Ultrasonic general principle

The general principles of HR-US measurements are simple. A generated electronic signal is transformed by a piezotransducer into the ultrasonic wave travelling through the sample in a 30 fiL to 4 mL cell. Another piezotransducer transforms the received ultrasonic wave into an electronic signal... 

The general principle of acoustic measurements for layer characterization is to follow the ultrasonic eedio reflected on the top of a layer and the one reflected on the bottom of the layer. One can write ... 

Generally two main types of foam detector are used. They work by detecting either changes in electrical capacitance or changes in electrical resistance. Table 4.2 shows the application of foam detectors based on various principles, such as conductance, thermal conductivity, capacitance, ultrasonic rotating disks. 

Since ultrasound in general follows the principles delineated in acoustics, its development naturally reflects the developments in acoustics. For the purpose of this review, only some of the major developments in acoustics and ultrasonics will be highlighted. For in-depth review of this area, readers are referred to a website developed by Dr. Joseph Woo,12 which contains some of the best information on the history of the study of acoustics and biomedical application of ultrasound. 

Ultrasonic-assisted extraction (UAE) is the other common method that accelerates the extraction process [83]. The principle behind the UAE is similar to MAE, where the cell wall is destroyed by ultrasound that leads to active constituents being leached out from ruptured cells without modifying the polysaccharides. In general, UAE is able to extract polysaccharides at lower temperatures, which is about 25-70 °C at 120/300 W of ultrasonic power [89]. The extraction time is between 5 and 40 min. 

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