretical basis for interpreting acoustic well logging data and evaluating carbonate reservoirs with different pore and fracture types.

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Kos̆tial, Pavol. „Surface acoustic wave control of the ion concentration in water“. Applied Acoustics 41, Nr. 2 (1994): 187–93. http://dx.doi.org/10.1016/0003-682x(94)90068-x.

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Kozaczka, Eugeniusz, Jacek Domagalski, Grażyna Grelowska und Ignacy Gloza. „Identification of hydro-acoustic waves emitted from floating units during mooring tests“. Polish Maritime Research 14, Nr. 4 (01.10.2007): 40–46. http://dx.doi.org/10.2478/v10012-007-0038-5.

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Identification of hydro-acoustic waves emitted from floating units during mooring tests Measurements of hydro-acoustic noise emitted from vessels are a.o. a subject of the tests carried out in the control measurement ranges of the Navy. The measurements are performed both on anchored and floating vessels. Acoustic field of vessels is changing along with their speed changing and is associated with acoustic activity of wave sources installed in vessel's hull (main engines, electric generating sets, reduction gears, pumps, shaft-lines, piping, ventilating ducts etc) as well as hydro-dynamic sources such as screw propellers and water flow around the hull [5, 7]. Vibration energy generated by the onboard devices is transferred through ship structural elements to water where it propagates in the form of hydro-acoustic waves of a wide frequency band.

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Anisimkin, Vladimir, Vladimir Kolesov, Anastasia Kuznetsova, Elizaveta Shamsutdinova und Iren Kuznetsova. „An Analysis of the Water-to-Ice Phase Transition Using Acoustic Plate Waves“. Sensors 21, Nr. 3 (29.01.2021): 919. http://dx.doi.org/10.3390/s21030919.

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It is shown that, in spite of the wave radiation into the adjacent liquid, a large group of Lamb waves are able to propagate along piezoelectric plates (quartz, LiNbO3, LiTaO3) coated with a liquid layer (distilled water H2O). When the layer freezes, most of the group’s waves increase their losses, essentially forming an acoustic response towards water-to-ice transformation. Partial contributions to the responses originating from wave propagation, electro-mechanical transduction, and wave scattering were estimated and compared with the coupling constants, and the vertical displacements of the waves were calculated numerically at the water–plate and ice–plate interfaces. The maximum values of the responses (20–30 dB at 10–100 MHz) are attributed to the total water-to-ice transformation. Time variations in the responses at intermediate temperatures were interpreted in terms of a two-phase system containing both water and ice simultaneously. The results of the paper may turn out to be useful for some applications where the control of ice formation is an important problem (aircraft wings, ship bodies, car roads, etc.).

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Li, Qi, Ke Wu und Mingquan Zhang. „Two-Dimensional Composite Acoustic Metamaterials of Rectangular Unit Cell from Pentamode to Band Gap“. Crystals 11, Nr. 12 (25.11.2021): 1457. http://dx.doi.org/10.3390/cryst11121457.

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Pentamode metamaterials have been receiving an increasing amount of interest due to their water-like properties. In this paper, a two-dimensional composite pentamode metamaterial of rectangular unit cell is proposed. The unit cells can be classified into two groups, one with uniform arms and the other with non-uniform arms. Phononic band structures of the unit cells were calculated to derive their properties. The unit cells can be pentamode metamaterials that permit acoustic wave travelling or have a total band gap that impedes acoustic wave propagation by varying the structures. The influences of geometric parameters and materials of the composed elements on the effective velocities and anisotropy were analyzed. The metamaterials can be used for acoustic wave control under water. Simulations of materials with different unit cells were conducted to verify the calculated properties of the unit cells. The research provides theoretical support for applications of the pentamode metamaterials.

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Knight, Rosemary, Jack Dvorkin und Amos Nur. „Acoustic signatures of partial saturation“. GEOPHYSICS 63, Nr. 1 (Januar 1998): 132–38. http://dx.doi.org/10.1190/1.1444305.

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The relationship between elastic wave velocities and water saturation in a water/gas reservoir depends strongly on whether saturation is heterogeneous (patchy) or homogeneous. Heterogeneity in saturation may result from lithologic heterogeneity because under conditions of capillary equilibrium, different lithologies within a reservoir can have different saturations, depending on their porosities and permeabilities. We investigate this phenomenon by generating models of a reservoir in which we control the distribution of lithologic units and theoretically determine the corresponding velocity‐saturation relationship. We assume a state of capillary equilibrium in the reservoir and determine the saturation level of each region within the reservoir from the corresponding capillary pressure curve for the lithologic unit at that location. The velocities we calculate for these models show that saturation heterogeneity, caused by lithologic variation, can lead to a distinct dependence of velocity on saturation. In a water‐gas saturated reservoir, a patchy distribution of the different lithologic units is found to cause P-wave velocity to exhibit a noticeable and almost continuous velocity variation across the entire saturation range. This is in distinct contrast to the response of a homogeneous reservoir where there is only a large change in velocity at water saturations close to 100%.

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Memon, Maria Muzamil, Qiong Liu, Ali Manthar, Tao Wang und Wanli Zhang. „Surface Acoustic Wave Humidity Sensor: A Review“. Micromachines 14, Nr. 5 (27.04.2023): 945. http://dx.doi.org/10.3390/mi14050945.

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The Growing demands for humidity detection in commercial and industrial applications led to the rapid development of humidity sensors based on different techniques. Surface acoustic wave (SAW) technology is one of these methods that has been found to provide a powerful platform for humidity sensing owing to its intrinsic features, including small size, high sensitivity, and simple operational mechanism. Similar to other techniques, the principle of humidity sensing in SAW devices is also realized by an overlaid sensitive film, which serves as the core element whose interaction with water molecules is responsible for overall performance. Therefore, most researchers are focused on exploring different sensing materials to achieve optimum performance characteristics. This article reviews sensing materials used to develop SAW humidity sensors and their responses based on theoretical aspects and experimental outcomes. Herein the influence of overlaid sensing film on the performance parameters of the SAW device, such as quality factor, signal amplitude, insertion loss, etc., is also highlighted. Lastly, a recommendation to minimize the significant change in device characteristics is presented, which we believe will be a good step for the future development of SAW humidity sensors.

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M’zoughi, Fares, Izaskun Garrido, Aitor J. Garrido und Manuel De La Sen. „Rotational Speed Control Using ANN-Based MPPT for OWC Based on Surface Elevation Measurements“. Applied Sciences 10, Nr. 24 (16.12.2020): 8975. http://dx.doi.org/10.3390/app10248975.

