Probes vibrational analysis

Staniforth, J.N. Quincey, S.M. Granulation monitoring in a planetary mixer using a probe vibration analysis technique. Int. J. Pharm. 1986, 32, 177-185. 

The vibrational spectrum of a molecule is determined by its three-dimensional structure and its vibrational force field. An analysis of this [usually infrared (IR) and Raman] spectrum can therefore provide information on the structure and on intramolecular and intermolecular interactions. The more probing the analysis, the more detailed is the information that can be obtained. 

A three-dimensional arbitrary Lagrangian Eulerian finite element code SPLASH has been applied to the flow-induced vibration analysis of the thermocouple probe. Equations of... 

Mechanical E-modulus measurement Vibration analysis Modal analysis Scanning probe microscopy Mostly indirect indications of defects... 

Note, however, that vibration analysis and performance analysis may be linked in many instances. For example, a cracked combustion liner results in a change in TIT and PA calculations. As the cracked metal distxu-hs the airflow and is set into a vibration mode of its own, vibration sensors pick up indication of the cracked hner. Depending on the accuracy of the vibration probes, the sensors may pick up the problem before monitoring of gas path parameters. 

Experienced engineers can do what an expert system does, i.e., arrive at diagnosis of a problem by using indicators from the vibration analysis probes and transducers that are monitoring the gas path. 

The major role of TOF-SARS and SARIS is as surface structure analysis teclmiques which are capable of probing the positions of all elements with an accuracy of <0.1 A. They are sensitive to short-range order, i.e. individual interatomic spacings that are <10 A. They provide a direct measure of the interatomic distances in the first and subsurface layers and a measure of surface periodicity in real space. One of its most important applications is the direct determination of hydrogen adsorption sites by recoiling spectrometry [12, 4T ]. Most other surface structure teclmiques do not detect hydrogen, with the possible exception of He atom scattering and vibrational spectroscopy. 

The use of vibrational spectroscopy for the qualitative analysis of absorbed surface species is first considered, and a Table is then included which summarises a number of the key features of the various quantitative techniques. We then proceed to summarize these in groups depending not upon the probe used (as in the preceding chapters), but in terms of the signal emitted by the specimen which is used in each identification process. 

Due to the nature of the test method, quality by design is an important qualification aspect for in vitro disolution test equipment. The suitability of the apparatus for the dissolu-tion/drug-release testing depends on both the physical and chemical calibrations which qualifies the equipment for further analysis. Besides the geometrical and dimensional accuracy and precision, as described in USP 27 and Ph.Eur., any irregularities such as vibration or undesired agitation by mechanical imperfection are to be avoided. Temperature of the test medium, rotation speed/flow rate, volume, sampling probes, and procedures need to be monitored periodically. 

Note The principal objective of shop verification by response to unbalance is to verify the existence of a critical speed (vibration peak) within tolerance of the calculated value, or if the analysis predicted a highly damped critical speed, the absence of a vibration peak within tolerance of calculated value. Shop verification by this method is feasible only for pumps that have sleeve bearings and are furnished with proximity probe pairs at each journal bearing. 

Adsorption of a specific probe molecule on a catalyst induces changes in the vibrational spectra of surface groups and the adsorbed molecules used to characterize the nature and strength of the basic sites. The analysis of IR spectra of surface species formed by adsorption of probe molecules (e.g., CO, CO2, SO2, pyrrole, chloroform, acetonitrile, alcohols, thiols, boric acid trimethyl ether, acetylenes, ammonia, and pyridine) was reviewed critically by Lavalley (50), who concluded that there is no universally suitable probe molecule for the characterization of basic sites. This limitation results because most of the probe molecules interact with surface sites to form strongly bound complexes, which can cause irreversible changes of the surface. In this section, we review work with some of the probe molecules that are commonly used for characterizing alkaline earth metal oxides. 

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