Estudio de efectos de asimetría en vibradores ultrasónicos axisimétricos

8 pages, 6 figures.-- Comunicación presentada en: XXXV Congreso Español de Acústica – TecniAcústica 2004, IV Congreso Iberoamericano de Acústica, IV Congreso Ibérico de Acústica y EAA Symposium "Environmental and Architectural Acoustics" (Guimaraes, 14-17 Sep 2004).[EN] The use of high-power ultrasonic plate transducers shows a series of problems related with the presence of modal coupling or interactions between the vibrational modes of the ultrasonic system. In such system, the radiator consists of a stepped circular plate. The radiator plate is driven at its centre by a tuned piezoelectric vibrator generating an axysimetric mode of vibration. Nevertheless, in many cases the nodal figures are deformed and present ovals instead of circles in the plate. This phenomenon which is frequently observed can be basically due to two main reasons: the material anisotropy and the influence of the high-density of nonaxysimetrical modes around the operating frequency.This paper deals with the study and analysis of both possibilities using numerical simulations by finite element techniques and experimental measurements.[ES] El uso de transductores ultrasónicos de potencia del tipo placa vibrante, plantea una serie de problemas relacionados con el posible acoplamiento o interacción entre los diversos modos de vibración que contiene el sistema. En estos transductores el radiador está constituido por una placa vibrante de geometría circular y perfil escalonado. Esta placa se pone en vibración mediante un excitador piezoeléctrico sintonizado a la frecuencia del modo de vibración de interés. La placa radiante se excita sinusoidalmente en su centro generando un modo de vibración axisimétrico. Las figuras nodales que se forman son círculos concéntricos. Sin embargo, en muchos casos aparecen asimetrías en el modo de vibración, de forma que las figuras nodales aparecen deformadas en forma de óvalos. Este fenómeno, que se repite con determinada frecuencia, puede ser debido fundamentalmente a dos causas: la influencia de modos cercanos no axisimétricos o a la anisotropía del material.En este trabajo se estudian y analizan ambas posibilidades empleando tanto técnicas de simulación numérica por elementos finitos como medidas experimentales.Este trabajo ha sido financiado con cargo al Proyecto del Plan Nacional de Investigación DPI 2002-3409.Peer reviewe

A NEW HIGH-INTENSITY ULTRASONIC TECHNOLOGY FOR FOOD DEHYDRATION

12 páginas, 7 figurasAt present, there is a growing interest in the field of dehydration for preserving food. Ultrasonic energy represents a means to obtain dehydration without affecting the food. This paper deals with an experimental study about the use of high-intensity ultrasound for vegetable dehydration by using a new power ultrasound generator and a procedure in which ultrasonic vibrations are applied in direct contact with the product and under a certain static pressure. The drying effect of this new process is compared with that obtained from forced-air drying assisted by air-borne ultrasonic radiation and from a conventional hot-air drying. The results show that by using the new technology and procedure it is possible to reduce dramatically the treatment time and it is relatively easy to reach a final moisture content in the samples less than 1%. In addition, the product qualities are well preserved, the sample rehydration is higher than 70% and, because of the high efficiency of the new ultrasonic system employed, the energy consumption is low. As a consequence of the results a new technology for industrial applications is under development.Peer reviewe

Industrial requirements in high-power ultrasonic transducers for defoaming

Ponencia presentada en el XIX Congreso Internacional de Acústica (ICA2007), Madrid, 2-7 Sep 2007.-- PACS: 43.35.-c.Airborne stepped-plate focusing transducers have shown to be an efficient tool for breaking foams. The main characteristics of such transducers are their high efficiency and power capacity as well as their strong focusing effect. As a consequence, by using these power transducers it is possible to generate intensities in the focal area as high as 170 dB. However, for their application to industrial problems a special design has to be done covering specific requirements. The main requirements for industrial applications refer to efficiency, safety, durability and environmental resistance. This paper deals with the design and characterization of an industrial prototype of high power ultrasonic transducer for defoaming which is able to work in continuous operation under adverse environmental conditions, and high power excitation without the use of any cooling system. In addition, the transducer is designed to ensure the safe use of airborne high-power ultrasound according to the international recommendations for occupational exposure limits.The industrial use of the transducers is for defoaming in bottling and canning lines and in fermenting vessels and other reactors.The work has been carried out in the frame of the Project: “Adaptation to requirements and industrial standards of an ultrasonic system for foam elimination and control, (CSIC Intramural Programme PIE 2004-50E193).Peer reviewe

Automatic real-time monitoring and assessment of tremor parameters in the upper limb from orientation data