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This paper presents an ANN-based rotational speed control to avoid the stalling behavior in Oscillating Water Columns composed of a Doubly Fed Induction Generator driven by a Wells turbine. This control strategy uses rotational speed reference provided by an ANN-based Maximum Power Point Tracking. The ANN-based MPPT predicts the optimal rotational speed reference from wave amplitude and period. The neural network has been trained and uses wave surface elevation measurements gathered by an acoustic Doppler current profiler. The implemented ANN-based rotational speed control has been tested with two different wave conditions and results prove the effectiveness of avoiding the stall effect which improved the power generation.

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Dissertationen zum Thema "Acoustic wave control in water"

Kourchi, Hasna. „Μétaréseaux pοur la réflexiοn et la transmissiοn anοrmales de frοnts d’οnde acοustique dans l’eau“. Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMLH36.

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Un métaréseau est un assemblage périodique de diffuseurs conçu pour réfléchir ou réfracter une onde vers une direction anormale, non prévue par les lois de Snell-Descartes. Dans ce travail, nous avons conçu, fabriqué et caractérisé expérimentalement de tels métaréseaux pour le contrôle des ondes ultrasonores dans l’eau, en utilisant des tubes et des cylindres en laiton ainsi que des supports plastiques imprimés en 3D. Ces métaréseaux permettent de rediriger un front d'onde incident vers une direction arbitraire souhaitée, avec une efficacité élevée (proche de 100 %), aussi bien en réflexion sur une surface (comme l’interface eau/air) qu'en transmission. L’approche théorique repose sur les principes de la diffraction de Bragg et sur les interactions constructives et destructives des ondes. Les résultats de cette thèse démontrent l'efficacité des métaréseaux à induire des phénomènes acoustiques tels que la rétro-réflexion et la réponse asymétrique, grâce à l’utilisation de structures résonantes et non résonantes, validées par des simulations par éléments finis et des expérimentations. Cette recherche ouvre de nouvelles perspectives pour la manipulation des ondes acoustiques sous-marines, avec des applications potentielles dans les domaines de la détection, de l'absorption et de la réflexion des ondes en milieu marin
A metagrating is a periodic assembly of scatterers designed to reflect or refract a wave toward an anomalous direction, not predicted by Snell's law. In this work, we designed, fabricated, and experimentally characterized such metagratings for the control of ultrasonic waves in water, using brass tubes and cylinders as well as 3D-printed plastic supports. These metagratings enable the redirection of an incident wavefront to an arbitrarily desired direction with high efficiency (close to 100%), both in reflection on a surface (e.g., the water/air interface) and in transmission. The theoretical approach is based on the principles of Bragg diffraction and constructive and destructive wave interactions. The results of this thesis demonstrate the efficiency of metagratings in inducing acoustic phenomena such as retroreflection and asymmetric wave response, achieved through the use of resonant and non-resonant structures, validated by finite element simulations and experiments. This research opens new perspectives for the manipulation of underwater acoustic waves, with potential applications in the fields of wave detection, absorption, and reflection in marine environments

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Awodele, M. Kofoworola. „Control of charge transports in semiconductor superlattices using an acoustic wave“. Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16738.

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In this work, we describe the electron dynamics in semiconductor superlattices (SLs) when driven by an acoustic wave. First, we discuss the physical features and structure of SLs. Then we describe semiclassical transport in periodic potential driven by a plane wave, and the dynamics of ultracold atoms in the periodic potentials. Secondly, we explore single electron dynamics in superlattices driven by an acoustic wave, then present and analyse the types of electron trajectories according to the strength of the acoustic wave amplitude. The two dynamical regimes obtained depend on the wave amplitude strength and the initial position of electrons in the acoustic wave. The frequency range of the oscillation produced can be as large as terahertz. Lastly, we discuss the effect of applying a static electric field to the acoustically driven SLs. When the acoustic wave and electric fields were applied together along the axis of SLs, we obtained a higher peak drift velocity than when the acoustic wave or electric fields were applied alone. We use the phase portrait to explain the electron trajectory and the path of the electrons. The global state associated with the drastic change in the drift velocity of the electrons depends on the varied parameters in the dynamical systems. We numerically calculate the electron trajectories while we varied the strength of electric field and wave amplitude to investigate the role of interactions in the system. When very high electric field and very high wave amplitude are applied together along the axis of SL, global catastrophe occurs. This is the discontinuous bifurcation in dynamical system.

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Turnbull, Katharine Frances Vogan. „A surface acoustic wave frost point hygrometer for measurements of atmospheric water vapour“. Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619580.

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葉子良 und Tsz-leung Yip. „Active water-wave control by a submerged pitching plate“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31237976.

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Yip, Tsz-leung. „Active water-wave control by a submerged pitching plate /“. Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19003067.

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Eden, L. „Measurements of atmospheric water vapour using a balloon-borne surface acoustic wave frost point hygrometer“. Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598746.

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A frost point hygrometer is described in this thesis which uses surface acoustic waves (SAWs) to detect water vapour condensation. The SAW device crystal is cooled by a thermoelectric cooler until condensation occurs, at which point, water vapour loading onto the SAW device causes changes in the SAW velocity and amplitude. Two methods of determining the frost point temperature are outlined in this thesis. The first uses a feedback loop algorithm to maintain a constant amount of water vapour on the SAW device and hence keep the temperature of the device at the frost point. The second uses heating and cooling cycles to oscillate the SAW device temperature above and below the frost paint. Changes in the SAW properties are then used to detect the condensation-evaporation equilibrium point which is equal to the frost point. The use of SAWs rather than a conventional optical detection system in this hygrometer allows a faster response time, increased sensitivity, and decreased risk of contamination. Between September 2001 and February 2004, the SAW hygrometer was flown on 28 balloon flights, in various configurations. All of these flight data sets show agreement with radiosonde relative humidity measurements to within 1%, using given criteria for extraction of reliable SAW hygrometer measurements. Accurate lower and mid tropospheric measurements have been made on each flight and four flights show accurate upper tropospheric and lower stratospheric measurements with water vapour mixing ratio values of less than 5 ppmv. The Hibiscus campaign flights in Bauru, Brazil, show excellent agreement between the different instruments measuring water vapour on the flight train and the SAW hygrometer. These data are discussed in conjunction with auxiliary data and model backward trajectories. Two different backward trajectory models have been used to assess the possible mechanisms of transport of water vapour above Bauru, one of which is a large scale model and the other is a meso-scale model. A sharp contrast in the air parcel transport above and below the tropical tropopause layer (TTL) is seen, with large scale convection or descent controlling the water vapour mixing ratios below the TTL, and a combination of large and small scale fields controlling the water vapour in and above the TTL.

