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除垢超声波传播影响因素的理论研究 总被引:1,自引:0,他引:1
从一维平面波理论入手分析了超声波声压分布特性。依据多普勒频移原理,在声场的运动方程,连续性方程,波动方程的基础上,建立一个超声波在流动的液体中传播的控制方程。根据轴对称模型的实际特点,简化了所得方程,并求出解析解。结果表明流动液体可以产生声波的衰减。液体的黏滞性是产生超声波衰减的重要原因。超声波的频率较高,液体的黏滞性对超声波衰减影响明显。依据黏滞力与速度梯度的关系,建立一个超声波在黏滞液体传播的控制方程,并依据边界条件求出解析解,反映了媒质黏滞性对超声波传播尤其是衰减特性的影响。 相似文献
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近几十年来,由于压电换能原件效率的提高和低噪声的集成元件放大器的应用,超声波传感器在变压器的在线监测及局部放电检测中得到广泛的应用.准确测量变压器油中超声波的传播速度,对变压器局部放电检测研究具有非常重要的意义.根据超声波在液体中传播时能够形成超声光栅的特点,介绍了一种应用分光计精确测量变压器油中超声波速度的方法.实验测得29.3℃时变压器油中超声波速度为1432m/s,与超声手册中标准值符合得很好,相对误差仅为0.5%.该方法有助于提高变压器在线监测及局部放电检测的精确度. 相似文献
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V. Bucur 《Ultrasonics》1983,21(3):116-126
Three stiffness moduli and three shear moduli were determined using an ultrasonic velocity method for 5 mm diameter increment cores bored from living beech trees. The validity of the method was assessed by comparing the results for the increment cores with those for standard specimens loaded in static bending and on cubes tested with ultrasonic transverse waves.Good correlation was found between the elastic constants of the cores and standard specimens. It was noted that the regression equation between the modulus of rupture and the longitudinal stiffness modulus for cores, or between the modulus of rupture for standard specimens and longitudinal velocity in cores, permits one to predict the strength of living tree wood through a simple ultrasonic test. The technique is capable of rapidly detecting the differences between individual characteristics of living trees. 相似文献
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根据Jacobson的液体分子自由程理论和液体声速与分子自由程的关系,推导出多元有机混合液声速的温度系数、压力系数和非线性声参量B/A的计算公式,并根据组成多元有机混合液各组分特性参量(密度、自由程、非线性声参量B/A、等压膨胀系数、等温压缩系数等),利用给出的公式对声速的温度系数、压力系数、非线性声参量B/A进行了数值计算,并将计算结果与实验结果进行了比较. 相似文献
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利用超声波声速测定仪测定出超声波在不同浓度NaCl溶液中的传播速度.实验给出,超声波在NaCl溶液中的传播速度与溶液浓度呈线性关系.溶液温度对超声波波速也有影响,并从理论作了分析研究,给出了合理的解释. 相似文献
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超声是频率高于20 000Hz的声波,由于它遇到障碍物能发生反射、透射,同时具有方向性好、穿透能力强等特征,很快在医学诊断中得到重要应用.本文着重阐述如何利用超声在人体各种组织内的传播特性不同而形成影像,对病理作出诊断提供依据。 相似文献
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超声波波型转换与表面波的检测 总被引:1,自引:0,他引:1
分析了超声波纵波、横波、表面波3种波型的产生条件和声速关系,检测了超声波在固体表面的波型转换,并测量了声表面波的速度,讨论了声表面波在超声延迟线方面的应用. 相似文献
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为了提高超声波测距精度,构建了基于AVR单片机的测距及数据处理系统。分析了超声波测距的原理,以AVR单片机为处理器设计了超声波产生和发射电路、超声波接收和信号处理电路以及温度测量和补偿电路等。针对温度对超声波速度的影响,根据超声波速度与温度的关系,设计了超声波速度补偿算法。为了提高回波时间测量准确性,减小随机噪声及空气中其他杂散播干扰的影响,采用均值数字滤波方法,对计数时间进行处理。实测结果表明,在3cm~400cm范围内,超声波测距系统测量数据准确,最大误差为0.66cm。 相似文献
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为获取液体介质的声速值,设计了一种测定流体声速的实验方法,该方法利用时差式超声波流量计和标准流量校验设备同时对封闭管道中的液体进行流速测量,分别得到流速的测量值和真实值,从而计算出超声波流量计的仪表系数,并以此导出了一定条件下液体介质的声速值随仪表系数的变化关系式.利用该方法测量给出了0.17 MPa下四氧化二氮(N2O4)在7.6-19.4 ℃、偏二甲肼((CH3)2NNH2)在6.5-25.2 ℃范围内的流体声速值,并为其他液体介质的声速测量提供了借鉴.