Upper limb tremor is the most prevalent movement disorder and, unfortunately, it is not effectively managed in a large proportion of the patients. Neuroprostheses that stimulate the sensorimotor pathways are one of the most promising alternatives although they are still under development. To enrich the interpretation of data recorded during long-term tremor monitoring and to increase the intelligence of tremor suppression neuroprostheses we need to be aware of the context. Context awareness is a major challenge for neuroprostheses and would allow these devices to react more quickly and appropriately to the changing demands of the user and/or task. Traditionally kinematic features are used to extract context information, with most recently the use of joint angles as highly potential features. In this paper we present two algorithms that enable the robust extraction of joint angle and related features to enable long-term continuous monitoring of tremor with context awareness. First, we describe a novel relative sensor placement identification technique based on orientation data. We focus on relative rather than absolute sensor location, because in many medical applications magnetic and inertial measurement units (MIMU) are used in a chain stretching over adjacent segments, or are always placed on a fixed set of locations. Subsequently we demonstrate how tremor parameters can be extracted from orientation data using an adaptive estimation algorithm. Relative sensor location was detected with an accuracy of 94.12% for the 4 MIMU configuration, and 100% for the 3 MIMU configurations. Kinematic tracking error values with an average deviation of 8% demonstrate our ability to estimate tremor from orientation data. The methods presented in this study constitute an important step toward more user-friendly and context-aware neuroprostheses for tremor suppression and monitoring

Analysis of the nonlinear reverberation of titanium alloys fatigued at high amplitude ultrasonic vibration

6 pages.-- PACS nr.: 81.40.-Z.-- Communication presented at: Forum Acusticum Sevilla 2002 (Sevilla, Spain, 16-20 Sep 2002), comprising: 3rd European Congress on Acoustics; XXXIII Spanish Congress on Acoustics (TecniAcústica 2002); European and Japanese Symposium on Acoustics; 3rd Iberian Congress on Acoustics.-- Special issue of the journal Revista de Acústica, Vol. XXXIII, year 2002.The strong amplitude dependence of material parameters of microinhomogeneous materials can be used to link observations of nonlinearity to micro-scale damage. We have measured the amplitude dependence of the resonance frequency and damping characteristics in the reverberation field of the fundamental eigenmode of titanium alloy samples at regular instances during dynamic fatigue loading at high strains. The analysis of the reverberation is performed in the frequency domain using classical time-windowed FFT, as well as in the time domain using analytical functions with iteratively optimised parameters over each time window. The results show a significant increase of the nonlinearity in the frequency and damping characteristics of the signals observed during the fatiguing process.The authors would like to thank the ESF organisation for support of this research in the frame of the PESC-program NATEMIS (www.polito.it/research/natemis/).Peer reviewe

Procedimiento y sistema ultrasónico de desespumación mediante emisores con placa vibrante escalonada

Referencia OEPM: P200202113.-- Fecha de solicitud: 13/09/2002.-- Titular: Consejo Superior de Investigaciones Científicas (CSIC).Procedimiento y sistema ultrasónico de desespumación mediante emisores con placa vibrante escalonada (ver figura en archivo de texto adjunto). El objeto de esta solicitud de patente es un dispositivo ultrasónico que permite eliminar espumas y controlar su crecimiento en grandes contenedores. El dispositivo emplea emisores sónicos y/o ultrasónicos del tipo placa vibrante escalonada, especiales para radiar altas intensidades acústicas en gases, los cuales, al estar libremente suspendidos en un soporte giratorio con rotación variable controlada, generan en su movimiento por acción de la fuerza centrífuga un recorrido complejo de los haces acústicos emitidos que permite barrer la superficie sobre la que se forma la espuma. Por efecto de la alta intensidad acústica ( >170 dB ref. 2.10^-4 μbar) gran parte de las burbujas de la espuma se van rompiendo casi instantáneamente al paso del haz ultrasónico.Peer reviewe

One central oscillatory drive is compatible with experimental motor unit behaviour in essential and Parkinsonian tremor

Pathological tremors are symptomatic to several neurological disorders that are difficult to differentiate and the way by which central oscillatory networks entrain tremorogenic contractions is unknown. We considered the alternative hypotheses that tremor arises from one oscillator (at the tremor frequency) or, as suggested by recent findings from the superimposition of two separate inputs (at the tremor frequency and twice that frequency). Approach. Assuming one central oscillatory network we estimated analytically the relative amplitude of the harmonics of the tremor frequency in the motor neuron output for different temporal behaviors of the oscillator. Next, we analyzed the bias in the relative harmonics amplitude introduced by superimposing oscillations at twice the tremor frequency. These findings were validated using experimental measurements of wrist angular velocity and surface electromyography (EMG) from 22 patients (11 essential tremor, 11 Parkinson’s disease). The ensemble motor unit action potential trains identified from the EMG represented the neural drive to the muscles. Main results. The analytical results showed that the relative power of the tremor harmonics in the analytical models of the neural drive was determined by the variability and duration of the tremor bursts and the presence of the second oscillator biased this power towards higher values. The experimental findings accurately matched the analytical model assuming one oscillator, indicating a negligible functional role of secondary oscillatory inputs. Furthermore, a significant difference in the relative power of harmonics in the neural drive was found across the patient groups, suggesting a diagnostic value of this measure (classification accuracy: 86%). This diagnostic power decreased substantially when estimated from limb acceleration or the EMG. Signficance. The results indicate that the neural drive in pathological tremor is compatible with one central network providing neural oscillations at the tremor frequency. Moreover, the regularity of this neural oscillation varies across tremor pathologies, making the relative amplitude of tremor harmonics a potential biomarker for diagnostic use