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Chen, Feng. „Effect of mesoscale variability of water masses on acoustic wave propagation in a shallow sea“. Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3219.

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Anthropogenic noise in the sea is now classed as a pollutant alongside chemical pollution and marine litter in accordance with the Marine Strategy Framework Directive. Noise from shipping is a major contributor to the ambient noise levels in the ocean, particularly at low (<300Hz) frequencies. The properties of sound propagation in shallow waters are highly influenced by the marine physical environment. Ocean modelling plays an important role in underwater noise studies since it can provide high resolution water column parameters over large geographic areas. This study investigates the noise patterns and their temporal variations in the Celtic Sea by using a coupled ocean model (POLCOMS) and an acoustic model (HARCAM). A method to predict noise exposure experienced by marine animals is then developed, following an application for diving seals. The ocean model is applied in the Celtic Sea to provide high-resolution 3D hourly temperature and salinity fields for the acoustic model. The model is validated against in-situ and satellite observations, giving high skills to simulate the water column structures. Sensitivity studies of modelled results to different atmospheric forcing are carried out in order to improve the accuracy of the model. The results show that the modelled sea surface temperature, stratification and water column structures are highly sensitive to the choice of surface forcing, especially in the summer time. The increase in resolution of surface forcing does not necessarily lead to more accurate results. The tidally frontal position is, however, insensitive to the forcing. The variability of noise propagation is studied using the coupled model, demonstrating high dependence on oceanographic conditions, geographic location of sound source and its depth. In summer, when the source of sound is on the inshore side of the bottom front, the sound energy is mostly concentrated in the near-bottom layer. In winter, the sound from the same source is distributed more evenly in the vertical. When the source is on the seaward side of the front, the sound level from a shallow source is nearly uniform in the vertical and the transmission loss is significantly greater (~16dB at 40km distance) in summer than in winter. In contrast, sound energy from a deep source is trapped in the bottom cold water, leading to a much lower transmission loss (~20dB) in summer than in winter. Note that ~10dB fluctuation of sound energy is found during the deterioration of the thermocline in late autumn. Shallow sources (e.g. ships) are sensitive to the surface heat flux as it changes significantly the vertical temperature gradient, while tides play an important role in determining the TL variability of deeper sources (e.g. pile driving) since they cause adjustments of positions of subsurface fronts. The seasonal noise patterns radiated by a large cargo ship are modelled by relating the AIS ship track data and the coupled model, showing a clear influence of the seasonal thermocline and associated bottom fronts on shipping noise distribution. The noise propagates much further (tens of kilometres) in winter than in summer. The predicted shipping noise exposure perceived by grey seals shows strong step changes in the sound level during their descent/ascent through the water column. Since grey seals tend to be benthic foragers, a hypothesis that the step change in sound exposure may have negative impacts on their foraging behaviour is proposed for biological specialists.

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Buck, John R. (John Richard). „Single mode excitation in the shallow water acoustic channel using feedback control“. Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40604.

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López, Ríos Juan Carlos. „Water-wave equations and free boundary problems: inverse problems and control“. Tesis, Universidad de Chile, 2015. http://repositorio.uchile.cl/handle/2250/135179.

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Doctor en Ciencias de la Ingeniería, Mención Modelación Matemática
En este trabajo se aborda el problema de existencia de algunos tipos de soluciones para las ecuaciones de ondas en el agua así como la relación que existe entre estas soluciones y la forma de un fondo impermeable sobre la que se desliza el fluido. Empezamos por describir las ecuaciones que modelan el fenómeno físico a partir de las leyes de conservación; el modelo general de las ecuaciones de ondas en el agua, escrito para la restricción de la velocidad potencial a la superficie libre, es \begin{equation*} \left\{ \begin{aligned} &\partial_t\zeta-G(\zeta,b)\psi=0, \\ &\partial_t\psi+g\zeta+\frac{1}{2}|\nabla_X\psi|^2-\frac{1}{2(1+|\nabla_X\zeta|^2)}(G(\zeta,b)\psi+\nabla_X\zeta\cdot\nabla_X\psi)^2=0, \end{aligned} \right. \end{equation*} donde $G=G(\zeta,b)\psi$ es el operador Dirichlet-Neumann, el cual contiene la información del fondo $b$, \begin{equation*} G(\zeta,b)\psi:=-\sqrt{1+|\nabla_X\zeta|^2}\partial_n\phi|_{y=\zeta(t,X)}, \end{equation*} y \begin{equation*} \left\{ \begin{array}{rl} & \Delta\phi=0, \quad \R\times(b,\zeta), \\ & \phi|_{y=\zeta}=\psi, \quad \partial_n \phi|_{y=b(X)}=0. \end{array} \right. \end{equation*} Después de describir las condiciones para un teorema de existencia y unicidad de soluciones de las ecuaciones de ondas en el agua, en espacios de Sobolev, nos preguntamos sobre el mínimo de datos necesarios, sobre la superficie libre, para identificar el fondo de manera única. Por la relación que existe entre el operador Dirichlet-Neumann y la velocidad dentro del fluido y utilizando la propiedad de continuación única de las funciones armónicas hemos probado que basta conocer el perfil, la velocidad potencial y la velocidad normal en un instante de tiempo dado y un abierto de $\R$, aún cuando nuestro sistema es de evolución. En la segunda parte se estudia la existencia de soluciones en forma de salto hidráulico para las ecuaciones estacionarias de ondas en el agua, en dimensión dos y su relación con la velocidad aguas arriba, caracterizada por un parámetro adimensional, llamado el número de Froude, $F$, como consecuencia de la existencia de ramas de bifurcación de la solución trivial para el problema \begin{equation*} \mathcal{F}(\eta,F)=\eta+F\widetilde{\psi}_{y^{\prime }}+\frac{\epsilon}{2}(% \widetilde{\psi}_{x^{\prime }}^2+\widetilde{\psi}_{y^{\prime }}^2)-\epsilon^2\eta_x\widetilde{\psi}_{x^{\prime }}\widetilde{\psi}% _{y^{\prime }}+\frac{\epsilon^3}{2}\eta_x^2\widetilde{\psi}_{y^{\prime }}^2; \end{equation*} donde \begin{equation*} \left\{ \begin{aligned} &\Delta\widetilde{\psi}=\epsilon G, && (-L,L)\times(0,1), \\ &\widetilde{\psi}_{x'}=0, && x'=-L,L, \\ &\widetilde{\psi}=0, && y'=0, \\ &\widetilde{\psi}=-F\eta, && y'=1. \end{aligned} \right. \end{equation*}

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Dungan, Mary Elizabeth. „Development of a compact sound source for the active control of turbofan inlet noise /“. This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03302010-020615/.

