Measured transient response

Figure 4.40 shows the simulated output ripple voltage, while Fig. 4.41 shows the simulated output voltage ripple. The measured transient response is shown in Fig. 4.42, while the simulated transient response is shown in Fig. 4.43. 

The subscript m in Fig. 4 represents a measured transient response and the maximum value of 1.0 represents the steady-state flow rate of the reactant or inert, and the steady state formation rate of the product. 

FIGURE 20.36 Tolerance graticule mask for measuring transient response of a visual transmitter. A complete oscillation is fi rst displayed on the screen. The timebase then is expanded, and the signal X-Y position controls are adjusted to shift the trace into the tolerance mask. After [4].)... 

Finally Dill and Zimm have designed a new rheological instrument that can not only perform steady shear, but also measure transient responses, e.g., both stress relaxation and strain relaxation (creep recovery) experiments for dilute solutions. They have investigated the properties of T2 DNA, and studied, for example, the concentration dependence of Results are consistent with the theory of Muthukumar and Freed, and from the value of r, at infinite dilution the molecular weight of the DNA may be determined. 

FIGURE 1.58 Measured transient response at the top of a 1100 kV transmission tower, (a) Injected current and voltage at the top of the tower, (b) Step response of the voltage at the top of the tower. 

In general, it is not easy to measure transient responses in a test field, because there is no power source (AC voltage source) and no voltage reference (no ground terminal). Therefore, one has to prepare all the apparatus required for the measurement. For example, one needs ... 

Measured transient responses at various positions of an artificial tower (fe = 15 m, r=25 mm). 

Transient, or time-resolved, techniques measure tire response of a substance after a rapid perturbation. A swift kick can be provided by any means tliat suddenly moves tire system away from equilibrium—a change in reactant concentration, for instance, or tire photodissociation of a chemical bond. Kinetic properties such as rate constants and amplitudes of chemical reactions or transfonnations of physical state taking place in a material are tlien detennined by measuring tire time course of relaxation to some, possibly new, equilibrium state. Detennining how tire kinetic rate constants vary witli temperature can further yield infonnation about tire tliennodynamic properties (activation entlialpies and entropies) of transition states, tire exceedingly ephemeral species tliat he between reactants, intennediates and products in a chemical reaction. 

Distance-Velocity Lag (Dead-Time Element) The dead-time element, commonly called a distance-velocity lag, is often encountered in process systems. For example, if a temperature-measuring element is located downstream from a heat exchanger, a time delay occurs before the heated fluid leaving the exchanger arrives at the temperature measurement point. If some element of a system produces a dead-time of 0 time units, then an input to that unit,/(t), will be reproduced at the output a.s f t — 0). The transfer function for a pure dead-time element is shown in Fig. 8-17, and the transient response of the element is shown in Fig. 8-18. 

Another major second messenger in cells is calcium ion. Virtually any mammalian cell line can be used to measure transient calcium currents in fluorescence assays when cells are preloaded with an indicator dye that allows monitoring of changes in cytosolic calcium concentration. These responses can be observed in real time, but a characteristic of these responses is that they are transient. This may lead to problems with hemi-equilibria in antagonist studies whereby the maximal responses to agonists may be depressed in the presence of antagonists. These effects are discussed more fully in Chapter 6. 

Tye [38] explained that separator tortuosity is a key property determining the transient response of a separator (and batteries are used in a non steady-state mode) steady-state electrical measurements do not reflect the influence of tortuosity. He recommended that the distribution of tortuosity in separators be considered some pores may have less tortuous paths than others. He showed mathematically that separators with identical average tortuosities and porosities can be distinguished by their unsteady-state behavior if they have different distributions of tortuosity. 

Gal-Or and Hoelscher (G5) have recently developed a fast and simple transient-response method for the measurement of concentration and volumetric mass-transfer coefficients in gas-liquid dispersions. The method involves the use of a transient response to a step change in the composition of the feed gas. The resulting change in the composition of the liquid phase of the dispersion is measured by means of a Clark electrode, which permits the rapid and accurate analysis of oxygen or carbon dioxide concentrations in a gas, in blood, or in any liquid mixture. 

Figure 4.26. Transient response of the rate of CO2 formation and of the catalyst potential during NO reduction by CO on Pt/p"-Al2C>396 upon imposition of fixed current (galvanostatic operation) showing the corresponding (Eq. 4.24) Na coverage on the Pt surface and the maximum measured (Eq. 4.34) promotion index PINa value. T=348°C, inlet composition Pno = Pco = 0.75 kPa. Reprinted with permission from Academic Press.

FIGURE 15.10 Transient response measurements for systems governed by the axial dispersion model (a) closed system (b) open system. 

The following isotopic labeling experiment was performed in order to quantify the contribution of the direct and indirect reaction routes to CO formation After steady-state reaction with CH4/02/He was achieved, an abrupt switch of the feed from CH4/02/He to an isotopic mixture of CH4/1 02/ C 02/He was made, in which the partial pressures of CH4 and 62 were kept exactly the same as in the ordinary CH4/02/He mixture, so as not to disturb the steady-state condition. However, C 02 was added to the isotopic mixture in an amount corresponding to approximately 10-15% of the CO2 produced during reaction of the mixture. The purpose was to measure the production of C 0 due to reforming of CH4 with C 02 only (indirect reaction scheme) under steady-state conditions of the working catalyst surface. Figure 3 shows the transient responses of and C O... 

