共查询到18条相似文献,搜索用时 125 毫秒
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微纳相控线阵超声换能器参数(阵元数目、阵元宽度及阵元间距)直接影响其横向声场分布,而其横向声场分布是能否实现高成像分辨率、大探测深度的决定性因素,也是制备换能器的主要依据。该文利用数值模拟研究微纳相控线阵超声换能器阵元参数对其横向声场中主瓣强度、-3 dB主瓣宽度、第一级旁瓣及栅瓣的影响。结果表明,主瓣强度随着阵元数目增加而增大,随阵元间距减小而增大,随着阵元宽度的增大呈现先增大后减小的趋势;-3 dB主瓣宽度随着阵元数目和阵元间距的增大而减小,随着阵元宽度的减小而减小;此外,减小阵元数目、减小阵元间距或增大阵元宽度均可以抑制旁瓣;栅瓣在阵元间距满足一定条件时可以完全消除。通过这些研究为微纳相控线阵超声换能器的优化设计与制备提供理论参考。 相似文献
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为考察基于时间反转方法的高强度聚焦超声治疗在预设目标点处的组织损伤情况,使用三维有限差分算法求解Westervelt方程,建立非线性声波传播数值模型,采用97阵元相控阵结合虚拟源的时间反转方法进行超声聚焦,分析其形成的声场和热场,并考察目标点偏离轴线时的组织损伤形成规律。结果表明随着目标点偏轴距离的增大,声压旁瓣开始增多。旁瓣的温升较低,不足以形成组织损伤。时间反转方法可用于多点聚焦,在一定的范围内,形成多点目标损伤而不产生额外的周围组织损伤。同时多点聚焦可以形成一个较大的损伤区域,减少超声治疗时间。 相似文献
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针对线性相控阵列在固体介质中的声场聚焦特性及参数优化问题,该文给出了一个线性阵列的纵波瞬态聚焦声场模型。数值结果表明,当阵元被短时脉冲信号激励时,瞬态聚焦声场中不会形成栅瓣,突破了传统稳态理论模型中对阵元间距的限制;同时由于横纵波在聚焦区域内可完全分离,声束旁瓣的幅值也得到了抑制。其次,增大阵元间距能够显著提高聚焦性能,但会导致聚焦声场能量减弱,综合考虑后,最佳的阵元间距为一个波长左右。并且发现,阵元宽度对于聚焦性能几乎没有影响,但宽阵元能够提高聚焦能量。此外,受到纵波激发特性的影响,使得相控阵只能在低偏转角处获得理想的纵波聚焦性能。最后,采用不同阵元间距的相控阵探头对试块进行成像实验,观察到大阵元间距可以显著改善缺陷成像分辨率,从而验证了理论分析的结果。 相似文献
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采用3种随机排列策略形成相控阵元线性排列结构抑制高强度聚焦超声(HIFU)相控阵栅瓣。第1种和第2种策略中阵元基于规则排列随机移动,而第3种策略中阵元则直接进行随机移动,阵元可移动范围依次为:第1种<第2种<第3种。采用瑞利积分和非线性Westervelt方程分别计算了3种策略对应随机相控阵产生的线性和非线性声场,并通过归一化栅瓣最大声压、归一化栅瓣平均声强和归一化旁瓣平均声强3个参量,对栅瓣抑制效果进行评价。结果表明:线性声场中,阵元可移动范围的增加有利于栅瓣抑制,3种随机策略的归一化栅瓣最大声压相比规则排列分别降低30.7%,53.8%和55.8%;非线性声场中对于同一种随机排列策略,随机度的增加可以改善栅瓣抑制效果。例如,第3种随机策略在随机度为0.9时正负压的归一化栅瓣最大声压相比规则排列分别降低55.6%和54.8%。进一步讨论了焦点偏移时随机相控阵的非线性声场,以-8 dB作为栅瓣的安全标准,第2种和第3种随机策略可以满足要求,横向偏移分别为6 mm和10 mm。本文的工作为抑制栅瓣提供了新思路,有利于随机HIFU相控阵的设计优化。 相似文献
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基于高分辨的CT数据建立了非均匀颅骨仿真模型,该模型引入了颅骨的声衰减系数,深入研究和分析了声波时间反转法和超声相控阵法在颅脑中的聚焦方法及效果。颅骨具有较强的声波衰减特性,使用时间反转聚焦时需要进行幅度补偿,对于0.7MHz的频率信号,幅度补偿后的时间反转聚焦声场主瓣宽度窄、旁瓣低,焦点处声场比无幅度补偿的时间反转法提高8.86dB,比超声相控阵聚焦法提高7.89dB,具有很好的空间聚焦精度和聚焦效率。研究了颅骨衰减系数、声场焦点位置、声波频率、换能器阵列位置和方位等参数对聚焦声场的影响,结果表明,幅度补偿时间反转法比相控阵法具有更低的旁瓣,且高频时的聚焦效果比相控阵好,相控阵聚焦对换能器阵列的位置和方位比较敏感,而时间反转经颅超声聚焦对声传播路径和入射角具有更高的鲁棒性。 相似文献
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《物理学报》2021,(11)
本文基于求解单频声波方程近似解的方法,得到了非线性声场中谐波的声压与介质性质、初始声压幅值及频率之间的定量关系.并对两列相对声压幅值和相对频率不同情况下的声场分布进行了研究.通过分析单、双频声源辐射场中的谐波分布和传播规律发现:在非线性声场中会不断地出现新的谐波,激发的各阶谐波随着声波传播距离的增大逐渐增强而后减弱.在声源的附近,谐波的声压随基波声压振幅的增大而增大;但在基波的频率增大时反而会减小.在输入总声能相同的情况下,与单频声场相比双频声源辐射场的声能量分布较均匀,声的传播距离较大,远场中的谐波含量较大.结果表明,基波的频率越高,衰减得越快,谐波的积累越缓慢;声压的极值越大,基波声能量转移得越多,产生的谐波越多,基波的衰减越快,声压对远场声能的负效应增大;如果改用多频声源,并适当地控制输入声波的组成成分,可以达到改善声场分布均匀性、增大声辐射距离的效果. 相似文献
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从理论上导出了传声器失配误差对适用于任意阵元数的一阶和二阶差分传声器圆阵的主瓣指向影响规律。揭示了传声器相位误差可造成一阶差分传声器圆阵主瓣指向产生反转现象,是影响其主瓣指向的主要因素。而对于二阶差分传声器圆阵,传声器相位误差和增益误差均可导致其主瓣指向产生反转现象和严重指向误差,进而造成阵列指向性因子严重下降,尤其在低频处失配误差的影响更为显著。然后给出了确保差分传声器圆阵主瓣指向正确时阵列设计参数所需满足的条件,并在此基础上进行了传声器失配误差的容差分析。分析结果表明,随着阵元数增多,失配误差的容差范围增大,差分传声器圆阵对传声器失配误差的敏感性相应降低。 相似文献
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针对传统超声探头焦距固定,检测位置的改变就要更换相应焦距的探头而影响检测效率的问题,提出一种基于超声相控阵换能器的环焊缝缺陷检测方法。而超声相控阵具有电子偏转和电子聚焦特性,能在不移动的情况下发射偏转聚焦超声束,有效地解决了上述问题。首先基于超声相控线阵换能器的声场特点,采用数值分析方法,研究了影响声束偏转聚焦性能的几个主要参数。然后给出了与超声相控阵换能器相连接的多通道数据采集系统结构。介绍了单通道声信号的硬件结构及相应的信号处理方法,实现了对换能器中单个阵元的精确延时的控制。实验结果表明,优化设计的超声相控线阵换能器具有较高的检测精度和检测效率。 相似文献
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Radiation Acoustic Field of a Linear Phased Array on a Cylindrical Surface 总被引:6,自引:0,他引:6 下载免费PDF全文