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Bücher zum Thema "Acoustic wave control in water"

Reddy, J. N. Water absorption studies on polymer coated piezoelectriccrystaland surface acoustic wave devices. Manchester: UMIST, 1994.

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United States. Environmental Protection Agency. Office of Water, Hrsg. WAVE, water management for the 21st century. [Washington, DC]: U.S. Environmental Protection Agency, Office of Water, 1999.

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Headrick, Robert Hugh. Analysis of Internal Wave induced mode coupling effects on the 1995 SWARM experiment acoustic transmissions. Springfield, Va: Available from National Technical Information Service, 1997.

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Buck, John R. Single mode excitation in the shallow water acoustic channel using feedback control. Woods Hole, Mass: Woods Hole Oceanographic Institution, 1996.

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Frisk, George V. Report on the Office of Naval Research Shallow Water Acoustics Workshop: April 24-26, 1991. Woods Hole, Mass: Woods Hole Oceanographic Institution, 1992.

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Ahrens, John. Irregular wave overtopping of seawall/revetment configurations, Roughans Point, Massachusetts: Experimental model study. [Vicksburg, Miss: U.S. Army Engineer Waterways Experiment Station, 1986.

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Zhou, Xiaoming, und Gengkai Hu. Acoustic Metamaterials and Wave Control. World Scientific Publishing Co Pte Ltd, 2018.

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Korde, Umesh A., und John V. Ringwood. Hydrodynamic Control of Wave Energy Devices. Cambridge University Press, 2016.

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Ringwood, John, und Umesh A. Korde. Hydrodynamic Control of Wave Energy Devices. Cambridge University Press, 2016.

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Buchteile zum Thema "Acoustic wave control in water"

Stone, Austen, Timothy Waters und Jennifer Muggleton. „Focussing Acoustic Waves with Intent to Control Biofouling in Water Pipes“. In Mechanisms and Machine Science, 1059–68. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-15758-5_109.

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Lin, Hejie, Turgay Bengisu und Zissimos P. Mourelatos. „Derivation of Acoustic Wave Equation“. In Lecture Notes on Acoustics and Noise Control, 27–48. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-88213-6_2.

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Lin, Hejie, Turgay Bengisu und Zissimos P. Mourelatos. „Solutions of Acoustic Wave Equation“. In Lecture Notes on Acoustics and Noise Control, 49–79. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-88213-6_3.

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Nayfeh, Adnan H. „Acoustic Wave Reflection from Water/Laminated Composite Interfaces“. In Review of Progress in Quantitative Nondestructive Evaluation, 1119–28. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4613-1893-4_128.

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Kurosawa, Minoru Kuribayashi. „Surface Acoustic Wave Motor Modeling and Motion Control“. In Next-Generation Actuators Leading Breakthroughs, 7–18. London: Springer London, 2010. http://dx.doi.org/10.1007/978-1-84882-991-6_2.

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Hoskin, R. E., B. M. Count, N. K. Nichols und D. A. C. Nicol. „Phase Control for the Oscillating Water Column“. In Hydrodynamics of Ocean Wave-Energy Utilization, 257–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-82666-5_22.

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Rajan, Subramaniam D., und George V. Frisk. „The Effect of Seasonal Temperature Fluctuations in the Water Column on Sediment Compressional Wave Speed Profiles in Shallow Water“. In Ocean Variability & Acoustic Propagation, 69–80. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3312-8_5.

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Uscinski, B. J. „Acoustic Scattering in Wave-Covered Shallow Water. The Coherent Field“. In Impact of Littoral Environmental Variability of Acoustic Predictions and Sonar Performance, 329–36. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0626-2_41.

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Volkov, Grigory A., Aleksey A. Gruzdkov und Yuri V. Petrov. „A Randomized Approach to Estimate Acoustic Strength of Water“. In Mechanics and Control of Solids and Structures, 633–40. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-93076-9_30.

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Santiago, J. A. F., und L. C. Wrobel. „Boundary Element Method for Two-Dimensional Shallow Water Acoustic Wave Propagation“. In IUTAM/IACM/IABEM Symposium on Advanced Mathematical and Computational Mechanics Aspects of the Boundary Element Method, 281–92. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-015-9793-7_24.

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Konferenzberichte zum Thema "Acoustic wave control in water"

Yun, Gu Qiu, Hu HaoHao, Wang Biao, Zhu RuiQi, Wang Kang und Zuo Wang. „Vibro-Acoustic Characteristics of Ribbed Cylindrical Shells in Shallow Water Based on Wave Superposition“. In 2024 OES China Ocean Acoustics (COA), 1–8. IEEE, 2024. http://dx.doi.org/10.1109/coa58979.2024.10723699.

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Mokhtari, Alireza, und Vijay Chatoorgoon. „Study of Wall Thickness and Material Effect on Acoustic Wave Propagation in Water-Filled Piping“. In ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ncad2012-1131.

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The operation of many industries, such as power plants or many piping systems, demands knowledge of generated pressure pulsations. The effect of acoustic wave amplification in piping systems can be detrimental to the integrity and life of whole plant. Therefore, understanding of the nature of acoustic wave propagation in water filled piping systems needs to be established based on fundamental experiments and analysis. Chatoorgoon et al. [1] and Rzentkowski et al. [2], compared their no flow experiments with theoretical calculation, and realized that the resonant frequency shifts increased linearly, with resonant frequency increasing. This paper presents an experimental study showing that linear wave theory, based on a transmission matrix method does predict well the acoustic resonance frequency from 50 to 500 Hz. and the resonant frequency shifts were negligible. Study of tube wall thickness, material (stainless steel and Aluminum) and some equal branch configurations for “Closed-end” tubes are discussed.

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Bender, Florian, Fabien Josse, Rachel E. Mohler und Antonio J. Ricco. „Design of SH-surface acoustic wave sensors for detection of ppb concentrations of BTEX in water“. In 2013 Joint European Frequency and Time Forum & International Frequency Control Symposium (EFTF/IFC). IEEE, 2013. http://dx.doi.org/10.1109/eftf-ifc.2013.6702067.