关键词:
超声波流量计
声速
仪表系数
温度 相似文献
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肌肉组织受力时的弹性特征变化,是其功能特性、健康状态的重要评估参量。该文利用在离体肌肉组织表面施加低频振动引起组织发生形变,在组织内部产生剪切波的方法,经过快速超声成像,通过剪切波图像估计剪切波的传播速度。研究结果表明顺肌纤维方向传播的剪切波速度快于垂直肌纤维方向传播的剪切波速度,剪切波的传播速度随受力的增加而变大,且顺肌纤维方向传播的剪切波速度与受力大小呈正相关。探讨肌纤维不同方向上的剪切波速度,为肌肉组织的病变及疲劳状态的检测和评估提供了参考。 相似文献
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The measurements of ultrasonic velocity and density were made for the ternary mixtures of l-naphthol/2-naphthol with 2-propanone
in benzene at 20, 30 and 40°C in the mole fraction range of 0.00 to 0.05. Adiabatic compressibility and intermolecular free
length have been evaluated using ultrasonic velocity data. The non-linear variation of ultrasonic velocity and allied parameters
with mole fraction indicates solute-solute interactions through hydrogen bonding between unlike molecules. Results of ultrasonic
velocity and density measurements are further supported by FT-IR spectra. The change in transmittance as well as the shift
in the frequency of the representative peak of the OH stretching in FT-IR spectra give inferences about the complex formation. 相似文献
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Hideto Saigusa Makoto Saigusa Iichirou Aino Chiharu Iwasaki Lishu Li Seiji Niimi 《Journal of voice》2006,20(1):38-45
To observe and estimate the movement of the tongue, ultrasonic investigation is the most harmless real-time monitoring procedure for analyzing articulatory movements. Color Doppler ultrasonic imaging is special in that it can only sample a moving target, and it can indicate the velocity and direction of the target by color and brightness in real time. This study assessed and demonstrated the validity of M-mode color Doppler ultrasonic imaging to observe the movements of the tongue during syllable repetition tasks performed by normal subjects and dysarthric patients, those affected by amyotrophic lateral sclerosis, cerebellar ataxia, Parkinsonism, and polymyopathy. When the transducer was set below the jaw, upward movement was indicated by a blue signal and downward movement was indicated by a red one on the screen of the ultrasound machine. We also measured the velocity of the tongue by contrast scale classified by 15 degrees. Thus, we could observe vertical tongue movement by a color-coded pattern after quantitative analysis. The Doppler signal patterns of normal subjects were verified by simultaneous video x-ray fluorography recordings. The findings for dysarthric patients corresponded well with previously reported features analyzed by other methods. Therefore, color Doppler ultrasonic imaging of the tongue is a useful procedure to researchers for clinical speech and voice studies. 相似文献
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现有超声散射统一理论可通过多晶体材料的微观结构和力学特性,实现全频域范围内衰减和相速度的正演建模,但其忽略晶粒尺寸分布的影响,进而降低了正演模型的计算精度.本文对不均匀介质的波动方程进行二阶Keller近似,用全频域格林函数推导介质中的平均波;以截断对数正态分布描述晶粒分布,构建加权的空间相关函数;结合材料的弹性模量协方差,建立含晶粒分布的超声散射统一理论,揭示晶粒分布对超声散射的影响规律;制备304不锈钢试块并开展超声散射实验.结果表明考虑晶粒分布特性后,纵波衰减谱和相速度谱相对于实验结果的相异性降低约49%和64%,横波衰减谱和相速度谱相对于实验结果的相异性降低约12%和4%.可见,本文的统一理论模型能有效修正晶粒分布导致的衰减谱和相速度谱偏差,为晶粒分布反演评价提供理论基础. 相似文献
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The frequency scanning ultrasonic pulse echo reflectometer (FSUPER) is a device which can be used to measure the ultrasonic velocity, attenuation coefficient and specific acoustic impedance of liquid samples as a function of frequency (0.3–6 MHz). 相似文献
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