A new linear ultrasonic phased array fixed on a cylindrical surface is designed. This kind of the cylindrical phased array can meet the specific requirements of the application in testing pipe quality inside pipes. Using the transducer, we can not only avoid mechanical rotating but also test the quality of any point in a pipe by ultrasonic phase array technology. The focused acoustic field distributions in the axial, radial and tangential directions of the transducer are investigated theoretically by numerical simulation. The energy flux density, the width of the main lobe, the imaging resolution, the grating lobe elimination and other characteristics are analysed. The effect of the focal distance, effective aperture, transducer radius, number of total element, and steering angle on the acoustic field distribution is also studied.thoroughly. Many important results are obtained. 相似文献
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由于良好的声束偏转与聚焦特性,超声相控阵已经广泛应用于多层固体介质的缺陷检测。当超声束经过多层介质时,由于反射、透射以及模式转换的存在,多种声束存在于这种结构中,使得声场分析变得复杂。为了提高多层介质检测的准确性,有必要对超声声场的分布规律进行深入地了解。该文结合高斯声束等效点源模型以及射线追踪法,给出了相控阵声源在多层固体介质中激发声场的仿真方法,并且模拟计算了一维线型相控阵在楔块-铝-黄铜-钢四层固体介质中的辐射声场。通过对不同延时法则的计算,实现了声波在这种复杂介质中的偏转与聚焦,进而研究了不同焦点处聚焦声场的分布。结果表明:相控阵方法能使聚焦点处的声场幅值增大,能量集中,提高了检测分辨率;不同聚焦点处声场聚焦效果不同,实际检测时应根据检测区域结构及位置特点,合理放置相控阵换能器。与瑞利积分法的比较表明,该文的仿真方法适用于多层介质相控阵声场的计算。 相似文献
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Numerical simulations of partial elements excitation for hemispherical high-intensity focused ultrasound phased transducer 下载免费PDF全文
Yanqiu Zhang 《中国物理 B》2021,30(7):78704-078704
The hemispherical phased transducer maximizes the coverage of the skull and the ultrasonic energy per unit area of the skull is minimized, thereby reducing the risk of skull burns, but the transducer has a small focal area adjustment range, increasing the focal length of treatment is an urgent question for this type of transducer. In this paper, a three-dimensional high-intensity focused ultrasound (HIFU) transcranial propagation model is established based on the human head structure. The finite difference time domain (FDTD) is combined with the Westervelt acoustic wave nonlinear propagation equation and Penne's biological heat conduction equation for numerical simulation of the sound pressure field and temperature field. Forming a treatable focal area in a small-opening hemispherical transducer with a small amount of numerical simulation calculation focusing at a set position to determine the minimum partial excitation area ratio of focusing. And then, applying these preliminary results to a large-opening diameter hemispherical transducer and the temperature field formed by it or full excitation is studied. The results show that the focus area with the excitation area ratio of less than 22% moves forward to the transducer side when the excitation sound is formed. When the excitation area ratio is greater than or equal to 23%, it focuses at the set position. In the case of partial incentives, using 23% of the partial array, the adjustable range of the treatable focal area formed in the three-dimensional space is larger than that of the full excitation. 相似文献
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Numerical study on scanning radiation acoustic field in formations generated from a borehole 总被引:9,自引:0,他引:9
