Submarine detection systems

Piezoelectricity links the fields of electricity and acoustics. Piezoelectric materials are key components in acoustic transducers such as microphones, loudspeakers, transmitters, burglar alarms and submarine detectors. The Curie brothers [7] in 1880 first observed the phenomenon in quartz crystals. Langevin [8] in 1916 first reported the application of piezoelectrics to acoustics. He used piezoelectric quartz crystals in an ultrasonic sending and detection system - a forerunner to present day sonar systems. Subsequently, other materials with piezoelectric properties were discovered. These included the crystal Rochelle salt [9], the ceramics lead barium titanate/zirconate (pzt) and barium titanate [10] and the polymer poly(vinylidene fluoride) [11]. Other polymers such as nylon 11 [12], poly(vinyl chloride) [13] and poly (vinyl fluoride) [14] exhibit piezoelectric behavior, but to a much smaller extent. Strain constants characterize the piezoelectric response. These relate a vector quantity, the electrical field, to a tensor quantity, the mechanical stress (or strain). In this convention, the film orientation direction is denoted by 1, the width by 2 and the thickness by 3. Thus, the piezoelectric strain constant dl3 refers to a polymer film held in the orientation direction with the electrical field applied parallel to the thickness or 3 direction. The requirements for observing piezoelectricity in materials are a non-symmetric unit cell and a net dipole movement in the structure. There are 32-point groups, but only 30 of these have non-symmetric unit cells and are therefore capable of exhibiting piezoelectricity. Further, only 10 out of these twenty point groups exhibit both piezoelectricity and pyroelectricity. The piezoelectric strain constant, d, is related to the piezoelectric stress coefficient, g, by... 

Military INS and GPS Uses. Flight instrumentation and avionics are used by military aircraft as well as civilian aircraft, but the military have many other applications. INS is used in guided missiles and submarines. It can also be used as a stand-alone navigational system in vehicles that do not want to communicate with outside sources for security purposes. INS and GPS are used in bombs, rockets, and, with great success, unmanned aerial vehicles (UAVs) that are used for reconnaissance as well as delivering ordnance without placing a pilot in harm s way. GPS is used in almost all military vehicles such as tanks, ships, armored vehicles, and cars, but not in submarines as the satellite signals will not penetrate deep water. GPS is also used by the United States Nuclear Detonation Detection System as the satellites carry nuclear detonation detectors. 

The fi O-Pj system has also recently been applied to phosphates associated with ferric iron oxyhydroxide precipitates in submarine ocean ridge sediments (Blake et al., 2000, 2001). The gi O-Pj signature of phosphate associated with these authigenic Fe-oxyhydroxide precipitates indicates microbial phosphate turnover at elevated temperatures. The latter observation suggests that phosphate oxygen isotopes may be useful biomarkers for fossil hydrothermal vent systems. On the basis of this work, Blake et al. (2001) also hypothesize that authigenic phases extant on other planets may retain imprints of primitive biospheres, in the form of detectable and diagnostic fi O-Pj composition, imparted by biochemical, enzymatic processes. 

Over the past decade, the development of stable microbubbles has extended to the pharmaceutical arena as ultrasound contrast agents. Knowledge of microbubbles or gas-water interfaces as efficient backscatterers of sound waves has existed for many decades. Even before it was conceived that they could be used for clinical ultrasound image enhancement, the U.S. Navy was interested in bubble technology because sound or sonar was an efficient means for detecting ships and submarines—the reason being that submarines could be made of stealth components but could not completely hide their propulsion systems, which would form a trail of bubbles or cavitation nuclei, detectable by ultrasound. 

Fig. 16.27 Mounts Melbourne and Erebus are located on opposite ends of the Terror rift which is a local manifestation of the West Antarctic rift system. The summit of Mt. Melbourne displays fumaroles and high heat flow indicating that this volcano is not yet extinct. Mt. Erebus still maintains a lava lake in its Inner Crater. Small submarine vents have been detected by geophysical surveys. The alignment of Mt. Melbourne and Mt.

Towed array sonar is a system of hydrophones towed behind a submarine or a surface ship on a cable. It mainly consists of a source array and a receiver array. In order to ensure its detection range and positioning accuracy, the source array is always hundreds of meters long and contains thousands of similar components. 

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... 

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