Stationary Measurements

Stationary microwave electrochemical measurements can be performed like stationary photoelectrochemical measurements simultaneously with the dynamic plot of photocurrents as a function of the voltage. The reflected photoinduced microwave power is recorded. A simultaneous plot of both photocurrents and microwave conductivity makes sense because the technique allows, as we will see, the determination of interfacial rate constants, flatband potential measurements, and the determination of a variety of interfacial and solid-state parameters. The accuracy increases when the photocurrent and the microwave conductivity are simultaneously determined for the same system. As in ordinary photoelectrochemistry, many parameters (light intensity, concentration of redox systems, temperature, the rotation speed of an electrode, or the pretreatment of an electrode) may be changed to obtain additional information. 

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Though it is easy to determine formally what is a yield stress, in practice its measurement faces essential methodical and principal difficulties. Here two approaches are basically used, stationary and dynamic . During stationary measurements a flow curve is measured and interpretation of the results obtained leads to the definition of a yield stress. An example of such an approach is given in Fig. 1, where experimental points are shown conventionally. They can be obtained under the con-... 

Gillard, P., and Roux, M Study of the Radiation Emitted During the Combustion of Pyrotechnic Charges. Part I Non-Stationary Measurement of the Temperature by Means of a Two-Color Pyrometer, Propellants, Explosives, Pyrotechnics, Vol. 

At 310 °C reaction temperature, a pressure of 1.25 bar and an S/C ratio of 1.9, 80% methanol conversion was achieved in the stainless-steel reactors compared with > 90% for the copper reactor. The carbon monoxide concentration determined in the reformate was 0.5 vol.%. Lower temperature gradients were found for the copper reactor (7 K) than the stainless-steel device (18 K). Non-stationary measurements were carried out at the reformer reactors. The reaction followed the... 

Spectral SERS information of the active spot A can be derived from stationary measurements. The basis of this type of experiment is to center the spot A and to hold it in the excitation focus of the confocal microscope. 

Figure 8.13 shows a sequence of subsequent SERS spectra 1-69 taken at point A. The SERS activity is time dependent and fluctuating. At the very beginning of the stationary measurements, substantial SERS activity of the strong Rhodamin 6 G peaks at 1,510 and 1,270 cm is not visible. With time, SERS activity increasingly develops accompanied by smaller fluctuations. After longer times, the SERS activity again decreases. 

The response time is determined by the ratio d2/DP. Using fast-responding transducers, in stationary measurements a stable signal is obtained within one second up to a few minutes. 

Fig. 71. Dependence of the stationary measuring signal of the electrode depicted in Fig. 69 on urease loading. Urea concentration 0.25 mmol/1.

Fig. 72. Concentration dependence of the stationary measuring signal of a urease-covered Ir-MOS condensator. (Redrawn from Winquist et al., 1986).

With an excess of invertase and GOD in the enzyme membrane the total rate of sucrose determination is limited by the spontaneous mutarotation. Therefore the sensitivity towards sucrose is only about 10% of that for glucose (Scheller and Karsten, 1983). Kinetic (dl/dt) measurement even gives only 1% of the glucose signal at the same sucrose concentration. Application of coimmobilized mutarotase gives rise to an increase of the sensitivity by a factor of 6 for stationary measurement... 

QUASI-STATIONARY MEASUREMENTS OF THE HEAT CONDUCTIVITY OF SYNTHETIC MATERIALS IN THE TEMPERATURE RANGE -180 TO +90 C. //ENGLISH TRANSLATION OF KOLLOID-ZEITSCHRIFT AND ZEITSCHRIFT FUER POLYMERE, 174/2/ 134-42,1961.//... 

The British pendulum was designed with the aim of providing a low-cost and portable apparatus for stationary measurements of slip/skid resistance of a surface in the field or in the laboratory. This test method provides a measure of frictional property, micro-texture in particular, of surfaces and may be used to determine the relative effects of various polishing processes on materials or material combinations. 

As an alternative to on-line gas analysis, simple and reliable techniques such as dynamic measurements [15, 45], stationary measurements [46] and the recirculation method [47] have been developed for on-line OUR determination in mammalian cell cultures. In the dynamic method, a DO profile is dynamically created by changing the gas composition. The DO concentration is increased to a first DO set point by... 

Figure 21.35. Scheme of a setup for a stationary measurement of fluid permeation. 

Another aspect of the structural changes observed in these systems is elucidated by the stationary measurements. The surfactant-based gels behave as non-Newtonian mixtures, and their activation energies can be determined with the well-known Arrhenius equation. If a positive activation energy is acquired, there... 

In practice, the movements of the surfaces that bound the material, rather than the strains or strain rates, are usually measured. If the bottom surface (at z = 0) is kept stationary, measuring the velocity u c(h) of the top surface leads to ... 

Giona, M., S. Cerbelli, F. J. Muzzio, and A. Adrover (1998). Non-uniform stationary measure properties of chaotic area-presCTving dynamical systems, Physica A, 254, 451-465. 

Objective evaluation for furnishing suitable equipment for a TA laboratory, automated data treatment and the choice of most relevant information from possibly parallel figures and successful solution of a given problem, lead to a more responsible direction of the progressive enhancement of research work. The main problem of such quasi-stationary measurements is the intricacy of deciphering all the complex information hidden in a single curve. 

The histogram in Fig. 4 summarized experimental data from the stationary measurements at r= 298 5 K of iron dissolution in acid sulfate and perchlorate solutions. Although there is no apparent reason to believe that the measurements have not been performed with high accuracy and despite the fact that many of the values reported fall into one of two groups, namely, ba = 30 5 mV dec Vqh" = 1 -8 0.2 and = 40 5 mV dec ... 

Sensitivity of modulated excitation (ME) ATR spectroscopy An impression of the sensitivity of stationary measurements was given the last but one section. A limit of 0.2 mAU is suggested. This limit is beaten by one order or magnitude when the ME technique is applied. As mentioned above, the sample must fulfil the condition of a reversible stimulation by a periodically altered external thermodynamic parameter. F3ere, the excellent sensitivity and instrumental stability will be demonstrated, for example, with a chemical modulation experiment performed in liquid water, a very strong absorber in the 3400 and 1640 cm" region. 

The experiments were conducted on a special test rig (Figure 4). The basic principle of the test rig is that the test-rig shaft is coupled with a flywheel and accelerated by an electric motor to a predetermined speed. Then the shaft is braked over the friction surface against the stationary measuring device. Gear shift is by means of a hydraulic cylinder. The force of the hydraulic cylinder is regulated. Lubrication is by oil circulation with temperature control. The test specimen is cormected with the test-rig shaft and with the sensor. 

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