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Sracic, Michael W., Jordan D. Petrie, Henry A. Moroder, Ryan T. Koniecko, Andrew R. Abramczyk und Kamlesh Suthar. „Acoustic Pressure Fields Generated With a High Frequency Acoustic Levitator“. In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71849.

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Acoustic levitation is an advantageous particle positioning mechanism currently employed for applications of x-ray spectroscopy and micro-material manufacturing[1], [2]. By levitating a particle using only acoustic pressure waves, one eliminates the need for a container or other physical structure which may contaminate the specimen. Unfortunately, the pressure field generated by a standing acoustic wave is susceptible to periodic instabilities, and a particle that is levitated in this field tends to vibrate. The amplitude of the vibration is largest in the directions that are orthogonal to the axis in which the acoustic wave is generated. Therefore, by generating additional acoustic waves in each orthogonal axis, the vibration amplitude of the levitated particle is significantly reduced. The authors have shown this phenomenon to be true in a previous study[3]. In this paper, the authors explore the details of the pressure field that is generated with the device. A single degree-of-freedom relationship is developed between the acoustic field pressure, the location of the levitated particle, and the mechanical vibration needed to produce levitation. In order to levitate a 100 micrometer diameter water droplet at 55 kilohertz, the calculations suggest that the transducer must achieve an average surface vibration amplitude of at least 6.43 micrometers. This mechanical vibration must produce a root means-squared pressure amplitude of 933 Pascal. Under these conditions, the particle will levitate approximately 0.4 millimeters below a zero pressure node. To validate the use of the single degree of freedom relationships and to explore the acoustic field for one, two, and three-axis levitation, the authors designed and prototyped an acoustic levitator capable of generating standing waves in three orthogonal directions. Using a simple electrical control circuit, the acoustic wave transducers of each axis can be turned on individually or simultaneously. An experiment was developed to measure the pressure of the acoustic field using a microphone. Preliminary pressure magnitude results were measured for one-axis levitation along the center of the vertical axis of the levitator. The measurements suggest that the theoretical development provides a valid first approximation for the pressure magnitude and required mechanical vibration amplitude.

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Cai, Feyan, Hairong Zheng, Zhaojian He, Zhengyou Liu und Ji Wang. „Off-axis directional acoustic wave beaming control by an asymmetric rubber heterostructures film deposited on steel plate in water“. In 2009 IEEE International Ultrasonics Symposium. IEEE, 2009. http://dx.doi.org/10.1109/ultsym.2009.5441953.

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Friedt, J. M., L. El Fissi, F. Cherioux, B. Guichardaz, V. Blondeau-Patissier und S. Ballandras. „Design and Use of Wafer Level Fluidic Packaging for Surface Acoustic Wave Sensors“. In 2007 IEEE International Frequency Control Symposium Joint with the 21st European Frequency and Time Forum. IEEE, 2007. http://dx.doi.org/10.1109/freq.2007.4319099.

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Dunham, Eric M., Junwei Zhang und Dan Moos. „Constraints on Pipe Friction and Perforation Cluster Efficiency from Water Hammer Analysis“. In SPE Hydraulic Fracturing Technology Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212337-ms.

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Abstract Pressure losses from pipe and perforation friction control the relation between wellhead pressure and pressure at the mouth (entrance) of hydraulic fractures. Because both pipe and perforation friction are proportional to flow rate squared, standard step-down tests that rely on the steady pressure response at a set of injection rates cannot uniquely determine pipe and perforation friction. We introduce a novel method to resolve this nonuniqueness by analyzing the water hammer response, measured by high-rate pressure sensors at the wellhead, following abrupt rate steps during shut-in following a stimulation treatment. Constraints on perforation friction permit quantification of the number of active perforations connecting to fractures and hence perforation cluster efficiency. Our method requires a shut-in procedure with abrupt drops in injection rate to produce water hammer oscillations (tube waves propagating between the wellhead and current stage). The rate drop is accompanied by a drop in wellhead pressure as a tube wave propagates away from the wellhead, decelerating the fluid behind it. Pipe friction attenuates this wave, such that the local flow rate remains higher at depth than near the wellhead. This expands the fluid, causing additional depressurization at the wellhead until the arrival of the reflected wave from the stage. The Darcy-Weisbach pipe friction factor is determined from the depressurization rate. At high background flow rates, the reflected wave amplitude is controlled by perforation friction with minimal sensitivity to fracture properties. The claims above are substantiated by numerical simulations of tube wave propagation and reflection from perforation clusters connected to hydraulic fractures. We then present two case studies in which the method is applied data from hydraulic fracturing treatments in two stages in different wells targeting the Wolfcamp and Bone Spring Formations, Permian Basin. The inferred pipe friction factor is 2×10−3, an order of magnitude smaller than for turbulent water flow, but consistent with the use of friction reducers and pumping company pressure loss tables. The measured perforation friction is higher than predictions based on a standard formula involving fluid density, discharge coefficient, entry hole diameter, and design number of holes. This suggests not all clusters connect to fractures; the inferred cluster efficiency is 67% (Case-A, Wolfcamp) and 84% (Case-B, Bone Spring). This work extends simulation and inversion capabilities utilizing wellhead data to nonlinear problems involving tube wave interactions with hydraulic fractures and perforations. The ability to independently constrain pipe and perforation friction resolves nonuniqueness of step rate tests. Rapid inversion enables us to deliver real-time measurements of perforation cluster efficiency, pipe and perforation friction that complement traditional fracture diagnostics. Combined with acoustic pulsing to quantify near-well flow resistance, the method provides a noninvasive, cost-effective means of monitoring of the critical connection between the well and fractures during simulation treatment. The method can be used to diagnose and treat problems such as uneven fluid distribution across clusters.

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Andrienko, Yu A. „Generation of focused shock waves in medicine using lasers“. In The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cwf22.

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Nowadays, noninvasive destruction of kidney concrements using focused shock waves is a routine procedure in medicine. A patient is immersed in the water bath under the tomographic control, and then electric discharge and acoustic reflector are used to produce a series of focused shock waves to destruct the concrement.1 Authors of the technique also supposed that laser beams can be used instead of electric discharge.

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Gupta, Samikhshak, und Vijaya V. N. Sriram Malladi. „Utilizing Steady-State Traveling Waves in a Quiescent Water Environment for Particle Propulsion“. In ASME 2024 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2024. http://dx.doi.org/10.1115/smasis2024-140461.

