The ultrasonic transient field radiated by a normal shear wave probe

The ultrasonic transient field of horizontally polarized shear wave radiated by a 2/2 piezoelectric composite normal probe was analyzed. The analytic field solutions for two different surface force sources were deduced and the transient displacement field distribution on the central cross-section was plotted by numerical calculations. Direct wave and edge wave as well as head wave were observed distinctly in the plots. The experimental results of time domain waveform conformed with the theoretical predictions, which supported the theoretical and numerical results about the transient field of the transducer.     

纵向带状裂隙形貌的逆时偏移超声成像

传统的工业超声成像方法通常只能确定缺陷的位置与横向尺寸,无法获得缺陷的形貌信息.一些特殊的缺陷,如纵向裂纹,是典型的例子.基于多阵元技术,开展了固体介质缺陷逆时偏移超声成像方法的数值与实验研究.针对铝块平底纵裂纹及内部纵裂纹两种传统方法无法有效成像的缺陷,首先开展了单分量逆时偏移成像方法研究,给出了基于数值仿真的逆时偏移成像结果以及基于多阵元超声成像实验系统实验测试的逆时偏移成像结果.进一步开展了基于多分量位移检测与转换横波分离的逆时偏移成像方法研究,并提出了基于新型多分量激光干涉仪进行检测的思路.数值仿真结果证实了多分量逆时偏移图像重建结果可以克服单分量方式的缺点,得到明显优于单分量检测时的图像.     

Experimental and theoretical study of crude oil pretreatment using low-frequency ultrasonic waves

In this work, an ultrasound experimental setup was designed to investigate the feasibility of using low-frequency ultrasonic waves as a substitute to reduce the consumption of chemical demulsifiers in the pretreatment of crude oil. The experiments were planned to study the effects of irradiation time, ultrasonic field intensity and initial water content on the efficiency of separation. The results of experiments showed that by selecting a proper irradiation time and field intensity, it is possible to decrease the usage of demulsifiers by 50%. Moreover, a population balance model was proposed to explicate the experimental data. A hybrid coalescence model was developed to determine the frequency of aggregation. The parameters of the model were estimated by linear regression. The parameter estimation was performed using a parallel execution of the particle swarm optimization algorithm. The results of the model showed a decent agreement with the experimental data.     

残余应力对光弹实验中超声图像的干扰分析

动态光弹成像技术是观测固体内部超声应力场的重要手段,然而样品在制作过程中会产生残余应力,给观测带来一定干扰,特别是缺陷附近的应力集中效应,使得缺陷散射声场的研究更为困难。本文利用线性应力理论分析了超声应力与残余应力的相互关系,并推导出该叠加应力场在光弹系统中的光强表达式,通过实验验证,证明了该理论的可行性。本文结果可为应力集中区域的散射声场分析提供借鉴。     

cMUT阵元的声学分析与环形扫描成像

电容式微机械超声换能器(cMUT)具有宽带宽、灵敏度高、机械阻抗低和与电子电路集成制造等优点.由于超声换能器声场设计的好坏决定了成像质量的优劣,为了明确阵元参数与辐射声场的关系,该文对不同的阵元参数进行了计算仿真.与压电陶瓷超声换能器的结构不同,cMUT阵元是由多个电容单元(cell)并联构成.因此分析了cell的半径...     

Modelling of layered resonators for ultrasonic separation

The potential of ultrasonic techniques for the separation and concentration of particles within a fluid has been investigated in some detail in recent years. Devices for effecting such separation typically consist of a piezoceramic transducer driving into a matching layer, fluid layer and reflector layer. This paper uses an equivalent-circuit transducer model, coupled with acoustic impedance transfer relationships to model such cells with regards to both their electrical characteristics and the strength of the resonance produced under different conditions. The model is compared with experimental results from two different cells and is shown to match experimental values well in terms of electrical characteristics and separator performance. The effects of matching layer thickness are also examined using the model. The importance of the adhesive bonding layer is demonstrated, and it is shown that the model can predict the effects of such a layer. The model is also used to demonstrate the effects of coincident resonances in cell layers and to examine the pressure distribution across cells at key frequencies.     

