Overshoot phenomenon

Overshoot of the steady state level is an intriguing feature of many of the transient current responses. This behavior occurs following both opening and closing the lightbox shutter. The following observations characterize this "overshoot" phenomena ... 

According to the Scott equation, plotting ln(ti/2) versus ln(l/FN) should give a straight line. This is what Leider (50) observed with a series of fluids in the Scott equation range. However, Leider and Bird (49) extended the analysis to include stress overshoot phenomena by using a semiempirical expression for the shear stress ... 

From the view-point of determination of recombination rate coefficients using measurements of H atom concentrations for example, the overshoot phenomena mentioned do not invalidate the p.e. approach, since the concentrations of the overshooting species are too low to contribute to the overall radical concentrations in the recombination region. It is more likely that the conditions in many actual flames are such that the p.e. assumption will predict slightly too rapid a recombination rate from a given set of rate coefficients. In some circumstances, however, O atom overshoot may influence the accuracy of prediction of rates of O atom reactions in flames using the p.e. assumptions. This may need careful consideration, for example, before attempting to calculate nitric oxide formation by the Zeldovich mechanism. 

EFFECTS IN PHYSICAF DEPENDENCE In subjects who are dependent on morphinelike opioids, small subcutaneous doses of naloxone (0.5 mg) precipitate a moderate-to-severe withdrawal syndrome that is very similar to that seen after abrupt withdrawal of opioids, except that the syndrome appears within minutes of administration and subsides in 2 hours. The severity and duration of the syndrome are related to the dose of the antagonist and to the degree and type of dependence. Higher doses of naloxone will precipitate a withdrawal syndrome in patients dependent on pentazocine, butorphanol, or nalbuphine. Naloxone produces overshoot phenomena suggestive of early acute physical dependence 6-24 hours after a single dose of a /i agonist. 

The flowsheet is decomposed into component parts. These are MIMO subsections of the flowsheet that are approximated by matrices of low-order transfer functions (usually first order with dead time). This decomposition permits process units to be modeled in sufficient detail, allowing inverse response and overshoot phenomena to be represented. 

Intermediate periodic operation lies between both extremes and covers systems in which the response time is of the same order as the imposed function cycle time so that resonance is possible. Here the state of the mechanism changes dynamically and is not directly related to the environmental conditions at the moment considered. Intermediate periodic operations encompass semibatch periodic operations, selectivity in periodically forced CSTRs, cycled reactors with heterogeneous catalysts, and non-steady-state biofilm reactors (e.g., Rittmann and McCarty, 1981). Lag, overshoot phenomena, and oscillations can typically occur. Biological reactor operation will basically fall into this latter class of operation, and balanced growth must be distinguished from steady-state growth (Barford et al., 1982). 

Widespread evidence for hysteresis and overshoot phenomena, such as displayed in Figure 13, indicates that structural relaxation is nonexponential even for small departures for which the linear approximation is adequate, and the time dependence may be represented by the function (7-10,36,113-115)... 

Sevastianov et al.73,74) have developed a model which considers the effect of surface heterogeniety on the adsorption process. They define centers of irreversible adsorption , labeled P, and centers of irreversible desorption , labeled D. They argue, in agreement with Soderquist and Walton, that desorbed material is conformationally altered and thus cannot readsorb — hence desorption is irreversible. The results of this model are given as Fig. 14, taken from Ref. 7J). The model also includes the case where adsorption may be transport limited. The model fits commonly observed adsorption data, including the overshoot phenomenon (Fig. 14, top) (discussed in Ref. 72)) to be discussed later. 

The carbohydrate resources of cod, during experimental refeeding after severe starvation, increase to values many times higher than in cod fed continuously throughout the experiment the overshoot phenomenon ... 

For fast squeezing flow we would need a constitutive equation that accounts for the stress overshoot phenomenon. 

Fig. 7. Sketch showing stress overshoot phenomenon exhibited by rigid dumbbell...

The expression for the shear stress contains terms which are similar to those in the expression for stress growth at the inception of steady shearing ( 11) in which an overshoot occurs. Such an overshoot phenomenon has been observed experimentally by Marsh (54) and by Warner (74). 

However expansions of the type of Eq. (20.4) would not be able to explain such phenomena as stress relaxation ( 10) or the overshoot phenomenon in stress growth ( 11). It might prove fruitful to explore alternate methods of obtaining constitutive equations which would not be of the form of Eq. (20.4), i.e. stress = function of y and its derivatives. After all, time derivatives of stress could appear [as in Eq. (4.23)], or stress could be given as an integral over the strain history. This question of the connection between dumbbell models and continuum mechanics has been studied extensively in a series of papers by Giesekus (3/). 

