Dispersion time, defined

Odor dispersion time Time taken to reduce an odor to a defined level from a given concentration in a standard test. 

Passive puff or plume In addition to the restriction on plumes discussed above, there is an along-wind dispersion time scale given by td = 2Gjur where Gx is evaluated at the endpoint distance xe. The release can usually be considered a plume if ts > 2.5 fd, where ts is the source time scale defined above, and the release can be considered a puff if td > ts. For td< ts< 2.5 td, neither puff nor plume models are entirely appropriate the predicted concentration is considered the largest of the puff and plume predictions. 

Graham s definitions were expanded, and the concept of a colloidal state of matter evolved. According to this view, a substance could occur in a colloidal state just as it could occur under various conditions as a gas, liquid, or solid. If a colloidal solution was, at that time, defined as a solution in which the dispersed particles were comprised of large molecules, the ascertion would have been more acceptable. 

The rate constant of longitudinal dispersion is defined as the relative change with time of the maximum concentration of a concentration cloud ... 

The ability to fit all available dispersion-time data well by either first-oider ch- second-order GPI kinetics has inqxxtantmechanistic in ilicaticms as well as practical significance. - In practical terms this new approach can be used with the well-defined database of this and the companion study to analyse the significance of important kinetic parameters k, and E (see... 

Figure 2.15. In addition to peak height a dispersed sample zone yields an infinite number of vertical readouts some of them being shown as vertical lines at delay times to fn. Thus, any dispersed sample zone is a matrix of concentrations versus time, defined by C , to, and t . 

A short pulse of light launched into a fibre will tend to spread out, as a result of dispersion. In optical fibres, the dispersion is defined as the delay between the arrival time of the start of a light pulse and its finish time relative to that of the initial pulse. It is measured at half peak amplitude. If the initial pulse has a spread of fj seconds at 50 % amplitude and the final pulse a spread of tf seconds at 50 % amplitode after having travelled d kilometres, the dispersion is given by ... 

The total amount of a nonreactive tracer injected as a Dirac pulse at the reactor entrance is given by q. The Bodenstein number, Ho, is defined as the ratio between the axial dispersion time, = L /D, and the mean residence time, t = r = L ju, which is identical to the space time for reaction mixtures with constant density. For Bo - 0 the axial dispersion time is short compared to the mean residence time resulting in complete backmixing in the reactor. For Ho oo no dispersion occurs. In practice, axial dispersion can be neglected for Ho > 100. 

Conductive-system dispersive response may be associated with a distribution of relaxation times (DRT) at the complex resistivity level, as in the work of Moynihan, Boesch, and Laberge [1973] based on the assumption of stretched-exponential response in the time domain (Eq. (118), Section 2.1.2.7), work that led to the widely used original modulus formalism (OMF) for data fitting and analysis, hi contrast, dielectric dispersive response may be characterized by a distribution of dielectric relaxation times defined at the complex dielectric constant or permittivity level (Macdonald [1995]). Its history, summarized in the monograph of Bbttcher and Bordewijk [1978], began more than a hundred years ago. Until relatively recently, however, these two types of dispersive response were not usually distinguished, and conductive-system dispersive response was often analyzed as if it were of dielectric character, even when this was not the case. In this section, material parameters will be expressed in specific form appropriate to the level concerned. 

In the following chapter on results and discussion, first solute solubility, is used to describe the two particle generation models developed. Second, the role of the mixing behavior of solvents and supercritical carbon dioxide in the SAS process to produce solid dispersions is defined. The crystallization and the time-scale models are then presented in terms of the solute solubility criterion. A final and more... 

Colloidal dispersions often display non-Newtonian behaviour, where the proportionality in equation (02.6.2) does not hold. This is particularly important for concentrated dispersions, which tend to be used in practice. Equation (02.6.2) can be used to define an apparent viscosity, happ, at a given shear rate. If q pp decreases witli increasing shear rate, tire dispersion is called shear tliinning (pseudoplastic) if it increases, tliis is known as shear tliickening (dilatant). The latter behaviour is typical of concentrated suspensions. If a finite shear stress has to be applied before tire suspension begins to flow, tliis is known as tire yield stress. The apparent viscosity may also change as a function of time, upon application of a fixed shear rate, related to tire fonnation or breakup of particle networks. Thixotropic dispersions show a decrease in q, pp with time, whereas an increase witli time is called rheopexy. 

However, in a countercurrent column contactor as sketched in Figure 8, the holdup of the dispersed phase is considerably less than this, because the dispersed drops travel quite fast through the continuous phase and therefore have a relatively short residence time in the equipment. The holdup is related to the superficial velocities U of each phase, defined as the flow rate per unit cross section of the contactor, and to a sHp velocity U (71,72) ... 

Chemical Reaction Measurements. Experimental studies of incineration kinetics have been described (37—39), where the waste species is generally introduced as a gas in a large excess of oxidant so that the oxidant concentration is constant, and the heat of reaction is negligible compared to the heat flux required to maintain the reacting mixture at temperature. The reaction is conducted in an externally heated reactor so that the temperature can be controlled to a known value and both oxidant concentration and temperature can be easily varied. The experimental reactor is generally a long tube of small diameter so that the residence time is well defined and axial dispersion may be neglected as a source of variation. Off-gas analysis is used to track both the disappearance of the feed material and the appearance and disappearance of any products of incomplete combustion. 

In the first case, that is with dipoles integral with the main chain, in the absence of an electric field the dipoles will be randomly disposed but will be fixed by the disposition of the main chain atoms. On application of an electric field complete dipole orientation is not possible because of spatial requirements imposed by the chain structure. Furthermore in the polymeric system the different molecules are coiled in different ways and the time for orientation will be dependent on the particular disposition. Thus whereas simple polar molecules have a sharply defined power loss maxima the power loss-frequency curve of polar polymers is broad, due to the dispersion of orientation times. 

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