CHE Xiaohua ZHANG Hailan QIAO Wenxiao & JU Xiaodong . Institute of Acoustics Chinese Academy of Sciences Beijing China . Faculty of Natural Resources & Information Technology University of Petroleum Beijing China 《中国科学G辑(英文版)》2005,48(2)
The directivity of acoustic transducers used in conventional acoustic logging tools is uncontrollable[1,2], which inevitably affects investigation depth and resolution. At present, deep and wide range of investigation in petroleum exploration is urgently re- quired. It is important to improve the exploration capability to find more complex and fine reservoirs[3], for which the direction of the radiated acoustic energy is a direct factor. Acoustic field in the formations generated by the source… 相似文献
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Considering the complexity of common phased array, and relatively slow mechanical scanning of the single transducer, a new-style transducer that has a changeable focus and a simple control system is needed. The sector phased array transducer, which has many advantages including easy fabrication, movable focus, and a simple control system, can reach the desired requirements. This paper has demonstrated its feasibility by the computation of acoustic field in (y, z) plane. The 24-element phased array, of which the length of the focal region is about 10 mm, and the maximum lateral diameter is about 1.5 mm, can accomplish the adjustment of the focus position. The maximum lateral displacement is 1.5 mm, and the treatment area is about 9 multiples of the single transducer, and only six power amplifiers are needed. 相似文献
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Acoustic power measurement of high intensity focused ultrasound in medicine based on radiation force
How to measure the acoustic power of HIFU is one of the most important tasks in its medical application. In the paper a whole series of formula for calculating the radiation force related to the acoustic power radiated by a single element focusing transducer and by the focusing transducer array were given. Various system of radiation force balance (RFB) to measure the acoustic power of HIFU in medicine were designed and applied in China. In high power experiments, the dependence of radiation force acting the absorbing target on the target position at the beam axis of focusing transducer was fined. There is a peak value of "radiation force" acting the absorbing target in the focal region when the acoustic power through the focal plane exceeds some threshold. In order to avoid this big measurement error caused by the 'peak effect' in focal region, the distance between the absorbing target of RFB and the focusing transducer or transducer array was defined to be equal to or less than 0.7 times of the focal length in the National Standard of China for the measurements of acoustic power and field characteristics of HIFU. More than six different therapeutic equipments of HIFU have been examined by RFB for measuring the acoustic power since 1998. These results show that RFB with the absorbing target is valid in the acoustic power range up to 500W with good linearity for the drive voltage squared of focusing transducer or array. The uncertainty of measurement is within +/-15%. 相似文献