Pressure pulse method

J. Pressure Pulse Method. Another important method developed by Seuler, Seeker, Laurenceau, Podgorsak, and others [363-368] to determine the charge distribution in an electret is based on the applicatioo of a step-function oompressional wave through the poled sample. The charge distribution is obtained from the time derivative of the voltage... 

FVgura 21 Setup for laser-induced pressure pulse method for charge measuremesi (367). 

Shock Sensitivity Shock-sensitive materials react exothermically when subjected to a pressure pulse. Materials that do not show an exotherm on a DSC or DTA are presumed not to be shock sensitive. Testing methods include ... 

To study the lowest pressure region from about 10 MPa, the acceleration loading pulse method previously used by Setchell [88S01] has been employed. In this case the slowly rising stress pulse from high quality fused quartz is in the form of a ramp in pressure. Hence, a continuous response can be determined to stresses up to about 3 GPa. 

The specific heat at constant pressure, Cpf of the HIP-treated sample with nominal composition LaVg 25 0,7504 was measured over the temperature range 4-400 K by the heat pulse method in a calorimeter that incorporates a feedback system to regulate the temperature of concentric radiation shields surrounding the sample (9). The Cp values are accurate to within 1%, as determined by calibration runs using a polycrystalline copper sample and a sapphire single crystal sample. 

Because of the millisecond time scale for these reactions, pressure-pulse perturbation (Fig. 4.1) with conductivity detection of the response can be used, as in the molybdate adsorption example. Evidently, the inner-sphere surface complexion step for sulfate occurs on time scales very much longer than those for its outer-sphere surface complexation, and therefore it was not observed experimentally with the method used. 

R. Righini and A. Cezairliyan, Pulse Method of Thermal Diffusivity Measurements, A Review , High Temperatures-High Pressures, 5 481-501 (1973). 

The MTO reaction was investigated at 698 K at a weight hourly space velocity (WHSV) of 57-384 g/(gcat h) with a methanol partial pressure of 7.2 kPa. Because the catalyst underwent rapid deactivation, the MTO reaction was investigated by using 3-min interrupted pulses with GC analysis carried out after 2 min for each pulse (this is the integrated pulse method). The time between pulses was about 40 min, allowing for completion of the GC analysis of each pulse. The reactant... 

Pipette and compression methods. The reactants are pre-mixed in the burette B (Fig. 12) and admitted to the RV from the pipette P. Pressure is measured as a function of time, the explosion limit being revealed by the appearance of a flame, a click or a sharp pressure pulse . A variation of this (Fig. 13) is to pre-mix the reactants in the RV and slowly compress the gases by means of the mercury in the burette B . 

The value of a, the compressibility at very low pressure, is well known for many solids. However, b is difficult to determine. Older, static methods are not reliable. Better results are obtained by ultrasonic pulse methods on single crystals, but even here different investigators can differ by 10-20 percent. Table 6.3 shows... 

The sound velocity (/"=l-3 MHz) in superheated ordinary and heavy water was measured by the pulse method. A liquid was superheated in a glass acoustic cell of volume 3 cm. Measurements were made along isotherms. The entry into a metastable region was realized by a pressure release. 

Figure 3. Currents recorded from isolated locust thoracic neuronal somata voltage-clamped by a conventional single-electrode method, a) Application of 1 sec pressure pulses of 10M GABA to a neuron clamped at a series of different holding potentials shows the direction and voltage-dependence of the current underlying the change in membrane potential seen in all cells in response to GABA or muscimol.

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