We have omitted from Fig. 16 the points derived by Seager and Anderson from their measurements above and below room temperature, which also fell near the full line of Fig. 16, though with a slightly smaller slope. These are now believed (Seager and Anderson, 1989) to be less reliable than the room temperature point, because the revised picture of the hydrogenation process throws doubt on the assumption that the surface concentration was nearly temperature independent. This assumption had been used in the analysis because the transient response to interruption of the sample had not been measured at these other temperatures.)... 

In this paper we will first describe a fast-response infrared reactor system which is capable of operating at high temperatures and pressures. We will discuss the reactor cell, the feed system which allows concentration step changes or cycling, and the modifications necessary for converting a commercial infrared spectrophotometer to a high-speed instrument. This modified infrared spectroscopic reactor system was then used to study the dynamics of CO adsorption and desorption over a Pt-alumina catalyst at 723 K (450°C). The measured step responses were analyzed using a transient model which accounts for the kinetics of CO adsorption and desorption, extra- and intrapellet diffusion resistances, surface accumulation of CO, and the dynamics of the infrared cell. Finally, we will briefly discuss some of the transient response (i.e., step and cycled) characteristics of the catalyst under reaction conditions (i.e.,... 

For the examination of the possibility of these reactions, the reaction rates were examined kinetically by using the values of Gy, qre(N20) and qre(C>2) which have been estimated from the results of transient response measurements. Since there are three possible reaction routes (1), (3) and (4), the reaction rates as measured by the formation rates of nitrogen can be tested by checking the fitness of rate equations developed for these different reaction routes. These rate equations are ... 

Our main motivation to develop the specific transient technique of wavefront analysis, presented in detail in (21, 22, 5), was to make feasible the direct separation and direct measurements of individual relaxation steps. As we will show this objective is feasible, because the elements of this technique correspond to integral (therefore amplified) effects of the initial rate, the initial acceleration and the differential accumulative effect. Unfortunately the implication of the space coordinate makes the general mathematical analysis of the transient responses cumbersome, particularly if one has to take into account the axial dispersion effects. But we will show that the mathematical analysis of the fastest wavefront which only will be considered here, is straight forward, because it is limited to ordinary differential equations dispersion effects are important only for large residence times of wavefronts in the system, i.e. for slow waves. We naturally recognize that this technique requires an additional experimental and theoretical effort, but we believe that it is an effective technique for the study of catalysis under technical operating conditions, where the micro- as well as the macrorelaxations above mentioned are equally important. 

The transient response of luminescent substances to modulated excitation can be determined in the frequency domain by measuring the phase delay and the demodulation of the luminescence with respect to the excitation. (14,23 28)... 

Response time. In the literature, response time is usually specified as the time taken for the electrode to reach > 90% of the output. Typical response times are around 30 sec. A fast response time is critical when one is measuring transient phenomena such as oxygen respiration rates in tissue or suspended cells and dynamic measurements of the volumetric mass transfer coefficient in bioreactors. 

Figure 21.15 shows the transient response of the measured pressure shortly before and after the onset of the control. In Fig. 21.15, the apparent frequency of the oscillations was deduced as a function of time by measuring the zero crossing. Two sets of data are plotted since every other zero crossing corresponds roughly to one period of oscillation. The curve fit coincides with the average of the two. Figure 21.15c shows the resulting phase shift associated with the frequency change in Fig. 21.15. At about 40 ms after the control was turned...

For most of the circuits, the transient response of the filter is matched to hardware results. For a select few filters, a network analyzer is utilized to measure the frequency response of the filter. 

Another schematic, which reflects the appropriate ESR of C2 and the DCR of inductor LI, is shown in Fig. 4.26. The schematic includes the circuitry that was used to measure the transient response of the hardware. 

Figure 4.27 Measured UA723 buck regulator transient response.

The transient domain model shown in Fig. 4.33 was used to measure output ripple voltage, transient response, gate voltage, and inductor current. This model properly predicts the cycle-by-cycle switching effects of the regulator. 

Figure 4.60 Measured low drop-out regulator transient response.

Square wave of 10 kHz at a 50% duty cycle used to measure transient loop response AC simulation input to determine filter response (frequency analysis)... 

The transient response of the amplifier was measured by using a 10 kHz square-wave input with a 50% duty cycle. The breadboard results are shown in Fig. 6.27. The bottom trace is the input square wave, while the top trace is the output result. The Micro-Cap, PSpice, and IsSpice results are shown in Figs. 6.28, 6.29, and 6.30, respectively. 

Sample preparation was given elsewhere [2]. Femtosecond fluorescence upconversion and picosecond time-correlated single-photon-counting set-ups were employed for the measurement of the fluorescence transients. The system response (FWHM) of the femtosecond fluorescence up-conversion and time-correlated single-photon-counting setups are 280 fs and 16 ps, respectively [3] The measured transients were fitted to multiexponential functions convoluted with the system response function. After deconvolution the time resolution was 100 fs. In the upconversion experiments, excitation was at 350 nm, the transients were measured from 420 nm upto 680 nm. Experiments were performed under magic angle conditions (to remove the fluorescence intensity effects of rotational motions of the probed molecules), as well as under polarization conditions in order to obtain the time evolution of the fluorescence anisotropy. 

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