Influence of adding salt on ultrasonic atomization in an ethanol-water solution

Ethanol was enriched by ultrasonic atomization. Enrichment ratios were increased by adding salt to the ethanol solution. Different enrichment ratios were observed for different types of salts in a range of low ethanol concentrations. The enrichment ratio was significantly improved by adding K(2)CO(3) or (NH(4))(2)SO(4). It is concluded that this is due to enhanced interfacial adsorption of the ethanol. Addition of Na(2)CO(3) to the ethanol solution also enhanced the interfacial adsorption of the ethanol, but the effect was relatively small. Addition of NaCl to the ethanol solution did not enhance the interfacial adsorption of the ethanol.     

Enrichment of surfactant from its aqueous solution using ultrasonic atomization

Dilute aqueous solutions of dodecyl-benzenesulfonic acid sodium salt (DBS-Na) and polyoxyethylenenonylphenyl ethers (PONPEs) were ultrasonically atomized. The surfactants were concentrated in collected mist droplets. The enrichment ratio increased with decreasing surfactant concentration. Depending on the surfactant’s molecular weight and affinity to water, different enrichment ratio was observed in the range of low feed concentrations. For anionic surfactant, DBS-Na, the enrichment ratio was significantly improved by KCl addition and a peak appeared on the plot of the ratio against KCl concentration. Addition of NaCl or CaCl₂ · 2H₂O to the surfactant solution also enhanced the enrichment ratio; however, the effect was relatively small. Such behaviors of the ratio were interpreted as enhanced interfacial adsorption of the surfactant and a lack of supply of surfactant monomers from liquid bulk because of slow breaking of surfactant micelles. Time required for collecting an amount of mist was also observed. Among the three salt systems, the time for KCl system was twice as long as others. This fact suggested that the formation of smaller droplets in KCl system.     

Double-structured ultrasonic high frequency reactor using an optimised slant bottom

The present work has been carried out in order to design a new type of ultrasonic reactor consisting of a double-structured tank. The inner working compartment is built with a slant bottom to allow a better ultrasonic transmission. This paper reports the effect of the inclination angle on acoustic efficiency for several different plates, e.g. two plates made of glass (2 mm and 3 mm thickness) and one made of PVC (3 mm thickness). The acoustic efficiency was determined as the ratio of the signal measured by a hydrophone in the presence of the plate to that signal in the absence of the plate. Having optimised the system, the ultrasonic powers in the inner and the outer compartments of the slant bottom reactor were determined by hydrogen peroxide dosimetry.     

Modeling of a high frequency ultrasonic transducer using periodic structures

Solidly mounted integrated transducers with a Bragg cell inserted between the piezoelectric film and the substrate are investigated for high frequency ultrasonic applications. A numerically stable recursive one dimensional transmission/reflection model was used to analyze the behavior of the periodic structure. This theoretical analysis includes the study of the influence of the acoustic properties of the constitutive layer, the effect of the number of cells and their arrangement. A 35 MHz integrated transducer consisting in a PZT ceramic laid down on a Au/PZT Bragg cell deposited on a porous substrate was fabricated and characterized. Both theoretical and experimental results highlight the interest of using a periodic structure for high frequency ultrasonic applications.     

Effect of ultrasonic frequency on size distributions of nanosized mist generated by ultrasonic atomization

Ultrasonic atomization is used to produce fine liquid mists with diameter ranges below 100 nm. We investigated the effect of the frequency on the size distribution of ultrasonic mist. A bimodal distribution was obtained for the mist generated by ultrasonic atomization with a wide-range particle spectrometer. The peak diameter decreased with increasing frequency, and the number concentration of the mist increased in the smaller range. We determined the relation between the size distribution of the mist and the ultrasonic frequency, and we proposed a generation mechanism for the ultrasonic nanosized mist based on the amount of water vapor around the liquid column. Increasing the power intensity and density by changing the surface diameter of the ultrasonic oscillator affected the number concentration and size distribution of the nanosized mist. Using this technique, the diameter of the mist can be controlled by changing the frequency of the ultrasonic transducer.     

