Characteristics response time

Examples of Receptor Category Characteristic Response Times... 

It is important to remember that all materials have a characteristic response time, varying from picoseconds for simple liquids like water to years for more traditional solids. If a sample appears to be a mobile liquid as it is disturbed in its container, then it will have a characteristic time of well under a second. If a sample appears to be an immobile solid, then it will have a characteristic time of several minutes or hours. Increasing the temperature of the sample will speed up molecular motion and thus decrease (shorten) the characteristic response time. Cooling the sample will have the opposite effect. If heating the sample is not an option, the only recourse is a long experiment ... 

Whether a polymer exhibits elastic as well as viscous behavior depends in part on the time scale of the imposition of a load or deformation compared to the characteristic response time of the matei ial. This concept is expressed in the dimensionless Deborah number ... 

During periodic operation, the system is forced to follow changes in the input. So-called cycling of the feed is the case where oscillations are applied to the concentrations of the reactor feed. Whether the input is followed perfectly depends on the dynamic behavior of the system. The most important parameter describing the dynamic behavior is the characteristic response time A small value of corresponds to a fast-responding system. Based on the period of the forced oscillation and characteristic response time of the system three different periodic operations can be distinguished [27,45] ... 

J. Relaxed steady-state or sliding regime (T rj. When the input varies rapidly relative to the characteristic response time, the state oscillates with a very small amplitude. The quasi-steady-stale approximation can be applied to the state using the time-averaged value of the control. The performance of the system can be predicted using the performance in comparable steady-state operation. 

Distribution of relaxation times, H(t). In this discussion, using plots of 3/J(t), we shall discuss the distribution of characteristic response times in terms of relaxation times. The relaxation-time spectrum, H(t), can be determined as a first approximation (18) by the following relationship ... 

The characteristic time of this reacting system is t = V/Qfi, where V is the shell-side void volume. The previous equation can be rewritten to relate the characteristic response time of the device and the volume where the biocatalyst is confined to give ... 

A second important aspect of electrochromism is the temporal response under alternating potentials ( 0.55 V). The DG showed sharp and distinct transitions between the colored/oxidized and bleached/reduced state across the entire visible spectrum (Fig. 6.10b). This time-resolved switching behavior was analyzed in more detail at A = 630 nm (Fig. 6.10c). The DG device showed short characteristic response times of 53 ms for the bleaching step and 63 ms for the reverse process, determined by fitting exponential functions to the switching curves. These short response times which are close to video rate (24 frames per second) are enabled by the short ion diffusion distance through the only >= 5 nm thick NiO nanotube wall. 

The long delayed responses of the fuel cell to changes in load have been attributed to mechanical property changes in the polymer. We have initiated measurements of polymer stress relaxation. The stress relaxation and viscoelastic creep of Nafion is both temperature and water concentration dependent. Response times vary from 1 s to 10 s, which can give a wide range of characteristic response times for PEM fuel cells. 

A typical value of the characteristic response time for water in an 800 pm capillary is approximately 20 ms, and so the typical frequencies in a microfluidic circuit are on the order of 100 Hz. 

Figure 4.5. Comparison of the relaxation times (characteristic response times, see Table 4.2), of the reaction mechanisms inside organisms (ij and those of characteristic times of environment in bioreactors (ig), according to Rods (1983).

Apart of giving a sohd thermodynamic basis for the analysis of temperature variation on interfacial studies, we have shown in this chapter how a methodology based on temperature jump perturbation techniques can result in significantly advantages, not only in terms of convenience from the experimental point of view, but also in the possibihty of selectively separate processes based on their different characteristic response time. 

Here as usual, is the characteristic response time of a fitting model such as the... 

In this expression R is the resistance over which the voltage is measured, R is the series resistance of the device, and C is the sum of the capacitances of the photoelectrode and the shunt capacitor. We write R + R, = R and RC being the characteristic response time of the system. 

FIGURE 2 (a) Dependence of the retardation factor, R (Eq. 8), on pH, p j>, and p/fg. (b) Dependence of the characteristic response time, t, on pH, p/ t, and pA p when pH-dependent hydration, buffer diffusivity, and hydrogel thickness are considered. The shaded area represents experimental test conditions. 

Figure 12 is a plot of the experimentally obtained characteristic response times derived from data presented in Fig. lO and compared with the theoretical analysis as expressed in Fig. 2b. Figure 12 is an enlargement of the experimental region (shaded box in Fig. 2b) that compares the theoretical and experimental response times obtained for pH step changes of different magnitudes. The experimental... 

FIGURE 11 Reciprocal of response time, l/Tj jr versus buffer concentration for an electrode array coated with an 80 20 HEMArDMA hydrogel and tested in phosphate buffer (1, 5, 10, 25. 50, and 100 mM) and triethanolamine buffer (5, 25, and 50 mM). Symbols represent characteristic response times for (o) a pH increase from 7.2 to 7.4 in phosphate buffer ( ) a pH decrea.se from 7.4 to 7.2 in phosphate ( ) a pH increase from 7.2 to 7.4 in triethanolamine buffer ( ) a pH decrease from 7.4 to 7.2 in triethanolamine buffer. Standard errors are shown. The solid lines represent linear regressions of the data. 

FIGURE 12 Dependence of on pH-p fp for an electrode array coated with an 80 20 HEMA DMA hydrogel and tested in 100 mM phosphate and 100 mM triethanolamine buffer. Symbols represent characteristic response times for ( ) a device responding to pH increases of 0.20, 0.32, 0.40, and 0.57 pH unit in phosphate buffer ( ) a device responding to pH increases of 0.20, 0.33, 0.44, and 0.60 pH unit in triethanolamine buffer. The solid curves represent the theoretical characteristic response time replotted from Fig. 2b (shaded area) and calculated from Eq. 4. 

Finally, theoretical analysis predicts that the characteristic response time should be directly proportional to the concentration of DMA within the hydrogel // ) when all other variables are held constant. The experimental data of Fig. 9 confirm that when the DMA content in the hydrogel membrane is doubled, the characteristic response time is also doubled. 

The characteristic response times Tc (7.27) of the effect in small fields E/Eu -C 1 are independent of the FLC polarization Ps and the field E, and defined only by the rotational viscosity 7, and the helix pitch Rq... 

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