Ultrasonic pulse

To determine the influence degree on both types of structure and volume of structural heterogeneity on the frequency spectrum characteristics of an ultrasonic pulse, research work using angle beam and straight beam probes was performed... 

Ultrasonic pulses are generated within the sample on the transducer s resonance frequency, pass through sample and are received by the wideband receiver. After received pulse processing in the computer, results analysis is carried out. 

Due to the outer circumference of the silo, about 25 meters, a non- or rarely destructive testing method was needed for the localization. Because the building was still in use, it was only accessable from the exterior side. We chose the ultrasonic pulse-echo-technique as an appropriate way of doing the testing. 

Hillger, W. Inspection of Concrete by Ultrasonic-Pulse-Echo-Technique, In Proceedings of the European Conference on Non Destructive Testing, Nice 1994, pp. II59-II63... 

In general a thickness measurement using ultrasound is done by measuring the time of flight of the ultrasonic pulse and calculating the thickness of the objeet multiplying the time and the known constant sound velocity in the material. 

The common civil engineering seismic testing techniques work on the principles of ultrasonic through transmission (UPV), transient stress wave propagation and reflection (Impact Echo), Ultrasonic Pulse Echo (UPE) and Spectral Analysis of Surface Waves (SASW). 

The use of ultrasonic energy is different in on/off switches and in transmitters. Switches act on the attenuation of the acoustic signal in the gap between two crystals, while transmitters measure the time of flight of the ultrasonic pulse. 

Erequendy, a single ultrasonic transducer serves both as the sender of the ultrasonic pulse and as a receiver for the sound waves reflected from surfaces and interior discontinuities. The receiver transforms the stress pulse back into electrical oscillations. AH of the signals are displayed on an oscilloscope screen for interpretation. Eor a material of length E having a wave speed C, the anomaly shown in Eigure 4 would reflect a signal back to the... 

Phase Velocity Measurements of Polybutadiene Composites Using Ultrasonic Pulses , Rept No BRL-1908 (1976)... 

Figure 4.4 Effect of a free-radical scavenger M-(2-mercaptoproplonyl)-glycine (MPG) on the recovery of contractile function following 15 min of regional ischaemia in the dog heart, (a) MPG infused 1 min before reperfusion, (b) MPG infused 1 min after reperfusion. Contractile function was assessed as changes in ventricular wall thickening measured using an ultrasonic pulsed-Doppler epicardial probe. Note The free radical scavenger MPG can reduce myocardial stunning only when present during the first minute of reperfusion. Redrawn with permission from Bolli et af. (1989).

The discussion above that led to Eqs. (4.2.6 and 4.2.7) assumes that the no-slip condition at the wall of the pipe holds. There is no such assumption in the theory for the spatially resolved measurements. We have recently used a different technique for spatially resolved measurements, ultrasonic pulsed Doppler velocimetry, to determine both the viscosity and wall slip velocity in a food suspension [2]. From a rheological standpoint, the theoretical underpinnings of the ultrasonic technique are the same as for the MRI technique. Flence, there is no reason in principle why MRI can not be used for similar measurements. 

Instrumentation for revealing the presence of bulk quantities of concealed drugs will differ from those developed to find evidence of minute quantities on surfaces. Bulk detection is concerned with amounts ranging from grams to kilograms [4], Bulk detection is done by manual inspection, X-ray, CT scans, and acoustic inspection. X-ray or CT scanners used as bulk detectors have sensitivity of 2-10 g, and suspect items are subsequently confirmed by chemical analysis. Hand-held acoustic inspection instruments such as the Acoustic Inspection Device (AID) and the Ultrasonic Pulse Echo (UPE) developed by Pacific Northwest National Laboratories/Battelle, can be used for analysis of cargo liquids in sealed containers of various sizes within seconds [5]. The acoustical velocity and attenuation of multiple echoes returned to the instrument is evaluated by software which compares the data to the shipping manifest. 

