Submerged barriers

G. Bellotti, A simplified model of rip currents systems around discontinuous submerged barriers, Coastal Eng. 51(4), 323-335 (2004). 

By the term submerged barrier , sometimes referred to as a reef, I mean an energy maximum along the MEP, but one whose energy is below that of the separated reactants. 

Smith el pointed out that the values of I.E. — E.A.) for reactions of 0( P) with alkenes straddle the critical value of 8.75 eV and would therefore comprise an interesting test case for the proposals in their paper. CRESU experiments were subsequently performed on these reactions by Sabbah et al. and their results are shown in Figure 1.7. They are compared with the results of calculations based on the two transition state model which made use of ab initio calculations of the potential at long and medium range. The ab initio calculations confirmed that all the reactions that were studied, apart from that of 0( P) with ethene, for which (I.E. — E.A.) = 9.05 eV, exhibit submerged barriers at separations shorter than those associated with the van der Waals minima. As the curves in Figure 1.7 show, the agreement of theory with experiment is excellent. 

Barrier polymers are used for many packagiag and protective applications. As barriers they separate a system, such as an article of food or an electronic component, from an environment. That is, they limit the iatroduction of matter from the environment iato the system or limit the loss of matter from the system or both. In many cases the environment is simply room air, but the environment can be very different, such as ia the case of protecting a submerged system from water. 

Tidal barriers utilise the rise and fall of the tide (the tidal range) to trap seawater at high tide in a reservoir behind a barrage. As the water leaves or enters the reservoir in a constrained duct, submerged hydroturbines generate electricity, as in conventional hydropower. There is only one significant tidal barrier power plant, which is at La Ranee, Brittany, in France. 

Tidal-current (or stream) power is derived from water turbines submerged in the wide expanse of a tidal flow or current there is no constructed barrier. Such a turbine is, therefore, the water-equivalent of a wind turbine. As yet, there are no commercial tidal-current power plants. 

Figure 3.9. Scheme of the LB technique (a) deposition of the amphiphiles on the water subphase with the solid substrate submerged (b) by action of the barrier the ML is compressed (c) by pulling out the substrate vertically a ML is transferred to both sides of the substrate (d) a multilayered structure is built up by repeated up and down strokes of the substrate, (e) Distinct arrangements of LB Aims. 

Lighty R.G. (1985) Preservation of internal reef porosity and diagenetic sealing of submerged ealy holocene Barrier Reef, southeast Florida Shelf. In Carbonate Cements (ed. O.P. Bricker), pp. 123-151. John Hopkins Press, Baltimore, MD. 

In order to prevent leakage of monolayer material over the edges of the trough and across the barrier, the edges and the barrier should not be wetted by the subphase liquid, but the underside of the barrier, somewhat submerged into the liquid, should be wetted. For air-water interfaces Teflon is the most preferable material. Obviously, it should not contaiin soluble impurities. 

Bubble barrier - A method for containing oil consisting of an underwater air delivery system that creates a curtain of rising bubbles that deflects the oil. The system has been used with some success in relatively calm areas, such as harbours. The system requires considerable maintenance when the submerged perforated pipes used to produce the bubble curtain become covered with redistributed bottom silt. 

Submerged wave-cut notches (Blanchon et al. 2002), evidence for the catastrophic drainage of large volumes of meltwater from ice-dammed lakes into the ocean (Clarke et al. 2001) and buried barrier complexes (Stapor Stone 2004) all suggest that millennial/centennial oscillations in sea-level must have occurred in the Holocene. Some interpretations of regional Holocene sea-level... 

In 1989, a related technology of cleanup and barrier combined was described by Lageman, Pool, and Seffinga (Fig. 16.4). A line of electrodes placed across a plume of pollution was used to clean up the pollutant as it moved toward the electrokinetic fence. The electrodes are operated submerged in an electrode solution, which can be removed for later treatment. Full-scale trials report successful cleanup, approaching 80% (Lageman, 1993). Further details are given in Chapter 19. 

Sanders, J.E., and Kumar, N. 1975. Evidence of shoreface retreat and in-place "drowning" during Holocene submergence of barriers, shelf of Fire Island, New York. Geological Society of America Bulletin, 86 65-76. 

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