Ultrasonic mapping

Piezoelectric polymer hydrophones have been proposed as probes (or mapping ultrasonic fields and determining acoustic field parameters in both water and biological media. Among the several PVDF hydrophones developed, the most widely used have been the original hoop membrane configuratioo (spot-poled membrane supported by means of a hoop) (40] and the needle-type probe (41]. While both can be used to assess ultrasonic field patterns in water, only the needle-type probe can be used for bioacoustic measurements, such as in vitro and in vivo evaluatkm of tissue properties. 

Some discontinuities may be identified by a conventional two-dimensional ultrasonic technique, from which the well-known C-scan image is the most popular. The C-scan technique is relatively easy to implement and the results from several NDE studies have been very encouraging [1]. In the case of cylindrical specimens, a circular C-scan image is convenient to show discontinuity information. The circular C-scan image shows the peak amplitude of a back-scattered pulse received in the circular array. The axial scan direction is shown as a function of transducer position in the circular array. The circular C-scan image serves also as an initial step for choosing circular B-scan profiles. The latter provides a mapping between distance to the discontinuity and transducer position in the circular array. 

Hildebrand B.P., Harrington TP. Mapping of materials stress with ultrasonic tomography //Proc. Symp. Microstmctural Characterization and Reliability Strategies - Pittsburgh, 1980. -P. 349-365. 

Of course, under the same operating conditions, the higher the thickness the lower the stress level. Further tests were carried out to map the surface thickness distribution using an ultrasonic precision thickness gauge. It was so verified a deviation of the thickness up to 10% of the nominal value. 

These two transducer pairs are activated alternating. For this purpose an ultrasonic instrument is combined with a two channel multiplexer. Figure 8 presents a modified standard instrument USN52 which also implies a modified software. This system performs four measurements per second - alternating the velocity and the thickness are determined. The probe can be scanned over the surface and in every position both, the velocity and the wall thickness are indicated Using the serial interface of the instrument finally a two-dimensional map of velocity or thickness can be generated. 

Moholkar VS, Sable SP, Pandit AB (2000) Mapping the cavitation intensity in an ultrasonic bath using the acoustic emission. AIChE J 46 684—694... 

He et al. (2002) used an off-line HPLC/CE method to map cancer cell extracts. Frozen ovarian cancer cells (containing 107 cells) were reconstituted in 300 pL of deionized water and placed in an ultrasonic bath to lyse the cells. Then the suspension was centrifuged and the solubilized proteins were collected for HPLC fractionation. The HPLC separation was carried out on an instrument equipped with a RP C-4 column, 250 mm x 4.6 mm, packed with 5-pm spherical silica particles. Extracted proteins were dissolved in 300 pL of DI water, and lOOpL was injected onto the column at a flow rate of 1 mL/min. Buffer A was 0.1% TEA in water and buffer B was 0.1% TFA in acetonitrile. A two-step gradient, 15-30% B in 15 min followed by 30-70% B in 105 min, was used. The column effluent was sampled every minute into a 96-well microtiter plate with the aid of an automatic fraction collector. After collection, the fractions were dried at room temperature under vacuum. The sample in each well was reconstituted before the CE analysis with 10 pL deionized water. The... 

Dinelli, F Assender, H. E Takeda, N., Briggs, G. A. D., and Kolosov, O. V. (1999). Elastic mapping of heterogeneous nanostructures with ultrasonic force microscopy (UFM). Surf. Interface Anal. 27, 562-7. [296, 305]... 

Position of the sampie vessei. Although the position of the sample container with respect to the transducer is not a characteristic variable of US application, it determines the amount of energy that is received by the sample. This variable, exclusive of ultrasonic baths, should be optimized in both DUSAL and CUSAL methods. When only one sample is leached, the precision is not affected provided the sample vessel is always in the same position — cavitational effects can be maximal or not in this situation, however. If several samples are simultaneously treated, then the precision is probably affected because the irradiation profile is not uniform throughout the bath. One example is the DUSAL of cadmium and lead from foods, where the iodine method was used to locate the best position for cavitational effects [5]. This requires the use of mapping techniques. 

Full-Sized Parts. Ultrasonic mapping was done on 1 m x 2 m troughs containing Urethanes A (200 series) and C (701 series) as well as Epoxy X (700 series). The results were interpreted qualitatively and indicated that voids grew with troughs that... 

Figure 1+. Percent void area in san5)le laminates as determined by ultrasonic mapping.

In another (somewhat different) approach, a probability density function (PDF) has been proposed (Moholkar and Pandit, 1997). This is used to map the cavity dynamics in the reaction medium covering all three phases of a cavity s lifetime growth, oscillation, and collapse. An ultrasonic reactor is considered highly efficient if the PDF shows peaks in the collapse regime at all of the locations in the cavitation field. This is an indication that pressure pulses exist throughout the medium and are not restricted to just a few locations. In other words, the cavitational intensity is uniformly distributed. If peaks occur in the growth and collapse regimes, it is desirable to place the reactor inside the sonicated medium at a location where the maximum probability of collapse is indicated. 

Figure 2.6 Principle of ultrasonic scanning of reinforced plastics laminates for defects. Access to both sides is not always possible. Output gives a map of the laminate...

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