Non-destructive testing of ceramic balls using high frequency ultrasonic resonance spectroscopy

Although ceramic balls are used more and more for bearings in the aerospace and space industries, defects in this type of ceramic material could be dangerous, particularly if such defects are located close to the surface. In this paper, we propose a non-destructive testing method for silicon nitride balls, based on ultrasonic resonance spectroscopy. Through the theoretical study of their elastic vibrations, it is possible to characterize the balls using a vibration mode that is similar to surface wave propagation. The proposed methodology can both excite spheroidal vibrations in the ceramic balls and detect such vibrations over a large frequency range. Studying their resonance spectrums allows the balls’ elastic parameters be characterized. Ours is an original method that can quickly estimate the velocity of surface waves using high frequency resonances, which permits surface and sub-surface areas to be tested specifically. Two applications are described in this paper. Both use velocity measurements to achieve their different goals, the first to differentiate between flawless balls from different manufacturing processes, and the second to detect small defects, such as cracks. Our method is rapid and permits the entire ceramic ball to be tested in an industrial context.     

Energetic balance in an ultrasonic reactor using focused or flat high frequency transducers

In order to undertake irradiation of polymer blocks or films by ultrasound, this paper deals with the measurements of ultrasonic power and its distribution within the cell by several methods. The electric power measured at the transducer input is compared to the ultrasonic power input to the cell evaluated by calorimetry and radiation force measurement for different generator settings. Results obtained in the specific case of new transducer types (composites and focused composites i.e., HIFU: high intensity focused ultrasound) provide an opportunity to conduct a discussion about measurement methods. It has thus been confirmed that these measurement techniques can be applied to HIFU transducers. For all cases, results underlined the fact that measurement of radiation pressure for power evaluation is more adapted to low powers (<15 W) and that measurement by calorimetry is a valid technique for global energy measurements. Composites and monocomponent transducers were compared and it appears that the presence of an adaptation glass plate reduces the efficiency of the monocomponent transducers. The distribution of ultrasonic intensity is qualitatively depicted by sono-chemiluminescence of luminol. Finally, the quantity of energy absorbed by samples placed in the sound field is determined and the temperature distribution monitored as a function of wall distance. This energetic balance allows us to understand the global behaviour of all experimental set-ups made up of a generator–transducer–liquid and sample.     

PZT厚膜及高频超声换能器的研究

近年来,基于PZT厚膜的超声换能器研究受到了广泛的重视。本文综述了PZT厚膜制备技术的发展情况,简要介绍了水下声纳和医用超声领域中PZT厚膜型高频超声换能器的应用研制进展。     

Separation characteristics of alcohol from aqueous solution by ultrasonic atomization

The generation rate of ultrasonically atomized droplets and the alcohol concentration in droplets were estimated by measuring the flow rate and the alcohol concentration of vapors from a bulk solution with a fountain. The effect of the alcohol concentration in the bulk solution on the generation rate of droplets and the alcohol concentration in droplets were investigated. The ultrasonic frequency was 2.4 MHz, and ethanol and methanol aqueous solutions were used as samples. The generation rate of droplets for ethanol was smaller than that for methanol at the same alcohol molar fraction in the bulk solution. For both solutions, at low alcohol concentration in the bulk solution, the alcohol concentration in droplets was lower than that in vapors and the atomized droplets were visible. On the other side, at high concentration, the concentration in droplets exceeded that in vapors and the atomized droplets became invisible. These results could be explained that the alcohol-rich clusters in the bulk solution were preferentially atomized by ultrasonic irradiation. The concentration in droplets for ethanol was higher than that for methanol at low alcohol concentration because the amount of alcohol-rich clusters was larger. When the alcohol molar fraction was greater than 0.6, the atomized droplets almost consisted of pure alcohol.     