Aglomeración acústica de partículas

PACS: 43.35, 43.25.-- Publicado en el Vol. XXXI, núm. 3-4, tercer y cuarto trimestre 2000 de la Revista de Acústica: Número especial dedicado al XXV Aniversario del Instituto de Acústica del C.S.I.C.[ES] En este trabajo se presenta una recopilación de las principales aportaciones llevadas a cabo en el campo de la aglomeración acústica de partículas desde 1972. A lo largo de este periodo de tiempo se ha consolidado esta línea de investigación. Se han estudiado y simulado numéricamente los mecanismos básicos del proceso de aglomeración. Paralelamente se han desarrollado y validado nuevos sistemas macrosónicos a escala de laboratorio y de planta piloto para la retención de partículas finas (0.1 - 2.5 μm) en efluentes industriales. Los principales logros científicos llevados a cabo en esta temática han dado lugar a más de setenta publicaciones internacionales.[EN] A summary of the most relevant R+D contributions since 1972 on the acoustic particle agglomeration is presented in this paper. Along this period the research topic has been well consolidated. The basic mechanisms involved in the agglomeration process have been studied and simulated numerically. In parallel, new macrosonic systems at laboratory and pilot plant scale have been developed and validated to reduce fine particle emissions (0.1 - 2.5 μm). The main scientific results obtained were published in more than seventy international papers.Peer reviewe

Profile and characteristics of the adequacy of blood transfusions in Trauma Intensive Care. A cross sectional multicenter study

IntroductionMajor trauma is one of the major health care problems facing modern society, trauma systems require careful planning to achieve an ideal level of coverage for the population. The Patient Blood Management Program is an integrated and global strategy to provide patient care that aims to assess and address, when possible, the etiology of blood abnormalities rather than transfuse without treating the underlying cause. We aimed to describe the factors that are associated with the clinical decision to transfuse polytraumatized patients admitted to the Intensive Care Unit (ICU).MethodWe performed a cross sectional multicenter study of patients admitted to ICUs for trauma in 14 Spanish hospitals from September 2020 to December 2021.ResultsA total of 69 patients were treated in the emergency room due to polytrauma, 46% of them were considered serious in the initial triage. Thirty were caused by a fall from considerable height (43.47%), followed by 39 patients admitted due to trac accidents (56.52%). The location of the trauma was mainly cranioencephalic, followed by thoracic trauma. Of the 69 patients, 25 received a blood transfusion during their ICU stay (36.23%).DiscussionNo significant differences were observed between transfused and non-transfused patients, except for the severity scales, where transfused patients have a higher score on all the scales assessed in the ICU except for the Revised Trauma Score. As we can see, the incidence of kidney failure was also different between the groups analyzed, reaching 44.00% in transfused patients and 13.64% in the group of patients without blood transfusion, p = 0.005. In this sense, 92.00% of the transfusions performed were inadequate according to the criteria of Hb in blood prior to the decision to transfuse (Hb < 9). Our data support the need to consider clinical practice guidelines regarding blood transfusion and its practices

Profile and characteristics of the adequacy of blood transfusions in Trauma Intensive Care. A cross sectional multicenter study

IntroductionMajor trauma is one of the major health care problems facing modern society, trauma systems require careful planning to achieve an ideal level of coverage for the population. The Patient Blood Management Program is an integrated and global strategy to provide patient care that aims to assess and address, when possible, the etiology of blood abnormalities rather than transfuse without treating the underlying cause. We aimed to describe the factors that are associated with the clinical decision to transfuse polytraumatized patients admitted to the Intensive Care Unit (ICU).MethodWe performed a cross sectional multicenter study of patients admitted to ICUs for trauma in 14 Spanish hospitals from September 2020 to December 2021.ResultsA total of 69 patients were treated in the emergency room due to polytrauma, 46% of them were considered serious in the initial triage. Thirty were caused by a fall from considerable height (43.47%), followed by 39 patients admitted due to trac accidents (56.52%). The location of the trauma was mainly cranioencephalic, followed by thoracic trauma. Of the 69 patients, 25 received a blood transfusion during their ICU stay (36.23%).DiscussionNo significant differences were observed between transfused and non-transfused patients, except for the severity scales, where transfused patients have a higher score on all the scales assessed in the ICU except for the Revised Trauma Score. As we can see, the incidence of kidney failure was also different between the groups analyzed, reaching 44.00% in transfused patients and 13.64% in the group of patients without blood transfusion, p = 0.005. In this sense, 92.00% of the transfusions performed were inadequate according to the criteria of Hb in blood prior to the decision to transfuse (Hb < 9). Our data support the need to consider clinical practice guidelines regarding blood transfusion and its practices