Thermal measurement techniques indirect

This sensitivity is, of course, the precision of the measurement based on signal noise considerations, and it does not reflect the absolute accuracy of the measurement. As with other noncontact, nondestructive methods, the thermal-wave technique provides an indirect measure of the geometric film thickness, and absolute accuracy must rely on either an accurate knowledge of the relevant physical parameters, or, as is common with the other methods, the use of calibration standards. In analyzing the data presented here we have used a rather complete (and complex) theoretical model to explain our experimental data, and thereby... 

Three years earlier, in 2000, Scrivens and Jackson published a review paper with the same title [5], in which revolutionary technical advances in the field were described. In their words, before the so-called revolution, The majority of mass spectrometric studies of polymer systems required optional extraction of the additives from the polymer followed by a chemical or thermal degradation of the polymer itself. Due to partial degradation, the authors make a distinction between direct measurements and indirect measurements [5]. The mass spectra of many synthetic polymers are discussed, but they limit their review to spectra recorded using three ionization techniques, namely field desorption (FD), electrospray ionization (ESI), and matrix-assisted laser desorption/ionization (MALDI). For MS of synthetic polymers prior to the revolution, the authors refer the reader to other sources. 

There are three indirect, nondestructive measurement techniques to determine thermal resistance acoustic microimaging, x-ray, and thermal test chips. The acoustic microimaging and x-ray methods can be used in both development and production, but the thermal test chip is restricted to development. The first two indirect thermal techniques find the amount of voiding in the thermal path and, through the use of thermal modeling, calculate the thermal resistance. The thermal test chip can only find the thermal resistance capability of the physical design. 

A variety of techniques have been used to determine the extent of crystallinity in a polymer, including X-ray diffraction, density, IR, NMR, and heat of fusion [Sperling, 2001 Wunderlich, 1973], X-ray diffraction is the most direct method but requires the somewhat difficult separation of the crystalline and amorphous scattering envelops. The other methods are indirect methods but are easier to use since one need not be an expert in the field as with X-ray diffraction. Heat of fusion is probably the most often used method since reliable thermal analysis instruments are commercially available and easy to use [Bershtein and Egorov, 1994 Wendlandt, 1986], The difficulty in using thermal analysis (differential scanning calorimetry and differential thermal analysis) or any of the indirect methods is the uncertainty in the values of the quantity measured (e.g., the heat of fusion per gram of sample or density) for 0 and 100% crystalline samples since such samples seldom exist. The best technique is to calibrate the method with samples whose crystallinites have been determined by X-ray diffraction. 

All other experimental TSR techniques used in trap level spectroscopy in semiconductors (insulators) are indirect methods for the determination of trapping parameters. The techniques involve the measurement of phenomena that are due to charge carriers emitted after thermal stimulation from the traps. 

The origin of this lack of uniqueness has been traced to the fact that both TSC and thermoluminescence are only indirect trap-spectroscopic methods. In contrast to TSCAP techniques, the thermal release from traps or the capture of charge carriers in traps is not measured directly. 

For monitoring catalytic (enzymatic) products, various techniques, such as spectrophotometry [32], potentiometry [33,34], coulometry [35,36] and amperometry [37,38], have been proposed. An advantage of these sensors is their high selectivity. However, time and thermal instability of the enzyme, the need of a substrate use and indirect determination of urea (logarithmic dependence of a signal upon concentration while measuring pH) cause difficulties in the use and storage of sensors. 

Heat cannot be directly measured. In most cases heat measurement is made indirectly by using temperature measurement Nevertheless, there are some calorimeters able to measure directly the heat release rate or thermal power. Calorimetry is a very old technique, which was first established by Lavoisier in the 18th century. In the mean time, a huge choice of different calorimeters, using a broad variety of designs and measurement principles, were developed. 

One popular technique for the detection of trace gases in standard (room-temperature) gas samples is the method of photothermal spectroscopy. Photothermal spectroscopy may be classified as an indirect method, since it does not measure the transmission of light used to excite the sample directly, but rather measures the effects that optical absorption has on the sample, specifically thermal changes e.g. see Harren et al. (2000). 

The thermal evaluation of sohd-state devices and integrated circuits (ICs), and VLSI-based packaging takes two forms theoretical analysis and experimental charaaerization. Theoretical analysis utilizes various approaches from simple to complex closed-form analytical solutions and numerical analysis techniques, or a combination of both. Experimental characterization of the device/chip junction/surface temperature (s) of packaged/unpackaged structures takes both direct, infrared microradiometry, or Kquid crystals and thermographic phosphorous, or, to a lesser extent, thermocouples, and indirect (parametric) electrical measurements. 

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