Ultrasonic advantages/disadvantages

Other types are available that use sonic energy (from gas streams), ultrasonic energy (electronic), and electrostatic energy, but they are less commonly used in process industries. See Table 14-11 for a sum-maiy of the advantages/disadvantages of the different type units. An expanded discussion is given by Masters [Spray Drying Handbook, Wiley, New York, (1991)]. 

Manual ultrasonic testing offers the advantages of low equipment cost combined with the flexibility of the human operator to provide good access and complex scanning capability. However, a total reliance on the capabilities of the ultrasonic technician to visualise the physical situation leads to a number of drawbacks, including lack of accuracy and consistency of defect size and location measurements, lack of verification that the required scan coverage has been fully achieved, and lack of consistency in flaw classification. A further disadvantage is that the ultrasonic data is not permanently recorded there is therefore no opportunity for the data to be re-examined at a later date if required. 

The practising chemist has four types of laboratory ultrasonic apparatus which are commercially available. One of these, the whistle reactor, relies on mechanical generation of ultrasonic power whereas the other three - the bath, probe and cup-horn systems - are driven by electromechanical transducers. The construction of such systems is discussed below and a summary of their relative advantages (and disadvantages) in sonochemical usage are summarised in Tab. 7.1. 

Q. Make a list of the advantages and disadvantages of the ultrasonic and Babington-type nebulizers. 

Advantages and disadvantages of uitrasonic baths. Although the cleaning bath Is the piece of ultrasonic equipment most widely used by chemists. It Is not necessarily the most effective. The advantages of using an ultrasonic bath are as follows ... 

Advantages and disadvantages of the ultrasonic nebulizer for the delivery of pharmaceutical compounds to the human respiratory airways are listed in Table 8. The output of drug compound leaving the ultrasonic nebulizer is at a relatively slow velocity compared with the jet nebulizer. Therefore, less patient coordination is required during treatment. 

Bed Level There are several general types of bed level detection instruments ultrasonic, nuclear, float and rod, and reeling (with various sensors). Each has advantages and disadvantages, which are discussed below. There is not a standard bed level sensor that is recommended for all applications. 

Determination. GC two different SFE systems are compared high temperature method in some cases yields a more exhaustive extraction, but also less clean extracts whereas medium temperature may sometimes cause problems with quantitative recoveries, but it yields very clean extracts The use, advantages and disadvantages of silica sorbents, polymeric, functionalized, carbon-based and mixed available sorbents are discussed Determination. LC—MS best conditions, extraction solvent methanol—acetone (1 1, v/v) temperature 50°C pressure 1500 psi two static cycles recoveries >10%. LOD between 1 to 5 /ag/kg loss of volatile molecules is produce at elevated temperatures Determination GC-MS Best conditions extractant methanol temperature lOffC, pressure 100 atm combined with 15 min static and then 10 min dynamic recovery 111% (RSD 4%) and 106% (RSD 5%) extraction efficiency of the PLE was compared with conventional Soxhlet and bath ultrasonication GC-MS an extraction time of 1 h was employed. 

In this chapter, a summary of different techniques of spray pyrolysis with its advantages and disadvantages is presented. The process of spray pyrolysis with ultrasonic excitation is treated separately for which, a theoretical model of structuring and substructuring of aerosol particles, Si02, Ti02, carbonate calciumhydroxyapatite, and phosphor-doped wolfram bronze is developed. 

Other extraction methods like (Ultra-Turrax) blending, ultrasonic, and solvent extractions are available. Most of these techniques show good recoveries for specific matrices, and after optimization of the extraction conditions. Microwave assisted extraction is another promising technique. Good recoveries for PCBs have been obtained. The extraction time is short, and samples can be extracted simultaneously. An overview of advantages and disadvantages of the various extraction techniques is given in Table 2. 

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