Fig. 7.17B). This indicates that the source of the double overshoot phenomenon is simpler than previously thought. Figure 7.19 shows the concentrations of the various isotopic species of DAP during the double overshoot simulation shown in Fig. 7.17B. The peaks of the two overshoots are indicated in Fig. 7.19, demonstrating... 

The effect of CPH-treatment upon the Na -depen-dent transport of the amino acid L-alanine was investigated [75]. The results of these studies showed that Na+-dependent transport of L-alanine was also reduced by the treatment with CPH and the overshoot phenomenon completely eliminated (Figure 7). In con-... 

After a single alcohol binge, damaged mtDNA molecules are quickly repaired and resynthesized de novo from intact mtDNA templates. mtDNA levels are quickly restored, with even an overshoot phenomenon at 24 h (Mansouri et al. 1999). In contrast, after 4 days of a once-a-day binge, the accumulation of... 

As the mathematical representation of the complete overshoot curve is very complicated, only the amplitude of the peak is usually taken as an indicator of secondary active transport, provided that other causes of an overshoot phenomenon, such as osmotic swelling or temporary changes in membrane potential, can be excluded. 

The first part of the production term corresponds with the production term of the standard / - model. Notice that the second production term is related to the time scale r. The introduction of this additional term enables the energy transfer to respond more efficiently to the mean strain than the standard k-e model does. Thus, r enables the development of a field of suppressing the well-known overshoot phenomenon of the turbulent kinetic energy k. This overshoot appears, when the standard k- model is applied to flow conditions with large values of mean strain [4,7,8]. 

By using the affinity of [0.01 0.03] instead of [0.1 0.3] kPa , we have a low affmity system and Figure 10.5-1 also shows the fractional uptake of this low affinity system. The overshoot phenomenon is again observed but the degree of overshoot is not as significant as that in the high affmity system. 

Winfield, )., leropoulos, I., and Greenman, J. (2010) The overshoot phenomenon as a function of internal resistance in microbial fuel cells. J. Biotechnol., 150 (Suppl. 1), 23—23. 

Fig. 26. Effect of strain rate on the stress-time (double logarithmic plot) behavior for a concentrated polymer solution, showing the increasing strength of the stress overshoot phenomenon with increasing strain rate. After Zapas and Phillips (81), with permission.

Y. Y. Wang and S.-Q. Wang. Exploring stress overshoot phenomenon upon startup deformation of entangled linear polymeric liquids. J. Rheol, 53 (2009), 1389-1401. 

The curves in Figure 5.2 are typical of exothermic reactions in batch or tubular reactors. The temperature overshoots the wall temperature. This phenomenon is called an exotherm. The exotherm is moderate in Example 5.2 but becomes larger and perhaps uncontrollable upon scaleup. Ways of managing an exotherm during scaleup are discussed in Section 5.3. 

The time dependence of the various species concentrations will depend on the relative magnitudes of the four rate constants. In some cases the curves will involve a simple exponential rise to an asymptote, as is the case for irreversible reactions. In other cases the possibility of overshoot (exists, as indicated in Figure 5.2. Whether or not this phenomenon will occur depends on the relative magnitudes of the rate constants and the initial conditions. However, the fact that both roots of equation 5.2.34 must be real requires that there be only one maximum in the curve for R(t) or S(t). 

The consequences of this type of activated physical adsorption is not only that the quantity adsorbed can lie off the isotherm but also that the measured quantity of adsorption is far less than the equilibrium value. No experiments have been conducted to illustrate whether or not the quantity adsorbed lies within the hysteresis loop. The occasional failure of the vacuum volumetric method to agree with the dynamic method, which is not subject to any pressure overshoot, may in part be attributed to this phenomenon. 

The dosing requirement of gravimetric and volumetric apparatus can lead to pressure overshoot which may produce data off the isotherm in the hysteresis region. The continuous flow method is not susceptible to this phenomenon. 

The restoration for low z suffers a bit more overshoot at the gradient edges. This is consistent with a photon-bunching phenomenon that occurs as the solution to estimator (34). Notice that our estimator (61) includes Eq. (34). If Eq. (34) per se is solved, the answer is that all N photons jam into the resolution cell xm that has the largest degeneracy zm over m = 1,..., M. The other cells are empty, and the estimated spectrum is a spike. The presence of image data, and of noise, will compromise this extreme behavior. However, there is still a tendency to bunch photons in some cells and deplete them from others, as seen in Fig. 6(a-c). 

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