Underwater objects

Underwater Objects We made a brief allusion to another environment in commenting on Figure 4.4. That figure shows one example of an environment that is very different from a simple buried munition. Several things become apparent immediately. Clearly, the aqueous state is likely to dominate the entire process. There will be some sorbing onto particles of the bottom, but even for objects totally buried in the bottom that will be reduced, since the bottom will always be at a saturated state. Therefore, it is reasonable to focus development attention on finding molecules in the aqueous state, rather than the vapor state. The Office of Naval Research (ONR) has sponsored substantial work of this nature. Some of it is reported in detail in Chapter 6. 

Turbulence is not the asset in water that it is in air. In air, we saw that some turbulence is required to bring the molecules out of the chemical boundary layer. That may also be needed in water to move molecules away from the bottom surface. Turbulence away from the surface tends to break up the plumes of molecules that are diagrammed in Figure 4.4. Those plumes are the key to successful detection of an underwater object that is releasing the molecules of interest. One result of the ONR experiment at San Clemente Island, off San Diego, California, was a better understanding of the formation, persistence, and dissipation of these plumes. When a well-formed plume is available, it often becomes possible to follow it to its source see Chapters 5 and 6. 

Towed Array Cable with a number of underwater microphones used to detect underwater objects across a range of aquatic environments. 

Figure 6.3.8.1 Experimental setup for the formation of Hg/Pt hemispherical UME by electrodeposition from a Hg2(NOj)2 solution with 0.1 M KNO3 acidified to 0.5% with HNO3 as supporting electrolyte. This glass cell was joined at the base with a microscope slide. The underwater objective was lowered into solution and the deposition curve recorded during a 300 sec potential step of -0.1 V vs. Ag/AgCl. Reprinted with permission from reference (3). Copyright, the American Chemical Society.

Usually power sources from 1 to 10 A are used (rarely 50-100 A), which at a voltage from 5 to 24 V or to 60 V ensure the realization of CP of modern underground and underwater objects. Due to the application of modem high quality coatings and insulation, the current demand for cathodically protected metal stmctures has decreased, creating new, beneficial conditions for the development of this technology, at the same time decreasing the hazard of pollution of the environment. 

Piezoelectric materials may be used as transducers between electrical and mechanical energies. One of the early uses of piezoelectric ceramics was in sonar systems, in which underwater objects (e.g., submarines) are detected and their positions determined using an ultrasonic emitting and receiving system. A piezoelectric crystal is caused to oscillate... 

Stabilization iavolves the removal of the cause of deterioration which is frequentiy soluble salts present ia the stone. If the stmctural strength of the stone permits it, this can be done through soakiag. The object is placed underwater ia a tank, and the water is changed regularly. Another method is by apphcation of poultices on the surface. 

Bulk sensors certainly have a role in chemical sensing of explosives, but the subject of this book is the other basic type sensor, one that seeks molecules released from the bulk of the explosive material in an object. We will refer to these as trace chemical sensors. They are sometimes called vapor sensors, but that seems a less accurate description when they are applied to explosive molecules, which may not always be found in a vapor state. As we shall see in Chapter 5, that requires us to understand where and how to look for these molecules. It will become apparent upon a little reflection that the two types of sensors are complementary and are best used in different situations. Furthermore, even when trace sensors are used, in some situations sampling of particles of soil or vegetation or sampling from surfaces may prove to be more productive that vapor sampling. For underwater sources the term vapor sensing is also inappropriate. 

These obviously include UXO,1 IEDs,2 and other ERW,3 but also may include similar objects underwater, buried in the seabed. There are also abandoned mining and construction sites that may need to be searched for old explosives. No matter which type object we may hypothesize as the source of molecules found, we need to follow similar reasoning to locate that source. 

Plumes in Water Several fine researchers have approached the study of underwater plumes with different objectives. While all this work is undoubtedly instructive, a series of articles [28-32] produced by Webster and Weissberg and their colleagues may apply most directly. They have examined the structure [28] of plumes in controlled experiments and produced photographs of dye plumes to study their development. They also took the point of view of a hungry crab [32], In its attempt to find the food source indicated by the plume, the crab manipulates its sensors within the plume. The structure of the plume makes it necessary. Chapter 5 is devoted to a description of these plumes. 

At the end of the preceding century, an intensification of the studies of the Black Sea ecosystem occurred. Its necessity was mainly defined by three principal reasons the influence of the regional climate changes during the last decade of the last century on the entire Black Sea ecosystem the strongest impact of species-invaders on the pelagic and bottom biocenoses of the basin and catastrophic reduction in their commercial potential and, finally, the large-scale construction and plans of construction of object of oil and gas complex in the sea area such as the oil terminal of the the Caspian Pipeline Consortium (CPC) on the Russian shelf (2001), and the Blue Flow (2003) and Blue Flow - 2 (nearest future) underwater gas pipelines. 

Underwater acoustics is routinely used in laboratory-scale test facilities for flaw detection, transducer calibration, material property evaluations, and acoustic visualization. In a typical underwater acoustic study, an object of interest is submerged in a water filled tank and acoustically illuminated (insonified). The acoustic signals scattered by the object are then measured and analyzed. If the tank used is not sufficiently large, these measured acoustic signals will include spurious echo components due to extraneous wall reflections. Since the effect of these contaminating echoes usually cannot be removed from the resulting data set by post analysis, they must be prevented from occurring at their source. One cost... 

The ocean conceals a vast number of unexplored, and potentially valuable, archaeological sites. But the technology needed to explore these sites was not perfected until the mid-twentieth century. With the development of scuba gear, underwater transport, and other underwater devices, archaeologists have improved their ability to survey and retrieve objects underwater. 

At great ocean depths or in areas with poor visibility other devices may be employed. Sonar may be used to determine the location of large or encrusted objects by calculating the time it takes echoes to bounce off them. Underwater cameras may be towed by the boat to take pictures of a site in water with good visibility. 

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