Analysis of the modeling of echo responses from circular concavity defects using impulse response and discrete representation methods

AbstractIn this work the impulse response and the discrete representation method are applied to model the acoustic wave generated by ultrasonic transducers, its interaction with the defect, and the echoes received by the transducer. Several simulations are performed to determine the echo responses arising from a concave circular defect on a plane surface, using a planar circular piston emitting pulses in water. The simulations are calculated using the Matlab software. The effects of defect size and field position on both amplitude and shape of the echo responses are investigated. Moreover, experimental measurements of the acoustic field are compared with the simulations. The experimental results, based on the above-mentioned process, were obtained using 1.6 and 2.25MHz transducers

Acoustic levitation in mid-air: recent advances, challenges, and future perspectives

Mid-air acoustic levitation is becoming a powerful tool to suspend and manipulate millimetric objects. Because of its unique characteristics, acoustic levitation is suitable to trap a wide variety of materials such as liquids, solids, soap bubbles, and even living creatures. Acoustic levitation can also be combined with noncontact measurement systems, allowing contactless analysis and characterization of levitating samples. In this article, we review some of the advances that have been made over the last decade. We also present the technical challenges that must be overcome in order to extend the capability of current acoustic levitation devices and, finally, we point out future directions for acoustic levitation.This work was supported by the São Paulo Research Foundation–FAPESP (Grant No. 2017/27078-0) and by the Government of Navarre through Fondo Europeo de Desarrollo Regional (FEDER) Project No. 0011-1365-2019-000086

Contactless pick-and-place of millimetric objects using inverted near-field acoustic levitation

We model and realize an ultrasonic contactless pick-and-place device capable of picking, self-centering, self-orienting, translating, and releasing flat millimetric objects. The device is an ultrasonic Langevin transducer operating at 21 kHz that radiates into air through a tapered tip. Objects are trapped few micrometers below the tip due to the near-field acoustic levitation phenomenon. We first investigate the conditions to achieve an attractive force on the object depending on its size and the device operating frequency. Second, we use a 3D acoustic model that describes the converging forces and torque that provide the self-centering and self-orienting capabilities. Third, a more advanced Computational Fluid Dynamics model based on the Navier-Stokes equations explains the small gap between the tip and the trapped object. The contactless manipulation capabilities of the device are demonstrated by picking, transporting, and releasing a Surface Mount Device in air. The presented manipulation concept can be an interesting alternative for manipulating delicate objects such as microelectromechanical devices, silicon dies, or micro-optical devices.This research was supported by the São Paulo Research Foundation—FAPESP (Grant Nos. 2017/27078-0 and 2018/04101-0)

Novas narrativas sociais: as práticas de mídia livre através do audiovisual

Dissertação de mestrado apresentada à Escola Superior de Comunicação Social como parte dos requisitos para obtenção de grau de mestre em Audiovisual e Multimédia.Com a proliferação e popularização dos aparatos móveis de comunicação digital e o avanço dos dispositivos conectados à Internet, a mídia ganhou novos contornos, tanto quantitativos quanto qualitativos. O intenso fluxo de mudanças, em constante curso e evolução, trouxe para as mãos do grande público o material e espaço necessários para ser ativo na transmissão de mensagens na sociedade; em contrapartida, gerou uma perda do controle do conteúdo, excesso de informação disponível e inúmeros novos formatos de transmissão. Este trabalho pretende revisitar a bibliografia da área ao longo das últimas décadas, ressaltando os debates e teorias levantadas de acordo com as principais mudanças na Comunicação Social. As principais características da cada época trarão um contexto macro de manifestações sociais que hoje também apresentam-se no contexto micro. O uso social dos meios de comunicação é o foco e ponto chave para discutir o papel social, efetivo ou potencial, da mídia. Para que o benefício de controlar os meios de produção da informação, bem como aproveitar a liberdade presente no ciberespaço, seja utilizado em prol da sociedade e em favor da democracia. A importância histórica e social do discurso e da narrativa será explicado para comprovar a importância do debate sobre a mídia livre, assim como as suas principais características e práticas, ilustradas através do objeto de estudo, o coletivo Mídia NINJA.ABSTRACT: With the proliferation and popularization of mobile digital communication devices and the advancement of devices connected to the Internet, the media has gained new contours, both quantitative and qualitative. The intense flow of change, in constant progress and evolution, has brought into the hands of the general public the material and space necessary to be active in the transmission of messages in society; on the other hand, generated a loss of control of the content, excessive information available and numerous new transmission formats. This work intends to revisit the bibliography of the area over the last decades, highlighting the debates and theories raised according to the main changes in social communication. The main characteristics of each period will bring a macro context of social manifestations that today also present themselves in the micro context. The social use of the media is the focus and key point to discuss the social role, effective or potential, of the media. So that the benefit of controlling the means of information production, as well as taking advantage of the freedom present in cyberspace, be used for the benefit of society and for democracy. The historical and social importance of discourse and narrative will be explained to prove the importance of the debate about free media, as well as its main characteristics and practices, illustrated through the object of study, the collective Mídia NINJA.N/