Characteristics of coated copper wire specimens using high frequency ultrasonic complex vibration welding equipments

Welding characteristic of thin coated copper wires were studied using 40, 60, 100 kHz ultrasonic complex vibration welding equipments with elliptical to circular vibration locus. The complex vibration systems consisted of a longitudinal-torsional vibration converter and a driving longitudinal vibration system. Polyurethane coated copper wires of 0.036 mm outer diameter and copper plates of 0.3 mm thickness and the other dimension wires were used as welding specimens. The copper wire part is completely welded on the copper substrate and the insulated coating material is driven from welded area to outsides of the wire specimens by high frequency complex vibration.     

基于改进PSO的超声雾化电源频率跟踪研究*

超声波雾化技术由于其良好的雾化效果获得了广泛关注，具有极大的研究价值和应用前景。但是在超声雾化的过程中，由于换能器的温度变化、刚度变化以及在水中的负载变化等因素，会产生谐振频率漂移的现象。当工作频率偏移谐振频率时，将造成换能器的工作效率降低和元器件损坏等问题。针对此问题，设计了基于改进粒子群算法优化PID参数的超声雾化电源频率跟踪算法，并对该算法进行频率跟踪的仿真验证和实验对比，在频率跟踪上实现了更好的效果，使换能器能够稳定工作在谐振状态，提高了电源的利用率。     

离体猪淋巴结组织的高频成像研究

用C扫的超声显微镜系统对猪的淋巴结组织进行了研究,得到了猪的正常淋巴结和出血性淋巴结组织的高频超声图像和声参量值,结果表明:高频超声图像能反映组织结构的变化;猪的出血性淋巴结组织的声散射系数比正常淋巴结组织的小,且随频率的变化而变化,背向散射技术是在高频段进行组织定征的有效手段。     

The dielectric relaxation study of 2(2-alkoxyethoxy)ethanol-water mixtures using time domain reflectometry

Complex permittivity spectra of 2(2-alkoxyethoxy)ethanol-water mixtures for the entire concentration range and at 25 °C have been measured using time domain reflectometry technique up to 30 GHz. The relaxation processes have been obtained by fitting the complex permittivity spectra of the binary mixtures in 2-Debye equation. In glycol ether-water mixtures except for pure water and its rich region the double relaxation times, primary process (τ₁) and secondary process (τ₂) have been observed. The primary relaxation process (τ₁) may be due to cooperative relaxation of the H-bond network of mixture constituents and the secondary relaxation process (τ₂) may be due to its flexible parts attached to the carbon chain. The intra and intermolecular hydrogen bonding of 2(2-alkoxyethoxy)ethanol in pure form as well as in binary mixtures of water have been discussed using Kirkwood correlation factor, Excess dielectric properties and the Bruggeman factor.     

Electronic circuit for high frequency and broad-band ultrasonic pulse-echo operation

A new concept in broad-band ultrasonic flaw detectors is presented, based on a principle which uses only a single fast voltage drop instead of a pulse-like excitation as the driving voltage. This enables unipolar pressure pulses to be generated with acoustically well-matched transducers. The basic electronic circuit essentially consists of Power-MOS-FETs with a fast switching time. With the circuit as described below and a borad-band PVDF transducer, a pulse duration of ultrasonic signals in water shorter than 50 ns is obtained.     

单载波频域均衡压电声透通信研究

研究了单载波频域均衡压电声透通信技术,将系统复杂度集中至介质一侧,并实现高速压电声透通信。分析了压电声透系统信道特性,通过变步长自适应滤波器,有效降低了信道响应的计算量并提高了收敛速度。提出一种改进的单载波频域均衡相关同步算法,可涵盖已有的多种同步方案并提出最佳同步的帧结构判决方案。在此基础上,结合训练序列信息和能量判决方法,提出了针对压电声透通信系统的综合同步算法。同时针对实际应用中的采样起始点偏移和频率偏差累积问题,提出了相应的优化策略。实验中采用中心频率为500 kHz的换能器,在4 cm厚钢板两侧可达到1.298 Mbps的最大传输速率,表明该算法能有效抑制码间干扰,降低误比特率。     

