Measurement techniques advantages /limitations

Point versus Full Field Velocity Measurement Techniques Advantages and Limitations... 

The major advantages of the HTOF technique are that it is not subject to trapping constraints nor the restrictions concerning the absorption depth of conventional photocurrent transient measurements. The principal limitation is that it is limited to photorefractive materials. Malliaras et al. (1995) used the HTOF method to measure mobilities of ternary mixtures of poly(N-vinylcarbazole), 2.4.7-trinitro-9-fluorenone, and 4-(hexyloxy)nitrobenzene. Results obtained by the HTOF method were in good agreement with those obtained by conventional photocurrent transient measurements. 

For multiplex measurements, when compared to fluorescence, SERRS also offers significant advantages. In multiplex measurements fluorescence has the disadvantage that the electronic spectra produced are broad (typically 50 to lOOnm full width at half maximum) and therefore overlap so that the technique is limited to the simultaneous measurement of around four dye labels [69, 77]. In contrast, SERRS uses the vibrational Raman spectrum of the label as a spectroscopic molecular fingerprint As a result the information content of the spectra is much higher and, because the vibrational bands are much narrower (about 1 nm full width at half maximum), spectral overlap is much less of a problem. Thus using SERRS it is possible to readily identify the components of a mixture without extensive separation procedures [78] and it has been estimated in the literature that simultaneous measurement with up to 30 SE(R)RS labels should be possible [79]. 

Experimental descriptors emerge from a fixed experimental design, and their appearance is subject to the physical or chemical limitations of the measurement technique. The advantage of artificial descriptors is that they can be adjusted and fine-tuned easily to fit to a task due to their pure mathematical nature. The only limitation to this approach is the scientist s imagination. However, there are several constraints to be taken into account when selecting or constructing a molecular descriptor. Todeschini and Consonni pointed these out in their book Handbook of Molecular Descriptors [15]. Let us have a closer look at these constraints. 

The thermal property measurement techniques can be categorized as steady-state methods and transient methods. They can also be categorized as invasive and noninvasive techniques. In the following sections, we will focus on several widely used techniques for measuring tissue thermal conductivity or diffusivity. Their advantages and limitations will also be described. 

Xing et al. (2000) compared five different techniques for the measurement of interfacial tension in a model polystyrene (PS)/polyamide-6 (PA-6) system at a constant temperature. The techniques include three dynamic methods (the breaking thread, the imbedded fiber retraction, and the retraction of deformed drop), one equilibrium method (the pendant drop), and a rheological method based on linear viscoelastic measurements. The advantages, the limitations, and the difficulties of each technique were discussed and compared. 

The experimental measurement of topographies aeross the whole seale-size of interest, often extending from the nanometer to the millimeter range, is generally impaired by distortion of the true surfaee profiles [30] (e.g., envelope system [31], limited lateral and/or vertical resolution and accessibility of surface features) and by artefacts (e.g., deformation of surface in contact-type measurements [32], optical artefacts in laser non-contact type measurements because of microgeometry, inclination and reflectivity of the surface [33,34]). The conclusion is that often a combination of different experimental techniques with different advantages/limitations is mandatory in order to get the best possible data [35]. 

This paper will review the advantages and limitations of conventional mass spearometry for the study of energetic materials, describe the STMBMS and time-of-flight (TOF) velocity-spectra measurement techniques, and illustrate the use of these techniques to obtain information on the decomposition of HMX. The following paper will present the results on the decomposition of HMX along with a qualitative model of the processes occurring during the low temperature decomposition of HMX. 

The thermosetting blends require very complicated restrictions, and the limitations and advantages of each type of measurement technique have been reviewed by Halley and Mackay [7]. At this point, only a brief summary is provided ... 

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