Individual and Collective Behavior of Small Vibrating Motors Interacting Through a Resonant Plate

We report on experiments of many small motors -- cell phone vibrators -- glued to and interacting through a resonant plate. We find that individual motors interacting with the plate demonstrate hysteresis in their steady-state frequency due to interactions with plate resonances. For multiple motors running simultaneously, the degree of synchronization between motors increases when the motors' frequencies are near a resonance of the plate, and the frequency at which the motors synchronize shows a history dependence.Comment: 7 pages, 8 figure

An Ultrasonic analog for a laser

We report measurements on ultrasonic systems analogous to random lasers. One system entails unstable ultrasonic feedback between distinct transducers, another involves a piezoelectric device that emits spontaneously and by stimulation. Both systems are found to exhibit behaviors similar to those of lasers. Over a wide range of parameters we observe narrow single emission lines, sensitivity to linear cavity properties, complex multi-mode emissions, and line narrowing

Entrainment and stimulated emission of auto-oscillators in an acoustic cavity

We report theory, measurements and numerical simulations on nonlinear piezoelectric ultrasonic devices with stable limit cycles. The devices are shown to exhibit behavior familiar from the theory of coupled auto-oscillators. Frequency of auto-oscillation is affected by the presence of an acoustic cavity as these spontaneously emitting devices adjust their frequency to the spectrum of the acoustic cavity. Also, the auto-oscillation is shown to be entrained by an applied field; the oscillator synchronizes to an incident wave at a frequency close to the natural frequency of the limit cycle. It is further shown that synchronization occurs here with a phase that can, depending on details, correspond to stimulated emission: the power emission from the oscillator is augmented by the incident field. These behaviors are essential to eventual design of an ultrasonic system that would consist of a number of such devices entrained to their mutual field, a system that would be an analog to a laser. A prototype laser is constructed

Coherent backscattering of ultrasound without a source

Coherent backscattering is due to constructive interferences of reciprocal paths and leads to an enhancement of the intensity of a multiply scattered field near its source. To observe this enhancement an array of receivers is conventionally placed close to the source. Our approach here is different. In a first experiment, we recover the coherent backscattering effect (CBE) within an array of sources and a distant receiver using time correlation of diffuse fields. The enhancement cone has an excellent spatial resolution. The dynamics of the enhancement factor is studied in a second experiment using correlation of thermal phonons at the same ultrasonic frequencies, without any active source

Overture Patriotic

https://digitalcommons.library.umaine.edu/mmb-ps/3177/thumbnail.jp

Melodies Of Scotland : Overture

https://digitalcommons.library.umaine.edu/mmb-ps/1805/thumbnail.jp

CHANGING STATUS OF MOUNTAIN LION IN CALIFORNIA AND LIVESTOCK DEPREDATION PROBLEMS

The California Department of Fish and Game studied depredation by mountain lions on livestock from 1971 through 1977 to determine the scope of the problem. Information was needed on the physical characteristics of a stock killer, the frequency and trend of predation, the livestock types preyed upon, and the geographic distribution of incidents. Department of Fish and Game verified 134 incidents of mountain lion predation on livestock which occurred between April 1971 and December 1977. Forty-five mountain lions (28 males and 17 females) were killed on depredation during this time. Approximately 42 percent of the predation incidents involved sheep, 22 percent goats and 16 percent cattle, with horses, pigs, poultry and pets composing most of the remaining prey. California\u27s south coast region from Santa Clara to Ventura County reported 44 percent of the predation incidents, 28 percent from the Sierra Nevada, 20 percent from the north coast from Napa and Sonoma counties to Humboldt County and nearly 8 percent from southern California. There does not appear to be a stock-killer profile of common sex, age or health factors. Present depredation policy appears adequate to handle the problem, but efficiency could be increased by coordinating incident verification investigations and available depredation resources, such as U.S. Fish and Wildlife Service and county predator control agents