Biological effects of combined ultrasound and cisplatin treatment on ovarian carcinoma cells

The effects of low-power ultrasound, the anti-cancer drug cisplatin, and their combined application were studied in two lines of human ovarian carcinoma cells, A2780 and A2780cis. Four modes of treatment were used: exposure to ultrasonic field, application of cisplatin, exposure to ultrasound followed by cisplatin, and presence of cisplatin followed by exposure to application ultrasound. Ultrasound was used at intensities of 0.5 W/cm² and 1.0 W/cm² for 10 min, cisplatin was applied at concentrations of 1 μM and 6 μM per cell suspension treated in A2780 and cisplatin-resistant A2780cis cells, respectively. The results of each experimental treatment were assessed by the resultant cell viability related to the viability of control cells, using a standard MTT test. It was shown that a combined effect of ultrasound and cisplatin was more effective than that of ultrasound or cisplatin alone. It also appeared that the order of application played a role, with the cisplatin-ultrasound treatment lowering cell viability more than the ultrasound-cisplatin treatment. It can be assumed that the exposure of cells to a low-power ultrasonic field has an immediate effect on the structure of cell surfaces and, consequently, on entry of cisplatin into the cell.The study also included observations on changes in the cell cycle associated with the treatments used in both cell lines and their evaluation by flow cytometry.     

Optimization of ultrasonic-assisted ultrafiltration process for removing bacterial endotoxin from diammonium glycyrrhizinate using response surface methodology

Ultrasonic-assisted ultrafiltration (UAU) removing bacterial endotoxin from diammonium glycyrrhizinate, was firstly applied to surfactant separation. Separation efficiency was related with four variables, including ultrafiltration molecular weight cut off (MWCO), ultrasonic power, concentration and pH. The SCQ-9200E ultrasonic system was provided for the study with adjustable ultrasonic power 80 W to 800 W, and the ultrasonic frequency was 40 KHz. On the basis of response surface methodology (RSM), the optimal separation conditions were determined to be the ultrafiltration MWCO as 10 kDa, the ultrasonic power as 570 W, diammonium glycyrrhizinate concentration as 150.00 μg/mL and the pH as 4.70. The experimental rejection of bacterial endotoxin was 94.08%, meanwhile the transmittance of diammonium glycyrrhizinate was 93.65%. Based on the ultrasonic power, solution volume, and ultrasonic container size, the experiments with UAU at different power intensities showed that ultrasonic at a power intensity of 57 W/L and the power density of 0.32 W/cm² could solve the separation contradiction between diammonium glycyrrhizinate and bacterial endotoxin. This study indicated that UAU could be an innovation in ultrasonic separation fields, and had a vast range of prospects for making use in pharmaceutical preparation area.     

Separation of calcium and magnesium solvated cations under the action of external periodic electric field on moving solution

The experimental results on the excitation of the phenomenon of selective drift of solvated ions under the action of an external “asymmetric” electric field on a circulating solution of calcium and magnesium chloride salts in polar liquid dielectric, i.e., in water, are presented. The objective of the experiments was the determination of the features of the effect of the field frequency and field strength amplitude on the phenomenon excitation, and the study of operating characteristics of the experimental device, i.e., the separation cell. The dependences of the efficiency of solvated cation separation on the external field frequency and the phenomenon excitation threshold in the field strength in the separation cell are determined.     

Ultrasonic backscatter from flowing whole blood. II: Dependence on frequency and fibrinogen concentration

Earlier studies showed that ultrasonic backscatter from erythrocytes suspended in saline is a function of hematocrit and frequency and that it can be affected by flow disturbance. The experimental data agree well with the theories. Recently, studies have been extended to flowing whole blood. The results indicated that ultrasonic backscatter from flowing whole blood differs from that from saline suspensions of erythrocytes in that it is shear-rate dependent and species dependent. In the present article, data on the dependence of ultrasonic backscatter from flowing whole blood on frequency and on fibrinogen concentration are reported. It was found that ultrasonic backscatter from flowing whole blood also depends on fibrinogen concentration when red blood cell (RBC) aggregation exists. Moreover, when the blood is under conditions that favor RBC aggregation such as low shear rates, high fibrinogen concentration, or high hematocrits, Rayleigh scattering apparently is no longer sufficient to describe its scattering behavior.     

