A study on the etching properties of electron-irradiated plastic track detectors

The variations of the bulk etching rate of electron-bombarded CN, CA, CAB, PC and PET sheets were studied as a function of electron dose and etching temperature. A conclusion was made that in the plastics under study a radiation-damaged region produced, either by an electron beam or a heavily ionizing nuclear particle display, to a certain extent, analogous etching properties. It was shown that the ratio of the etching rates of an electron-bombarded and an unirradiated sheet increases with the increase of the etching temperature for PC and PET, and with the decrease of etching temperature for CN and CA. Similar temperature dependences were obtained for the ratio of track– and bulk-etching rates (i.e. for registration sensitivity) if the plastic sheets were irradiated with heavier nuclear particles. Our results seem to confirm the assumption that the delta electrons may play an important role in the formation of primary nuclear particle tracks in plastic track detectors.     

Quasi pulse-echo ultrasonic technique for flaw classification

One of the important flaw characterization tasks in the field of ultrasonic non-destructive evaluation (NDE) is to provide flaw type information by analysing the flaw responses acquired during an inspection. Here a new quasi pulse-echo ultrasonic classification technique is presented which utilizes the time separation and amplitude difference of mode-converted diffracted signals to distinguish between smooth and sharp-edged flaw geometries. Experiments with cylindrical cavities, surface-breaking fatigue cracks and slag inclusions have been used to test the practicality of this approach. All results of these tests show good consistency in the separation of smooth and sharp-edged flaws, provided that the signal-to-noise ratio is sufficient. Furthermore, the scattering feature used for classification in this method is also verified by detailed elastodynamic scattering calculations.     

Three dimensional evaluation of aluminum plates with wall-thinning by full-field pulse-echo laser ultrasound

We propose a full-field pulse-echo laser ultrasonic wave propagation imager (FF-PE-UPI) for the evaluation of structural defects. The FF-PE-UPI consists of a Q-switched laser for the generation of thermoelastic waves, a laser Doppler vibrometer (LDV) for sensing, and a two-axis translation stage for raster scanning of the combined generation and sensing laser beams. A-scan, B-scan, and C-scan data representations are used for the evaluation of structural defects. Three specimens were tested: a 4-mm aluminum plate with an area of 50% thickness reduction, a 6-mm aluminum plate with an area of 25% thickness reduction, and an 8-mm aluminum plate with engraved letters. The damages on the tested specimens were successfully visualized.     

Piezoelectric wafer active sensor embedded ultrasonics in beams and plates

In this paper we present the results of a systematic theoretical and experimental investigation of the fundamental aspects of using piezoelectric wafe active sensors (PWASs) to achieve embedded ultrasonics in thin-gage beam and plate structures. This investigation opens the path for systematic application of PWASs forin situ health monitoring. After a comprehensive review of the literature, we present the principles of embedded PWASs and their interaction with the host structure. We give a brief review of the Lamb wave principles with emphasis on the understanding the particle motion wave speed/group velocity dispersion. Finite element modeling and experiments on thin-gage beam and plate specimens are presented and analyzed. The axial (S ₀) and flexural (A ₀) wave propagation patterns are simulated and experimentally measured. The group-velocity dispersion curves are validated. The use of the pulse-echo ultrasonic technique with embedded PWASs is illustrated using both finite element simulation and experiments. The importance of using high-frequency waves optimally tuned to the sensor-structure interaction is demonstrated. In conclusion, we discuss the extension of these results toin situ structural health monitoring using embedded ultrasonics.     

Ultrasonic study of nitric acid

I.IntroductionBymeansofu1trasonicwavesthedynamicspecificpropertiesofmolecu1esinmediacouldbeapprehended.Fromthe195ostol96osacousticiansstudiedmo1ecu1aracousticandthermodynamicspecificpropertiesof1iquidsandmixtureswithgreate.th.siasm['-'],andkeptonbringto1ighttheirreportsofrc1evantstudiesinthe1astten-oddyearsl'-'l.overrecentyearstheauthorhasbeenengagedinthemeasurementandstudyofsoundve-locityofsevera1chemica1so1utionsinassociationwithu1trasonicmeasurementstudyofthecon-centrationofsolutionsproduce…     

基于长焦区聚焦换能器的扫描光声乳腺成像技术

报道了一种利用长焦区聚焦超声换能器检测光声信号的扫描光声乳腺成像系统.通过增加聚焦换能器焦区的长度,该技术可以快速实现对大块组织(如乳腺)的光声成像.测试结果表明,该实验系统能够对大块模拟样品中吸收体的位置、尺寸以及光能量吸收情况实现较为准确的成像.另外,实验中,该系统还可便捷地与传统的超声技术相结合,从而实现多模式复合的乳腺癌诊断.初步结果显示了该技术路线在乳腺癌早期诊断应用上的前景. 关键词： 乳腺癌诊断 光声成像 扫描光声层析术 脉冲回波法