Burglar alarms

Several polymers also are effective piezoelectric materials. The best known of these is PVDF (Equation 6.55), which is employed in loud speakers, fire and burglar alarm systems, earphones, and microphones. 

However relieved, and however exhausted, you are unlikely to be easily able to fall asleep without some resurgence of anxiety or altered perceptions. This is because falling asleep under any circumstance is characterized by the sudden eruption of dreamlike conscious experience. These sleep onset microdreams are often associated with classic jerks of the trunk and extremities akin to those in startle reactions. Reasoning teleologically, it would seem that nature had evolved a built-in burglar alarm system to provide us with a security check at sleep onset, just the time that we are about to become most vulnerable to predation ... 

I A simple pull switch for use In burglar alarms, booby traps and for arming bombs can be made from a spring clothespin, a wood or plastic wedge, and a pull wire or string. See drawing Hi)... 

POPULAR MECHANICS FEBRUARY/ 1940 Burglar Alarm Fires Cartridge... 

Coatings. The traditional uses of coatings for decorative and protective purposes are expanding into future concepts of coatings as energy collective devices, burglar alarm systems, and other novel... 

Photoelectric materials are usually semiconductors. Copper(I) oxide photoelectric cells do not generate much power, but they react rapidly to changes in light levels. This property makes them useful as light detectors, which have many applications from cameras with automatic adjustment settings to automatic door openers and burglar alarms. 

Safety equipment—fire alarm, burglar alarm, lightning and other static arresters... 

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... 

Abrahams, M. V. Townsend, L.D. 1993. Bioluminescence in dinoflagellates - a test of the burglar alarm hypothesis. Ecology, 74, 58—260. 

The effects of negative reinforcement, on the other hand, are not quite as clear. An example may help in understanding negative reinforcement. Fire and burglar alarms are based on the principle of negative reinforcement. 

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