Application of high-power ultrasound to enhance fluid/solid particle separation processes

The separation of fine particles from gases or liquids is a topic of permanent industrial attention. The use of ultrasonic energy to assist conventional separation techniques seems to be very promising. The adequate applications of high-intensity ultrasonic fields may contribute to improve the efficiency and capacity of the separation methods presently used. The specific mechanisms to ultrasonically enhance separation processes basically depend on the medium to be treated. In gas suspensions, where very fine particles have to be removed, ultrasonic action involves agglomeration of particles in order to increase their size and, consequently, to improve collection efficiency of conventional filters. In liquid suspensions, agglomeration is, in general, less efficient than in gases. Nevertheless, the ultrasonic energy is useful to dewater fine-particle high-concentration suspensions such as slurries and sludges. This paper deals with the application of acoustic energy to assist fluid/solid separation processes in gas and liquid suspensions and presents some theoretical and experimental results in specific applications.     

The external magnetic field dependence of RF splitting of57Fe hyperfine lines. NMR + Mössbauer double resonance experiment

We present the results of an experimental investigation of a RF splitting of⁵⁷Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field.     

超声辐照及辐照环境对液体中流场分布特性的影响

研究了超声辐照下液体中声压场分布,模拟了流场分布的特性,模拟结果与利用粒子成像测速仪得到的实验结果相符。进一步研究了声学参数及容器几何环境对流场分布的影响。研究发现,增大超声功率和频率可使流场速度变大:在30~60W范围内,超声功率与流场中最大流速间存在线性关系;在频率为100~472kHz范围内,流场速度大小随频率的升高而增加:在层流区,流速与频率的平方成正比;在湍流区,流速与频率的1/2次方成正比。进一步研究发现,随着换能器到容器壁间距离的增加,流场速度减小。      

Novel applications of ultrasonic atomization in the manufacturing of fine chemicals,pharmaceuticals, and medical devices

Liquid atomization as a fluid disintegration method has been used in many industrial applications such as spray drying, coating, incineration, preparation of emulsions, medical devices, etc. The usage of ultrasonic energy for atomizing liquid is gaining interest as a green and energy-efficient alternative to traditional mechanical atomizers. In the past two decades, efforts have been made to explore new applications of ultrasonic misting for downstream separation of chemicals, e.g., bioethanol, from their aqueous solutions. Downstream separation of a chemical from its aqueous solutions is known to be an energy-intensive process. Conventional distillation is featured by low energy efficiency and inability to separate azeotropic mixtures, and thus novel alternatives, such as ultrasonic separation have been explored to advance the separation technology. Ultrasonic misting has been reported to generate mist and vapor mixture in a gaseous phase that is enriched in solute (e.g., ethanol), under non-thermal, non-equilibrium, and phase change free conditions. This review article takes an in-depth look into the recent advancements in ultrasound-mediated separation of organic molecules, especially bioethanol, from their aqueous solutions. An effort was made to analyze and compare the experimental setups used, mist collection methods, droplet size distribution, and separation mechanism. In addition, the applications of ultrasonic atomization in the production of pharmaceuticals and medical devices are discussed.     

功率超声珩磨磨削区空化声场的建模与仿真研究

通过建立Φ47功率超声珩磨磨削区流体-结构耦合声场的理论模型,采用ANSYS有限元分析软件对磨削区的空化声场进行了仿真分析,得出磨削区二维、三维空化声场的分布情况和声压幅值,并利用超声波功率测量仪对磨削区的空化声场进行模拟实验测量。结果表明:在谐振频率18.6 kHz下,声场主要集中在油石的中部,二维和三维声场的声压最大值分别为1.39 MPa和1.47 MPa,与实验测得声压最大值1.3 MPa在同一个数量级,为进一步研究功率超声珩磨空化效应提供理论和实验的基础。      

