Dynamic Variation

Meylan S, Behra R, Sigg L (2003) Accumulation of Cu and Zn in periphyton in response to dynamic variations of metal speciation in freshwater. Environ Sci Technol 37 5204... 

Mathematical models of tubular chemical reactor behaviour can be used to predict the dynamic variations in concentration, temperature and flow rate at various locations within the reactor. A complete tubular reactor model would however be extremely complex, involving variations in both radial and axial... 

As explained in Sec. 3. 3. 1.11, the fractional holdup of the dispersed phase in agitated extraction columns will vary with changing phase flow rate. This dynamic variation in the holdup along the column will cause a dynamic velocity profile in both phases. 

The general experimental approach used in 2D correlation spectroscopy is based on the detection of dynamic variations of spectroscopic signals induced by an external perturbation (Figure 7.43). Various molecular-level excitations may be induced by electrical, thermal, magnetic, chemical, acoustic, or mechanical stimulations. The effect of perturbation-induced changes in the local molecular environment may be manifested by time-dependent fluctuations of various spectra representing the system. Such transient fluctuations of spectra are referred to as dynamic spectra of the system. Apart from time, other physical variables in a generalised 2D correlation analysis may be temperature, pressure, age, composition, or even concentration. 

More recently we have turned our attention to the influence of dynamic variations in stacking on base-base CT. Here again Ap is particularly useful given its demonstrated charge transfer chemistry in DNA, and its ability to report on the structure and dynamics of the DNA environment. Using spe-... 

The significance of dynamic variations in stacking has been revealed by many of our investigations of DNA-mediated CT. The yield of long-range... 

Dou, S., Herb, B., Tuzla, K., and Chen, J. C., Dynamic Variation of Solid Concentration and Heat Transfer Coefficient at Wall of Circulating Fluidized Bed, Fluidization VII, 793-801 (1993)... 

It is natural to equate the dynamical variations of the basic operators 6Xk and 5Yk, obtained with the scaling (7) and Thouless (25) perturbed wave functions. This provides the additional relation between the amplitudes and deformations Qk and pk and finally result in the system of equations for the unknowns pk and p. ... 

Tests such as the tensile strength and tear strength tests evaluate polyurethanes to destruction. When polyurethanes are used in a practical situation, the aim is for them to have as long a life as needed in the application. Stress, strain, and shear are applied to the polyurethane at various frequencies and at different temperatures. There may also be dynamic variations on top of a static load, for example, vibrations on a loaded isolation pad. 

The extension of Gillespie s algorithm to spatially distributed systems is straightforward. A lattice is used to represent binding sites of adsorbates, which correspond to local minima of the potential energy surface. The discrete nature of KMC coupled with possible separation of time scales of various processes could render KMC inefficient. The work of Bortz et al. on the n-fold or continuous time MC CTMC) method can lead to computational speedup of the KMC method, which, however, has been underutilized most probably because of its difficult implementation. This method classifies all atoms in a finite number of classes according to their transition probability. Probabilities are computed a priori and each event is successful, in contrast to the Metropolis method (and other null event algorithms) whose fraction of unsuccessful (null) events increases drastically at low temperatures and for stiff problems. In conjunction with efficient search within a class and dynamic variation of atom coordi-nates, " the CPU time can be practically independent of lattice size. After each event, the time is incremented by a continuous amount. 

Unlike the case of the regenerative PEC system, sulphur formed at the photoanode (and dissolved as polysulphide species, S( c+i) ) is here not balanced by the reduction reaction at the counter electrode, because of the simultaneous reduction process taking place at the storage electrode. As a result, sulphur is accumulated in the photoelectrode compartment, and is removed only in the subsequent discharge process. This dynamic variation in electrolyte composition may have a profound influence on the stability of the photoelectrode and electrolyte, and on cell potential. To minimise these effects, either excess polysulphide must be included in the photocompartment, or a limit must be set to the maximum depth of cell charge and discharge. 

Mathematical models of tubular chemical reactor behaviour can be used to predict the dynamic variations in concentration, temperature and flow rate at various locations within the reactor. A complete tubular reactor model would however be extremely complex, involving variations in both radial and axial positions, as well as perhaps spatial variations within individual catalyst pellets. Models of such complexity are beyond the scope of this text, and variations only with respect to both time and axial position are treated here. Allowance for axial dispersion is however included, owing to its very large influence on reactor performance, and the fact that the modelling procedure using digital simulation is relatively straightforward. 

MSPM techniques rely on the model of the process. If the process has significant dynamic variations, state-space and subspace state-space models... 

M35. Mortensen, H. B., V0lund, A., and Christophersen, C., Glucosylation of human haemoglobin A. Dynamic variation in the Hb Aj described by a biokinetic model. Clin. Chim. Acta 136, 75-81 (1984). 

Sulfate-sulfide isotopic exchange disequilibrium (where sulfate is reduced to sulfide without isotopic exchange but sulfide minerals and H2S isotopically equilibrate) in closed and open isotopic systems result in significantly smaller shifts in isotopic compositions (Figure 1). In addition, the calculated shifts are to higher sulfide compositions, generally consistent with the measured values for seafloor sulfide minerals. Analyses of the natural samples, however, provide no evidence of systematic isotopic differences between pyrite, sphalerite, and chalcopyrite, as predicted by both standard fractionation approaches and these calculated isotopic reaction pathways, possibly due to dynamic variations of mixing and precipitation on a local scale. 

The preparation of a dynamic variation (to be described in the following section) is somewhat in between the two extremes, though very much closer to the designer s end. 

The plant must be considered for example, the amount of compound in the tissues must be sufficient to produce a biological effect on the test insect. In the evaluation of this, it should be remembered that many plants have specialized tissues which contain high levels of secondary metabolites. For example, many conifer species contain specialized secretory structures, such as resin ducts, which contain high localized concentrations of terpenoids [82]. There may also be dynamic variations in the amounts of these compounds in the plant, resulting from seasonal fluxes or synthesis induced upon stress. 

Sound pressure dynamic variation in atmospheric pressure. The pressure at a point in space minus the static pressure at that point. 

The images from the ensemble of an NMR structure (Eig. 5.6, b and d) show the dynamic variation of a molecule in solution. This reflects the conditions of the... 

Cheng J, Guo X (1998) Distribution and dynamic variations of species and quantity of benthos in the Bohai Sea. Mar Fish Res 19(l) 31-42 (in Chinese with English... 

When a system is more complex and there are more potential sources of dynamic variations, a more complicated control is required. Particularly in automatic systems where human operators are replaced by machines and computers, a thorough design of control responsibilities and procedures is necessary. Control activities include automatic control of individual machines, material handling, equipment, manufacturing processes, and production systems, as well as control of operations, inventory, quality, labor performance, and cost. Careful design of correct and adequate controls that continually identify and trace variations and disturbances, evaluate alternative responses, and result in timely and appropriate actions is therefore vital to the successful operation of a system. 

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