Pseudo-steady-state model

The mathematical solution to moving boundary problem involves setting up a pseudo-steady-state model. The pseudo-steady-state assumption is valid as long as the boundary moves ponderously slowly compared with the time required to reach steady state. Thus, we are assuming that the boundary between the salt solution and the solid salt moves slowly in the tablet compared to the diffusion... 

The unsteady-state operation is approximated by a pseudo-steady-state model... 

RETORT CALCULATION During the retort process we assume that no oxygen is present so that only water transport is considered. At retort temperatures the diffusion coefficient of water in materials of interest is sufficiently high so that a pseudo-steady-state model, in which linear profiles are assumed across all structural layers, can be used. The EvOH layer is assumed to be at a uniform water activity at a given time which is good assumption based on water permeability measurements in EvOH at humidities found in package applications (13 ). 

We, however, suggest that the time gap between generation and expulsion from the deep Are Formation relative to the shallower Spekk Formation, and time dependent HC loss from traps, i.e. the pseudo-steady-state model of loss and replenishment discussed in this paper and in Paper I, is the reason why we today generally do not observe type Ill/coal derived gas in the traps off Mid-Norway. Thus, the time lag between, even delayed expulsion from the Are Formation, and expulsion from the shallower Spekk Formation is simply too significant in light of the dynamic trap model (cf. Sales 1993, 1997—trap type II and III), for these traps to hold on to petroleum generated e.g. 50Mabp. 

Pseudo-steady-state Approximation for Dispersed Drugs Loaded above the Solubility. Drug molecules can be loaded into the matrix as fine solid particles. In this situation, the drug concentration within the matrix may be much higher than the drug solubility in the aqueous solution. A boundary between dissolved and dispersed drug may be present as release proceeds, this boundary would move from the outer surface of the matrix to the center. A pseudo-steady-state model has been used to describe these systems [10] ... 

Since the protein is loaded into the matrix at high concentration in solid particles, and protein molecules are confined to the water-filled pore space, it is possible for protein concentration within the pores to exceed protein solubility. The pseudo-steady-state model of Higuchi [10] (Equation 9-20) can be modified to account for this physical situation ... 

Quasi-static/Pseudo-steady-State Model... 

Quasi-Statlc/Pseudo-Steady-State Model 1 d (MTy... 

R. S. Barlow, Analysis of the Adsorption Process and Desiccant Systems-A Pseudo Steady State Model for Coupled Heat and Mass Transfer, Solar Energy Research Institute, Golden, CO, Report No. SERI/TR-631-1330, 1982. 

The unsteady-state operation is approximated by a pseudo-steady-state model using a series of time steps, during each of which steady-state conditions are assumed. At the end of each time step the bottoms product becomes the feed for the next time step. 

But experimental concentration profiles measured 1 day after implantation were noticeably different the peak concentration was substantially higher and the drug penetration into the surrounding tissue was deeper (see the left-hand panel of Figure 15.3). This behavior cannot be easily explained by the pseudo-steady-state models described above. For example, if the difference observed at 1 day represents transient behavior, the concentration observed at a fixed radial position should increase with time (Figure 15.2) in contrast, the experimental concentration at any radial position on day 1 is higher than the concentration measured at that same position on subsequent days. 

At the same time, current mechanistic understanding of photocatalysis speaks in favor of applying the pseudo-steady-state model for virtually all photocatalyzed reactions, where adsorption/desorption equilibrium cannot be achieved. 

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