Z箍缩Al等离子体X辐射谱线的分离及电子温度的提取

以"强光一号"Z箍缩装置10174发次光谱诊断实验结果为例,描述了一种对Z箍缩等离子体X辐射光谱分离提纯、诊断的方法.对连续辐射谱和特征辐射线谱进行分离,并从连续辐射谱和特征辐射线谱中提取了等离子体电子温度信息.结果显示:等离子体连续谱主要由等离子体中心的高温区(Te=290.7 eV±1.2 eV)和温度较低的壳层区域(Te=95.3 eV±8.3 eV)两部分叠加而成;特征辐射线谱主要反映了等离子体中心的高温区信息,根据非局域热动平衡模型计算提取的电子温度约为299—313 eV,与连续谱诊断结果基本符合.     

超声波在磁性液体中的传播特性

本文报道超声波在磁性液体中的传播特性,首先研究了磁化状态建立与消失的弛豫过程,弛豫时间约20min,为了保证平衡状态下进行测量,所有数据均为附加磁场60min后进行的测量,然后在f=4HMz下,测量了φ=0,π/2的声速与磁场的关系,声速与磁性液体中磁性颗粒浓度的关系,对有关理论进行了解释。 关键词：     

Spatiotemporal measurement using L-band ESR-CT system for water sonolysis in the presence of 1-Hydroxy-2,2,5,5-tetramethyl-3-imidazoline-3-oxide

When using ESR to measure the radicals generated by ultrasound, it is necessary to extract a solution and place it in the ESR system. To avoid this process, we incorporated an ultrasonic reaction cell in an L-band ESR-CT system, producing a system that allows the detection of the concentration of radicals during ultrasonic irradiation. This system was used to measure the time and space dependences of OH radicals generated by ultrasonic irradiation. When a 10 ml aqueous solution of 1-hydroxy-2,2,5,5-tetramethyl-3-imidazoline-3-oxide (HTIO) was irradiated with ultrasound, it was found that the generation of radicals was clearly shown in a CT image after a period of 10 min. It was also found that continued irradiation resulted in an increased concentration of radicals. In addition to this system, an X-band ESR system was also used to measure the concentration of OH radicals generated, and the results of both systems were then compared. Both results are very similar, showing that the proposed system, which was realized by incorporating an ultrasonic irradiation cell in the L-band ESR-CT system, operated properly. Because this system allows the measurement of sonochemical reactions in an opaque cell or an opaque solution such as blood and industrial wastewater, it is a very useful measurement system for achieving the applying of sonochemistry to the medical engineering field.     

Sensitivity enhancement in membrane separation flow injection analysis by ultrasound

The effect of ultrasound on gas-diffusion and pervaporation flow injection separation was investigated. Ammonia and three aliphatic amines (propylamine, tri-ethylamine and di-n-butylamine) with different volatility and surface activity were used as model analytes. Under the experimental conditions used, sonication did not enhance gas-diffusion separation efficiency and resulted in up to 62% improvement in pervaporation mass transfer. Based on these findings and taking into account the surface activity of the analytes studied which decreased with their molecular mass it was postulated that ultrasound-induced surface rippling was primarily responsible for the enhanced evaporation in the donor chamber of the pervaporation cell. The results reported in this paper suggest that ultrasonic pervaporation separation could extend the applicability of this on-line flow injection separation technique to the direct determination of higher molecular mass volatile and semi-volatile analytes in 'dirty' samples.     

Shear Wave Field Radiated by an Electromagnetic Acoustic Transducer

The horizontally polarized ultrasonic shear wave field emitted by an electromagnetic acoustic transducer （EMAT） is studied by the surface force distribution on the EMAT approximately described as an inhomogeneous horizontal shear force. The shear wave directivity pattern is plotted by numerical calculations based on our strictly analytic solutions of the wave field we presented previously. An experimental system of EMAT generation and piezoelectric transducer reception is set up to check the predictions of the theoretical wave field by measuring the ultrasonic signals through aluminium block. The directivity pattern of the wave field obtained from the experimental results conforms the theoretical prediction, which lays a foundation for engineering applications of EMATs.