Reverse stratification

In the stratification strategy the supply air is used to substitute the outgoing air from the ventilated (in most cases occupied) zone, thus preventing circulation patterns between the zones. The supply air has to be distributed in such a way that the buoyancy flows are not disturbed. Exhaust air openings are to be located downstream in order to avoid reverse currents within the room. The location of the contaminant sources and the heat sources causing density differences must be the same in order to carry out the contaminants with equal or higher density than air. 

For gas-fired shell boilers it is difficult to justify these trim controllers on an economic basis. Equally important, the position to control based on CO in such a boiler is ideally in the reversal chamber and not the flue. However, the temperature and stratification of flue products here make it impracticable. 

Hansen and Rattray (1966) introduced a general classification scheme for estuaries based on stratification/circulation that is divided into the following four estuarine types Type 1 estuaries well-mixed estuaries with mean flow in the seaward direction and the salt balance being maintained by diffusive processes—via tidal transport Type 2 estuaries partially mixed estuaries where the net flow reverses at depth and the salt flux is maintained by both diffusive and advective processes Type 3 estuaries these estuaries include fjords with two distinct layers and advection accounting for the majority of the salt flux Type 4 estuaries these are salt-wedge estuaries where freshwater flows out over a stable more dense bottom layer. 

Some thickness transitions occurring in the foam films, such as CBF/NBF were considered so far and estimated from the h(Cei), /i(pH) and TT(/i) dependences. These are transitions in the equilibrium thickness from the thicker CBF to the thinner NBF. The reverse thickness transitions were also realised experimentally, for instance NBF/CBF (see Fig. 3.57) in the Tl(/x) isotherm of NaDoS films at Cei = 0.165 - 0.18 mol dm 3. Similar reverse transition was found in the h(Cei) dependence of lyso PC films in the presence of CaCl2. In this case there occurs a specific adsorption of the Ca2+ ion and the films transfer from CBF to NBF (Fig. 3.50). Along with transition from one equilibrium state into another, non-equilibrium thickness transitions also exist. This is the phenomenon known as stratification, i.e. a consecutive stepwise film thinning. During this process the initially formed films thin to... 

The coupling between the hydrological forces and chemical processes —H->C—is responsible for transport of solutes, and this coupling is also to some extent reflected in the water-flow-rate dependence of some mineral dissolution reactions. The reverse coupling between chemical forces and hydrological processes—C- H—is seen in such phenomena as chemical density stratification in lakes, evaporative mixing caused by solute concentration increase in a surface water layer, and chemical density-driven water currents. 

Cardiac MRI may have a role in risk stratification for SCD due to its ability to detect myocardial scar. The use of gadolinium, which accumulates in infarcted tissue, has allowed delayed enhancement MRI to detect scar burden. Early experiments in dog models performed by coronary artery occlusion compared acute and chronic infarcts to pathologic specimens of the dog heart postmortem (89,90). Delayed enhancement MRI was remarkably accurate in imaging the infarcted tissue in comparison to the pathologic specimen. The spatial extent of hyperenhancement was the same as the spatial extent of myocyte necrosis at every stage post-MI. Reversible ischemia did not show delayed gadolinium uptake. Thus, delayed enhancement MRI can distinguish between reversible and irreversible injury, and... 

ENSO events are characterized by reversals of the atmospheric pressure systems in the south and central Pacific and switching of the sources of the intensely upwelled water masses along the southeastern Pacific continental margin. An El Nino event results in warmer surface waters, greater stratification and reduced upwelling of nutrients in the central and eastern equatorial Pacific, reducing primary productivity. While reduced equatorial-subequatorial productivity during El Nino is observed in the central eastern Pacific in all studied events (Barber Chavez, 1983 Barber etal., 1996 Strutton Chavez, 2000), the effects of ENSO events on POC flux to the seafloor are not clear. 

Jigging is a process of particle stratification in which the particle rearrangement results from an alternate expansion and contraction of a bed of particles by pulsating fluid flow. The vertical direction of fluid flow is reversed periodically. Jigging results in layers of particles arranged by increasing density from the top to the bottom of the bed. 

In smaller installations, steaming may be done in the kiln but, in larger installations, a separate chamber supplied with low-pressure, saturated steam is used for this purpose. Such chambers are not normally supplied with fans, and stratification of the steam and air can be a problem. Lumber that is high-temperature dried should be cooled so that the wood temperature falls to about 70 to 95°C to enable the wood to pick up moisture. The steaming induces a reversal of the moisture content profile through the wood, with concomitant reduction in the residual stresses. 

Although the first superheater is stable with respect to density wave oscillations, even without orifices, we have to expect flow reversal in some fuel assemblies of the first superheater of a three-pass core at low mass flow rates because of an unstable stratification... 

The convective instability, reached by the stratification of two multi-component cryogenic liquid layers with different densities, was originally believed to cause the stratified layers to reverse position by rolling over. This is not correct... 

Once the RPV pressure reaches the same value as that at the bottom of the core flooding pool, flow direction in the core flooding line reverses, and the water flows by gravitational force from the core flooding pool into the RPV irrespective of whether natural convection or stratification prevails in the pool or in the RPV. 

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