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Abstract Using steady-state traveling waves as a propulsion mechanism emerges as a highly effective strategy for displacing particles, eliminating the need for an external fluid transfer pump. This experimental inquiry delves into the intricate application of traveling waves within a beam submerged in quiescent water, deploying two distinctive force input methods to govern particle movement acoustically. The complexity of this research lies in balancing the finesse of particle motion while concurrently imposing constraints on the number of control cycles implemented. To address this challenge comprehensively, we introduce a diverse range of control cycles tailored to manipulate particles of varying sizes. Navigating the nuanced dynamics of this system requires a sophisticated approach, prompting the adoption of the Reinforcement Learning Approach. This methodological choice empowers us to discern the characteristics of traveling waves necessary for facilitating the movement of particles with divergent sizes. The utilization of Reinforcement Learning not only refines our understanding of the intricate interplay between waves and particles but also enhances our ability to optimize control strategies in this particular context. The significance of this research extends beyond the confines of the laboratory, resonating in various applications, with particular prominence in advancing transportation mechanisms for cells and analogous entities. By elucidating the underlying principles governing the interaction between traveling waves and particles of different sizes, the findings offer invaluable insights that can be harnessed to optimize particle manipulation techniques. This holds potential implications in biotechnology, where the precision control of particle movement is pivotal for applications ranging from targeted drug delivery to the manipulation of biological cells. Furthermore, our exploration not only contributes to the theoretical understanding of particle manipulation through traveling waves but also yields tangible practical implications. The versatility of our approach, as exemplified through the successful manipulation of particles with varying sizes, underscores its potential applicability across a spectrum of scenarios, emphasizing its broader relevance within the burgeoning field of acoustic fluids. In conclusion, the utilization of steady-state traveling waves as a particle propulsion mechanism, as showcased in this experimental investigation, not only holds promise for the advancement of particle manipulation but also underscores its potential impact in diverse applications. Through the thorough exploration of control cycles and the strategic application of the Reinforcement Learning Approach, this research not only contributes to the theoretical knowledge underpinning acoustofluidics but also provides practical methodologies for precision particle manipulation. These advancements are poised to play a pivotal role in shaping the future landscape of biotechnology and related fields, where fine-tuned control over particle dynamics is a cornerstone for innovation and progress.

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Wang, Y. Jenny, und Brian W. Anthony. „Using Local Concentration to Model the Progress of Acoustophoretic Assembly of Microspheres in Planar Standing Waves“. In ASME 2023 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/imece2023-112310.

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Abstract Acoustophoretic assembly uses a standing acoustic field to move dispersed small particles into a geometric pattern. The technique relies on the acoustic radiation force, which arises from the interaction between the acoustic field and the particles, and drives the particles towards areas of low acoustophoretic potential. Acoustophoretic assembly shows potential for a wide range of applications, including organizing filler materials in composites, creating metamaterials, and fabricating functional biological tissue. However, the method has not yet been incorporated into large-scale manufacturing processes. One barrier is the incomplete understanding of the assembly process. While an ideal final pattern geometry can be calculated from the acoustic field and the material properties, there are currently no widespread metrics for measuring the progress of the pattern formation. As a result, it is difficult to know how long the acoustic field should be applied during manufacturing. Our approach uses the local particle concentration to model the acoustophoretic assembly process. When the acoustic field is applied, the acoustophoretic patterns coalesce as a whole from the initial state of randomly dispersed particles. Over time, the pattern becomes more distinct as the particles become more tightly grouped together. Thus, the process of acoustophoretic assembly can be considered a change in the local concentration of particles. We show that an expression for the time-dependent local particle concentration can be derived from the force balance on the particles and a control volume analysis. The analysis is applied to microspheres in a planar acoustic standing wave, and an analytical expression is obtained. To validate the theoretical results, experiments were carried out using polystyrene microspheres in a glycerol-water mixture. As expected, the particle concentration increases over time at regions with the lowest acoustophoretic potential, while the concentration decreases at regions with the highest acoustophoretic potential. We use the local concentration to define measurements for the quality of the assembled microsphere pattern. When the acoustic field is initially applied, the quality of the pattern changes quickly. At longer times, the quality of the pattern plateaus, and there is a diminishing return to pattern quality with each additional unit of time. This suggests that a cut-off time for pattern assembly can be implemented based on the acoustic and material properties.

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Berichte der Organisationen zum Thema "Acoustic wave control in water"

Yamamoto, Tokuo. Models of Acoustic Wave Scattering at 0.2-10 kHz From Turbulence in Shallow Water. Fort Belvoir, VA: Defense Technical Information Center, September 2008. http://dx.doi.org/10.21236/ada533110.

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Orr, Marshall H. The Influence of the Shallow Water Internal Wave Field on the Properties of Acoustic Signals. Fort Belvoir, VA: Defense Technical Information Center, September 1997. http://dx.doi.org/10.21236/ada629255.

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Godin, Oleg A., und Alexander G. Voronovich. Multiple Scattering of Sound by Internal Waves and Acoustic Characterization of Internal Wave Fields in Deep and Shallow Water. Fort Belvoir, VA: Defense Technical Information Center, September 2006. http://dx.doi.org/10.21236/ada613572.

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Yamamoto, Tokuo. Measurement and Modeling of Low Frequency Acoustic Wave Propagation and Scattering in Shallow Water with Comprehensive Subbottom Structure Measurements. Fort Belvoir, VA: Defense Technical Information Center, Februar 1996. http://dx.doi.org/10.21236/ada305049.

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Khan, Fenton, Gary E. Johnson, Ida M. Royer, Nathan RJ Phillips, James S. Hughes, Eric S. Fischer, Kenneth D. Ham und Gene R. Ploskey. Acoustic Imaging Evaluation of Juvenile Salmonid Behavior in the Immediate Forebay of the Water Temperature Control Tower at Cougar Dam, 2010. Office of Scientific and Technical Information (OSTI), April 2012. http://dx.doi.org/10.2172/1042547.

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Khan, Fenton, Gary E. Johnson, Ida M. Royer, Nathan RJ Phillips, James S. Hughes, Eric S. Fischer und Gene R. Ploskey. Acoustic Imaging Evaluation of Juvenile Salmonid Behavior in the Immediate Forebay of the Water Temperature Control Tower at Cougar Dam, 2010. Office of Scientific and Technical Information (OSTI), Oktober 2011. http://dx.doi.org/10.2172/1029871.

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Wadman, Heidi, und Jesse McNinch. Use of chirp sub-bottom acoustics to assess integrity of water-control structures : Inner Harbor Navigation Canal Lock, New Orleans. Engineer Research and Development Center (U.S.), September 2024. http://dx.doi.org/10.21079/11681/49198.

