Heat pulse technique

Only in the latter case, the measurement is practically adiabatic. Otherwise, it is necessary to extrapolate data to get the effective ST at t = 0 (start of the heat pulse) [2,3], The heat capacity of the addendum (Caddendum = CXh + CSp + CH) can be obtained by a separate measurement without the sample. The heat pulse technique is typically used in the 0.05 1 K temperature range. 

Dry, using a heat pulse technique, showed the effect of the presence of solids on the gas flow both at the entrance region and along the riser [116]. Solids enhance... 

Thermal conductivity, which is an important parameter for thermal assessment of the core behaviour in the safe-storage safety case, is derived from thermal diffusivity measurements which employ a laser heat-pulse technique defined by a British Standard method (BS 7134 Part 4.2, 1990). 

The specific heat of both polymers was measured with the heat pulse technique in semiadiabatic fashion. The thermal conductivity was measured with a top loading He refngerator using the standard procedure. The acoustic properties, sound velocity and attenuation, were measured with the vibrating reed technique [16] in the frequency range (0.2 3) kHz. 

A very common heating sensing technique used in condensed matter is photoacoustic (PA) spectroscopy, which is based on detection of the acoustic waves that are generated after a pulse of light is absorbed by a luminescent system. These acoustic waves are produced in the whole solid sample and in the coupling medium adjacent to the sample as a result of the heat delivered by multiphonon relaxation processes. 

An optical detection technique was developed by Renk 13°) to observe the distribution of vibrational excitations in a ruby sample during 800 nanoseconds after injecting a heat pulse. A spatial resolution of about 1 mm and a 10-9 sec time response were achieved. The result is shown in Fig. 13. The orientational distribution of the pulse was also studied83). From later work120) it has become clear that in Fig. 13 the 29 cm-1 phonon, emanating from the excited 2E-state in ruby, propagates ballistically rather than as a post-relaxation heat wave. 

These same activation energies describe our conductivity data for these samples. Indeed, we can go farther. We have also measured the current-voltage characteristics of semiconducting ITF-TCNQ at higher fields, using a pulsed technique designed to eliminate sample heating effects. The results do... 

Dispersion of Pt, as well as its combinations with Pd or Ir, in H-MOR and H-BEA zeolites were determined by H2 chemisorption using a pulse technique similar to that of Freel . The calcined catalysts were heated in the chemisorption furnace at 500°C for 3h in a H2 flow of 50 cc/min then in a N2 flow of 30 cc/min for 2 h (degassing). The furnace was shut off and the catalyst was cooled to room temperature. H2 was then pulsed into the N2 carrier until saturation (appearance of H2 peaks equivalent to non-chemisorbed pulses). The H2 uptake was calculated as hydrogen atoms adsorbed per total metal atoms on the basis of 1 1 stoichiometry... 

Parameters such as impeller speed and shaft power (in a stirred bioreactor) and fluid velocity are indicators of the degree of mixing and thus play an important role in the control of mass transfer. Impeller speed is easily monitored with a tachometer (electronic or mechanical) [39], but the measurement of shaft power input is not as straightforward. The most common method utilizes a torsion dynamometer attached to the impeller drive however, this technique includes losses due to friction in the drive shaft. Better data can be obtained from balanced strain gauges mounted on the impeller [37]. On-line measurement of the liquid velocity in a flowing or stirred system can be obtained by a heat-pulse method in which a resistance thermometer is used to measure a brief temperature increase caused by an upstream pair of electrodes [43]. Use of this sensor system has been limited to laboratory applications. 

The High Frequency CO2 Pulses technique was carried out at 500, 400, and 25°C by sending pulses of 0.135 pmol of CO2 in He carrier every 10 sec, to the catalyst without soot. Thermal treatments between pulse cycles were also carried out. Typically, the catalyst was heated up to 700°C, and cooled down to 500°C were a new cycle of pulses was carried out. 

Figure 6. The DSC/pulse-heating combination Schematic flow diagram to demonstrate how the different properties are related to each other, using a DSC/pulse-heating combination technique.

Thermal waves have relatively shallow penetration into a material surface flaws tend to cause heat to diffuse at a different rate from that of the surrounding material [68]. In thermographic testing, two techniques exist, the single-sided technique and the through-transmission or double-sided test. In the former, which is more sensitive to flaw depth indication, only the test area scanned is heated (Eig. 4), while the double-sided technique uses the transmission characteristics of a heat pulse passing through a thin section of composite material [64], Temperature patterns at the surface of a composite arc produced... 

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