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Sound Cannon
A long-range acoustic device (LRAD), acoustic hailing device (AHD) or sound cannon is a specialized loudspeaker that produces sound at high power for communicating at a distance. It has been used as a method of crowd control, which has caused permanent Hearing loss, hearing damage, having an extremely high decibel capacity (up to 160 dB measured at one meter from the device). Other uses have included for negotiations in siege situations; to deal with piracy at sea; for mass notification during natural disasters or other emergencies; and by defense forces, including several navies. Overview Acoustic hailing devices are acoustic devices capable of outputting Intelligibility (communication), intelligible sound at very high volumes. The distance at which acoustic hailing can be effective varies based on several factors including the sound level, directionality, and Audio frequency, frequency of the acoustic source, the sensitivity and directionality of the receiver, and th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Infrastructure Protection
In the U.S., critical infrastructure protection (CIP) is a concept that relates to the preparedness and response to serious incidents that involve the critical infrastructure of a region or the nation. The American Presidential directive PDD-63 of May 1998 set up a national program of "Critical Infrastructure Protection". In 2014 the NIST Cybersecurity Framework was published after further presidential directives. History The U.S. CIP is a national program to ensure the security of vulnerable and interconnected infrastructures of the United States. In May 1998, President Bill Clinton issued presidential directive PDD-63 on the subject of critical infrastructure protection. This recognized certain parts of the national infrastructure as critical to the national and economic security of the United States and the well-being of its citizenry, and required steps to be taken to protect it. This was updated on December 17, 2003, by President George W. Bush through Homeland Security ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Institute Of Physics
The American Institute of Physics (AIP) promotes science and the profession of physics, publishes physics journals, and produces publications for scientific and engineering societies. The AIP is made up of various member societies. Its corporate headquarters are at the American Center for Physics in College Park, Maryland, but the institute also has offices in Melville, New York, and Beijing. Historical overview The AIP was founded in 1931 as a response to lack of funding for the sciences during the Great Depression. /www.aip.org/aip/history "History of AIP" American Institute of Physics. July 2010. The AIP was founded in 1931 at a joint meeting between four physics societies: the American Physical Society, the Optical Society of America, the Acoustical Society of America, and the Society of Rheology. These were soon joined by the American Association of Physics Teachers, for a total of five societies. It formally incorporated in 1932 consisting of five original "member so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave Number
In the physical sciences, the wavenumber (or wave number), also known as repetency, is the spatial frequency of a wave. Ordinary wavenumber is defined as the number of wave cycles divided by length; it is a physical quantity with dimension of reciprocal length, expressed in SI units of cycles per metre or reciprocal metre (m−1). Angular wavenumber, defined as the wave phase divided by time, is a quantity with dimension of angle per length and SI units of radians per metre. They are analogous to temporal frequency, respectively the '' ordinary frequency'', defined as the number of wave cycles divided by time (in cycles per second or reciprocal seconds), and the ''angular frequency'', defined as the phase angle divided by time (in radians per second). In multidimensional systems, the wavenumber is the magnitude of the ''wave vector''. The space of wave vectors is called ''reciprocal space''. Wave numbers and wave vectors play an essential role in optics and the physics of w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicopter
A helicopter is a type of rotorcraft in which Lift (force), lift and thrust are supplied by horizontally spinning Helicopter rotor, rotors. This allows the helicopter to VTOL, take off and land vertically, to hover (helicopter), hover, and to fly forward, backward and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of short take-off and landing (STOL) or short take-off and vertical landing (STOVL) aircraft cannot perform without a runway. The Focke-Wulf Fw 61 was the first successful, practical, and fully controllable helicopter in 1936, while in 1942, the Sikorsky R-4 became the first helicopter to reach full-scale mass production, production. Starting in 1939 and through 1943, Igor Sikorsky worked on the development of the Vought-Sikorsky VS-300, VS-300, which over four iterations, became the basis for modern helicopters with a single main rotor and a single tail rotor. Although most earlier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transducer