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The US Army Corps of Engineers (USACE)-maintained lock on the Inner Harbor Navigation Canal serves as a critical navigation link between Lake Pontchartrain to the north and the Mississippi River to the south. Extensive slumping has been observed on the earthen embankment on each side of the lock, suggesting that internal pathways for water to escape through the lock’s concrete walls or joints are present. Unfortunately, traditional methods often used to identify cracks in the concrete (e.g., sidescan sonar) or water-filled voids under or behind the structure (e.g., ground-penetrating radar) did not identify any structural issues at this site. Prior to dewatering and repair, the USACE New Orleans District requested that the US Army Engineer Research and Development Center conduct a sub-bottom survey at the lock to identify water-filled voids and better prepare for potential repairs during dewatering. A unique sled was constructed that allowed a small vessel to tow the sub-bottom profiler at an angle to direct more acoustic energy into the structure. Low-frequency, chirp acoustic energy successfully penetrated the concrete walls and identified several water-filled voids on both sides of the lock. A later post-dewatering walkthrough indicated that the chirp imaged voids spatially adjacent to cracks, and cracks were not found in any other locations. Additional work is needed to further develop this methodology in other USACE structures.

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Posacka, Anna, und Peter Ross. Tackling microfibre pollution through science, policy, and innovation: A framework for Canadian leadership. Raincoast Conservation Foundation, November 2024. http://dx.doi.org/10.70766/47.9973.

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Microfibre pollution has emerged as a global conservation and public health concern, prompting a wave of research related to its source, transport, fate and effects, as well as mitigation strategies. This report provides support for the Government of Canada in decision-making on microfibres, by summarizing important elements of the topic from the scientific literature, stakeholder consultations and cross-sector activities. The goal herein is to characterize the primary sources, discharge mechanisms and environmental fate of microfibre pollution in Canada, review available methodologies and definitions, list candidate solution strategies for Canadian application, and review global advances in policy and industry. Many sources and types of microfibres exist, but current evidence suggests that environmental microfibre contamination originates largely from the textile sector, with releases arising during manufacturing, trade and laundry processes. Two broad categories of textiles in this sector are relevant to the characterisation of sources, applications and processes that result in microfibre pollution in Canada, namely conventional (clothing) and technical textiles. We focus herein on conventional textiles, as a significant, but not exclusive, source of microfibres to the Canadian environment. Additional types of products that contribute microfibres to the environment are those used in the fishing, civil engineering, medical, personal care and construction sectors, and consumer products such as cigarettes. The underlying polymers used in these products can be both synthetic and natural, with both being the focus of this report. Our awareness of microfibre pollution grew out of the broader research on microplastics. This research demonstrates that microfibres, often the dominant type of microplastics, are pervasive in the environment, wildlife and drinking water. In Canada, microfibres account for approximately 80 per cent of the microplastic particles reported across water, soil, biota, air, and wastewater samples. While Canadian researchers will continue to benefit from new approaches to the sampling, detection and identification of microfibres and microplastics in the environment, having comparable data among studies and monitoring programs is crucial. Agreed-upon Quality Assurance/Quality Control (QA/QC) protocols are needed by producers, researchers, natural resource managers, consultants and regulators. This report assesses progress in the important, but at times challenging developments in the standardization and harmonization of microfibre methods, and provides guidance for stakeholders on best scientific and technical practices and the latest measurement methods. Microfibre pollution arising from textiles is a multifaceted environmental challenge that cannot be effectively mitigated through technical solutions alone. Meaningful and lasting reductions in microfibre pollution will require a holistic approach that recognizes the interconnected role of the textile value chain and the ways in which microfibres contaminate the environment. Such a system prioritizes waste reduction and waste management at all stages. Achieving a demonstrable reduction in microfibre pollution in the environment necessitates a re-evaluation and transformation of how textiles are designed, produced, used, and disposed of, ensuring sustainability is embedded at every stage. While domestic circumstances in Canada offer the most immediate regulatory and policy solution opportunities, a dual approach that helps to also capture the international supply chain is critical to the success of efforts to curtail microfibre pollution in the Canadian environment. Microfibre pollution is but one – albeit important – environmental impact associated with the textile sector. We therefore touch herein on additional impacts that may be considered so as to maximize sustainability aims and the protection of human health. A systems change approach will allow Canada to achieve wider environmental goals around the textile sector, such as reducing plastic and microfibre pollution, conserving water and energy resources, reducing the release of potentially harmful dyes and additives, reducing greenhouse gas emissions, and ultimately minimizing the overall ecological footprint of our clothing choices.

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O'Connell, Kelly, David Burdick, Melissa Vaccarino, Colin Lock, Greg Zimmerman und Yakuta Bhagat. Coral species inventory at War in the Pacific National Historical Park: Final report. National Park Service, 2024. http://dx.doi.org/10.36967/2302040.