Negishi, K. and Ri, H. U. (1987). Propagation of multi-mode ultrasonic pulses in non-destructive material evaluation. In Ultrasonic spectroscopy and its application to materials Science (Ed. Y. Wada), pp. 70-4. Ministry of Education, Science, and Culture, Japan. [100,102]... 

Sherar, M. D., Noss, M. B., and Foster, F. S. (1987). Ultrasound backscatter microscopy images the internal structure of living tumour spheroids. Nature 330,493-5. [174] Shimada, H. (1987). Propagation of multi-mode ultrasonic pulses in non-destructive material evaluation. In Ultrasonic spectroscopy and its application to Materials science (ed. Y. Wada), pp. 50-6. Ministry of Education, Science and Culture, Japan. [148] Shotton, D. M. (1989). Confocal scanning optical microscopy and its applications for biological specimens. J. Cell. Sci. 94,175-206. [177,200]... 

Another interesting alternative is ultrasonic velocimetry. Sound travels more quickly in solids than liquids, and it is possible to measure the solids content of an oil sample by measuring the time needed for an ultrasonic pulse to move through a fixed pathlength of oil as a function of temperature (McClements and Povey, 1987). Comparisons of ultrasonic with NMR methods have shown the former perform at least as well as the latter, and perform better in the case of low levels of solids (McClements and Povey, 1988). However, because this technique has not been widely adopted or received detailed review by the AOCS or other professional organizations, it is not given the status of a recommended method here. 

A typical experimental configuration consists of a measurement cell which contains the sample, a pulse generator, an ultrasonic transducer and an oscilloscope (Figure 4). The pulse generator produces an electrical pulse of an appropriate frequency and amplitude. This pulse is converted into an ultrasonic pulse by the transducer. It then propagates through the sample until it reaches the far wall of the cell where it is reflected back to the transducer. The... 

Figure 4. Schematic diagram of the experimental configuration for an ultrasonic pulse-echo experiment.

Figure 5. An ultrasonic pulse travels back and forth across the measurement cell so that a series of echoes is observed on the oscilloscope.

Figure 10. Ultrasonic pulse-echo technique for determining the thickness of layers in multilayer materials.

The determination of the thickness of the layers of fat and lean tissue in animal flesh is the most popular use of ultrasound in the food industry at present [5,6]. In fact there are over a hundred references pertaining to this application of ultrasound in the Food Science and Technology Abstracts (1969-1993). In contrast to most other applications of ultrasound in the food industry, which have rarely developed further than use in the laboratory, there are a number of commercial instruments available for grading meat quality [6, 30-32]. This application is based on measurement of time intervals between ultrasonic pulses reflected from boundaries between layers of fat, lean tissue and bone. Ultrasonic techniques have the advantage that they are fairly cheap, easy to operate and give predictions of meat quality of live animals. Other examples of thickness determinations include liquid levels in cans or tanks, thickness of coatings on confectioneries, egg shell thickness. 

Sonic (up to 9,500 Hz) and ultrasonic (10-70 kHz) level sensors operate either by the absorption (attenuation) of acoustic energy as it travels from source to receiver, or by generating an ultrasonic pulse and measuring the time it takes for the echo to return. If the transmitter is mounted at the top of the tank, the pulse travels in the vapor space above the tank contents, and if it is mounted on the bottom, the time of travel reflects the depth of liquid in the tank. In water, at ambient temperature, the ultrasonic pulse travels at 1,505 m/s (4,936 ft/s). 

Ultrasonic level measurement depends on a transducer sending an ultrasonic pulse to the liquid surface which is reflected back to the transducer. Electronics convert the ultrasonic lag time into a distance (D) corresponding to depth. Ultrasonic level measurement is based on the equation... 

Povey, M.J.W., Wilkinson, J.M. 1980. Application of ultrasonic pulse-echo techniques to albumen quality testing - a preliminary report. Br. Poult. Sci. 21, 489-495. 

The energy barrier for the /ra r-rA-isomerization was determined to be 10 kcal moP as determined by ultrasonic pulse techniques <1969JCA713>. It has been shown that the molecule is planar and that >90% of the molecule exists in the A,0-fM-orientation <1985J(P2)1839>. 

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