Synthesis of bio-functional nanoparticles from sono-responsive amino acids using high frequency ultrasound

A simple, one-pot high frequency ultrasonication (490 kHz) methodology to convert hydrophobic and amphipathic amino acids into nanostructures was investigated. The approach involved the oxidative coupling of aromatic amino acids (phenylalanine and tryptophan) in aqueous solutions to form high molecular weight dimers and oligomers. The role of cavitation bubble surface and ultrasonic power to trigger the out-of-equilibrium self-assembly of dimers and trimers to spherical and uniform nanostructures with controlled size has been discussed. The synthesized particles exhibited fluorescence in blue, green and red spectral regions and a strong antioxidant activity.     

Experimental study of the hydrodynamic behaviour of a high frequency ultrasonic reactor

In relation to design and modeling of sonochemical reactors, the hydrodynamic behaviour of a high-frequency ultrasonic reactor has been investigated. Residence time distribution (RTD) measurements have been performed by means of a tracer method. The influence of ultrasound on the response to an inlet pulse was evidenced. It was shown that the reactor behaves like a completely stirred tank reactor (CSTR) as soon as ultrasonic irradiation operates. Preliminary observations on acoustic streaming occurring within the reactor will also be presented.     

Development of a 64 channel ultrasonic high frequency linear array imaging system

In order to improve the lateral resolution and extend the field of view of a previously reported 48 element 30 MHz ultrasound linear array and 16-channel digital imaging system, the development of a 256 element 30 MHz linear array and an ultrasound imaging system with increased channel count has been undertaken. This paper reports the design and testing of a 64 channel digital imaging system which consists of an analog front-end pulser/receiver, 64 channels of Time-Gain Compensation (TGC), 64 channels of high-speed digitizer as well as a beamformer. A Personal Computer (PC) is used as the user interface to display real-time images. This system is designed as a platform for the purpose of testing the performance of high frequency linear arrays that have been developed in house. Therefore conventional approaches were taken it its implementation. Flexibility and ease of use are of primary concern whereas consideration of cost-effectiveness and novelty in design are only secondary. Even so, there are many issues at higher frequencies but do not exist at lower frequencies need to be solved. The system provides 64 channels of excitation pulsers while receiving simultaneously at a 20–120 MHz sampling rate to 12-bits. The digitized data from all channels are first fed through Field Programmable Gate Arrays (FPGAs), and then stored in memories. These raw data are accessed by the beamforming processor to re-build the image or to be downloaded to the PC for further processing. The beamformer that applies delays to the echoes of each channel is implemented with the strategy that combines coarse (8.3 ns) and fine delays (2 ns). The coarse delays are integer multiples of the sampling clock rate and are achieved by controlling the write enable pin of the First-In-First-Out (FIFO) memory to obtain valid beamforming data. The fine delays are accomplished with interpolation filters. This system is capable of achieving a maximum frame rate of 50 frames per second. Wire phantom images acquired with this system show a spatial resolution of 146 μm (lateral) and 54 μm (axial). Images with excised rabbit and pig eyeball as well as mouse embryo were also acquired to demonstrate its imaging capability.     

Calculation of high frequency ultrasonic signals for shear wave insonification in solid material

The goal of the theoretical part is to simulate an automatic ultrasonic inspection with contact technique shear wave probes, where the high frequency signals are captured and used to perform a reconstruction based on the synthetic aperture focusing method "SAFT". Therefore the ultrasonic probe, the scanning path and the defects are parameters in a CAD model. The scattering behavior of the defect is calculated by the Kirchhoff approximation in its elastodynamic version. The result of the simulation--the high frequency data--and the result of the SAFT-reconstructions are compared with experimental results on a steel test block with side drilled and flat bottom holes. The model is validated by the experiment. One of the applications of the model is to identify multiple reflections.