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The War in the Pacific National Historical Park (WAPA), a protected area managed by the National Park Service (NPS), was established "to commemorate the bravery and sacrifice of those participating in the campaigns of the Pacific Theater of World War II and to conserve and interpret outstanding natural, scenic, and historic values on the island of Guam." Coral reef systems present in the park represent a vital element of Guam?s cultural, traditional, and economical heritage, and as such, are precious and in need of conservation. To facilitate the management of these resources, NPS determined that a scleractinian (stony coral) species survey was necessary to establish a baseline for existing coral communities and other important factors for conservation. EnviroScience, Inc. performed a survey of stony coral species, coral habitat, and current evidence of stressors at WAPA?s H?gat and Asan Units in 2022. This report summarizes these findings from a management perspective and compares its findings to previous survey data from 1977 and 1999 (Eldridge et al. 1977; Amesbury et al. 1999). WAPA is located on the tropical island of Guam, located on the west-central coast of the island, and encompasses 2,037 acres. Underwater resources are a significant component of the park, as 1,002 acres consists of water acres. The park is comprised of seven units, of which two of these, the H?gat and Asan Beach Units, include all the oceanic water acres for the park. The H?gat Beach Unit (local spelling, formerly known as ?Agat?) is located at the south-west portion of the park and consists of 38 land acres and 557 water acres (NPS 2003). The Asan Beach Unit consists of 109 acres of land and 445 water acres (NPS 2003). A current baseline for existing coral communities and other important factors for conservation necessitates the need for up-to-date data on the location, presence, relative abundance, and present health of corals. Park managers need this updated data to determine where and how to best focus conservation priorities and identify restoration opportunities. Management actions in park reef areas informed by this inventory included identifying locations where there were: high rates of sedimentation; high coral biomass; rare or threatened species, with a priority given to species endemic to Guam and listed as ?threatened? under the U.S. Endangered Species Act (ESA; Acropora globiceps, A. retusa, A. speciosa, and Seriatopora aculeata); coral persistence and decline, disease and/or nuisance species, including the crown-of-thorns starfish (Acanthaster cf. solaris, ?COTS?) and the sponge Terpios hoshinota; and bleached areas. All work carried out was in accordance with the NPS statement of work (SOW) requirements, which involved a quantitative inventory using both new and pre-existing transects. The resulting transects totaled 61 (including the four from the 1999 study), each measuring 50 meters in length and distributed across depths of up to 50 feet. Divers took photo-quadrat samples covering an area of approximately 9 m?, encompassing 50 photo-quadrats of dimensions 0.50 m x 0.36 m (n=50). The collective area surveyed across all 61 transects amounted to ~549 m?. Additionally, a qualitative search was conducted to enhance documentation of coral species that have limited distribution and might not be captured by transects, along with identifying harmful species and stressors. Timed roving diver coral diversity surveys were carried out at a total of 20 sites occurring within the waters of WAPA, including eight sites at the H?gat unit and 12 sites at the Asan unit. The findings from this report reveal significant disparities in benthic cover compositions between H?gat and Asan units. The H?gat unit exhibits high abundances of turf algae and unconsolidated sediment while the Asan beach unit presents a different scenario, with hard coral as the dominant benthic cover, followed closely by crustose coralline algae (CCA). The Asan unit is also more difficult to access from shore or boat relative to H?gat which provides that unit some protection from human influences. The Asan beach unit's prevalence of hard coral, CCA, and colonizable substrate suggests a more favorable environment for reef growth and the potential benefits of maintaining robust coral cover in the area. These distinct differences in benthic communities highlight the contrasting ecological dynamics and habitats of the two study areas. Across both H?gat and Asan beach unit transects, a total of 56 hard coral species were recorded from 27 genera, with 44 species recorded from the H?gat unit and 48 species recorded from the Asan unit. Of the four historical transects surveyed in the Asan unit from 1999, three experienced declines in percent coral cover (17.38-78.72%), while the fourth had an increase (10.98%). During the timed roving diver coral diversity surveys, a total of 245 hard coral species, including 241 scleractinian coral species representing 49 genera and 4 non-scleractinian coral species representing 4 genera were recorded. Uncertainties related to coral identification, unresolved boundaries between morphospecies, differences in taxonomists' perspectives, and the rapidly evolving state of coral taxonomy have significant implications for species determinations during coral diversity surveys. While the recent surveys have provided valuable insights into coral diversity in WAPA waters, ongoing taxonomic research and collaboration among experts will be essential to obtain a more comprehensive and accurate understanding of coral biodiversity in the region. Of the several ESA coral species that were searched for among the H?gat and Asan beach units, Acropora retusa was the only coral species found among quantitative transects (n=2) and A. globiceps was observed during coral diversity surveys. Acropora speciosa, which was dominant in the upper seaward slopes in 1977, is now conspicuously absent from all the surveys conducted in 2022 (Eldredge et al., 1977). The disappearance and reduction of these once-dominant species underscores the urgency of implementing conservation measures to safeguard the delicate balance of Guam's coral reefs and preserve the diversity and ecological integrity of these invaluable marine ecosystems. Other formerly common or locally abundant species were infrequently encountered during the diversity surveys, including Acropora monticulosa, A. sp. ?obtusicaulis?, A. palmerae, Stylophora sp. ?mordax?, Montipora sp. ?pagoensis?, and Millepora dichotoma. Significant bleaching-associated mortality was recorded for these species, most of which are restricted to reef front/margin zones exposed to moderate-to-high levels of wave energy. Sedimentation was present in both H?gat and the Asan units, though it was more commonly encountered in H?gat transects. While significant portions of the reef area within the WAPA H?gat unit are in poor condition due to a variety of stressors, some areas still hosted notable coral communities, which should be a potential focus for park management to prevent further degradation. There is a need for more effective management of point source pollution concerns, particularly when subpar wastewater treatment or runoff from areas with potential pollution or sediment-laden water is flowing from nearby terrestrial environments. Future monitoring efforts should aim to establish a framework that facilitates a deeper understanding of potential point source pollution incidents. This would empower park managers to collaborate with adjacent communities, both within and outside of park boundaries, to mitigate the localized impacts of pollution (McCutcheon and McKenna, 2021). COTS were encountered during transect surveys as well as in coral diversity surveys. including along the upper reef front/reef margin at site Agat-CS-2. The frequency of these observations, particularly in the WAPA H?gat unit and where stress-susceptible corals are already uncommonly encountered, raise concern about the ability of the populations of these coral species to recover following acute disturbance events, and calls in to question the ability of some of these species to persist in WAPA waters, and in Guam?s waters more broadly. More frequent crown-of-thorns control efforts, even if only a handful of sea stars are removed during a single effort, may be required to prevent further loss to vulnerable species. There were several documented incidents of Terpios hoshinota covering large sections of branching coral in the reef flat along transects, but it is still unclear how detrimental this sponge is to the overall reef system. There is a concern that elevated levels of organic matter and nutrients in the water, such as those resulting from sewage discharge or stormwater runoff, could lead to increased Terpios populations (De Voogd et al. 2013). Consequently, it is important to track populations in known areas of sedimentation and poor water quality. The presence of unique species at single survey sites within the study areas underscores the ecological importance of certain locations. Some species are known to occur in other locations in Guam, while a few may be limited to specific sites within WAPA waters. These differences are likely influenced by environmental and biological factors such as poor water quality, severe heat stress events, chronic predation by crown-of-thorns sea stars, disease, and reduced herbivore populations. These factors collectively shape the condition of the benthic community, leading to variations in species distribution and abundance across the study sites. Documenting coral stress and identifying potentially harmful species allows for proactive management strategies to prevent the establishment of nuisance or detrimental species while populations are still manageable. Updated data on the location, presence, relative abundance, and health of corals is essential for park managers to prioritize conservation efforts and identify restoration opportunities effectively. Observations from this report raise concerns about the health and resilience of coral ecosystems in the H?gat unit and emphasize the need for knowledge of local factors that shape benthic community structure. Understanding the drivers responsible for these variations is crucial for effective conservation and management strategies to preserve the ecological balance and overall health of coral reefs in both units. Continued monitoring efforts will be critical in assessing long-term trends and changes in benthic cover and enabling adaptive management approaches to safeguard these valuable marine ecosystems in the face of ongoing environmental challenges.

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