Caracterización de emulsiones de agua y aceite por ultrasonidos

[ES] En este trabajo se presentan resultados de medidas de pequeñas concentraciones de agua en aceite lubricante utilizando una célula de medida por ultrasonidos. Esta célula es compuesta por un emisor piezocerámico (5 y 10 MHz), y un receptor de PVDF de grande apertura, que elimina efectos de difracción. A través de la medida de la velocidad de propagación, se puede diferenciar cantidades de agua en aceite con una resolución de un 0,2% en volumen, en el rango comprendido entre 0 y 5%. El máximo error en la medida de la velocidad de propagación es 0,003% a través de la utilización de una técnica de procesamiento digital de señales precisa.[EN] This paper presents an ultrasonic method to measure small concentrations of water in lubricating oil. It uses an ultrasonic measurement cell composed by a piezoceramic emitter (5 and 10 MHz), and a PVDF receiver of large aperture that eliminates the effect of diffraction. The concentrations of water of the samples were in the range of 0 to 5% in volume, and the results showed that these low concentrations can be discriminated within a resolution of 0.2% in the studied range. The maximun error obtained in the measurement of the propagation velocity is 0.003% by using an accurate signal processing method.6 pp.-- PACS nr.: 43.35.Zc.-- Comunicación presentada en los siguientes congresos: II Congreso Iberoamericano de Acústica. XXXI Congreso Nacional de Acústica – TecniAcústica 2000. II Jornadas Iberoamericanas de Ultrasonidos. II Congreso Ibérico de Acústica. EAA Symposium on Architectural Acoustics (Madrid, 16-20 Octubre 2000). Publicado también en número especial de la Revista de Acústica, Vol. XXXI, año 2000.Peer reviewe

Ultrasonic Viscosity Measurement Using the Shear-Wave Reflection Coefficient with a Novel Signal Processing Technique

Real-time viscosity measurement remains a necessity for highly automated industry. To resolve this problem, many studies have been carried out using an ultrasonic shear wave reflectance method. This method is based on the determination of the complex reflection coefficient`s magnitude and phase at the solid-liquid interface. Although magnitude is a stable quantity and its measurement is relatively simple and precise, phase measurement is a difficult task because of strong temperature dependence. A simplified method that uses only the magnitude of the reflection coefficient and that is valid under the Newtonian regimen has been proposed by some authors, but the obtained viscosity values do not match conventional viscometry measurements. In this work, a mode conversion measurement cell was used to measure glycerin viscosity as a function of temperature (15 to 25 degrees C) and corn syrup-water mixtures as a function of concentration (70 to 100 wt% of corn syrup). Tests were carried out at 1 MHz. A novel signal processing technique that calculates the reflection coefficient magnitude in a frequency band, instead of a single frequency, was studied. The effects of the bandwidth on magnitude and viscosity were analyzed and the results were compared with the values predicted by the Newtonian liquid model. The frequency band technique improved the magnitude results. The obtained viscosity values came close to those measured by the rotational viscometer with percentage errors up to 14%, whereas errors up to 96% were found for the single frequency method.Coordinacao de Aperfeicoamento de Pessoal de Nivel Superior (Capes)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq

Particle manipulation by ultrasonic progressive waves

AbstractThis paper presents a numerical model to determine the trajectory of sphere particles when submitted to ultrasonic progressive waves. This model assumes that the following forces act on the particle: gravity, buoyancy, viscous forces and acoustic radiation force due to progressive wave. In order not to restrict the model to a small particle size range, the viscous forces that act on the sphere are modeled by an empirical relationship of drag coefficient that is valid for a wide range of Reynolds numbers. The numerical model requires the pressure field radiated by the ultrasonic transducer. The pressure field is obtained experimentally by using a calibrated needle hydrophone. The numerical model validation is done by dropping small glass spheres (on the order of 500 μm diameter) in front of a 1-MHz 30-mm diameter ultrasonic transducer. When the particles cross the transducer face, the radiation force produced by the transducer pushes the particles away. The glass particles trajectory is obtained by a CCD camera. The experimental trajectory shows good agreement with that predicted by the numerical model

Sensor ultrasónico para la presencia de contaminantes oleosos en agua

La determinación del coeficiente de reflexión de ondas transversales ultrasónicas en la interfaz sólido-líquido es una técnica que ha sido usada para la medición de las propiedades viscoelásticas de líquidos. Una característica interesante de la técnica es la pequeña distancia recorrida por las ondas transversales dentro del fluido, antes de ser completamente atenuadas, permitiendo la medición con una película muy delgada de líquido, del orden de algunos micrómetros. Esta característica, además de la conocida tendencia de las sustancias oleosas a adherirse a superficies, puede ser usada para la detección de contaminantes oleosos en agua. Este trabajo propone el uso de la técnica de reflexión de ondas transversales en el rango ultrasónico para la detección de contaminantes oleosos en agua y discute las bases teóricas y experimentales relacionadas. Resultados experimentales preliminares muestran que es posible la detección de la presencia de aceite automotriz SAE 40 en agua en proporciones menores a 0,5% en volumenThe determination of the complex reflection coefficient of ultrasonic shear-waves at the solid-liquid interface is a technique employed for the measurement of the viscoelastic properties of liquids. An interesting property of the measurement technique is the very small penetration depth of the shear-waves into the liquid sample, which permits measurements with liquid films of some micrometers thick. This property, along with the adhesion of oily substances to surfaces, can be used for the detection of oily contaminants in water. In this work, the employment of the ultrasonic shear-wave reflection technique to the detection of oily contaminants in water is proposed and the theoretical and experimental concepts involved are discussed. Preliminary experimental results show the measurement technique can detect SAE 40 automotive oil in water in volume proportions less than 0.5

Experimental Investigation of the Hydrodynamic Coefficients of a Remotely Operated Vehicle Using a Planar Motion Mechanism

The determination of hydrodynamic coefficients of full scale underwater vehicles using system identification (SI) is an extremely powerful technique. The procedure is based on experimental runs and on the analysis of on-board sensors and thrusters signals. The technique is cost effective and it has high repeatability; however, for open-frame underwater vehicles, it lacks accuracy due to the sensors' noise and the poor modeling of thruster-hull and thruster-thruster interaction effects. In this work, forced oscillation tests were undertaken with a full scale open-frame underwater vehicle. These conducted tests are unique in the sense that there are not many examples in the literature taking advantage of a PMM installation for testing a prototype and; consequently, allowing the comparison between the experimental results and the ones estimated by parameter identification. The Morison's equation inertia and drag coefficients were estimated with two parameter identification methods, that is, the weighted and the ordinary least-squares procedures. It was verified that the in-line force estimated from Morison's equation agrees well with the measured one except in the region around the motion inversion points. On the other hand, the error analysis showed that the ordinary least-squares provided better accuracy and, therefore, was used to evaluate the ratio between inertia and drag forces for a range of Keulegan-Carpenter and Reynolds numbers. It was concluded that, although both experimental and estimation techniques proved to be powerful tools for evaluation of an open-frame underwater vehicle's hydrodynamic coefficients, the research provided a rich amount of reference data for comparison with reduced models as well as for dynamic motion simulation of ROVs. [DOI: 10.1115/1.4004952]FINEP through CTPetro/ANPFINEP through CTPetro/ANPCNPqCNPqFAPESPFAPES