A transducer is a device that Energy transformation, converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, Measuring instrument, measurement, and control systems, where electrical signals are converted to and from other physical quantities (energy, force, torque, light, motion, position, etc.). The process of converting one form of energy to another is known as transduction. Types * Mechanical transducers convert physical quantities into mechanical outputs or vice versa; * Electrical transducers convert physical quantities into electrical outputs or signals. Examples of these are: ** a thermocouple that changes temperature differences into a small voltage; ** a linear variable differential transformer (LVDT), used to measure displacement (position) changes by means of electrical signals. Sensors, actuators and transceivers Transducers can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peanuts
''Peanuts'' (briefly subtitled ''featuring Good ol' Charlie Brown'') is a print syndication, syndicated daily strip, daily and Sunday strip, Sunday American comic strip written and illustrated by Charles M. Schulz. The strip's original run extended from 1950 to 2000, continuing in reruns afterward. ''Peanuts'' is among the most popular and influential in the history of comic strips, with 17,897 strips published in all, making it "arguably the longest story ever told by one human being". At the time of Schulz's death in 2000, ''Peanuts'' ran in over 2,600 newspapers, with a readership of roughly 355 million across 75 countries, and had been translated into 21 languages. It helped to cement the Yonkoma, four-panel gag strip as the standard in the United States, and together with its merchandise earned Schulz more than $1 billion. Following successful TV and theatrical adaptations over the years, a The Peanuts Movie, movie adaptation was released by Blue Sky Studios in 20 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charlie Brown
Charles "Charlie" Brown is the Protagonist, principal character of the comic strip ''Peanuts'', syndicated in daily newspaper, daily and Sunday newspapers in numerous countries all over the world. Depicted as a "lovable loser", Charlie Brown is one of the great American archetypes and a popular and widely recognized cartoon character. Charlie Brown is characterized as a person who frequently suffers, and as a result, is usually nervous and lacks self-confidence. He shows both Pessimism, pessimistic and Optimism, optimistic attitudes: on some days, he is apprehensive to even get out of bed because he is unable to face the world, but on others, he hopes to accomplish things and is determined to do his best. Charlie Brown is easily recognized by his round head and Trademark look, trademark zigzag patterned shirt. His catchphrase is "Good Grief!" The character's creator, Charles M. Schulz, said that Charlie Brown "has to be the one who suffers, because he is a caricature of the av ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Root Mean Square
In mathematics, the root mean square (abbrev. RMS, or rms) of a set of values is the square root of the set's mean square. Given a set x_i, its RMS is denoted as either x_\mathrm or \mathrm_x. The RMS is also known as the quadratic mean (denoted M_2), a special case of the generalized mean. The RMS of a continuous function is denoted f_\mathrm and can be defined in terms of an integral of the square of the function. In estimation theory, the root-mean-square deviation of an estimator measures how far the estimator strays from the data. Definition The RMS value of a set of values (or a continuous-time waveform) is the square root of the arithmetic mean of the squares of the values, or the square of the function that defines the continuous waveform. In the case of a set of ''n'' values \, the RMS is : x_\text = \sqrt. The corresponding formula for a continuous function (or waveform) ''f''(''t'') defined over the interval T_1 \le t \le T_2 is : f_\text = \sqrt , and the R ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logarithm
In mathematics, the logarithm of a number is the exponent by which another fixed value, the base, must be raised to produce that number. For example, the logarithm of to base is , because is to the rd power: . More generally, if , then is the logarithm of to base , written , so . As a single-variable function, the logarithm to base is the inverse of exponentiation with base . The logarithm base is called the ''decimal'' or ''common'' logarithm and is commonly used in science and engineering. The ''natural'' logarithm has the number as its base; its use is widespread in mathematics and physics because of its very simple derivative. The ''binary'' logarithm uses base and is widely used in computer science, information theory, music theory, and photography. When the base is unambiguous from the context or irrelevant it is often omitted, and the logarithm is written . Logarithms were introduced by John Napier in 1614 as a means of simplifying calculation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa). Mathematical definition A sound wave in a transmission medium causes a deviation (sound pressure, a ''dynamic'' pressure) in the local ambient pressure, a ''static'' pressure. Sound pressure, denoted ''p'', is defined by p_\text = p_\text + p, where * ''p''total is the total pressure, * ''p''stat is the static pressure. Sound measurements Sound intensity In a sound wave, the complementary variable to sound pressure is the particle velocity. Together, they determine the sound intensity of the wave. ''Sound intensity'', denoted I and measured in W· m−2 in SI units, is defined by \mathbf I = p \mathbf v, where * ''p'' is the sound pressure, * v is the particle velocity. Acous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
